Energy Technology Data Exchange (ETDEWEB)
Blink, J.A.
1985-03-01
In this manual we describe the use of the FORIG computer code to solve isotope-generation and depletion problems in fusion and fission reactors. FORIG runs on a Cray-1 computer and accepts more extensive activation cross sections than ORIGEN2 from which it was adapted. This report is an updated and a combined version of the previous ORIGEN2 and FORIG manuals. 7 refs., 15 figs., 13 tabs.
Study on fission blanket fuel cycling of a fusion-fission hybrid energy generation system
Zhou, Z.; Yang, Y.; Xu, H.
2011-10-01
This paper presents a preliminary study on neutron physics characteristics of a light water cooled fission blanket for a new type subcritical fusion-fission hybrid reactor aiming at electric power generation with low technical limits of fission fuel. The major objective is to study the fission fuel cycling performance in the blanket, which may possess significant impacts on the feasibility of the new concept of fusion-fission hybrid reactor with a high energy gain (M) and tritium breeding ratio (TBR). The COUPLE2 code developed by the Institute of Nuclear and New Energy Technology of Tsinghua University is employed to simulate the neutronic behaviour in the blanket. COUPLE2 combines the particle transport code MCNPX with the fuel depletion code ORIGEN2. The code calculation results show that soft neutron spectrum can yield M > 20 while maintaining TBR >1.15 and the conversion ratio of fissile materials CR > 1 in a reasonably long refuelling cycle (>five years). The preliminary results also indicate that it is rather promising to design a high-performance light water cooled fission blanket of fusion-fission hybrid reactor for electric power generation by directly loading natural or depleted uranium if an ITER-scale tokamak fusion neutron source is achievable.
Research on stellarator-mirror fission-fusion hybrid
Moiseenko, V. E.; Kotenko, V. G.; Chernitskiy, S. V.; Nemov, V. V.; Ågren, O.; Noack, K.; Kalyuzhnyi, V. N.; Hagnestål, A.; Källne, J.; Voitsenya, V. S.; Garkusha, I. E.
2014-09-01
The development of a stellarator-mirror fission-fusion hybrid concept is reviewed. The hybrid comprises of a fusion neutron source and a powerful sub-critical fast fission reactor core. The aim is the transmutation of spent nuclear fuel and safe fission energy production. In its fusion part, neutrons are generated in deuterium-tritium (D-T) plasma, confined magnetically in a stellarator-type system with an embedded magnetic mirror. Based on kinetic calculations, the energy balance for such a system is analyzed. Neutron calculations have been performed with the MCNPX code, and the principal design of the reactor part is developed. Neutron outflux at different outer parts of the reactor is calculated. Numerical simulations have been performed on the structure of a magnetic field in a model of the stellarator-mirror device, and that is achieved by switching off one or two coils of toroidal field in the Uragan-2M torsatron. The calculations predict the existence of closed magnetic surfaces under certain conditions. The confinement of fast particles in such a magnetic trap is analyzed.
Fission Thrust sail as booster for high {\\Delta}v fusion based propulsion
Ceyssens, Frederik; Driesen, Maarten
2014-01-01
The fission thrust sail as booster for nuclear fusion-based rocket propulsion for future starships is studied. Some required aspects of these systems such as neutron moderation and sail regeneration are discussed. First order calculations are used together with Monte Carlo simulations to assess system performance. When the fusion rocket has relatively low efficiency (~30%) in converting fusion fuel to a directed exhaust, adding a fission sail is shown to be beneficial for obtainable delta-v. Also, this type of fission-fusion hybrid interstellar propulsion has the potential to improve acceleration. Other advantages are discussed as well.
Axisymmetric Magnetic Mirror Fusion-Fission Hybrid
Energy Technology Data Exchange (ETDEWEB)
Moir, R. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Martovetsky, N. N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Molvik, A. W. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ryutov, D. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Simonen, T. C. [Univ. of California, Berkeley, CA (United States)
2011-05-13
The achieved performance of the gas dynamic trap version of magnetic mirrors and today’s technology we believe are sufficient with modest further efforts for a neutron source for material testing (Q=P_{fusion}/P_{input}~0.1). The performance needed for commercial power production requires considerable further advances to achieve the necessary high Q>>10. An early application of the mirror, requiring intermediate performance and intermediate values of Q~1 are the hybrid applications. The Axisymmetric Mirror has a number of attractive features as a driver for a fusion-fission hybrid system: geometrical simplicity, inherently steady-state operation, and the presence of the natural divertors in the form of end tanks. This level of physics performance has the virtue of low risk and only modest R&D needed and its simplicity promises economy advantages. Operation at Q~1 allows for relatively low electron temperatures, in the range of 4 keV, for the DT injection energy ~ 80 keV. A simple mirror with the plasma diameter of 1 m and mirror-to-mirror length of 35 m is discussed. Simple circular superconducting coils are based on today’s technology. The positive ion neutral beams are similar to existing units but designed for steady state. A brief qualitative discussion of three groups of physics issues is presented: axial heat loss, MHD stability in the axisymmetric geometry, microstability of sloshing ions. Burning fission reactor wastes by fissioning actinides (transuranics: Pu, Np, Am, Cm, .. or just minor actinides: Np, Am, Cm, …) in the hybrid will multiply fusion’s energy by a factor of ~10 or more and diminish the Q needed to less than 1 to overcome the cost of recirculating power for good economics. The economic value of destroying actinides by fissioning is rather low based on either the cost of long-term storage or even deep geologic disposal so most of the revenues of hybrids will come from electrical power. Hybrids that obtain revenues from
Directory of Open Access Journals (Sweden)
Thakur Meenu
2015-01-01
Full Text Available The reaction mechanism of 19F + 232Th and 28Si + 232Th systems populating the near-super-heavy compound nuclei 251Es and 260Rf respectively are investigated using neutron multiplicity as a probe. The prescission neutron multiplicities of these compound nuclei are calculated at different excitation energies using a statistical model code. These calculations are performed using the Bohr-Wheeler transition state fission width as well as the dissipative dynamical fission width based on the Kramers’ prescription. For 19F + 232Th system, the measured yield of pre-scission is compared with the statistical model calculations for the decay of a compound nucleus in the excitation energy range of 54-90 MeV. The comparison between the measured and the calculated values indicates that the Bohr-Wheeler fission width underestimates the pre-scission neutron yield and a large amount of dissipation strength is required to reproduce the experimental pre-scission neutron multiplicities. The excitation energy dependence of the fitted values of the dissipation coefficient is also discussed. In addition, exploratory statistical model calculations of pre-scission neutron multiplicity for the 28Si + 232Th system are presented in the above range of excitation energy.
Fusion and fission of atomic clusters: recent advances
DEFF Research Database (Denmark)
Obolensky, Oleg I.; Solov'yov, Ilia; Solov'yov, Andrey V.
2005-01-01
We review recent advances made by our group in finding optimized geometries of atomic clusters as well as in description of fission of charged small metal clusters. We base our approach to these problems on analysis of multidimensional potential energy surface. For the fusion process we have...... developed an effective scheme of adding new atoms to stable cluster geometries of larger clusters in an efficient way. We apply this algorithm to finding geometries of metal and noble gas clusters. For the fission process the analysis of the potential energy landscape calculated on the ab initio level...... of theory allowed us to obtain very detailed information on energetics and pathways of the different fission channels for the Na^2+_10 clusters....
Angular anisotropy of the fusion-fission and quasifission fragments
Nasirov, A K; Utamuratov, R K; Fazio, G; Giardina, G; Hanappe, F; Mandaglio, G; Manganaro, M; Scheid, W
2007-01-01
The anisotropy in the angular distribution of the fusion-fission and quasifission fragments for the $^{16}$O+$^{238}$U, $^{19}$F+$^{208}$Pb and $^{32}$S+$^{208}$Pb reactions is studied by analyzing the angular momentum distributions of the dinuclear system and compound nucleus which are formed after capture and complete fusion, respectively. The orientation angles of axial symmetry axes of colliding nuclei to the beam direction are taken into account for the calculation of the variance of the projection of the total spin onto the fission axis. It is shown that the deviation of the experimental angular anisotropy from the statistical model picture is connected with the contribution of the quasifission fragments which is dominant in the $^{32}$S+$^{208}$Pb reaction. Enhancement of anisotropy at low energies in the $^{16}$O+$^{238}$U reaction is connected with quasifission of the dinuclear system having low temperature and effective moment of inertia.
SABR Fusion-Fission Hybrid Studies
Stewart, Chris
2012-03-01
The Subcritical Advanced Burner Reactor (SABR) concept is a fast reactor comprised of a tokamak fusion neutron source based on ITER surrounded by an annular fission core adapted from Integral Fast Reactor designs. Previous work has examined SABR used to help close the nuclear fuel cycle by fissioning the transuranics from spent nuclear fuel. One focus of the present work is a SABR Breeder Reactor to achieve tritium self-sufficieny and a Pu breeding ratio significantly above 1 in order to provide fuel for SABR as well as for MOX-fueled LWR's and other fast reactors. Another focus of this research is the dynamic safety simulation of lloss-of-flow loss-of-heat-sink, loss-of-power, and positive reactivity accidents in the TRU fuel SABR burner reactor. The reactivity effect of thermal-induced bowing of fuel pins has been modeled, which is expected to provide passive safety.
Fusion-fission energy systems evaluation
Energy Technology Data Exchange (ETDEWEB)
Teofilo, V.L.; Aase, D.T.; Bickford, W.E.
1980-01-01
This report serves as the basis for comparing the fusion-fission (hybrid) energy system concept with other advanced technology fissile fuel breeding concepts evaluated in the Nonproliferation Alternative Systems Assessment Program (NASAP). As such, much of the information and data provided herein is in a form that meets the NASAP data requirements. Since the hybrid concept has not been studied as extensively as many of the other fission concepts being examined in NASAP, the provided data and information are sparse relative to these more developed concepts. Nevertheless, this report is intended to provide a perspective on hybrids and to summarize the findings of the rather limited analyses made to date on this concept.
Ceramics in fission and fusion technology
Energy Technology Data Exchange (ETDEWEB)
Olander, D.R.
1986-04-01
The role of ceramic components in fission and fusion reactors is described. Almost all of the functions normally performed by ceramics, except mechanical, are required of nuclear ceramics. The oxides of uranium and plutonium are of predominant importance in nuclear applications, but a number of other ceramics play peripheral roles. The unique service conditions under which nuclear ceramics must operate include intense radiation fields, high temperatures and large temperature gradients, and aggressive chemical environments. Examples of laboratory research designed to broaden understanding of the behavior of uranium dioxide in such conditions are given. The programs described include high temperature vaporization, diffusional processes, and interaction with hydrogen.
Excitation Functions of Fusion and Fission for 32S+170Er at Energies Near and Below Coulomb Barrier
Institute of Scientific and Technical Information of China (English)
BAO; Peng-fei; LIN; Cheng-jian; YANG; Feng; JIA; Hui-ming; XU; Xin-xing; YANG; Lei; SUN; Li-jie; MA; Nan-ru; ZHANG; Huan-qiao; LIU; Zu-hua
2013-01-01
Excitation functions of fusion evaporation residue(ER)and fission for 32S+170Er system at near barrier energy region were measured,respectively.With the comparison to the calculations of coupledchannels effects,it is accessible to investigate the impacts on the fusion and fission processes of target deformation and the dependence on the entrance-channel.The experiment was performed at Beijing HI-13 Tandem Accelerator.Fission and fusion evaporation
A revised calculational model for fission
Energy Technology Data Exchange (ETDEWEB)
Atchison, F.
1998-09-01
A semi-empirical parametrization has been developed to calculate the fission contribution to evaporative de-excitation of nuclei with a very wide range of charge, mass and excitation-energy and also the nuclear states of the scission products. The calculational model reproduces measured values (cross-sections, mass distributions, etc.) for a wide range of fissioning systems: Nuclei from Ta to Cf, interactions involving nucleons up to medium energy and light ions. (author)
Fusion-fission study at IUAC: Recent results
Pullanhiotan, Sugathan
2016-10-01
Several properties observed in heavy ion induced fission led to the conclusion that fission is not always originated from fully equilibrated compound nucleus. Soon after the collision of two nuclei, it forms a di-nuclear system than can fission before a compound nucleus is formed. This process termed quasi-fission is a major hurdle to the formation of heavier elements by fusion. Fission originated before complete equilibration showed anomalously large angular anisotropy and mass distribution wider than what is expected from compound nucleus fission. The standard statistical model fails to predict the outcome of quasi-fission and currently no dynamical model is fully developed to predict all the features of quasi-fission. Though much progress has been made in recent times, a full understanding of the fission dynamics is still missing. Experiments identifying the influence of entrance channel parameters on dynamics of fusion-fission showed contrasting results. At IUAC accelerator facility many experiments have been performed to make a systematic study of fission dynamics using mass distribution, angular distribution and neutron multiplicity measurements in mass region around A ∼ 200. Recent measurement on mass distribution of fission fragment from reaction 19 F +206,208 Pb around fusion barrier energy showed the influence of multi-mode fission in enhancing the mass variance at low excitation energy. In this talk I will present some of these results.
Fission Fusion Hybrids: a nearer term application of Fusion
Kotschenreuther, M.; Valanju, P.; Mahajan, S.; Covele, B.
2011-10-01
Fission-fusion hybrids enjoy unique advantages for addressing long standing societal acceptability issues of nuclear fission power at a much lower level of technical development than a competitive fusion power plant. For waste incineration, hybrids burn intransigent transuranic residues (with the long lived biohazard) from light water reactors (LWRs). The number of hybrids needed is 5-10 times less than the corresponding number of fast reactors (FRs). The highly sub-critical hybrids, with a thermal/epithermal spectrum, incinerate > 95% of the waste in decades rather than the centuries needed for FRs. For fuel production, hybrids can produce fuel for 3-4 times as many LWRs with no fuel reprocessing. Thorium fuel rods exposed to neutrons in the hybrid reach fissile concentrations that enable efficient burning in LWR without the proliferation risks of reprocessing. The proliferation risks of this method are far less than other fuel breeding approaches, including today's gas centrifuge. With this cycle, US Thorium reserves could supply the entire US electricity supply for centuries. The centerpiece of the fuel cycle is a high power density Compact Fusion Neutron Source (major+minor radius ~ 2.5-3.5 m), which is made feasible by the super-X divertor.
Structural materials for fission & fusion energy
Directory of Open Access Journals (Sweden)
Steven J. Zinkle
2009-11-01
Full Text Available Structural materials represent the key for containment of nuclear fuel and fission products as well as reliable and thermodynamically efficient production of electrical energy from nuclear reactors. Similarly, high-performance structural materials will be critical for the future success of proposed fusion energy reactors, which will subject the structures to unprecedented fluxes of high-energy neutrons along with intense thermomechanical stresses. Advanced materials can enable improved reactor performance via increased safety margins and design flexibility, in particular by providing increased strength, thermal creep resistance and superior corrosion and neutron radiation damage resistance. In many cases, a key strategy for designing high-performance radiation-resistant materials is based on the introduction of a high, uniform density of nanoscale particles that simultaneously provide good high temperature strength and neutron radiation damage resistance.
Energy Technology Data Exchange (ETDEWEB)
Kramer, Kevin James [Univ. of California, Berkeley, CA (United States)
2010-04-08
This study investigates the neutronics design aspects of a hybrid fusion-fission energy system called the Laser Fusion-Fission Hybrid (LFFH). A LFFH combines current Laser Inertial Confinement fusion technology with that of advanced fission reactor technology to produce a system that eliminates many of the negative aspects of pure fusion or pure fission systems. When examining the LFFH energy mission, a significant portion of the United States and world energy production could be supplied by LFFH plants. The LFFH engine described utilizes a central fusion chamber surrounded by multiple layers of multiplying and moderating media. These layers, or blankets, include coolant plenums, a beryllium (Be) multiplier layer, a fertile fission blanket and a graphite-pebble reflector. Each layer is separated by perforated oxide dispersion strengthened (ODS) ferritic steel walls. The central fusion chamber is surrounded by an ODS ferritic steel first wall. The first wall is coated with 250-500 μm of tungsten to mitigate x-ray damage. The first wall is cooled by Li_{17}Pb_{83 } eutectic, chosen for its neutron multiplication and good heat transfer properties. The Li_{17}Pb_{83} flows in a jacket around the first wall to an extraction plenum. The main coolant injection plenum is immediately behind the Li_{17}Pb_{83}, separated from the Li_{17}Pb_{83} by a solid ODS wall. This main system coolant is the molten salt flibe (2LiF-BeF_{2}), chosen for beneficial neutronics and heat transfer properties. The use of flibe enables both fusion fuel production (tritium) and neutron moderation and multiplication for the fission blanket. A Be pebble (1 cm diameter) multiplier layer surrounds the coolant injection plenum and the coolant flows radially through perforated walls across the bed. Outside the Be layer, a fission fuel layer comprised of depleted uranium contained in Tristructural-isotropic (TRISO) fuel particles
Microscopic Calculations of 240Pu Fission
Energy Technology Data Exchange (ETDEWEB)
Younes, W; Gogny, D
2007-09-11
Hartree-Fock-Bogoliubov calculations have been performed with the Gogny finite-range effective interaction for {sup 240}Pu out to scission, using a new code developed at LLNL. A first set of calculations was performed with constrained quadrupole moment along the path of most probable fission, assuming axial symmetry but allowing for the spontaneous breaking of reflection symmetry of the nucleus. At a quadrupole moment of 345 b, the nucleus was found to spontaneously scission into two fragments. A second set of calculations, with all nuclear moments up to hexadecapole constrained, was performed to approach the scission configuration in a controlled manner. Calculated energies, moments, and representative plots of the total nuclear density are shown. The present calculations serve as a proof-of-principle, a blueprint, and starting-point solutions for a planned series of more comprehensive calculations to map out a large set of scission configurations, and the associated fission-fragment properties.
Pulsed Fission-Fusion (PuFF) Propulsion System Project
National Aeronautics and Space Administration — Fission-ignited fusion systems have been operational – in weapon form – since the 1950’s. Leveraging insights gained from the weapons physics...
Dynamics of morphological changes for mitochondrial fission and fusion
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Mitochondria experience continuous fusion and fission in a living cell, but their dynamics remains poorly quantified. Here a theoretical model was developed, upon a simplified population balance equation (PBE), to predict the morphological changes induced by mitochondrial fission and fusion. Assuming that both fission and fusion events are statistically independent, the survival probability of mitochondria staying in the fission or fusion state was formulated as an exponentially-decayed function with time, which depended on the time-dependent distribution of the mitochondrial volume and the fission and fusion rates. Parametric analysis was done for two typical volume distributions. One was Gamma distribution and the other was Gaussian distribution, derived from the measurements of volume distribution for individual mitochondria in a living cell and purified mitochondria in vitro. The predictions indicated that the survival probability strongly depended on morphological changes of individual mitochondria and was inversely correlated to the fission and fusion rates. This work provided a new insight into quantifying the mitochondrial dynamics via monitoring the evolution of the mitochondrial volume.
Fission and fusion scenarios for magnetic microswimmer clusters
Guzmán-Lastra, Francisca; Löwen, Hartmut
2016-01-01
Fission and fusion processes of particles clusters occur in many areas of physics and chemistry from subnuclear to astronomic length scales. Here we study fission and fusion of magnetic microswimmer clusters as governed by their hydrodynamic and dipolar interactions. Rich scenarios are found which depend crucially on whether the swimmer is a pusher or a puller. In particular a linear magnetic chain of pullers is stable while a pusher chain shows a cascade of fission (or disassembly) processes as the self-propulsion velocity is increased. Contrarily, magnetic ring clusters show fission for any type of swimmer. Moreover, we find a plethora of possible fusion (or assembly) scenarios if a single swimmer collides with a ringlike cluster and two rings spontaneously collide. Our predictions are obtained by computer simulations and verifiable in experiments on active colloidal Janus particles and magnetotactic bacteria.
Fission-suppressed hybrid reactor: the fusion breeder
Energy Technology Data Exchange (ETDEWEB)
Moir, R.W.; Lee, J.D.; Coops, M.S.
1982-12-01
Results of a conceptual design study of a /sup 233/U-producing fusion breeder are presented. The majority of the study was devoted to conceptual design and evaluation of a fission-suppressed blanket and to fuel cycle issues such as fuel reprocessing, fuel handling, and fuel management. Studies in the areas of fusion engineering, reactor safety, and economics were also performed.
Isotopic fission fragment distributions as a deep probe to fusion-fission dynamics
Farget, F; Delaune, O; Tarasov, O B; Derkx, X; Schmidt, K -H; Amthor, A M; Audouin, L; Bacri, C -O; Barreau, G; Bastin, B; Bazin, D; Blank, B; Benlliure, J; Caceres, L; Casarejos, E; Chibihi, A; Fernandez-Dominguez, B; Gaudefroy, L; Golabek, C; Grevy, S; Jurado, B; Kamalou, O; Lemasson, A; Lukyanov, S; Mittig, W; Morrissey, D J; Navin, A; Pereira, J; Perrot, L; Rejmund, M; Roger, T; Saint-Laurent, M -G; Savajols, H; Schmitt, C; Sherill, B M; Stodel, C; Taieb, J; Thomas, J -C; Villari, A C
2012-01-01
During the fission process, the nucleus deforms and elongates up to the two fragments inception and their final separation at scission deformation. The evolution of the nucleus energy with deformation is determined by the macroscopic properties of the nucleus, and is also strongly influenced by the single-particle structure of the nucleus. The fission fragment distribution is a direct consequence of the deformation path the nucleus has encountered, and therefore is the most genuine experimental observation of the potential energy landscape of the deforming nucleus. Very asymmetric fusion-fission reactions at energy close to the Coulomb barrier, produce well-defined conditions of the compound nucleus formation, where processes such as quasi-fission, pre-equilibrium emission and incomplete fusion are negligible. In the same time, the excitation energy is sufficient to reduce significantly structural effects, and mostly the macroscopic part of the potential is responsible for the formation of the fission fragmen...
Energy Technology Data Exchange (ETDEWEB)
Kramer, Kevin James [Univ. of California, Berkeley, CA (United States)
2010-04-08
This study investigates the neutronics design aspects of a hybrid fusion-fission energy system called the Laser Fusion-Fission Hybrid (LFFH). A LFFH combines current Laser Inertial Confinement fusion technology with that of advanced fission reactor technology to produce a system that eliminates many of the negative aspects of pure fusion or pure fission systems. When examining the LFFH energy mission, a significant portion of the United States and world energy production could be supplied by LFFH plants. The LFFH engine described utilizes a central fusion chamber surrounded by multiple layers of multiplying and moderating media. These layers, or blankets, include coolant plenums, a beryllium (Be) multiplier layer, a fertile fission blanket and a graphite-pebble reflector. Each layer is separated by perforated oxide dispersion strengthened (ODS) ferritic steel walls. The central fusion chamber is surrounded by an ODS ferritic steel first wall. The first wall is coated with 250-500 μm of tungsten to mitigate x-ray damage. The first wall is cooled by Li_{17}Pb_{83 } eutectic, chosen for its neutron multiplication and good heat transfer properties. The Li_{17}Pb_{83} flows in a jacket around the first wall to an extraction plenum. The main coolant injection plenum is immediately behind the Li_{17}Pb_{83}, separated from the Li_{17}Pb_{83} by a solid ODS wall. This main system coolant is the molten salt flibe (2LiF-BeF_{2}), chosen for beneficial neutronics and heat transfer properties. The use of flibe enables both fusion fuel production (tritium) and neutron moderation and multiplication for the fission blanket. A Be pebble (1 cm diameter) multiplier layer surrounds the coolant injection plenum and the coolant flows radially through perforated walls across the bed. Outside the Be layer, a fission fuel layer comprised of depleted uranium contained in Tristructural-isotropic (TRISO) fuel particles
Kramer, Kevin James
2010-01-01
This study investigates the neutronics design aspects of a hybrid fusion-fission energy system called the Laser Fusion-Fission Hybrid (LFFH). A LFFH combines current Laser Inertial Confinement fusion technology with that of advanced fission reactor technology to produce a system that eliminates many of the negative aspects of pure fusion or pure fission systems. When examining the LFFH energy mission, a significant portion of the United States and world energy production could be supplied by ...
Principles of the mitochondrial fusion and fission cycle in neurons.
Cagalinec, Michal; Safiulina, Dzhamilja; Liiv, Mailis; Liiv, Joanna; Choubey, Vinay; Wareski, Przemyslaw; Veksler, Vladimir; Kaasik, Allen
2013-05-15
Mitochondrial fusion-fission dynamics play a crucial role in many important cell processes. These dynamics control mitochondrial morphology, which in turn influences several important mitochondrial properties including mitochondrial bioenergetics and quality control, and they appear to be affected in several neurodegenerative diseases. However, an integrated and quantitative understanding of how fusion-fission dynamics control mitochondrial morphology has not yet been described. Here, we took advantage of modern visualisation techniques to provide a clear explanation of how fusion and fission correlate with mitochondrial length and motility in neurons. Our main findings demonstrate that: (1) the probability of a single mitochondrion splitting is determined by its length; (2) the probability of a single mitochondrion fusing is determined primarily by its motility; (3) the fusion and fission cycle is driven by changes in mitochondrial length and deviations from this cycle serves as a corrective mechanism to avoid extreme mitochondrial length; (4) impaired mitochondrial motility in neurons overexpressing 120Q Htt or Tau suppresses mitochondrial fusion and leads to mitochondrial shortening whereas stimulation of mitochondrial motility by overexpressing Miro-1 restores mitochondrial fusion rates and sizes. Taken together, our results provide a novel insight into the complex crosstalk between different processes involved in mitochondrial dynamics. This knowledge will increase understanding of the dynamic mitochondrial functions in cells and in particular, the pathogenesis of mitochondrial-related neurodegenerative diseases.
Fission Product Decay Heat Calculations for Neutron Fission of 232Th
Son, P. N.; Hai, N. X.
2016-06-01
Precise information on the decay heat from fission products following times after a fission reaction is necessary for safety designs and operations of nuclear-power reactors, fuel storage, transport flasks, and for spent fuel management and processing. In this study, the timing distributions of fission products' concentrations and their integrated decay heat as function of time following a fast neutron fission reaction of 232Th were exactly calculated by the numerical method with using the DHP code.
Tunneling process in heavy-ion fusion and fission
Energy Technology Data Exchange (ETDEWEB)
Iwamoto, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Kondratyev, V.; Bonasera, A.
1998-10-01
We present a model towards the many-body description of sub-barrier fusion and spontaneous fission based on the semiclassical Vlasov equation and the Feynman path integral method. We define suitable collective variables from the Vlasov solution and use the imaginary time technique for the dynamics below the Coulomb barrier. (author)
Proceedings of the Second Fusion-Fission Energy Systems Review Meeting
Energy Technology Data Exchange (ETDEWEB)
None
1977-11-02
The agenda of the meeting was developed to address, in turn, the following major areas: specific problem areas in nuclear energy systems for application of fusion-fission concepts; current and proposed fusion-fission programs in response to the identified problem areas; target costs and projected benefits associated with fusion-fission energy systems; and technical problems associated with the development of fusion-fission concepts. The greatest emphasis was placed on the characteristics of and problems, associated with fuel producing fusion-fission hybrid reactors.
1D Burnup Calculation of Fusion-Fission Hybrid Energy Reactor%聚变-裂变混合能源堆一维计算模型燃耗分析
Institute of Scientific and Technical Information of China (English)
李茂生; 师学明; 伊炜伟
2012-01-01
Fusion-fission hybrid energy reactor is driven by Tokamak fusion source for energy production. Its subcritical zone uses the natural uranium as fuel and water as coolant. The neutron multiplication constant keff, energy multiplication factor M and tritium breeding ratio TBR of the ID hybrid energy reactor model were calculated by transport burnup code MCORGS. The neutron spectrum and nuclear density changing as a function of time show the characteristics of the hybrid energy reactors, which differs from the hybrid reactor for breed nuclear fuel and for spent fuel transmutation. The definition and results may be a reference to the other conceptual analysis.%聚变-裂变混合能源堆包括聚变中子源和以天然铀为燃料、水为冷却剂的次临界包层,主要目标是生产电力.利用输运燃耗耦合程序系统MCORGS计算了混合能源堆一维模型的燃耗,给出了中子有效增殖因数keff、能量放大倍数M、氚增殖比TBR等物理量随时间的变化.通过分析能谱和重要核素随燃耗时间的变化,说明混合能源堆与核燃料增殖、核废料嬗变混合堆的不同特点.本文给出的结果可作为混合堆中子输运、燃耗分析程序校验的参考数据,为混合堆概念研究提供了基础数据.
Systems study of tokamak fusion--fission reactors
Energy Technology Data Exchange (ETDEWEB)
Tenney, F.H.; Bathke, C.G.; Price, W.G. Jr.; Bohlke, W.H.; Mills, R.G.; Johnson, E.F.; Todd, A.M.M.; Buchanan, C.H.; Gralnick, S.L.
1978-11-01
This publication reports the results of a two to three year effort at a systematic analysis of a wide variety of tokamak-driven fissioning blanket reactors, i.e., fusion--fission hybrids. It addresses the quantitative problems of determining the economically most desirable mix of the two products: electric power and fissionable fuel and shows how the price of electric power can be minimized when subject to a variety of constraints. An attempt has been made to avoid restricting assumptions, and the result is an optimizing algorithm that operates in a six-dimensional parameter space. Comparisons are made on sets of as many as 100,000 distinct machine models, and the principal results of the study have been derived from the examination of several hundred thousand possible reactor configurations.
Measurement of tritium production rate distribution for a fusion-fission hybrid conceptual reactor
Institute of Scientific and Technical Information of China (English)
WANG Xin-Hua; GUO Hai-Ping; MOU Yun-Feng; ZHENG Pu; LIU Rong; YANG Xiao-Fei; YANG Jian
2013-01-01
A fusion-fission hybrid conceptual reactor is established.It consists of a DT neutron source and a spherical shell of depleted uranium and hydrogen lithium.The tritium production rate (TPR) distribution in the conceptual reactor was measured by DT neutrons using two sets of lithium glass detectors with different thicknesses in the hole in the vertical direction with respect to the D+ beam of the Cockcroft-Walton neutron generator in direct current mode.The measured TPR distribution is compared with the calculated results obtained by the threedimensional Monte Carlo code MCNP5 and the ENDF/B-Ⅵ data file.The discrepancy between the measured and calculated values can be attributed to the neutron data library of the hydrogen lithium lack S(α,β) thermal scattering model,so we show that a special database of low-energy and thermal neutrons should be established in the physics design of fusion-fission hybrid reactors.
Fusion-Fission Hybrid for Fissile Fuel Production without Processing
Energy Technology Data Exchange (ETDEWEB)
Fratoni, M; Moir, R W; Kramer, K J; Latkowski, J F; Meier, W R; Powers, J J
2012-01-02
Two scenarios are typically envisioned for thorium fuel cycles: 'open' cycles based on irradiation of {sup 232}Th and fission of {sup 233}U in situ without reprocessing or 'closed' cycles based on irradiation of {sup 232}Th followed by reprocessing, and recycling of {sup 233}U either in situ or in critical fission reactors. This study evaluates a third option based on the possibility of breeding fissile material in a fusion-fission hybrid reactor and burning the same fuel in a critical reactor without any reprocessing or reconditioning. This fuel cycle requires the hybrid and the critical reactor to use the same fuel form. TRISO particles embedded in carbon pebbles were selected as the preferred form of fuel and an inertial laser fusion system featuring a subcritical blanket was combined with critical pebble bed reactors, either gas-cooled or liquid-salt-cooled. The hybrid reactor was modeled based on the earlier, hybrid version of the LLNL Laser Inertial Fusion Energy (LIFE1) system, whereas the critical reactors were modeled according to the Pebble Bed Modular Reactor (PBMR) and the Pebble Bed Advanced High Temperature Reactor (PB-AHTR) design. An extensive neutronic analysis was carried out for both the hybrid and the fission reactors in order to track the fuel composition at each stage of the fuel cycle and ultimately determine the plant support ratio, which has been defined as the ratio between the thermal power generated in fission reactors and the fusion power required to breed the fissile fuel burnt in these fission reactors. It was found that the maximum attainable plant support ratio for a thorium fuel cycle that employs neither enrichment nor reprocessing is about 2. This requires tuning the neutron energy towards high energy for breeding and towards thermal energy for burning. A high fuel loading in the pebbles allows a faster spectrum in the hybrid blanket; mixing dummy carbon pebbles with fuel pebbles enables a softer spectrum in
Pink1 regulates mitochondrial dynamics through interaction with the fission/fusion machinery
Yang, Yufeng; Ouyang, Yingshi; Yang, Lichuan; Beal, M. Flint; McQuibban, Angus; Vogel, Hannes; Lu, Bingwei
2008-01-01
Mitochondria form dynamic tubular networks that undergo frequent morphological changes through fission and fusion, the imbalance of which can affect cell survival in general and impact synaptic transmission and plasticity in neurons in particular. Some core components of the mitochondrial fission/fusion machinery, including the dynamin-like GTPases Drp1, Mitofusin, Opa1, and the Drp1-interacting protein Fis1, have been identified. How the fission and fusion processes are regulated under norma...
Role of mitochondrial lipids in guiding fission and fusion.
Frohman, Michael A
2015-03-01
Clinically important links have been established between mitochondrial function and cardiac physiology and disease in the context of signaling mechanisms, energy production, and muscle cell development. The proteins and processes that drive mitochondrial fusion and fission are now known to have emergent functions in intracellular calcium homeostasis, apoptosis, vascular smooth muscle cell proliferation, myofibril organization, and Notch-driven cell differentiation, all key issues in cardiac disease. Moreover, decreasing fission may confer protection against ischemic heart disease, particularly in the setting of obesity, diabetes, and heart failure. The importance of lipids in controlling mitochondrial fission and fusion is increasingly becoming appreciated. Roles for the bulk and signaling lipids cardiolipin, phosphatidylethanolamine, phosphatidic acid, diacylglycerol, and lysophosphatidic acid and the enzymes that synthesize or metabolize them in the control of mitochondrial shape and function are reviewed here. A number of diseases have been linked to loss-of-function alleles for a subset of the enzymes, emphasizing the importance of the lipid environment in this context.
Dynamical approach to fusion-fission process in superheavy mass region
Directory of Open Access Journals (Sweden)
Aritomo Y.
2012-10-01
Full Text Available In order to describe heavy-ion fusion reactions around the Coulomb barrier with an actinide target nucleus, we propose a model which combines the coupled-channels approach and a fluctuation-dissipation model for dynamical calculations. This model takes into account couplings to the collective states of the interacting nuclei in the penetration of the Coulomb barrier and the subsequent dynamical evolution of a nuclear shape from the contact configuration. In the fluctuation-dissipation model with a Langevin equation, the effect of nuclear orientation at the initial impact on the prolately deformed target nucleus is considered. Fusion-fission, quasifission and deep quasifission are separated as different Langevin trajectories on the potential energy surface. Using this model, we analyze the experimental data for the mass distribution of fission fragments (MDFF in the reaction of 36S+238U at several incident energies around the Coulomb barrier.
Theory of competition between fusion and quasi-fission in a heavy fusing system
Díaz-Torres, A
2006-01-01
A theory of the competition between fusion and quasi-fission in a heavy fusing system is proposed, which is based on a master equation and the two-center shell model. Fusion and quasi-fission arise from a diffusion process in an ensemble of nuclear shapes evolving towards the thermal equilibrium. The master equation describes the diffusion of the nuclear shapes due to quantum and thermal fluctuations. Other crucial physical effects like dissipation, ground-state shell effects, diabatic effects and rotational effects are also incorporated into the theory. The fusing system moves in a dynamical (time-dependent) collective potential energy surface which is initially diabatic and gradually becomes adiabatic. The microscopic ingredients of the theory are obtained with a realistic two-center shell model based on Woods-Saxon potentials. Numerical calculations for several reactions leading to $^{256}$No are discussed. Among other important conclusions, the results indicate that (i) the diabatic effects play a very im...
Pink1 regulates mitochondrial dynamics through interaction with the fission/fusion machinery.
Yang, Yufeng; Ouyang, Yingshi; Yang, Lichuan; Beal, M Flint; McQuibban, Angus; Vogel, Hannes; Lu, Bingwei
2008-05-13
Mitochondria form dynamic tubular networks that undergo frequent morphological changes through fission and fusion, the imbalance of which can affect cell survival in general and impact synaptic transmission and plasticity in neurons in particular. Some core components of the mitochondrial fission/fusion machinery, including the dynamin-like GTPases Drp1, Mitofusin, Opa1, and the Drp1-interacting protein Fis1, have been identified. How the fission and fusion processes are regulated under normal conditions and the extent to which defects in mitochondrial fission/fusion are involved in various disease conditions are poorly understood. Mitochondrial malfunction tends to cause diseases with brain and skeletal muscle manifestations and has been implicated in neurodegenerative diseases such as Parkinson's disease (PD). Whether abnormal mitochondrial fission or fusion plays a role in PD pathogenesis has not been shown. Here, we show that Pink1, a mitochondria-targeted Ser/Thr kinase linked to familial PD, genetically interacts with the mitochondrial fission/fusion machinery and modulates mitochondrial dynamics. Genetic manipulations that promote mitochondrial fission suppress Drosophila Pink1 mutant phenotypes in indirect flight muscle and dopamine neurons, whereas decreased fission has opposite effects. In Drosophila and mammalian cells, overexpression of Pink1 promotes mitochondrial fission, whereas inhibition of Pink1 leads to excessive fusion. Our genetic interaction results suggest that Fis1 may act in-between Pink1 and Drp1 in controlling mitochondrial fission. These results reveal a cell biological role for Pink1 and establish mitochondrial fission/fusion as a paradigm for PD research. Compounds that modulate mitochondrial fission/fusion could have therapeutic value in PD intervention.
Fusion and fission studies for the system /sup 32/S + /sup 239/U
Energy Technology Data Exchange (ETDEWEB)
Freifelder, R.H.
1985-01-01
The total fusion cross section has been measured at energies from 0.93 to 1.08 times the s-wave interaction barrier for the system /sup 32/S + /sup 238/U. Measurements were made by detecting coincident fission fragments following full momentum transfer in two position sensitive parallel plate avalanche counters. Fission fragment angular distributions were measured from 90/sup 0/ to 166/sup 0/ in the center of mass for all energies except the lowest where the angular range was 127/sup 0/ to 170/sup 0/. The experimental total fusion cross section was first compared to a one dimensional barrier penetration model which severely underpredicted the data. Then the data were compared to the predictions of coupled channels calculations where the first 2/sup +/ and then higher lying states in /sup 238/U were included. The calculations with only the 2/sup +/ state were able to predict the trend in the data quite well. Inclusion of the higher lying states made no appreciable change in the fusion cross section suggesting that for nuclei which may be characterized as highly rotational, coupling to the lowest lying state may be able to reproduce the measured fusion cross section.
Energy Technology Data Exchange (ETDEWEB)
Shaw, H F; Blink, J; Farmer, J; Latkowski, J; Kramer, K
2009-09-08
We are studying the use of a Laser Inertial-confinement Fusion Engine (LIFE) to drive a hybrid fusion-fission system that can generate electrical power and/or burn nuclear waste. The system uses the neutrons from laser driven ICF to produce tritium and to drive nuclear reactions in a subcritical fission blanket. The fusion neutron source obviates the need for a self-sustaining chain reaction in the fission blanket. Either fissile or fertile could be used as fission fuel, thus eliminating the need for isotopic enrichment. The 'driven' system potentially allows very high levels of burnup to be reached, extracting a large fraction of the available energy in the fission fuel without the need for reprocessing. In this note, we discuss the radionuclide inventory of a depleted uranium (DU) fuel burned to greater than 95% FIMA (Fissions per Initial heavy Metal Atom), the implications for thermal management of the resulting waste, and the implications of this waste for meeting the dose standards for releases from a geological repository for high-level waste. The fission waste discussed here would be that produced by a LIFE hybrid with a 500-MW fusion source. The fusion neutrons are multiplied and moderated by a sequence of concentric shells of materials before encountering the fission fuel, and fission in this region is largely due to thermal neutrons. The fission blanket consists of 40 metric tons (MT) of DU, assumed to be in the form of TRISO-like UOC fuel particles embedded in 2-cm-diameter graphite pebbles. (It is recognized that TRISO-based fuel may not reach the high burnup of the fertile fuel considered here, and other fuel options are being investigated. We postulate the existence of a fuel that can reach >95% FIMA so that the waste disposal implications of high burnup can be assessed.) The engine and plant design considered here would receive one load of fission fuel and produce {approx}2 GWt of power (fusion + fission) over its 50- to 70-year lifetime
Fusion and fission studies for the system S-32 + U-238
Freifelder, R. H.
The total fusion cross section was measured at energies from .93 to 1.08 times the s-wave interaction barrier for the system S32 + U238. Measurements were made by detecting coincident fission fragments following full momentum transfer in two position sensitive parallel plate avalanche counters. Fission fragment angular distributions were measured from 90 to 166 degrees in the center of mass for all energies except the lowest where the angular range was 127 to 170 degrees. The experimental total fusion cross section was first compared to a one dimensional barrier penetration model which severely underpredicted the data. Then the data were compared to the predictions of coupled channels calculations where the first 2+ and then higher lying states in U238 were included. The calculations with only the 2+ state were able to predict the trend in the data quite well. The measured angular distribution of fission fragments were compared to the predictions of transition state theory. A model using the scission point as the transition state was discussed and predictions based on this model were presented.
Fission life-time calculation using a complex absorbing potential
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Scamps Guillaume
2016-01-01
Full Text Available A comparison between the semi-classical approximation and the full quantum calculation with a complex absorbing potential is made with a model of the fission of 258Fm. The potential barrier is obtained with the constrained Skyrme HF+BCS theory. The life-time obtained by the two calculations agree with each other the difference being only by 25%.
Fission life-time calculation using a complex absorbing potential
Scamps, Guillaume
2015-01-01
A comparison between the semi-classical approximation and the full quantum calculation with a complex absorbing potential is made with a model of the fission of 258Fm. The potential barrier is obtained with the constrained Skyrme HF+BCS theory. The life-time obtained by the two calculations agree with each other the difference being only by 25%.
Study of thorium-uranium based molten salt blanket in a fusion-fission hybrid reactor
Energy Technology Data Exchange (ETDEWEB)
Zhao Jing, E-mail: zhao_jing@mail.tsinghua.edu.cn [INET, Tsinghua University, Beijing 100084 (China); Yang Yongwei; Zhou Zhiwei [INET, Tsinghua University, Beijing 100084 (China)
2012-08-15
Highlights: Black-Right-Pointing-Pointer A molten salt blanket has been designed for the fusion-fission hybrid reactor. Black-Right-Pointing-Pointer The use of Thorium in the molten salt fuels has been studied. Black-Right-Pointing-Pointer The molten salt was consisted of F-Li-Be and with the thickness of 40 cm. Black-Right-Pointing-Pointer The concentration of {sup 6}Li was chosen to be the natural enrichment ratio. Black-Right-Pointing-Pointer The result shows that TBR is greater than 1, M is about 15-16. - Abstract: Not only solid fuels, but also liquid fuels can be used for the fusion-fission symbiotic reactor blanket. The operational record of the molten salt reactor with F-Li-Be was very successful, so the F-Li-Be blanket was chosen for research. The molten salt has several features which are suited for the fusion-fission applications. The fuel material uranium and thorium were dissolved in the F-Li-Be molten salt. A combined program, COUPLE, was used for neutronics analysis of the molten salt blanket. Several cases have been calculated and compared. Not only the influence of the different fuels have been studied, but also the thickness of the molten salt, and the concentration of the {sup 6}Li in the molten salt. Preliminary studies indicate that when thorium-uranium-plutonium fuels were added into a F-Li-Be molten salt blanket and with a component of 71% LiF-2% BeF{sub 2}-13.5% ThF{sub 4}-8.5% UF{sub 4}-5% PuF{sub 3}, and also with the molten salt thickness of 40 cm and natural concentration of {sup 6}Li, the appropriate blanket energy multiplication factor and TBR can be obtained. The result shows that thorium-uranium molten salt can be used in the blanket of a fusion-fission symbiotic reactor. The research on the molten salt blanket must be valuable for the design of fusion-fission symbiotic reactor.
Control of a laser inertial confinement fusion-fission power plant
Energy Technology Data Exchange (ETDEWEB)
Moses, Edward I.; Latkowski, Jeffery F.; Kramer, Kevin J.
2015-10-27
A laser inertial-confinement fusion-fission energy power plant is described. The fusion-fission hybrid system uses inertial confinement fusion to produce neutrons from a fusion reaction of deuterium and tritium. The fusion neutrons drive a sub-critical blanket of fissile or fertile fuel. A coolant circulated through the fuel extracts heat from the fuel that is used to generate electricity. The inertial confinement fusion reaction can be implemented using central hot spot or fast ignition fusion, and direct or indirect drive. The fusion neutrons result in ultra-deep burn-up of the fuel in the fission blanket, thus enabling the burning of nuclear waste. Fuels include depleted uranium, natural uranium, enriched uranium, spent nuclear fuel, thorium, and weapons grade plutonium. LIFE engines can meet worldwide electricity needs in a safe and sustainable manner, while drastically shrinking the highly undesirable stockpiles of depleted uranium, spent nuclear fuel and excess weapons materials.
Energy Technology Data Exchange (ETDEWEB)
Gabriel, T.A.; Bishop, B.L.; Wiffen, F.W.
1979-08-01
In order to plan radiation damage experiments in fission reactors keyed toward fusion reactor applications, it is necessary to have available for these facilities displacement per atom (dpa) and gas production rates for many potential materials. This report supplies such data for the elemental constituents of alloys of interest to the United States fusion reactor alloy development program. The calculations are presented for positions of interest in the HFIR, ORR, and EBR-II reactors. DPA and gas production rates in alloys of interest can be synthesized from these results.
Can Fusion and Fission Breeding Help Civilization Survive?
Manheiemr, Wallace
2006-12-01
As apparent from the title, this author feels that civilization faces a real threat, one which will become obvious and serious within the lifetimes of many readers of this article. This threat is not global warming, but lack of affordable energy. We take for granted turning on a light, or adjusting our thermostats in winter or summer, or filling our cars gas tank; and lose sight of the fact that there are huge and complicated industrial systems which make this possible. But as we run out of petroleum and natural gas, and worry about the environmental and climatic effects of burning coal on the required scale, how can this continue? This paper makes the case that breeding nuclear fuel, by both fusion and fission, is the only way our civilization as we know it, can continue beyond the next half century or so.
Predation risk shapes social networks in fission-fusion populations.
Directory of Open Access Journals (Sweden)
Jennifer L Kelley
Full Text Available Predation risk is often associated with group formation in prey, but recent advances in methods for analysing the social structure of animal societies make it possible to quantify the effects of risk on the complex dynamics of spatial and temporal organisation. In this paper we use social network analysis to investigate the impact of variation in predation risk on the social structure of guppy shoals and the frequency and duration of shoal splitting (fission and merging (fusion events. Our analyses revealed that variation in the level of predation risk was associated with divergent social dynamics, with fish in high-risk populations displaying a greater number of associations with overall greater strength and connectedness than those from low-risk sites. Temporal patterns of organisation also differed according to predation risk, with fission events more likely to occur over two short time periods (5 minutes and 20 minutes in low-predation fish and over longer time scales (>1.5 hours in high-predation fish. Our findings suggest that predation risk influences the fine-scale social structure of prey populations and that the temporal aspects of organisation play a key role in defining social systems.
Emergence of the mitochondrial reticulum from fission and fusion dynamics.
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Valerii M Sukhorukov
Full Text Available Mitochondria form a dynamic tubular reticulum within eukaryotic cells. Currently, quantitative understanding of its morphological characteristics is largely absent, despite major progress in deciphering the molecular fission and fusion machineries shaping its structure. Here we address the principles of formation and the large-scale organization of the cell-wide network of mitochondria. On the basis of experimentally determined structural features we establish the tip-to-tip and tip-to-side fission and fusion events as dominant reactions in the motility of this organelle. Subsequently, we introduce a graph-based model of the chondriome able to encompass its inherent variability in a single framework. Using both mean-field deterministic and explicit stochastic mathematical methods we establish a relationship between the chondriome structural network characteristics and underlying kinetic rate parameters. The computational analysis indicates that mitochondrial networks exhibit a percolation threshold. Intrinsic morphological instability of the mitochondrial reticulum resulting from its vicinity to the percolation transition is proposed as a novel mechanism that can be utilized by cells for optimizing their functional competence via dynamic remodeling of the chondriome. The detailed size distribution of the network components predicted by the dynamic graph representation introduces a relationship between chondriome characteristics and cell function. It forms a basis for understanding the architecture of mitochondria as a cell-wide but inhomogeneous organelle. Analysis of the reticulum adaptive configuration offers a direct clarification for its impact on numerous physiological processes strongly dependent on mitochondrial dynamics and organization, such as efficiency of cellular metabolism, tissue differentiation and aging.
Burning high-level TRU waste in fusion fission reactors
Shen, Yaosong
2016-09-01
Recently, the concept of actinide burning instead of a once-through fuel cycle for disposing spent nuclear fuel seems to get much more attention. A new method of burning high-level transuranic (TRU) waste combined with Thorium-Uranium (Th-U) fuel in the subcritical reactors driven by external fusion neutron sources is proposed in this paper. The thorium-based TRU fuel burns all of the long-lived actinides via a hard neutron spectrum while outputting power. A one-dimensional model of the reactor concept was built by means of the ONESN_BURN code with new data libraries. The numerical results included actinide radioactivity, biological hazard potential, and much higher burnup rate of high-level transuranic waste. The comparison of the fusion-fission reactor with the thermal reactor shows that the harder neutron spectrum is more efficient than the soft. The Th-U cycle produces less TRU, less radiotoxicity and fewer long-lived actinides. The Th-U cycle provides breeding of 233U with a long operation time (>20 years), hence significantly reducing the reactivity swing while improving safety and burnup.
Fusion-fission probabilities, cross sections and structure notes of super-heavy nuclei
Kowal, Michał; Jachimowicz, Piotr; Skalski, Janusz; Siwek-Wilczyńska, Krystyna; Wilczyński, Janusz
2016-01-01
Fusion - fission probabilities in the synthesis of heaviest elements are discussed in the context of the latest experimental reports. Cross sections for superheavy nuclei are evaluated using "Fusion by Diffusion" (FBD) model. Predictive power of this approach is shown for experimentally known Lv, Og isotopes and predictions given for Z=119,120. Ground state and saddle point properties as: masses, shell corrections, pairing energies and deformations necessary for cross section estimations are calculated systematically within the multidimensional microscopic - macroscopic method based on the deformed Woods-Saxon single particle potential. In the frame of FBD approach predictions for production of elements heavier than Z = 118 are not too optimistic. For this reason, and because of high instability of superheavy nuclei, we comment on some structure effects, connected with the K-isomerism phenomenon which could lead to a significant increase in the stability of these systems.
Fusion-fission probabilities, cross sections, and structure notes of superheavy nuclei
Kowal, Michał; Cap, Tomasz; Jachimowicz, Piotr; Skalski, Janusz; Siwek-Wilczyńska, Krystyna; Wilczyński, Janusz
2016-12-01
Fusion - fission probabilities in the synthesis of heaviest elements are discussed in the context of the latest experimental reports. Cross sections for superheavy nuclei are evaluated using the "Fusion by Diffusion" (FBD) model. Predictive power of this approach is shown for experimentally known Lv and Og isotopes and predictions given for Z = 119, 120. Ground state and saddle point properties as masses, shell corrections, pairing energies, and deformations necessary for cross-section estimations are calculated systematically within the multidimensional microscopic-macroscopic method based on the deformed Woods-Saxon single-particle potential. In the frame of the FBD approach predictions for production of elements heavier than Z = 118 are not too optimistic. For this reason, and because of high instability of superheavy nuclei, we comment on some structure effects, connected with the K-isomerism phenomenon which could lead to a significant increase in the stability of these systems.
Energy Technology Data Exchange (ETDEWEB)
Dobrowolski, A
2006-04-15
This thesis work is centred on some essential ingredients of a theoretical description of the reaction dynamics of the nuclear fusion and fission process, such as the interaction potential between projectile and target nuclei for fusion and the deformation energy landscape in a multidimensional space for the fission process. We have in particular evaluated the importance of the difference between the neutron and proton density distributions on these 2 processes. The fusion potential between the two interacting nuclei is obtained through the nucleon densities, determined in a self-consistent way through semiclassical density variational calculations for a given effective nucleon-nucleon effective interaction of the Skyrme type. These fusion barriers can then be used in a Langevin formalism to evaluation fusion cross sections. For the fission process it turns out to be essential to allow for the large variety of shapes which appear between the nuclear ground state and the the scission configuration. We show that a shape parametrisation taking into account elongation, as well as possible neck formation, left-right asymmetry and non-axiality allows a precise description of this phenomena in the framework of the macroscopic-microscopic approach. We are thus able to enrich the expression of the liquid-drop type energy through a term which describes the variation of the nuclear energy due to a deformation difference between the proton and neutron distribution. The resulting reduction of the fission barriers is only of the order of one MeV but this can easily cause a change in the fission cross-section by an order of magnitude and thus plays a capital role for the stability of super-heavy of exotic nuclei. (author)
Eslamizadeh, H.
2016-10-01
Abstract. A stochastic approach based on four-dimensional Langevin equations was applied to calculate the anisotropy of fission fragment angular distributions, average prescission neutron multiplicity, and the fission probability in a wide range of fissile parameters for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf produced in fusion reactions. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis K were considered in the four-dimensional dynamical model. In the dynamical calculations, nuclear dissipation was generated through the chaos-weighted wall and window friction formula. Furthermore, in the dynamical calculations the dissipation coefficient of K ,γk was considered as a free parameter, and its magnitude inferred by fitting measured data on the anisotropy of fission fragment angular distributions for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf. Comparison of the calculated results for the anisotropy of fission fragment angular distributions with the experimental data showed that the results of the calculations are in good agreement with the experimental data by using values of the dissipation coefficient of K equal to (0.185-0.205), (0.175-0.192), (0.077-0.090), and (0.075-0.085) (MeVzs ) -1 /2 for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf, respectively. It was also shown that the influence of the dissipation coefficient of K on the results of the calculations of the prescission neutron multiplicity and fission probability is small.
Clement, J. D.
1973-01-01
Different types of nuclear fission reactors and fissionable materials are compared. Special emphasis is placed upon the environmental impact of such reactors. Graphs and charts comparing reactor facilities in the U. S. are presented.
Uncertainties in fission-product decay-heat calculations
Energy Technology Data Exchange (ETDEWEB)
Oyamatsu, K.; Ohta, H.; Miyazono, T.; Tasaka, K. [Nagoya Univ. (Japan)
1997-03-01
The present precision of the aggregate decay heat calculations is studied quantitatively for 50 fissioning systems. In this evaluation, nuclear data and their uncertainty data are taken from ENDF/B-VI nuclear data library and those which are not available in this library are supplemented by a theoretical consideration. An approximate method is proposed to simplify the evaluation of the uncertainties in the aggregate decay heat calculations so that we can point out easily nuclei which cause large uncertainties in the calculated decay heat values. In this paper, we attempt to clarify the justification of the approximation which was not very clear at the early stage of the study. We find that the aggregate decay heat uncertainties for minor actinides such as Am and Cm isotopes are 3-5 times as large as those for {sup 235}U and {sup 239}Pu. The recommended values by Atomic Energy Society of Japan (AESJ) were given for 3 major fissioning systems, {sup 235}U(t), {sup 239}Pu(t) and {sup 238}U(f). The present results are consistent with the AESJ values for these systems although the two evaluations used different nuclear data libraries and approximations. Therefore, the present results can also be considered to supplement the uncertainty values for the remaining 17 fissioning systems in JNDC2, which were not treated in the AESJ evaluation. Furthermore, we attempt to list nuclear data which cause large uncertainties in decay heat calculations for the future revision of decay and yield data libraries. (author)
Fission products, activity calculation of spent-fuel
Energy Technology Data Exchange (ETDEWEB)
Souka, N.; El-Hakiem, M.N.
1981-01-01
This work is a scrutiny of the activity of burned up fuel elements of the ET-RR-1. A knowledge of this activity as well as its decay with time is quite helpful in shielding calculations related to construction purposes of hot facilities. The present treatment is based on a knowledge of: fuel composition, percentage burnup, and fission yields of produced isotopes. Cooling periods ranging from 1 hr to 10 years were considered.
The MCEF code for nuclear evaporation and fission calculations
Energy Technology Data Exchange (ETDEWEB)
Deppman, A.; Pina, S.R. de; Likhachev, V.P.; Mesa, J. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica; Tavares, O.A.P.; Duarte, S.B.; Oliveira, E.C. de [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Arruda-Neto, J.D.T. [Universidade Santo Amaro (UNISA), SP (Brazil); Rodriguez, O. [Instituto Superior de Ciencias y Tecnologia Nucleares, La Habana (Cuba); Goncalves, M. [Instituto de Radioprotecao e Dosimetria (IRD), Rio de Janeiro, RJ (Brazil)
2001-11-01
We present an object oriented algorithm, written in the Java programming language, which performs a Monte Carlo calculation of the evaporation-fission process taking place inside an excited nucleus. We show that this nuclear physics problem is very suited for the object oriented programming by constructing two simple objects: one that handles all nuclear properties and another that takes care of the nuclear reaction. The MCEF code was used to calculate important results for nuclear reactions, and here we show examples of possible uses for this code. (author)
Allowance for the tunnel effect in the entrance channel of fusion-fission reactions
Litnevsky, V. L.; Kosenko, G. I.; Ivanyuk, F. A.
2016-05-01
A two-stage model is developed in order to describe fusion-fission reactions. The process in the course of which colliding ions approach each other is simulated at the first stage, the deformations and relative orientations of the ions being taken into account. The first stage of the calculation is completed as soon as colliding nuclei touch each other. A continuous nuclear system (monosystem) is formed at this instant. The emerging distributions of the angular momenta of this system and of its potential and internal energies at the point of touching are used as input data that are necessary for triggering the second stage of the calculation. The evolution of collective coordinates that describe the shape of the monosystem is calculated at the second stage. The description of this evolution is terminated either at the instant of its fission or upon the release of a major part of its excess energy via particle and photon emission. In the latter case, the probability for the fission of the monosystem or a further decrease in its excitation energy becomes extremely small. The ion-collision process and the evolution of the monosystem formed after primary nuclei come into contact are simulated on the basis of stochastic Langevin equations. The quantities appearing in them (which include the potential energy and inertial and friction parameters) are determined with allowance for the shell structure of nuclei. The tunneling of colliding nuclei through the Coulomb barrier is taken into account, and the effect of this phenomenon on model predictions is studied.
TRAP1 controls mitochondrial fusion/fission balance through Drp1 and Mff expression.
Directory of Open Access Journals (Sweden)
Hironori Takamura
Full Text Available Mitochondria are dynamic organelles that change in response to extracellular stimuli. These changes are essential for normal mitochondrial/cellular function and are controlled by a tight balance between two antagonistic pathways that promote fusion and fission. Although some molecules have been identified to mediate the mitochondrial fusion and fission process, the underlying mechanisms remain unclear. Tumor necrosis factor receptor-associated protein 1 (TRAP1 is a mitochondrial molecule that regulates a variety of mitochondrial functions. Here, we examined the role of TRAP1 in the regulation of morphology. Stable TRAP1 knockdown cells showed abnormal mitochondrial morphology, and we observed significant decreases in dynamin-related protein 1 (Drp1 and mitochondrial fission factor (Mff, mitochondrial fission proteins. Similar results were obtained by transient knockdown of TRAP1 in two different cell lines, SH-SY5Y neuroblastoma cells and KNS-42 glioma cells. However, TRAP1 knockdown did not affect expression levels of fusion proteins. The reduction in Drp1 and Mff protein levels was rescued following treatment with the proteasome inhibitor MG132. These results suggest that TRAP1 regulates the expression of fission proteins and controls mitochondrial fusion/fission, which affects mitochondrial/cellular function.
Deceleration of fusion-fission cycles improves mitochondrial quality control during aging.
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Marc Thilo Figge
Full Text Available Mitochondrial dynamics and mitophagy play a key role in ensuring mitochondrial quality control. Impairment thereof was proposed to be causative to neurodegenerative diseases, diabetes, and cancer. Accumulation of mitochondrial dysfunction was further linked to aging. Here we applied a probabilistic modeling approach integrating our current knowledge on mitochondrial biology allowing us to simulate mitochondrial function and quality control during aging in silico. We demonstrate that cycles of fusion and fission and mitophagy indeed are essential for ensuring a high average quality of mitochondria, even under conditions in which random molecular damage is present. Prompted by earlier observations that mitochondrial fission itself can cause a partial drop in mitochondrial membrane potential, we tested the consequences of mitochondrial dynamics being harmful on its own. Next to directly impairing mitochondrial function, pre-existing molecular damage may be propagated and enhanced across the mitochondrial population by content mixing. In this situation, such an infection-like phenomenon impairs mitochondrial quality control progressively. However, when imposing an age-dependent deceleration of cycles of fusion and fission, we observe a delay in the loss of average quality of mitochondria. This provides a rational why fusion and fission rates are reduced during aging and why loss of a mitochondrial fission factor can extend life span in fungi. We propose the 'mitochondrial infectious damage adaptation' (MIDA model according to which a deceleration of fusion-fission cycles reflects a systemic adaptation increasing life span.
Winterberg, Friedwardt
2009-05-01
The recently proposed Super Marx pure deuterium micro-detonation ignition concept [1] is compared to the Lawrence Livermore National Ignition Facility (NIF) laser DT fusion-fission hybrid concept (LIFE) [2]. A typical example of the LIFE concept is a fusion gain 30, and a fission gain of 10, making up for a total gain of 300, with about 10 times more energy released into fission as compared to fusion. This means a substantial release of fission products, as in fusion-less pure fission reactors. In the Super Marx approach for the ignition of a pure deuterium micro-detonation gains of the same magnitude can in theory be reached. If the theoretical prediction can be supported by more elaborate calculations, the Super Marx approach is likely to make lasers obsolete as a means for the ignition of thermonuclear micro-explosions. [1] ``Ignition of a Deuterium Micro-Detonation with a Gigavolt Super Marx Generator,'' Winterberg, F., Journal of Fusion Energy, Springer, 2008. http://www.springerlink.com/content/r2j046177j331241/fulltext.pdf. [2] ``LIFE: Clean Energy from Nuclear Waste,'' https://lasers.llnl.gov/missions/energy&_slash;for&_slash;the&_slash;future/life/
Molecular dynamics simulations of cluster fission and fusion processes
DEFF Research Database (Denmark)
Lyalin, Andrey G.; Obolensky, Oleg I.; Solov'yov, Ilia
2004-01-01
Results of molecular dynamics simulations of fission reactions Na_10^2+ --> Na_7^+ +Na_3^+ and Na_18^2+ --> 2Na_9^+ are presented. The dependence of the fission barriers on the isomer structure of the parent cluster is analyzed. It is demonstrated that the energy necessary for removing homothetic...... groups of atoms from the parent cluster is largely independent of the isomer form of the parent cluster. The importance of rearrangement of the cluster structure during the fission process is elucidated. This rearrangement may include transition to another isomer state of the parent cluster before actual...
Decay characteristics of fission products and summation calculation
Energy Technology Data Exchange (ETDEWEB)
Yoshida, Tadashi [Faculty of Engineering, Musashi Institute of Technology, Tokyo (Japan)
1999-02-01
This paper reviews the decay characteristics of fission products on the viewpoint of summation calculation. The fission products (FPs) are accumulated in the operating power reactors. As they are neutron-rich at the time of scission, they undergo successive beta decays toward stable nuclides. To grasp the quantity of an arbitrary nuclide, fission yields, decay constants and blanching ratios of the nuclide in the same decay chain ( a mass chain of the fixed mass is sufficient) must be known. As a neutron capture increases the mass, and release of a delayed neutron decreases the mass, capture cross sections and delayed neutron emitting ratios are also required. If these values of all FP are known, the quantities such as time dependent decay heat and the delayed neutron fraction can be calculated by summation of the contribution of the nuclides. A computer code ORIGEN-2 is a typical example to compute these quantities. The more important than computer code is the data library for summation calculation which includes physical constants such as fission yields, decay constants, blanching ratio, beta and gamma energy emitted at a beta decay, delayed neutron emitting ratios, and neutron capture cross sections for more than 1000 FP nuclides. They are realized in JNDC FP Decay Data Library-Version 2 of Japan, JEF-2 by western European countries, and ENDF/B-VI of USA. The early versions (until early 80's) of these full-scale libraries showed worse agreement with experiment than the old libraries based on approximations and estimates. The application of the gross theory to beta-decay' to short-lived FPs could solve the problem. The above disagreement is explained by having dropped of high excitation levels of short lived daughter nuclides. This is called as Pandemonium Problem. The summation calculation for the gamma ray spectrum succeeded to predict the experimental value by correcting theoretical spectrum. However, there remains still an underestimate for cooling
Energy Technology Data Exchange (ETDEWEB)
Koch, M.; Kazimi, M.S.
1991-04-01
Limitations of the fission fuel resources will presumably mandate the replacement of thermal fission reactors by fast fission reactors that operate on a self-sufficient closed fuel cycle. This replacement might take place within the next one hundred years, so the direct competitors of fusion reactors will be fission reactors of the latter rather than the former type. Also, fast fission reactors, in contrast to thermal fission reactors, have the potential for transmuting long-lived actinides into short-lived fission products. The associated reduction of the long-term activation of radioactive waste due to actinides makes the comparison of radioactive waste from fast fission reactors to that from fusion reactors more rewarding than the comparison of radioactive waste from thermal fission reactors to that from fusion reactors. Radioactive waste from an experimental and a commercial fast fission reactor and an experimental and a commercial fusion reactor has been characterized. The fast fission reactors chosen for this study were the Experimental Breeder Reactor 2 and the Integral Fast Reactor. The fusion reactors chosen for this study were the International Thermonuclear Experimental Reactor and a Reduced Activation Ferrite Helium Tokamak. The comparison of radioactive waste parameters shows that radioactive waste from the experimental fast fission reactor may be less hazardous than that from the experimental fusion reactor. Inclusion of the actinides would reverse this conclusion only in the long-term. Radioactive waste from the commercial fusion reactor may always be less hazardous than that from the commercial fast fission reactor, irrespective of the inclusion or exclusion of the actinides. The fusion waste would even be far less hazardous, if advanced structural materials, like silicon carbide or vanadium alloy, were employed.
Dynamical Safety Analysis of the SABR Fusion-Fission Hybrid Reactor
Sumner, Tyler; Stacey, Weston; Ghiaassian, Seyed
2009-11-01
A hybrid fusion-fission reactor for the transmutation of spent nuclear fuel is being developed at Georgia Tech. The Subcritical Advanced Burner Reactor (SABR) is a 3000 MWth sodium-cooled, metal TRU-Zr fueled fast reactor driven by a tokamak fusion neutron source based on ITER physics and technology. We are investigating the accident dynamics of SABR's coupled fission, fusion and heat removal systems to explore the safety characteristics of a hybrid reactor. Possible accident scenarios such as loss of coolant mass flow (LOFA), of power (LOPA) and of heat sink (LOHSA), as well as inadvertent reactivity insertions and fusion source excursion are being analyzed using the RELAP5-3D code, the ATHENA version of which includes liquid metal coolants.
Fusion-Fission Research Facility (FFRF) as a Practical Step Toward Hybrids
Energy Technology Data Exchange (ETDEWEB)
L. Zakharov, J. Li and Y. Wu
2010-11-18
The project of ASIPP (with PPPL participation), called FFRF, (R/a=4/1 m/m, Ipl=5 MA, Btor=4-6 T, PDT=50-100 MW, Pfission=80-4000 MW, 1 m thick blanket) is outlined. FFRF stands for the Fusion-Fission Research Facility with a unique fusion mission and a pioneering mission of merging fusion and fission for accumulation of design, experimental, and operational data for future hybrid applications. The design of FFRF will use as much as possible the EAST and ITER design experience. On the other hand, FFRF strongly relies on new, Lithium Wall Fusion plasma regimes, the development of which has already started in the US and China.
Shi, Xue-Ming; Peng, Xian-Jue
2016-09-01
Fusion science and technology has made progress in the last decades. However, commercialization of fusion reactors still faces challenges relating to higher fusion energy gain, irradiation-resistant material, and tritium self-sufficiency. Fusion Fission Hybrid Reactors (FFHR) can be introduced to accelerate the early application of fusion energy. Traditionally, FFHRs have been classified as either breeders or transmuters. Both need partition of plutonium from spent fuel, which will pose nuclear proliferation risks. A conceptual design of a Fusion Fission Hybrid Reactor for Energy (FFHR-E), which can make full use of natural uranium with lower nuclear proliferation risk, is presented. The fusion core parameters are similar to those of the International Thermonuclear Experimental Reactor. An alloy of natural uranium and zirconium is adopted in the fission blanket, which is cooled by light water. In order to model blanket burnup problems, a linkage code MCORGS, which couples MCNP4B and ORIGEN-S, is developed and validated through several typical benchmarks. The average blanket energy Multiplication and Tritium Breeding Ratio can be maintained at 10 and 1.15 respectively over tens of years of continuous irradiation. If simple reprocessing without separation of plutonium from uranium is adopted every few years, FFHR-E can achieve better neutronic performance. MCORGS has also been used to analyze the ultra-deep burnup model of Laser Inertial Confinement Fusion Fission Energy (LIFE) from LLNL, and a new blanket design that uses Pb instead of Be as the neutron multiplier is proposed. In addition, MCORGS has been used to simulate the fluid transmuter model of the In-Zinerater from Sandia. A brief comparison of LIFE, In-Zinerater, and FFHR-E will be given.
Neutron-energy-dependent defect production cross sections for fission and fusion applications
Energy Technology Data Exchange (ETDEWEB)
Odette, G.R.; Doiron, D.R.
1976-06-01
Neutron cross sections for displacements and post-short-term cascade annealing defects are derived from nuclear kinematics calculations of primary atomic recoil energy distributions and the number of secondary defects produced per primary as a function of recoil energy. For the first time, recoil kinematics of charged- and multiple-particle emission reactions are treated rigorously using a compound-nucleus evaporation spectrum nuclear model. Secondary-defect production functions, derived from computer simulation experiments, are taken from the literature. Spectral-averaged defect production cross sections for a fusion reactor first-wall-type environment are on the order of 1.5 to 2.5 times those for a fast fission reactor core-type spectrum. The indicated range of uncertainty is primarily due to secondary-defect production model sensitivity. Nuclear model and data errors are expected to become more significant at high neutron energies, greater than approximately 20 MeV. Fusion reactor environments are found to produce some very energetic recoils and high-energy release events due to charged-particle reactions such as (n,..cap alpha..).
Directory of Open Access Journals (Sweden)
Laken C. Woods
2016-03-01
Full Text Available Mitochondrial function is dependent upon mitochondrial structure which is in turn dependent upon mitochondrial dynamics, including fission, fusion, and motility. Here we examined the relationship between mitochondrial dynamics and the cytoskeleton in Dictyostelium discoideum. Using time-lapse analysis, we quantified mitochondrial fission, fusion, and motility in the presence of cytoskeleton disrupting pharmaceuticals and the absence of the potential mitochondria-cytoskeleton linker protein, CluA. Our results indicate that microtubules are essential for mitochondrial movement, as well as fission and fusion; actin plays a less significant role, perhaps selecting the mitochondria for transport. We also suggest that CluA is not a linker protein but plays an unidentified role in mitochondrial fission and fusion. The significance of our work is to gain further insight into the role the cytoskeleton plays in mitochondrial dynamics and function. By better understanding these processes we can better appreciate the underlying mitochondrial contributions to many neurological disorders characterized by altered mitochondrial dynamics, structure, and/or function.
Short-Term Forecasting of Taiwanese Earthquakes Using a Universal Model of Fusion-Fission Processes
Cheong, S.A.; Tan, T.L.; Chen, C.-C.; Chang, W.-L.; Liu, Z.; Chew, L.Y.; Sloot, P.M.A.; Johnson, N.F.
2014-01-01
Predicting how large an earthquake can be, where and when it will strike remains an elusive goal in spite of the ever-increasing volume of data collected by earth scientists. In this paper, we introduce a universal model of fusion-fission processes that can be used to predict earthquakes starting fr
Actinide incineration in fusion-fission hybrid-A model nuclear synergy
Taczanowski, Stefan
2012-06-01
The alliance of fusion with fission is a cause worthy of great efforts, as being able to ease (if not even to solve) serious problems that both these forms of nuclear energy are facing. Very high investment costs caused by tokamak enormous size, material consumption and difficult technology put in doubt whether alone the minute demand for fuel raw material (Li) and lack of danger of uncontrolled supercriticality prove sufficient for making it competitive. Preliminary evaluations demonstrated that a radical shift of energy production i.e. the energy gain from plasma to fission blanket is feasible [1]. A reduction in the fusion component to about 2% at given system power allows for a radical drop in plasma Q down to the values of ˜0.2-0.3 achievable in small systems [2] (e.g. mirrors) of sizes comparable to fission reactors. As a result in a Fusion-Driven Actinide Incinerator (FDI) both radiations from the plasma: corpuscular (i.e. neutrons and ions) and photons are drastically reduced. Thus are too, first of all - the neutron induced radiation damage: DPA and gas production, then plasma-wall interactions. The fundamental safety of the system has been proved by simulation of its collapse that has shown preservation its subcriticality. Summarizing, all the above problems may be solved with synergic union of fusion with fission embodied in the concept of FDI - small and less expensive.
Reference mirror hybrid fusion-fission reactor design
Energy Technology Data Exchange (ETDEWEB)
Bender, D.J.; Lee, J.D.; Neef, W.S.
1977-06-08
The status of the reference mirror hybrid reactor design being performed by LLL and General Atomic is summarized. The reactor parameters have been chosen to minimize the cost of producing fissile fuel for consumption in fission power reactors. The design draws on the experience developed at LLL in previous hybrid reactor conceptual designs and on GA expertise in gas-cooling technology and fission reactor mechanical design. As in the past, we have emphasized the use of existing technology where possible and a minimum extrapolation of technology otherwise. We consider our projections for the plasma physics parameters to be conservative, in that they are well-founded on the experiments in 2XIIB and the interpretation of these experiments.
Directory of Open Access Journals (Sweden)
Kaplan Abdullah
2015-01-01
Full Text Available Implementation of projects of new generation nuclear power plants requires the solving of material science and technological issues in developing of reactor materials. Melts of heavy metals (Pb, Bi and Pb-Bi due to their nuclear and thermophysical properties, are the candidate coolants for fast reactors and accelerator-driven systems (ADS. In this study, α, γ, p, n and 3He induced fission cross section calculations for 209Bi target nucleus at high-energy regions for (α,f, (γ,f, (p,f, (n,f and (3He,f reactions have been investigated using different fission reaction models. Mamdouh Table, Sierk, Rotating Liquid Drop and Fission Path models of theoretical fission barriers of TALYS 1.6 code have been used for the fission cross section calculations. The calculated results have been compared with the experimental data taken from the EXFOR database. TALYS 1.6 Sierk model calculations exhibit generally good agreement with the experimental measurements for all reactions used in this study.
Fields, Jerel Adam; Serger, Elisabeth; Campos, Sofia; Divakaruni, Ajit S; Kim, Changyoun; Smith, Kendall; Trejo, Margarita; Adame, Anthony; Spencer, Brian; Rockenstein, Edward; Murphy, Anne N; Ellis, Ronald J; Letendre, Scott; Grant, Igor; Masliah, Eliezer
2016-02-01
HIV-associated neurocognitive disorders (HAND) still occur in approximately 50% of HIV patients, and therapies to combat HAND progression are urgently needed. HIV proteins are released from infected cells and cause neuronal damage, possibly through mitochondrial abnormalities. Altered mitochondrial fission and fusion is implicated in several neurodegenerative disorders. Here, we hypothesized that mitochondrial fission/fusion may be dysregulated in neurons during HAND. We have identified decreased mitochondrial fission protein (dynamin 1-like; DNM1L) in frontal cortex tissues of HAND donors, along with enlarged and elongated mitochondria localized to the soma of damaged neurons. Similar pathology was observed in the brains of GFAP-gp120 tg mice. In vitro, recombinant gp120 decreased total and active DNM1L levels, reduced the level of Mitotracker staining, and increased extracellular acidification rate (ECAR) in primary neurons. DNM1L knockdown enhanced the effects of gp120 as measured by reduced Mitotracker signal in the treated cells. Interestingly, overexpression of DNM1L increased the level of Mitotracker staining in primary rat neurons and reduced neuroinflammation and neurodegeneration in the GFAP-gp120-tg mice. These data suggest that mitochondrial biogenesis dynamics are shifted towards mitochondrial fusion in brains of HAND patients and this may be due to gp120-induced reduction in DNM1L activity. Promoting mitochondrial fission during HIV infection of the CNS may restore mitochondrial biogenesis and prevent neurodegeneration.
Dissipation strength of the tilting degree of freedom in fusion-fission reactions
Directory of Open Access Journals (Sweden)
Nadtochy P. N.
2016-01-01
Full Text Available The four-dimensional Langevin model was applied to calculate a wide set of experimental observables for compound nuclei, formed in heavy-ion fusion-fission reactions. A modified one-body mechanism for nuclear dissipation with a reduction coefficient ks of the contribution from a “wall” formula was used for shapes parameters. Different possibilities of deformation-dependent dissipation coefficient for the K coordinate (γK were investigated. Presented results demonstrate that the influence of the ks and γK parameters on the calculated quantities can be selectively probed. It was found that it is possible to describe experimental data with the deformation-dependent γK coefficient. One of the possibility is to use large values of γK ≃ 0.2 (MeV zs−1/2 for compact shapes featuring no neck and small values of γK ≃ 0.0077 (MeV zs−1/2 for elongated shapes.
Development of Calculation Code for Fission Product and Corrosion Product in PWR’s Primary Loop
Institute of Scientific and Technical Information of China (English)
XU; Zhi-long; WAN; Hai-xia; SHAO; Jing; WU; Xiao-chun; LI; Long; LIU; Xing-min; KE; Guo-tu
2015-01-01
With the basis of study on generation,release and migration of fission product,calculation model for each of the above processes was developed,and calculation method for source term of PWR fission products was established.Study on source term of corrosion product in primary loop was been done.Based on the study of corrosion,
SABR fusion-fission hybrid transmutation reactor design concept
Stacey, Weston
2009-11-01
A conceptual design has been developed for a sub-critical advanced burner reactor (SABR) consisting of i) a sodium cooled fast reactor fueled with the transuranics (TRU) from spent nuclear fuel, and ii) a D-T tokamak fusion neutron source based on ITER physics and technology. Subcritical operation enables more efficient transmutation fuel cycles in TRU fueled reactors (without compromising safety), which may be essential for significant reduction in high-level waste repository requirements. ITER will serve as the prototype for the fusion neutron source, which means SABRs could be implemented to help close the nuclear fuel cycle during the 2^nd quarter of the century.
Fission yield calculation using toy model based on Monte Carlo simulation
Energy Technology Data Exchange (ETDEWEB)
Jubaidah, E-mail: jubaidah@student.itb.ac.id [Nuclear Physics and Biophysics Division, Department of Physics, Bandung Institute of Technology. Jl. Ganesa No. 10 Bandung – West Java, Indonesia 40132 (Indonesia); Physics Department, Faculty of Mathematics and Natural Science – State University of Medan. Jl. Willem Iskandar Pasar V Medan Estate – North Sumatera, Indonesia 20221 (Indonesia); Kurniadi, Rizal, E-mail: rijalk@fi.itb.ac.id [Nuclear Physics and Biophysics Division, Department of Physics, Bandung Institute of Technology. Jl. Ganesa No. 10 Bandung – West Java, Indonesia 40132 (Indonesia)
2015-09-30
Toy model is a new approximation in predicting fission yield distribution. Toy model assumes nucleus as an elastic toy consist of marbles. The number of marbles represents the number of nucleons, A. This toy nucleus is able to imitate the real nucleus properties. In this research, the toy nucleons are only influenced by central force. A heavy toy nucleus induced by a toy nucleon will be split into two fragments. These two fission fragments are called fission yield. In this research, energy entanglement is neglected. Fission process in toy model is illustrated by two Gaussian curves intersecting each other. There are five Gaussian parameters used in this research. They are scission point of the two curves (R{sub c}), mean of left curve (μ{sub L}) and mean of right curve (μ{sub R}), deviation of left curve (σ{sub L}) and deviation of right curve (σ{sub R}). The fission yields distribution is analyses based on Monte Carlo simulation. The result shows that variation in σ or µ can significanly move the average frequency of asymmetry fission yields. This also varies the range of fission yields distribution probability. In addition, variation in iteration coefficient only change the frequency of fission yields. Monte Carlo simulation for fission yield calculation using toy model successfully indicates the same tendency with experiment results, where average of light fission yield is in the range of 90fission yield is in about 135
Social Network Analysis Reveals Potential Fission-Fusion Behavior in a Shark
Haulsee, Danielle E.; Fox, Dewayne A.; Breece, Matthew W.; Brown, Lori M.; Kneebone, Jeff; Skomal, Gregory B.; Oliver, Matthew J.
2016-09-01
Complex social networks and behaviors are difficult to observe for free-living marine species, especially those that move great distances. Using implanted acoustic transceivers to study the inter- and intraspecific interactions of sand tiger sharks Carcharias taurus, we observed group behavior that has historically been associated with higher order mammals. We found evidence strongly suggestive of fission-fusion behavior, or changes in group size and composition of sand tigers, related to five behavioral modes (summering, south migration, community bottleneck, dispersal, north migration). Our study shows sexually dimorphic behavior during migration, in addition to presenting evidence of a potential solitary phase for these typically gregarious sharks. Sand tigers spent up to 95 consecutive and 335 cumulative hours together, with the strongest relationships occurring between males. Species that exhibit fission-fusion group dynamics pose a particularly challenging issue for conservation and management because changes in group size and composition affect population estimates and amplify anthropogenic impacts.
Systems Modeling For The Laser Fusion-Fission Energy (LIFE) Power Plant
Energy Technology Data Exchange (ETDEWEB)
Meier, W R; Abbott, R; Beach, R; Blink, J; Caird, J; Erlandson, A; Farmer, J; Halsey, W; Ladran, T; Latkowski, J; MacIntyre, A; Miles, R; Storm, E
2008-10-02
A systems model has been developed for the Laser Inertial Fusion-Fission Energy (LIFE) power plant. It combines cost-performance scaling models for the major subsystems of the plant including the laser, inertial fusion target factory, engine (i.e., the chamber including the fission and tritium breeding blankets), energy conversion systems and balance of plant. The LIFE plant model is being used to evaluate design trade-offs and to identify high-leverage R&D. At this point, we are focused more on doing self consistent design trades and optimization as opposed to trying to predict a cost of electricity with a high degree of certainty. Key results show the advantage of large scale (>1000 MWe) plants and the importance of minimizing the cost of diodes and balance of plant cost.
Social Network Analysis Reveals Potential Fission-Fusion Behavior in a Shark
Haulsee, Danielle E.; Fox, Dewayne A.; Breece, Matthew W.; Brown, Lori M.; Kneebone, Jeff; Skomal, Gregory B.; Oliver, Matthew J.
2016-01-01
Complex social networks and behaviors are difficult to observe for free-living marine species, especially those that move great distances. Using implanted acoustic transceivers to study the inter- and intraspecific interactions of sand tiger sharks Carcharias taurus, we observed group behavior that has historically been associated with higher order mammals. We found evidence strongly suggestive of fission-fusion behavior, or changes in group size and composition of sand tigers, related to five behavioral modes (summering, south migration, community bottleneck, dispersal, north migration). Our study shows sexually dimorphic behavior during migration, in addition to presenting evidence of a potential solitary phase for these typically gregarious sharks. Sand tigers spent up to 95 consecutive and 335 cumulative hours together, with the strongest relationships occurring between males. Species that exhibit fission-fusion group dynamics pose a particularly challenging issue for conservation and management because changes in group size and composition affect population estimates and amplify anthropogenic impacts. PMID:27686155
Calculation of Fission Observables Through Event-by-Event Simulation
Energy Technology Data Exchange (ETDEWEB)
Randrup, J; Vogt, R
2009-06-04
The increased interest in more exclusive fission observables has demanded more detailed models. We present here a new computational model, FREYA, that aims to met this need by producing large samples of complete fission events from which any observable of interest can then be extracted consistently, including arbitrary correlations. The various model assumptions are described and the potential utility of the model is illustrated by means of several novel correlation observables.
Calculation of Prompt Fission Neutron Spectrum for 233U（n, f） Reaction by Semi-empirical Method
Institute of Scientific and Technical Information of China (English)
CHEN; Yong-jing; LIU; Ting-jin; SHU; Neng-chuan
2013-01-01
The prompt fission neutron spectra for neutron-induced fission of 233U for low energy neutron(below 6 MeV)are calculated using the nuclear evaporation theory with a semi-empirical method,in which the partition of the total excitation energy between the fission fragments for the nth+233U fission
Energy Technology Data Exchange (ETDEWEB)
Schmidt, Luisa; Horta, Ana; Pereira, Sergio; Delicado, Ana [Institute of Social Sciences of the University of Lisbon, Av. Prof. Anibal de Bettencourt, 9 1600-189 Lisbon (Portugal)
2015-07-01
This paper presents results of a comparison of media coverage of fusion and fission energy technologies in three countries (Germany, Spain and Portugal) and in the English language international print media addressing transnational elite, from 2008 to 2012. The analysis showed that the accident in Fukushima in March 2010 did not have significant impact on media framing of nuclear fusion in the major part of print media under investigation. In fact, fusion is clearly dissociated from traditional nuclear (fission) energy and from nuclear accidents. It tends to be portrayed as a safe, clean and unlimited source of energy, although less credited when confronted with research costs, technological feasibility and the possibility to be achieved in a reasonable period of time. On the contrary, fission is portrayed as a hazardous source of energy, expensive when compared to research costs of renewables, hardly a long-term energy option, susceptible to contribute to the proliferation of nuclear weapons or rogue military use. Fukushima accident was consistently discussed in the context of safety problems of nuclear power plants and in many cases appeared not as an isolated event but rather as a reminder of previous nuclear disasters such as Three Miles Island and Chernobyl. (authors)
Fission-fusion dynamics over large distances in raven non-breeders.
Loretto, Matthias-Claudio; Schuster, Richard; Itty, Christian; Marchand, Pascal; Genero, Fulvio; Bugnyar, Thomas
2017-03-23
The influence of fission-fusion dynamics, i.e., temporal variation in group size and composition, on social complexity has been studied in large-brained mammals that rely on social bonds. Little is known about birds, even though some species like ravens have recently received attention for their socio-cognitive skills and use of social bonds. While raven breeders defend territories year-round, non-breeders roam through large areas and form groups at food sources or night roosts. We here examined the fission-fusion patterns of non-breeding ravens over years, investigating whether birds meet repeatedly either at the same or at different locations. We combined four large datasets: presence-absence observations from two study sites (Austria, Italy) and GPS-tracking of ravens across two study areas (Austria, France). As expected, we found a highly dynamic system in which individuals with long phases of temporary settlement had a high probability of meeting others. Although GPS-tagged ravens spread out over thousands of square kilometres, we found repeated associations between almost half of the possible combinations at different locations. Such a system makes repeated interactions between individuals at different sites possible and likely. High fission-fusion dynamics may thus not hinder but shape the social complexity of ravens and, possibly, other long-term bonded birds.
Physics of Fission and Fusion for the Diagnostics and Monitoring of the Deadliest Illness of Mankind
Saxena, Arjun
2015-03-01
The physics of fission and fusion has been well known for the past several decades. It has been used primarily for destructive purposes (e. g., nuclear armaments) with both processes. However for peaceful purposes, e. g., generation of energy, only fission has been used, but not yet fusion. It is also well known that the deadliest illness of mankind is the group of illnesses called mental illnesses. A large segment of the world population is afflicted by them causing more loss of human lives, destruction of families, businesses and overall economy than all the other illnesses combined. Despite outstanding advancements in medical research and huge investments, unfortunately no diagnostic techniques have yet been found which can characterize the patient's mental illness. Consequently, no quantitative monitoring techniques are available to evaluate the efficacy of the various medicines used to treat the patients, and to develop them in the pharmaceutical labs. The purpose of this paper is to apply the constructive aspects of fission and fusion to identify the missing links in the diagnosis and treatment of mental illnesses. Each patient is a unique human being, not a disease or a group of symptoms. This makes it even more difficult to treat the patients suffering from mental illnes
Calculation of Prompt Fission Neutron Spectra for ~(235)U (n,f)
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
The prompt fission neutron spectra for neutron-induced fission of 235U at En<5 MeV are calculated using the nuclear evaporation theory with a semi-empirical model, in which the non-constant temperature and the constant temperature related to the Fermi gas model
Fission cross section calculations of actinides with EMPIRE code
Energy Technology Data Exchange (ETDEWEB)
Sin, M.; Oblozinsky, P.; Herman,M.; Capote,R.
2010-04-30
The cross sections of the neutron induced reactions on {sup 233,234,236}U, {sup 237}Np, {sup 238,242}Pu, {sup 241,243}Am, {sup 242,246}Cm carried out in the energy range 1 keV-20 MeV with EMPIRE code are presented, emphasizing the fission channel. Beside a consistent, accurate set of evaluations, the paper contains arguments supporting the choice of the reaction models and input parameters. A special attention is paid to the fission parameters and their uncertainties.
Saita, Shotaro; Ishihara, Takaya; Maeda, Maki; Iemura, Shun-Ichiro; Natsume, Tohru; Mihara, Katsuyoshi; Ishihara, Naotada
2016-05-01
Mitochondrial morphology is dynamically regulated by fusion and fission. Several GTPase proteins control fusion and fission, and posttranslational modifications of these proteins are important for the regulation. However, it has not been clarified how the fusion and fission is balanced. Here, we report the molecular mechanism to regulate mitochondrial morphology in mammalian cells. Ablation of the mitochondrial fission, by repression of Drp1 or Mff, or by over-expression of MiD49 or MiD51, results in a reduction in the fusion GTPase mitofusins (Mfn1 and Mfn2) in outer membrane and long form of OPA1 (L-OPA1) in inner membrane. RNAi- or CRISPR-induced ablation of Drp1 in HeLa cells enhanced the degradation of Mfns via the ubiquitin-proteasome system (UPS). We further found that UPS-related protein BAT3/BAG6, here we identified as Mfn2-interacting protein, was implicated in the turnover of Mfns in the absence of mitochondrial fission. Ablation of the mitochondrial fission also enhanced the proteolytic cleavage of L-OPA1 to soluble S-OPA1, and the OPA1 processing was reversed by inhibition of the inner membrane protease OMA1 independent on the mitochondrial membrane potential. Our findings showed that the distinct degradation systems of the mitochondrial fusion proteins in different locations are enhanced in response to the mitochondrial morphology.
Multi-modal calculations of prompt fission neutrons from 238U(n, f) at low induced energy
Institute of Scientific and Technical Information of China (English)
ZHENG Na; ZHONG Chun-Lai; FAN Tie-Shuan
2011-01-01
Properties of prompt fission neutrons from 238U(n,f) are calculated for incident neutron energies below 6 MeV using the multi-modal model,including the prompt fission neutron spectrum,the average prompt fission neutron multiplicity,and the prompt fission neutron multiplicity as a function of the fission fragment mass v(A) (usually named “sawtooth” data) The three most dominant fission modes are taken into account.The model parameters are determined on the basis of experimental fission fragment data.The predicted results are in good agreement with the experimental data.
Radiation damage of graphite in fission and fusion reactor systems
Energy Technology Data Exchange (ETDEWEB)
Engle, G.B. (GA Technologies, Inc., San Diego, CA (USA)); Kelly, B.T. (Springfields Nuclear Power Development Labs. (UK))
1984-05-01
Increasing the crystalline perfection of artificial graphites is suggested as one method of reducing the crystallite damage. The life expectance for the isotropic conventional graphites will in each case depend on the reactor component for which it will be used and on its design considerations. Based on neutron damage and related dimensional changes it is estimated graphite will be tenable to about 3x10/sup 22/ n/cm/sup 2/ (EDN) at 400/sup 0/C, 0.6x10/sup 22/ n/cm/sup 2/ (EDN) at 1000/sup 0/C and 1.4x10/sup 22/ n/cm/sup 2/ (EDN) at 1400/sup 0/C. There are no data above 1400/sup 0/C on which to speculate. A dose of 2x10/sup 22/ n/cm/sup 2/ may be accumulated in times ranging from as short as a few months in the first wall region of high power density designs to the fusion plant lifetime (30 years) in the neutron reflector region behind the blanket.
Comparative evaluation of solar, fission, fusion, and fossil energy resources, part 3
Clement, J. D.; Reupke, W. A.
1974-01-01
The role of nuclear fission reactors in becoming an important power source in the world is discussed. The supply of fissile nuclear fuel will be severely depleted by the year 2000. With breeder reactors the world supply of uranium could last thousands of years. However, breeder reactors have problems of a large radioactive inventory and an accident potential which could present an unacceptable hazard. Although breeder reactors afford a possible solution to the energy shortage, their ultimate role will depend on demonstrated safety and acceptable risks and environmental effects. Fusion power would also be a long range, essentially permanent, solution to the world's energy problem. Fusion appears to compare favorably with breeders in safety and environmental effects. Research comparing a controlled fusion reactor with the breeder reactor in solving our long range energy needs is discussed.
Block-free optical quantum Banyan network based on quantum state fusion and fission
Zhu, Chang-Hua; Meng, Yan-Hong; Quan, Dong-Xiao; Zhao, Nan; Pei, Chang-Xing
2014-12-01
Optical switch fabric plays an important role in building multiple-user optical quantum communication networks. Owing to its self-routing property and low complexity, a banyan network is widely used for building switch fabric. While, there is no efficient way to remove internal blocking in a banyan network in a classical way, quantum state fusion, by which the two-dimensional internal quantum states of two photons could be combined into a four-dimensional internal state of a single photon, makes it possible to solve this problem. In this paper, we convert the output mode of quantum state fusion from spatial-polarization mode into time-polarization mode. By combining modified quantum state fusion and quantum state fission with quantum Fredkin gate, we propose a practical scheme to build an optical quantum switch unit which is block free. The scheme can be extended to building more complex units, four of which are shown in this paper.
Energy Technology Data Exchange (ETDEWEB)
Zakharov, Anatoly I.; Adzhemyan, Loran Ts.; Shchekin, Alexander K., E-mail: akshch@list.ru [Department of Statistical Physics, Faculty of Physics, St. Petersburg State University, Ulyanovskaya 1, Petrodvoretz, St. Petersburg 198504 (Russian Federation)
2015-09-28
We have performed direct numerical calculations of the kinetics of relaxation in the system of surfactant spherical micelles under joint action of the molecular mechanism with capture and emission of individual surfactant molecules by molecular aggregates and the mechanism of fusion and fission of the aggregates. As a basis, we have taken the difference equations of aggregation and fragmentation in the form of the generalized kinetic Smoluchowski equations for aggregate concentrations. The calculations have been made with using the droplet model of molecular surfactant aggregates and two modified Smoluchowski models for the coefficients of aggregate-monomer and aggregate-aggregate fusions which take into account the effects of the aggregate size and presence of hydrophobic spots on the aggregate surface. A full set of relaxation times and corresponding relaxation modes for nonequilibrium aggregate distribution in the aggregation number has been found. The dependencies of these relaxation times and modes on the total concentration of surfactant in the solution and the special parameter controlling the probability of fusion in collisions of micelles with other micelles have been studied.
Baden, Andrea L; Webster, Timothy H; Kamilar, Jason M
2016-02-01
Ruffed lemurs (genus Varecia) are often described as having a flexible social organization, such that both cohesive (low fission-fusion dynamics) and fluid (high fission-fusion dynamics) grouping patterns have been observed. In ruffed lemur communities with high fission-fusion dynamics, group members vary in their temporal and spatial dispersion throughout a communally defended territory. These patterns have been likened to those observed in several haplorrhine species that exhibit the most fluid types of fission-fusion social organization (e.g., Pan and Ateles). To substantiate and further refine these claims, we describe the fission-fusion dynamics of a black-and-white ruffed lemur (Varecia variegata) community at Mangevo, an undisturbed primary rainforest site in Ranomafana National Park, Madagascar. We collected instantaneous group scan samples from August 2007-December 2008 (4,044 observation hours) to study and characterize patterns of subgroup size, composition, cohesion, and social association. In 16 consecutive months, we never found all members of the community together. In fact, individuals spent nearly half of their time alone. Subgroups were small, cohesive, and typically of mixed-sex composition. Mixed-sex subgroups were significantly larger, less cohesive, and more common than either male-only or female-only subgroups. Subgroup dynamics were related to shifts in climate, phenology of preferred fruit species, and female reproductive state. On average, association indices were low. Males and females were equally gregarious; however, adult male-male associations were significantly weaker than any other association type. Results presented herein document striking differences in fission-fusion dynamics between black-and-white ruffed lemurs and haplorrhines, while also demonstrating many broad-scale similarities to haplorrhine taxa that possess the most fluid fission-fusion societies.
Materials degradation in fission reactors: Lessons learned of relevance to fusion reactor systems
Was, Gary S.
2007-08-01
The management of materials in power reactor systems has become a critically important activity in assuring the safe, reliable and economical operation of these facilities. Over the years, the commercial nuclear power reactor industry has faced numerous 'surprises' and unexpected occurrences in materials. Mitigation strategies have sometimes solved one problem at the expense of creating another. Other problems have been solved successfully and have motivated the development of techniques to foresee problems before they occur. This paper focuses on three aspects of fission reactor experience that may benefit future fusion systems. The first is identification of parameters and processes that have had a large impact on the behavior of materials in fission systems such as temperature, dose rate, surface condition, gradients, metallurgical variability and effects of the environment. The second is the development of materials performance and failure models to provide a basis for assuring component integrity. Last is the development of proactive materials management programs that identify and pre-empt degradation processes before they can become problems. These aspects of LWR experience along with the growing experience with materials in the more demanding advanced fission reactor systems form the basis for a set of 'lessons learned' to aid in the successful management of materials in fusion reactor systems.
Disentangling association patterns in fission-fusion societies using African buffalo as an example
Cross, P.C.; Lloyd-Smith, J. O.; Getz, W.M.
2005-01-01
A description of the social network of a population aids us in understanding dispersal, the spread of disease, and genetic structure in that population. Many animal populations can be classified as fission–fusion societies, whereby groups form and separate over time. Examples discussed in the literature include ungulates, primates and cetaceans (Lott and Minta, 1983, Whitehead et al., 1991, Henzi et al., 1997, Christal et al., 1998 and Chilvers and Corkeron, 2002). In this study, we use a heuristic simulation model to illustrate potential problems in applying traditional techniques of association analysis to fission–fusion societies and propose a new index of association: the fission decision index (FDI). We compare the conclusions resulting from traditional methods with those of the FDI using data from African buffalo, Syncerus caffer, in the Kruger National Park. The traditional approach suggested that the buffalo population was spatially and temporally structured into four different ‘herds’ with adult males only peripherally associated with mixed herds. Our FDI method indicated that association decisions of adult males appeared random, but those of other sex and age categories were nonrandom, particularly when we included the fission events associated with adult males. Furthermore, the amount of time that individuals spent together was only weakly correlated with their propensity to remain together during fission events. We conclude with a discussion of the applicability of the FDI to other studies.
Fission product inventory calculation by a CASMO/ORIGEN coupling program
Energy Technology Data Exchange (ETDEWEB)
Kim, Do Heon; Kim, Jong Kyung [Hanyang University, Seoul (Korea, Republic of); Choi, Hang Bok; Roh, Gyu Hong; Jung, In Ha [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
1997-12-31
A CASMO/ORIGEN coupling utility program was developed to predict the composition of all the fission products in spent PWR fuels. The coupling program reads the CASMO output file, modifies the ORIGEN cross section library and reconstructs the ORIGEN input file at each depletion step. In ORIGEN, the burnup equation is solved for actinides and fission products based on the fission reaction rates and depletion flux of CASMO. A sample calculation has been performed using a 14 x 14 PWR fuel assembly and the results are given in this paper. 3 refs., 1 fig., 1 tab. (Author)
Calculation of prompt fission neutron spectra for 235U(n,f)
Institute of Scientific and Technical Information of China (English)
CHEN Yong-Jing; JIA Min; TAO Xi; QIAN Jing; LIU Ting-Jin; SHU Neng-Chuan
2012-01-01
The prompt fission neutron spectra for the neutron-induced fission of 235U at En ＜ 5 MeV are calculated using nuclear evaporation theory with a semi-empirical model,in which the nonconstant and constant temperatures related to the Fermi gas model are taken into account. The calculated prompt fission neutron spectra reproduce the experimental data well.For the n(thermal)+235U reaction,the average nuclear temperature of the fission fragment,and the probability distribution of the nuclear temperature,are discussed and compared with the Los Alamos model.The energy carried away by γ rays emitted from each fragment is also obtained and the results are in good agreement with the existing experimental data.
Caamaño, M; Farget, F; Derkx, X; Schmidt, K -H; Audouin, L; Bacri, C -O; Barreau, G; Benlliure, J; Casarejos, E; Chbihi, A; Fernandez-Dominguez, B; Gaudefroy, L; Golabek, C; Jurado, B; Lemasson, A; Navin, A; Rejmund, M; Roger, T; Shrivastava, A; Schmitt, C
2013-01-01
A novel method to access the complete identification in atomic number Z and mass A of fragments produced in low-energy fission of actinides is presented. This method, based on the use of multi- nucleon transfer and fusion reactions in inverse kinematics, is applied in this work to reactions between a 238U beam and a 12C target to produce and induce fission of moderately excited actinides. The fission fragments are detected and fully identified with the VAMOS spectrometer of GANIL, allowing the measurement of fragment yields of several hundreds of isotopes in a range between A ~ 80 and ~ 160, and from Z ~ 30 to ~ 64. For the first time, complete isotopic yield distributions of fragments from well-defined fissioning systems are available. Together with the precise measurement of the fragment emission angles and velocities, this technique gives further insight into the nuclear-fission process.
Augmentation of ENDF/B fission product gamma-ray spectra by calculated spectra
Energy Technology Data Exchange (ETDEWEB)
Katakura, J. (Japan Atomic Energy Research Inst., Tokai-mura, Naka-gun, Ibaraki-ken (Japan)); England, T.R. (Los Alamos National Lab., NM (United States))
1991-11-01
Gamma-ray spectral data of the ENDF/B-V fission product decay data file have been augmented by calculated spectra. The calculations were performed with a model using beta strength functions and cascade gamma-ray transitions. The calculated spectra were applied to individual fission product nuclides. Comparisons with several hundred measured aggregate gamma spectra after fission were performed to confirm the applicability of the calculated spectra. The augmentation was extended to a preliminary ENDF/B-VI file, and to beta spectra. Appendix C provides information on the total decay energies for individual products and some comparisons of measured and aggregate values based on the preliminary ENDF/B-VI files. 15 refs., 411 figs.
Ding, Yuan; Li, Jianmin; Liu, Zhen; Liu, Huaxiang; Li, Hao; Li, Zhenzhong
2017-01-01
Restoring the contractile function of long-term denervated skeletal muscle (SKM) cells is difficult due to the long period of denervation, which causes a loss of contractility. Although sensory innervation is considered a promising protective approach, its effect is still restricted. In this study, we introduced insulin-like growth factor-1 (IGF-1) as an efficient protective agent and observed that IGF-1 potentiated the effects of sensory protection by preventing denervated muscle atrophy and improving the condition of denervated muscle cells in vivo and in vitro. IGF-1-induced Akt phosphorylation suppressed the mitochondrial outer-membrane protein Mul1 expression, which is a key step on preserving contractile property of sensory innervated SKM cells. Mul1 overexpression interfered with the balance between mitochondrial fusion and fission and was a key node for blocking the effects of IGF-1 that preserved the contractility of sensory-innervated SKM cells. Activation of AMP-activated protein kinase α (AMPKα), a mitochondrial downstream target, could block the effects of IGF-1. These data provide novel evidence that might be applied when searching for new approaches to improve the functional condition of long-term denervated SKM cells by increasing sensory protection using the IGF-1 signalling system to modulate the balance between mitochondrial fusion and fission. PMID:28276453
Thermal fission rates with temperature dependent fission barriers
Zhu, Yi; Pei, J. C.
2016-08-01
Background: The fission processes of thermal excited nuclei are conventionally studied by statistical models which rely on inputs of phenomenological level densities and potential barriers. Therefore the microscopic descriptions of spontaneous fission and induced fission are very desirable for a unified understanding of various fission processes. Purpose: We propose to study the fission rates, at both low and high temperatures, with microscopically calculated temperature-dependent fission barriers and collective mass parameters. Methods: The fission barriers are calculated by the finite-temperature Skyrme-Hartree-Fock+BCS method. The mass parameters are calculated by the temperature-dependent cranking approximation. The thermal fission rates can be obtained by the imaginary free energy approach at all temperatures, in which fission barriers are naturally temperature dependent. The fission at low temperatures can be described mainly as a barrier-tunneling process. While the fission at high temperatures has to incorporate the reflection above barriers. Results: Our results of spontaneous fission rates reasonably agree with other studies and experiments. The temperature dependencies of fission barrier heights and curvatures have been discussed. The temperature dependent behaviors of mass parameters have also been discussed. The thermal fission rates from low to high temperatures with a smooth connection have been given by different approaches. Conclusions: Since the temperature dependencies of fission barrier heights and curvatures, and the mass parameters can vary rapidly for different nuclei, the microscopic descriptions of thermal fission rates are very valuable. Our studies without free parameters provide a consistent picture to study various fissions such as that in fast-neutron reactors, astrophysical environments, and fusion reactions for superheavy nuclei.
Fast ion motion in the plasma part of a stellarator-mirror fission-fusion hybrid
Moiseenko, V. E.; Nemov, V. V.; Ågren, O.; Kasilov, S. V.; Garkusha, I. E.
2016-06-01
Recent developments of a stellarator-mirror (SM) fission-fusion hybrid concept are reviewed. The hybrid consists of a fusion neutron source and a powerful sub-critical fast fission reactor core. The aim is transmutation of spent nuclear fuel and safe fission energy production. In its fusion part, a stellarator-type system with an embedded magnetic mirror is used. The stellarator confines deuterium plasma with moderate temperature, 1-2 keV. In the magnetic mirror, a hot component of sloshing tritium ions is trapped. There, the fusion neutrons are generated. A candidate for a combined SM system is a DRACON magnetic trap. A basic idea behind an SM device is to maintain local neutron production in a mirror part, but at the same time eliminate the end losses by using a toroidal device. A possible drawback is that the stellarator part can introduce collision-free radial drift losses, which is the main topic for this study. For high energy ions of tritium with an energy of 70 keV, comparative computations of collisionless losses in the rectilinear part of a specific design of the DRACON type trap are carried out. Two versions of the trap are considered with different lengths of the rectilinear sections. Also the total number of current-carrying rings in the magnetic system is varied. The results predict that high energy ions from neutral beam injection can be satisfactorily confined in the mirror part during 0.1-1 s. The Uragan-2M experimental device is used to check key points of the SM concept. The magnetic configuration of a stellarator with an embedded magnetic mirror is arranged in this device by switching off one toroidal coil. The motion of particles magnetically trapped in the embedded mirror is analyzed numerically with use of motional invariants. It is found that without radial electric field particles quickly drift out of the SM, even if the particles initially are located on a nested magnetic surface. We will show that a weak radial electric field, which
Investigation of the diffusion of atomic fission products in UC by density functional calculations
Energy Technology Data Exchange (ETDEWEB)
Bévillon, Émile, E-mail: emile.bevillon@yahoo.fr [IRSN, SEMIC, DPAM, LETR, Centre de Cadarache, 13115 Saint Paul Lez Durance (France); Ducher, Roland; Barrachin, Marc; Dubourg, Roland [IRSN, SEMIC, DPAM, LETR, Centre de Cadarache, 13115 Saint Paul Lez Durance (France)
2013-03-15
Activation energies of U and C atoms self-diffusion in UC, as well as activation energies of hetero-diffusion of fission products (FPs) are investigated by first-principles calculations. According to a previous study which showed a likely U site occupation was favoured for all the FPs, their diffusion is restricted to the uranium sublattice of UC in the present study. In this framework, long-range displacements are only possible through a concerted mechanism with a surrounding uranium vacancy. Using the apparent formation energies of the uranium vacancy defect calculated in our previous study and the classical approach used in UO{sub 2} by Andersson et al., the activation energies of the main fission products in the various stoichiometric domains have been calculated. The results are compared to those obtained with the five frequency model applied to two representative fission products, Xe and Zr. Interestingly, despite strong differences of formalism, both models provided similar activation energies.
Investigation of the diffusion of atomic fission products in UC by density functional calculations
Bévillon, Émile; Ducher, Roland; Barrachin, Marc; Dubourg, Roland
2013-03-01
Activation energies of U and C atoms self-diffusion in UC, as well as activation energies of hetero-diffusion of fission products (FPs) are investigated by first-principles calculations. According to a previous study which showed a likely U site occupation was favoured for all the FPs, their diffusion is restricted to the uranium sublattice of UC in the present study. In this framework, long-range displacements are only possible through a concerted mechanism with a surrounding uranium vacancy. Using the apparent formation energies of the uranium vacancy defect calculated in our previous study and the classical approach used in UO2 by Andersson et al., the activation energies of the main fission products in the various stoichiometric domains have been calculated. The results are compared to those obtained with the five frequency model applied to two representative fission products, Xe and Zr. Interestingly, despite strong differences of formalism, both models provided similar activation energies.
Institute of Scientific and Technical Information of China (English)
郑娜; 钟春来; 樊铁栓
2012-01-01
An attempt is made to improve the evaluation of the prompt fission neutron emis- sion from 233U(n, f) reaction for incident neutron energies below 6 MeV. The multi-modal fission approach is applied to the improved version of Los Alamos model and the point by point model. The prompt fission neutron spectra and the prompt fission neutron as a function of fragment mass (usually named "sawtooth" data) v(A) are calculated independently for the three most dominant fission modes (standard I, standard II and superlong), and the total spectra and v(A) are syn- thesized. The multi-modal parameters are determined on the basis of experimental data of fission fragment mass distributions. The present calculation results can describe the experimental data very well, and the proposed treatment is thus a useful tool for prompt fission neutron emission prediction.
Evaluation of fission product worth margins in PWR spent nuclear fuel burnup credit calculations.
Energy Technology Data Exchange (ETDEWEB)
Blomquist, R.N.; Finck, P.J.; Jammes, C.; Stenberg, C.G.
1999-02-17
Current criticality safety calculations for the transportation of irradiated LWR fuel make the very conservative assumption that the fuel is fresh. This results in a very substantial overprediction of the actual k{sub eff} of the transportation casks; in certain cases, this decreases the amount of spent fuel which can be loaded in a cask, and increases the cost of transporting the spent fuel to the repository. Accounting for the change of reactivity due to fuel depletion is usually referred to as ''burnup credit.'' The US DOE is currently funding a program aimed at establishing an actinide only burnup credit methodology (in this case, the calculated reactivity takes into account the buildup or depletion of a limited number of actinides). This work is undergoing NRC review. While this methodology is being validated on a significant experimental basis, it implicitly relies on additional margins: in particular, the absorption of neutrons by certain actinides and by all fission products is not taken into account. This provides an important additional margin and helps guarantee that the methodology is conservative provided these neglected absorption are known with reasonable accuracy. This report establishes the accuracy of fission product absorption rate calculations: (1) the analysis of European fission product worth experiments demonstrates that fission product cross-sections available in the US provide very good predictions of fission product worth; (2) this is confirmed by a direct comparison of European and US cross section evaluations; (3) accuracy of Spent Nuclear Fuel (SNF) fission product content predictions is established in a recent ORNL report where several SNF isotopic assays are analyzed; and (4) these data are then combined to establish in a conservative manner the fraction of the predicted total fission product absorption which can be guaranteed based on available experimental data.
Nasirov, A K; Hanappe, F; Heinz, S; Hofmann, S; Mandaglio, G; Manganaro, M; Muminov, A I; Scheid, W
2008-01-01
The yields of evaporation residues, fusion-fission and quasifission fragments in the $^{48}$Ca+$^{144,154}$Sm and $^{16}$O+$^{186}$W reactions are analyzed in the framework of the combined theoretical method based on the dinuclear system concept and advanced statistical model. The measured yields of evaporation residues for the $^{48}$Ca+$^{154}$Sm reaction can be well reproduced. The measured yields of fission fragments are decomposed into contributions coming from fusion-fission, quasifission, and fast-fission. The decrease in the measured yield of quasifission fragments in $^{48}$Ca+$^{154}$Sm at the large collision energies and the lack of quasifission fragments in the $^{48}$Ca+$^{144}$Sm reaction are explained by the overlap in mass-angle distributions of the quasifission and fusion-fission fragments. The investigation of the optimal conditions for the synthesis of the new element $Z$=120 ($A$=302) show that the $^{54}$Cr+$^{248}$Cm reaction is preferable in comparison with the $^{58}$Fe+$^{244}$Pu and ...
Institute of Scientific and Technical Information of China (English)
Fang Jian-Ping; Zheng Chun-Long
2005-01-01
With the help of an extended mapping approach, a series of new types of exact excitations with two arbitrary functions of the (2+1)-dimensional Broer-Kaup-Kupershmidt (BKK) system is derived. Based on the derived solitary wave excitation, some specific soliton fission and fusion solutions of the higher-dimensional BKK system are also obtained.
Short-term forecasting of Taiwanese earthquakes using a universal model of fusion-fission processes.
Cheong, Siew Ann; Tan, Teck Liang; Chen, Chien-Chih; Chang, Wu-Lung; Liu, Zheng; Chew, Lock Yue; Sloot, Peter M A; Johnson, Neil F
2014-01-10
Predicting how large an earthquake can be, where and when it will strike remains an elusive goal in spite of the ever-increasing volume of data collected by earth scientists. In this paper, we introduce a universal model of fusion-fission processes that can be used to predict earthquakes starting from catalog data. We show how the equilibrium dynamics of this model very naturally explains the Gutenberg-Richter law. Using the high-resolution earthquake catalog of Taiwan between Jan 1994 and Feb 2009, we illustrate how out-of-equilibrium spatio-temporal signatures in the time interval between earthquakes and the integrated energy released by earthquakes can be used to reliably determine the times, magnitudes, and locations of large earthquakes, as well as the maximum numbers of large aftershocks that would follow.
Han, Jie
2014-01-01
We investigate time-dependent probability for a Brownian particle passing over the barrier to stay at a metastable potential pocket against escaping over the barrier. This is related to whole fusion-fission dynamical process and can be called the reverse Kramers problem. By the passing probability over the saddle point of inverse harmonic potential multiplying the exponential decay factor of a particle in the metastable potential, we present an approximate expression for the modified passing probability over the barrier, in which the effect of reflection boundary of potential is taken into account. Our analytical result and Langevin Monte-Carlo simulation show that the probability passing and against escaping over the barrier is a non-monotonous function of time and its maximal value is less than the stationary result of passing probability over the saddle point of inverse harmonic potential.
Mitochondrial fission and fusion in astrocytes: a new pathway towards senescence
Directory of Open Access Journals (Sweden)
Sonia Luz Albarracin
2015-02-01
Full Text Available Astrocytes are highly specialized cells that can maintain the integrity of the synapse, facilitate nutrition and trophic support to neurons, and regulate metabolic coupling between neurons and glia. However, astrocytes are involved in resolving different types of injuries and in aging processes in the brain. Senescence has also been reported in the brain, and senescence-associated loss of astrocyte function is linked to neuronal dysfunction in age-related neurodegenerative diseases such as Alzheimer’s disease and Parkinson's disease. For example, astrocyte senescence per se inhibits synapse maturation and affects synaptic transmission. In response to the cell’s bio-energetic state, mitochondria continuously undergo structural remodeling through fission and fusion processes. These tightly regulated events are believed to be involved in many cellular events such as apoptosis, senescence, and age-related diseases. Although, little is known about the age-related changes that occur in astrocytes and if these cells are able to generate a senescent phenotype mediated by mitochondria, in the present study we evaluated the involvement of mitochondrial remodeling in the senescence process of rat astrocytes in vitro. The results obtained showed that when comparing cells at population doubling two (PD2 with cells at population doubling ten (PD10 there is a significant increase in the activity of the senescence-associated β-galactosidase marker in PD10 cells. In addition, PD10 cells had increased mitochondrial volume, decreased superoxide production, and decreased mitochondrial membrane potential. Protein characterization evidenced changes in the balance between mitochondrial fission and fusion proteins. Collectively, our results demonstrated a senescent-astrocyte phenotype at PD10, which is associated with metabolic and mitochondrial phenotype changes.
Sonzogni, A. A.; McCutchan, E. A.; Johnson, T. D.; Dimitriou, P.
2016-04-01
Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 235U 235 fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of 86Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.
Sonzogni, A A; McCutchan, E A; Johnson, T D; Dimitriou, P
2016-04-01
Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 ^{235}U fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of ^{86}Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.
Energy Technology Data Exchange (ETDEWEB)
Raeder, Juergen; Weller, Arthur; Wolf, Robert [Max-Planck-Institut fuer Plasmaphysik (IPP), Garching (Germany); Jin, Xue Zhou; Boccaccini, Lorenzo V.; Stieglitz, Robert; Carloni, Dario [Karlsruher Institute fuer Technologie (KIT), Eggenstein-Leopoldshafen (Germany); Pistner, Christoph [Oeko-Institut e.V., Darmstadt (Germany); Herb, Joachim [Gesellschaft fuer Anlagen- und Reaktorsicherheit, Koeln (Germany)
2016-01-15
This paper summarizes the current state of the art in science and technology of the safety concept for future fusion power plants (FPPs) and examines the transferability of the current nuclear fission regulation to the concepts of future fusion power plants. At the moment there exist only conceptual designs of future fusion power plants. The most detailed concepts with regards to safety aspects were found in the European Power Plant Conceptual Study (PPCS). The plant concepts discussed in the PPCS are based on magnetic confinement of the plasma. The safety concept of fusion power plants, which has been developed during the last decades, is based on the safety concepts of installations with radioactive inventories, especially nuclear fission power plants. It applies the concept of defence in depth. However, there are specific differences between the implementations of the safety concepts due to the physical and technological characteristics of fusion and fission. It is analysed whether for fusion a safety concept is required comparable to the one of fission. For this the consequences of a purely hypothetical release of large amounts of the radioactive inventory of a fusion power plant and a fission power plant are compared. In such an event the evacuation criterion outside the plant is exceeded by several orders of magnitude for a fission power plant. For a fusion power plant the expected radiological consequences are of the order of the evacuation criterion. Therefore, a safety concept is also necessary for fusion to guarantee the confinement of the radioactive inventory. The comparison between the safety concepts for fusion and fission shows that the fundamental safety function ''confinement of the radioactive materials'' can be transferred directly in a methodical way. For a fusion power plant this fundamental safety function is based on both, physical barriers as well as on active retention functions. After the termination of the fusion
Energy Technology Data Exchange (ETDEWEB)
Raeder, Juergen; Weller, Arthur; Wolf, Robert [Max-Planck-Institut fuer Plasmaphysik (IPP), Garching (Germany); Jin, Xue Zhou; Boccaccini, Lorenzo V.; Stieglitz, Robert; Carloni, Dario [Karlsruher Institute fuer Technologie (KIT), Eggenstein-Leopoldshafen (Germany); Pistner, Christoph [Oeko-Institut e.V., Darmstadt (Germany); Herb, Joachim [Gesellschaft fuer Anlagen- und Reaktorsicherheit, Koeln (Germany)
2016-01-15
This paper summarizes the current state of the art in science and technology of the safety concept for future fusion power plants (FPPs) and examines the transferability of the current nuclear fission regulation to the concepts of future fusion power plants. At the moment there exist only conceptual designs of future fusion power plants. The most detailed concepts with regards to safety aspects were found in the European Power Plant Conceptual Study (PPCS). The plant concepts discussed in the PPCS are based on magnetic confinement of the plasma. The safety concept of fusion power plants, which has been developed during the last decades, is based on the safety concepts of installations with radioactive inventories, especially nuclear fission power plants. It applies the concept of defence in depth. However, there are specific differences between the implementations of the safety concepts due to the physical and technological characteristics of fusion and fission. It is analysed whether for fusion a safety concept is required comparable to the one of fission. For this the consequences of a purely hypothetical release of large amounts of the radioactive inventory of a fusion power plant and a fission power plant are compared. In such an event the evacuation criterion outside the plant is exceeded by several orders of magnitude for a fission power plant. For a fusion power plant the expected radiological consequences are of the order of the evacuation criterion. Therefore, a safety concept is also necessary for fusion to guarantee the confinement of the radioactive inventory. The comparison between the safety concepts for fusion and fission shows that the fundamental safety function ''confinement of the radioactive materials'' can be transferred directly in a methodical way. For a fusion power plant this fundamental safety function is based on both, physical barriers as well as on active retention functions. After the termination of the fusion
Siegel, Edward
2011-10-01
Numbers: primality/indivisibility/non-factorization versus compositeness/divisibility /factor-ization, often in tandem but not always, provocatively close analogy to nuclear-physics: (2 + 1)=(fusion)=3; (3+1)=(fission)=4[=2 × 2]; (4+1)=(fusion)=5; (5 +1)=(fission)=6[=2 × 3]; (6 + 1)=(fusion)=7; (7+1)=(fission)=8[= 2 × 4 = 2 × 2 × 2]; (8 + 1) =(non: fission nor fusion)= 9[=3 × 3]; then ONLY composites' Islands of fusion-INstability: 8, 9, 10; then 14, 15, 16,... Could inter-digit Feshbach-resonances exist??? Applications to: quantum-information/computing non-Shore factorization, millennium-problem Riemann-hypotheses proof as Goodkin BEC intersection with graph-theory ``short-cut'' method: Rayleigh(1870)-Polya(1922)-``Anderson'' (1958)-localization, Goldbach-conjecture, financial auditing/accounting as quantum-statistical-physics;... abound!!!
Archie, Elizabeth A; Moss, Cynthia J; Alberts, Susan C
2006-03-07
Many social animals live in stable groups. In contrast, African savannah elephants (Loxodonta africana) live in unusually fluid, fission-fusion societies. That is, 'core' social groups are composed of predictable sets of individuals; however, over the course of hours or days, these groups may temporarily divide and reunite, or they may fuse with other social groups to form much larger social units. Here, we test the hypothesis that genetic relatedness predicts patterns of group fission and fusion among wild, female African elephants. Our study of a single Kenyan population spans 236 individuals in 45 core social groups, genotyped at 11 microsatellite and one mitochondrial DNA (mtDNA) locus. We found that genetic relatedness predicted group fission; adult females remained with their first order maternal relatives when core groups fissioned temporarily. Relatedness also predicted temporary fusion between social groups; core groups were more likely to fuse with each other when the oldest females in each group were genetic relatives. Groups that shared mtDNA haplotypes were also significantly more likely to fuse than groups that did not share mtDNA. Our results suggest that associations between core social groups persist for decades after the original maternal kin have died. We discuss these results in the context of kin selection and its possible role in the evolution of elephant sociality.
Semi-empirical Calculation for Yield of 240Pu Spontaneous Fission
Institute of Scientific and Technical Information of China (English)
SHU; Neng-chuan; LIU; Li-le; CHEN; Xiao-song; LIU; Ting-jin; SUN; Zheng-jun; CHEN; Yong-jing; QIAN; Jing
2012-01-01
<正>The spontaneous fission yield has important implication in the nuclear engineering. This work used semi-empirical model to calculate its chain yield, the result shows good agreement with the measured data. There are only 3 sets of measured data, and only too gave the chain yields and cumulative yields, covering 17 chains. It is not enough to satisfy the requirement of users. So it is needed to use theoretical model to calculate the chain yield without measured data.
Calculating fusion neutron energy spectra from arbitrary reactant distributions
Eriksson, J.; Conroy, S.; Andersson Sundén, E.; Hellesen, C.
2016-02-01
The Directional Relativistic Spectrum Simulator (DRESS) code can perform Monte-Carlo calculations of reaction product spectra from arbitrary reactant distributions, using fully relativistic kinematics. The code is set up to calculate energy spectra from neutrons and alpha particles produced in the D(d, n)3He and T(d, n)4He fusion reactions, but any two-body reaction can be simulated by including the corresponding cross section. The code has been thoroughly tested. The kinematics calculations have been benchmarked against the kinematics module of the ROOT Data Analysis Framework. Calculated neutron energy spectra have been validated against tabulated fusion reactivities and against an exact analytical expression for the thermonuclear fusion neutron spectrum, with good agreement. The DRESS code will be used as the core of a detailed synthetic diagnostic framework for neutron measurements at the JET and MAST tokamaks.
Usang, M. D.; Ivanyuk, F. A.; Ishizuka, C.; Chiba, S.
2016-10-01
Nuclear fission is treated by using the Langevin dynamical description with macroscopic and microscopic transport coefficients (mass and friction tensors), and it is elucidated how the microscopic (shell and pairing) effects in the transport coefficients, especially their dependence on temperature, affects various fission observables. We found that the microscopic transport coefficients, calculated by linear response theory, change drastically as a function of temperature: in general, the friction increases with growing temperature while the mass tensor decreases. This temperature dependence brings a noticeable change in the mass distribution and kinetic energies of fission fragments from nuclei around 236U at an excitation energy of 20 MeV. The prescission kinetic energy decreases from 25 MeV at low temperature to about 2.5 MeV at high temperature. In contrast, the Coulomb kinetic energy increases as the temperature increases. Interpolating the microscopic transport coefficients among the various temperatures enabled our Langevin equation to use the microscopic transport coefficients at a deformation-dependent local temperature of the dynamical evolution. This allowed us to compare directly the fission observables of both macroscopic and microscopic calculations, and we found almost identical results under the conditions considered in this work.
Thermal Fission Rate Calculated Numerically by Particles Multi-passing over Saddle Point
Institute of Scientific and Technical Information of China (English)
LIU Ling; BAO Jing-Dong
2004-01-01
Langevin simulation of the particles multi-passing over the saddle point is proposed to calculate thermal fission rate. Due to finite friction and the corresponding thermal fluctuation, a backstreaming exists in the process of the particle descent from the saddle to the scission. This leads to that the diffusion behind the saddle point has influence upon the stationary flow across the saddle point. A dynamical correction factor, as a ratio of the flows of multi- and firstoverpassing the saddle point, is evaluated analytically. The results show that the fission rate calculated by the particles multi-passing over the saddle point is lower than the one calculated by the particle firstly passing over the saddle point,and the former approaches the results at the scission point.
Indian Academy of Sciences (India)
Hadi Eslamizadeh
2015-12-01
The anisotropy of fission fragment angular distribution, evaporation residue crosssection and the fission cross-section were calculated for 197Tl formed in 16O+181Ta reactions in the framework of the modified statistical model and the results were compared with the experimental data. The effects of temperature and projection of spin about the symmetry axis have been considered for calculating potential energy surfaces and fission widths. It was shown that in the framework of the modified statistical model, by choosing appropriate values for the temperature coefficient of the effective potential, , and scaling factor of the fission-barrier height, s, one can satisfactorily reproduce the above-mentioned experimental data. It was also shown that the appropriate values of these parameters for 197Tl are = 0.0185 ± 0.0050 MeV-2 and s = 1.0006 ± 0.0020.
Kim, Do Heon; Gil, Choong-Sup; Chang, Jonghwa; Lee, Yong-Deok
2005-05-01
The neutron absorption cross sections for 18 fission products evaluated within the framework of the KAERI (Korea Atomic Energy Research Institute)-BNL (Brookhaven National Laboratory) international collaboration have been compared with ENDF/B-VI.7. Also, the influence of the new evaluations on the isotopic composition calculations of the fission products has been estimated through the OECD/NEA burnup credit criticality benchmarks (Phase 1B) and the LWR/Pu recycling benchmarks. These calculations were performed by WIMSD-5B with the 69-group libraries prepared from three evaluated nuclear data libraries: ENDF/B-VI.7, ENDF/B-VI.8 including the new evaluations in the resonance region covering the thermal region, and the expected ENDF/B-VII including those in the upper resonance region up to 20 MeV. For Xe-131, the composition calculated with ENDF/B-VI.8 shows a maximum difference of 5.02% compared to ENDF/B-VI.7. However, the isotopic compositions of all the fission products calculated with the expected ENDF/B-VII show no differences when compared to ENDF/B-VI.7 for the thermal reactor benchmark cases.
The fusion-fission process in the reaction {sup 34}S+{sup 186}W near the interaction barrier
Energy Technology Data Exchange (ETDEWEB)
Harca, I. M. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, (FLNR JINR) Dubna, Russia and Faculty of Physics, University of Bucharest - P.O. Box MG 11, RO 77125, Bucharest-Magurele (Romania); Dmitriev, S.; Itkis, J.; Kozulin, E. M.; Knyazheva, G.; Loktev, T.; Novikov, K. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, (FLNR JINR) Dubna (Russian Federation); Azaiez, F.; Gottardo, A.; Matea, I.; Verney, D. [IPN, CNRS/IN2P3, Univ. Paris-Sud, 91405 Orsay (France); Chubarian, G. [Cyclotron Institute, Texas A and M University, College Station, TX 77843-3366 (United States); Hanappe, F. [Universite Libre de Bruxelles (ULB), Bruxelles (Belgium); Piot, J.; Schmitt, C. [GANIL, CEA/DSM-CNRS/IN2P3, Bd Henri Becquerel, BP 55027, F-14076 Caen Cedex 5 (France); Trzaska, W. H. [Accelerator Laboratory of University of Jyväskylä (JYFL), Jyväskylä (Finland); Vardaci, E. [Dipartamento di Scienze Fisiche and INFN (INFN-Na), Napoli (Italy)
2015-02-24
The reaction {sup 34}S+{sup 186}W at E{sub lab}=160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF–γ coincidence method is of better use then the γ – γ coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.
Archie, Elizabeth A.; Moss, Cynthia J; Alberts, Susan C.
2005-01-01
Many social animals live in stable groups. In contrast, African savannah elephants (Loxodonta africana) live in unusually fluid, fission–fusion societies. That is, ‘core’ social groups are composed of predictable sets of individuals; however, over the course of hours or days, these groups may temporarily divide and reunite, or they may fuse with other social groups to form much larger social units. Here, we test the hypothesis that genetic relatedness predicts patterns of group fission and fu...
Energy Technology Data Exchange (ETDEWEB)
Kramer, K J; Latkowski, J F; Abbott, R P; Boyd, J K; Powers, J J; Seifried, J E
2008-10-24
Lawrence Livermore National Laboratory is currently developing a hybrid fusion-fission nuclear energy system, called LIFE, to generate power and burn nuclear waste. We utilize inertial confinement fusion to drive a subcritical fission blanket surrounding the fusion chamber. It is composed of TRISO-based fuel cooled by the molten salt flibe. Low-yield (37.5 MJ) targets and a repetition rate of 13.3 Hz produce a 500 MW fusion source that is coupled to the subcritical blanket, which provides an additional gain of 4-8, depending on the fuel. In the present work, we describe the neutron transport and nuclear burnup analysis. We utilize standard analysis tools including, the Monte Carlo N-Particle (MCNP) transport code, ORIGEN2 and Monteburns to perform the nuclear design. These analyses focus primarily on a fuel composed of depleted uranium not requiring chemical reprocessing or enrichment. However, other fuels such as weapons grade plutonium and highly-enriched uranium are also under consideration. In addition, we have developed a methodology using {sup 6}Li as a burnable poison to replace the tritium burned in the fusion targets and to maintain constant power over the lifetime of the engine. The results from depleted uranium analyses suggest up to 99% burnup of actinides is attainable while maintaining full power at 2GW for more than five decades.
Teh, Boon Kin; Cheong, Siew Ann
2016-01-01
The Global Financial Crisis of 2007-2008 wiped out US$37 trillions across global financial markets, this value is equivalent to the combined GDPs of the United States and the European Union in 2014. The defining moment of this crisis was the failure of Lehman Brothers, which precipitated the October 2008 crash and the Asian Correction (March 2009). Had the Federal Reserve seen these crashes coming, they might have bailed out Lehman Brothers, and prevented the crashes altogether. In this paper, we show that some of these market crashes (like the Asian Correction) can be predicted, if we assume that a large number of adaptive traders employing competing trading strategies. As the number of adherents for some strategies grow, others decline in the constantly changing strategy space. When a strategy group grows into a giant component, trader actions become increasingly correlated and this is reflected in the stock price. The fragmentation of this giant component will leads to a market crash. In this paper, we also derived the mean-field market crash forecast equation based on a model of fusions and fissions in the trading strategy space. By fitting the continuous returns of 20 stocks traded in Singapore Exchange to the market crash forecast equation, we obtain crash predictions ranging from end October 2008 to mid-February 2009, with early warning four to six months prior to the crashes. PMID:27706198
Energy Technology Data Exchange (ETDEWEB)
Braffort, P.; Chaigne, M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1958-07-01
1) Introduction: The difficulties of the formulation of the equations of phenomena occurring during the operation of a fusion reactor are underlined. 2) The possibilities presented by analog computation of the solution of nonlinear differential equations are enumerated. The accuracy and limitations of this method are discussed. 3) The analog solution in the stationary problem of the measurement of the discharge confinement is given and comparison with experimental results. 4) The analog solution of the dynamic problem of the evolution of the discharge current in a simple case is given and it is compared with experimental data. 5) The analog solution of the motion of an isolated ion in the electromagnetic field is given. A spatial field simulator used for this problem (bidimensional problem) is described. 6) The analog solution of the preceding problem for a tridimensional case for particular geometrical configurations using simultaneously 2 field simulators is given. 7) A method of computation derived from Monte Carlo method for the study of dynamic of plasma is described. 8) Conclusion: the essential differences between the analog computation of fission reactors and fusion reactors are analysed. In particular the theory of control of a fusion reactor as described by SCHULTZ is discussed and the results of linearized formulations are compared with those of nonlinear simulation. (author)Fren. [French] 1) Introduction. On souligne les difficultes que presente la mise en equation des phenomenes mis en jeu lors du fonctionnement d'un reacteur a fusion. On selectionne un certain nombre d'equations generalement utilisees et on montre les impossibilites analytiques auxquelles on se heurte alors. 2) On rappelle les possibilites du calcul analogique pour la resolution des systemes differentiels non lineaires et on indique la precision de la methode ainsi que ses limitations. 3) On decrit esolution analogique du probleme statique de la mesure du confinement de la
Barber, Duncan Henry
During some postulated accidents at nuclear power stations, fuel cooling may be impaired. In such cases, the fuel heats up and the subsequent increased fission-gas release from the fuel to the gap may result in fuel sheath failure. After fuel sheath failure, the barrier between the coolant and the fuel pellets is lost or impaired, gases and vapours from the fuel-to-sheath gap and other open voids in the fuel pellets can be vented. Gases and steam from the coolant can enter the broken fuel sheath and interact with the fuel pellet surfaces and the fission-product inclusion on the fuel surface (including material at the surface of the fuel matrix). The chemistry of this interaction is an important mechanism to model in order to assess fission-product releases from fuel. Starting in 1995, the computer program SOURCE 2.0 was developed by the Canadian nuclear industry to model fission-product release from fuel during such accidents. SOURCE 2.0 has employed an early thermochemical model of irradiated uranium dioxide fuel developed at the Royal Military College of Canada. To overcome the limitations of computers of that time, the implementation of the RMC model employed lookup tables to pre-calculated equilibrium conditions. In the intervening years, the RMC model has been improved, the power of computers has increased significantly, and thermodynamic subroutine libraries have become available. This thesis is the result of extensive work based on these three factors. A prototype computer program (referred to as SC11) has been developed that uses a thermodynamic subroutine library to calculate thermodynamic equilibria using Gibbs energy minimization. The Gibbs energy minimization requires the system temperature (T) and pressure (P), and the inventory of chemical elements (n) in the system. In order to calculate the inventory of chemical elements in the fuel, the list of nuclides and nuclear isomers modelled in SC11 had to be expanded from the list used by SOURCE 2.0. A
Energy Technology Data Exchange (ETDEWEB)
Farmer, J C; Diaz de la Rubia, T; Moses, E
2008-12-23
The National Ignition Facility (NIF) project, a laser-based Inertial Confinement Fusion (ICF) experiment designed to achieve thermonuclear fusion ignition and burn in the laboratory, is under construction at the Lawrence Livermore National Laboratory (LLNL) and will be completed in April of 2009. Experiments designed to accomplish the NIF's goal will commence in late FY2010 utilizing laser energies of 1 to 1.3 MJ. Fusion yields of the order of 10 to 20 MJ are expected soon thereafter. Laser initiated fusion-fission (LIFE) engines have now been designed to produce nuclear power from natural or depleted uranium without isotopic enrichment, and from spent nuclear fuel from light water reactors without chemical separation into weapons-attractive actinide streams. A point-source of high-energy neutrons produced by laser-generated, thermonuclear fusion within a target is used to achieve ultra-deep burn-up of the fertile or fissile fuel in a sub-critical fission blanket. Fertile fuels including depleted uranium (DU), natural uranium (NatU), spent nuclear fuel (SNF), and thorium (Th) can be used. Fissile fuels such as low-enrichment uranium (LEU), excess weapons plutonium (WG-Pu), and excess highly-enriched uranium (HEU) may be used as well. Based upon preliminary analyses, it is believed that LIFE could help meet worldwide electricity needs in a safe and sustainable manner, while drastically shrinking the nation's and world's stockpile of spent nuclear fuel and excess weapons materials. LIFE takes advantage of the significant advances in laser-based inertial confinement fusion that are taking place at the NIF at LLNL where it is expected that thermonuclear ignition will be achieved in the 2010-2011 timeframe. Starting from as little as 300 to 500 MW of fusion power, a single LIFE engine will be able to generate 2000 to 3000 MWt in steady state for periods of years to decades, depending on the nuclear fuel and engine configuration. Because the fission
Neutron and photon transport calculations in fusion system. 2
Energy Technology Data Exchange (ETDEWEB)
Sato, Satoshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment
1998-03-01
On the application of MCNP to the neutron and {gamma}-ray transport calculations for fusion reactor system, the wide range design calculation has been carried out in the engineering design activities for the international thermonuclear fusion experimental reactor (ITER) being developed jointly by Japan, USA, EU and Russia. As the objects of shielding calculation for fusion reactors, there are the assessment of dose equivalent rate for living body shielding and the assessment of the nuclear response for the soundness of in-core structures. In the case that the detailed analysis of complicated three-dimensional shapes is required, the assessment using MCNP has been carried out. Also when the nuclear response of peripheral equipment due to the gap streaming between blanket modules is evaluated with good accuracy, the calculation with MCNP has been carried out. The analyses of the shieldings for blanket modules and NBI port are explained, and the examples of the results of analyses are shown. In the blanket modules, there are penetrating holes and continuous gap. In the case of the NBI port, shielding plug cannot be installed. These facts necessitate the MCNP analysis with high accuracy. (K.I.)
New Global Calculation of Nuclear Masses and Fission Barriers for Astrophysical Applications
Möller, P.; Sierk, A. J.; Bengtsson, R.; Ichikawa, T.; Iwamoto, A.
2008-05-01
The FRDM(1992) mass model [1] has an accuracy of 0.669 MeV in the region where its parameters were determined. For the 529 masses that have been measured since, its accuracy is 0.46 MeV, which is encouraging for applications far from stability in astrophysics. We are developing an improved mass model, the FRDM(2008). The improvements in the calculations with respect to the FRDM(1992) are in two main areas. (1) The macroscopic model parameters are better optimized. By simulation (adjusting to a limited set of now known nuclei) we can show that this actually makes the results more reliable in new regions of nuclei. (2) The ground-state deformation parameters are more accurately calculated. We minimize the energy in a four-dimensional deformation space (ɛ2, V3, V4, V6,) using a grid interval of 0.01 in all 4 deformation variables. The (non-finalized) FRDM (2008-a) has an accuracy of 0.596 MeV with respect to the 2003 Audi mass evaluation before triaxial shape degrees of freedom are included (in progress). When triaxiality effects are incorporated preliminary results indicate that the model accuracy will improve further, to about 0.586 MeV. We also discuss very large-scale fission-barrier calculations in the related FRLDM (2002) model, which has been shown to reproduce very satisfactorily known fission properties, for example barrier heights from 70Se to the heaviest elements, multiple fission modes in the Ra region, asymmetry of mass division in fission and the triple-humped structure found in light actinides. In the superheavy region we find barriers consistent with the observed half-lives. We have completed production calculations and obtain barrier heights for 5254 nuclei heavier than A = 170 for all nuclei between the proton and neutron drip lines. The energy is calculated for 5009325 different shapes for each nucleus and the optimum barrier between ground state and separated fragments is determined by use of an ``immersion'' technique.
Calculation for fission decay from heavy ion reactions at intermediate energies
Energy Technology Data Exchange (ETDEWEB)
Blaich, T.; Begemann-Blaich, M.; Fowler, M.M.; Wilhelmy, J.B. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)); Britt, H.C.; Fields, D.J.; Hansen, L.F.; Namboodiri, M.N.; Sangster, T.C. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)); Fraenkel, Z. (Weizmann Institute of Science, 76100 Rehovot (Israel))
1992-02-01
A detailed deexcitation calculation is presented for target residues resulting from intermediate-energy heavy ion reactions. The model involves an intranuclear cascade, subsequent fast nucleon emission, and final decay by statistical evaporation including fission. Results are compared to data from bombardments with Fe and Nb projectiles on targets of Ta, Au, and Th at 100 MeV/nucleon. The majority of observable features are reproduced with this simple approach, making obvious the need for involving new physical phenomena associated with multifragmentation or other collective dissipation mechanisms.
Delayed neutron spectra and their uncertainties in fission product summation calculations
Energy Technology Data Exchange (ETDEWEB)
Miyazono, T.; Sagisaka, M.; Ohta, H.; Oyamatsu, K.; Tamaki, M. [Nagoya Univ. (Japan)
1997-03-01
Uncertainties in delayed neutron summation calculations are evaluated with ENDF/B-VI for 50 fissioning systems. As the first step, uncertainty calculations are performed for the aggregate delayed neutron activity with the same approximate method as proposed previously for the decay heat uncertainty analyses. Typical uncertainty values are about 6-14% for {sup 238}U(F) and about 13-23% for {sup 243}Am(F) at cooling times 0.1-100 (s). These values are typically 2-3 times larger than those in decay heat at the same cooling times. For aggregate delayed neutron spectra, the uncertainties would be larger than those for the delayed neutron activity because much more information about the nuclear structure is still necessary. (author)
Core Physics and Kinetics Calculations for the Fissioning Plasma Core Reactor
Butler, C.; Albright, D.
2007-01-01
Highly efficient, compact nuclear reactors would provide high specific impulse spacecraft propulsion. This analysis and numerical simulation effort has focused on the technical feasibility issues related to the nuclear design characteristics of a novel reactor design. The Fissioning Plasma Core Reactor (FPCR) is a shockwave-driven gaseous-core nuclear reactor, which uses Magneto Hydrodynamic effects to generate electric power to be used for propulsion. The nuclear design of the system depends on two major calculations: core physics calculations and kinetics calculations. Presently, core physics calculations have concentrated on the use of the MCNP4C code. However, initial results from other codes such as COMBINE/VENTURE and SCALE4a. are also shown. Several significant modifications were made to the ISR-developed QCALC1 kinetics analysis code. These modifications include testing the state of the core materials, an improvement to the calculation of the material properties of the core, the addition of an adiabatic core temperature model and improvement of the first order reactivity correction model. The accuracy of these modifications has been verified, and the accuracy of the point-core kinetics model used by the QCALC1 code has also been validated. Previously calculated kinetics results for the FPCR were described in the ISR report, "QCALC1: A code for FPCR Kinetics Model Feasibility Analysis" dated June 1, 2002.
Winterberg, Friedwardt
2009-01-01
The recently proposed Super Marx generator pure deuterium micro-detonation ignition concept is compared to the Lawrence Livermore National Ignition Facility (NIF) Laser DT fusion-fission hybrid concept (LiFE) [1]. In a Super Marx generator a large number of ordinary Marx generators charge up a much larger second stage ultra-high voltage Marx generator, from which for the ignition of a pure deuterium micro-explosion an intense GeV ion beam can be extracted. A typical example of the LiFE concept is a fusion gain of 30, and a fission gain of 10, making up for a total gain of 300, with about 10 times more energy released into fission as compared to fusion. This means a substantial release of fission products, as in fusion-less pure fission reactors. In the Super Marx approach for the ignition of a pure deuterium micro-detonation a gain of the same magnitude can in theory be reached [2]. If feasible, the Super Marx generator deuterium ignition approach would make lasers obsolete as a means for the ignition of ther...
Directory of Open Access Journals (Sweden)
Porta A.
2016-01-01
Full Text Available Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. 92,93Rb are two fission products of importance in reactor antineutrino spectra and decay heat, but their β-decay properties are not well known. New measurements of 92,93Rb β-decay properties have been performed at the IGISOL facility (Jyväskylä, Finland using Total Absorption Spectroscopy (TAS. TAS is complementary to techniques based on Germanium detectors. It implies the use of a calorimeter to measure the total gamma intensity de-exciting each level in the daughter nucleus providing a direct measurement of the beta feeding. In these proceedings we present preliminary results for 93Rb, our measured beta feedings for 92Rb and we show the impact of these results on reactor antineutrino spectra and decay heat calculations.
Density functional theory calculations of defect and fission gas properties in U-Si fuels
Energy Technology Data Exchange (ETDEWEB)
Andersson, Anders David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-02-03
Accident tolerant fuels (ATF) are being developed in response to the Fukushima Daiichi accident in Japan. One of the options being pursued is U-Si fuels, such as the U_{3}Si_{2} and U_{3}Si_{5} compounds, which benefit from high thermal conductivity (metallic) compared to the UO_{2} fuel (insulator or semi-conductor) used in current Light Water Reactors (LWRs). The U-Si fuels also have higher fissile density. In order to perform meaningful engineering scale nuclear fuel performance simulations, the material properties of the fuel, including the response to irradiation environments, must be known. Unfortunately, the data available for U-Si fuels are rather limited, in particular for the temperature range where LWRs would operate. The ATF HIP is using multi-scale modeling and simulations to address this knowledge gap. The present study investigates point defect and fission gas properties in U_{3}Si_{2}, which is one of the main fuel candidates, using density functional theory (DFT) calculations. Based on a few assumption regarding entropy contributions, defect and fission diffusivities are predicted. Even though uranium silicides have been shown to amorphize easily at low temperature, we assume that U_{3}Si_{2} remains crystalline under the conditions expected in Light Water Reactors (LWRs). The temperature and dose where amorphization occurs has not yet been well established.
Porta, A.; Zakari-Issoufou, A.-A.; Fallot, M.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; Estienne, M.; Agramunt, J.; Äystö, J.; Bowry, M.; Briz, J. A.; Caballero-Folch, R.; Cano-Ott, D.; Cucouanes, A.; Elomaa, V.-V.; Eronen, T.; Estévez, E.; Farrelly, G. F.; Garcia, A. R.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Karvonen, P.; Kolhinen, V. S.; Kondev, F. G.; Martinez, T.; Mendoza, E.; Molina, F.; Moore, I.; Perez-Cerdán, A. B.; Podolyák, Zs.; Penttilä, H.; Regan, P. H.; Reponen, M.; Rissanen, J.; Rubio, B.; Shiba, T.; Sonzogni, A. A.; Weber, C.
2016-03-01
Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. 92,93Rb are two fission products of importance in reactor antineutrino spectra and decay heat, but their β-decay properties are not well known. New measurements of 92,93Rb β-decay properties have been performed at the IGISOL facility (Jyväskylä, Finland) using Total Absorption Spectroscopy (TAS). TAS is complementary to techniques based on Germanium detectors. It implies the use of a calorimeter to measure the total gamma intensity de-exciting each level in the daughter nucleus providing a direct measurement of the beta feeding. In these proceedings we present preliminary results for 93Rb, our measured beta feedings for 92Rb and we show the impact of these results on reactor antineutrino spectra and decay heat calculations.
Energy Technology Data Exchange (ETDEWEB)
Farmer, J C; Diaz de la Rubia, T; Moses, E
2008-12-23
The National Ignition Facility (NIF) project, a laser-based Inertial Confinement Fusion (ICF) experiment designed to achieve thermonuclear fusion ignition and burn in the laboratory, is under construction at the Lawrence Livermore National Laboratory (LLNL) and will be completed in April of 2009. Experiments designed to accomplish the NIF's goal will commence in late FY2010 utilizing laser energies of 1 to 1.3 MJ. Fusion yields of the order of 10 to 20 MJ are expected soon thereafter. Laser initiated fusion-fission (LIFE) engines have now been designed to produce nuclear power from natural or depleted uranium without isotopic enrichment, and from spent nuclear fuel from light water reactors without chemical separation into weapons-attractive actinide streams. A point-source of high-energy neutrons produced by laser-generated, thermonuclear fusion within a target is used to achieve ultra-deep burn-up of the fertile or fissile fuel in a sub-critical fission blanket. Fertile fuels including depleted uranium (DU), natural uranium (NatU), spent nuclear fuel (SNF), and thorium (Th) can be used. Fissile fuels such as low-enrichment uranium (LEU), excess weapons plutonium (WG-Pu), and excess highly-enriched uranium (HEU) may be used as well. Based upon preliminary analyses, it is believed that LIFE could help meet worldwide electricity needs in a safe and sustainable manner, while drastically shrinking the nation's and world's stockpile of spent nuclear fuel and excess weapons materials. LIFE takes advantage of the significant advances in laser-based inertial confinement fusion that are taking place at the NIF at LLNL where it is expected that thermonuclear ignition will be achieved in the 2010-2011 timeframe. Starting from as little as 300 to 500 MW of fusion power, a single LIFE engine will be able to generate 2000 to 3000 MWt in steady state for periods of years to decades, depending on the nuclear fuel and engine configuration. Because the fission
Energy Technology Data Exchange (ETDEWEB)
Jo, Yu Gwon; Cho, Nam Zin [KAIST, Daejeon (Korea, Republic of)
2014-10-15
The OLG iteration scheme uses overlapping regions for each local problem solved by continuous-energy MC calculation to reduce errors in inaccurate boundary conditions (BCs) that are caused by discretization in space, energy, and angle. However, the overlapping region increases computational burdens and the discretized BCs for continuous-energy MC calculation result in an inaccurate global p-CMFD solution. On the other hand, there also have been several studies on the direct domain decomposed MC calculation where each processor simulates particles within its own domain and exchanges the particles crossing the domain boundary between processors with certain frequency. The efficiency of this method depends on the message checking frequency and the buffer size. Furthermore, it should overcome the load-imbalance problem for better parallel efficiency. Recently, fission and surface source (FSS) iteration method based on banking both fission and surface sources for the next iteration (i.e., cycle) was proposed to give exact BCs for non overlapping local problems in domain decomposition and tested in one-dimensional continuous-energy reactor problems. In this paper, the FSS iteration method is combined with a source splitting scheme to reduce the load imbalance problem and achieve global variance reduction. The performances are tested on a two dimensional continuous-energy reactor problem with domain-based parallelism and compared with the FSS iteration without source splitting. Numerical results show the improvements of the FSS iteration with source splitting. This paper describes the FSS iteration scheme in the domain decomposition method and proposes the FSS iteration combined with the source splitting based on the number of sampled sources, reducing the load-imbalance problem in domain-based parallelism and achieving global variance reduction.
Smith, A.; Siegel, Edward Carl-Ludwig
2011-03-01
Numbers: primality/indivisibility/non-factorization versus compositeness/divisibility/ factorization, often in tandem but not always, provocatively close analogy to nuclear-physics: (2 + 1)=(fusion)=3; (3+1)=(fission)=4[=2 x 2]; (4+1)=(fusion)=5; (5 +1)=(fission)=6[=2 x 3]; (6 + 1)=(fusion)=7; (7+1)=(fission)=8[= 2 x 4 = 2 x 2 x 2]; (8 + 1) =(non: fission nor fusion)= 9[=3 x 3]; then ONLY composites' Islands of fusion-INstability: 8, 9, 10; then 14, 15, 16, ... Could inter-digit Feshbach-resonances exist??? Possible applications to: quantum-information/ computing non-Shore factorization, millennium-problem Riemann-hypotheses proof as Goodkin BEC intersection with graph-theory "short-cut" method: Rayleigh(1870)-Polya(1922)-"Anderson"(1958)-localization, Goldbach-conjecture, financial auditing/accounting as quantum-statistical-physics; ...abound!!! Watkins [www.secamlocal.ex.ac.uk/people/staff/mrwatkin/] "Number-Theory in Physics" many interconnections: "pure"-maths number-theory to physics including Siegel [AMS Joint Mtg.(2002)-Abs.# 973-60-124] inversion of statistics on-average digits' Newcomb(1881)-Weyl(14-16)-Benford(38)-law to reveal both the quantum and BEQS (digits = bosons = digits:"spinEless-boZos"). 1881 1885 1901 1905 1925 < 1927, altering quantum-theory history!!!
Calculation of 239Pu fission observables in an event-by-event simulation
Energy Technology Data Exchange (ETDEWEB)
Vogt, R; Randrup, J; Pruet, J; Younes, W
2010-03-31
The increased interest in more exclusive fission observables has demanded more detailed models. We describe a new computational model, FREYA, that aims to meet this need by producing large samples of complete fission events from which any observable of interest can then be extracted consistently, including any interesting correlations. The various model assumptions are described and the potential utility of the model is illustrated. As a concrete example, we use formal statistical methods, experimental data on neutron production in neutron-induced fission of {sup 239}Pu, along with FREYA, to develop quantitative insights into the relation between reaction observables and detailed microscopic aspects of fission. Current measurements of the mean number of prompt neutrons emitted in fission taken together with less accurate current measurements for the prompt post-fission neutron energy spectrum, up to the threshold for multi-chance fission, place remarkably fine constraints on microscopic theories.
Energy Technology Data Exchange (ETDEWEB)
Qi, J.M., E-mail: qjm06@sina.com [Laboratory of Advanced Nuclear Energy (LANE), Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999 (China); Center for Fusion Energy Science and Technology (CFEST), China Academy of Engineering Physics, Mianyang 621999 (China); Wang, Z., E-mail: wangz_es@caep.cn [Laboratory of Advanced Nuclear Energy (LANE), Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999 (China); Center for Fusion Energy Science and Technology (CFEST), China Academy of Engineering Physics, Mianyang 621999 (China); Chu, Y.Y., E-mail: chuyanyun@caep.cn [Laboratory of Advanced Nuclear Energy (LANE), Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999 (China); Center for Fusion Energy Science and Technology (CFEST), China Academy of Engineering Physics, Mianyang 621999 (China); Li, Z.H., E-mail: lee_march@sina.com [Laboratory of Advanced Nuclear Energy (LANE), Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999 (China)
2016-03-15
Highlights: • Z-FFR utilizes DT neutrons to drive a sub-critical fission blanket to produce energy. • A metal shell and Ar gas are employed in the fusion chamber for shock mitigation. • Massive materials can effectively mitigate the thermal heats on the chamber wall. • The W-coated Zr-alloy first wall exhibits good viability as a long-lived component. - Abstract: In a Z-pinch driven fusion–fission hybrid power reactor (Z-FFR), the fusion target will produce enormous energy of ∼1.5 GJ per pulse at a frequency of 0.1 Hz. Almost 20% of the fusion energy yield, approximately 300 MJ, is released in forms of pulsed X-rays. To prevent the first wall from fatal damages by the intense X-rays, a thin spherical metal shell and rare Ar buffer gas are introduced to mitigate the transient X-ray bursts. Radiation hydrodynamics in the fusion chamber were investigated by MULTI-1D simulations, and the corresponding thermal and mechanical loads on the first wall were also obtained. The simulations indicated that by optimizing the design parameters of the metal shell and Ar buffer gas, peak power flux of the thermal heats on the first wall could be mitigated to less than 10{sup 4} W/cm{sup 2} within a time scale of several milliseconds, while peak overpressures of the mechanical loads varying from 0.6 to 0.7 MPa. In addition, the thermomechanical response in a W–coated Zr-alloy first wall was performed by FWDR1D calculations using the derived thermal and mechanical loads as inputs. The temperature and stress fields were analyzed, and the corresponding elastic strains were conducted for primary lifetime estimations by using the Coffin–Manson relationships of both W and Zr-alloy. It was shown that the maximum temperature rises and stresses in the first wall were less than 50 K and 130 MPa respectively, and lifetime of the first wall would be in excess of 10{sup 9} cycles. The chamber exhibits good viability as a long-lived component to sustain the Z-FFR conceptual
Variational RRKM calculation of thermal rate constant for C–H bond fission reaction of nitro methane
Directory of Open Access Journals (Sweden)
Afshin Taghva Manesh
2017-02-01
Full Text Available The present work provides quantitative results for the rate constants of unimolecular C–H bond fission reactions in the nitro methane at elevated temperatures up to 2000 K. In fact, there are three different hydrogen atoms in the nitro methane. The potential energy surface for each C–H bond fission reaction of nitro methane was investigated by ab initio calculations. The geometry and vibrational frequencies of the species involved in this process were optimized at the MP2 level of theory, using the cc-pvdz basis set. Since C–H bond fission channel is a barrierless reaction, we have used variational RRKM theory to predict rate coefficients. By means of calculated rate coefficients at different temperatures, the Arrhenius expression of the channel over the temperature range of 100–2000 K is k(T = 5.9E19∗exp(−56274.6/T.
Spontaneous telomere to telomere fusions occur in unperturbed fission yeast cells
Almeida, H.; Godinho Ferreira, M.
2013-01-01
Telomeres protect eukaryotic chromosomes from illegitimate end-to-end fusions. When this function fails, dicentric chromosomes are formed, triggering breakage-fusion-bridge cycles and genome instability. How efficient is this protection mechanism in normal cells is not fully understood. We created a positive selection assay aimed at capturing chromosome-end fusions in Schizosaccharomyces pombe. We placed telomere sequences with a head to head arrangement in an intron of a selectable marker co...
Kashatus, David F
2016-09-15
In this issue of Molecular Cell, Adachi et al. (2016) describe a novel interaction between the mitochondrial fission GTPase Drp1 and phosphatidic acid that restrains Drp1 activity and shifts the balance toward mitochondrial fusion, adding another layer of complexity to the regulation of mitochondrial dynamics.
Energy Technology Data Exchange (ETDEWEB)
Gerasimenko, B.F. [V.G. Khlopin Radium Inst., Saint Peterburg (Russian Federation)
1997-03-01
The calculations of integral spectra of prompt neutrons of spontaneous fission of {sup 244}Cm and {sup 246}Cm were carried out. The calculations were done by the Statistical Computer Code Complex SCOFIN applying the Hauser-Feschbach method as applied to the description of the de-excitation of excited fission fragments by means of neutron emission. The emission of dipole gamma-quanta from these fragments was considered as a competing process. The average excitation energy of a fragment was calculated by two-spheroidal model of tangent fragments. The density of levels in an excited fragment was calculated by the Fermi-gas model. The quite satisfactory agreement was reached between theoretical and experimental results obtained in frames of Project measurements. The calculated values of average multiplicities of neutron number were 2,746 for {sup 244}Cm and 2,927 for {sup 246}Cm that was in a good accordance with published experimental figures. (author)
Fission and Fusion of Solitons for the (1+1)-Dimensional Kupershmidt Equation
Institute of Scientific and Technical Information of China (English)
YING Jin-Ping
2001-01-01
By means of the heat conduction equation and the standard truncated Painlevé expansion, the (1+1) dimensional Kupershmidt equation is solved. Some significant exact multi-soliton solutions are given. Especially; for the interaction of the multi-solitons of the Kupershmidt equation, we find that a single (resonant) kink or bell soliton may be fissioned to several kink or bell solitons. Inversely, several kink or bell solitons may also be fused to one kink or bell soliton.
Díaz-Torres, A
2006-01-01
A realistic microscopically-based quantum approach to the competition between fusion and quasi-fission in a heavy fusing system is applied to several reactions leading to $^{256}$No. Fusion and quasi-fission are described in terms of a diffusion process of nuclear shapes through a dynamical collective potential energy landscape which is initially diabatic and gradually becomes adiabatic. The microscopic ingredients of the theory are obtained with a realistic two-center shell model based on Woods-Saxon potentials. The results indicate that (i) the diabatic effects play a very important role in the onset of fusion hindrance for heavy systems, and (ii) very asymmetric reactions induced by closed shell nuclei seem to be the best suited to synthesize the heaviest compound nuclei.
Energy Technology Data Exchange (ETDEWEB)
None
2009-09-30
Largely in anticipation of a possible nuclear renaissance, there has been an enthusiastic renewal of interest in the fusion-fission hybrid concept, driven primarily by some members of the fusion community. A fusion-fission hybrid consists of a neutron-producing fusion core surrounded by a fission blanket. Hybrids are of interest because of their potential to address the main long-term sustainability issues related to nuclear power: fuel supply, energy production, and waste management. As a result of this renewed interest, the U.S. Department of Energy (DOE), with the participation of the Office of Fusion Energy Sciences (OFES), Office of Nuclear Energy (NE), and National Nuclear Security Administration (NNSA), organized a three-day workshop in Gaithersburg, Maryland, from September 30 through October 2, 2009. Participants identified several goals. At the highest level, it was recognized that DOE does not currently support any R&D in the area of fusion-fission hybrids. The question to be addressed was whether or not hybrids offer sufficient promise to motivate DOE to initiate an R&D program in this area. At the next level, the workshop participants were asked to define the research needs and resources required to move the fusion-fission concept forward. The answer to the high-level question was given in two ways. On the one hand, when viewed as a standalone concept, the fusion-fission hybrid does indeed offer the promise of being able to address the sustainability issues associated with conventional nuclear power. On the other hand, when participants were asked whether these hybrid solutions are potentially more attractive than contemplated pure fission solutions (that is, fast burners and fast breeders), there was general consensus that this question could not be quantitatively answered based on the known technical information. Pure fission solutions are based largely on existing both fusion and nuclear technology, thereby prohibiting a fair side-by-side comparison
Directory of Open Access Journals (Sweden)
K. Nishio
2015-09-01
Full Text Available Mass distributions of fission fragments from the compound nuclei 180Hg and 190Hg formed in fusion reactions 36Ar + 144Sm and 36Ar + 154Sm, respectively, were measured at initial excitation energies of E⁎(Hg180=33–66 MeV and E⁎(Hg190=48–71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses A¯L/A¯H=79/101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+/EC-delayed fission of 180Tl, from our earlier ISOLDE(CERN experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of A¯L/A¯H=83/107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.
Energy Technology Data Exchange (ETDEWEB)
Tone, Tatsuzo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
2001-03-01
Overview of the historical evolution of nuclear energy systems development and related activities in JAERI is given in the report. This report reviews the research and development for light water reactor, fast breeder reactor, high temperature gas reactor, fusion reactor and utilization of accelerator-based neutron source. (author)
Study of fusion-fission dynamics in 19F+238U reaction
Directory of Open Access Journals (Sweden)
Dubey R.
2016-01-01
Full Text Available Mass angle distribution measurements for 19F+238U reaction were carried out around the sub barrier energies. Mass angle correlation has not been observed at above and below the fusion barrier in present reaction. This infer the minimal presence of non compound like events at these bombarding energies range.
Energy Technology Data Exchange (ETDEWEB)
Thirolf, P. G., E-mail: Peter.Thirolf@lmu.de [Ludwig-Maximilians-Universität München, Am Coulombwall 1, Garching (Germany)
2015-02-24
High-power, short pulse lasers have emerged in the last decade as attractive tools for accelerating charged particles (electrons, ions) to high energies over mm-scale acceleration lengths, thus promising to rival conventional acceleration techniques in the years ahead. In the first part of the article, the principles of laser-plasma interaction as well as the techniques and the current status of the acceleration of electron and ion beams will be briefly introduced. In particular with the upcoming next generation of multi-PW class laser systems, such as the one under construction for the ELI-Nuclear Physics project in Bucharest (ELI-NP), very efficient acceleration mechanisms for brilliant ion beams like radiation pressure acceleration (RPA) come into reach. Here, ultra-dense ion beams reaching solid-state density can be accelerated from thin target foils, exceeding the density of conventionally accelerated ion beams by about 14 orders of magnitude. This unique property of laser-accelerated ion beams can be exploited to explore the scenario of a new reaction mechanism called ‘fission-fusion’, which will be introduced in the second part of the article. Accelerating fissile species (e.g. {sup 232}Th) towards a second layer of the same material will lead to fission both of the beam-like and target-like particles. Due to the close to solid-state density of the accelerated ion bunches, fusion may occur between neutron-rich (light) fission products. This may open an access path towards extremely neutron-rich nuclides in the vicinity of the N=126 waiting point of the astrophysical r process. ‘Waiting points’ at closed nucleon shells play a crucial role in controlling the reaction rates. However, since most of the pathway of heavy-element formation via the rapid-neutron capture process (r-process) runs in ‘terra incognita’ of the nuclear landscape, in particular the waiting point at N=126 is yet unexplored and will remain largely inaccessible to conventional
Zamponi, Nahuel; Billoni, Orlando V; Cannas, Sergio A; Helguera, Pablo R; Chialvo, Dante R
2016-01-01
Mitochondrial networks have been shown to exhibit a variety of complex behaviors, including cell-wide oscillations of mitochondrial energy states, as well as a phase transition in response to oxidative stress. Since functional status and structural properties are often intertwined, in this work we look at the structural properties of the organelle in normal mouse embryonic fibroblasts, describing its most relevant features. Subsequently we manipulated mitochondrial morphology using two interventions with opposite effects: over-expression of mitofusin 1, a protein that promotes mitochondria fusion, and paraquat treatment, a compound that induces mitochondrial fragmentation due to oxidative stress. Quantitative analysis of the organelle's structural clusters revealed that healthy mitochondrial networks were in a status intermediate between the extremes of highly fragmented and completely fusioned networks. This was confirmed by a comparison of our empirical findings with those of a recently described computatio...
UW MCNP source patch for the EPFL Haefely source. EPFL (Swiss) fusion-fission hybrid experiment
Energy Technology Data Exchange (ETDEWEB)
McKinney, G; Woodruff, G L
1986-06-01
The development of a source patch which describes the Haefely neutron source for use in the MCNP Monte Carlo code has been described in progress reports of the EPFL (Swiss) Fusion Blanket Project at the University of Washington. The most recent of these reports dealing with the source patch was Progress Report No. 14. This report reviews some of the physical description included in the report, and also includes additional details of the patch as well as a listing of the patch itself.
Williams, J. R.
1974-01-01
Air pollution resulting from the use of fossil fuels is discussed. Phenomena relating to the emission of CO2 such as the greenhouse effect and multiplier effect are explored. Particulate release is also discussed. The following recommendations are made for the elimination of fossil fuel combustion products in the United States: development of nuclear breeder reactors, use of solar energy systems, exploration of energy alternatives such as geothermal and fusion, and the substitution of coal for gas and oil use.
Nanoscale interfaces in hybrid materials for exciton fission and fusion (Conference Presentation)
Bardeen, Christopher J.
2016-09-01
The ability to downconvert (1 photon to 2 photons) and upconvert (2 photons to 1 photon) energy can have applications in many fields, including solar energy. Singlet fission provides a way to convert one photon into a pair of triplet excitons. It occurs efficiently in organic semiconductors, but the question remains how to extract the triplet excitons in a useful form. In this talk, we will describe efforts to transform triplet excitons into other forms through energy transfer into inorganic semiconductors like silicon. Heterogeneous solid-liquid approaches to use spin-orbit coupling to enhance the triplet excitons' oscillator strength so they can emit photons will also be described. The solid-solid and solid-liquid interface appears to be critical for these schemes to succeed. Upconversion occurs via the reverse process, where a pair of triplet excitons fuse into a high-energy singlet state. A new approach to triplet state sensitization involves absorption of low energy photons by the semiconductor nanocrystals followed by energy transfer to the molecular triplet states. These states can then undergo triplet-triplet annihilation to create high energy singlet states that emit upconverted light in the visible and ultraviolet regions. By using conjugated organic ligands to form an energy cascade, the upconversion can be enhanced by up to three orders of magnitude. The mechanism of the nanocrystal-to-triplet energy transfer is investigated using time-resolved spectroscopy. Again, the role of organic ligand-inorganic surface interactions is important for determining the ultimate efficiency.
Main restrictions in the synthesis of new superheavy elements: quasifission or/and fusion-fission
Nasirov, Avazbek; Mandaglio, Giuseppe; Giardina, Giorgio; Muminov, Akhtam; Kim, Youngman
2013-01-01
The synthesis of superheavy elements stimulates the effort to study the peculiarities of the complete fusion with massive nuclei and to improve theoretical models in order to extract knowledge about reaction mechanism in heavy ion collisions at low energies. We compare the theoretical results of the compound nucleus (CN) formation and evaporation residue (ER) cross sections obtained for the $^{48}$Ca+$^{248}$Cm and $^{58}$Fe+$^{232}$Th reactions leading to the formation of the isotopes $A=296$ and $A=290$, respectively, of the new superheavy element Lv ($Z=116$). The ER cross sections, which can be measured directly, are determined by the complete fusion and survival probabilities of the heated and rotating compound nucleus. That probabilities can not be measured unambiguously but the knowledge about them is important to study the formation mechanism of the observed products. For this aim, the $^{48}$Ca+$^{249}$Cf and $^{64}$Ni+$^{232}$Th reactions have been considered too. The use of the mass values of super...
Fine-scale population genetic structure in a fission-fusion society.
Archie, Elizabeth A; Maldonado, Jésus E; Hollister-Smith, Julie A; Poole, Joyce H; Moss, Cynthia J; Fleischer, Robert C; Alberts, Susan C
2008-06-01
Nonrandom patterns of mating and dispersal create fine-scale genetic structure in natural populations - especially of social mammals - with important evolutionary and conservation genetic consequences. Such structure is well-characterized for typical mammalian societies; that is, societies where social group composition is stable, dispersal is male-biased, and males form permanent breeding associations in just one or a few social groups over the course of their lives. However, genetic structure is not well understood for social mammals that differ from this pattern, including elephants. In elephant societies, social groups fission and fuse, and males never form permanent breeding associations with female groups. Here, we combine 33 years of behavioural observations with genetic information for 545 African elephants (Loxodonta africana), to investigate how mating and dispersal behaviours structure genetic variation between social groups and across age classes. We found that, like most social mammals, female matrilocality in elephants creates co-ancestry within core social groups and significant genetic differentiation between groups (Phi(ST) = 0.058). However, unlike typical social mammals, male elephants do not bias reproduction towards a limited subset of social groups, and instead breed randomly across the population. As a result, reproductively dominant males mediate gene flow between core groups, which creates cohorts of similar-aged paternal relatives across the population. Because poaching tends to eliminate the oldest elephants from populations, illegal hunting and poaching are likely to erode fine-scale genetic structure. We discuss our results and their evolutionary and conservation genetic implications in the context of other social mammals.
Next generation laser optics for a hybrid fusion-fission power plant
Energy Technology Data Exchange (ETDEWEB)
Stolz, C J; Latkowski, J T; Schaffers, K I
2009-09-10
The successful completion of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL), followed by a campaign to achieve ignition, creates the proper conditions to begin exploring what development work remains to construct a power plant based on Inertial Confinement Fusion (ICF) technology. Fundamentally, two distinct NIF laser properties must be overcome. The repetition rate must increase from a shot every four hours to several shots per second. Additionally, the efficiency of converting electricity to laser light must increase by 20x to roughly 10 percent. Solid state diode pumped lasers, commercially available for table top applications, have adequate repetition rates and power conversion efficiencies, however, they operate at a tiny fraction of the required energy for an ICF power plant so would need to be scaled in energy and aperture. This paper describes the optics and coatings that would be needed to support this type of laser architecture.
A spallation-based irradiation test facility for fusion and future fission materials
Samec, K; Kadi, Y; Luis, R; Romanets, Y; Behzad, M; Aleksan, R; Bousson, S
2014-01-01
The EU’s FP7 TIARA program for developing accelerator-based facilities has recently demonstrated the unique capabilities of a compact and powerful spallation source for irradiating advanced nuclear materials. The spectrum and intensity of the neutron flux produced in the proposed facility fulfils the requirements of the DEMO fusion reactor for ITER, ADS reactors and also Gen III / IV reactors. Test conditions can be modulated, covering temperature from 400 to 550°C, liquid metal corrosion, cyclical or static stress up to 500 MPa and neutron/proton irradiation damage of up to 25 DPA per annum. The entire “TMIF” facility fits inside a cube 2 metres on a side, and is dimensioned for an accelerator beam power of 100 kW, thus reducing costs and offering great versatility and flexibility.
Quantum Calculation of Dipole Excitation in Fusion Reaction
2000-01-01
The excitation of the giant dipole resonance by fusion is studied with N/Z asymmetry in the entrance channel. the TDHF solution exhibits a strong dipole vibration which can be associated with a giant vibration along the main axis of a fluctuating prolate shape. The consequences on the gamma-ray emission from hot compound nuclei are discussed.
Decay heat measurement on fusion reactor materials and validation of calculation code system
Energy Technology Data Exchange (ETDEWEB)
Maekawa, Fujio; Ikeda, Yujiro; Wada, Masayuki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1998-03-01
Decay heat rates for 32 fusion reactor relevant materials irradiated with 14-MeV neutrons were measured for the cooling time period between 1 minute and 400 days. With using the experimental data base, validity of decay heat calculation systems for fusion reactors were investigated. (author)
Energy Technology Data Exchange (ETDEWEB)
NONE
2002-07-01
This series of 7 digest booklets present the bases of the nuclear physics and of the nuclear energy: 1 - the atom (structure of matter, chemical elements and isotopes, the four fundamental interactions, nuclear physics); 2 - radioactivity (definition, origins of radioelements, applications of radioactivity); 3 - man and radiations (radiations diversity, biological effects, radioprotection, examples of radiation applications); 4 - energy (energy states, different forms of energy, characteristics); 5 - nuclear energy: fusion and fission (nuclear energy release, thermonuclear fusion, nuclear fission and chain reaction); 6 - operation of a nuclear reactor (nuclear fission, reactor components, reactor types); 7 - nuclear fuel cycle (nuclear fuel preparation, fuel consumption, reprocessing, wastes management). (J.S.)
Energy Technology Data Exchange (ETDEWEB)
Cabrera, Carlos Eduardo Velasquez
2015-07-01
A fission-fusion hybrid reactor is proposed for recycling and transmutation of highly radioactive waste. Two fusion systems were evaluated. A Tokamak, based on magnetic confinement, and another based on inertial confinement. These systems have been modified and designed to place a transmutation layer loaded with transuranic elements from spent fuel of nuclear power plants. The transmutation layer is the first presented in specific literature to be used with fuel reprocessed by the method UREX + and further spiked with depleted uranium or thorium to reduce the amount of fissile material in order to keep a subcritical system. The evaluations were carried out by varying geometric parameters such as the thickness of transmutation layer and the radius of the fuel rod. Depending on the case this variations increase the efficiency to reduce the transuranic contained in the fuel. The results show the possibility of reducing the transuranic for each model and transmutation efficiency compared to the initial amount of recycled fuel for each fusion reactor. Furthermore, a comparison of both hybrid fusion-fission systems is performed in order to find the best system to reduce transuranics efficiently. (author)
Energy Technology Data Exchange (ETDEWEB)
Wilson, W. B. (William B.); Perry, R. T. (Robert T.); Shores, E. F. (Erik F.); Charlton, W. S. (William S.); Parish, Theodore A.; Estes, G. P. (Guy P.); Brown, T. H. (Thomas H.); Arthur, Edward D. (Edward Dana),; Bozoian, Michael; England, T. R.; Madland, D. G.; Stewart, J. E. (James E.)
2002-01-01
SOURCES 4C is a computer code that determines neutron production rates and spectra from ({alpha},n) reactions, spontaneous fission, and delayed neutron emission due to radionuclide decay. The code is capable of calculating ({alpha},n) source rates and spectra in four types of problems: homogeneous media (i.e., an intimate mixture of a-emitting source material and low-Z target material), two-region interface problems (i.e., a slab of {alpha}-emitting source material in contact with a slab of low-Z target material), three-region interface problems (i.e., a thin slab of low-Z target material sandwiched between {alpha}-emitting source material and low-Z target material), and ({alpha},n) reactions induced by a monoenergetic beam of {alpha}-particles incident on a slab of target material. Spontaneous fission spectra are calculated with evaluated half-life, spontaneous fission branching, and Watt spectrum parameters for 44 actinides. The ({alpha},n) spectra are calculated using an assumed isotropic angular distribution in the center-of-mass system with a library of 107 nuclide decay {alpha}-particle spectra, 24 sets of measured and/or evaluated ({alpha},n) cross sections and product nuclide level branching fractions, and functional {alpha}-particle stopping cross sections for Z < 106. The delayed neutron spectra are taken from an evaluated library of 105 precursors. The code provides the magnitude and spectra, if desired, of the resultant neutron source in addition to an analysis of the'contributions by each nuclide in the problem. LASTCALL, a graphical user interface, is included in the code package.
Zolezzi, Juan M.; Silva-Alvarez, Carmen; Ordenes, Daniela; Godoy, Juan A.; Carvajal, Francisco J.; Santos, Manuel J.; Inestrosa, Nibaldo C.
2013-01-01
Recent studies showed that the activation of the retinoid X receptor, which dimerizes with peroxisome proliferator-activated receptors (PPARs), leads to an enhanced clearance of Aβ from the brain of transgenic mice model of Alzheimer’s disease (AD), because an increased expression of apolipoprotein E and it main transporters. However, the effects observed must involve additional underlying mechanisms that have not been yet explored. Several studies conducted in our laboratory suggest that part of the effects observed for the PPARs agonist might involves mitochondrial function and, particularly, mitochondrial dynamics. In the present study we assessed the effects of oxidative stress challenge on mitochondrial morphology and mitochondrial dynamics-related proteins in hippocampal neurons. Using immunofluorescence, we evaluated the PPARγ co-activator 1α (PGC-1α), dynamin related protein 1 (DRP1), mitochondrial fission protein 1 (FIS1), and mitochondrial length, in order to determine if PPARs agonist pre-treatment is able to protect mitochondrial population from hippocampal neurons through modulation of the mitochondrial fusion-fission events. Our results suggest that both a PPARγ agonist (ciglitazone) and a PPARα agonist (WY 14.643) are able to protect neurons by modulating mitochondrial fusion and fission, leading to a better response of neurons to oxidative stress, suggesting that a PPAR based therapy could acts simultaneously in different cellular components. Additionally, our results suggest that PGC-1α and mitochondrial dynamics should be further studied in future therapy research oriented to ameliorate neurodegenerative disorders, such as AD. PMID:23675519
Energy Technology Data Exchange (ETDEWEB)
Barroso, Dalton Ellery Girao
2006-07-01
multiply ionized' atoms. The thermal radiation transport was performed by the flux-limited conduction approximation and the neutron transport equation was solved implicitly in time, in multigroup of energy and using the SN method in angular variable. In the burn equations, only the principal deuterium-deuterium (DD) and deuterium-tritium (DT) fusion reactions were taken into account, as well as the tritium production by one of the DD reaction branches and by the neutron reactions with the lithium isotopes present in the thermonuclear fuel. Three isotopic composition of lithium were considered in the calculations: natural lithium (7.42% of Li{sup 6} + 92.58% of Li{sup 7}), Li{sup 6}(50%) and Li{sup 6}(95%). In one case, the uranium of the external' tamper was considered 80% U{sup 235} enriched in order to maximize the energy from the fission component. In other case, the plutonium was used in the internal fissile mass with the purpose of determining a minimum fissile mass necessary to ignite the LiD fuel. Finally, an attempt was made to determine the possible configuration of the W-87 warhead, one of the most modern thermonuclear bombs at present in use in the United of States. The results obtained were appraised very satisfactory and they allowed a detailed analysis of the process by which a thermonuclear detonation takes place in the secondary module of the modern and compact thermonuclear bombs today in the arsenals. (author)
Remarks on the fission barriers of super-heavy nuclei
Energy Technology Data Exchange (ETDEWEB)
Hofmann, S. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Goethe-Universitaet Frankfurt, Institut fuer Physik, Frankfurt (Germany); Heinz, S.; Mann, R.; Maurer, J.; Muenzenberg, G.; Barth, W.; Dahl, L.; Kindler, B.; Kojouharov, I.; Lang, R.; Lommel, B.; Runke, J.; Scheidenberger, C.; Tinschert, K. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Antalic, S. [Comenius University, Department of Nuclear Physics and Biophysics, Bratislava (Slovakia); Eberhardt, K.; Thoerle-Pospiech, P.; Trautmann, N. [Johannes Gutenberg-Universitaet Mainz, Mainz (Germany); Grzywacz, R. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); University of Tennessee, Knoxville, TN (United States); Hamilton, J.H. [Vanderbilt University, Department of Physics and Astronomy, Nashville, TN (United States); Henderson, R.A.; Kenneally, J.M.; Moody, K.J.; Shaughnessy, D.A.; Stoyer, M.A. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Miernik, K. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); University of Warsaw, Warsaw (Poland); Miller, D. [University of Tennessee, Knoxville, TN (United States); Morita, K. [RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama (Japan); Nishio, K. [Japan Atomic Energy Agency, Tokai, Ibaraki (Japan); Popeko, A.G.; Yeremin, A.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Roberto, J.B.; Rykaczewski, K.P. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Uusitalo, J. [University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland)
2016-04-15
Shell-correction energies of super-heavy nuclei are approximated by using Q{sub α} values of measured decay chains. Five decay chains were analyzed, which start at the isotopes {sup 285}Fl, {sup 294}118, {sup 291}Lv, {sup 292}Lv and {sup 293}Lv. The data are compared with predictions of macroscopic-microscopic models. Fission barriers are estimated that can be used to eliminate uncertainties in partial fission half-lives and in calculations of evaporation-residue cross-sections. In that calculations, fission probability of the compound nucleus is a major factor contributing to the total cross-section. The data also provide constraints on the cross-sections of capture and quasi-fission in the entrance channel of the fusion reaction. Arguments are presented that fusion reactions for synthesis of isotopes of elements 118 and 120 may have higher cross-sections than assumed so far. (orig.)
Recent studies in heavy ion induced fission reactions
Choudhury, R. K.
2001-08-01
Nuclear fission process involves large scale shape changes of the nucleus, while it evolves from a nearly spherical configuration to two separated fission fragments. The dynamics of these shape changes in the nuclear many body system is governed by a strong interplay of the collective and single particle degrees of freedom. With the availability of heavy ion accelerators, there has been an impetus to study the nuclear dynamics through the investigations of nucleus--nucleus collisions involving fusion and fission process. From the various investigations carried out in the past years, it is now well recognized that there is large scale damping of collective modes in heavy ion induced fission reactions, which in other words implies that nuclear motion is highly viscous. In recent years, there have been many experimental observations in heavy ion induced fission reactions at medium bombarding energies, which suggest possible occurrence of various non-equilibrium modes of fission such as quasi-fission, fast fission and pre-equilibrium fission, where some of the internal degrees of freedom of the nucleus is not fully equilibrated. We have carried out extensive investigations on the fission fragment angular distributions at near barrier bombarding energies using heavy fissile targets. The measured fragment anisotropies when compared with the standard saddle point model (SSPM) calculations show that for projectile-target systems having zero or low ground state spins, the angular anisotropy exhibits a peak-like behaviour at the sub barrier energies, which cannot be explained by the SSPM calculations. For projectiles or targets with large ground state spins, the anomalous peaking gets washed out due to smearing of the K-distribution by the intrinsic entrance channel spins. Recently studies have been carried out on the spin distributions of fission fragments through the gamma ray multiplicity measurements. The fission fragments acquire spin mainly from two sources: (i) due to
Energy Technology Data Exchange (ETDEWEB)
Ku, L.P.; Hendel, H.W.; Liew, S.L.
1989-02-01
Neutron transport simulations have been carried out to calculate the absolute detection efficiency of a moderated /sup 235/U neutron detector which is used on the TFTR as a part of the primary fission detector diagnostic system for measuring fusion power yields. Transport simulations provide a means by which the effects of variations in various shielding and geometrical parameters can be explored. These effects are difficult to study in calibration experiments. The calculational model, benchmarked against measurements, can be used to complement future detector calibrations, when the high level of radioactivity resulting from machine operation may severely restrict access to the tokamak. We present a coupled forward-adjoint algorithm, employing both the deterministic and Monte Carlo sampling methods, to model the neutron transport in the complex tokamak and detector geometries. Sensitivities of the detector response to the major and minor radii, and angular anisotropy of the neutron emission are discussed. A semi-empirical model based on matching the calculational results with a small set of experiments produces good agreement (+-15%) for a wide range of source energies and geometries. 20 refs., 6 figs., 4 tabs.
Thermal fission rates with temperature dependent fission barriers
Zhu, Yi
2016-01-01
\\item[Background] The fission processes of thermal excited nuclei are conventionally studied by statistical models which rely on inputs of phenomenological level densities and potential barriers. Therefore the microscopic descriptions of spontaneous fission and induced fission are very desirable for a unified understanding of various fission processes. \\item[Purpose] We propose to study the fission rates, at both low and high temperatures, with microscopically calculated temperature-dependent fission barriers and mass parameters. \\item[Methods] The fission barriers are calculated by the finite-temperature Skyrme-Hartree-Fock+BCS method. The mass parameters are calculated by the temperature-dependent cranking approximation. The thermal fission rates can be obtained by the imaginary free energy approach at all temperatures, in which fission barriers are naturally temperature dependent. The fission at low temperatures can be described mainly as a barrier-tunneling process. While the fission at high temperatures ...
Directory of Open Access Journals (Sweden)
Olivier Pays
Full Text Available Despite the large number of movement studies, the constraints that grouping imposes on movement decisions remain essentially unexplored, even for highly social species. Such constraints could be key, however, to understanding the dynamics and spatial organisation of species living in group fusion-fission systems. We investigated the winter movements (speed and diffusion coefficient of groups of free-ranging roe deer (Capreolus capreolus, in an agricultural landscape characterised by a mosaic of food and foodless patches. Most groups were short-lived units that merged and split up frequently during the course of a day. Deer groups decreased their speed and diffusion rate in areas where food patches were abundant, as well as when travelling close to main roads and crest lines and far from forests. While accounting for these behavioural adjustments to habitat features, our study revealed some constraints imposed by group foraging: large groups reached the limit of their diffusion rate faster than small groups. The ability of individuals to move rapidly to new foraging locations following patch depression thus decreases with group size. Our results highlight the importance of considering both habitat heterogeneity and group dynamics when predicting the movements of individuals in group fusion-fission societies. Further, we provide empirical evidence that group cohesion can restrain movement and, therefore, the speed at which group members can explore their environment. When maintaining cohesion reduces foraging gains because of movement constraints, leaving the group may become a fitness-rewarding decision, especially when individuals can join other groups located nearby, which would tend to maintain highly dynamical group fusion-fission systems. Our findings also provide the basis for new hypotheses explaining a broad range of ecological patterns, such as the broader diet and longer residency time reported for larger herbivore groups.
紧凑型聚变裂变混合堆自举电流的数值模拟研究%Simulation on bootstrap current for the compact fusion-fission hybrid reactor
Institute of Scientific and Technical Information of China (English)
陈美霞; 刘成岳; 舒双宝
2015-01-01
On the basis of the equilibrium code Jsolver, the compact fusion-fission hybrid reactor’s advanced equilibrium configuration design is carried out, especially for the reversed shear operation mode. And the calculation, distribution and fraction of bootstrap current are also simulated.%以平衡程序Jsolver为基础开展了紧凑型聚变裂变混合堆先进等离子体平衡位形设计，重点研究了反剪切运行模式，并在此位形下研究了自举电流的计算、分布及份额。
Indian Academy of Sciences (India)
M Balasubramaniam; K R Vijayaraghavan; C Karthikraj
2015-09-01
We present the ternary fission of 252Cf and 236U within a three-cluster model as well as in a level density approach. The competition between collinear and equatorial geometry is studied by calculating the ternary fragmentation potential as a function of the angle between the lines joining the stationary middle fragment and the two end fragments. The obtained results for the 16O accompanying ternary fission indicate that collinear configuration is preferred to equatorial configuration. Further, for all the possible third fragments, the potential energy surface (PES) is calculated corresponding to an arrangement in which the heaviest and the lightest fragments are considered at the end in a collinear configuration. The PES reveals several possible ternary modes including true ternary modes where the three fragments are of similar size. The complete mass distributions of Si and Ca which accompanied ternary fission of 236U is studied within a level density picture. The obtained results favour several possible ternary combinations.
Preliminary Neutronics Design of Breed Blanket for Fusion-fission Hybrid Reactor%聚变-裂变增殖堆包层的初步中子学设计
Institute of Scientific and Technical Information of China (English)
赵奉超; 栗再新
2012-01-01
基于国际热核实验堆ITER的堆芯参数和套管结构,对聚变-裂变增殖堆包层进行了初步中子学设计.基于国际热核实验堆的堆芯参数提出了采用套管结构,以天然金属铀为燃料和硅酸锂为氚增殖剂的快裂变-增殖堆包层的初步中子学设计方案.使用FENDL 2.1核数据库及MCNP程序自带的核数据库,用MCNP程序对套管结构快裂变-增殖堆包层进行一维的方案筛选及三维中子学的计算分析.计算分析包层内的一维功率密度分布、产氚率、钚增殖率分布,通过优化设计分析给出合理的包层设计方案,并计算氚增殖率TBR、能量放大倍数M、有效增值系数(Keff)、裂变增殖比等参数.%A preliminary neutronics design of breed blanket for fusion-fission hybrid reactor has been carried out based on the plasma parameters of International Thermonuclear Experimental Reactor (ITER) and casing structure. In the design of fast-fission breed blanket, the natural Uranium pebble bed is used as fuel and neutron multiplication and the Lithium silicate pebble bed is used as tritium breed material. By using FENDL2.1 nuclear database cross section library with native cross section library of MCNP nuclear database, the calculation and analysis are carried out with MCNP program. Through one-dimension calculation and analysis on different design proposals, a proper design proposal has been screened and then the three-dimension calculation and analysis have been implemented with the parameters of ITER. The calculation shows that the TBR of fusion-fission hybrid reactor is 1.13, it indicates that the design of breed blanket is able to meet self-sustaining of tritium and the calculation also indicates that the energy enlargement of fusion-ission hybrid reactor is 6.5 and Polonium breeding rate is 1.35, it means that the reactor is able to also product large quantities energy and Polonium and they could be used by light water reactor. Meanwhile, fission
Energy Technology Data Exchange (ETDEWEB)
Hudritsch, W.W.; Smith, P.D.
1977-11-01
The one-dimensional computer program PADLOC is designed to analyze steady-state and time-dependent plateout of fission products in an arbitrary network of pipes. The problem solved is one of mass transport of impurities in a fluid, including the effects of sources in the fluid and in the plateout surfaces, convection along the flow paths, decay, adsorption on surfaces (plateout), and desorption from surfaces. These phenomena are governed by a system of coupled, nonlinear partial differential equations. The solution is achieved by (a) linearizing the equations about an approximate solution, employing a Newton Raphson iteration technique, (b) employing a finite difference solution method with an implicit time integration, and (c) employing a substructuring technique to logically organize the systems of equations for an arbitrary flow network.
Energy Technology Data Exchange (ETDEWEB)
Garner, F.A.; Greenwood, L.R. [Pacific Northwest National Lab., Richland, WA (United States); Oliver, B.M.
1996-10-01
For many years it has been accepted that significant differences exist in the helium/dpa ratios produced in fast reactors and various proposed fusion energy devices. In general, the differences arise from the much larger rate of (n,{alpha}) threshold reactions occurring in fusion devices, reactions which occur for energies {ge} 6 MeV. It now appears, however, that for nickel-containing alloys in fast reactors the difference may not have been as large as was originally anticipated. In stainless steels that have a very long incubation period for swelling, for instance, the average helium concentration over the duration of the transient regime have been demonstrated in an earlier paper to be much larger in the FFTF out-of-core regions than first calculated. The helium/dpa ratios in some experiments conducted near the core edge or just outside of the FFTF core actually increase strongly throughout the irradiation, as {sup 59}Ni slowly forms by transmutation of {sup 58}Ni. This highly exothermic {sup 59}Ni(n,{alpha}) reaction occurs in all fast reactors, but is stronger in the softer spectra of oxide-fueled cores such as FFTF and weaker in the harder spectra of metal-fueled cores such as EBR-II. The formation of {sup 59}Ni also increases strongly in out-of-core unfueled regions where the reactor spectra softens with distance from the core.
Duarte, S B; Guzmán, F; Di Marco, A; García, F; Rodríguez, O; Gonçalves, M
2002-01-01
Half-life values of spontaneous nuclear decay processes are presented in the framework of the effective liquid drop model (ELDM) using the combination of varying mass asymmetry shape description for the mass transfer (VMAS) and Werner-Wheeler's inertia coefficient (WW). The calculated half lives of ground-state to ground-state transitions for proton emission, alpha decay, cluster radioactivity, and cold fission processes are compared with experimental data. These comparisons show that the ELDM is a very efficient model to describe these different decay processes in a same, unified, theoretical framework. A table listing the predicted half-life values, tau sub c , is presented for all possible cases of spontaneous nuclear breakup such that -7.30 -17.0, where tau is the total half life of the parent nucleus.
Energy Technology Data Exchange (ETDEWEB)
Powers, Jeffrey James [Univ. of California, Berkeley, CA (United States)
2011-11-30
This study focused on creating a new tristructural isotropic (TRISO) coated particle fuel performance model and demonstrating the integration of this model into an existing system of neutronics and heat transfer codes, creating a user-friendly option for including fuel performance analysis within system design optimization and system-level trade-off studies. The end product enables both a deeper understanding and better overall system performance of nuclear energy systems limited or greatly impacted by TRISO fuel performance. A thorium-fueled hybrid fusion-fission Laser Inertial Fusion Energy (LIFE) blanket design was used for illustrating the application of this new capability and demonstrated both the importance of integrating fuel performance calculations into mainstream design studies and the impact that this new integrated analysis had on system-level design decisions. A new TRISO fuel performance model named TRIUNE was developed and verified and validated during this work with a novel methodology established for simulating the actual lifetime of a TRISO particle during repeated passes through a pebble bed. In addition, integrated self-consistent calculations were performed for neutronics depletion analysis, heat transfer calculations, and then fuel performance modeling for a full parametric study that encompassed over 80 different design options that went through all three phases of analysis. Lastly, side studies were performed that included a comparison of thorium and depleted uranium (DU) LIFE blankets as well as some uncertainty quantification work to help guide future experimental work by assessing what material properties in TRISO fuel performance modeling are most in need of improvement. A recommended thorium-fueled hybrid LIFE engine design was identified with an initial fuel load of 20MT of thorium, 15% TRISO packing within the graphite fuel pebbles, and a 20cm neutron multiplier layer with beryllium pebbles in flibe molten salt coolant. It operated
Directory of Open Access Journals (Sweden)
Minato Futoshi
2016-01-01
Full Text Available Nuclear β-decay and delayed neutron (DN emission is important for the r-process nucleosynthesis after the freeze-out, and stable and safe operation of nuclear reactors. Even though radioactive beam facilities have enabled us to measure β-decay and branching ratio of neutron-rich nuclei apart from the stability line in the nuclear chart, there are still a lot of nuclei which one cannot investigate experimentally. In particular, information on DN is rather scarce than that of T1/2. To predict T1/2 and the branching ratios of DN for next JENDL decay data, we have developed a method which comprises the quasiparticle-random-phase-approximation (QRPA and the Hauser-Feshbach statistical model (HFSM. In this work, we calculate fission fragments with T1/2 ≤ 50 sec. We obtain the rms deviation from experimental half-life of 3:71. Although the result is still worse than GT2 which has been adopted in JENDL decay data, DN spectra are newly calculated. We also discuss further subjects to be done in future for improving the present approach and making next generation of JENDL decay data.
Calculating Transition Energy Barriers and Characterizing Activation States for Steps of Fusion.
Ryham, Rolf J; Klotz, Thomas S; Yao, Lihan; Cohen, Fredric S
2016-03-08
We use continuum mechanics to calculate an entire least energy pathway of membrane fusion, from stalk formation, to pore creation, and through fusion pore enlargement. The model assumes that each structure in the pathway is axially symmetric. The static continuum stalk structure agrees quantitatively with experimental stalk architecture. Calculations show that in a stalk, the distal monolayer is stretched and the stored stretching energy is significantly less than the tilt energy of an unstretched distal monolayer. The string method is used to determine the energy of the transition barriers that separate intermediate states and the dynamics of two bilayers as they pass through them. Hemifusion requires a small amount of energy independently of lipid composition, while direct transition from a stalk to a fusion pore without a hemifusion intermediate is highly improbable. Hemifusion diaphragm expansion is spontaneous for distal monolayers containing at least two lipid components, given sufficiently negative diaphragm spontaneous curvature. Conversely, diaphragms formed from single-component distal monolayers do not expand without the continual injection of energy. We identify a diaphragm radius, below which central pore expansion is spontaneous. For larger diaphragms, prior studies have shown that pore expansion is not axisymmetric, and here our calculations supply an upper bound for the energy of the barrier against pore formation. The major energy-requiring deformations in the steps of fusion are: widening of a hydrophobic fissure in bilayers for stalk formation, splay within the expanding hemifusion diaphragm, and fissure widening initiating pore formation in a hemifusion diaphragm.
Assessing the adequacy of the bare optical potential in near-barrier fusion calculation
Energy Technology Data Exchange (ETDEWEB)
Canto, L.F. [Universidade Federal do Rio de Janeiro, Instituto de Fisica, CP 68528, Rio de Janeiro (Brazil); Gomes, P.R.S.; Lubian, J. [Universidade Federal Fluminense, Instituto de Fisica, Niteroi, R.J. (Brazil); Hussein, M.S. [Universidade de Sao Paulo, Instituto de Estudos Avancados, C. P. 72012, Sao Paulo-SP (Brazil); Universidade de Sao Paulo, Instituto de Fisica, C. P. 66318, Sao Paulo (Brazil); Lotti, P. [INFN, Padova (Italy)
2014-05-15
We critically examine the differences among the different bare nuclear interactions used in near-barrier heavy-ion fusion analysis and coupled-channels calculations, and discuss the possibility of extracting the barrier parameters of the bare potential from above-barrier data. We show that the choice of the bare potential may be critical for the analysis of the fusion cross sections. Although this may seem trivial, several recent papers use different bare potentials and reach different conclusions, especially when weakly bound systems are considered and possible relatively small fusion cross section enhancements or suppressions are found. We show also that the barrier parameters taken from above-barrier data may be very wrong. (orig.)
Dissipative dynamics in quasi-fission
Oberacker, V E; Simenel, C
2014-01-01
Quasi-fission is the primary reaction mechanism that prevents the formation of superheavy elements in heavy-ion fusion experiments. Employing the time-dependent density functional theory approach we study quasi-fission in the systems $^{40,48}$Ca+$^{238}$U. Results show that for $^{48}$Ca projectiles the quasi-fission is substantially reduced in comparison to the $^{40}$Ca case. This partly explains the success of superheavy element formation with $^{48}$Ca beams. For the first time, we also calculate the repartition of excitation energies of the two fragments in a dynamic microscopic theory. The system is found in quasi-thermal equilibrium only for reactions with $^{40}$Ca. The differences between both systems are interpreted in terms of initial neutron to proton asymmetry of the colliding partners.
Directory of Open Access Journals (Sweden)
A Parvazian
2010-12-01
Full Text Available Fast ignition is a new method for inertial confinement fusion (ICF in which the compression and ignition steps are separated. In the first stage, fuel is compressed by laser or ion beams. In the second phase, relativistic electrons are generated by pettawat laser in the fuel. Also, in the second phase 5-35 MeV protons can be generated in the fuel. Electrons or protons can penetrate in to the ultra-dense fuel and deposit their energy in the fuel . More recently, cylindrical rather than spherical fuel chambers with magnetic control in the plasma domain have been also considered. This is called magnetized target fusion (MTF. Magnetic field has effects on relativistic electrons energy deposition rate in fuel. In this work, fast ignition method in cylindrical fuel chambers is investigated and transportation of the relativistic electrons and protons is calculated using MCNPX and FLUKA codes with 0. 25 and 0. 5 tesla magnetic field in single and dual hot spot. Furthermore, the transfer rate of relativistic electrons and high energy protons to the fuel and fusion gain are calculated. The results show that the presence of external magnetic field guarantees higher fusion gain, and relativistic electrons are much more appropriate objects for ignition. MTF in dual hot spot can be considered as an appropriate substitution for the current ICF techniques.
Energy Technology Data Exchange (ETDEWEB)
Duarte, S.B.; Tavares, O.A.P.; Guzman, F.; Dimarco, A. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Garcia, F. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica; Universidade Estadual de Santa Cruz, Ilheus, BA (Brazil). Dept. de Ciencias Exatas e Tecnologicas; Rodriguez, O. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica; Instituto Superior de Ciencias e Tecnologia Nucleares, La Habana (Cuba); Goncalves, M. [Instituto de Radioprotecao e Dosimetria (IRD), Rio de Janeiro, RJ (Brazil)
2002-01-01
Half-life values of spontaneous nuclear decay processes are presented in the framework of the Effective Liquid Drop Model (ELDM) using the combination of varying mass asymmetry shape description for the mass transfer with Werner-Wheeler's inertia coefficient V{sub MAS}/WW. The calculated half-lives of ground-state to ground-state transitions for the proton emission, alpha decay, cluster radioactivity, and cold fission processes are compared with experimental data. Results have shown that the ELDM is a very efficient model to describe these different decay processes in a same, unified theoretical framework. A Table listing the predicted half-life values, {tau}{sub c} is presented for all possible cases of spontaneous nuclear break-up such that -7.30 <{approx_equal} log{sub 10} {tau}{sub c} [S] <{approx_equal} 27.50 and log {sub 10}({tau}/{tau}{sub c}) > -17.0, where {tau} is the total half-life of the parent nucleus. (author)
SPARC-90: A code for calculating fission product capture in suppression pools
Energy Technology Data Exchange (ETDEWEB)
Owczarski, P.C.; Burk, K.W. (Pacific Northwest Lab., Richland, WA (United States))
1991-10-01
This report describes the technical bases and use of two updated versions of a computer code initially developed to serve as a tool for calculating aerosol particle retention in boiling water reactor (BWR) pressure suppression pools during severe accidents, SPARC-87 and SPARC-90. The most recent version is SPARC-90. The initial or prototype version (Owczarski, Postma, and Schreck 1985) was improved to include the following: rigorous treatment of local particle deposition velocities on the surface of oblate spherical bubbles, new correlations for hydrodynamic behavior of bubble swarms, models for aerosol particle growth, both mechanistic and empirical models for vent exit region scrubbing, specific models for hydrodynamics of bubble breakup at various vent types, and models for capture of vapor iodine species. A complete user's guide is provided for SPARC-90 (along with SPARC-87). A code description, code operating instructions, partial code listing, examples of the use of SPARC-90, and summaries of experimental data comparison studies also support the use of SPARC-90. 29 refs., 4 figs., 11 tabs.
Energy Technology Data Exchange (ETDEWEB)
Guenay, Mehtap [Inoenue Univ., Malatya (Turkey). Physics Dept.
2014-03-15
In this study, the effect of spent fuel grade plutonium content on {sup 239-243}Pu was investigated in a designed hybrid reactor system. In this system, the fluids were composed of a molten salt, heavy metal mixture with increased mole fractions 99-95 % Li{sub 20}Sn{sub 80}-1-5 % SFG-Pu, 99-95 % Li{sub 20}Sn{sub 80}-1-5 % SFG-PuF{sub 4}, 99-95 % Li{sub 20}Sn{sub 80}-1-5 % SFG-PuO{sub 2}. Beryllium (Be) is a neutron multiplier by (n,2n) reactions. Thence, a Be zone of 3 cm thickness was used in order to contribute to fissile fuel breeding between the liquid first wall and a 9Cr2WVTa ferritic steel blanket which is used as structural material. The production of {sup 238-242}Pu(n,γ){sup 239-243}Pu was calculated in liquid first wall, blanket and shielding zones. Three-dimensional nucleonic calculations were performed by using the most recent version MCNPX-2.7.0 Monte Carlo code and nuclear data library ENDF/B-VII.0. (orig.)
Mahaffey, James A
2012-01-01
As energy problems of the world grow, work toward fusion power continues at a greater pace than ever before. The topic of fusion is one that is often met with the most recognition and interest in the nuclear power arena. Written in clear and jargon-free prose, Fusion explores the big bang of creation to the blackout death of worn-out stars. A brief history of fusion research, beginning with the first tentative theories in the early 20th century, is also discussed, as well as the race for fusion power. This brand-new, full-color resource examines the various programs currently being funded or p
Energy Technology Data Exchange (ETDEWEB)
Hatsukawa, Yuichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1997-07-01
Delayed fission is a nuclear decay process that couples {beta} decay and fission. In the delayed fission process, a parent nucleus undergoes {beta} decay and thereby populates excited states in the daughter. If these states are of energies comparable to or greater than the fission barrier of the daughter, then fission may compete with other decay modes of the excited states in the daughter. In this paper, mechanism and some experiments of the delayed fission will be discussed. (author)
Study of plasma equilibrium in toroidal fusion devices using mesh-free numerical calculation method
Rasouli, C.; Abbasi Davani, F.; Rokrok, B.
2016-08-01
Plasma confinement using external magnetic field is one of the successful ways leading to the controlled nuclear fusion. Development and validation of the solution process for plasma equilibrium in the experimental toroidal fusion devices is the main subject of this work. Solution of the nonlinear 2D stationary problem as posed by the Grad-Shafranov equation gives quantitative information about plasma equilibrium inside the vacuum chamber of hot fusion devices. This study suggests solving plasma equilibrium equation which is essential in toroidal nuclear fusion devices, using a mesh-free method in a condition that the plasma boundary is unknown. The Grad-Shafranov equation has been solved numerically by the point interpolation collocation mesh-free method. Important features of this approach include truly mesh free, simple mathematical relationships between points and acceptable precision in comparison with the parametric results. The calculation process has been done by using the regular and irregular nodal distribution and support domains with different points. The relative error between numerical and analytical solution is discussed for several test examples such as small size Damavand tokamak, ITER-like equilibrium, NSTX-like equilibrium, and typical Spheromak.
Pomorski, Krzysztof; Ivanyuk, Fedir A
2016-01-01
The fission-fragments mass-yield of 236U is obtained by an approximate solution of the eigenvalue problem of the collective Hamiltonian that describes the dynamics of the fission process whose degrees of freedom are: the fission (elongation), the neck and the mass-asymmetry mode. The macroscopic-microscopic method is used to evaluate the potential energy surface. The macroscopic energy part is calculated using the liquid drop model and the microscopic corrections are obtained using the Woods-Saxon single-particle levels. The four dimensional modified Cassini ovals shape parametrization is used to describe the shape of the fissioning nucleus. The mass tensor is taken within the cranking-type approximation. The final fragment mass distribution is obtained by weighting the adiabatic density distribution in the collective space with the neck-dependent fission probability. The neck degree of freedom is found to play a significant role in determining that final fragment mass distribution.
Refined Calculations of Secondary Nuclear Reactions in Magneto-Inertial Fusion Plasmas
Schmit, Paul; Knapp, Patrick; Hansen, Stephanie; Gomez, Matthew; Hahn, Kelly; Sinars, Daniel; Peterson, Kyle; Slutz, Stephen; Sefkow, Adam; Awe, Thomas; Harding, Eric; Jennings, Christopher
2014-10-01
Diagnosing the degree of magnetic flux compression at stagnation in magneto-inertial fusion (MIF) is critical for charting the performance of any MIF concept. In pure deuterium plasma, the transport of high-energy tritons produced by the aneutronic DD fusion reaction depends strongly on the magnetic field. The tritons probe and occasionally react with the fuel, emitting secondary DT neutrons. We show that the DT/DD neutron yield ratio and the secondary DT neutron spectra can be used to infer the magnetic field-radius product (BR), the critical confinement parameter for MIF. The amount of fuel-pusher mix also can be constrained by secondary reactions. We discuss the sensitivity to plasma inhomogeneities of the calculations and outline methods to relate secondary yields to alpha particle energy deposition in ignition-relevant experiments employing DT fuel. We compare our calculations to recent tests of the Magnetized Liner Inertial Fusion (MagLIF) concept on the Z Pulsed Power Facility. Supported in part by the SNL Truman Fellowship, which is part of the LDRD Program, and sponsored by Sandia Corporation (a wholly owned subsidiary of Lockheed Martin Corporation) as Operator of SNL under its U.S. DoE Contract No. DE-AC04-94AL85000.
Fission modes of mercury isotopes
Warda, M; Nazarewicz, W
2012-01-01
Recent experiments on beta-delayed fission in the mercury-lead region and the discovery of asymmetric fission in $^{180}$Hg [1] have stimulated renewed interest in the mechanism of fission in heavy nuclei. Here we study fission modes and fusion valleys in $^{180}$Hg and $^{198}$Hg using the self-consistent nuclear density functional theory employing Skyrme and Gogny energy density functionals. We show that the observed transition from asymmetric fission in $^{180}$Hg towards more symmetric distribution of fission fragments in $^{198}$Hg can be explained in terms of competing fission modes of different geometries that are governed by shell effects in pre-scission configurations. The density distributions at scission configurations are studied and related to the experimentally observed mass splits.
Romanets, Y; Vaz, P; Herrera-Martinez, A; Kadi, Y; Kharoua, C; Lettry, J; Lindroos, M
The EURISOL (The EURopean Isotope Separation On-Line Radioactive Ion Beam) project aims at producing high intensity radioactive ion beams produced by neutron induced fission on a fissile target (235U) surrounding a liquid mercury converter. A proton beam of 1 GeV and 4 MW impinges on the Hg converter generating by spallation reactions high neutron fluxes. In this work the state-of-the-art Monte Carlo codes MCNPX and FLUKA were used to assess the neutronics performance of the system which geometry, inspired from the MAFF concept, allows a versatile manipulation of the fission targets. The objective of the study was to optimize the geometry of the system and the materials used in the fuel and reflector elements of the system, in order to achieve the highest possible fission rate.
Advanced model for the prediction of the neutron-rich fission product yields
Directory of Open Access Journals (Sweden)
Rubchenya V. A.
2013-12-01
Full Text Available The consistent models for the description of the independent fission product formation cross sections in the spontaneous fission and in the neutron and proton induced fission at the energies up to 100 MeV is developed. This model is a combination of new version of the two-component exciton model and a time-dependent statistical model for fusion-fission process with inclusion of dynamical effects for accurate calculations of nucleon composition and excitation energy of the fissioning nucleus at the scission point. For each member of the compound nucleus ensemble at the scission point, the primary fission fragment characteristics: kinetic and excitation energies and their yields are calculated using the scission-point fission model with inclusion of the nuclear shell and pairing effects, and multimodal approach. The charge distribution of the primary fragment isobaric chains was considered as a result of the frozen quantal fluctuations of the isovector nuclear matter density at the scission point with the finite neck radius. Model parameters were obtained from the comparison of the predicted independent product fission yields with the experimental results and with the neutron-rich fission product data measured with a Penning trap at the Accelerator Laboratory of the University of Jyväskylä (JYFLTRAP.
Institute of Scientific and Technical Information of China (English)
陈德鸿; 杜红飞; 蒋洁琼; 汪晖; 王福琼; 陈一平; 吴宜灿; FDS团队
2012-01-01
Based on the recent experiment progress of Gas Dynamic Trap (GDT), a core plasma physics conceptual design for driving fission blanket was proposed The 0-D physical model was built and the core plasma parameters with 50 MW fusion power were preliminarily designed The reliability of the physical model and design was demonstrated by comparison between the calculation and the experiment results.%基于Gas Dynamic Trap(GDT)装置的实验进展,提出了用于驱动聚变裂变混合堆包层的聚变堆芯参数设计.基于零维堆芯物理模型,计算分析给出了一套聚变功率为50 MW的初步堆芯参数方案.利用GDT装置的实验结果对该物理模型进行计算对比校验,显示该物理模型和设计参数的可靠性.
Velasquez, Carlos E.; de P. Barros, Graiciany; Pereira, Claubia; Fortini Veloso, Maria A.; Costa, Antonella L.
2012-08-01
A sub-critical advanced reactor based on Tokamak technology with a D-T fusion neutron source is an innovative type of nuclear system. Due to the large number of neutrons produced by fusion reactions, such a system could be useful in the transmutation process of transuranic elements (Pu and minor actinides (MAs)). However, to enhance the MA transmutation efficiency, it is necessary to have a large neutron wall loading (high neutron fluence) with a broad energy spectrum in the fast neutron energy region. Therefore, it is necessary to know and define the neutron fluence along the radial axis and its characteristics. In this work, the neutron flux and the interaction frequency along the radial axis are evaluated for various materials used to build the first wall. W alloy, beryllium, and the combination of both were studied, and the regions more suitable to transmutation were determined. The results demonstrated that the best zone in which to place a transmutation blanket is limited by the heat sink and the shield block. Material arrangements of W alloy/W alloy and W alloy/beryllium would be able to meet the requirements of the high fluence and hard spectrum that are needed for transuranic transmutation. The system was simulated using the MCNP code, data from the ITER Final Design Report, 2001, and the Fusion Evaluated Nuclear Data Library/MC-2.1 nuclear data library.
Fission fragment angular distributions in pre-actinide nuclei
Banerjee, Tathagata; Nath, S.; Jhingan, A.; Kaur, Gurpreet; Dubey, R.; Yadav, Abhishek; Laveen, P. V.; Shamlath, A.; Shareef, M.; Gehlot, J.; Saneesh, N.; Prasad, E.; Sugathan, P.; Pal, Santanu
2016-10-01
measured σfis and predictions of SM indicated the presence of NCNF in at least four systems, when shell effects, both in the level density and the fission barrier, were included in the calculation. Conclusions: Systematic SM analysis of measured fission angular anisotropies and σfis confirmed the onset of NCNF in pre-actinide nuclei. Discrepancies between results about the degree of its influence on complete fusion, as deduced from various experimental probes, remain challenges to be solved. Complete measurement of all signatures of NCNF for many systems and preferably a dynamical description of the collisions between projectile and target nuclei are warranted for a deeper understanding.
Kendl, Alexander
2014-01-01
Turbulent transport of trace impurities impurities in the edge and scrape-off-layer of tokamak fusion plasmas is modelled by three dimensional electromagnetic gyrofluid computations including evolution of plasma profile gradients. The source function of impurity ions is dynamically computed from pre-determined measured and calculated electron impact ionization cross section data. The simulations describe the generation and further passive turbulent E-cross-B advection of the impurities by intermittent fluctuations and coherent filamentary structures (blobs) across the scrape-off-layer.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The paper specifies an unambiguous basic relationship between the published results of ab initio calculations of lattice energies,EL,and heats of sublimation,ΔHs,of individual energetic materials. In this relationship,the ΔHs value has been replaced by heats of fusion,ΔHm,tr. Thereby its unambiguity has been lost,and the similarity of details of molecular structure begins to be of decisive importance. The resulting partial relationships,together with the basic relationship,have been used for prediction of ΔHs,and ΔHm,tr values of technically attractive polynitro compounds.
Present status of coupled-channels calculations for heavy-ion subbarrier fusion reactions
Hagino, K
2015-01-01
The coupled-channels method has been a standard tool in analyzing heavy-ion fusion reactions at energies around the Coulomb barrier. We investigate three simplifications usually adopted in the coupled-channels calculations. These are i) the exclusion of non-collective excitations, ii) the assumption of coordinate independent coupling strengths, and iii) the harmonic oscillator approximation for multi-phonon excitations. In connection to the last point, we propose a novel microscopic method based on the beyond-mean-field approach in order to take into account the anharmonic effects of collective vibrations.
Barbosa, Daniel José; Serrat, Romàn; Mirra, Serena; Quevedo, Martí; de Barreda, Elena Goméz; Àvila, Jesús; Ferreira, Luísa Maria; Branco, Paula Sério; Fernandes, Eduarda; Lourdes Bastos, Maria de; Capela, João Paulo; Soriano, Eduardo; Carvalho, Félix
2014-06-01
3,4-Methylenedioxymethamphetamine (MDMA; "ecstasy") is a potentially neurotoxic recreational drug of abuse. Though the mechanisms involved are still not completely understood, formation of reactive metabolites and mitochondrial dysfunction contribute to MDMA-related neurotoxicity. Neuronal mitochondrial trafficking, and their targeting to synapses, is essential for proper neuronal function and survival, rendering neurons particularly vulnerable to mitochondrial dysfunction. Indeed, MDMA-associated disruption of Ca(2+) homeostasis and ATP depletion have been described in neurons, thus suggesting possible MDMA interference on mitochondrial dynamics. In this study, we performed real-time functional experiments of mitochondrial trafficking to explore the role of in situ mitochondrial dysfunction in MDMA's neurotoxic actions. We show that the mixture of MDMA and six of its major in vivo metabolites, each compound at 10μM, impaired mitochondrial trafficking and increased the fragmentation of axonal mitochondria in cultured hippocampal neurons. Furthermore, the overexpression of mitofusin 2 (Mfn2) or dynamin-related protein 1 (Drp1) K38A constructs almost completely rescued the trafficking deficits caused by this mixture. Finally, in hippocampal neurons overexpressing a Mfn2 mutant, Mfn2 R94Q, with impaired fusion and transport properties, it was confirmed that a dysregulation of mitochondrial fission/fusion events greatly contributed to the reported trafficking phenotype. In conclusion, our study demonstrated, for the first time, that the mixture of MDMA and its metabolites, at concentrations relevant to the in vivo scenario, impaired mitochondrial trafficking and increased mitochondrial fragmentation in hippocampal neurons, thus providing a new insight in the context of "ecstasy"-induced neuronal injury.
Energy Technology Data Exchange (ETDEWEB)
Nouicer, Rachid [Institut de Recherche Subatomique, CNRS-IN2P3 - Universite Louis Pasteur, 67 - Strasbourg (France)
1997-11-21
During the work on which this Thesis is based, the significant role of the Fusion-Fission Asymmetric mechanism in light heavy ion collisions (A{sub NC} {<=} 60) has been emphasized. The Spin Dis-alignment in the oblate-oblate system has supplied evidence for the first time for the Butterfly mode in a resonant-like reaction. These two aspects, one macroscopic and the other more closely related to microscopic effects are certainly different from a conceptual point of view but are quite complementary for a global understanding of dinuclear systems. In the first part, inclusive and exclusive measurements of the {sup 35}Cl + {sup 12}C and {sup 35}Cl + {sup 24}Mg reaction have been performed at 8 MeV/nucleon in the Saclay experiment. These measurements have permitted us to verify the origin of products which have given rise of the asymmetric fusion-fission mechanism and which have demonstrated that the three-body process in this energy range is very weak. In the second part the {sup 28}Si + {sup 28}Si reaction has been performed at the resonance energy E{sub lab}> = 111.6 MeV at Strasbourg with the Eurogam phase II multi-detector array and VIVITRON accelerator. An angular momentum J{sup {pi}} 38{sup +} for inelastic and mutual channels of the {sup 28}Si + {sup 28}Si exit channel has been measured and has supplied evidence for a spin dis-alignment which has been interpreted in the framework of a molecular model by Butterfly motion. The spectroscopic study of {sup 32}S nucleus, has revealed the occurrence of a new {gamma}-ray transition 0{sup +}(8507.8 keV) {yields} 2{sub 1}{sup +}(2230.2 keV). (author) 105 refs., 116 figs., 26 tabs.
Fortin, Daniel; Fortin, Marie-Eve; Beyer, Hawthorne L; Duchesne, Thierry; Courant, Sabrina; Dancose, Karine
2009-09-01
For gregarious animals the cost-benefit trade-offs that drive habitat selection may vary dynamically with group size, which plays an important role in foraging and predator avoidance strategies. We examined how habitat selection by bison (Bison bison) varied as a function of group size and interpreted these patterns by testing whether habitat selection was more strongly driven by the competing demands of forage intake vs. predator avoidance behavior. We developed an analytical framework that integrated group size into resource selection functions (RSFs). These group-size-dependent RSFs were based on a matched case-control design and were estimated using conditional logistic regression (mixed and population-averaged models). Fitting RSF models to bison revealed that bison groups responded to multiple aspects of landscape heterogeneity and that selection varied seasonally and as a function of group size. For example, roads were selected in summer, but not in winter. Bison groups avoided areas of high snow water equivalent in winter. They selected areas composed of a large proportion of meadow area within a 700-m radius, and within those areas, bison selected meadows. Importantly, the strength of selection for meadows varied as a function of group size, with stronger selection being observed in larger groups. Hence the bison-habitat relationship depended in part on the dynamics of group formation and division. Group formation was most likely in meadows. In contrast, risk of group fission increased when bison moved into the forest and was higher during the time of day when movements are generally longer and more variable among individuals. We also found that stronger selection for meadows by large rather than small bison groups was caused by longer residence time in individual meadows by larger groups and that departure from meadows appears unlikely to result from a depression in food intake rate. These group-size-dependent patterns were consistent with the hypothesis
Development of Fission Chamber Assembly
Institute of Scientific and Technical Information of China (English)
YANGJinwei; ZHANGWei; SONGXianying; LIXu
2003-01-01
The fission chambers which are gas counters with fissile material inside chamber,provide essential information for plasma opcharacteristics. In conjunction with the neutron flux monitor system these provide time-resolved measurements of the global neutron source strength and fusion power from thermal nuclear fusion reactor as ITER for all plasma conditions for which neutrons are produced.
Progress in physics design of fusion-fission hybrid energy reactor%次临界能源堆物理设计进展
Institute of Scientific and Technical Information of China (English)
李茂生; 贾建平; 程和平; 蒋洁琼; 栗再新; 杨永伟; 吴宏春; 师学明; 刘荣; 鹿心鑫; 朱通华; 王新华; 余泳; 严钧; 唐涛
2014-01-01
聚变-裂变混合能源堆包括聚变中子源和次临界能源堆，主要目标是生产电能。回顾了国内外混合堆的发展历史，给出混合能源堆设计的边界条件和约束条件，说明次临界能源堆以铀锆合金为燃料、水为冷却剂的设计思想。利用输运燃耗耦合程序 MCORGS 计算了混合能源的燃耗，给出了中子有效增殖因数、能量放大倍数和氚增殖比等物理量随时间的变化。通过分析能谱和重要核素随燃耗时间的变化，说明混合能源堆与核燃料增殖、核废料嬗变混合堆的不同特点。论述了混合堆的热工设计并进行了安全分析。对于燃耗数值模拟程序，通过多家对算，保证其计算结果的可信性。针对次临界能源堆的特点，利用贫铀球壳建立了贫铀聚乙烯装置和贫铀 LiH 装置，并且专门设计加工了天然铀装置，开展铀裂变率、造钚率、产氚率等中子学积分实验，验证了数值模拟的可靠性。%In this paper,we propose a preliminary design for a fusion-fission hybrid energy reactor (FFHER),based on cur-rent fusion science and technology and well-developed fission technology.Design rules are listed and a primary concept blanket with uranium alloy as fuel and water as coolant is put forward.The uranium fuel can be natural uranium,LWR spent fuel,or de-pleted uranium.The FFHER design can increase the utilization rate of uranium in a comparatively simple way to sustain the de-velopment of nuclear energy.The interaction between the fusion neutron and the uranium fuel with the aim of achieving greater energy multiplication and tritium sustainability is studied.Other concept hybrid reactor designs are also reviewed.Integral neu-tron experiments were carried out to verify the credibility of our proposed physical design.The combination of the physical design with the related thermal hydraulic design,alloy fuel manufacture,and nuclear fuel cycle programs provides the
Energy Technology Data Exchange (ETDEWEB)
Younes, W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-10-26
A three-year theory project was undertaken to study the fission process in extreme astrophysical environments, such as the crust of neutron stars. In the first part of the project, the effect of electron screening on the fission process was explored using a microscopic approach. For the first time, these calculations were carried out to the breaking point of the nucleus. In the second part of the project, the population of the fissioning nucleus was calculated within the same microscopic framework. These types of calculations are extremely computer-intensive and have seldom been applied to heavy deformed nuclei, such as fissioning actinides. The results, tools and methodologies produced in this work will be of interest to both the basic-science and nuclear-data communities.
Mishra, Saurabh
In the past two decades, numerical transport phenomena based models have provided useful information about the thermal cycles and weld pool geometry. However, no effort has been made to apply these concepts to design weld consumables, to study the weld bead shape on welding two plates with different sulfur contents and to tailor weld pool geometry to specified dimensions. The present research focuses on these unexplored areas. The research proposed here seeks to develop a quantitative understanding of mass transport during fusion welding, with special emphasis on the role of surface active elements and the effect of solute distribution on weld defects like liquation cracking. A comprehensive model, incorporating numerical three-dimensional calculations of temperature and velocity fields and solute distribution in the weld pool is developed for the proposed quantitative study. The study identifies the factors that affect the weld pool geometry on joining two plates with different sulfur contents, and predicts the susceptibility of an aluminum-copper alloy GMA weld to liquation cracking. The specific contributions of the present thesis research include (i) development of a numerical solute transport model for fusion welding; (ii) improving the reliability of output of the numerical model; (iii) achieving computational efficiency and economy by developing a neural network trained by data generated by the numerical model; (iv) creating a bi-directional methodology where a target weld attribute like weld pool geometry can be attained via multiple combinations of input process parameters like arc current, voltage and welding speed; (v) calculating sulfur distribution during gas tungsten arc welding of stainless steel plates with different sulfur contents and predicting the arc welding of aluminum-copper alloys by incorporating the heat and mass addition from filler metal and a non-equilibrium solidification model, and using the copper content of the mushy zone to predict
Parameter-free effective field theory calculation for the solar proton-fusion and hep processes
Energy Technology Data Exchange (ETDEWEB)
T.S. Park; L.E. Marcucci; R. Schiavilla; M. Viviani; A. Kievsky; S. Rosati; K. Kubodera; D.P. Min; M. Rho
2002-08-01
Spurred by the recent complete determination of the weak currents in two-nucleon systems up to {Omicron}(Q{sup 3}) in heavy-baryon chiral perturbation theory, we carry out a parameter-free calculation of the threshold S-factors for the solar pp (proton-fusion) and hep processes in an effective field theory that combines the merits of the standard nuclear physics method and systematic chiral expansion. The power of the EFT adopted here is that one can correlate in a unified formalism the weak-current matrix elements of two-, three- and four-nucleon systems. Using the tritium {beta}-decay rate as an input to fix the only unknown parameter in the theory, we can evaluate the threshold S factors with drastically improved precision; the results are S{sub pp}(0) = 3.94 x (1 {+-} 0.004) x 10{sup -25} MeV-b and S{sub hep}(0) = (8.6 {+-} 1.3) x 10{sup -20} keV-b. The dependence of the calculated S-factors on the momentum cutoff parameter {Lambda} has been examined for a physically reasonable range of {Lambda}. This dependence is found to be extremely small for the pp process, and to be within acceptable levels for the hep process, substantiating the consistency of our calculational scheme.
Directory of Open Access Journals (Sweden)
Jingyu Zhang
2016-01-01
Full Text Available In water-cooled reactor, the dominant radioactive source term under normal operation is activated corrosion products (ACPs, which have an important impact on reactor inspection and maintenance. A three-node transport model of ACPs was introduced into the new version of ACPs source term code CATE in this paper, which makes CATE capable of theoretically simulating the variation and the distribution of ACPs in a water-cooled reactor and suitable for more operating conditions. For code testing, MIT PWR coolant chemistry loop was simulated, and the calculation results from CATE are close to the experimental results from MIT, which means CATE is available and credible on ACPs analysis of water-cooled reactor. Then ACPs in the blanket cooling loop of water-cooled fusion reactor ITER under construction were analyzed using CATE and the results showed that the major contributors are the short-life nuclides, especially Mn-56. At last a point kernel integration code ARShield was coupled with CATE, and the dose rate around ITER blanket cooling loop was calculated. Results showed that after shutting down the reactor only for 8 days, the dose rate decreased nearly one order of magnitude, which was caused by the rapid decay of the short-life ACPs.
Energy Technology Data Exchange (ETDEWEB)
Mueller, Don [ORNL; Marshall, William BJ J [ORNL; Wagner, John C [ORNL; Bowen, Douglas G [ORNL
2015-09-01
The U.S. Nuclear Regulatory Commission (NRC) Division of Spent Fuel Storage and Transportation recently issued Interim Staff Guidance (ISG) 8, Revision 3. This ISG provides guidance for burnup credit (BUC) analyses supporting transport and storage of PWR pressurized water reactor (PWR) fuel in casks. Revision 3 includes guidance for addressing validation of criticality (k_{eff}) calculations crediting the presence of a limited set of fission products and minor actinides (FP&MA). Based on previous work documented in NUREG/CR-7109, recommendation 4 of ISG-8, Rev. 3, includes a recommendation to use 1.5 or 3% of the FP&MA worth to conservatively cover the bias due to the specified FP&MAs. This bias is supplementary to the bias and bias uncertainty resulting from validation of k_{eff} calculations for the major actinides in SNF and does not address extension to actinides and fission products beyond those identified herein. The work described in this report involves comparison of FP&MA worths calculated using SCALE and MCNP with ENDF/B-V, -VI, and -VII based nuclear data and supports use of the 1.5% FP&MA worth bias when either SCALE or MCNP codes are used for criticality calculations, provided the other conditions of the recommendation 4 are met. The method used in this report may also be applied to demonstrate the applicability of the 1.5% FP&MA worth bias to other codes using ENDF/B V, VI or VII based nuclear data. The method involves use of the applicant s computational method to generate FP&MA worths for a reference SNF cask model using specified spent fuel compositions. The applicant s FP&MA worths are then compared to reference values provided in this report. The applicants FP&MA worths should not exceed the reference results by more than 1.5% of the reference FP&MA worths.
聚变-裂变混合能源堆球模型中子学对算研究%Comparative Study on Spherical Model of Fusion-Fission Hybrid Energy Reactor
Institute of Scientific and Technical Information of China (English)
邵增; 程和平; 刘国明
2012-01-01
利用蒙特卡罗程序和自主开发的蒙特卡罗-燃耗耦合程序MOCouple-s,对北京应用物理与计算数学研究所提出的聚变-裂变混合能源堆球模型进行了对算研究.对初始时刻及各燃耗时刻下的有效增殖因数、能量倍增因子、氚增殖比、中子源强度等堆芯参数进行了比较,结果总体符合较好.对寿期末重要核素的成分进行了详细比较,除个别核素外,偏差很小,表明所采用的计算程序与核参数库一致性良好.对核参数库的选择、铀水体积比等对燃耗计算结果的影响进行敏感性分析,并对外中子源驱动的次临界堆芯的燃耗计算进行详细讨论,提出可行的燃耗计算基准.%The comparative study on fusion-fission hybrid spherical model proposed by the Institute of Applied Physics and Computational Mathematics was performed with Monte-Carlo code and MOCouple-s code. Comparisons of reactor parameters, such as neutron effective multiplication factor, energy multiplication factor, tritium breeding ratio and neutron source intensity, were made. The results agree well with the reference as a whole. The concentrations of important isotopes were also compared in detail. Most of the biases are very small except a tiny fraction of the iotopes. It proves that both codes and nuclear data library have very good consistency. In calculation of the model used, the burnup sensitivity of nuclear data and uranium-water ratio employed in the simulation model were analyzed. For such a fixed external source driven subcritical reactor core, detailed discussion was made about the burnup calculation method, and a feasible burnup calculation benchmark was proposed.
Institute of Scientific and Technical Information of China (English)
刘国明; 程和平; 邵增
2012-01-01
在聚变-裂变混合能源堆球模型基础上,使用蒙特卡罗方法中子学程序对中子源、铀水体积比、产氚区等相关参数进行了中子学的敏感性计算.分析了各参数对混合能源堆能量放大倍数M和氚增殖比TBR的影响,并总结其基本规律,为开展进一步的混合能源堆概念设计提供了重要参考.%The sensitivity analysis on neutronics parameters related to neutron source, uranium-water ratio and tritium breeding layers for spherical blanket model of fusion-fission hybrid reactor were presented. By using a Monte-Carlo method based neutron transport code, the effects of the parameters on energy multiplication factor M and tritium breeding ratio TBR were analyzed, and the general various laws of M and TBR were summarized, which were significant for the further conceptual design of fusion-fission hybrid energy reactor.
SYMMETRICAL AND ASYMMETRIC TERNARY FISSION OF HOT NUCLEI
SIWEKWILCZYNSKA, K; WILCZYNSKI, J; LEEGTE, HKW; SIEMSSEN, RH; WILSCHUT, HW; GROTOWSKI, K; PANASIEWICZ, A; SOSIN, Z; WIELOCH, A
1993-01-01
Emission of a particles accompanying fusion-fission processes in the Ar-40 + Th-232 reaction at E(Ar-40) = 365 MeV was studied in a wide range of in-fission-plane and out-of-plane angles. The exact determination of the emission angles of both fission fragments combined with the time-of-flight measur
Truchet, G.; Leconte, P.; Peneliau, Y.; Santamarina, A.; Malvagi, F.
2014-06-01
Pile-oscillation experiments are performed in the MINERVE reactor at the CEA Cadarache to improve nuclear data accuracy. In order to precisely calculate small reactivity variations (experiments, a reference calculation need to be achieved. This calculation may be accomplished using the continuous-energy Monte Carlo code TRIPOLI-4® by using the eigenvalue difference method. This "direct" method has shown limitations in the evaluation of very small reactivity effects because it needs to reach a very small variance associated to the reactivity in both states. To answer this problem, it has been decided to implement the exact perturbation theory in TRIPOLI-4® and, consequently, to calculate a continuous-energy adjoint flux. The Iterated Fission Probability (IFP) method was chosen because it has shown great results in some other Monte Carlo codes. The IFP method uses a forward calculation to compute the adjoint flux, and consequently, it does not rely on complex code modifications but on the physical definition of the adjoint flux as a phase-space neutron importance. In the first part of this paper, the IFP method implemented in TRIPOLI-4® is described. To illustrate the effciency of the method, several adjoint fluxes are calculated and compared with their equivalent obtained by the deterministic code APOLLO-2. The new implementation can calculate angular adjoint flux. In the second part, a procedure to carry out an exact perturbation calculation is described. A single cell benchmark has been used to test the accuracy of the method, compared with the "direct" estimation of the perturbation. Once again the method based on the IFP shows good agreement for a calculation time far more inferior to the "direct" method. The main advantage of the method is that the relative accuracy of the reactivity variation does not depend on the magnitude of the variation itself, which allows us to calculate very small reactivity perturbations with high precision. Other applications of
Fission dynamics within time-dependent Hartree-Fock: deformation-induced fission
Goddard, P M; Rios, A
2015-01-01
Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide $^{240}$Pu as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate non-adiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behaviour. Those beginning just beyond the ...
Exotic decay transition from cluster mode to fission mode
Santhosh, K P
2002-01-01
Exotic decay of some heavy nuclei with Z >= 100 formed in heavy ion 'cold fusion' reaction were studied taking interacting barrier consisting of Coulomb and proximity potential. Calculated half-life time shows that some modes of decay are well within the present upper limit for measurements (T sub 1 sub / sub 2 < 10 sup 3 sup 0 s). Cluster formation probabilities are calculated for different clusters within fission model. It is found that transition from cluster mode to fission mode take place at mass of the cluster, A sub 2 = 20 in exotic decay which is comparable with the value A sub 2 = 16 of Shanmugam et al based on cubic plus Yukawa plus exponential model (CYEM). (author)
Energy Technology Data Exchange (ETDEWEB)
Lee, C.E.; Apperson, C.E. Jr.; Foley, J.E.
1976-10-01
The report describes an analytic containment building model that is used for calculating the leakage into the environment of each isotope of an arbitrary radioactive decay chain. The model accounts for the source, the buildup, the decay, the cleanup, and the leakage of isotopes that are gas-borne inside the containment building.
Energy Technology Data Exchange (ETDEWEB)
Petrizzi, L.; Batistoni, P.; Migliori, S. [Associazione EURATOM ENEA sulla Fusione, Frascati (Roma) (Italy); Chen, Y.; Fischer, U.; Pereslavtsev, P. [Association FZK-EURATOM Forschungszentrum Karlsruhe (Germany); Loughlin, M. [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire, OX (United Kingdom); Secco, A. [Nice Srl Via Serra 33 Camerano Casasco AT (Italy)
2003-07-01
In deuterium-deuterium (D-D) and deuterium-tritium (D-T) fusion plasmas neutrons are produced causing activation of JET machine components. For safe operation and maintenance it is important to be able to predict the induced activation and the resulting shut down dose rates. This requires a suitable system of codes which is capable of simulating both the neutron induced material activation during operation and the decay gamma radiation transport after shut-down in the proper 3-D geometry. Two methodologies to calculate the dose rate in fusion devices have been developed recently and applied to fusion machines, both using the MCNP Monte Carlo code. FZK has developed a more classical approach, the rigorous 2-step (R2S) system in which MCNP is coupled to the FISPACT inventory code with an automated routing. ENEA, in collaboration with the ITER Team, has developed an alternative approach, the direct 1 step method (D1S). Neutron and decay gamma transport are handled in one single MCNP run, using an ad hoc cross section library. The intention was to tightly couple the neutron induced production of a radio-isotope and the emission of its decay gammas for an accurate spatial distribution and a reliable calculated statistical error. The two methods have been used by the two Associations to calculate the dose rate in five positions of JET machine, two inside the vacuum chamber and three outside, at cooling times between 1 second and 1 year after shutdown. The same MCNP model and irradiation conditions have been assumed. The exercise has been proposed and financed in the frame of the Fusion Technological Program of the JET machine. The scope is to supply the designers with the most reliable tool and data to calculate the dose rate on fusion machines. Results showed that there is a good agreement: the differences range between 5-35%. The next step to be considered in 2003 will be an exercise in which the comparison will be done with dose-rate data from JET taken during and
Eslamizadeh, H.
2017-02-01
Evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity for the excited compound nuclei {}168{{Y}}{{b}}, {}172{{Y}}{{b}}, {}178{{W}} and {}227{{P}}{{a}} produced in fusion reactions have been calculated in the framework of the modified statistical model and multidimensional dynamical model. In the dynamical calculations, the dynamics of fission of excited nuclei has been studied by solving three- and four-dimensional Langevin equations with dissipation generated through the chaos-weighted wall and window friction formula. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis, K, were considered in the four-dimensional dynamical model. A non-constant dissipation coefficient of K, {γ }k, was applied in the four-dimensional dynamical calculations. A comparison of the results of the three- and four-dimensional dynamical models with the experimental data showed that the results of the four-dimensional dynamical model for the evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity are in better agreement with the experimental data. It was also shown that the modified statistical model can reproduce the above-mentioned experimental data by choosing appropriate values of the temperature coefficient of the effective potential, λ , and the scaling factor of the fission-barrier height, {r}s.
A theoretical framework is described, allowing to determine the fission barrier height using the observed cross sections of fission induced by the (d,p)-transfer with accuracy, which is not achievable in another type of low-energy fission of neutron-deficient nuclei, the $\\beta$-delayed fission. The primary goal is to directly determine the fission barrier height of proton-rich fissile nuclei, preferably using the radio-active beams of isotopes of odd elements, and thus confirm or exclude the low values of fission barrier heights, typically extracted using statistical calculations in the compound nucleus reactions at higher excitation energies. Calculated fission cross sections in transfer reactions of the radioactive beams show sufficient sensitivity to fission barrier height. In the probable case that fission rates will be high enough, mass asymmetry of fission fragments can be determined. Results will be relevant for nuclear astrophysics and for production of super-heavy nuclei. Transfer induced fission of...
Design of In-vessel neutron monitor using micro fission chambers for ITER
Energy Technology Data Exchange (ETDEWEB)
Nishitani, Takeo; Kasai, Satoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Ebisawa, Katsuyuki [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Walker, Chris [ITER Joint Central Team, Garching (Germany)
2001-10-01
A neutron monitor using micro fission chambers to be installed inside the vacuum vessel has been designed for compact ITER (ITER-FEAT). We investigated the responses of the micro fission chambers to find the suitable position of micro fission chambers by a neutron Monte Carlo calculation using MCNP version 4b code. It was found that the averaged output of the micro fission chambers behind blankets at upper outboard and lower outboard is insensitive to the changes in the plasma position and the neutron source profile. A set of {sup 235}U micro fission chamber and ''blank'' detector which is a fissile material free detector to identify noise issues such as from {gamma}-rays are installed behind blankets. Employing both pulse counting mode and Campbelling mode in the electronics, the ITER requirement of 10{sup 7} dynamic range with 1 ms temporal resolution can be accomplished. The in-situ calibration has been simulated by MCNP calculation, where a point source of 14 MeV neutrons is moving on the plasma axis. It was found that the direct calibration is possible by using a neutron generator with an intensity of 10{sup 11} n/s. The micro fission chamber system can meet the required 10% accuracy for a fusion power monitor. (author)
Gontchar, I. I.; Chushnyakova, M. V.
2016-07-01
A systematic calculation of barriers for heavy-ion fusion was performed on the basis of the double-folding model by employing two versions of an effective nucleon-nucleon interaction: M3Y interaction and Migdal interaction. The results of calculations by the Hartree-Fockmethod with the SKX coefficients were taken for nuclear densities. The calculations reveal that the fusion barrier is higher in the case of employing theMigdal interaction than in the case of employing the M3Y interaction. In view of this, the use of the Migdal interaction in describing heavy-ion fusion is questionable.
Chopra, Sahila; Kaur, Arshdeep; Hemdeep, Gupta, Raj K.
2016-04-01
The product PCNPsurv of compound nucleus (CN) fusion probability PCN and survival probability Psurv is calculated to determine the reduced evaporation residue cross section σER/σfusion , denoted σERreduced, with (total) fusion cross section σfusion given as a sum of CN-formation cross section σCN and non-CN cross section σnCN for each reaction, where σCN is the sum of evaporation residue cross section σER and fusion-fission cross section σff and σnCN, if not measured, is estimated empirically as the difference between measured and calculated σfusion. Our calculations of PCN and Psurv, based on the dynamical cluster-decay model, were successfully made for some 17 "hot" fusion reactions, forming different CN of mass numbers ACN˜100 -300 , with deformations of nuclei up to hexadecapole deformations and "compact" orientations for both coplanar (Φc=0∘ ) and noncoplanar (Φc≠0∘ ) configurations, using various different nuclear interaction potentials. Interesting variations of σERreduced with CN excitation energy E*, fissility parameter χ , CN mass ACN, and Coulomb parameter Z1Z2 show that, independent of entrance channel, different isotopes of CN, and nuclear interaction potentials used, the dominant quantity in the product is Psurv, which classifies all the studied CN into three groups of weakly fissioning, radioactive, and strongly fissioning superheavy nuclei, with relative magnitudes of σERreduced˜1 , ˜10-6 , and ˜10-11 , which, like for PCN, get further grouped in two dependencies of (i) weakly fissioning and strongly fissioning superheavy nuclei decreasing with increasing E* and (ii) radioactive nuclei increasing with increasing E*.
Research on Nuclear Reaction Network Equation for Fission Product Nuclides
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
Nuclear Reaction Network Equation calculation system for fission product nuclides was developed. With the system, the number of the fission product nuclides at different time can be calculated in the different neutron field intensity and neutron energy spectra
Institute of Scientific and Technical Information of China (English)
陈美霞; 刘成岳; 吴斌
2012-01-01
Reversed shear (RS) operation mode is simulated with Jsolver and TSC codes on some important issues, such as RS Plasma configuration, bootstrap current fraction and RS operation mode discharge simulation etc.. To some degree, the modeling results show that the RS operation mode is advanced and feasible for the compact Fusion-fission hybrid reactor.%使用Jsolver程序及托卡马克模拟程序TSC对紧凑型聚变裂变混合堆系统的反剪切平衡位形、自举电流份额及放电模拟进行数值模拟研究,以此探讨该混合堆的可行性和先进性.
Lee, E. H.; Mansur, L. K.
2000-01-01
In an effort to develop alloys for fission and fusion reactor applications, 28Fe-15Ni-13Cr base alloys were fabricated by adding various combinations of the minor alloying elements, Mo, Ti, C, Si, P, Nb, and B. The results showed that a significant fraction of undesirable residual oxygen was removed as oxides when Ti, C, and Si were added. Accordingly, the concentrations of the latter three essential alloying elements were reduced also. Among these elements, Ti was the strongest oxide former, but the largest oxygen removal (over 80%) was observed when carbon was added alone without Ti, since gaseous CO boiled off during melting. This paper recommends an alloy melting procedure to mitigate solute losses while reducing the undesirable residual oxygen. In this work, 14 different types of precipitate phases were identified. Compositions of precipitate phases and their crystallographic data are documented. Finally, stability of precipitate phases was examined in view of Gibbs free energy of formation.
Directory of Open Access Journals (Sweden)
Somak Das
2014-01-01
Full Text Available It was proposed that resveratrol, a polyphenolic antioxidant and a calorie restriction mimetic could promote longevity but subsequent studies could not prove this. The original proposal was based on the fact that a grape-derived antioxidant could activate the antiaging gene Sirt1. Most studies agree that indeed grape activates Sirt1, but a question remains whether Sirt1 is the cause or consequence of resveratrol treatment. Subsequently, mitochondrial Sirt3 was found to be activated. The present study on ischemic reperfusion (I/R in rat hearts demonstrates that Foxo3a is activated subsequent to Sirt3 activation, which then activates PINK1. PINK1 potentiates activation of PARKIN leading to the activation of mitochondrial fission and mitophagy. Confocal microscopy conclusively shows the coexistence of Sirt3 with Foxo3a and Foxo3a with PINK1 and PARKIN. Mitophagy was demonstrated both by confocal microscopy and transmission electron microscopy. Western blot analyses data are consistent with the results of confocal microscopy. It appears that the grape-derived antioxidant modifies the intracellular environment by changing the oxidizing milieu into a reducing milieu and upregulating intracellular glutathione, potentiates a signal transduction cascade consisting of Sirt1/Sirt3-Foxo3a-PINK1-PARKIN-mitochondrial fusion fission-mitophagy that leads to cardioprotection, and paves the way to an anti-aging environment.
Conceptual design of Z-pinch driven fusion-fission hybrid power reactor%Z箍缩驱动聚变-裂变混合堆总体概念研究进展
Institute of Scientific and Technical Information of China (English)
李正宏; 周林; 黄洪文; 王真; 陈晓军; 祁建敏; 郭海兵; 马纪敏; 肖成建; 褚衍运
2014-01-01
Z箍缩驱动聚变-裂变混合能源堆(Z-FFR)在核安全、经济、持久和环境友好等方面具有优良的品质，有望成为有效应对未来能源危机和环境、气候问题的新能源。从 Z箍缩驱动聚变方案与聚变靶设计、重复频率驱动器、次临界包层及产氚包层设计、燃料循环等关键问题方面，对Z-FFR工程概念总体研究情况进行了介绍。%The Z-pinch driven fusion-fission hybrid power reactor(Z-FFR)has remarkable advantages in nuclear security,e-conomy,permanence and environment-friendliness,it can promisingly be millennial energy source dealing effectively with future energy crisis and climate problem.This article introduces the status quo of the conceptual research on Z-FFR from aspects of fu-sion-target physics,low-repetitive Z-pinch driver development,sub-critical fission reactor design and fuel cycle analysis.
Activation Characteristics of Fuel Breeding Blanket Module in Fusion Driven Subcritical System
Institute of Scientific and Technical Information of China (English)
HUANG Qun-Ying; LI Jian-Gang; CHEN Yi-Xue
2004-01-01
@@ Shortage of energy resources and production of long-lived radioactivity wastes from fission reactors are among the main problems which will be faced in the world in the near future. The conceptual design of a fusion driven subcritical system (FDS) is underway in Institute of Plasma Physics, Chinese Academy of Sciences. There are alternative designs for multi-functional blanket modules of the FDS, such as fuel breeding blanket module (FBB)to produce fuels for fission reactors, tritium breeding blanket module to produce the fuel, i.e. tritium, for fusion reactor and waste transmutation blanket module to try to permanently dispose of long-lived radioactivity wastes from fission reactors, etc. Activation of the fuel breeding blanket of the fusion driven subcritical system (FDS-FBB) by D-T fusion neutrons from the plasma and fission neutrons from the hybrid blanket are calculated and analysed under the neutron wall loading 0.5 MW/m2 and neutron fluence 15 MW. yr/m2. The neutron spectrum is calculated with the worldwide-used transport code MCNP/4C and activation calculations are carried out with the well known European inventory code FISPACT/99 with the latest released IAEA Fusion Evaluated Nuclear Data Library FENDL-2.0 and the ENDF/B-V uranium evaluated data. Induced radioactivities, dose rates and afterheats, etc, for different components of the FDS-FBB are compared and analysed.
Directory of Open Access Journals (Sweden)
Patties Ina
2006-03-01
Full Text Available Abstract Background In eukaryotes, histone H3 lysine 9 (H3K9 methylation is a common mechanism involved in gene silencing and the establishment of heterochromatin. The loci of the major heterochromatic H3K9 methyltransferase Su(var3-9 and the functionally unrelated γ subunit of the translation initiation factor eIF2 are fused in Drosophila melanogaster. Here we examined the phylogenetic distribution of this unusual gene fusion and the molecular evolution of the H3K9 HMTase Su(var3-9. Results We show that the gene fusion had taken place in the ancestral line of winged insects and silverfishs (Dicondylia about 400 million years ago. We cloned Su(var3-9 genes from a collembolan and a spider where both genes ancestrally exist as independent transcription units. In contrast, we found a Su(var3-9-specific exon inside the conserved intron position 81-1 of the eIF2γ gene structure in species of eight different insect orders. Intriguinly, in the pea aphid Acyrthosiphon pisum, we detected only sequence remains of this Su(var3-9 exon in the eIF2γ intron, along with an eIF2γ-independent Su(var3-9 gene. This reveals an evolutionary re-fission of both genes in aphids. Su(var3-9 chromo domains are similar to HP1 chromo domains, which points to a potential binding activity to methylated K9 of histone H3. SET domain comparisons suggest a weaker methyltransferase activity of Su(var3-9 in comparison to other H3K9 HMTases. Astonishingly, 11 of 19 previously described, deleterious amino acid substitutions found in Drosophila Su(var3-9 are seemingly compensable through accompanying substitutions during evolution. Conclusion Examination of the Su(var3-9 evolution revealed strong evidence for the establishment of the Su(var3-9/eIF2γ gene fusion in an ancestor of dicondylic insects and a re-fission of this fusion during the evolution of aphids. Our comparison of 65 selected chromo domains and 93 selected SET domains from Su(var3-9 and related proteins offers
Chang, G. S.; Lillo, M. A.
2009-08-01
-Z mini-plate fuel model was developed. The Y-Z model divides each fuel plate into 30 equal intervals in both the Y and Z directions. The MCNP-calculated results and the detailed Y-Z fission power mapping were used to help design the AFIP fuel test assembly to demonstrate that the AFIP test assembly thermal-hydraulic limits will not exceed the ATR safety limits.
Fission modelling with FIFRELIN
Energy Technology Data Exchange (ETDEWEB)
Litaize, Olivier; Serot, Olivier; Berge, Leonie [CEA, DEN, DER, SPRC, Saint Paul Lez Durance (France)
2015-12-15
The nuclear fission process gives rise to the formation of fission fragments and emission of particles (n,γ, e{sup -}). The particle emission from fragments can be prompt and delayed. We present here the methods used in the FIFRELIN code, which simulates the prompt component of the de-excitation process. The methods are based on phenomenological models associated with macroscopic and/or microscopic ingredients. Input data can be provided by experiment as well as by theory. The fission fragment de-excitation can be performed within Weisskopf (uncoupled neutron and gamma emission) or a Hauser-Feshbach (coupled neutron/gamma emission) statistical theory. We usually consider five free parameters that cannot be provided by theory or experiments in order to describe the initial distributions required by the code. In a first step this set of parameters is chosen to reproduce a very limited set of target observables. In a second step we can increase the statistics to predict all other fission observables such as prompt neutron, gamma and conversion electron spectra but also their distributions as a function of any kind of parameters such as, for instance, the neutron, gamma and electron number distributions, the average prompt neutron multiplicity as a function of fission fragment mass, charge or kinetic energy, and so on. Several results related to different fissioning systems are presented in this work. The goal in the next decade will be i) to replace some macroscopic ingredients or phenomenological models by microscopic calculations when available and reliable, ii) to be a support for experimentalists in the design of detection systems or in the prediction of necessary beam time or count rates with associated statistics when measuring fragments and emitted particle in coincidence iii) extend the model to be able to run a calculation when no experimental input data are available, iv) account for multiple chance fission and gamma emission before fission, v) account for
Fission modelling with FIFRELIN
Litaize, Olivier; Serot, Olivier; Berge, Léonie
2015-12-01
The nuclear fission process gives rise to the formation of fission fragments and emission of particles (n,γ , e-) . The particle emission from fragments can be prompt and delayed. We present here the methods used in the FIFRELIN code, which simulates the prompt component of the de-excitation process. The methods are based on phenomenological models associated with macroscopic and/or microscopic ingredients. Input data can be provided by experiment as well as by theory. The fission fragment de-excitation can be performed within Weisskopf (uncoupled neutron and gamma emission) or a Hauser-Feshbach (coupled neutron/gamma emission) statistical theory. We usually consider five free parameters that cannot be provided by theory or experiments in order to describe the initial distributions required by the code. In a first step this set of parameters is chosen to reproduce a very limited set of target observables. In a second step we can increase the statistics to predict all other fission observables such as prompt neutron, gamma and conversion electron spectra but also their distributions as a function of any kind of parameters such as, for instance, the neutron, gamma and electron number distributions, the average prompt neutron multiplicity as a function of fission fragment mass, charge or kinetic energy, and so on. Several results related to different fissioning systems are presented in this work. The goal in the next decade will be i) to replace some macroscopic ingredients or phenomenological models by microscopic calculations when available and reliable, ii) to be a support for experimentalists in the design of detection systems or in the prediction of necessary beam time or count rates with associated statistics when measuring fragments and emitted particle in coincidence iii) extend the model to be able to run a calculation when no experimental input data are available, iv) account for multiple chance fission and gamma emission before fission, v) account for the
(d,p)-transfer induced fission of heavy radioactive beams
Veselsky, Martin
2012-01-01
(d,p)-transfer induced fission is proposed as a tool to study low energy fission of exotic heavy nuclei. Primary goal is to directly determine the fission barrier height of proton-rich fissile nuclei, preferably using the radio-active beams of isotopes of odd elements, and thus confirm or exclude the low values of fission barrier heights, typically extracted using statistical calculations in the compound nucleus reactions at higher excitation energies. Calculated fission cross sections in transfer reactions of the radioactive beams show sufficient sensitivity to fission barrier height. In the probable case that fission rates will be high enough, mass asymmetry of fission fragments can be determined. Results will be relevant for nuclear astrophysics and for production of super-heavy nuclei. Transfer induced fission offers a possibility for systematic study the low energy fission of heavy exotic nuclei at the ISOLDE.
Multi-Nucleon Exchange in Quasi-Fission Reactions
Ayik, S; Yilmaz, O
2015-01-01
Nucleon exchange mechanism is investigated in the central collisions of ${}^{40}$Ca + ${}^{238}$U and ${}^{48}$Ca + ${}^{238}$U systems near the quasi-fission regime in the framework of the Stochastic Mean-Field (SMF) approach. Sufficiently below the fusion barrier, di-nuclear structure in the collisions is maintained to a large extend. Consequently, it is possible to describe nucleon exchange as a diffusion process familiar from deep-inelastic collisions. Diffusion coefficients for proton and neutron exchange are determined from the microscopic basis of the SMF approach in the semi-classical framework. Calculations show that after a fast charge equilibration the system drifts toward symmetry over a very long interaction time. Large dispersions of proton and neutron distributions of the produced fragments indicate that diffusion mechanism may help to populate heavy trans-uranium elements near the quasi-fission regime in these collisions.
Theoretical Description of the Fission Process
Energy Technology Data Exchange (ETDEWEB)
Witold Nazarewicz
2003-07-01
The main goals of the project can be summarized as follows: Development of effective energy functionals that are appropriate for the description of heavy nuclei. Our goal is to improve the existing energy density (Skyrme) functionals to develop a force that will be used in calculations of fission dynamics. Systematic self-consistent calculations of binding energies and fission barriers of actinide and trans-actinide nuclei using modern density functionals. This will be followed by calculations of spontaneous fission lifetimes and mass and charge divisions using dynamic adiabatic approaches based on the WKB approximation. Investigate novel microscopic (non-adiabatic) methods to study the fission process.
Bloch, F.; Staub, H.
1943-08-18
Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951
Sub-library of Updated Fission Barrier Parameters(CENPL-FBP2)
Institute of Scientific and Technical Information of China (English)
2001-01-01
The fission barrier parameters are important to determine the fission character of a nucleus. The fission barrier parameters and fission level densities are key ingredients in calculations of not only fission cross section but also various cross sections, and spectra for the fissile nuclides, even heavy nuclides at higher incident energies. It is necessaries that the accuracy of fission barrier parameters requires even higher, and nuclides with fission barrier parameters can cover even wider nuclear range.
Assessment of fissionable material behaviour in fission chambers
Energy Technology Data Exchange (ETDEWEB)
Cabellos, O., E-mail: oscar.cabellos@upm.e [Instituto de Fusion Nuclear, Universidad Politecnica de Madrid, 28006 Madrid (Spain); Department of Nuclear Engineering, Universidad Politecnica de Madrid, 28006 Madrid (Spain); Fernandez, P. [Department of Nuclear Engineering, Universidad Politecnica de Madrid, 28006 Madrid (Spain); Rapisarda, D. [Laboratorio Nacional de Fusion, EURATOM-CIEMAT, 28040 Madrid (Spain); Garcia-Herranz, N. [Instituto de Fusion Nuclear, Universidad Politecnica de Madrid, 28006 Madrid (Spain); Department of Nuclear Engineering, Universidad Politecnica de Madrid, 28006 Madrid (Spain)
2010-06-21
A comprehensive study is performed in order to assess the pertinence of fission chambers coated with different fissile materials for high neutron flux detection. Three neutron scenarios are proposed to study the fast component of a high neutron flux: (i) high neutron flux with a significant thermal contribution such as BR2, (ii) DEMO magnetic fusion reactor, and (iii) IFMIF high flux test module. In this study, the inventory code ACAB is used to analyze the following questions: (i) impact of different deposits in fission chambers; (ii) effect of the irradiation time/burn-up on the concentration; (iii) impact of activation cross-section uncertainties on the composition of the deposit for all the range of burn-up/irradiation neutron fluences of interest. The complete set of nuclear data (decay, fission yield, activation cross-sections, and uncertainties) provided in the EAF2007 data library are used for this evaluation.
Intrinsic energy partition in fission
Directory of Open Access Journals (Sweden)
Mirea M.
2013-03-01
Full Text Available The intrinsic energy partition between two complementary fission fragments is investigated microscopically. The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time-dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the other separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The excitation energy in a wide distribution of fission fragments is calculated for the 234U parent nucleus.
Veselsky, Martin; Ma, Yu-Gang; Souliotis, Georgios A
2016-01-01
The mechanism of fusion hindrance, an effect preventing the synthesis of superheavy elements in the reactions of cold and hot fusion, is investigated using the Boltzmann-Uehling-Uhlenbeck equation, where Coulomb interaction is introduced. A strong sensitivity is observed both to the modulus of incompressibility of symmetric nuclear matter, controlling the competition of surface tension and Coulomb repulsion, and to the stiffness of the density-dependence of symmetry energy, influencing the formation of the neck prior to scission. The experimental fusion probabilities were for the first time used to derive constraints on the nuclear equation of state. A strict constraint on the modulus of incompressibility of nuclear matter $K_0 = 240 - 260$ MeV is obtained while the stiff density-dependences of the symmetry energy ($\\gamma>1.$) are rejected.
Advanced Space Fission Propulsion Systems
Houts, Michael G.; Borowski, Stanley K.
2010-01-01
Fission has been considered for in-space propulsion since the 1940s. Nuclear Thermal Propulsion (NTP) systems underwent extensive development from 1955-1973, completing 20 full power ground tests and achieving specific impulses nearly twice that of the best chemical propulsion systems. Space fission power systems (which may eventually enable Nuclear Electric Propulsion) have been flown in space by both the United States and the Former Soviet Union. Fission is the most developed and understood of the nuclear propulsion options (e.g. fission, fusion, antimatter, etc.), and fission has enjoyed tremendous terrestrial success for nearly 7 decades. Current space nuclear research and technology efforts are focused on devising and developing first generation systems that are safe, reliable and affordable. For propulsion, the focus is on nuclear thermal rockets that build on technologies and systems developed and tested under the Rover/NERVA and related programs from the Apollo era. NTP Affordability is achieved through use of previously developed fuels and materials, modern analytical techniques and test strategies, and development of a small engine for ground and flight technology demonstration. Initial NTP systems will be capable of achieving an Isp of 900 s at a relatively high thrust-to-weight ratio. The development and use of first generation space fission power and propulsion systems will provide new, game changing capabilities for NASA. In addition, development and use of these systems will provide the foundation for developing extremely advanced power and propulsion systems capable of routinely and affordably accessing any point in the solar system. The energy density of fissile fuel (8 x 10(exp 13) Joules/kg) is more than adequate for enabling extensive exploration and utilization of the solar system. For space fission propulsion systems, the key is converting the virtually unlimited energy of fission into thrust at the desired specific impulse and thrust
Some aspects of fission and quasifission processes
Indian Academy of Sciences (India)
B B Back
2015-08-01
The discovery of nuclear fission in 1938–1939 had a profound influence on the field of nuclear physics and it brought this branch of physics into the forefront as it was recognized for having the potential for its seminal influence on modern society. Although many of the basic features of actinide fission were described in a ground-breaking paper by Bohr and Wheeler only six months after the discovery, the fission process is very complex and it has been a challenge for both experimentalists and theorists to achieve a complete and satisfactory understanding of this phenomenon. Many aspects of nuclear physics are involved in fission and it continues to be a subject of intense study even three quarters of a century after its discovery. In this talk, I will review an incomplete subset of the major milestones in fission research, and briefly discuss some of the topics that I have been involved in during my career. These include studies of vibrational resonances and fission isomers that are caused by the second minimum in the fission barrier in actinide nuclei, studies of heavy-ion-induced fission in terms of the angular distributions and the mass–angle correlations of fission fragments. Some of these studies provided evidence for the importance of the quasifission process and the attendant suppression of the complete fusion process. Finally, some of the circumstances around the establishment of large-scale nuclear research in India will be discussed.
Evolution of isotopic fission-fragment yields with excitation energy
Directory of Open Access Journals (Sweden)
Bazin D.
2012-07-01
Full Text Available Two fission experiments have been performed at GANIL using 238U beams at different energies and light targets. Different fissioning systems were produced with excitation energies from 10 to 230 MeV and their decay by fission was investigated with GANIL spectrometers. Preliminary fission-fragment isotopic distributions have been obtained. The evolution with impinging energy of their properties, the neutron excess and the width of the neutron-number distributions, gives important insights into the dynamics of fusion-fission mechanism.
Fusion probability in heavy nuclei
Banerjee, Tathagata; Nath, S.; Pal, Santanu
2015-03-01
Background: Fusion between two massive nuclei is a very complex process and is characterized by three stages: (a) capture inside the potential barrier, (b) formation of an equilibrated compound nucleus (CN), and (c) statistical decay of the CN leading to a cold evaporation residue (ER) or fission. The second stage is the least understood of the three and is the most crucial in predicting yield of superheavy elements (SHE) formed in complete fusion reactions. Purpose: A systematic study of average fusion probability, PCN> , is undertaken to obtain a better understanding of its dependence on various reaction parameters. The study may also help to clearly demarcate onset of non-CN fission (NCNF), which causes fusion probability, PCN, to deviate from unity. Method: ER excitation functions for 52 reactions leading to CN in the mass region 170-220, which are available in the literature, have been compared with statistical model (SM) calculations. Capture cross sections have been obtained from a coupled-channels code. In the SM, shell corrections in both the level density and the fission barrier have been included. PCN> for these reactions has been extracted by comparing experimental and theoretical ER excitation functions in the energy range ˜5 %-35% above the potential barrier, where known effects of nuclear structure are insignificant. Results: PCN> has been shown to vary with entrance channel mass asymmetry, η (or charge product, ZpZt ), as well as with fissility of the CN, χCN. No parameter has been found to be adequate as a single scaling variable to determine PCN> . Approximate boundaries have been obtained from where PCN> starts deviating from unity. Conclusions: This study quite clearly reveals the limits of applicability of the SM in interpreting experimental observables from fusion reactions involving two massive nuclei. Deviation of PCN> from unity marks the beginning of the domain of dynamical models of fusion. Availability of precise ER cross sections
Spontaneous fission of superheavy nuclei
Indian Academy of Sciences (India)
R A Gherghescu; D N Poenaru
2015-09-01
The macroscopic–microscopic method is extended to calculate the deformation energy and penetrability for binary nuclear configurations typical for fission processes. The deformed two-centre shell model is used to obtain single-particle energy levels for the transition region of two partially overlapped daughter and emitted fragment nuclei. The macroscopic part is obtained using the Yukawa-plus-exponential potential. The microscopic shell and pairing corrections are obtained using the Strutinsky and BCS approaches and the cranking formulae yield the inertia tensor. Finally, the WKB method is used to calculate penetrabilities and spontaneous fission half-lives. Calculations are performed for the decay of 282,292120 nuclei.
Magnetic fusion reactor economics
Energy Technology Data Exchange (ETDEWEB)
Krakowski, R.A.
1995-12-01
An almost primordial trend in the conversion and use of energy is an increased complexity and cost of conversion systems designed to utilize cheaper and more-abundant fuels; this trend is exemplified by the progression fossil fission {yields} fusion. The present projections of the latter indicate that capital costs of the fusion ``burner`` far exceed any commensurate savings associated with the cheapest and most-abundant of fuels. These projections suggest competitive fusion power only if internal costs associate with the use of fossil or fission fuels emerge to make them either uneconomic, unacceptable, or both with respect to expensive fusion systems. This ``implementation-by-default`` plan for fusion is re-examined by identifying in general terms fusion power-plant embodiments that might compete favorably under conditions where internal costs (both economic and environmental) of fossil and/or fission are not as great as is needed to justify the contemporary vision for fusion power. Competitive fusion power in this context will require a significant broadening of an overly focused program to explore the physics and simbiotic technologies leading to more compact, simplified, and efficient plasma-confinement configurations that reside at the heart of an attractive fusion power plant.
Directory of Open Access Journals (Sweden)
Privas Edwin
2016-01-01
Full Text Available The effective Neodymium cumulative fission yields for 235U have been measured in the fast reactor PHENIX relatively to the 235U fission cross-section. The data were derived from isotope-ratio measurements obtained in the frame of the PROFIL-1, PROFIL-2A and PROFIL-2B programs. The interpretations of the experimental programs were performed with the ERANOS code in association with the Joint Evaluated Fission and Fusion library JEFF-3.1.1. Final results for 143Nd, 145Nd, 146Nd, 148Nd and 150Nd were 5.61%, 3.70%, 2.83%, 1.64% and 0.66%, respectively. The relative uncertainties attached to each of the cumulative fission yields lie between 2.1% and 2.4%. The main source of uncertainty is due to the fluence scaling procedure (<2%. The uncertainties on the Neodymium capture cross-sections provide a contribution lower than 1%. The energy dependence of the fission yields was studied with the GEF code from the thermal energy to 20 MeV. Neutron spectrum average corrections, deduced from GEF calculations, were applied to our effective fission yields with the aim of estimating fission yields at 400 keV and 500 keV, as given in the International Evaluated Nuclear Data Files (JEFF, ENDF/B and JENDL. The neutron spectrum average correction calculated for the PROFIL results remains lower than 1.5%.
DEFF Research Database (Denmark)
Christiansen, Steen Ledet
; it is a materialisation of an ideological fission which attempts to excise certain ideological constructions, yet paradoxically casting them in a form that is recognizable and familiar. The monstrous metonomy which is used shows us glimpses of a horrid being, intended to vilify the attack on New York City. However......, it is a being which is reminiscent of earlier monsters - from Godzilla to The Blob. It is evident that the Cloverfield monster is a paradoxical construction which attempts to articulate fear and loathing about terrorism, but ends up trapped in an ideological dead-end maze, unable to do anything other than...
Keutgen, T; El-Masri, Y; Ghisalberti, C; Tilquin, I; Lebreton, L; Ninane, A; Lehmann, J; Roberfroid, V; Michel, L; Regimbart, R; Natowitz, J B; Hagel, K; Wada, R; Charity, R J
1999-01-01
We have undertaken a study of the thermal and the dynamical properties of fission and evaporation processes through the observation of neutron and light charged particle (LCP) emission (p, alpha) in collisions of sup 2 sup 0 Ne + sup 1 sup 5 sup 9 Tb and sup 2 sup 0 Ne + sup 1 sup 6 sup 9 Tm at 8, 10, 13 and 16 MeV/nucleon using the neutron multidetector DEMON. Both systems lead to the formation of compound nuclei (CN) with initial excitation energies (E* sub z) ranging between 100 and 250 MeV. These CN, formed through complete (CF) or incomplete (IF) fusion reactions, decay through either fission or evaporation residue (ER) formation. Our experimental goal in this study is to establish, as a function of E* sub x , i) sigma sub E sub R /sigma sub f sub i sub s sub s sub i sub o sub n cross-section ratios, ii) pre- and post-scission neutron and LCP multiplicities with a clear cut assignment to CF and IF processes and iii) to try to consistently interpret these data in the framework of the recently modified sta...
Aneutronic Fusion Spacecraft Architecture Project
National Aeronautics and Space Administration — Description: provide framework to realize fusion propulsion for long-range space travel; analyze “hybrid” schemes with a solar or fission primary energy...
面向Z箍缩驱动聚变能源需求的超高功率重复频率驱动器技术%Super-power repetitive Z-pinch driver for fusion-fission reactor
Institute of Scientific and Technical Information of China (English)
邓建军; 陈林; 夏明鹤; 计策; 袁建强; 宋盛义; 黄显宾; 彭先觉; 王勐; 谢卫平; 周良骥; 邹文康; 郭帆; 章乐; 李逢; 丰树平
2014-01-01
According to the demands of Z-pinch driven fusion-fission reactor(Z-FFR),several possible technical schemes are analyzed and evaluated.A novel technical scheme named mixed-mode LTD is proposed.A conceptual design of Z-FFR driver is presented based on mixed-mode LTD scheme.The main directions for key technologies development are pointed out.A road-map is proposed for the super-power Z-pinch driver development.%针对Z箍缩驱动聚变裂变混合能源系统对驱动器的总体要求，对可能的技术路线进行了分析评述，结合当前在单脉冲超高功率Z箍缩驱动器和重复频率脉冲功率技术方面的研究基础，提出了混合模式直线变压驱动器概念设计思想，分析了主要的技术难点，明确了相应的关键技术攻关方向，同时对 Z 箍缩驱动器的总体发展计划提出了建议。
Effect of nuclear viscosity on fission process
Energy Technology Data Exchange (ETDEWEB)
Li Shidong; Kuang Huishun; Zhang Shufa; Xing Jingru; Zhuo Yizhong; Wu Xizhen; Feng Renfa
1989-02-01
According to the fission diffusion model, the deformation motion of fission nucleuses is regarded as a diffusion process of quasi-Brownian particles under fission potential. Through simulating such Brownian motion in two dimensional phase space by Monte-Carlo mehtod, the effect of nuclear visocity on Brownian particle diffusion is studied. Dynamical quanties, such as fission rate, kinetic energy distribution on scission, and soon are numerically calculated for various viscosity coefficients. The results are resonable in physics. This method can be easily extended to deal with multi-dimensional diffusion problems.
Application of the dinuclear system model to fission process
Directory of Open Access Journals (Sweden)
Andreev A. V.
2016-01-01
Full Text Available A theoretical evaluation of the collective excitation spectra of nucleus at large deformations is possible within the framework of the dinuclear system model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two-cluster configurations in a dynamical way, permitting exchange of nucleons between clusters. In this work the method of calculation of the potential energy and the collective spectrum of fissioning nucleus at scission point is presented. Combining the DNS model calculations and the statistical model of fission we calculate the mass, total kinetic energy, and angular distribution of fission fragments for the neutron–induced fission of 239Pu.
Collective spectra along the fission barrier
Directory of Open Access Journals (Sweden)
Pigni M. T.
2012-12-01
Full Text Available Discrete and continuous spectra of fissioning nuclei at the humps of fission barriers (Bohr transition states and in the intermediate wells (superdeformed and hyperdeformed states play a key role in the calculation of fission cross sections. A theoretical evaluation of the collective parts of the spectra is possible within the framework of the dinuclear system model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two–cluster configurations in a dynamical way, permitting exchange of upper–shell nucleons between clusters. The impact of theoretical spectra on neutron–induced fission cross sections and, in combination with an improved version of the scission–point model, on angular distribution of fission fragments is evaluated for plutonium isotopes of interest to nuclear energy applications.
Shizgal, Bernie D.
2016-08-01
Nonclassical quadratures based on a new set of half-range polynomials, Tn(x) , orthogonal with respect to w(x) =e - x - b /√{ x } for x ∈ [ 0 , ∞) are employed in the efficient calculation of the nuclear fusion reaction rate coefficients from cross section data. The parameter b = B /√{kB T } in the weight function is temperature dependent and B is the Gamow factor. The polynomials Tn(x) satisfy a three term recurrence relation defined by two sets of recurrence coefficients, αn and βn. These recurrence coefficients define in turn the tridiagonal Jacobi matrix whose eigenvalues are the quadrature points and the weights are calculated from the first components of the eigenfunctions. For nonresonant nuclear reactions for which the astrophysical function can be expressed as a lower order polynomial in the relative energy, the convergence of the thermal average of the reactive cross section with this nonclassical quadrature is extremely rapid requiring in many cases 2-4 quadrature points. The results are compared with other libraries of nuclear reaction rate coefficient data reported in the literature.
Energy Technology Data Exchange (ETDEWEB)
Qiu, Yuefeng, E-mail: yuefeng.qiu@kit.edu [Association KIT-Euratom, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Karlsruhe (Germany); Lu, Peng [Association KIT-Euratom, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Karlsruhe (Germany); School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Fischer, Ulrich; Pereslavtsev, Pavel; Kecskes, Szabolcs [Association KIT-Euratom, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Karlsruhe (Germany)
2014-10-15
Highlights: • A data translation scheme has been developed for coupling Monte Carlo neutronics and CFD simulations. • It contains a generic data translation kernel, and interfaces for the MCNP, CFX and Fluent code. • A blanket test case model was investigated for validation and verification purposes. • Results of the so-called Inversion Check are very close to MCNP calculated results. - Abstract: The design of fusion device components is achieved through iterative coupled neutronics and thermal hydraulics analyses. A translation scheme has been developed for transferring the nuclear heating data from Monte Carlo (MC) neutronic calculations to CFD simulations. It contains a generic data translation kernel which supports the high-fidelity data mapping of MC meshes on CFD meshes, and provides interfaces for processing the nuclear response data on the meshes for CFD codes. This translation scheme has been implemented in the open-source pre- and post-processing platform SALOME to extend its capabilities on data manipulations and visualizations. For verification purposes, a blanket test case based on the Helium Cooled Pebble Bed Test Blanket Module was investigated. The processing of the heating distribution data was validated through a so-called Inversion Check comparing the inverted heating field with the original MC tally distribution. The results of the verification have been discussed in detail, and the reliability of the data translation scheme is concluded.
Knaster, J.; Moeslang, A.; Muroga, T.
2016-05-01
Fusion materials research started in the early 1970s following the observation of the degradation of irradiated materials used in the first commercial fission reactors. The technological challenges of fusion energy are intimately linked with the availability of suitable materials capable of reliably withstanding the extremely severe operational conditions of fusion reactors. Although fission and fusion materials exhibit common features, fusion materials research is broader. The harder mono-energetic spectrum associated with the deuterium-tritium fusion neutrons (14.1 MeV compared to hydrogen and helium as transmutation products that might lead to a (at present undetermined) degradation of structural materials after a few years of operation. Overcoming the historical lack of a fusion-relevant neutron source for materials testing is an essential pending step in fusion roadmaps. Structural materials development, together with research on functional materials capable of sustaining unprecedented power densities during plasma operation in a fusion reactor, have been the subject of decades of worldwide research efforts underpinning the present maturity of the fusion materials research programme.
Fission dynamics within time-dependent Hartree-Fock: boost-induced fission
Goddard, P M; Rios, A
2015-01-01
Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe induced fission processes, using quadrupole boosts in the nuclide $^{240}$Pu as an example. Methods: Quadrupole constrained Hartree-Fock calculations are used to create a potential energy surface. An isomeric state and a state beyond the second barrier peak are excited by means of instantaneous as well as temporally extended gauge boosts with quadrupole shapes. The subsequent deexcitation is studied in a time-dependent Hartree-Fock simulation, with emphasis on fissioned final states. The corresponding fission fragment mass numbers are studied. Results: In general, the energy deposited by the quadrupole boost is quickl...
Energy Partition in n+233U Fission Reaction
Institute of Scientific and Technical Information of China (English)
CHEN; Yong-jing; LIU; Ting-jin; SHU; Neng-chuan
2012-01-01
<正>The partition of the total excitation energy between the fission fragments for the n+233U fission reactions are analyzed with a semi-empirical model, and it is a key point for calculating the prompt fission neutron spectrum, and it is still a long-standing problem for nuclear fission, and attracts more and more attention. With the available experimental data, such as the average total number of emitted neutrons, the
Increased Exploration Capacity Promotes Group Fission in Gregarious Foraging Herbivores
Lardy, Sophie; Fortin, Daniel; Pays, Olivier
2016-01-01
Many gregarious species display rapid fission-fusion dynamics with individuals frequently leaving their groups to reunite or to form new ones soon after. The adaptive value of such ephemeral associations might reflect a frequent tilt in the balance between the costs and benefits of maintaining group cohesion. The lack of information on the short-term advantages of group fission, however, hampers our understanding of group dynamics. We investigated the effect of group fission on area-restricted search, a search tactic that is commonly used when food distribution is spatially autocorrelated. Specifically, we determine if roe deer (Capreolus capreolus) improve key aspects of their extensive search mode immediately after fission. We found that groups indeed moved faster and farther over time immediately after than before fission. This gain was highest for the smallest group that resulted from fission, which was more likely to include the fission’s initiator. Sex of group members further mediated the immediate gain in search capacity, as post-fission groups moved away at farthest rate when they were only comprised of males. Our study suggests that social conflicts during the extensive search mode can promote group fission and, as such, can be a key determinant of group fission-fusion dynamics that are commonly observed in gregarious herbivores. PMID:27907143
Institute of Scientific and Technical Information of China (English)
马续波; 陈义学; 王继亮; 王悦; 韩静茹; 陆道纲
2011-01-01
The hybrid fusion-fission reactor has advantages of breeding of the nuclear fuel and transmutation of the long-life nuclear waste and having inherent safety. Meanwhile, the engineering and technological demand of hybrid reactor is significantly reduced comparing with that of pure fusion reactor. A generating electricity blanket concept using the PWR spent fuel directly was proposed, which was based on ITER parameter level achieved. Different volume fractions of the fuel in blanket enabled to realize a power flattening in the fissile zone. The results show that the peak-to-average power factor becomes less than no power flattening, and the output power of the fuel zone raises more than 21. 7%. At the end of the operation, the maximum fuel enrichment is 5. 23%. The blanket is feasible from the neutronics viewpoint.%聚变裂变混合堆在增殖核燃料、嬗变长寿命核废料及固有安全性等方面具有较大优势,同时,它比纯聚变堆在工程及技术方面要求低,因此较聚变堆更易实现.本工作基于目前国际聚变实验堆(ITER)所能达到的技术水平,提出一种直接利用乏燃料进行发电的聚变裂变混合堆包层概念,利用在不同位置放置不同乏燃料体积分数的方法对燃料增殖区实现了功率展平.计算结果表明:功率展平后的包层功率不均匀系数更小,且包层中燃料区的能量输出要比不展平情况下的能量输出高约21.7％.燃料富集度到运行末期最大可达5.23％.从中子学角度初步论证了该包层的可行性.
Thorium-uranium fission radiography
Haines, E. L.; Weiss, J. R.; Burnett, D. S.; Woolum, D. S.
1976-01-01
Results are described for studies designed to develop routine methods for in-situ measurement of the abundance of Th and U on a microscale in heterogeneous samples, especially rocks, using the secondary high-energy neutron flux developed when the 650 MeV proton beam of an accelerator is stopped in a 42 x 42 cm diam Cu cylinder. Irradiations were performed at three different locations in a rabbit tube in the beam stop area, and thick metal foils of Bi, Th, and natural U as well as polished silicate glasses of known U and Th contents were used as targets and were placed in contact with mica which served as a fission track detector. In many cases both bare and Cd-covered detectors were exposed. The exposed mica samples were etched in 48% HF and the fission tracks counted by conventional transmitted light microscopy. Relative fission cross sections are examined, along with absolute Th track production rates, interaction tracks, and a comparison of measured and calculated fission rates. The practicality of fast neutron radiography revealed by experiments to data is discussed primarily for Th/U measurements, and mixtures of other fissionable nuclei are briefly considered.
On fusion driven systems (FDS) for transmutation
Energy Technology Data Exchange (ETDEWEB)
Aagren, O (Uppsala Univ., Aangstroem laboratory, div. of electricity, Uppsala (Sweden)); Moiseenko, V.E. (Inst. of Plasma Physics, National Science Center, Kharkov Inst. of Physics and Technology, Kharkov (Ukraine)); Noack, K. (Forschungszentrum Dresden-Rossendorf (Germany))
2008-10-15
This report gives a brief description of ongoing activities on fusion driven systems (FDS) for transmutation of the long-lived radioactive isotopes in the spent nuclear waste from fission reactors. Driven subcritical systems appears to be the only option for efficient minor actinide burning. Driven systems offer a possibility to increase reactor safety margins. A comparatively simple fusion device could be sufficient for a fusion-fission machine, and transmutation may become the first industrial application of fusion. Some alternative schemes to create strong fusion neutron fluxes are presented
Energy Technology Data Exchange (ETDEWEB)
Gelles, D.S.
1995-03-01
Fusion energy production has an inherent advantage over fission: a fuel supply with reduced long term radioactivity. One of the leading candidate materials for structural applications in a fusion reactor is a tungsten stabilized 9% chromium Martensitic steel. This alloy class is being considered because it offers the opportunity to maintain that advantage in the reactor structure as well as provide good high temperature strength and radiation induced swelling and embrittlement resistance. However, calculations indicate that to obtain acceptable radioactivity levels within 500 years after service, clean steel will be required because the niobium impurity levels must be kept below about 2 appm and nickel, molybdenum, nitrogen, copper, and aluminum must be intentionally restricted. International efforts are addressing the problems of clean steel production. Recently, a 5,000 kg heat was vacuum induction melted in Japan using high purity commercial raw materials giving niobium levels less than 0.7 appm. This paper reviews the need for reduced long term radioactivity, defines the advantageous properties of the tungsten stabilized Martensitic steel class, and describes the international efforts to produce acceptable clean steels.
SPIDER Progress Towards High Resolution Correlated Fission Product Data
Shields, Dan; Meierbachtol, Krista; Tovesson, Fredrik; Arnold, Charles; Blackeley, Rick; Bredeweg, Todd; Devlin, Matt; Hecht, Adam; Jandel, Marian; Jorgenson, Justin; Nelson, Ron; White, Morgan; Spider Team
2014-09-01
The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) is under development with the goal of obtaining high-resolution, high-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (ν), and total kinetic energy (TKE). A detailed description of the prototype SPIDER detector components will be presented. Characterization measurements with alpha and spontaneous fission sources will also be discussed. LA-UR-14-24875. The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) is under development with the goal of obtaining high-resolution, high-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (ν), and total kinetic energy (TKE). A detailed description of the prototype SPIDER detector components will be presented. Characterization measurements with alpha and spontaneous fission sources will also be discussed. LA-UR-14-24875. This work is in part supported by LANL Laboratory Directed Research and Development Projects 20110037DR and 20120077DR.
Inclusive spectra of hadrons created by color tube fission; 1, Probability of tube fission
Gedalin, E V
1997-01-01
The probability of color tube fission that includes the tube surface small oscillation corrections is obtained with pre-exponential factor accuracy on the basis of previously constructed color tube model. Using these expressions the probability of the tube fission in $n$ point is obtained that is the basis for calculation of inclusive spectra of produced hadrons.
Institute of Scientific and Technical Information of China (English)
刘金超; FDS团队; 金鸣; 王明煌; 蒋洁琼; 王国忠; 邱岳峰; 宋婧; 邹俊; 吴宜灿
2011-01-01
FDS-MFX(Multi-Functional eXperimental fusion-fission hybrid reactor)是一个基于现实可行技术的多功能聚变裂变混合实验堆概念,分3个阶段相继开展实验研究,分别采用纯氚增殖包层、铀燃料包层和乏燃料包层.本文重点对其中铀燃料包层后期阶段中高浓缩铀模块的摆放方式和尺寸进行优化,给出一个区平均最大功率密度约为100 MW/m3,235U装料量约为1 t,氚增殖率为1.05的三维初步中子学方案.%A multi-functional experimental fusion-fission hybrid reactor concept named FDS-MFX , which is based on viable fusion and fission technologies, has been proposed. Three-stage tests will be carried out successively, in which the tritium breeding blanket, uranium-fueled blanket and spent-fuel-fueled blanket will be utilized respectively. In this paper,the design optimization for the layout and the size of high enriched uranium modules inlater stage of uranium-fueled blanket has been performed.Finally,proposing a preliminarythree-dimension neutronies design with maximum average Power Density(Pdmax)100 MW/m3,loaded mass of the 235U 1 000 kg and TBR(Tritium Breeding Ratio)1.05.
Chopra, Sahila; Kaur, Arshdeep; Gupta, Raj K.
2015-03-01
After a successful attempt to define and determine recently the compound nucleus (CN) fusion/ formation probability PCN within the dynamical cluster-decay model (DCM), we introduce and estimate here for the first time the survival probability Psurv of CN against fission, again within the DCM. Calculated as the dynamical fragmentation process, Psurv is defined as the ratio of the evaporation residue (ER) cross section σER and the sum of σER and fusion-fission (ff) cross section σff, the CN formation cross section σCN, where each contributing fragmentation cross section is determined in terms of its formation and barrier penetration probabilities P0 and P . In DCM, the deformations up to hexadecapole and "compact" orientations for both in-plane (coplanar) and out-of-plane (noncoplanar) configurations are allowed. Some 16 "hot" fusion reactions, forming a CN of mass number ACN˜100 to superheavy nuclei, are analyzed for various different nuclear interaction potentials, and the variation of Psurv on CN excitation energy E*, fissility parameter χ , CN mass ACN, and Coulomb parameter Z1Z2 is investigated. Interesting results are that three groups, namely, weakly fissioning, radioactive, and strongly fissioning superheavy nuclei, are identified with Psurv, respectively, ˜1 ,˜10-6 , and ˜10-10 . For the weakly fissioning group (100 PCN belongs to the strongly fissioning superheavy group, Psurv belongs to weakly fissioning nuclei; for Pt* isotopes, the inverse of all the compound systems studied, both PCN and Psurv decrease with the increase of E*; for 213 ,215 ,217Fr* nuclei, though fissility χ is nearly the same, Psurv for 213 ,217Fr* is of the same order as for weakly fissioning nuclei, but that for 215Fr* is of the order of radioactive nuclei. Apparently, further calculations are called for.
Systematic study of anomalous fragment anisotropies in subbarrier complete fusion—fission reactions
Institute of Scientific and Technical Information of China (English)
ZhangHuan－Qiao; LiuZu－Hua; 等
1997-01-01
The complete fusion-fission is separated from the transter-induced-fission with the fragment folding angle technique.The cross sections and fragment angular distributions for the complete fusion-fission reactions of 11B+ 238U(237Np),237NP,16O+232Th(238U) and 19F+232Th at near-and sub-barrier energies have been measured.The present fusion and fission standard models can reproduces both the excitation functions and the fragment anisotropies for the systems of 11B+238U(237Np)and 12C+237Np;but fail to explain both the experimental data for the other 3 systems simultaneously,The evidence of the entrance-channel dependence of fission-fragment anisotropies is revealsed by comparison of the 11B+237NP and 16O+232Th data.Based on the observations a new version model of preequilibrium fission is put forward to explain the anomaly.
混合堆增殖钍基燃料组件中子学分析%Neutronics Calculation of Fusion-Fission Hybrid Breeding Thorium Fuel Assembly
Institute of Scientific and Technical Information of China (English)
马续波; 陈义学; 全国萍; 王悦; 韩静茹; 陆道纲
2012-01-01
A preliminary comparative study of the physical properties among 17×17 fuel assembly in PWRs for prototype between uranium assembly and hybrid breeding thorium-based assembly has been investigated respectively using the DRAGON software. The parameters such as fuel temperature coefficient, moderator temperature coefficient and that variation as a function of operation period have been investigated. Results show that the neutron properties of uranium-based assembly and hybrid breeding thorium-based assembly are similitude, but MA mass of hybrid breeding thorium-based assembly is evidently less than those of the uranium assembly.%采用压水堆17×17燃料组件模型,用燃料组件参数计算程序DRAGON分别对混合堆增殖钍燃料组件和全铀组件的中子学特性进行了研究,分析组件的燃料温度系数、慢化剂温度系数及其与燃耗的关系.计算结果表明,混合堆增殖钍燃料组件和全铀组件的中子特性相似,但钍燃料组件中的乏燃料组件中的次锕系核素(MA)的含量明显减少.
Theoretical Description of the Fission Process
Energy Technology Data Exchange (ETDEWEB)
Witold Nazarewicz
2009-10-25
Advanced theoretical methods and high-performance computers may finally unlock the secrets of nuclear fission, a fundamental nuclear decay that is of great relevance to society. In this work, we studied the phenomenon of spontaneous fission using the symmetry-unrestricted nuclear density functional theory (DFT). Our results show that many observed properties of fissioning nuclei can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. From the calculated collective potential and collective mass, we estimated spontaneous fission half-lives, and good agreement with experimental data was found. We also predicted a new phenomenon of trimodal spontaneous fission for some transfermium isotopes. Our calculations demonstrate that fission barriers of excited superheavy nuclei vary rapidly with particle number, pointing to the importance of shell effects even at large excitation energies. The results are consistent with recent experiments where superheavy elements were created by bombarding an actinide target with 48-calcium; yet even at high excitation energies, sizable fission barriers remained. Not only does this reveal clues about the conditions for creating new elements, it also provides a wider context for understanding other types of fission. Understanding of the fission process is crucial for many areas of science and technology. Fission governs existence of many transuranium elements, including the predicted long-lived superheavy species. In nuclear astrophysics, fission influences the formation of heavy elements on the final stages of the r-process in a very high neutron density environment. Fission applications are numerous. Improved understanding of the fission process will enable scientists to enhance the safety and reliability of the nation’s nuclear stockpile and nuclear reactors. The deployment of a fleet of safe and efficient advanced reactors, which will also minimize radiotoxic
An overview of the recent results on fission dynamics from the NAND facility
Indian Academy of Sciences (India)
B R Behera
2015-08-01
This paper summarizes the results of some of the recent fusion–fission experiments carried out at the National Array of Neutron Detectors (NAND) Phase-01 installed at the Pelletron+LINAC accelerator facility of Inter-University Accelerator Centre (IUAC), New Delhi. Pre-scission neutron multiplicity excitation functions are measured for the 213,215,217Fr, 210,212,214,216Rn and 206,210Po compound nuclei populated through the fusion of the 19F+194,196,198Pt, 16,18O+194,198Pt and 12C+194,198Pt systems, respectively. Pre-scission neutron yields from these reactions are compared with the extensive statistical model calculations to look for the effects due to the compound nucleus shell closure, / ratio of the compound nucleus, magnitude of the saddle-point shell corerction and fission time-scale.
Modeling Fission Product Sorption in Graphite Structures
Energy Technology Data Exchange (ETDEWEB)
Szlufarska, Izabela [University of Wisconsin, Madison, WI (United States); Morgan, Dane [University of Wisconsin, Madison, WI (United States); Allen, Todd [University of Wisconsin, Madison, WI (United States)
2013-04-08
The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high- temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission
Fission and Properties of Neutron-Rich Nuclei
Hamilton, Joseph H.; Ramayya, A. V.; Carter, H. K.
2008-08-01
Opening session. Nuclear processes in stellar explosions / M. Wiescher. In-beam [symbol]-ray spectroscopy of neutron-rich nuclei at NSCL / A. Gade -- Nuclear structure I. Shell-model structure of neutron-rich nuclei beyond [symbol]Sn / A. Covello ... [et al.]. Shell structure and evolution of collectivity in nuclei above the [symbol]Sn core / S. Sarkar and M. S. Sarkar. Heavy-ion fusion using density-constrained TDHF / A. S. Umar and V. E. Oberacker. Towards an extended microscopic theory for upper-fp shell nuclei / K. P. Drumev. Properties of the Zr and Pb isotopes near the drip-line / V. N. Tarasov ... [et al.]. Identification of high spin states in [symbol] Cs nuclei and shell model calculations / K. Li ... [et al.]. Recent measurements of spherical and deformed isomers using the Lohengrin fission-fragment spectrometer / G. S. Simpson ... [et al.] -- Nuclear structure II. Nuclear structure investigation with rare isotope spectroscopic investigations at GSI / P. Boutachkov. Exploring the evolution of the shell structures by means of deep inelastic reactions / G. de Anaelis. Probing shell closures in neutron-rich nuclei / R. Krücken for the S277 and REX-ISOLDEMINIBALL collaborations. Structure of Fe isotopes at the limits of the pf-shell / N. Hoteling ... [et al.]. Spectroscopy of K isomers in shell-stabilized trans-fermium nuclei / S. K. Tandel ... [et al.] -- Radioactive ion beam facilities. SPIRAL2 at GANIL: a world leading ISOL facility for the next decade / S. Gales. New physics at the International Facility for Antiproton and Ion Research (FAIR) next to GSI / I. Augustin ... [et al.]. Radioactive beams from a high powered ISOL system / A. C. Shotter. RlKEN RT beam factory / T. Motobayashi. NSCL - ongoing activities and future perspectives / C. K. Gelbke. Rare isotope beams at Argonne / W. F. Henning. HRIBF: scientific highlights and future prospects / J. R. Beene. Radioactive ion beam research done in Dubna / G. M. Ter-Akopian ... [et al.] -- Fission I
Fission induced by nucleons at intermediate energies
Meo, Sergio Lo; Massimi, Cristian; Vannini, Gianni; Ventura, Alberto
2014-01-01
Monte Carlo calculations of fission of actinides and pre-actinides induced by protons and neutrons in the energy range from 100 MeV to 1 GeV are carried out by means of a recent version of the Li\\`ege Intranuclear Cascade Model, INCL++, coupled with two different evaporation-fission codes, GEMINI++ and ABLA07. In order to reproduce experimental fission cross sections, model parameters are usually adjusted on available (p,f) cross sections and used to predict (n,f) cross sections for the same isotopes.
Teller, E.
1958-07-03
Applications of thermonuclear energy for peaceful and constructive purposes are surveyed. Developments and problems in the release and control of fusion energy are reviewed. It is pointed out that the future of thermonuclear power reactors will depend upon the construction of a machine that produces more electric energy than it consumes. The fuel for thermonuclear reactors is cheap and practically inexhaustible. Thermonuclear reactors produce less dangerous radioactive materials than fission reactors and, when once brought under control, are not as likely to be subject to dangerous excursions. The interaction of the hot plasma with magnetic fields opens the way for the direct production of electricity. It is possible that explosive fusion energy released underground may be harnessed for the production of electricity before the same feat is accomplished in controlled fusion processes. Applications of underground detonations of fission devices in mining and for the enhancement of oil flow in large low-specific-yield formations are also suggested.
Cross Sections Calculations of ( d, t) Nuclear Reactions up to 50 MeV
Tel, E.; Yiğit, M.; Tanır, G.
2013-04-01
In nuclear fusion reactions two light atomic nuclei fuse together to form a heavier nucleus. Fusion power is the power generated by nuclear fusion processes. In contrast with fission power, the fusion reaction processes does not produce radioactive nuclides. The fusion will not produce CO2 or SO2. So the fusion energy will not contribute to environmental problems such as particulate pollution and excessive CO2 in the atmosphere. Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production is still believed to be unlikely before 2050. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. In the fusion reactor, tritium self-sufficiency must be maintained for a commercial power plant. Therefore, for self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of ( d, t) nuclear reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. Since the experimental data of charged particle induced reactions are scarce, self-consistent calculation and analyses using nuclear theoretical models are very important. In this study, ( d, t) cross sections for target nuclei 19F, 50Cr, 54Fe, 58Ni, 75As, 89Y, 90Zr, 107Ag, 127I, 197Au and 238U have been investigated up to 50 MeV deuteron energy. The excitation functions for ( d, t) reactions have been calculated by pre-equilibrium reaction mechanism. Calculation results have been also compared with the available measurements in
Fusion using radioactive ion beams
Indian Academy of Sciences (India)
A M Vinodkumar
2010-07-01
The capture-fission cross-section is measured for the collision of the massive nucleus 132Sn with 96Zr at near-barrier energies and compared with the collision of 124Sn with 96Zr. This study gives insight into fusion enhancement and hindrance in systems involving neutron-rich nuclei. The dinuclear system model (DNS) calculations describe the excitation function reasonably well and if we use the barrier heights predicted by this model we can conclude that fusion hindrance (represented by extra push energy) is greater for the more neutron-rich systems. The fusion excitation function for 9Li+70Zn and 9Li+208Pb systems are measured for near-barrier energies using ISAC1 and ISAC2 Facilities at TRIUMF. The -emitting evaporation residues (211−214At) are stopped in the 208Pb target and their decay is measured. The measured excitation function shows evidence for large enhancements in the sub-barrier energies, which is not accounted by current theoretical models. Suppression of the above-barrier cross-section with respect to these theoretical models are also seen.
Energy Technology Data Exchange (ETDEWEB)
Laget, M
2007-10-15
While the existence of an island of stability beyond Z=110 is theoretically acquired, the location of this island ranges from Z=114 to Z=126 depending on models. In this work, the stability of super-heavy nuclei is probed through the study of their fission time. The chosen experimental method, the crystal blocking method, is sensitive to the presence of possible long time components in the fission time distribution which indicates a fission mechanism occurring after the formation of a compound nucleus. The blocking dips were therefore constituted for the various products of the reaction U{sup 238} + Ni (6.6 MeV/A) {yields} 120, the experimental set-up allowing us to clearly identify and select the reaction mechanisms. The comparison of the blocking dip constituted for quasi-elastic scattering events with the one obtained for the fission fragments of a Z=120, combined with the study of kinematical properties of these fission fragments, give evidences of the existence of very long fission times (> 10{sup -18} s) only compatible with a fusion-fission mechanism implying a non vanishing fission barrier height for Z=120. The second part outlines microscopic calculations of fission barrier heights, carried out in the framework of the finite temperature of the Hartree-Fock-Bogoliubov (HFB) theory. Because of the progressive vanishing of the pairing correlation with T, which happens differently at the ground state and at the top of the barrier, B{sub f} first grows until T {approx_equal} 0.8 MeV before dropping with T owing to shell-effects damping with temperature. (author)
MCNP6 Fission Multiplicity with FMULT Card
Energy Technology Data Exchange (ETDEWEB)
Wilcox, Trevor [Los Alamos National Laboratory; Fensin, Michael Lorne [Los Alamos National Laboratory; Hendricks, John S. [Los Alamos National Laboratory; James, Michael R. [Los Alamos National Laboratory; McKinney, Gregg W. [Los Alamos National Laboratory
2012-06-18
With the merger of MCNPX and MCNP5 into MCNP6, MCNP6 now provides all the capabilities of both codes allowing the user to access all the fission multiplicity data sets. Detailed in this paper is: (1) the new FMULT card capabilities for accessing these different data sets; (2) benchmark calculations, as compared to experiment, detailing the results of selecting these separate data sets for thermal neutron induced fission on U-235.
Fifty years of nuclear fission: Nuclear data and measurements series
Energy Technology Data Exchange (ETDEWEB)
Lynn, J.E.
1989-06-01
This report is the written version of a colloquium first presented at Argonne National Laboratory in January 1989. The paper begins with an historical preamble about the events leading to the discovery of nuclear fission. This leads naturally to an account of early results and understanding of the fission phenomena. Some of the key concepts in the development of fission theory are then discussed. The main theme of this discussion is the topography of the fission barrier, in which the interplay of the liquid-drop model and nucleon shell effects lead to a wide range of fascinating phenomena encompassing metastable isomers, intermediate-structure effects in fission cross-sections, and large changes in fission product properties. It is shown how study of these changing effects and theoretical calculations of the potential energy of the deformed nucleus have led to broad qualitative understanding of the nature of the fission process. 54 refs., 35 figs.
Characterization of the scission point from fission-fragment velocities
Caamaño, M; Delaune, O; Schmidt, K -H; Schmitt, C; Audouin, L; Bacri, C -O; Benlliure, J; Casarejos, E; Derkx, X; Fernández-Domínguez, B; Gaudefroy, L; Golabek, C; Jurado, B; Lemasson, A; Ramos, D; Rodríguez-Tajes, C; Roger, T; Shrivastava, A
2015-01-01
The isotopic-yield distributions and kinematic properties of fragments produced in transfer-induced fission of 240Pu and fusion-induced fission of 250Cf, with 9 MeV and 45 MeV of excitation energy respectively, were measured in inverse kinematics with the spectrometer VAMOS. The kinematic properties of identified fission fragments allow to derive properties of the scission configuration such as the distance between fragments, the total kinetic energy, the neutron multiplicity, the total excitation energy, and, for the first time, the proton- and neutron-number sharing during the emergence of the fragments. These properties of the scission point are studied as functions of the fragment atomic number. The correlation between these observables, gathered in one single experiment and for two different fissioning systems at different excitation energies, give valuable information for the understanding and modeling of the fission process.
Nuclear fission problem and Langevin equation
Directory of Open Access Journals (Sweden)
M Sakhaee
2011-12-01
Full Text Available A combined dynamical and statistical model for fission was employed in our calculation. There is no doubt that a Langevin description plus a Monte Carlo treatment of the evaporation processes provide the most adequate dynamical description. In this paper, we would consider a strongly shaped dependent friction force and we use the numerical method rather than the analytical one. The objective of this article is to calculate the time dependent fission widths of the 224Th nucleus. The fission widths were calculated with both chaos-weighted wall friction (CWWF and wall friction (WF dissipations. The calculations are repeated for 100000 trajectories. The result was compared to the others' work. We use nuclear elongation coordinate with time and it is necessary to repeat the small steps many times to improve the accuracy.
Fission barriers and probabilities of spontaneous fission for elements with Z$\\geq$100
Baran, A; Reinhard, P -G; Robledo, L M; Staszczak, A; Warda, M
2015-01-01
This is a short review of methods and results of calculations of fission barriers and fission half-lives of even-even superheavy nuclei. An approvable agreement of the following approaches is shown and discussed: The macroscopic-microscopic approach based on the stratagem of the shell correction to the liquid drop model and a vantage point of microscopic energy density functionals of Skyrme and Gogny type selfconsistently calculated within Hartree-Fock-Bogoliubov method. Mass parameters are calculated in the Hartree-Fock-Bogoliubov cranking approximation. A short part of the paper is devoted to the nuclear fission dynamics. We also discuss the predictive power of Skyrme functionals applied to key properties of the fission path of $^{266}$Hs. It applies the standard techniques of error estimates in the framework of a $\\chi^2$ analysis.
Modelling with uncertainties: The role of the fission barrier
Directory of Open Access Journals (Sweden)
Lü Hongliang
2013-12-01
Full Text Available Fission is the dominant decay channel of super-heavy elements formed in heavy ions collisions. The probability of synthesizing heavy or super-heavy nuclei in fusion-evaporation reactions is then very sensitive to the height of their fission barriers. This contribution will firstly address the influence of theoretical uncertainty on excitation functions. Our second aim is to investigate the inverse problem, i.e., what information about the fission barriers can be extracted from excitation functions? For this purpose, Bayesian methods have been used with a simplified toy model.
Modelling animal group fission using social network dynamics.
Sueur, Cédric; Maire, Anaïs
2014-01-01
Group life involves both advantages and disadvantages, meaning that individuals have to compromise between their nutritional needs and their social links. When a compromise is impossible, the group splits in order to reduce conflict of interests and favour positive social interactions between its members. In this study we built a dynamic model of social networks to represent a succession of temporary fissions involving a change in social relations that could potentially lead to irreversible group fission (i.e. no more group fusion). This is the first study that assesses how a social network changes according to group fission-fusion dynamics. We built a model that was based on different parameters: the group size, the influence of nutritional needs compared to social needs, and the changes in the social network after a temporary fission. The results obtained from this theoretical data indicate how the percentage of social relation transfer, the number of individuals and the relative importance of nutritional requirements and social links influence the average number of days before irreversible fission occurs. The greater the nutritional needs and the higher the transfer of social relations during temporary fission, the fewer days will be observed before an irreversible fission. It is crucial to bridge the gap between the individual and the population level if we hope to understand how simple, local interactions may drive ecological systems.
Negative Pion Induced Fission with Heavy Target Nuclei
Institute of Scientific and Technical Information of China (English)
G. Sher; Mukhtar A. Rana; S. Manzoor; M. I. Shahzad
2011-01-01
We investigate fission induced by negative pions in copper and bismuth targets using CR-39 dielectric track detectors. The target-detector assemblies in Air-geometric configuration were exposed at the AGS facility of Brookhaven National Laboratory, USA. The exposed detectors were chemically etched under appropriate etching conditions and scanned to collect data in the form of fission fragments tracks produced as a result of interaction of pions with the target nuclei. Using the track counts, the experimental fission cross sections for copper and bismuth have been measured at energies of 500, 672, 1068 and 1665 MeV and compared with the calculation using the Cascade-Exciton Model code (CEM95). The values of fission probability based on experimental fission cross-sections have been compared with the theoretically calculated values of fission probabilities obtained using the CEM95 code. Good agreement is observed between the measured and computed results.
Basics of Fusion-Fissison Research Facility (FFRF) as a Fusion Neutron Source
Energy Technology Data Exchange (ETDEWEB)
Leonid E. Zakharov
2011-06-03
FFRF, standing for the Fusion-Fission Research Facility represents an option for the next step project of ASIPP (Hefei, China) aiming to a first fusion-fission multifunctional device [1]. FFRF strongly relies on new, Lithium Wall Fusion plasma regimes, the development of which has already started in the US and China. With R/a=4/1m/m, Ipl=5 MA, Btor=4-6 T, PDT=50- 100 MW, Pfission=80-4000MW, 1 m thick blanket, FFRF has a unique fusion mission of a stationary fusion neutron source. Its pioneering mission of merging fusion and fission consists in accumulation of design, experimental, and operational data for future hybrid applications.
Revision of the JENDL FP Fission Yield Data
Directory of Open Access Journals (Sweden)
Katakura Jun-ichi
2016-01-01
Full Text Available Some fission yields data of JENDL FP Fission Yields Data File 2011 (JENDL/FPY-2011 revealed inadequacies when applied to delayed neutron related subjects. The sensitivity analyses of decay heat summation calculations also showed some problems. From these results the fission yields of JENDL/FPY-2011 have been revised. The present report describes the revision of the yield data by emphasizing the sensitivity analyses.
Chushnyakova, M. V.; Bhattacharya, R.; Gontchar, I. I.
2014-07-01
Background: In our previous paper [Gontchar et al., Phys. Rev. C 89, 034601 (2014), 10.1103/PhysRevC.89.034601] we have calculated the capture (fusion) excitation functions for several reactions with O16,Si28, and S32 nuclei as the projectiles and Zr92,Sm144, and Pb208 nuclei as the targets. These calculations were performed by using our fluctuation-dissipation trajectory model based on the double-folding approach with the density-dependent M3Y NN forces that include the finite range exchange part. For the nuclear matter density the Hartree-Fock approach with the SKP coefficient set that includes the tensor interaction was applied. It was found that for most of the reactions induced by O16 the calculated cross sections cannot be brought into agreement with the data. This suggested that the deviation in the calculated nuclear density for O16 from the experimental one was crucial. Method: The SKX parameter set is used to obtain the nuclear densities. Reactions with C12 and S36 as the projectiles and Pb204 as the target are included in the analysis in addition to those of the previous paper. Only data that correspond to the collision energy Ec.m.>1.1UB0 (UB0 is the s-wave fusion barrier height) are included in the analysis. The radial friction strength KR is used as the individual adjustable parameter for each reaction. Results: For all 13 reactions (91 points) it is possible to reach an agreement with the experimental fusion cross sections within 10%. Only at ten points does the deviation exceed 5%. The value of KR, which provides the best agreement with the data in general, decreases as the system gets heavier in accord with the previous paper [Gontchar et al., Phys. Rev. C 89, 034601 (2014), 10.1103/PhysRevC.89.034601]. A universal analytical approximation for the dependence of KR upon the Coulomb barrier height is found. Conclusions: The developed model is able to reproduce the above-barrier portion of the fusion excitation function within 5% with a probability of
Energy Technology Data Exchange (ETDEWEB)
Felou Youmbi, V
1996-12-11
Fission cross sections of {sup 9,11}Be + {sup 238}U systems are measured in the energy range of the coulomb barrier. These measures allow the study of neutron halo effect on sub coulombian fusion. {sup 9,11}Be beams are obtained by fragmentation at the GANIL facilities. The fusion between incident particle and the target nucleus leads to a compound nucleus which disappears by fission. The FUSION detector is used to detect the fission fragments by coincidence. We present some calculations of potential barriers by using Wong formula. The nucleus-nucleus interaction is simulated by a double convolution between the nucleus density and the effective M3Y interaction. In a more realistic framework ECIS94 code calculates the fusion cross section by using a coupling formalism. Theoretical values and experimental results are compared. We get a good agreement for {sup 9}Be + {sup 238}U system and an unusual behaviour appears for {sup 11}Be + {sup 238}U system 116 refs.
Fuel cycle for a fusion neutron source
Ananyev, S. S.; Spitsyn, A. V.; Kuteev, B. V.
2015-12-01
The concept of a tokamak-based stationary fusion neutron source (FNS) for scientific research (neutron diffraction, etc.), tests of structural materials for future fusion reactors, nuclear waste transmutation, fission reactor fuel production, and control of subcritical nuclear systems (fusion-fission hybrid reactor) is being developed in Russia. The fuel cycle system is one of the most important systems of FNS that provides circulation and reprocessing of the deuterium-tritium fuel mixture in all fusion reactor systems: the vacuum chamber, neutral injection system, cryogenic pumps, tritium purification system, separation system, storage system, and tritium-breeding blanket. The existing technologies need to be significantly upgraded since the engineering solutions adopted in the ITER project can be only partially used in the FNS (considering the capacity factor higher than 0.3, tritium flow up to 200 m3Pa/s, and temperature of reactor elements up to 650°C). The deuterium-tritium fuel cycle of the stationary FNS is considered. The TC-FNS computer code developed for estimating the tritium distribution in the systems of FNS is described. The code calculates tritium flows and inventory in tokamak systems (vacuum chamber, cryogenic pumps, neutral injection system, fuel mixture purification system, isotope separation system, tritium storage system) and takes into account tritium loss in the fuel cycle due to thermonuclear burnup and β decay. For the two facility versions considered, FNS-ST and DEMO-FNS, the amount of fuel mixture needed for uninterrupted operation of all fuel cycle systems is 0.9 and 1.4 kg, consequently, and the tritium consumption is 0.3 and 1.8 kg per year, including 35 and 55 g/yr, respectively, due to tritium decay.
Ongena, J.; Koch, R.; Wolf, R.; Zohm, H.
2016-05-01
Our modern society requires environmentally friendly solutions for energy production. Energy can be released not only from the fission of heavy nuclei but also from the fusion of light nuclei. Nuclear fusion is an important option for a clean and safe solution for our long-term energy needs. The extremely high temperatures required for the fusion reaction are routinely realized in several magnetic-fusion machines. Since the early 1990s, up to 16 MW of fusion power has been released in pulses of a few seconds, corresponding to a power multiplication close to break-even. Our understanding of the very complex behaviour of a magnetized plasma at temperatures between 150 and 200 million °C surrounded by cold walls has also advanced substantially. This steady progress has resulted in the construction of ITER, a fusion device with a planned fusion power output of 500 MW in pulses of 400 s. ITER should provide answers to remaining important questions on the integration of physics and technology, through a full-size demonstration of a tenfold power multiplication, and on nuclear safety aspects. Here we review the basic physics underlying magnetic fusion: past achievements, present efforts and the prospects for future production of electrical energy. We also discuss questions related to the safety, waste management and decommissioning of a future fusion power plant.
Parone, Philippe A.; Sandrine Da Cruz; Daniel Tondera; Yves Mattenberger; James, Dominic I.; Pierre Maechler; François Barja; Jean-Claude Martinou
2008-01-01
Mitochondria form a highly dynamic tubular network, the morphology of which is regulated by frequent fission and fusion events. However, the role of mitochondrial fission in homeostasis of the organelle is still unknown. Here we report that preventing mitochondrial fission, by down-regulating expression of Drp1 in mammalian cells leads to a loss of mitochondrial DNA and a decrease of mitochondrial respiration coupled to an increase in the levels of cellular reactive oxygen species (ROS). At t...
Edwards, E. R.; Cassata, W. S.; Velsko, C. A.; Yeamans, C. B.; Shaughnessy, D. A.
2016-11-01
Precisely-known fission yield distributions are needed to determine a fissioning isotope and the incident neutron energy in nuclear security applications. 14 MeV neutrons from DT fusion at the National Ignition Facility induce fission in depleted uranium contained in the target assembly hohlraum. The fission yields of Kr isotopes (85m, 87, 88, and 89) are measured relative to the cumulative yield of 88Kr and compared to previously tabulated values. The results from this experiment and England and Rider are in agreement, except for the 85mKr/88Kr ratio, which may be the result of incorrect nuclear data.
Fission Measurements with Dance
Jandel, M.; Bredeweg, T. A.; Fowler, M. M.; Bond, E. M.; Chadwick, M. B.; Clement, R. R.; Couture, A.; O'Donnell, J. M.; Haight, R. C.; Keksis, A. L.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Agvaanluvsan, U.; Dashdorj, D.; Macri, R. A.; Parker, W. E.; Wilk, P. A.; Wu, C. Y.; Becker, J. A.; Angell, C. T.; Tonchev, A. P.; Baker, J. D.
2008-08-01
Neutron capture cross section measurements on actinides are complicated by the presence of neutron-induced fission. An efficient fission tagging detector used in coincidence with the Detector for Advanced Neutron Capture Experiments (DANCE) provides a powerful tool in undertaking simultaneous measurements of (n,γ) and (n,f) cross sections. Preliminary results on 235U(n,γ) and (n,f) and 242mAm(n,f) cross sections measured with DANCE and a custom fission-tagging parallel plate avalanche counter (PPAC) are presented. Additional measurements of γ-ray cluster multiplicity distributions for neutron-induced fission of 235U and 242mAm and spontaneous fission of 252Cf are shown, as well as γ-ray energy and average γ-ray energy distributions.
A new approach to prompt fission neutron TOF data treatment
Zeynalov, Sh.; Zeynalova, O. V.; Hambsch, F.-J.; Oberstedt, S.
The prompt neutron emission in spontaneous fission of 252Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. A new mathematical approach, applicable to single events, was developed for prompt fission neutron (PFN) time-offlight distribution unfolding. The main goal was to understand the reasons of the long existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of the fission fragments (FF). Since the 252Cf (sf) reaction is one of the main references for nuclear data the understanding of the PFN emission mechanism is very important both for nuclear fission theory and nuclear data. The experimental data were taken with a twin Frisch-grid ionization chamber and a NE213-equivalent neutron detector in an experimental setup similar to the well known work of C. Budtz-Jorgensen and H.-H. Knitter. About 2.5 × 105 coincidences between fission fragment (FF) and neutron detector response to prompt fission neutron detection have been registered (∼ 1.6 × 107 of total recorded fission events). Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12-bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. The main goal of this work was a detailed description of the prompt fission neutron treatment.
Alpha decay from fission isomeric states
Energy Technology Data Exchange (ETDEWEB)
Poenaru, D.N.; Ivascu, M. (Institutul de Fizica si Inginerie Nucleara, Bucharest (Romania))
1981-07-01
Alpha-decay half-lives from shape isomeric states of some even-even isotopes of U, Pu and Cm nuclei are calculated by using fission theory in the parametrisation of a spheroid intersected with a sphere. The potential barrier was calculated in the framework of the liquid-drop model of Myers and Swiatecki (Art. Fys.; 36: 343 (1967)) extended for systems with different charge densities; a phenomenological shell correction was introduced. The WKB computed lifetimes are many orders of magnitude longer than that of the spontaneous fission process, in agreement with experimental results.
Angular Anisotropy of the Fission Fragments in the Dinuclear System Mo del
Institute of Scientific and Technical Information of China (English)
T. M. Shneidman; A. V. Andreev; C. Massimi; M. T. Pigni; G. Vannini; A. Ventura; S. G. Zhou
2015-01-01
A theoretical evaluation of the collective excitation spectra of nucleus at large deformations is possible within the framework of the dinuclear system (DNS) model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two-cluster configurations in a dynamical way, permitting exchange of nucleons between clusters. In this work the method of calculation of the potential energy and the collective spectrum of fissioning nucleus at scission point is presented. Combining the DNS model calculations and the statistical model of fission we calculate the angular distribution of fission fragments for the neutron–induced fission of 239Pu.
Hu, S. X.
2014-10-01
Accurate knowledge of the properties of warm dense deuterium/tritium (DT) is essential to reliably design inertial confinement fusion (ICF) implosions. In the warm-dense-matter regime, routinely accessed by low-adiabat ICF implosions, strong-coupling and degeneracy effects play an important role in determining plasma properties. Using first-principles methods of both path-integral Monte Carlo and quantum molecular-dynamics (QMD), we have performed systematic investigation of the equation of state, thermal conductivity, and opacity for DT over a wide range of densities and temperatures. These first-principles properties have been incorporated into our hydrocodes. When compared to hydro simulations using standard plasma models, significant differences in 1-D target performance have been identified for simulations of DT implosions. For low-adiabat (α Administration under Award Number DE-NA0001944.
Metal cluster fission: jellium model and Molecular dynamics simulations
DEFF Research Database (Denmark)
Lyalin, Andrey G.; Obolensky, Oleg I.; Solov'yov, Ilia;
2004-01-01
Fission of doubly charged sodium clusters is studied using the open-shell two-center deformed jellium model approximation and it ab initio molecular dynamic approach accounting for all electrons in the system. Results of calculations of fission reactions Na_10^2+ --> Na_7^+ + Na_3^+ and Na_18^2+ ...
EMISSION OF PHOTONS IN SPONTANEOUS FISSION OF CF-252
VANDERPLOEG, H; BACELAR, JCS; BUDA, A; LAURENS, CR; VANDERWOUDE, A; GAARDHOJE, JJ; ZELAZNY, Z; VANTHOF, G; KALANTARNAYESTANAKI, N
1995-01-01
High energy photon emission accompanying the spontaneous fission of Cf-252 is measured for different mass splits. The photon yields up to an energy of 20 MeV are obtained at several angles relative to the fission direction. Statistical model calculations are used to interpret the data. The photon yi
Fusion and quasifission studies in reactions forming Rn via evaporation residue measurements
Shamlath, A.; Prasad, E.; Madhavan, N.; Laveen, P. V.; Gehlot, J.; Nasirov, A. K.; Giardina, G.; Mandaglio, G.; Nath, S.; Banerjee, Tathagata; Vinodkumar, A. M.; Shareef, M.; Jhingan, A.; Varughese, T.; Kumar, Dvgrks; Devi, P. Sandya; Khushboo, Jisha, P.; Kumar, Neeraj; Hosamani, M. M.; Kailas, S.
2017-03-01
Background: Formation of the compound nucleus (CN) is highly suppressed by quasifission in heavy-ion collisions involving massive nuclei. Though considerable progress has been made in the understanding of fusion-fission and quasifission, the exact dependence of fusion probability on various entrance channel variables is not completely clear, which is very important for the synthesis of new heavy and superheavy elements. Purpose: To study the interplay between fusion and quasifission in reactions forming CN in the boundary region where the fusion probability starts to deviate from unity. Methods: Fusion evaporation residue cross sections were measured for the Si,3028+180Hf reactions using the Hybrid Recoil Mass Analyser at IUAC, New Delhi. Experimental data were compared with data from other reactions forming the same CN or isotopes of the CN. Theoretical calculations were performed using the dinuclear system and statistical models. Results: Reduced evaporation residue cross sections were observed for the reactions studied compared with the asymmetric reaction forming the same CN, indicating fusion suppression in more symmetric systems. The observations are consistent with fission fragment measurements performed in the same or similar systems. Larger ER cross sections are observed with increase in mass in the isotopic chain of the CN. Conclusions: Fusion probability varies significantly with the entrance channels in reactions forming the same CN. While complete fusion occurs for the 16O+194Pt reaction, the fusion probability drops to approximately 60 -70 % for the 30Si+180Hf and less than 20 % for the 50Ti+160Gd reactions, respectively, forming the same CN at similar excitation energies.
Transmutation of silicon carbide in fusion nuclear environment
Energy Technology Data Exchange (ETDEWEB)
Sawan, M.E., E-mail: sawan@engr.wisc.edu [University of Wisconsin-Madison, 1500 Engineering Dr., Madison, WI (United States); Katoh, Y.; Snead, L.L. [Oak Ridge National Laboratory, Oak Ridge, TN (United States)
2013-11-15
The amount and type of metallic transmutants produced in SiC/SiC when used in magnetic (MFE) and inertial (IFE) confinement fusion systems are determined and compared to those obtained following irradiation in fission reactors. Up to ∼1.3% metallic transmutants are generated at the expected lifetime of the fusion blanket. Irradiation in fission reactors to the same fast neutron fluence produces about an order of magnitude lower metallic transmutation products than in fusion systems. While the dominant component in fusion systems is Mg, P is the main transmutation product in fission reactors. The impact on the SiC/SiC properties is not fully understood. The results of this work will help guide irradiation experiments in fission reactors to properly simulate the conditions in fusion systems by possible ion implantation. In addition, the results represent a necessary input for modeling activities aimed at understanding the expected effects on properties.
Technical issues for beryllium use in fusion blanket applications
Energy Technology Data Exchange (ETDEWEB)
McCarville, T.J.; Berwald, D.H.; Wolfer, W.; Fulton, F.J.; Lee, J.D.; Maninger, R.C.; Moir, R.W.; Beeston, J.M.; Miller, L.G.
1985-01-01
Beryllium is an excellent non-fissioning neutron multiplier for fusion breeder and fusion electric blanket applications. This report is a compilation of information related to the use of beryllium with primary emphasis on the fusion breeder application. Beryllium resources, production, fabrication, properties, radiation damage and activation are discussed. A new theoretical model for beryllium swelling is presented.
Analysis of dynamical process with mass distribution of fission fragmentin heavy ion reactions
Directory of Open Access Journals (Sweden)
Aritomo Y.
2010-03-01
Full Text Available We analyzed experimental data obtained for the mass distribution of fission fragments in the reactions 36S+238U and 30Si+238U at several incident energies, which were performed by the JAEA group. Using the dynamical model with the Langevin equation, we precisely investigate the incident energy dependence of the mass distribution of fission fragments. We also consider the fine structures in the mass distribution of fission fragments caused by the nuclear structure at a low incident energy. It is explained why the mass distribution of fission fragments has different features in the two reactions. The fusion cross sections are also estimated.
Fuel cycle for a fusion neutron source
Energy Technology Data Exchange (ETDEWEB)
Ananyev, S. S., E-mail: Ananyev-SS@nrcki.ru; Spitsyn, A. V., E-mail: spitsyn-av@nrcki.ru; Kuteev, B. V., E-mail: Kuteev-BV@nrcki.ru [National Research Center Kurchatov Institute (Russian Federation)
2015-12-15
The concept of a tokamak-based stationary fusion neutron source (FNS) for scientific research (neutron diffraction, etc.), tests of structural materials for future fusion reactors, nuclear waste transmutation, fission reactor fuel production, and control of subcritical nuclear systems (fusion–fission hybrid reactor) is being developed in Russia. The fuel cycle system is one of the most important systems of FNS that provides circulation and reprocessing of the deuterium–tritium fuel mixture in all fusion reactor systems: the vacuum chamber, neutral injection system, cryogenic pumps, tritium purification system, separation system, storage system, and tritium-breeding blanket. The existing technologies need to be significantly upgraded since the engineering solutions adopted in the ITER project can be only partially used in the FNS (considering the capacity factor higher than 0.3, tritium flow up to 200 m{sup 3}Pa/s, and temperature of reactor elements up to 650°C). The deuterium–tritium fuel cycle of the stationary FNS is considered. The TC-FNS computer code developed for estimating the tritium distribution in the systems of FNS is described. The code calculates tritium flows and inventory in tokamak systems (vacuum chamber, cryogenic pumps, neutral injection system, fuel mixture purification system, isotope separation system, tritium storage system) and takes into account tritium loss in the fuel cycle due to thermonuclear burnup and β decay. For the two facility versions considered, FNS-ST and DEMO-FNS, the amount of fuel mixture needed for uninterrupted operation of all fuel cycle systems is 0.9 and 1.4 kg, consequently, and the tritium consumption is 0.3 and 1.8 kg per year, including 35 and 55 g/yr, respectively, due to tritium decay.
Brownian shape motion: Fission fragment mass distributions
Directory of Open Access Journals (Sweden)
Sierk Arnold J.
2012-02-01
Full Text Available It was recently shown that remarkably accurate fission-fragment mass distributions can be obtained by treating the nuclear shape evolution as a Brownian walk on previously calculated five-dimensional potential-energy surfaces; the current status of this novel method is described here.
Monte Carlo simulation based toy model for fission process
Kurniadi, Rizal; Waris, Abdul; Viridi, Sparisoma
2016-09-01
Nuclear fission has been modeled notoriously using two approaches method, macroscopic and microscopic. This work will propose another approach, where the nucleus is treated as a toy model. The aim is to see the usefulness of particle distribution in fission yield calculation. Inasmuch nucleus is a toy, then the Fission Toy Model (FTM) does not represent real process in nature completely. The fission event in FTM is represented by one random number. The number is assumed as width of distribution probability of nucleon position in compound nuclei when fission process is started. By adopting the nucleon density approximation, the Gaussian distribution is chosen as particle distribution. This distribution function generates random number that randomizes distance between particles and a central point. The scission process is started by smashing compound nucleus central point into two parts that are left central and right central points. The yield is determined from portion of nuclei distribution which is proportional with portion of mass numbers. By using modified FTM, characteristic of particle distribution in each fission event could be formed before fission process. These characteristics could be used to make prediction about real nucleons interaction in fission process. The results of FTM calculation give information that the γ value seems as energy.
Late Time Emission of Prompt Fission Gamma Rays
Talou, P; Stetcu, I; Lestone, J P; McKigney, E; Chadwick, M B
2016-01-01
The emission of prompt fission $\\gamma$ rays within a few nanoseconds to a few microseconds following the scission point is studied in the Hauser-Feshbach formalism applied to the deexcitation of primary excited fission fragments. Neutron and $\\gamma$-ray evaporations from fully accelerated fission fragments are calculated in competition at each stage of the decay, and the role of isomers in the fission products, before $\\beta$-decay, is analyzed. The time evolution of the average total $\\gamma$-ray energy, average total $\\gamma$-ray multiplicity, and fragment-specific $\\gamma$-ray spectra, is presented in the case of neutron-induced fission reactions of $^{235}$U and $^{239}$Pu, as well as spontaneous fission of $^{252}$Cf. The production of specific isomeric states is calculated and compared to available experimental data. About 7% of all prompt fission $\\gamma$ rays are predicted to be emitted between 10 nsec and 5 $\\mu$sec following fission, in the case of $^{235}$U and $^{239}$Pu $(n_{\\rm th},f)$ reactio...
Evaluation of Nuclear Fission Barrier Parameters for 17 Nuclei
Institute of Scientific and Technical Information of China (English)
2001-01-01
As well know that modern nuclear installations and applications have reached a high degree of sophistication. The effective safe and economical design of these technologies require detailed and reliable design calculations. The accuracy of these calculations is largely determined by the accuracy of the basic nuclear and atomic input parameters. In order to meet the needs on high energy fission cross section, fission spectra in waste disposal, transmutation, radioactive beams physics and so on, 17 nuclei fission barrier parameters were collected from the literature based on different experiments and
Prompt fission neutron emission: Problems and challenges
Directory of Open Access Journals (Sweden)
Hambsch F.-J.
2013-12-01
Full Text Available This paper presents some of the challenges ahead of us even after 75 years of the discovery of the fission process and large progress made since then. The focus is on application orientation, which requires improved measurements on fission cross-sections and neutron and γ-ray multiplicities. Experimental possibilities have vastly improved the past decade leading to developments of highly sophisticated detector systems and the use of digital data acquisition and signal processing. The development of innovative fast nuclear reactor technology needs improved respective nuclear data. Advancements in theoretical modelling also require better experimental data. Theory has made progress in calculating fission fragment distributions (i.e. GEF code as well as prompt neutron and γ-ray emission to catch up with the improved experiments.
The Quest for Fusion at the National Ignition Facility
Hartouni, Edward
2017-01-01
Arthur Eddington speculated in 1920 on the internal constitution of stars and described the possibility of nuclear fusion based on the then new results from special relativity and measurements of light nuclei masses. By 1929 Atkinson and Houtermans worked out the calculations for nuclear fusion in stars and initiating nuclear astrophysics. All of these sciences were pressed into service during the World War II, and the applications developed, particularly under the auspices of the Manhattan Project provided both weapons with which to wage and win that conflict, but also the possibilities to harness these applications of the nuclear processes of fission and fusion for peaceful purposes. 32 years after Eddington's speculation the United States demonstrated the application of fusion in a famous nuclear weapons test. In the following years many ideas for producing ``controlled'' fusion through inertial confinement were pursued. The invention of the laser opened up new avenues which have culminated in the National Ignition Facility, NIF. I will attempt to cover the ground between Eddington, through the Manhattan Project and provide a current status of this quest at NIF. LLNL-ABS-704367-DRAFT. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Determination of fission gas yields from isotope ratios
DEFF Research Database (Denmark)
Mogensen, Mogens Bjerg
1983-01-01
This paper describes a method of calculating the actual fission yield of Kr and Xe in nuclear fuel including the effect of neutron capture reactions and decay. The bases for this calculation are the cumulative yields (ref. 1) of Kr and Xe isotopes (or pairs of isotopes) which are unaffected...... by neutron capture reactions, and measured Kr and Xe isotope ratios. Also the burnup contribution from the different fissile heavy isotopes must be known in order to get accurate fission gas yields....
Kuganathan, Navaratnarajah; Ghosh, Partha S.; Galvin, Conor O. T.; Arya, Ashok K.; Dutta, Bijon K.; Dey, Gautam K.; Grimes, Robin W.
2017-03-01
The fission gases Xe and Kr, formed during normal reactor operation, are known to degrade fuel performance, particularly at high burn-up. Using first-principles density functional theory together with a dispersion correction (DFT + D), in ThO2 we calculate the energetics of neutral and charged point defects, the di-vacancy (DV), different neutral tri-vacancies (NTV), the charged tetravacancy (CTV) defect cluster geometries and their interaction with Xe and Kr. The most favourable incorporation point defect site for Xe or Kr in defective ThO2 is the fully charged thorium vacancy. The lowest energy NTV in larger supercells of ThO2 is NTV3, however, a single Xe atom is most stable when accommodated within a NTV1. The di-vacancy (DV) is a significantly less favoured incorporation site than the NTV1 but the CTV offers about the same incorporation energy. Incorporation of a second gas atom in a NTV is a high energy process and more unfavourable than accommodation within an existing Th vacancy. The bi-NTV (BNTV) cluster geometry studied will accommodate one or two gas atoms with low incorporation energies but the addition of a third gas atom incurs a high energy penalty. The tri-NTV cluster (TNTV) forms a larger space which accommodates three gas atoms but again there is a penalty to accommodate a fourth gas atom. By considering the energy to form the defect sites, solution energies were generated showing that in ThO2-x the most favourable solution equilibrium site is the NTV1 while in ThO2 it is the DV.
Uncertainties analysis of fission fraction for reactor antineutrino experiments using DRAGON
Ma, X B; Chen, Y X; Zhong, W L; An, F P
2014-01-01
Rising interest in nuclear reactors as a source of antineutrinos for experiments motivates validated, fast, and accessible simulation to predict reactor rates. First, DRAGON was developed to calculate the fission rates of the four most important isotopes in fissions,235U,238U,239Pu and141Pu, and it was validated for PWRs using the Takahama benchmark. The fission fraction calculation function was validated through comparing our calculation results with MIT's results. we calculate the fission fraction of the Daya Bay reactor core, and compare its with those calculated by the commercial reactor simulation program SCIENCE, which is used by the Daya Bay nuclear power plant, and the results was consist with each other. The uncertainty of the antineutrino flux by the fission fraction was studied, and the uncertainty of the antineutrino flux by the fission fraction simulation is 0.6% per core for Daya Bay antineutrino experiment.
Observation of fission residues in the 16O + 181Ta system at Elab ≈ 6 MeV/A
Directory of Open Access Journals (Sweden)
Singh B. P.
2011-10-01
Full Text Available Present paper reports on the production cross-section of 24 fission like events (30 ≤ Z ≤ 60 formed via complete fusion-fission and/or incomplete fusion-fission processes in 16O+181Ta system at energies ≈ 6 MeV/A. Experiments have been performed using the recoil-catcher technique followed by off-line γ-spectroscopy. The measured cross-section of fission-like events is satisfactorily described by a statistical model code. Further, an attempt has been made to study the mass and isotopic yield distributions of fission fragments. The variance of the presently measured isotopic yield distributions has been found to be in agreement with the literature values for some other fissioning systems.
Measurement of the Fusion Probability, PCN, for Hot Fusion Reactions
Yanez, R; Barrett, J S; Yao, L; Back, B B; Zhu, S; Khoo, T L
2013-01-01
Background: The cross section for forming a heavy evaporation residue in fusion reactions depends on the capture cross section, the fusion probability, PCN, i.e., the probability that the projectile-target system will evolve inside the fission saddle point to form a completely fused system rather than re-separating (quasifission), and the survival of the completely fused system against fission. PCN is the least known of these quantities. Purpose: To measure PCN for the reaction of 101.2 MeV 18O, 147.3 MeV 26Mg, 170.9 MeV 30Si and 195.3 MeV 36S with 197Au. Methods: We measured the fission fragment angular distributions for these reactions and used the formalism of Back to deduce the fusion-fission and quasifission cross sections. From these quantities we deduced PCN for each reaction. Results: The values of PCN for the reaction of 101.2 MeV 18O, 147.3 MeV 26Mg, 170.9 MeV 30Si and 195.3 MeV 36S with 197Au are 0.66, 1.00, 0.06, 0.13, respectively. Conclusions: The new measured values of PCN agree roughly with th...
Measurement of the fusion probability, PCN, for hot fusion reactions
Yanez, R.; Loveland, W.; Barrett, J. S.; Yao, L.; Back, B. B.; Zhu, S.; Khoo, T. L.
2013-07-01
Background: The cross section for forming a heavy evaporation residue in fusion reactions depends on the capture cross section, the fusion probability, PCN, i.e., the probability that the projectile-target system will evolve inside the fission saddle point to form a completely fused system rather than reseparating (quasifission), and the survival of the completely fused system against fission. PCN is the least known of these quantities.Purpose: We want to determine PCN for the reactions of 101.2 MeV 18O, 147.3 MeV 26Mg, 170.9 MeV 30Si, and 195.3 MeV 36S with 197Au.Methods: We measured the fission fragment angular distributions for these reactions and used the formalism of Back to deduce the fusion-fission and quasifission cross sections. From these quantities we deduced PCN for each reaction.Results: The values of PCN for the reactions of 101.2 MeV 18O, 147.3 MeV 26Mg, 170.9 MeV 30Si, and 195.3 MeV 36S with 197Au are 0.66, 1.00, 0.06, and 0.13, respectively.Conclusions: The new measured values of PCN agree roughly with the semiempirical systematic dependence of PCN upon fissility for excited nuclei.
Specific fission J-window and angular momentum dependence of the fission barrier
Energy Technology Data Exchange (ETDEWEB)
Baba, Hiroshi; Saito, Tadashi; Takahashi, Naruto; Yokoyama, Akihiko [Osaka Univ., Suita (Japan); Shinohara, Atsushi
1997-04-01
A method to determine a unique J-window in the fission process was devised and the fissioning nuclide associated with thus extracted J-window was identified for each of the heavy-ion reaction systems. Obtained fission barriers at the resulting J-window were compared with the calculated values by the rotating finite range model (RFRM). The deduced barriers for individual nuclides were compared with the RFRM barriers to reproduce more or less the angular momentum dependence the RFRM prediction. The deduced systematic behavior of the fission barrier indicates no even-odd and shell corrections are necessary. The nuclear dissipation effect based on Kramer`s model revealed substantial reduction of the statistically deduced barrier heights and brought a fairly large scattering from the RFRM J-dependence. However, introduction of the temperature-dependent friction coefficient ({gamma} = 2 for T {>=} 1.0 MeV and 0.5 for T < 1.0 MeV) was found to bring about satisfactory agreement with both RFRM fission barriers and the pre-fission neutron multiplicity systematics. (author). 81 refs.
De Laeter, J. R.; Rosman, K. J. R.; Smith, C. L.
1980-10-01
Solid source mass spectrometry has been used to determine the relative cumulative fission yields of five elements in three samples of uranium ore from reactor zones in the Oklo mine site. Eighteen fission chains covering the mass range from 105 ≤ A ≤ 130 have been measured for Pd, Ag, Cd, Sn and Te. These measurements have enabled a number of nuclear parameters to be calculated including the relative proportions of 235U, 238U and 239Pu involved in the fission process. The concentration of the five elements in the Oklo samples have also been measured using the stable isotope dilution technique. These values have then been compared to the estimates of the amount of these elements produced by fission under the conditions that are appropriate to the three samples. This procedure enables the retentivity of the elements in the reactor zones to be evaluated. Our work confirms the fact that Pd and Te are retained almost in their entirety in the samples, whereas the other three elements have been partially lost from the reactor site. Almost all the Cd fission products have been lost, and more than 50% of the Ag and Sn fission-produced material has been removed.
Tonchev, Anton; Henderson, Roger; Schunck, Nicolas; Sroyer, Mark; Vogt, Ramona
2016-09-01
In 1939, Niels Bohr and John Wheeler formulated a theory of neutron-induced nuclear fission based on the hypothesis of the compound nucleus. Their theory, the so-called ``Bohr hypothesis,'' is still at the heart of every theoretical fission model today and states that the decay of a compound nucleus for a given excitation energy, spin, and parity is independent of its formation. We propose the first experiment to validate to 1-2% absolute uncertainties the practical consequences of the Bohr hypothesis during induced nuclear fission. We will compare the fission product yields (FPYs) of the same 240Pu compound nucleus produced via two different reactions (i) n+239Pu and (ii) γ+240 Pu. These high-precision FPYs measurements will be extremely beneficial for our fundamental understanding of the nuclear fission process and nuclear reactions from first principles. This work was performed under the auspices of US DOE by LLNL under Contract DE-AC52-07NA27344. Funding was provided via the LDRD-ERD-069 project.
Osborne, Andrew G
2016-01-01
Under the right conditions, self sustaining fission waves can form in fertile nuclear materials. These waves result from the transport and absorption of neutrons and the resulting production of fissile isotopes. When these fission, additional neutrons are produced and the chain reaction propagates until it is poisoned by the buildup of fission products. It is typically assumed that fission waves are soliton-like and self stabilizing. However, we show that in uranium, coupling of the neutron field to the 239U->239Np->239Pu decay chain can lead to a Hopf bifurcation. The fission reaction then ramps up and down, along with the wave velocity. The critical driver for the instability is a delay, caused by the half-life of 239U, between the time evolution of the neutron field and the production of 239Pu. This allows the 239Pu to accumulate and burn out in a self limiting oscillation that is characteristic of a Hopf bifurcation. Time dependent results are obtained using a numerical implementation of a reduced order r...
Applications of Event-by-Event Fission Modeling with FREYA
Directory of Open Access Journals (Sweden)
Vogt R.
2012-02-01
Full Text Available The recently developed code FREYA (Fission Reaction Event Yield Algorithm generates large samples of complete fission events, consisting of two receding product nuclei as well as a number of neutrons and photons, all with complete kinematic information. Thus it is possible to calculate arbitrary correlation observables whose behavior may provide unique insight into the fission process. We first discuss the present status of FREYA, which has now been extended to include spontaneous fission. Concentrating on 239Pu(nth,f, 240Pu(sf and 252Cf(sf, we discuss the neutron multiplicity correlations, the dependence of the neutron energy spectrum on the neutron multiplicity, and the relationship between the fragment kinetic energy and the number of neutrons and their energies. We also suggest novel fission observables that could be measured with modern detectors.
Modelling the widths of fission observables in GEF
Directory of Open Access Journals (Sweden)
Schmidt K.-H.
2013-03-01
Full Text Available The widths of the mass distributions of the different fission channels are traced back to the probability distributions of the corresponding quantum oscillators that are coupled to the heat bath, which is formed by the intrinsic degrees of freedom of the fissioning system under the influence of pairing correlations and shell effects. Following conclusion from stochastic calculations of Adeev and Pashkevich, an early freezing due to dynamical effects is assumed. It is shown that the mass width of the fission channels in low-energy fission is strongly influenced by the zero-point motion of the corresponding quantum oscillator. The observed variation of the mass widths of the asymmetric fission channels with excitation energy is attributed to the energy-dependent properties of the heat bath and not to the population of excited states of the corresponding quantum oscillator.
Fission and Properties of Neutron-Rich Nuclei - Proceedings of the Second International Conference
Hamilton, J. H.; Phillips, W. R.; Carter, H. K.
The Table of Contents for the book is as follows: * Preface * Structure of Elementary Matter: Cold Valleys and Their Importance in Fission, Fusion and for Superheavy Nuclei * Tunnelling Phenomena in Nuclear Physics * Heavy Nuclei Studies Using Transfer Reactions * Isomeric Properties of Nuclei Near 78Ni * Investigation of Light Actinide Nuclei at Yale and Beyond * U-Projectile Fission at Relativistic Energies * Cluster Description of Cold Fission Modes in 252Cf * Neutron-pair Transfer Theory for Pear-shaped Ba Fission Fragments * New RMFA Parameters of Normal and Exotic Nuclei * Study of Fission Fragments from 12C+238U Reactions: Prompt and Delayed Spectroscopy * γ-Ray Angular Correlations in 252Cf and 248Cm Fission Fragments * Fragment Angular Momentum and Descent Dynamics in 252Cf Spontaneous Fission * The Experimental Investigation of Neutron-Rich Nuclei * High-Spin Structure of Some Odd-Z Nuclei with A ≈ 100 From Heavy-Ion Induced Fission * Coexistence of Symmetric and Asymmetric Nuclear Shapes and 10Be Ternary Fission * Octupole Effects in the Lanthanides * High Spin Structure of the 113-1l6Cd Isotopes Produced by Heavy-Ion Induced Fission Reaction * Temperature-Dependent Fission Barriers and Mass Distributions for 239U * Strength Distributions for Gamow Teller Transitions in Very Weakly Bound Systems * High Spin Fragmentation Spectroscopy * Search for a Four-Neutron Transfer From 8He to 4He * Microsecond Isomers in Fission Fragments in the Vicinity of the Doubly Magic 132Sn * Recent On-Line NMR/on Nuclear Magnetic Dipole Moments Near 132Sn: Meson Exchange Current Effects at the Shell Closure and Shell Model Treatment of Variation with Proton and Neutron Number * High-spin K-Isomers Beyond the Fusion Limit * High Energy Neutron Induced Fission: Charge Yield Distributions and Search and Spectroscopy of New Isomers * Hartree-Fock Mean-Field Models Using Separable Interactions * Variation of Fission Characteristics Over the Nuclear Chart * Investigation of
Fission Product Library and Resource
Energy Technology Data Exchange (ETDEWEB)
Burke, J. T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Padgett, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-09-29
Fission product yields can be extracted from an irradiated sample by performing gamma ray spectroscopy on the whole sample post irradiation. There are several pitfalls to avoid when trying to determine a specific isotope's fission product yield.
Fusion Power Program biannual progress report, April-September 1979
Energy Technology Data Exchange (ETDEWEB)
1980-02-01
This biannual report summarizes the Argonne National Laboratory work performed for the Office of Fusion Energy during the April-September 1979 quarter in the following research and development areas: materials; energy storage and transfer; tritium containment, recovery and control; advanced reactor design; atomic data; reactor safety; fusion-fission hybrid systems; alternate applications of fusion energy; and other work related to fusion power. Separate abstracts were prepared for three sections. (MOW)
Fusion Power Program. Quarterly progress report, October--December 1978
Energy Technology Data Exchange (ETDEWEB)
1979-04-01
This quarterly report summarizes the Argonne National Laboratory work performed for the Office of Fusion Energy during the October--December 1978 quarter in the following research and development areas: materials; energy storage and transfer; tritium containment, recovery and control; advanced reactor design; atomic data; reactor safety; fusion-fission hybrid systems; alternate applications of fusion energy; and other work related to fusion power. Three separate abstracts were prepared for the included sections. (MOW)
Discoveries of isotopes by fission
Indian Academy of Sciences (India)
M Thoennessen
2015-09-01
Of the about 3000 isotopes presently known, about 20% have been discovered in fission. The history of fission as it relates to the discovery of isotopes as well as the various reaction mechanisms leading to isotope discoveries involving fission are presented.
Fission dynamics of hot nuclei
Indian Academy of Sciences (India)
Santanu Pal; Jhilam Sadhukhan
2014-04-01
Experimental evidence accumulated during the last two decades indicates that the fission of excited heavy nuclei involves a dissipative dynamical process. We shall briefly review the relevant dynamical model, namely the Langevin equations for fission. Statistical model predictions using the Kramers’ fission width will also be discussed.
Microscopic modeling of mass and charge distributions in the spontaneous fission of 240Pu
Sadhukhan, Jhilam; Nazarewicz, Witold; Schunck, Nicolas
2016-01-01
We propose a methodology to calculate microscopically the mass and charge distributions of spontaneous fission yields. We combine the multidimensional minimization of collective action for fission with stochastic Langevin dynamics to track the relevant fission paths from the ground-state configuration up to scission. The nuclear potential energy and collective inertia governing the tunneling motion are obtained with nuclear density functional theory in the collective space of shape deformations and pairing. We obtain a quantitative agreement with experimental data and find that both the charge and mass distributions in the spontaneous fission of 240Pu are sensitive both to the dissipation in collective motion and to adiabatic fission characteristics.
Interplay of fission modes in mass distribution of light actinide nuclei 225,227Pa
Directory of Open Access Journals (Sweden)
R. Dubey
2016-01-01
Full Text Available Fission-fragment mass distributions were measured for 225,227Pa nuclei formed in fusion reactions of 19F+206,208Pb around fusion barrier energies. Mass-angle correlations do not indicate any quasi-fission like events in this bombarding energy range. Mass distributions were fitted by Gaussian distribution and mass variance extracted. At below-barrier energies, the mass variance was found to increase with decrease in energy for both nuclei. Results from present work were compared with existing data for induced fission of 224,226Th and 228U around barrier energies. Enhancement in mass variance of 225,227Pa nuclei at below-barrier energies shows evidence for presence of asymmetric fission events mixed with symmetric fission events. This is in agreement with the results of mass distributions of nearby nuclei 224,226Th and 228U where two-mode fission process was observed. Two-mode feature of fission arises due to the shell effects changing the landscape of the potential-energy surfaces at low excitation energies. The excitation-energy dependence of the mass variance gives strong evidence for survival of microscopic shell effects in fission of light actinide nuclei 225,227Pa with initial excitation energy ∼30–50 MeV.
Fission Matrix Capability for MCNP Monte Carlo
Energy Technology Data Exchange (ETDEWEB)
Carney, Sean E. [Los Alamos National Laboratory; Brown, Forrest B. [Los Alamos National Laboratory; Kiedrowski, Brian C. [Los Alamos National Laboratory; Martin, William R. [Los Alamos National Laboratory
2012-09-05
In a Monte Carlo criticality calculation, before the tallying of quantities can begin, a converged fission source (the fundamental eigenvector of the fission kernel) is required. Tallies of interest may include powers, absorption rates, leakage rates, or the multiplication factor (the fundamental eigenvalue of the fission kernel, k{sub eff}). Just as in the power iteration method of linear algebra, if the dominance ratio (the ratio of the first and zeroth eigenvalues) is high, many iterations of neutron history simulations are required to isolate the fundamental mode of the problem. Optically large systems have large dominance ratios, and systems containing poor neutron communication between regions are also slow to converge. The fission matrix method, implemented into MCNP[1], addresses these problems. When Monte Carlo random walk from a source is executed, the fission kernel is stochastically applied to the source. Random numbers are used for: distances to collision, reaction types, scattering physics, fission reactions, etc. This method is used because the fission kernel is a complex, 7-dimensional operator that is not explicitly known. Deterministic methods use approximations/discretization in energy, space, and direction to the kernel. Consequently, they are faster. Monte Carlo directly simulates the physics, which necessitates the use of random sampling. Because of this statistical noise, common convergence acceleration methods used in deterministic methods do not work. In the fission matrix method, we are using the random walk information not only to build the next-iteration fission source, but also a spatially-averaged fission kernel. Just like in deterministic methods, this involves approximation and discretization. The approximation is the tallying of the spatially-discretized fission kernel with an incorrect fission source. We address this by making the spatial mesh fine enough that this error is negligible. As a consequence of discretization we get a
Monte Carlo Based Toy Model for Fission Process
Kurniadi, R; Viridi, S
2014-01-01
Fission yield has been calculated notoriously by two calculations approach, macroscopic approach and microscopic approach. This work will proposes another calculation approach which the nucleus is treated as a toy model. The toy model of fission yield is a preliminary method that use random number as a backbone of the calculation. Because of nucleus as a toy model hence the fission process does not represent real fission process in nature completely. Fission event is modeled by one random number. The number is assumed as width of distribution probability of nucleon position in compound nuclei when fission process is started. The toy model is formed by Gaussian distribution of random number that randomizes distance like between particle and central point. The scission process is started by smashing compound nucleus central point into two parts that are left central and right central points. These three points have different Gaussian distribution parameters such as mean ({\\mu}CN, {\\mu}L, {\\mu}R), and standard d...
Chemical state of fission products in irradiated uranium carbide fuel
Arai, Yasuo; Iwai, Takashi; Ohmichi, Toshihiko
1987-12-01
The chemical state of fission products in irradiated uranium carbide fuel has been estimated by equilibrium calculation using the SOLGASMIX-PV program. Solid state fission products are distributed to the fuel matrix, ternary compounds, carbides of fission products and intermetallic compounds among the condensed phases appearing in the irradiated uranium carbide fuel. The chemical forms are influenced by burnup as well as stoichiometry of the fuel. The results of the present study almost agree with the experimental ones reported for burnup simulated carbides.
Sensitivity analysis of the fission gas behavior model in BISON.
Energy Technology Data Exchange (ETDEWEB)
Swiler, Laura Painton; Pastore, Giovanni; Perez, Danielle; Williamson, Richard
2013-05-01
This report summarizes the result of a NEAMS project focused on sensitivity analysis of a new model for the fission gas behavior (release and swelling) in the BISON fuel performance code of Idaho National Laboratory. Using the new model in BISON, the sensitivity of the calculated fission gas release and swelling to the involved parameters and the associated uncertainties is investigated. The study results in a quantitative assessment of the role of intrinsic uncertainties in the analysis of fission gas behavior in nuclear fuel.
Dynamical features of nuclear fission
Indian Academy of Sciences (India)
Santanu Pal
2015-08-01
It is now established that the transition-state theory of nuclear fission due to Bohr and Wheeler underestimates several observables in heavy-ion-induced fusion–fission reactions. Dissipative dynamical models employing either the Langevin equation or equivalently the Fokker–Planck equation have been developed for fission of heavy nuclei at high excitations (T ∼1 MeV or higher). Here, we first present the physical picture underlying the dissipative fission dynamics. We mainly concentrate upon the Kramers’ prescription for including dissipation in fission dynamics. We discuss, in some detail, the results of a statistical model analysis of the pre-scission neutron multiplicity data from the reactions 19F+194,196,198Pt using Kramers’ fission width. We also discuss the multi-dimensional Langevin equation in the context of kinetic energy and mass distribution of the fission fragments.
Thermodynamics of fission products in UO2+-x
Energy Technology Data Exchange (ETDEWEB)
Nerikar, Pankaj V [Los Alamos National Laboratory
2009-01-01
The stabilities of selected fission products - Xe, Cs, and Sr - are investigated as a function of non-stoichiometry x in UO{sub 2{+-}x}. In particular, density functional theory (OFT) is used to calculate the incorporation and solution energies of these fission products at the anion and cation vacancy sites, at the divacancy, and at the bound Schottky defect. In order to reproduce the correct insulating state of UO{sub 2}, the DFT calculations are performed using spin polarization and with the Hubbard U tenn. In general, higher charge defects are more soluble in the fuel matrix and the solubility of fission products increases as the hyperstoichiometry increases. The solubility of fission product oxides is also explored. CS{sub 2}O is observed as a second stable phase and SrO is found to be soluble in the UO{sub 2} matrix for all stoichiometries. These observations mirror experimentally observed phenomena.
Photoluminescence dynamics in singlet fission chromophore liquid melts
Piland, Geoffrey B.; Bardeen, Christopher J.
2017-02-01
The effect of high temperature melting on the photophysics of three prototypical singlet fission molecules is investigated. Time-resolved photoluminescence is used to look at the melt phase of the molecules tetracene, diphenylhexatriene and rubrene. Chemical decomposition of tetracene precluded any detailed measurements on this molecule. In the diphenylhexatriene melt, a rapid singlet state nonradiative relaxation process outcompetes singlet fission. In the rubrene melt, singlet fission occurs at a rate similar to that of the crystal, but the decay of the delayed fluorescence is much more rapid. The rapid decay of the delayed fluorescence suggests that either the triplet lifetime is shortened, or the fusion probability decreases, or that both factors are operative at higher temperatures.
Kaur, Arshdeep; Chopra, Sahila; Gupta, Raj K.
2014-08-01
The compound nucleus (CN) fusion/formation probability PCN is defined and its detailed variations with the CN excitation energy E*, center-of-mass energy Ec .m., fissility parameter χ, CN mass number ACN, and Coulomb interaction parameter Z1Z2 are studied for the first time within the dynamical cluster-decay model (DCM). The model is a nonstatistical description of the decay of a CN to all possible processes. The (total) fusion cross section σfusion is the sum of the CN and noncompound nucleus (nCN) decay cross sections, each calculated as the dynamical fragmentation process. The CN cross section σCN is constituted of evaporation residues and fusion-fission, including intermediate-mass fragments, each calculated for all contributing decay fragments (A1, A2) in terms of their formation and barrier penetration probabilities P0 and P. The nCN cross section σnCN is determined as the quasi-fission (qf) process, where P0=1 and P is calculated for the entrance-channel nuclei. The DCM, with effects of deformations and orientations of nuclei included in it, is used to study the PCN for about a dozen "hot" fusion reactions forming a CN of mass number A ˜100 to superheavy nuclei and for various different nuclear interaction potentials. Interesting results are that PCN=1 for complete fusion, but PCNPCN≪1 due to the nCN contribution, depending strongly on different parameters of the entrance-channel reaction but found to be independent of the nuclear interaction potentials used.
Measurement of MA fission cross sections at YAYOI
Energy Technology Data Exchange (ETDEWEB)
Ohkawachi, Yasushi; Ohki, Shigeo; Wakabayashi, Toshio [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center
1998-03-01
Fission cross section ratios of minor actinide nuclides (Am-241, Am-243) relative to U-235 in the fast neutron energy region have been measured using a back-to-back (BTB) fission chamber at YAYOI fast neutron source reactor. A small BTB fission chamber was developed to measure the fission cross section ratios in the center of the core at YAYOI reactor. Dependence of the fission cross section ratios on neutron spectra was investigated by changing the position of the detector in the reactor core. The measurement results were compared with the fission cross sections in the JENDL-3.2, ENDF/B-VI and JEF-2.2 libraries. It was found that calculated values of Am-241 using the JENDL-3.2, ENDF/B-VI and JEF-2.2 data are lower by about 15% than the measured value in the center of the core (the neutron average energy is 1.44E+6(eV)). And, good agreement can be seen the measured value and calculated value of Am-243 using the JENDL-3.2 data in the center of the core (the neutron average energy is 1.44E+6)(eV), but calculated values of Am-243 using the ENDF/B-VI and JEF-2.2 data are lower by 11% and 13% than the measured value. (author)
Recoil-alpha-fission and recoil-alpha-alpha-fission events observed in the reaction Ca-48 + Am-243
Forsberg, U; Andersson, L -L; Di Nitto, A; Düllmann, Ch E; Gates, J M; Golubev, P; Gregorich, K E; Gross, C J; Herzberg, R -D; Hessberger, F P; Khuyagbaatar, J; Kratz, J V; Rykaczewski, K; Sarmiento, L G; Schädel, M; Yakushev, A; Åberg, S; Ackermann, D; Block, M; Brand, H; Carlsson, B G; Cox, D; Derkx, X; Dobaczewski, J; Eberhardt, K; Even, J; Fahlander, C; Gerl, J; Jäger, E; Kindler, B; Krier, J; Kojouharov, I; Kurz, N; Lommel, B; Mistry, A; Mokry, C; Nazarewicz, W; Nitsche, H; Omtvedt, J P; Papadakis, P; Ragnarsson, I; Runke, J; Schaffner, H; Schausten, B; Shi, Y; Thörle-Pospiech, P; Torres, T; Traut, T; Trautmann, N; Türler, A; Ward, A; Ward, D E; Wiehl, N
2015-01-01
Products of the fusion-evaporation reaction Ca-48 + Am-243 were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum f\\"ur Schwerionenforschung. Amongst the detected thirty correlated alpha-decay chains associated with the production of element Z=115, two recoil-alpha-fission and five recoil-alpha-alpha-fission events were observed. The latter are similar to four such events reported from experiments performed at the Dubna gas-filled separator. Contrary to their interpretation, we propose an alternative view, namely to assign eight of these eleven decay chains of recoil-alpha(-alpha)-fission type to start from the 3n-evaporation channel 115-288. The other three decay chains remain viable candidates for the 2n-evaporation channel 115-289.
Energy Technology Data Exchange (ETDEWEB)
Ku, L.P.; Hendel, H.W.; Liew, S.L.; Strachan, J.D.
1990-02-01
Accurate determinations of fusion neutron yields on the TFTR require that the neutron detectors be absolutely calibrated in-situ, using neutron sources of known strengths. For such calibrations, numerical simulations of neutron transport can be powerful tools in the design of experiments and the study of measurement results. On the TFTR, numerical calibration experiments' have been frequently used to complement actual detector calibrations. We present calculational approaches and transport models used in these numerical simulations, and summarize the results from simulating the calibration of {sup 235}U fission detectors carried out in December 1988. 12 refs., 9 figs., 6 tabs.
Institute of Scientific and Technical Information of China (English)
张信一; 赵柱民; 江新标; 郭和伟; 陈立新; 周永茂
2012-01-01
To calculate the fission product poisoning and bumup of the reactor accurately, the paper sets up the coupled calculation methods based on MCNP code and ORIGEN2 code and program data translation, cross section revision and date interface codes. Making use of elaborate reactor model to calculate the fission product poisoning and bumup for in-hospital neutron irradiator mark 1 reactor.%为了准确地计算反应堆的裂变产物中毒和燃耗问题,开发了一套蒙特卡罗方法程序系统.利用通用的燃耗计算方法,基于MCNP和ORIGEN2,编写了相关的数据转换、截面修正、数据接口程序,实现了MCNP和ORIGEN2程序的耦合.采用堆芯精细结构划分,对医院中子照射器Ⅰ型堆裂变产物中毒和燃耗进行了计算分析.
Directory of Open Access Journals (Sweden)
Philippe A Parone
Full Text Available Mitochondria form a highly dynamic tubular network, the morphology of which is regulated by frequent fission and fusion events. However, the role of mitochondrial fission in homeostasis of the organelle is still unknown. Here we report that preventing mitochondrial fission, by down-regulating expression of Drp1 in mammalian cells leads to a loss of mitochondrial DNA and a decrease of mitochondrial respiration coupled to an increase in the levels of cellular reactive oxygen species (ROS. At the cellular level, mitochondrial dysfunction resulting from the lack of fission leads to a drop in the levels of cellular ATP, an inhibition of cell proliferation and an increase in autophagy. In conclusion, we propose that mitochondrial fission is required for preservation of mitochondrial function and thereby for maintenance of cellular homeostasis.
General Description of Fission Observables: GEF Model Code
Energy Technology Data Exchange (ETDEWEB)
Schmidt, K.-H. [CENBG, CNRS/IN2 P3, Chemin du Solarium, B.P. 120, F-33175 Gradignan (France); Jurado, B., E-mail: jurado@cenbg.in2p3.fr [CENBG, CNRS/IN2 P3, Chemin du Solarium, B.P. 120, F-33175 Gradignan (France); Amouroux, C. [CEA, DSM-Saclay (France); Schmitt, C., E-mail: schmitt@ganil.fr [GANIL, Bd. Henri Becquerel, B.P. 55027, F-14076 Caen Cedex 05 (France)
2016-01-15
consistent with the collective enhancement of the level density. The exchange of excitation energy and nucleons between the nascent fragments on the way from saddle to scission is estimated according to statistical mechanics. As a result, excitation energy and unpaired nucleons are predominantly transferred to the heavy fragment in the superfluid regime. This description reproduces some rather peculiar observed features of the prompt-neutron multiplicities and of the even-odd effect in fission-fragment Z distributions. For completeness, some conventional descriptions are used for calculating pre-equilibrium emission, fission probabilities and statistical emission of neutrons and gamma radiation from the excited fragments. Preference is given to simple models that can also be applied to exotic nuclei compared to more sophisticated models that need precise empirical input of nuclear properties, e.g. spectroscopic information. The approach reveals a high degree of regularity and provides a considerable insight into the physics of the fission process. Fission observables can be calculated with a precision that complies with the needs for applications in nuclear technology without specific adjustments to measured data of individual systems. The GEF executable runs out of the box with no need for entering any empirical data. This unique feature is of valuable importance, because the number of systems and energies of potential significance for fundamental and applied science will never be possible to be measured. The relevance of the approach for examining the consistency of experimental results and for evaluating nuclear data is demonstrated.
Magnetic fusion 1985: what next
Energy Technology Data Exchange (ETDEWEB)
Fowler, T.K.
1985-03-01
Recent budget reductions for magnetic fusion have led to a re-examination of program schedules and objectives. Faced with delays and postponement of major facilities as previously planned, some have called for a near-term focus on science, others have stressed technology. This talk will suggest a different focus as the keynote for this conference, namely, the applications of fusion. There is no doubt that plasma science is by now mature and fusion technology is at the forefront. This has and will continue to benefit many fields of endeavor, both in actual new discoveries and techniques and in attracting and training scientists and engineers who move on to make significant contributions in science, defense and industry. Nonetheless, however superb the science or how challenging the technology, these are means, not ends. To maintain its support, the magnetic fusion program must also offer the promise of power reactors that could be competitive in the future. At this conference, several new reactor designs will be described that claim to be smaller and economically competitive with fission reactors while retaining the environmental and safety characteristics that are the hallmark of fusion. The American Nuclear Society is an appropriate forum in which to examine these new designs critically, and to stimulate better ideas and improvements. As a preview, this talk will include brief discussions of new tokamak, tandem mirror and reversed field pinch reactor designs to be presented in later sessions. Finally, as a preview of the session on fusion breeders, the talk will explore once again the economic implications of a new nuclear age, beginning with improved fission reactors fueled by fusion breeders, then ultimately evolving to reactors based solely on fusion.
Fission Product Yields from 232Th, 238U, and 235U Using 14 MeV Neutrons
Pierson, B. D.; Greenwood, L. R.; Flaska, M.; Pozzi, S. A.
2017-01-01
Neutron-induced fission yield studies using deuterium-tritium fusion-produced 14 MeV neutrons have not yet directly measured fission yields from fission products with half-lives on the order of seconds (far from the line of nuclear stability). Fundamental data of this nature are important for improving and validating the current models of the nuclear fission process. Cyclic neutron activation analysis (CNAA) was performed on three actinide targets-thorium-oxide, depleted uranium metal, and highly enriched uranium metal-at the University of Michigan's Neutron Science Laboratory (UM-NSL) using a pneumatic system and Thermo-Scientific D711 accelerator-based fusion neutron generator. This was done to measure the fission yields of short-lived fission products and to examine the differences between the delayed fission product signatures of the three actinides. The measured data were compared against previously published results for 89Kr, -90, and -92 and 138Xe, -139, and -140. The average percent deviation of the measured values from the Evaluated Nuclear Data Files VII.1 (ENDF/B-VII.1) for thorium, depleted-uranium, and highly-enriched uranium were -10.2%, 4.5%, and -12.9%, respectively. In addition to the measurements of the six known fission products, 23 new fission yield measurements from 84As to 146La are presented.
Energy Technology Data Exchange (ETDEWEB)
Casoli, P.; Authier, N. [CEA, Centre de Valduc, 21120 Is-sur-Tille (France); Laurec, J.; Bauge, E.; Granier, T. [CEA, Centre DIF, 91297 Arpajon (France)
2011-07-01
In the 1970's and early 1980's, an experimental program was performed on the facilities of the CEA Valduc Research Center to measure several actinide-fission product yields. Experiments were, in particular, completed on the Caliban and Prospero metallic core reactors to study fission-neutron-induced reactions on {sup 233}U, {sup 235}U, and {sup 239}Pu. Thick actinide samples were irradiated and the number of nuclei of each fission product was determined by gamma spectrometry. Fission chambers were irradiated simultaneously to measure the numbers of fissions in thin deposits of the same actinides. The masses of the thick samples and the thin deposits were determined by mass spectrometry and alpha spectrometry. The results of these experiments will be fully presented in this paper for the first time. A description of the Caliban and Prospero reactors, their characteristics and performances, and explanations about the experimental approach will also be given in the article. A recent work has been completed to analyze and reinterpret these measurements and particularly to evaluate the associated uncertainties. In this context, calculations have also been carried out with the Monte Carlo transport code Tripoli-4, using the published benchmarked Caliban description and a three-dimensional model of Prospero, to determine the average neutron energy causing fission. Simulation results will be discussed in this paper. Finally, new fission yield measurements will be proposed on Caliban and Prospero reactors to strengthen the results of the first experiments. (authors)
Interplay of fission modes in mass distribution of light actinide nuclei 225,227Pa
Dubey, R; Jhingan, A; Kaur, Gurpreet; Mukul, Ish; Mohanto, G; Siwal, D; Saneesh, N; Banerjee, T; Thakur, Meenu; Mahajan, Ruchi; Kumar, N; Chatterjee, M B
2015-01-01
Fission-fragment mass distributions were measured for 225,227Pa nuclei formed in fusion reactions of 19F + 206, 208Pb around fusion barrier energies. Mass-angle correlations do not indicate any quasi-fission like events in this bombarding energy range. Mass distributions were fitted by Gaussian distribution and mass variance extracted. At below-barrier energies, the mass variance was found to increase with decrease in energy for both nuclei. Results from present work were compared with existing data for induced fission of 224, 226Th and 228U around barrier energies. Enhancement in mass variance of 225, 227Pa nuclei at below-barrier energies shows evidence for presence of asymmetric fission events mixed with symmetric fission events. This is in agreement with the results of mass distributions of nearby nuclei 224, 226Th and 228U where two-mode fission process was observed. Two-mode feature of fission arises due to the shell effects changing the landscape of the potential energy surfaces at low excitation energ...
Fission decay properties of ultra neutron-rich uranium isotopes
Indian Academy of Sciences (India)
L Satpathy; S K Patra; R K Choudhury
2008-01-01
The fission decay of highly neutron-rich uranium isotopes is investigated which shows interesting new features in the barrier properties and neutron emission characteristics in the fission process. 233U and 235U are the nuclei in the actinide region in the beta stability valley which are thermally fissile and have been mainly used in reactors for power generation. The possibility of occurrence of thermally fissile members in the chain of neutron-rich uranium isotopes is examined here. The neutron number = 162 or 164 has been predicted to be magic in numerous theoretical studies carried out over the years. The series of uranium isotopes around it with = 154-172 are identified to be thermally fissile on the basis of the fission barrier and neutron separation energy systematics; a manifestation of the close shell nature of = 162 (or 164). We consider here the thermal neutron fission of a typical representative 249U nucleus in the highly neutron-rich region. Semiempirical study of fission barrier height and width shows that 250U nucleus is stable against spontaneous fission due to increase in barrier width arising out of excess neutrons. On the basis of the calculation of the probability of fragment mass yields and the microscopic study in relativistic mean field theory, this nucleus is shown to undergo exotic decay mode of thermal neutron fission (multi-fragmentation fission) whereby a number of prompt scission neutrons are expected to be simultaneously released along with the two heavy fission fragments. Such properties will have important implications in stellar evolution involving -process nucleosynthesis.
Fission yield measurements at IGISOL
Directory of Open Access Journals (Sweden)
Lantz M.
2016-01-01
Full Text Available The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f and Th(p,f have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.
Fission approach to cluster radioactivity
Indian Academy of Sciences (India)
D N Poenaru; R A Gherghescu
2015-09-01
Fission theory is used to explain decay. Also, the analytical superasymmetric fission (ASAF) model is successfully employed to make a systematic search and to predict, with other models, cluster radioactivity. The macroscopic–microscopic method is illustrated for the superheavy nucleus 286Fl. Then a few results of the theoretical approach of decay (ASAF, UNIV and semFIS models), cluster decay (ASAF and UNIV) and spontaneous fission dynamics are described with Werner–Wheeler and cranking inertia. UNIV denotes universal curve and semFIS the fission-based semiempirical formula.
Hidden systematics of fission channels
Directory of Open Access Journals (Sweden)
Schmidt Karl-Heinz
2013-12-01
Full Text Available It is a common procedure to describe the fission-fragment mass distributions of fissioning systems in the actinide region by a sum of at least 5 Gaussian curves, one for the symmetric component and a few additional ones, together with their complementary parts, for the asymmetric components. These components have been attributed to the influence of fragment shells, e.g. in the statistical scission-point model of Wilkins, Steinberg and Chasman. They have also been associated with valleys in the potential-energy landscape between the outer saddle and the scission configuration in the multi-channel fission model of Brosa. When the relative yields, the widths and the mean mass-asymmetry values of these components are fitted to experimental data, the mass distributions can be very well reproduced. Moreover, these fission channels are characterised by specific values of charge polarisation, total kinetic energy and prompt-neutron yields. The present contribution investigates the systematic variation of the characteristic fission-channel properties as a function of the composition and the excitation energy of the fissioning system. The mean position of the asymmetric fission channels in the heavy fragment is almost constant in atomic number. The deformation of the nascent fragments at scission, which is the main source of excitation energy of the separated fission fragments ending up in prompt-neutron emission, is found to be a unique function of Z for the light and the heavy fragment of the asymmetric fission channels. A variation of the initial excitation energy of the fissioning system above the fission saddle is only seen in the neutron yield of the heavy fragment. The charge polarisation in the two most important asymmetric fission channels is found to be constant and to appreciably exceed the macroscopic value. The variation of the relative yields and of the positions of the fission channels as a function of the composition and excitation energy
Complete isotopic distributions of fragments produced in transfer- and fusion-induced reactions
Directory of Open Access Journals (Sweden)
Delaune O.
2013-12-01
Full Text Available Two fission experiments have been performed at GANIL using 238U beams at different energies and light targets. Different fissioning systems were produced with centre of mass energies from 10 to 240 MeV and their decay by fission was investigated with GANIL spectrometers. Fission-fragment isotopic distributions have been obtained. The evolution with impinging energy of their properties, the neutron excess and the width of the neutron-number distributions, gives important insights into the dynamics of the fusion-fission mechanism.
V-ATPase, ScNhxlp and Yeast Vacuole Fusion
Institute of Scientific and Technical Information of China (English)
Quan-Sheng Qiu
2012-01-01
Membrane fusion is the last step in trafficking pathways during which membrane vesicles fuse with target organelles to deliver cargos.It is a central cellular reaction that plays important roles in signal transduction,protein sorting and subcellular compartmentation.Recent progress in understanding the roles of ion transporters in vacuole fusion in yeast is summanzed in this article.It is becoming increasingly evident that the vacuolar proton pump V-ATPase and vacuolar Na+/H+ antiporter ScNhxlp are key components of the vacuole fusion machinery in yeast.Yeast ScNhxlp regulates vacuole fusion by controlling the luminal pH.V-ATPases serve a dual role in vacuolar integrity in which they regulate both vacuole fusion and fission reactions in yeast.Fission defects are epistatic to fusion defects.Vacuole fission depends on the proton translocation activity of the V-ATPase; by contrast,the fusion reaction does not need the transport activity but requires the physical presence of the proton pump.Vo,the membrane-integral sector of the V-ATPase,forms trans-complexes between the opposing vacuoles in the terminal phase of vacuole fusion where the Vo trans-complexes build a continuous proteolipid channel at the fusion site to mediate the bilayer fusion.
Simultaneous Evaluation of Fission Cross Sections for Cm Isotopes
Directory of Open Access Journals (Sweden)
Lee Y.-O.
2010-03-01
Full Text Available Fission Cross Sections for a complete set of Cm-isotopes, 240-250Cm, have been calculated in the incident energy range from above resonance region to 20 MeV. This work aims at providing the fission cross sections with consistent set of model parameters for Cm isotopes, as a part of a complete evaluation including covariance files for several minor actinides which play a great role in the Advanced Fuel Cycle (AFC design and applications as well as the design of new generation of nuclear reactors (GEN-IV. This was accomplished by means of computational analyses carried out with the nuclear model code EMPIRE-2.19 which is the modular system of nuclear reaction codes. A Fission model of this work took into account transmission derived in the WKB approximation within an optical model through a double-humped fission barrier.
Simultaneous Evaluation of Fission Cross Sections for Cm Isotopes
Kim, H. I.; Gil, C.-S.; Lee, Y.-O.
2010-03-01
Fission Cross Sections for a complete set of Cm-isotopes, 240-250Cm, have been calculated in the incident energy range from above resonance region to 20 MeV. This work aims at providing the fission cross sections with consistent set of model parameters for Cm isotopes, as a part of a complete evaluation including covariance files for several minor actinides which play a great role in the Advanced Fuel Cycle (AFC) design and applications as well as the design of new generation of nuclear reactors (GEN-IV). This was accomplished by means of computational analyses carried out with the nuclear model code EMPIRE-2.19 which is the modular system of nuclear reaction codes. A Fission model of this work took into account transmission derived in the WKB approximation within an optical model through a double-humped fission barrier.
Pairing-induced speedup of nuclear spontaneous fission
Sadhukhan, Jhilam; Nazarewicz, W; Sheikh, J A; Baran, A
2014-01-01
Collective inertia is strongly influenced at the level crossing at which quantum system changes diabatically its microscopic configuration. Pairing correlations tend to make the large-amplitude nuclear collective motion more adiabatic by reducing the effect of those configuration changes. Competition between pairing and level crossing is thus expected to have a profound impact on spontaneous fission lifetimes. To elucidate the role of nucleonic pairing on spontaneous fission, we study the dynamic fission trajectories of $^{264}$Fm and $^{240}$Pu using the state-of-the-art self-consistent framework. We employ the superfluid nuclear density functional theory with the Skyrme energy density functional SkM$^*$ and a density-dependent pairing interaction. Along with shape variables, proton and neutron pairing correlations are taken as collective coordinates. The collective inertia tensor is calculated within the nonperturbative cranking approximation. The fission paths are obtained by using the least action princip...
Radiochemical problems of fusion reactors. 1. Facilities
Energy Technology Data Exchange (ETDEWEB)
Crespi, M.B.A.
1984-02-01
A list of fusion reactor candidate materials is given, for use in connection with blanket structure, breeding, moderation, neutron multiplication, cooling, magnetic field generation, electrical insulation and radiation shielding. The phenomena being studied for each group of materials are indicated. Suitable irradiation test facilities are discussed under the headings (1) accelerator-based neutron sources, (2) fission reactors, and (3) ion accelerators.
Measurement of Fission Product Yields from Fast-Neutron Fission
Arnold, C. W.; Bond, E. M.; Bredeweg, T. A.; Fowler, M. M.; Moody, W. A.; Rusev, G.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Henderson, R.; Kenneally, J.; Macri, R.; McNabb, D.; Ryan, C.; Sheets, S.; Stoyer, M. A.; Tonchev, A. P.; Bhatia, C.; Bhike, M.; Fallin, B.; Gooden, M. E.; Howell, C. R.; Kelley, J. H.; Tornow, W.
2014-09-01
One of the aims of the Stockpile Stewardship Program is a reduction of the uncertainties on fission data used for analyzing nuclear test data [1,2]. Fission products such as 147Nd are convenient for determining fission yields because of their relatively high yield per fission (about 2%) and long half-life (10.98 days). A scientific program for measuring fission product yields from 235U,238U and 239Pu targets as a function of bombarding neutron energy (0.1 to 15 MeV) is currently underway using monoenergetic neutron beams produced at the 10 MV Tandem Accelerator at TUNL. Dual-fission chambers are used to determine the rate of fission in targets during activation. Activated targets are counted in highly shielded HPGe detectors over a period of several weeks to identify decaying fission products. To date, data have been collected at neutron bombarding energies 4.6, 9.0, 14.5 and 14.8 MeV. Experimental methods and data reduction techniques are discussed, and some preliminary results are presented.
The SPIDER fission fragment spectrometer for fission product yield measurements
Energy Technology Data Exchange (ETDEWEB)
Meierbachtol, K.; Tovesson, F. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Shields, D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colorado School of Mines, Golden, CO 80401 (United States); Arnold, C. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Blakeley, R. [University of New Mexico, Albuquerque, NM 87131 (United States); Bredeweg, T.; Devlin, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hecht, A.A.; Heffern, L.E. [University of New Mexico, Albuquerque, NM 87131 (United States); Jorgenson, J.; Laptev, A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Mader, D. [University of New Mexico, Albuquerque, NM 87131 (United States); O' Donnell, J.M.; Sierk, A.; White, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2015-07-11
The SPectrometer for Ion DEtermination in fission Research (SPIDER) has been developed for measuring mass yield distributions of fission products from spontaneous and neutron-induced fission. The 2E–2v method of measuring the kinetic energy (E) and velocity (v) of both outgoing fission products has been utilized, with the goal of measuring the mass of the fission products with an average resolution of 1 atomic mass unit (amu). The SPIDER instrument, consisting of detector components for time-of-flight, trajectory, and energy measurements, has been assembled and tested using {sup 229}Th and {sup 252}Cf radioactive decay sources. For commissioning, the fully assembled system measured fission products from spontaneous fission of {sup 252}Cf. Individual measurement resolutions were met for time-of-flight (250 ps FWHM), spacial resolution (2 mm FHWM), and energy (92 keV FWHM for 8.376 MeV). Mass yield results measured from {sup 252}Cf spontaneous fission products are reported from an E–v measurement.
Soheyli, S.; Khanlari, M. Varasteh
2016-09-01
The relative yield of complete fusion and quasifission components for the 12C+204Pb , 19F+197Au , 30Si+186W , and 48Ca+168Er reactions which all lead to the compound nucleus 216Ra are analyzed to calculate the entrance channel effects by comparison of capture, complete fusion, and quasifission cross sections, emission barriers (Bfus*,Bq f ), as well as complete fusion probability estimated by statistical method within the framework of the dinuclear system model. The difference among complete fusion probabilities calculated by the dinuclear system model for different entrance channels can be explained by the hindrance to complete fusion due to the larger inner fusion barrier Bfus* for the transformation of the dinuclear system into a compound nucleus and the increase of the quasifission contribution due to the decreasing of the emission barrier Bq f of quasifission as a function of the angular momentum. Although these reactions with different entrance channels populate the same compound nucleus 216Ra at similar excitation energies, the model predicts the negligible quasifission probability for reactions having higher entrance channel mass asymmetry and the dominant decay channel is complete fission. For reactions induced by massive projectiles such as Si and Ca having lower entrance channel mass asymmetry, the quasifission component is dominant in the evolution of dinuclear system, and the fusion process is extremely hindered.
Nuclear Fission Investigation with Twin Ionization Chamber
Zeynalova, O.; Zeynalov, Sh.; Nazarenko, M.; Hambsch, F.-J.; Oberstedt, S.
2011-11-01
The purpose of the present paper was to report the recent results, obtained in development of digital pulse processing mathematics for prompt fission neutron (PFN) investigation using twin ionization chamber (TIC) along with fast neutron time-of-flight detector (ND). Due to well known ambiguities in literature (see refs. [4, 6, 9 and 11]), concerning a pulse induction on TIC electrodes by FF ionization, we first presented detailed mathematical analysis of fission fragment (FF) signal formation on TIC anode. The analysis was done using Ramo-Shockley theorem, which gives relation between charged particle motion between TIC electrodes and so called weighting potential. Weighting potential was calculated by direct numerical solution of Laplace equation (neglecting space charge) for the TIC geometry and ionization, caused by FF. Formulae for grid inefficiency (GI) correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and discussed.
Directory of Open Access Journals (Sweden)
Ripani M.
2015-01-01
Full Text Available The main features of nuclear fission as physical phenomenon will be revisited, emphasizing its peculiarities with respect to other nuclear reactions. Some basic concepts underlying the operation of nuclear reactors and the main types of reactors will be illustrated, including fast reactors, showing the most important differences among them. The nuclear cycle and radioactive-nuclear-waste production will be also discussed, along with the perspectives offered by next generation nuclear assemblies being proposed. The current situation of nuclear power in the world, its role in reducing carbon emission and the available resources will be briefly illustrated.
Beta-delayed fission probabilities of transfermium nuclei, involved in the r-process
Panov, I.; Lutostansky, Yu; Thielemann, F.-K.
2016-01-01
For the nucleosynthesis of heavy and superheavy nuclei fission becomes very important when the r-process runs in a very high neutron density environment. In part, fission is responsible for the formation of heavy nuclei due to the inclusion of fission products as new seed nuclei (fission cycling). More than that, beta-delayed fission, along with spontaneous fission, is responsible in the late stages of the r-process for the suppression of superheavy element yields. For beta-delayed fission probability calculations a model description of the beta-strength- functions is required. Extended theoretical predictions for astro-physical applications were provided long ago, and new predictions also for superheavy nuclei with uptodate nuclear input are needed. For the further extension of data to heavier transactinides the models of strength- functions should be modified, taking into account more complicated level schemes. In our present calculations the strength-function model is based on the quasi-particle approximation of Finite Fermi Systems Theory. The probabilities of beta-delayed fission and beta-delayed neutron emission are calculated for some transfermium neutron-rich nuclei, and the influence of beta-delayed fission upon superheavy element formation is discussed.
Farget, F.; Caamaño, M.; Ramos, D.; Rodrıguez-Tajes, C.; Schmidt, K.-H.; Audouin, L.; Benlliure, J.; Casarejos, E.; Clément, E.; Cortina, D.; Delaune, O.; Derkx, X.; Dijon, A.; Doré, D.; Fernández-Domınguez, B.; Gaudefroy, L.; Golabek, C.; Heinz, A.; Jurado, B.; Lemasson, A.; Paradela, C.; Roger, T.; Salsac, M. D.; Schmitt, C.
2015-12-01
Inverse kinematics is a new tool to study nuclear fission. Its main advantage is the possibility to measure with an unmatched resolution the atomic number of fission fragments, leading to new observables in the properties of fission-fragment distributions. In addition to the resolution improvement, the study of fission based on nuclear collisions in inverse kinematics beneficiates from a larger view with respect to the neutron-induced fission, as in a single experiment the number of fissioning systems and the excitation energy range are widden. With the use of spectrometers, mass and kinetic-energy distributions may now be investigated as a function of the proton and neutron number sharing. The production of fissioning nuclei in transfer reactions allows studying the isotopic yields of fission fragments as a function of the excitation energy. The higher excitation energy resulting in the fusion reaction leading to the compound nucleus 250Cf at an excitation energy of 45MeV is also presented. With the use of inverse kinematics, the charge polarisation of fragments at scission is now revealed with high precision, and it is shown that it cannot be neglected, even at higher excitation energies. In addition, the kinematical properties of the fragments inform on the deformation configuration at scission.
Energy Technology Data Exchange (ETDEWEB)
Farget, F.; Schmidt, K.H.; Clement, E.; Delaune, O.; Derkx, X.; Dijon, A.; Golabek, C.; Lemasson, A.; Roger, T.; Schmitt, C. [CEA/DSM-CNRS/IN2P3, GANIL, Caen (France); Caamano, M.; Ramos, D.; Benlliure, J.; Cortina, D.; Fernandez-Dominguez, B.; Paradela, C. [Universidade de Santiago de Compostela, Santiago de Compostela (Spain); Rodriguez-Tajes, C. [CEA/DSM-CNRS/IN2P3, GANIL, Caen (France); Universidade de Santiago de Compostela, Santiago de Compostela (Spain); Audouin, L. [Universite Paris-Sud 11, CNRS/IN2P3, Institut de Physique Nucleaire, Orsay (France); Casarejos, E. [Universidade de Vigo, Vigo (Spain); Dore, D.; Salsac, M.D. [Centre de Saclay, CEA, Irfu, Gif-sur-Yvette (France); Gaudefroy, L. [CEA DAM Ile-de-France, BP 12, Bruyeres-le-Chatel (France); Heinz, A. [Chalmers Tekniska Hoegskola, Fundamental Fysik, Goeteborg (Sweden); Jurado, B. [Universite Bordeaux, CENBG, UMR 5797 CNRS/IN2P3, Gradignan (France)
2015-12-15
Inverse kinematics is a new tool to study nuclear fission. Its main advantage is the possibility to measure with an unmatched resolution the atomic number of fission fragments, leading to new observables in the properties of fission-fragment distributions. In addition to the resolution improvement, the study of fission based on nuclear collisions in inverse kinematics beneficiates from a larger view with respect to the neutron-induced fission, as in a single experiment the number of fissioning systems and the excitation energy range are widden. With the use of spectrometers, mass and kinetic-energy distributions may now be investigated as a function of the proton and neutron number sharing. The production of fissioning nuclei in transfer reactions allows studying the isotopic yields of fission fragments as a function of the excitation energy. The higher excitation energy resulting in the fusion reaction leading to the compound nucleus {sup 250}Cf at an excitation energy of 45MeV is also presented. With the use of inverse kinematics, the charge polarisation of fragments at scission is now revealed with high precision, and it is shown that it cannot be neglected, even at higher excitation energies. In addition, the kinematical properties of the fragments inform on the deformation configuration at scission. (orig.)
Membrane biology: fission behind BARs.
Haucke, Volker
2012-06-05
Membrane bending is accomplished in part by amphipathic helix insertion into the bilayer and the assembly of BAR domain scaffolds preparing the membrane for fission. Two recent studies highlight the roles of amphipathic helices and BAR scaffolds in membrane fission and establish the structural basis of membrane bending by the N-BAR protein endophilin.
Vimar Is a Novel Regulator of Mitochondrial Fission through Miro
Ding, Lianggong; Han, Yanping; Li, Yuhong; Ji, Xunming; Liu, Lei
2016-01-01
As fundamental processes in mitochondrial dynamics, mitochondrial fusion, fission and transport are regulated by several core components, including Miro. As an atypical Rho-like small GTPase with high molecular mass, the exchange of GDP/GTP in Miro may require assistance from a guanine nucleotide exchange factor (GEF). However, the GEF for Miro has not been identified. While studying mitochondrial morphology in Drosophila, we incidentally observed that the loss of vimar, a gene encoding an atypical GEF, enhanced mitochondrial fission under normal physiological conditions. Because Vimar could co-immunoprecipitate with Miro in vitro, we speculated that Vimar might be the GEF of Miro. In support of this hypothesis, a loss-of-function (LOF) vimar mutant rescued mitochondrial enlargement induced by a gain-of-function (GOF) Miro transgene; whereas a GOF vimar transgene enhanced Miro function. In addition, vimar lost its effect under the expression of a constitutively GTP-bound or GDP-bound Miro mutant background. These results indicate a genetic dependence of vimar on Miro. Moreover, we found that mitochondrial fission played a functional role in high-calcium induced necrosis, and a LOF vimar mutant rescued the mitochondrial fission defect and cell death. This result can also be explained by vimar's function through Miro, because Miro’s effect on mitochondrial morphology is altered upon binding with calcium. In addition, a PINK1 mutant, which induced mitochondrial enlargement and had been considered as a Drosophila model of Parkinson’s disease (PD), caused fly muscle defects, and the loss of vimar could rescue these defects. Furthermore, we found that the mammalian homolog of Vimar, RAP1GDS1, played a similar role in regulating mitochondrial morphology, suggesting a functional conservation of this GEF member. The Miro/Vimar complex may be a promising drug target for diseases in which mitochondrial fission and fusion are dysfunctional. PMID:27716788
Vimar Is a Novel Regulator of Mitochondrial Fission through Miro.
Directory of Open Access Journals (Sweden)
Lianggong Ding
2016-10-01
Full Text Available As fundamental processes in mitochondrial dynamics, mitochondrial fusion, fission and transport are regulated by several core components, including Miro. As an atypical Rho-like small GTPase with high molecular mass, the exchange of GDP/GTP in Miro may require assistance from a guanine nucleotide exchange factor (GEF. However, the GEF for Miro has not been identified. While studying mitochondrial morphology in Drosophila, we incidentally observed that the loss of vimar, a gene encoding an atypical GEF, enhanced mitochondrial fission under normal physiological conditions. Because Vimar could co-immunoprecipitate with Miro in vitro, we speculated that Vimar might be the GEF of Miro. In support of this hypothesis, a loss-of-function (LOF vimar mutant rescued mitochondrial enlargement induced by a gain-of-function (GOF Miro transgene; whereas a GOF vimar transgene enhanced Miro function. In addition, vimar lost its effect under the expression of a constitutively GTP-bound or GDP-bound Miro mutant background. These results indicate a genetic dependence of vimar on Miro. Moreover, we found that mitochondrial fission played a functional role in high-calcium induced necrosis, and a LOF vimar mutant rescued the mitochondrial fission defect and cell death. This result can also be explained by vimar's function through Miro, because Miro's effect on mitochondrial morphology is altered upon binding with calcium. In addition, a PINK1 mutant, which induced mitochondrial enlargement and had been considered as a Drosophila model of Parkinson's disease (PD, caused fly muscle defects, and the loss of vimar could rescue these defects. Furthermore, we found that the mammalian homolog of Vimar, RAP1GDS1, played a similar role in regulating mitochondrial morphology, suggesting a functional conservation of this GEF member. The Miro/Vimar complex may be a promising drug target for diseases in which mitochondrial fission and fusion are dysfunctional.
FREYA-a new Monte Carlo code for improved modeling of fission chains
Energy Technology Data Exchange (ETDEWEB)
Hagmann, C A; Randrup, J; Vogt, R L
2012-06-12
A new simulation capability for modeling of individual fission events and chains and the transport of fission products in materials is presented. FREYA ( Fission Yield Event Yield Algorithm ) is a Monte Carlo code for generating fission events providing correlated kinematic information for prompt neutrons, gammas, and fragments. As a standalone code, FREYA calculates quantities such as multiplicity-energy, angular, and gamma-neutron energy sharing correlations. To study materials with multiplication, shielding effects, and detectors, we have integrated FREYA into the general purpose Monte Carlo code MCNP. This new tool will allow more accurate modeling of detector responses including correlations and the development of SNM detectors with increased sensitivity.
Dependence of Fission-Fragment Properties On Excitation Energy For Neutron-Rich Actinides
Directory of Open Access Journals (Sweden)
Ramos D.
2016-01-01
Isotopic fission yields of 250Cf, 244Cm, 240Pu, 239Np and 238U are presented in this work. With this information, the average number of neutrons as a function of the atomic number of the fragments is calculated, which reflects the impact of nuclear structure around Z=50, N=80 on the production of fission fragments. The characteristics of the Super Long, Standard I, Standard II, and Standard III fission channels were extracted from fits of the fragment yields for different ranges of excitation energy. The position and contribution of the fission channels as function of excitation energy are presented.
Role of energy cost in the yield of cold ternary fission of 252Cf
Indian Academy of Sciences (India)
P V Kunhikrishnan; K P Santhosh
2013-01-01
The energy costs in the cold ternary fission of 252Cf for various light charged particle emission are calculated by includingWong's correction for Coulomb potential. Energy cost is found to be higher in cold fission than in normal fission. It is found that energy cost always increases with decrease in experimental yield in all the light charged particle emissions. The higher ground state deformation of the fragments, the odd–even effect and the enhanced yield in the octupole region observed in cold fission are found to be consistent with the concept of energy cost.
Microscopic modeling of mass and charge distributions in the spontaneous fission of 240Pu
Sadhukhan, Jhilam; Schunck, Nicolas
2016-01-01
In this letter, we outline a methodology to calculate microscopically mass and charge distributions of spontaneous fission yields. We combine the multi-dimensional minimization of collective action for fission with stochastic Langevin dynamics to track the relevant fission paths from the ground-state configuration up to scission. The nuclear potential energy and collective inertia governing the tunneling motion are obtained with nuclear density functional theory in the collective space of shape deformations and pairing. We obtain a quantitative agreement with experimental data and find that both the charge and mass distributions in the spontaneous fission of 240Pu are sensitive both to the dissipation in collective motion and to adiabatic characteristics.
Fission modes in charged-particle induced fission
Energy Technology Data Exchange (ETDEWEB)
Matthies, A.; Kotte, R.; Seidel, W.; Stary, F.; Wohlfarth, D. (Zentralinstitut fuer Kernforschung, Rossendorf bei Dresden (German Democratic Republic))
1990-12-01
The population of the three fission modes predicted by Brosa's multi-channel fission model for the uranium region was studied in different fissioning systems. They were produced bombarding {sup 232}Th and {sup 238}U targets by light charged particles with energies slightly above the Coulomb barrier. Though the maximum excitation energy of the compound nucleus amounted to about 22 MeV, the influences of various spherical and deformed nuclear shells on the mass and total kinetic energy distributions of fission fragments are still pronounced. The larger variances of the total kinetic energy distributions compared to those of thermal neutron induced fission were explained by temperature dependent fluctuations of the amount and velocity of alteration of the scission point elongation of the fissioning system. From the ratio of these variances the portion of the potential energy dissipated among intrinsic degrees of freedom before scission was deduced for the different fission channels. It was found that the excitation remaining after pre-scission neutron emission is mainly transferred into intrinsic heat and less into pre-scission kinetic energy. (orig.).
Study of Pre-equilibrium Fission Based on Diffusion Model
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
In terms of numerical method of Smoluchowski equation the behavior of fission process in diffusion model has been described and analyzed, including the reliance upon time, as well as the deformation parameters at several nuclear temperatures in this paper. The fission rates and the residual probabilities inside the saddle point are calculated for fissile nucleus n+238 U reaction and un-fissile nucleus p+208 Pb reaction. The results indicate that there really exists a transient fission process, which means that the pre-equilibrium fission should be taken into account for the fissile nucleus at the high temperature. Oppositely, the pre-equilibrium fission could be neglected for the un-fissile nucleus. In the certain case the overshooting phenomenon of the fission rates will occur, which is mainly determined by the diffusive current at the saddle point. The higher the temperature is, the more obvious the overshooting phenomenon is. However, the emissions of the light particles accompanying the diffusion process may weaken or vanish the overshooting phenomenon.
Energy-Dependent Fission Q Values Generalized for All Actinides
Energy Technology Data Exchange (ETDEWEB)
Vogt, R
2008-09-25
We generalize Madland's parameterization of the energy release in fission to obtain the dependence of the fission Q values on incident neutron energy, E{sub n}, for all major and minor actinides. These Q(E{sub n}) parameterizations are included in the ENDL2008 release. This paper describes calculations of energy-dependent fission Q values based on parameterizations of the prompt energy release in fission [1], developed by Madland [1] to describe the prompt energy release in neutron-induced fission of {sup 235}U, {sup 238}U, and {sup 239}Pu. The energy release is then related to the energy deposited during fission so that experimentally measurable quantities can be used to obtain the Q values. A discussion of these specific parameterizations and their implementation in the processing code for Monte Carlo neutron transport, MCFGEN, [2] is described in Ref. [3]. We extend this model to describe Q(E) for all actinides, major and minor, in the Evaluated Nuclear Data Library (ENDL) 2008 release, ENDL2008.
Dynamics of the tri-nuclear system at spontaneous fission of $^{252}$Cf
Tashkhodjaev, R B; Alpomeshev, E Kh
2016-01-01
To describe of dynamics of ternary fission of $^{252}$Cf an equation of motion of the tri-nuclear system is calculated. The fission of the $^{70}$Ni+$^{50}$Ca+$^{132}$Sn channel was chosen as one of the more probable channels of true ternary fission of $^{252}$Cf. The collinearity of ternary fission has been checked by analyzing results of the equation of motion. The results show that if initially all nuclei are placed collinearly (potential energy of this position is the smallest) and the component of the middle fragment's initial velocity which is perpendicular to this line, is zero then ternary fission is collinear, otherwise the non collinear ternary fission takes place.
New fission fragment distributions and r-process origin of the rare-earth elements
Goriely, S; Lemaitre, J -F; Panebianco, S; Dubray, N; Hilaire, S; Bauswein, A; Janka, H -Thomas
2013-01-01
Neutron star (NS) merger ejecta offer a viable site for the production of heavy r-process elements with nuclear mass numbers A > 140. The crucial role of fission recycling is responsible for the robustness of this site against many astrophysical uncertainties, but calculations sensitively depend on nuclear physics. In particular the fission fragment yields determine the creation of 110 140.
Evaluation and compilation of fission product yields 1993
Energy Technology Data Exchange (ETDEWEB)
England, T.R.; Rider, B.F.
1995-12-31
This document is the latest in a series of compilations of fission yield data. Fission yield measurements reported in the open literature and calculated charge distributions have been used to produce a recommended set of yields for the fission products. The original data with reference sources, and the recommended yields axe presented in tabular form. These include many nuclides which fission by neutrons at several energies. These energies include thermal energies (T), fission spectrum energies (F), 14 meV High Energy (H or HE), and spontaneous fission (S), in six sets of ten each. Set A includes U235T, U235F, U235HE, U238F, U238HE, Pu239T, Pu239F, Pu241T, U233T, Th232F. Set B includes U233F, U233HE, U236F, Pu239H, Pu240F, Pu241F, Pu242F, Th232H, Np237F, Cf252S. Set C includes U234F, U237F, Pu240H, U234HE, U236HE, Pu238F, Am241F, Am243F, Np238F, Cm242F. Set D includes Th227T, Th229T, Pa231F, Am241T, Am241H, Am242MT, Cm245T, Cf249T, Cf251T, Es254T. Set E includes Cf250S, Cm244S, Cm248S, Es253S, Fm254S, Fm255T, Fm256S, Np237H, U232T, U238S. Set F includes Cm243T, Cm246S, Cm243F, Cm244F, Cm246F, Cm248F, Pu242H, Np237T, Pu240T, and Pu242T to complete fission product yield evaluations for 60 fissioning systems in all. This report also serves as the primary documentation for the second evaluation of yields in ENDF/B-VI released in 1993.
Spontaneous fission of superheavy nucleus $^{286}$Fl
Poenaru, Dorin N
2016-01-01
The decimal logarithm of spontaneous fission half-life of the superheavy nucleus $^{286}$Fl experimentally determined is $\\log_{10} T_f^{exp} (s) = -0.632$. We present a method to calculate the half-life based on the cranking inertia and the deformation energy, functions of two independent surface coordinates, using the best asymmetric two center shell model. In the first stage we study the statics. At a given mass asymmetry up to about $\\eta=0.5$ the potential barrier has a two hump shape, but for larger $\\eta$ it has only one hump. The touching point deformation energy versus mass asymmetry shows the three minima, produced by shell effects, corresponding to three decay modes: spontaneous fission, cluster decay and $\\alpha$~decay. The least action trajectory is determined in the plane $(R,\\eta)$ where $R$ is the separation distance of the fission fragments and $\\eta$ is the mass asymmetry. We may find a sequence of several trajectories one of which gives the least action. The parametrization with two deforma...
Potential need for fusion in the U. S. energy system
Energy Technology Data Exchange (ETDEWEB)
Beardsworth, E; Powell, J
1977-09-01
For fusion to become available for commercial use in the 21st century, R and D must be undertaken now. But it is hard to justify these expenditures with a ''cost/benefit'' oriented assessment methodology, because of both the time frame and the uncertainty of the future benefits. Focusing on the factors most relevant for current consideration of fusion's commercial prospects, i.e., consumption levels and the outcomes for fission, solar, and coal, many possible futures of the U.S. energy system are posited and analyzed under various assumptions about costs. The ''Reference Energy System'' approach was modified to establish both an appropriate degree of detail and explicit time dependence, and a computer code used to organize the relevant data and to perform calculations of system cost (annual and discounted present value), resource use, and residuals that are implied by the consumption levels and technology mix in each scenario. Not-unreasonable scenarios indicate benefits in the form of direct cost savings, which may well exceed R and D costs, which could be attributed to the implementation of fusion.
Energy Technology Data Exchange (ETDEWEB)
Pigni, Marco T [ORNL; Francis, Matthew W [ORNL; Gauld, Ian C [ORNL
2015-01-01
A recent implementation of ENDF/B-VII. independent fission product yields and nuclear decay data identified inconsistencies in the data caused by the use of updated nuclear scheme in the decay sub-library that is not reflected in legacy fission product yield data. Recent changes in the decay data sub-library, particularly the delayed neutron branching fractions, result in calculated fission product concentrations that are incompatible with the cumulative fission yields in the library, and also with experimental measurements. A comprehensive set of independent fission product yields was generated for thermal and fission spectrum neutron induced fission for ^{235,238}U and ^{239,241}Pu in order to provide a preliminary assessment of the updated fission product yield data consistency. These updated independent fission product yields were utilized in the ORIGEN code to evaluate the calculated fission product inventories with experimentally measured inventories, with particular attention given to the noble gases. An important outcome of this work is the development of fission product yield covariance data necessary for fission product uncertainty quantification. The evaluation methodology combines a sequential Bayesian method to guarantee consistency between independent and cumulative yields along with the physical constraints on the independent yields. This work was motivated to improve the performance of the ENDF/B-VII.1 library in the case of stable and long-lived cumulative yields due to the inconsistency of ENDF/B-VII.1 fission p;roduct yield and decay data sub-libraries. The revised fission product yields and the new covariance data are proposed as a revision to the fission yield data currently in ENDF/B-VII.1.
Cold fission description with constant and varying mass asymmetries
Energy Technology Data Exchange (ETDEWEB)
Duarte, S.B.; Rodriguez, O.; Tavares, O.A.P. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Goncalves, M. [Instituto de Radioprotecao e Dosimetria (IRD), Rio de Janeiro, RJ (Brazil); Garcia, F.; Guzman, F. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica
1998-01-01
Different description for varying the mass asymmetry in the fragmentation process are used to calculate the cold fission barrier penetrability. The relevance of the appropriate choice for both the description of the pre-scission phase and inertia coefficient to unify alpha decay, cluster radioactivity, and spontaneous cold fission processes in the same theoretical framework is explicitly shown. We calculate the half-life of all possible partition modes of nuclei of A > 200 following the most recent Mass Table by Audi and Wapstra. It is shown that if one uses the description in which the mass asymmetry is maintained constant during the fragmentation process, the experimental half-life-values and mass yield of {sup 234} U cold fission are satisfactorily reproduced. (author) 39 refs., 6 figs., 2 tabs.; e-mail: telo at ird.gov.br
Mandaglio, G.; Nasirov, A. K.; Curciarello, F.; De Leo, V.; Romaniuk, M.; Fazio, G.; Giardina, G.
2012-12-01
By using the dinuclear system (DNS) model we determine the capture of reactants at the first stage of reaction, the competition between the DNS decay by the quasifission (QF) and the complete fusion (CF) process up to formation of the compound nucleus (CN) having compact shape. Further evolution of the CN is considered as its fission into two fragments or formation of evaporation residues (ER) by its cooling after emission of neutrons or/and charged light particles. Disappearance of the CN fission barrier due to its fast rotation leads to the fast fission (FF) by formation of fissionlike fragments. The results of calculations for the mass symmetric 136Xe+136Xe reaction, almost mass symmetric 108Mo+144Ba reaction, and mass asymmetric like 24Mg+238U and 34S+248Cm reactions are discussed. The fusion probability PCN calculated for many massive nuclei reactions leading to formation of superheavy nuclei have been analyzed. The reactions which can lead in perspective to the synthesis of superheavy elements in the Z = 120 - 126 range and, eventually, also to heaviest nuclei, are discussed.
Directory of Open Access Journals (Sweden)
Romaniuk M.
2012-12-01
Full Text Available By using the dinuclear system (DNS model we determine the capture of reactants at the first stage of reaction, the competition between the DNS decay by the quasifission (QF and the complete fusion (CF process up to formation of the compound nucleus (CN having compact shape. Further evolution of the CN is considered as its fission into two fragments or formation of evaporation residues (ER by its cooling after emission of neutrons or/and charged light particles. Disappearance of the CN fission barrier due to its fast rotation leads to the fast fission (FF by formation of fissionlike fragments. The results of calculations for the mass symmetric 136Xe+136Xe reaction, almost mass symmetric 108Mo+144Ba reaction, and mass asymmetric like 24Mg+238U and 34S+248Cm reactions are discussed. The fusion probability PCN calculated for many massive nuclei reactions leading to formation of superheavy nuclei have been analyzed. The reactions which can lead in perspective to the synthesis of superheavy elements in the Z = 120 − 126 range and, eventually, also to heaviest nuclei, are discussed.
DEFF Research Database (Denmark)
Marie Julie Møller, Anaïs; Delaissé, Jean-Marie; Søe, Kent
2017-01-01
suggesting that fusion partners may specifically select each other and that heterogeneity between the partners seems to play a role. Therefore, we set out to directly test the hypothesis that fusion factors have a heterogenic involvement at different stages of nuclearity. Therefore, we have analyzed...... on the nuclearity of fusion partners. While CD47 promotes cell fusions involving mono-nucleated pre-osteoclasts, syncytin-1 promotes fusion of two multi-nucleated osteoclasts, but also reduces the number of fusions between mono-nucleated pre-osteoclasts. Furthermore, CD47 seems to mediate fusion mostly through......Investigations addressing the molecular keys of osteoclast fusion are primarily based on end-point analyses. No matter if investigations are performed in vivo or in vitro the impact of a given factor is predominantly analyzed by counting the number of multi-nucleated cells, the number of nuclei per...
The spectroscopy of fission fragments
Energy Technology Data Exchange (ETDEWEB)
Phillips, W.R. [Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom); Collaboration: La Direction des Sciences de la Matiere du CEA (FR); Le Fonds National de la Recherche Scientifique de Belgique (BE)
1998-12-31
High-resolution measurements on {gamma} rays from fission fragments have provided a rich source of information, unobtainable at the moment in any other way, on the spectroscopy of neutron-rich nuclei. In recent years important data have been obtained on the yrast- and near yrast-structure of neutron-rich fission fragments. We discuss the scope of measurements which can be made on prompt gamma rays from secondary fission fragments, the techniques used in the experiments and some results recently obtained. (author) 24 refs., 8 figs., 1 tab.
Cranmer, K; Mellado, B; Quayle, W; Wu Sau Lan
2002-01-01
This note considers three measures of sensitivity used to anticipate the statistical significance of an observation of the Higgs boson at the LHC with the ATLAS detector. It is demonstrated that the heuristic $s/\\sqrt{b}$ systematically overestimates the sensitivity and results in qualitatively different optimization conditions for the analysis of $H\\rightarrow W^+W^- \\rightarrow l^{+}l^{-}\\sla{p_{T}}$ for $115
DEFF Research Database (Denmark)
Bendix, Pól Martin
2015-01-01
At Stanford University, Boxer lab, I worked on membrane fusion of small unilamellar lipid vesicles to flat membranes tethered to glass surfaces. This geometry closely resembles biological systems in which liposomes fuse to plasma membranes. The fusion mechanism was studied using DNA zippering...... between complementary strands linked to the two apposing membranes closely mimicking the zippering mechanism of SNARE fusion complexes....
Prompt γ-ray production in neutron-induced fission of 239Pu
Ullmann, J. L.; Bond, E. M.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Kawano, T.; Lee, H. Y.; O'Donnell, J. M.; Hayes, A. C.; Stetcu, I.; Taddeucci, T. N.; Talou, P.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Chyzh, A.; Gostic, J.; Henderson, R.; Kwan, E.; Wu, C. Y.
2013-04-01
Background: The prompt gamma-ray spectrum from fission is important for understanding the physics of nuclear fission, and also in applications involving fission. Relatively few measurements of the prompt gamma spectrum from 239Pu(n,f) have been published.Purpose: This experiment measured the multiplicity, individual gamma energy spectrum, and total gamma energy spectrum of prompt fission gamma rays from 239Pu(n,f) in the neutron energy range from thermal to 30 keV, to test models of fission and to provide information for applications.Method: Gamma rays from neutron-induced fission of 239Pu were measured using the DANCE gamma-ray calorimeter. Fission events were tagged by detecting fission products in a parallel-plate avalanche counter in the center of DANCE. The measurements were corrected for detector response using a geant4 model of DANCE. A detailed analysis for the gamma rays from the 1+ resonance complex at 10.93 eV is presented.Results: A six-parameter analytical parametrization of the fission gamma-ray spectrum was obtained. A Monte Carlo Hauser-Feshbach calculation provided good general agreement with the data, but some differences remain to be resolved.Conclusions: An analytic parametrization can be made of the gamma-ray multiplicity, energy distribution, and total-energy distribution for the prompt gamma rays following neutron-induced fission of 239Pu. This parametrization may be useful for applications. Modern Monte Carlo Hauser-Feshbach calculations can do a good job of calculating the fission gamma-ray emission spectrum, although some details remain to be understood.
First inverse-kinematics fission measurements in a gaseous active target
Rodríguez-Tajes, C.; Farget, F.; Acosta, L.; Alvarez-Pol, H.; Babo, M.; Boulay, F.; Caamaño, M.; Damoy, S.; Fernández-Domínguez, B.; Galaviz, D.; Grinyer, G. F.; Grinyer, J.; Harakeh, M. N.; Konczykowski, P.; Martel, I.; Pancin, J.; Randisi, G.; Renzi, F.; Roger, T.; Sánchez-Benítez, A. M.; Teubig, P.; Vandebrouck, M.
2017-02-01
The fission of a variety of actinides was induced by fusion and transfer reactions between a 238U beam and 12C nuclei, in the active target MAYA. The performance of MAYA was studied, as well as its capability to reconstruct the fission-fragment trajectories. Furthermore, a full characterization of the different transfer reactions was achieved, and the populated excitation-energy distributions were investigated as a function of the kinetic energy in the entrance channel. The ratio between transfer- and fusion-induced fission cross-sections was also determined, in order to investigate the competition between both reaction types and its evolution with the incident energy. The experimental results will be discussed with a view to forthcoming radioactive-ion beam facilities, and next-generation active-target setups.
Power Installations based on Activated Nuclear Reactions of Fission and Synthesis
Grigoriev, Yuriy
2016-01-01
The general scheme of power installations based on nuclear reactions of fission and synthesis activated by external sources is analyzed. The external activation makes possible to support nuclear reactions at temperatures and pressures lower than needed for chain reactions, so simplifies considerably practical realization of power installations. The possibility of operation on subcritical masses allows making installations compact and safe at emergency situations. Installations are suitable for transmutation of radioactive nuclides, what solves the problem of utilization of nuclear waste products. It is proposed and considered schemes of power installations based on nuclear reactions of fission and fusion, activated by external sources, different from ADS systems. Variants of activation of nuclear reactions of fission (U-235, 238, Pu-239) and fusion (Li-6,7, B-10,11) are considered.
Modeling of Fission Gas Release in UO2
Energy Technology Data Exchange (ETDEWEB)
MH Krohn
2006-01-23
A two-stage gas release model was examined to determine if it could provide a physically realistic and accurate model for fission gas release under Prometheus conditions. The single-stage Booth model [1], which is often used to calculate fission gas release, is considered to be oversimplified and not representative of the mechanisms that occur during fission gas release. Two-stage gas release models require saturation at the grain boundaries before gas is release, leading to a time delay in release of gases generated in the fuel. Two versions of a two-stage model developed by Forsberg and Massih [2] were implemented using Mathcad [3]. The original Forsbers and Massih model [2] and a modified version of the Forsberg and Massih model that is used in a commercially available fuel performance code (FRAPCON-3) [4] were examined. After an examination of these models, it is apparent that without further development and validation neither of these models should be used to calculate fission gas release under Prometheus-type conditions. There is too much uncertainty in the input parameters used in the models. In addition. the data used to tune the modified Forsberg and Massih model (FRAPCON-3) was collected under commercial reactor conditions, which will have higher fission rates relative to Prometheus conditions [4].
Fabrication and Installation of Radiation Shielded Spent Fuel Fusion System
Energy Technology Data Exchange (ETDEWEB)
Park, Soon Dal; Park, Yang Soon; Kim, Jong Goo; Ha, Yeong Keong; Song, Kyu Seok
2010-02-15
Most of the generated fission gases are retained in the fuel matrix in supersaturated state, thus alter the original physicochemical properties of the fuel. And some of them are released into free volume of a fuel rod and that cause internal pressure increase of a fuel rod. Furthermore, as extending fuel burnup, the data on fission gas generation(FGG) and fission gas release(FGR) are considered very important for fuel safety investigation. Consequently, it is required to establish an experimental facility for handling of highly radioactive sample and to develop an analytical technology for measurement of retained fission gas in a spent fuel. This report describes not only on the construction of a shielded glove box which can handle highly radioactive materials but also on the modifications and instrumentations of spent fuel fusion facilities and collection apparatuses of retained fission gas
Toyama, Erin Quan; Herzig, Sébastien; Courchet, Julien; Lewis, Tommy L; Losón, Oliver C; Hellberg, Kristina; Young, Nathan P; Chen, Hsiuchen; Polleux, Franck; Chan, David C; Shaw, Reuben J
2016-01-15
Mitochondria undergo fragmentation in response to electron transport chain (ETC) poisons and mitochondrial DNA-linked disease mutations, yet how these stimuli mechanistically connect to the mitochondrial fission and fusion machinery is poorly understood. We found that the energy-sensing adenosine monophosphate (AMP)-activated protein kinase (AMPK) is genetically required for cells to undergo rapid mitochondrial fragmentation after treatment with ETC inhibitors. Moreover, direct pharmacological activation of AMPK was sufficient to rapidly promote mitochondrial fragmentation even in the absence of mitochondrial stress. A screen for substrates of AMPK identified mitochondrial fission factor (MFF), a mitochondrial outer-membrane receptor for DRP1, the cytoplasmic guanosine triphosphatase that catalyzes mitochondrial fission. Nonphosphorylatable and phosphomimetic alleles of the AMPK sites in MFF revealed that it is a key effector of AMPK-mediated mitochondrial fission.
Energy Technology Data Exchange (ETDEWEB)
Cevolani, S.; Nava, E.; Burn, K.W. [ENEA, Divisione Sistemi Energetici Ecosostenibili, Centro Ricerche Ezio Clementel, Bologna (Italy)
2001-07-01
In the framework of an ADS study (Accelerator Driven System, a reactor cooled by a lead bismuth alloy) the distribution of the deposited energy between the fuel, coolant and structural materials was evaluated by means of Monte Carlo calculations. The energy deposition in the coolant turned out to be about four percent of the total deposited energy. In order to study this effect, further calculations were performed on water and sodium cooled reactors. Such an analysis showed, for both coolant materials, a much lower heat deposition, about one percent. Based on such results, a thermohydraulic analysis was performed in order to verify the effect of this phenomenon on the fuel assembly temperature distribution. The main effect of a significant fraction of energy deposition in the coolant is concerned with the decrease of the fuel pellet temperature. As a consequence, taking into account this effect allows to increase the possibilities of optimization at the disposal of the designer. [Italian] Nell'ambito dello studio di un ADS (Accelerator Driven System, un reattore refrigerato per mezzo di una lega di piombo-bismuto) per mezzo di calcoli Monte Carlo sono stati valutati i contributi di deposizione di potenza nei materiali fissile, strutturale e refrigerante, ottenendo che il contributo della potenza depositata nel refrigerante e' pari al quattro per cento circa del totale. Allo scopo di meglio approfondire questo effetto, sono stati effettuati ulteriori calcoli in relazione a reattori refrigeranti ad acqua e sodio; i risultati mostrano come, in questi casi, la deposizione di potenza nel refrigerante sia decisamente inferiore dell'ordine di un per cento circa. Sulla base di tali risultati, e' stata avviata un'analisi di caratterre termoidraulico avente lo scopo di verificare l'effetto di questo fenomeno sulla distribuzione di temperatura negli elementi di combustibile. L'effetto principale di una sensibile frazione di energia
Models of lipid droplets growth and fission in adipocyte cells
Energy Technology Data Exchange (ETDEWEB)
Boschi, Federico, E-mail: federico.boschi@univr.it [Department of Computer Science, University of Verona, Strada Le Grazie 15, 37134 Verona (Italy); Rizzatti, Vanni; Zamboni, Mauro [Department of Medicine, Geriatric Section, University of Verona, Piazzale Stefani 1, 37126 Verona (Italy); Sbarbati, Andrea [Department of Neurological and Movement Sciences, University of Verona, Strada Le Grazie 8, 37134 Verona (Italy)
2015-08-15
Lipid droplets (LD) are spherical cellular inclusion devoted to lipids storage. It is well known that excessive accumulation of lipids leads to several human worldwide diseases like obesity, type 2 diabetes, hepatic steatosis and atherosclerosis. LDs' size range from fraction to one hundred of micrometers in adipocytes and is related to the lipid content, but their growth is still a puzzling question. It has been suggested that LDs can grow in size due to the fusion process by which a larger LD is obtained by the merging of two smaller LDs, but these events seems to be rare and difficult to be observed. Many other processes are thought to be involved in the number and growth of LDs, like the de novo formation and the growth through additional neutral lipid deposition in pre-existing droplets. Moreover the number and size of LDs are influenced by the catabolism and the absorption or interaction with other organelles. The comprehension of these processes could help in the confinement of the pathologies related to lipid accumulation. In this study the LDs' size distribution, number and the total volume of immature (n=12), mature (n=12, 10-days differentiated) and lipolytic (n=12) 3T3-L1 adipocytes were considered. More than 11,000 LDs were measured in the 36 cells after Oil Red O staining. In a previous work Monte Carlo simulations were used to mimic the fusion process alone between LDs. We found that, considering the fusion as the only process acting on the LDs, the size distribution in mature adipocytes can be obtained with numerical simulation starting from the size distribution in immature cells provided a very high rate of fusion events. In this paper Monte Carlo simulations were developed to mimic the interaction between LDs taking into account many other processes in addition to fusion (de novo formation and the growth through additional neutral lipid deposition in pre-existing droplets) in order to reproduce the LDs growth and we also simulated the
Udagawa, Osamu; Ishihara, Takaya; Maeda, Maki; Matsunaga, Yui; Tsukamoto, Satoshi; Kawano, Natsuko; Miyado, Kenji; Shitara, Hiroshi; Yokota, Sadaki; Nomura, Masatoshi; Mihara, Katsuyoshi; Mizushima, Noboru; Ishihara, Naotada
2014-10-20
Mitochondria are dynamic organelles that change their morphology by active fusion and fission in response to cellular signaling and differentiation. The in vivo role of mitochondrial fission in mammals has been examined by using tissue-specific knockout (KO) mice of the mitochondria fission-regulating GTPase Drp1, as well as analyzing a human patient harboring a point mutation in Drp1, showing that Drp1 is essential for embryonic and neonatal development and neuronal function. During oocyte maturation and aging, structures of various membrane organelles including mitochondria and the endoplasmic reticulum (ER) are changed dynamically, and their organelle aggregation is related to germ cell formation and epigenetic regulation. However, the underlying molecular mechanisms of organelle dynamics during the development and aging of oocytes have not been well understood. Here, we analyzed oocyte-specific mitochondrial fission factor Drp1-deficient mice and found that mitochondrial fission is essential for follicular maturation and ovulation in an age-dependent manner. Mitochondria were highly aggregated with other organelles, such as the ER and secretory vesicles, in KO oocyte, which resulted in impaired Ca(2+) signaling, intercellular communication via secretion, and meiotic resumption. We further found that oocytes from aged mice displayed reduced Drp1-dependent mitochondrial fission and defective organelle morphogenesis, similar to Drp1 KO oocytes. On the basis of these findings, it appears that mitochondrial fission maintains the competency of oocytes via multiorganelle rearrangement.
Fission hindrance and nuclear viscosity
Indian Academy of Sciences (India)
Indranil Mazumdar
2015-08-01
We discuss the role of nuclear viscosity in hindering the fission of heavy nuclei as observed in the experimental measurements of GDR -ray spectra from the fissioning nuclei. We review a set of experiments carried out and reported by us previously [see Dioszegi et al, Phys. Rev. C 61, 024613 (2000); Shaw et al, Phys. Rev. C 61, 044612 (2000)] and argue that the nuclear viscosity parameter has no apparent dependence on temperature. However, it may depend upon the deformation of the nucleus.
Fusion rings and fusion ideals
DEFF Research Database (Denmark)
Andersen, Troels Bak
by the so-called fusion ideals. The fusion rings of Wess-Zumino-Witten models have been widely studied and are well understood in terms of precise combinatorial descriptions and explicit generating sets of the fusion ideals. They also appear in another, more general, setting via tilting modules for quantum...
Prompt Fission Neutron Spectra of Actinides
Energy Technology Data Exchange (ETDEWEB)
Capote, R; Chen, Y J; Hambsch, F J; Kornilov, N V; Lestone, J P; Litaize, O; Morillon, B; Neudecker, D; Oberstedt, S; Ohsawa, T; Smith, D. L.
2016-01-01
The energy spectrum of prompt neutrons emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) “Evaluation of Prompt Fission Neutron Spectra of Actinides”was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei. The following technical areas were addressed: (i) experiments and uncertainty quantification (UQ): New data for neutron-induced fission of 233U, 235U, 238U, and 239Pu have been measured, and older data have been compiled and reassessed. There is evidence from the experimental work of this CRP that a very small percentage of neutrons emitted in fission are actually scission neutrons; (ii) modeling: The Los Alamos model (LAM) continues to be the workhorse for PFNS evaluations. Monte Carlo models have been developed that describe the fission phenomena microscopically, but further development is needed to produce PFNS evaluations meeting the uncertainty targets; (iii) evaluation methodologies: PFNS evaluations rely on the use of the least-squares techniques for merging experimental and model data. Considerable insight was achieved on how to deal with the problem of too small uncertainties in PFNS evaluations. The importance of considering that all experimental PFNS data are “shape” data was stressed; (iv) PFNS evaluations: New evaluations, including covariance data, were generated for major actinides including 1) non-model GMA evaluations of the 235U(nth,f), 239Pu(nth,f), and 233U(nth,f) PFNS based exclusively on experimental data (0.02 ≤ E ≤ 10 MeV), which resulted in PFNS average energies E of 2.00±0.01, 2.073±0.010, and 2.030±0.013 MeV, respectively; 2) LAM evaluations of neutron-induced fission spectra on uranium and plutonium targets with improved UQ for incident energies from thermal up to 30 MeV; and 3) Point-by-Point calculations for 232Th, 234U and 237Np targets; and (v) data
Neutron induced current pulses in fission chambers. [LMFBR
Energy Technology Data Exchange (ETDEWEB)
Taboas, A L; Buck, W L
1978-01-01
The mechanism of neutron induced current pulse generation in fission chambers is discussed. By application of the calculated detector transfer function to proposed detector current pulse shapes, and by comparison with actually observed detector output voltage pulses, a credible, semi-empirical, trapezoidal pulse shape of chamber current is obtained.
Energy Technology Data Exchange (ETDEWEB)
Zaja, Ivan [Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226 (United States); Bai, Xiaowen, E-mail: xibai@mcw.edu [Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226 (United States); Liu, Yanan; Kikuchi, Chika; Dosenovic, Svjetlana; Yan, Yasheng; Canfield, Scott G. [Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226 (United States); Bosnjak, Zeljko J. [Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226 (United States); Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226 (United States)
2014-10-31
Highlights: • Drp1-mediated increased mitochondrial fission but not fusion is involved the cardiomyocyte death during anoxia-reoxygenation injury. • Reactive oxygen species are upstream initiators of mitochondrial fission. • Increased mitochondrial fission is resulted from Cdk1-, PKCδ-, and calcineurin-mediated Drp1 pathways. - Abstract: Myocardial ischemia–reperfusion (I/R) injury is one of the leading causes of death and disability worldwide. Mitochondrial fission has been shown to be involved in cardiomyocyte death. However, molecular machinery involved in mitochondrial fission during I/R injury has not yet been completely understood. In this study we aimed to investigate molecular mechanisms of controlling activation of dynamin-related protein 1 (Drp1, a key protein in mitochondrial fission) during anoxia-reoxygenation (A/R) injury of HL1 cardiomyocytes. A/R injury induced cardiomyocyte death accompanied by the increases of mitochondrial fission, reactive oxygen species (ROS) production and activated Drp1 (pSer616 Drp1), and decrease of inactivated Drp1 (pSer637 Drp1) while mitochondrial fusion protein levels were not significantly changed. Blocking Drp1 activity with mitochondrial division inhibitor mdivi1 attenuated cell death, mitochondrial fission, and Drp1 activation after A/R. Trolox, a ROS scavenger, decreased pSer616 Drp1 level and mitochondrial fission after A/R. Immunoprecipitation assay further indicates that cyclin dependent kinase 1 (Cdk1) and protein kinase C isoform delta (PKCδ) bind Drp1, thus increasing mitochondrial fission. Inhibiting Cdk1 and PKCδ attenuated the increases in pSer616 Drp1, mitochondrial fission, and cardiomyocyte death. FK506, a calcineurin inhibitor, blocked the decrease in expression of inactivated pSer637 Drp1 and mitochondrial fission. Our findings reveal the following novel molecular mechanisms controlling mitochondrial fission during A/R injury of cardiomyocytes: (1) ROS are upstream initiators of
Systematics of fission cross sections at the intermediate energy region
Energy Technology Data Exchange (ETDEWEB)
Fukahori, Tokio; Chiba, Satoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1997-03-01
The systematics was obtained with fitting experimental data for proton induced fission cross sections of Ag, {sup 181}Ta, {sup 197}Au, {sup 206,207,208}Pb, {sup 209}Bi, {sup 232}Th, {sup 233,235,238}U, {sup 237}Np and {sup 239}Pu above 20 MeV. The low energy cross section of actinoid nuclei is omitted from systematics study, since the cross section has a complicated shape and strongly depends on characteristic of nucleus. The fission cross sections calculated by the systematics are in good agreement with experimental data. (author)
A new prompt heavy-ion-induced fission mode
Indian Academy of Sciences (India)
W Udo Schröder
2015-08-01
Fission instabilities induced by mechanical and thermal stresses on intermediate nuclear systems in heavy-ion reactions are poorly understood but should reveal independent evidence for the nuclear equation of state (EoS), notably the tensile strength of finite nuclei. Experimental evidence is presented in support of a new mode of prompt fission of the composite nucleus formed in central 78Kr+40Ca collisions at only a few MeV per nucleon above the interaction barrier. The new process recalls the ‘L-window for fusion’ phenomenon, which was predicted by the early reaction theory and reappears in modern DFT model calculations.
Neutron and fission yields from high-energy deuterons in infinite /sup 238/U targets
Energy Technology Data Exchange (ETDEWEB)
Canfield, E.
1965-06-28
Early work on the interaction of high energy deuterons with large /sup 238/U targets is reexamined and current theoretical study is discussed. Results of fission and neutron yield calculations are compared with experiment. (SDF)
Fission characteristics of 216Ra formed in heavy-ion induced reactions
Indian Academy of Sciences (India)
Hadi Eslamizadeh
2013-11-01
A Kramers-modified statistical model is used to calculate the cross-section of the evaporation residue, fission cross-section, average pre-fission multiplicities of protons and -particles for 216Ra formed in 19F + 197Au reactions and results are compared with the experimental data. To calculate these quantities, the effects of temperature and spin K about the symmetry axis have been considered in the calculations of the potential energy surfaces and the fission widths. It is shown that the results of the calculations using values of the temperature coefficient of the effective potential = 0.008 ± 0.003 MeV−2 and scaling factor of the fission-barrier height $r_{s} = 1.004 ± 0.002$ are in good agreement with the experimental data.
Measurement and Analysis of Fission Rates in a Spherical Mockup of Uranium and Polyethylene
Tong-Hua, Zhu; Xin-Xin, Lu; Rong, Liu; Zi-Jie, Han; Li, Jiang; Mei, Wang
2013-01-01
Measurements of the reaction rate distribution were carried out using two kinds of Plate Micro Fission Chamber(PMFC). The first is a depleted uranium chamber and the second an enriched uranium chamber. The material in the depleted uranium chamber is strictly the same as the material in the uranium assembly. With the equation solution to conduct the isotope contribution correction, the fission rate of 238U and 235U were obtained from the fission rate of depleted uranium and enriched uranium. And then, the fission count of 238U and 235U in an individual uranium shell was obtained. In this work, MCNP5 and continuous energy cross sections ENDF/BV.0 were used for the analysis of fission rate distribution and fission count. The calculated results were compared with the experimental ones. The calculation of fission rate of DU and EU were found to agree with the measured ones within 10% except at the positions in polyethylene region and the two positions near the outer surface. Beacause the fission chamber was not co...
Fission-track analysis of meteorites: Dating of the Marjalahti pallasite
Energy Technology Data Exchange (ETDEWEB)
Bondar, Yu.V. [Institute of Environmental Geochemistry, 34a Palladin ave., Kiev 03142 (Ukraine)]. E-mail: juliavad@yahoo.com; Perelygin, V.P. [Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation)
2005-11-15
The results of the Marjalahti pallasite fission-track age determination are presented. Thorough examination of fossil tracks in the phosphate (whitlockite) crystals coupled with U-content determination in whitlockites can make it possible to estimate the contributions of all possible track sources to the total track density and to calculate a model fission-track age. It is found that whitlockite crystals of the Marjalahti pallasite contain fossil tracks due to galactic cosmic rays (VH, VVH nuclei); fission of U and Th induced by cosmic rays; spontaneous fission of {sup 238}U; and spontaneous fission of extinct, short-lived {sup 244}Pu present in significant quantities in the early solar system. A great track density attributed to the extinct {sup 244}Pu testifies to the high fission-track age. The model fission-track ages of (4.31+/-0.02)x10{sup 9}yr for the Marjalahti pallasite are calculated. Petrographic studies allow us to interpret the fission-track age as the time of the last shock/thermal event in the cosmic history of the pallasite.
Comparison of Fission Product Yields and Their Impact
Energy Technology Data Exchange (ETDEWEB)
S. Harrison
2006-02-01
This memorandum describes the Naval Reactors Prime Contractor Team (NRPCT) Space Nuclear Power Program (SNPP) interest in determining the expected fission product yields from a Prometheus-type reactor and assessing the impact of these species on materials found in the fuel element and balance of plant. Theoretical yield calculations using ORIGEN-S and RACER computer models are included in graphical and tabular form in Attachment, with focus on the desired fast neutron spectrum data. The known fission product interaction concerns are the corrosive attack of iron- and nickel-based alloys by volatile fission products, such as cesium, tellurium, and iodine, and the radiological transmutation of krypton-85 in the coolant to rubidium-85, a potentially corrosive agent to the coolant system metal piping.
A new approach to barrier-top fission dynamics
Bertsch, G. F.; Mehlhaff, J. M.
2016-06-01
We proposed a calculational framework for describing induced fission that avoids the Bohr-Wheeler assumption of well-defined fission channels. The building blocks of our approach are configurations that form a discrete, orthogonal basis and can be characterized by both energy and shape. The dynamics is to be determined by interaction matrix elements between the states rather than by a Hill-Wheeler construction of a collective coordinate. Within our approach, several simple limits can be seen: diffusion; quantized conductance; and ordinary decay through channels. The specific proposal for the discrete basis is to use the Kπ quantum numbers of the axially symmetric Hartree-Fock approximation to generate the configurations. Fission paths would be determined by hopping from configuration to configuration via the residual interaction. We show as an example the configurations needed to describe a fictitious fission decay 32S → 16 O + 16 O. We also examine the geometry of the path for fission of 236U, measuring distances by the number of jumps needed to go to a new Kπ partition.
Collective aspects of singlet fission in molecular crystals
Energy Technology Data Exchange (ETDEWEB)
Teichen, Paul E.; Eaves, Joel D., E-mail: joel.eaves@colorado.edu [Department of Chemistry and Biochemistry, The University of Colorado at Boulder, Boulder, Colorado 80309 (United States)
2015-07-28
We present a model to describe collective features of singlet fission in molecular crystals and analyze it using many-body theory. The model we develop allows excitonic states to delocalize over several chromophores which is consistent with the character of the excited states in many molecular crystals, such as the acenes, where singlet fission occurs. As singlet states become more delocalized and triplet states more localized, the rate of singlet fission increases. We also determine the conditions under which the two triplets resulting from fission are correlated. Using the Bethe Ansatz and an entanglement measure for indistinguishable bipartite systems, we calculate the triplet-triplet entanglement as a function of the biexciton interaction strength. The biexciton interaction can produce bound biexciton states and provides a source of entanglement between the two triplets even when the triplets are spatially well separated. Significant entanglement between the triplet pair occurs well below the threshold for bound pair formation. Our results paint a dynamical picture that helps to explain why fission has been observed to be more efficient in molecular crystals than in their covalent dimer analogues and have consequences for photovoltaic efficiency models that assume that the two triplets can be extracted independently.
Correcting mitochondrial fusion by manipulating mitofusin conformations
Franco, Antonietta; Kitsis, Richard N.; Fleischer, Julie A.; Gavathiotis, Evripidis; Kornfeld, Opher S.; Gong, Guohua; Biris, Nikolaos; Benz, Ann; Qvit, Nir; Donnelly, Sara K; Chen, Yun; Mennerick, Steven; Hodgson, Louis; Mochly-Rosen, Daria; Dorn, Gerald W
2017-01-01
Summary Mitochondria are dynamic organelles, remodeling and exchanging contents during cyclic fusion and fission. Genetic mutations of mitofusin (Mfn) 2 interrupt mitochondrial fusion and cause the untreatable neurodegenerative condition, Charcot Marie Tooth disease type 2A (CMT2A). It has not been possible to directly modulate mitochondrial fusion, in part because the structural basis of mitofusin function is incompletely understood. Here we show that mitofusins adopt either a fusion-constrained or fusion-permissive molecular conformation directed by specific intramolecular binding interactions, and demonstrate that mitofusin-dependent mitochondrial fusion can be regulated by targeting these conformational transitions. Based on this model we engineered a cell-permeant minipeptide to destabilize fusion-constrained mitofusin and promote the fusion-permissive conformation, reversing mitochondrial abnormalities in cultured fibroblasts and neurons harboring CMT2A gene defects. The relationship between mitofusin conformational plasticity and mitochondrial dynamism uncovers a central mechanism regulating mitochondrial fusion whose manipulation can correct mitochondrial pathology triggered by defective or imbalanced mitochondrial dynamics. PMID:27775718
Chamber Design for the Laser Inertial Fusion Energy (LIFE) Engine
Energy Technology Data Exchange (ETDEWEB)
Latkowski, J F; Abbott, R P; Aceves, S; Anklam, T; Badders, D; Cook, A W; DeMuth, J; Divol, L; El-Dasher, B; Farmer, J C; Flowers, D; Fratoni, M; ONeil, R G; Heltemes, T; Kane, J; Kramer, K J; Kramer, R; Lafuente, A; Loosmore, G A; Morris, K R; Moses, G A; Olson, B; Pantano, C; Reyes, S; Rhodes, M; Roe, K; Sawicki, R; Scott, H; Spaeth, M; Tabak, M; Wilks, S
2010-11-30
The Laser Inertial Fusion Energy (LIFE) concept is being designed to operate as either a pure fusion or hybrid fusion-fission system. The present work focuses on the pure fusion option. A key component of a LIFE engine is the fusion chamber subsystem. It must absorb the fusion energy, produce fusion fuel to replace that burned in previous targets, and enable both target and laser beam transport to the ignition point. The chamber system also must mitigate target emissions, including ions, x-rays and neutrons and reset itself to enable operation at 10-15 Hz. Finally, the chamber must offer a high level of availability, which implies both a reasonable lifetime and the ability to rapidly replace damaged components. An integrated design that meets all of these requirements is described herein.
Nuclear fission and neutron-induced fission cross-sections
James, G D; Michaudon, A; Michaudon, A; Cierjacks, S W; Chrien, R E
2013-01-01
Nuclear Fission and Neutron-Induced Fission Cross-Sections is the first volume in a series on Neutron Physics and Nuclear Data in Science and Technology. This volume serves the purpose of providing a thorough description of the many facets of neutron physics in different fields of nuclear applications. This book also attempts to bridge the communication gap between experts involved in the experimental and theoretical studies of nuclear properties and those involved in the technological applications of nuclear data. This publication will be invaluable to those interested in studying nuclear fis
Experimental approach to fission process of actinides
Energy Technology Data Exchange (ETDEWEB)
Baba, Hiroshi [Osaka Univ., Toyonaka (Japan). Faculty of Science
1997-07-01
From experimental views, it seems likely that the mechanism of nuclear fission process remains unsolved even after the Bohr and Weeler`s study in 1939. Especially, it is marked in respect of mass distribution in unsymmetric nuclear fission. The energy dependency of mass distribution can be explained with an assumption of 2-mode nuclear fission. Further, it was demonstrated that the symmetrical fission components and the unsymmetrical ones have different saddle and fission points. Thus, the presence of the 2-mode fission mechanism was confirmed. Here, transition in the nuclear fission mechanism and its cause were investigated here. As the cause of such transition, plausible four causes; a contribution of multiple-chance fission, disappearance of shell effects, beginning of fission following collective excitation due to GDR and nuclear phase transition were examined in the condition of excitation energy of 14.0 MeV. And it was suggested that the transition in the nuclear fission concerned might be related to phase transition. In addition, the mechanism of nuclear fission at a low energy and multi-mode hypothesis were examined by determination of the energy for thermal neutron fission ({sup 233,235}U and {sup 239}Pu) and spontaneous nuclear fission ({sup 252}Cf). (M.N.)
Report on simulation of fission gas and fission product diffusion in UO_{2}
Energy Technology Data Exchange (ETDEWEB)
Andersson, Anders David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Perriot, Romain Thibault [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Pastore, Giovanni [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Tonks, Michael R. [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Cooper, Michael William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Goyal, Anuj [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Uberuaga, Blas P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Stanek, Christopher Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division
2016-07-22
In UO_{2} nuclear fuel, the retention and release of fission gas atoms such as xenon (Xe) are important for nuclear fuel performance by, for example, reducing the fuel thermal conductivity, causing fuel swelling that leads to mechanical interaction with the clad, increasing the plenum pressure and reducing the fuel–clad gap thermal conductivity. We use multi-scale simulations to determine fission gas diffusion mechanisms as well as the corresponding rates in UO_{2} under both intrinsic and irradiation conditions. In addition to Xe and Kr, the fission products Zr, Ru, Ce, Y, La, Sr and Ba have been investigated. Density functional theory (DFT) calculations are used to study formation, binding and migration energies of small clusters of Xe atoms and vacancies. Empirical potential calculations enable us to determine the corresponding entropies and attempt frequencies for migration as well as investigate the properties of large clusters or small fission gas bubbles. A continuum reaction-diffusion model is developed for Xe and point defects based on the mechanisms and rates obtained from atomistic simulations. Effective fission gas diffusivities are then obtained by solving this set of equations for different chemical and irradiation conditions using the MARMOT phase field code. The predictions are compared to available experimental data. The importance of the large Xe_{U3O} cluster (a Xe atom in a uranium + oxygen vacancy trap site with two bound uranium vacancies) is emphasized, which is a consequence of its high mobility and high binding energy. We find that the Xe_{U3O} cluster gives Xe diffusion coefficients that are higher for intrinsic conditions than under irradiation over a wide range of temperatures. Under irradiation the fast-moving Xe_{U3O} cluster recombines quickly with irradiation induced interstitial U ions, while this mechanism is less important for intrinsic conditions. The net result is higher
Report on simulation of fission gas and fission product diffusion in UO_{2}
Energy Technology Data Exchange (ETDEWEB)
Andersson, Anders David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Perriot, Romain Thibault [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Pastore, Giovanni [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Tonks, Michael R. [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Cooper, Michael William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Goyal, Anuj [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Uberuaga, Blas P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Stanek, Christopher Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division
2016-07-22
In UO_{2} nuclear fuel, the retention and release of fission gas atoms such as xenon (Xe) are important for nuclear fuel performance by, for example, reducing the fuel thermal conductivity, causing fuel swelling that leads to mechanical interaction with the clad, increasing the plenum pressure and reducing the fuel–clad gap thermal conductivity. We use multi-scale simulations to determine fission gas diffusion mechanisms as well as the corresponding rates in UO_{2} under both intrinsic and irradiation conditions. In addition to Xe and Kr, the fission products Zr, Ru, Ce, Y, La, Sr and Ba have been investigated. Density functional theory (DFT) calculations are used to study formation, binding and migration energies of small clusters of Xe atoms and vacancies. Empirical potential calculations enable us to determine the corresponding entropies and attempt frequencies for migration as well as investigate the properties of large clusters or small fission gas bubbles. A continuum reaction-diffusion model is developed for Xe and point defects based on the mechanisms and rates obtained from atomistic simulations. Effective fission gas diffusivities are then obtained by solving this set of equations for different chemical and irradiation conditions using the MARMOT phase field code. The predictions are compared to available experimental data. The importance of the large Xe_{U3O} cluster (a Xe atom in a uranium + oxygen vacancy trap site with two bound uranium vacancies) is emphasized, which is a consequence of its high mobility and high binding energy. We find that the Xe_{U3O} cluster gives Xe diffusion coefficients that are higher for intrinsic conditions than under irradiation over a wide range of temperatures. Under irradiation the fast-moving Xe_{U3O} cluster recombines quickly with irradiation-induced interstitial U ions, while this mechanism is less important for intrinsic conditions. The net result is higher
Fusion and fission: membrane trafficking in animal cytokinesis.
Finger, Fern P; White, John G
2002-03-22
Cytokinesis is the physical act of separating daughter cells, allowing them to become separate entities. Recent studies have revealed that membrane insertion for furrowing and scission of the residual bridge is a key aspect of animal cytokinesis.
Fission, spallation or fusion-based neutron sources
Indian Academy of Sciences (India)
Kurt N Clausen
2008-10-01
In this paper the most promising technology for high power neutron sources is briefly discussed. The conclusion is that the route to high power neutron sources in the foreseeable future is spallation – short or long pulse or even CW – all of these sources will have areas in which they excel.
Genetically Controlled Fusion, Exocytosis and Fission of Artificial Vesicles
DEFF Research Database (Denmark)
Bönzli, Eva; Hadorn, Maik; De Lucrezia, Davide
Artificial vesicles represent ideal candidates as a model for artificial cells. It was shown that artificial genetic programs and the required cellular machinery (cell-free expression systems) can be incorporated into vesicles and allow the synthesis of proteins. Vesicles were shown to fuse...
Lemaître, J.-F.; Dubray, N.; Hilaire, S.; Panebianco, S.; Sida, J.-L.
2013-12-01
Our purpose is to determine fission fragments characteristics in a framework of a scission point model named SPY for Scission Point Yields. This approach can be considered as a theoretical laboratory to study fission mechanism since it gives access to the correlation between the fragments properties and their nuclear structure, such as shell correction, pairing, collective degrees of freedom, odd-even effects. Which ones are dominant in final state? What is the impact of compound nucleus structure? The SPY model consists in a statistical description of the fission process at the scission point where fragments are completely formed and well separated with fixed properties. The most important property of the model relies on the nuclear structure of the fragments which is derived from full quantum microscopic calculations. This approach allows computing the fission final state of extremely exotic nuclei which are inaccessible by most of the fission model available on the market.
Directory of Open Access Journals (Sweden)
Lemaître J.-F.
2013-12-01
Full Text Available Our purpose is to determine fission fragments characteristics in a framework of a scission point model named SPY for Scission Point Yields. This approach can be considered as a theoretical laboratory to study fission mechanism since it gives access to the correlation between the fragments properties and their nuclear structure, such as shell correction, pairing, collective degrees of freedom, odd-even effects. Which ones are dominant in final state? What is the impact of compound nucleus structure? The SPY model consists in a statistical description of the fission process at the scission point where fragments are completely formed and well separated with fixed properties. The most important property of the model relies on the nuclear structure of the fragments which is derived from full quantum microscopic calculations. This approach allows computing the fission final state of extremely exotic nuclei which are inaccessible by most of the fission model available on the market.
Photon and proton induced fission on heavy nuclei at intermediate energies
Directory of Open Access Journals (Sweden)
Andrade-II E.
2014-04-01
Full Text Available We present an analysis of fission induced by intermediate energy protons or photons on actinides. The 660 MeV proton induced reactions are on 241Am, 238U, and 237Np targets and the Bremmstrahlung-photons with end-point energies at 50 MeV and 3500 MeV are on 232Th and 238U targets. The study was performed by means of the Monte Carlo simulation code CRISP. A multimodal fission extension was added to the code within an approach which accounts for the contribution of symmetric and asymmetric fission. This procedure allowed the investigation of fission cross sections, fissility, number of evaporated nucleons and fission-fragment charge distributions. The comparison with experimental data show a good agreement between calculations and experiments.
High-Resolution Correlated Fission Product Measurements of 235U (nth , f) with SPIDER
Shields, Dan; Spider Team
2015-10-01
The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) has obtained high-resolution, moderate-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (ν), and total kinetic energy (TKE). These data will be some of the first of their kind available to nuclear data evaluations. An overview of the SPIDER detector, analytical method, and preliminary results for 235U (nth , f) will be presented. LA-UR-15-20130 This work benefited from the use of the LANSCE accelerator facility and was performed under the auspices of the US Department of Energy by Los Alamos Security, LLC under Contract DE-AC52-06NA25396.
Comparative study of metal cluster fission in Hartree-Fock and LDA
Lyalin, A; Greiner, W; Lyalin, Andrey; Solov'yov, Andrey; Greiner, Walter
2001-01-01
Fission of doubly charged metal clusters is studied using the open-shell two-center deformed jellium Hartree-Fock model and Local Density Approximation. Results of calculations of the electronic structure and fission barriers for the symmetric and asymmetric channels associated with the following processes Na_{10}^{2+} --> Na_{7}^{+} + Na_{3}^{+}, Na_{18}^{2+} --> Na_{15}^{+} + Na_{3}^{+} and Na_{18}^{2+} --> 2 Na_{9}^{+} are presented. The role of the exact exchange and many-body correlation effects in metal clusters fission is analysed. It is demonstrated that the influence of many-electron correlation effects on the height of the fission barrier is more profound if the barrier arises nearby or beyond the scission point. The importance of cluster deformation effects in the fission process is elucidated with the use of the overlapping-spheroids shape parametrization allowing one an independent variation of deformations in the parent and daughter clusters.
Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling
Energy Technology Data Exchange (ETDEWEB)
Pastore, Giovanni, E-mail: Giovanni.Pastore@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Swiler, L.P., E-mail: LPSwile@sandia.gov [Optimization and Uncertainty Quantification, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-1318 (United States); Hales, J.D., E-mail: Jason.Hales@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Novascone, S.R., E-mail: Stephen.Novascone@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Perez, D.M., E-mail: Danielle.Perez@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Spencer, B.W., E-mail: Benjamin.Spencer@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Luzzi, L., E-mail: Lelio.Luzzi@polimi.it [Politecnico di Milano, Department of Energy, Nuclear Engineering Division, via La Masa 34, I-20156 Milano (Italy); Van Uffelen, P., E-mail: Paul.Van-Uffelen@ec.europa.eu [European Commission, Joint Research Centre, Institute for Transuranium Elements, Hermann-von-Helmholtz-Platz 1, D-76344 Karlsruhe (Germany); Williamson, R.L., E-mail: Richard.Williamson@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States)
2015-01-15
The role of uncertainties in fission gas behavior calculations as part of engineering-scale nuclear fuel modeling is investigated using the BISON fuel performance code with a recently implemented physics-based model for fission gas release and swelling. Through the integration of BISON with the DAKOTA software, a sensitivity analysis of the results to selected model parameters is carried out based on UO{sub 2} single-pellet simulations covering different power regimes. The parameters are varied within ranges representative of the relative uncertainties and consistent with the information in the open literature. The study leads to an initial quantitative assessment of the uncertainty in fission gas behavior predictions with the parameter characterization presently available. Also, the relative importance of the single parameters is evaluated. Moreover, a sensitivity analysis is carried out based on simulations of a fuel rod irradiation experiment, pointing out a significant impact of the considered uncertainties on the calculated fission gas release and cladding diametral strain. The results of the study indicate that the commonly accepted deviation between calculated and measured fission gas release by a factor of 2 approximately corresponds to the inherent modeling uncertainty at high fission gas release. Nevertheless, significantly higher deviations may be expected for values around 10% and lower. Implications are discussed in terms of directions of research for the improved modeling of fission gas behavior for engineering purposes.
Systematics on fission fragment mass distribution of neutron induced 235U fission
Institute of Scientific and Technical Information of China (English)
LIU Ting-Jin; SUN Zheng-Jun; SHU Neng-Chuan
2008-01-01
Based on the neutron induced fission fragment mass distribution data up to neutron energy 20 MeV measured with the double kinetic energy method (KEM) and the radio active method (RAM), the systematics of fission fragment mass distribution was investigated by using 5 Gaussian model and the systematics parameters were obtained by fitting the experimental data. With the systematics, the yields of any mass A and at any energy in the region from 0 to 20 MeV of neutron energy can be calculated. The calculated results could well reproduce the experimental data measured with KEM, but show some systematical deviation from the data measured by RAM, which reflects some systematical deviations between the two kinds of measured data.The error of systematics yield was calculated in an exact error transformation way, including from the error of the experimental yield data to the error of the discrete parameters, then to the systematics parameters,and at last to the yield calculated with systematics.
Energy Technology Data Exchange (ETDEWEB)
none,
1989-01-01
This paper discuses the following topics on fusion reactor materials: irradiation, facilities, test matrices, and experimental methods; dosimetry, damage parameters, and activation calculations; materials engineering and design requirements; fundamental mechanical behavior; radiation effects; development of structural alloys; solid breeding materials; and ceramics.
Search for Singlet Fission Chromophores
Energy Technology Data Exchange (ETDEWEB)
Havlas, Z.; Akdag, A.; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, J.
2012-01-01
Singlet fission, in which a singlet excited chromophore shares its energy with a ground-state neighbor and both end up in their triplet states, is of potential interest for solar cells. Only a handful of compounds, mostly alternant hydrocarbons, are known to perform efficiently. In view of the large number of conditions that a successful candidate for a practical cell has to meet, it appears desirable to extend the present list of high performers to additional classes of compounds. We have (i) identified design rules for new singlet fission chromophores and for their coupling to covalent dimers, (ii) synthesized them, and (iii) evaluated their performance as neat solids or covalent dimers.
Setup for Fission and Evaporation Cross-Section Measurements in Reactions Induced by Secondary Beams
Hassan, A A; Kalpakchieva, R; Skobelev, N K; Penionzhkevich, Yu E; Dlouhý, Z; Radnev, S; Poroshin, N V
2002-01-01
A setup for studying reactions induced by secondary radioactive beams has been constructed. It allows simultaneous measurement of alpha-particle and fission fragment energy spectra. By measuring the alpha-particles, identification of evaporation residues is achieved. A set of three targets can be used so as to ensure sufficient statistics. Two silicon detectors, located at 90 degrees to the secondary beam direction, face each target, thus covering 30 % of the solid angle. This experimental setup is to be used to obtain excitation functions of fusion?fission reactions and of reactions leading to evaporation residue production.
Nuclear dissipation effects on fission and evaporation in systems of intermediate fissility
Directory of Open Access Journals (Sweden)
Gelli N.
2010-03-01
Full Text Available The systems of intermediate fissility 132Ce and 158Er have been studied experimentally and theoretically in order to investigate the dissipation properties of nuclear matter. Cross sections of fusion-fission and evaporation residues channels together with charged particles multiplicities in both channels, their spectra, angular correlations and mass-energy distribution of fission fragments have been measured. Theoretical analysis has been performed using multi-dimensional stochastic approach with realistic treatment of particle evaporation. The results of analysis show that full one-body or unusually strong two-body dissipation allows to reproduce experimental data. No temperature dependent dissipation was needed.
Mitochondrial Fusion Proteins and Human Diseases
Directory of Open Access Journals (Sweden)
Michela Ranieri
2013-01-01
Full Text Available Mitochondria are highly dynamic, complex organelles that continuously alter their shape, ranging between two opposite processes, fission and fusion, in response to several stimuli and the metabolic demands of the cell. Alterations in mitochondrial dynamics due to mutations in proteins involved in the fusion-fission machinery represent an important pathogenic mechanism of human diseases. The most relevant proteins involved in the mitochondrial fusion process are three GTPase dynamin-like proteins: mitofusin 1 (MFN1 and 2 (MFN2, located in the outer mitochondrial membrane, and optic atrophy protein 1 (OPA1, in the inner membrane. An expanding number of degenerative disorders are associated with mutations in the genes encoding MFN2 and OPA1, including Charcot-Marie-Tooth disease type 2A and autosomal dominant optic atrophy. While these disorders can still be considered rare, defective mitochondrial dynamics seem to play a significant role in the molecular and cellular pathogenesis of more common neurodegenerative diseases, for example, Alzheimer’s and Parkinson’s diseases. This review provides an overview of the basic molecular mechanisms involved in mitochondrial fusion and focuses on the alteration in mitochondrial DNA amount resulting from impairment of mitochondrial dynamics. We also review the literature describing the main disorders associated with the disruption of mitochondrial fusion.
Energy Technology Data Exchange (ETDEWEB)
Zhao, Lantao; Li, Shuhong; Wang, Shilei, E-mail: wshlei@aliyun.com; Yu, Ning; Liu, Jia
2015-06-05
The mitochondrial calcium uniporter (MCU) transports free Ca{sup 2+} into the mitochondrial matrix, maintaining Ca{sup 2+} homeostasis, thus regulates the mitochondrial morphology. Previous studies have indicated that there was closely crosstalk between MCU and mitochondrial fission during the process of ischemia/reperfusion injury. This study constructed a hypoxia reoxygenation model using primary hippocampus neurons to mimic the cerebral ischemia/reperfusion injury and aims to explore the exactly effect of MCU on the mitochondrial fission during the process of ischemia/reperfusion injury and so as the mechanisms. Our results found that the inhibitor of the MCU, Ru360, decreased mitochondrial Ca{sup 2+} concentration, suppressed the expression of mitochondrial fission protein Drp1, MIEF1 and Fis1, and thus improved mitochondrial morphology significantly. Whereas spermine, the agonist of the MCU, had no significant impact compared to the I/R group. This study demonstrated that the MCU regulates the process of mitochondrial fission by controlling the Ca{sup 2+} transport, directly upregulating mitochondrial fission proteins Drp1, Fis1 and indirectly reversing the MIEF1-induced mitochondrial fusion. It also provides new targets for brain protection during ischemia/reperfusion injury. - Highlights: • We study MCU with primary neuron culture. • MCU induces mitochondrial fission. • MCU reverses MIEF1 effect.
Chemical state of fission products in irradiated UO 2
Imoto, S.
1986-08-01
The chemical state of fission products in irradiated UO 2 fuel has been estimated for FBR as well as LWR on the basis of equilibrium calculation with the SOLGASMIX-PV code. The system considered for the calculation is composed of a gas phase, a CaF 2 type oxide phase, three grey phases, a noble metal alloy, a mixed telluride phase and several other phases each consisting of single compound. The distribution of elements into these phases and the amount of chemical species in each phase at different temperatures are obtained as a function of oxygen potential for LWR and FBR. Changes of the chemical potential of the fuel-fission products system during burnup are also evaluated with particular attention to the difference between LWR and FBR. Some informations obtained by the calculation are compared with the results of post irradiation examination of UO 2 fuels.
Energy Technology Data Exchange (ETDEWEB)
Keney, G.S.
1981-08-01
A computer code has been written to calculate neutron induced activation of neutral-beam injector components and the corresponding dose rates as a function of geometry, component composition, and time after shutdown. The code, ACDOS1, was written in FORTRAN IV to calculate both activity and dose rates for up to 30 target nuclides and 50 neutron groups. Sufficient versatility has also been incorporated into the code to make it applicable to a variety of general activation problems due to neutrons of energy less than 20 MeV.
Comparison of {sup 235}U fission cross sections in JENDL-3.3 and ENDF/B-VI
Energy Technology Data Exchange (ETDEWEB)
Kawano, Toshihiko [Kyushu Univ., Fukuoka (Japan); Carlson, Allan D. [National Institute of Standards and Technology (United States); Matsunobu, Hiroyuki [Data Engineering, Inc., Fujisawa, Kanagawa (Japan); Nakagawa, Tsuneo; Shibata, Keiichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Talou, Patrick; Young, Philip G.; Chadwick, Mark B. [Los Alamos National Laboratory, Los Alamos, NM (United States)
2002-01-01
Comparisons of evaluated fission cross sections for {sup 235}U in JENDL-3.3 and ENDF/B-VI are carried out. The comparisons are made for both the differential and integral data. The fission cross sections as well as the fission ratios are compared with the experimental data in detail. Spectrum averaged cross sections are calculated and compared with the measurements. The employed spectra are the {sup 235}U prompt fission neutron spectrum, the {sup 252}Cf spontaneous fission neutron spectrum, and the neutron spectrum produced by a {sup 9}Be(d, xn) reaction. For {sup 235}U prompt fission neutron spectrum, the ENDF/B-VI evaluation reproduces experimental averaged cross sections. For {sup 252}Cf and {sup 9}Be(d, xn) neutron spectra, the JENDL-3.3 evaluation gives better results than ENDF/B-VI. (author)
Regnier, D; Schunck, N; Verriere, M
2016-01-01
Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r-process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data is available is an incentive to develop a fully microscopic approach to fission dynamics. In this work, we calculate the pre-neutron emission charge and mass distributions of the fission fragments formed in the neutron-induced fission of 239Pu using a microscopic method based on nuclear energy density functional (EDF) method, where large amplitude collective motion is treated adiabatically using the time dependent generator coordinate method (TDGCM) under the Gaussian overlap approximation (GOA). Fission fragment distributions are extracted from the flux of the collective wave packet through the scission line. We find that the main characteristics of the fission charge and mass distributions can be well reproduced by existing energy functionals even in tw...
Radiochemistry and the Study of Fission
Energy Technology Data Exchange (ETDEWEB)
Rundberg, Robert S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-11-14
These are slides from a lecture given at UC Berkeley. Radiochemistry has been used to study fission since it’ discovery. Radiochemical methods are used to determine cumulative mass yields. These measurements have led to the two-mode fission hypothesis to model the neutron energy dependence of fission product yields. Fission product yields can be used for the nuclear forensics of nuclear explosions. The mass yield curve depends on both the fuel and the neutron spectrum of a device. Recent studies have shown that the nuclear structure of the compound nucleus can affect the mass yield distribution. The following topics are covered: In the beginning: the discovery of fission; forensics using fission products: what can be learned from fission products, definitions of R-values and Q-values, fission bases, K-factors and fission chambers, limitations; the neutron energy dependence of the mass yield distribution (the two mode fission hypothesis); the influence of nuclear structure on the mass yield distribution. In summary: Radiochemistry has been used to study fission since it’s discovery. Radiochemical measurement of fission product yields have provided the highest precision data for developing fission models and for nuclear forensics. The two-mode fission hypothesis provides a description of the neutron energy dependence of the mass yield curve. However, data is still rather sparse and more work is needed near second and third chance fission. Radiochemical measurements have provided evidence for the importance of nuclear states in the compound nucleus in predicting the mass yield curve in the resonance region.
Directory of Open Access Journals (Sweden)
Salahuddin Asif
2013-01-01
Full Text Available Multiple recycling of actinides and non-volatile fission products in fast reactors through the dry re-fabrication/reprocessing atomics international reduction oxidation process has been studied as a possible way to reduce the long-term potential hazard of nuclear waste compared to that resulting from reprocessing in a wet PUREX process. Calculations have been made to compare the actinides and fission products recycling scheme with the normal plutonium recycling scheme in a fast reactor. For this purpose, the Karlsruhe version of isotope generation and depletion code, KORIGEN, has been modified accordingly. An entirely novel fission product yields library for fast reactors has been created which has replaced the old KORIGEN fission products library. For the purposes of this study, the standard 26 groups data set, KFKINR, developed at Forschungszentrum Karlsruhe, Germany, has been extended by the addition of the cross-sections of 13 important actinides and 68 most important fission products. It has been confirmed that these 68 fission products constitute about 95% of the total fission products yield and about 99.5% of the total absorption due to fission products in fast reactors. The amount of fissile material required to guarantee the criticality of the reactor during recycling schemes has also been investigated. Cumulative high active waste per ton of initial heavy metal is also calculated. Results show that the recycling of actinides and fission products in fast reactors through the atomics international reduction oxidation process results in a reduction of the potential hazard of radioactive waste.
Effects of Isospin Equilibrium on Cold Fusion of Superheavy Nuclei
Institute of Scientific and Technical Information of China (English)
LIU Zu-Hua; BAO Jing-Dong
2005-01-01
@@ The neutron flow model predicts that neutrons start to flow freely between the approaching nuclei 58Fe and 208 Pb at s = 3fm, a length in which the effective surfaces of these nuclei are 3fm apart. As a result of neutron flow,the N/Z value rapidly reaches an equilibrium distribution. Meanwhile the system, originally in the fusion valley,is injected into the asymmetric fission valley. The dynamic process of the composite nucleus in the asymmetric fission valley is treated with a two-parameter Smoluchowski equation. It is shown that the probability to overcome the asymmetric fission barrier and to achieve compound nucleus configuration, hence the fusion cross section is obviously suppressed due to the effect of isospin equilibrium.
Confused about Fusion? Weed Your Science Collection with a Pro.
O'Dell, Charli
1998-01-01
Provides guidelines on weeding science collections in junior high/high school libraries. Highlights include checking copyright dates, online sources, 13 science subject areas that deserve special consideration (plate tectonics, fission, fusion, radioactive dating, weather/climate, astronomy/space science, elements, integrated science,…
Background and Derivation of ANS-5.4 Standard Fission Product Release Model
Energy Technology Data Exchange (ETDEWEB)
Beyer, Carl E.; Turnbull, Andrew J.
2010-01-29
This background report describes the technical basis for the newly proposed American Nuclear Society (ANS) 5.4 standard, Methods for Calculating the Fractional Release of Volatile Fission Products from Oxide Fuels. The proposed ANS 5.4 standard provides a methodology for determining the radioactive fission product releases from the fuel for use in assessing radiological consequences of postulated accidents that do not involve abrupt power transients. When coupled with isotopic yields, this method establishes the 'gap activity,' which is the inventory of volatile fission products that are released from the fuel rod if the cladding are breached.
Two neutron correlations in photo-fission
Dale, D. S.; Kosinov, O.; Forest, T.; Burggraf, J.; Stave, S.; Warren, G.; Starovoitova, V.
2016-09-01
A large body of experimental work has established the strong kinematical correlation between fission fragments and fission neutrons. Here, we report on the progress of investigations of the potential for strong two neutron correlations arising from the nearly back-to-back nature of the two fission fragments that emit these neutrons in the photo-fission process. In initial measurements, a pulsed electron linear accelerator was used to generate bremsstrahlung photons that impinged upon an actinide target, and the energy and opening angle distributions of coincident neutrons were measured using a large acceptance neutron detector array. A planned comprehensive set of measurements of two neutron correlations in the photo-fission of actinides is expected to shed light on several fundamental aspects of the fission process including the multiplicity distributions associated with the light and heavy fission fragments, the nuclear temperatures of the fission fragments, and the mass distribution of the fission fragments as a function of energy released. In addition to these measurements providing important nuclear data, the unique kinematics of fission and the resulting two neutron correlations have the potential to be the basis for a new tool to detect fissionable materials. A key technical challenge of this program arises from the need to perform coincidence measurements with a low duty factor, pulsed electron accelerator. This has motivated the construction of a large acceptance neutron detector array, and the development of data analysis techniques to directly measure uncorrelated two neutron backgrounds.
Fission dynamics at low excitation energy
Aritomo, Y
2013-01-01
The origin of mass asymmetry in the fission of uranium at a low excitation energy is clarified by a trajectory analysis of the Langevin equation. The positions of the peaks in the mass distribution of fission fragments are mainly determined by fission saddle points originating from the shell correction energy. The widths of the peaks, on the other hand, result from a shape fluctuation around the scission point caused by the random force in the Langevin equation. We found that a random vibration in the oblate direction of fissioning fragments is essential for the fission process. According to this picture, fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup. This is expected to lead to a new viewpoint of fission dynamics and the splitting mechanism.
Fission yield studies at the IGISOL facility
Energy Technology Data Exchange (ETDEWEB)
Penttilae, H.; Elomaa, V.V.; Eronen, T.; Hakala, J.; Jokinen, A.; Kankainen, A.; Moore, I.D.; Rahaman, S.; Rinta-Antila, S.; Rissanen, J.; Saastamoinen, A.; Weber, C.; Aeystoe, J. [University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland); Rubchenya, V. [University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland); V.G. Khlopin Radium Institute, St. Petersburg (Russian Federation)
2012-04-15
Low-energy-particle-induced fission is a cost-effective way to produce neutron-rich nuclei for spectroscopic studies. Fission has been utilized at the IGISOL to produce isotopes for decay and nuclear structure studies, collinear laser spectroscopy and precision mass measurements. The ion guide technique is also very suitable for the fission yield measurements, which can be performed very efficiently by using the Penning trap for fission fragment identification and counting. The proton- and neutron-induced fission yield measurements at the IGISOL are reviewed, and the independent isotopic yields of Zn, Ga, Rb, Sr, Cd and In in 25MeV deuterium-induced fission are presented for the first time. Moving to a new location next to the high intensity MCC30/15 light-ion cyclotron will allow also the use of the neutron-induced fission to produce the neutron rich nuclei at the IGISOL in the future. (orig.)
Indian Academy of Sciences (India)
ESLAMIZADEH HADI
2016-07-01
A stochastic approach to fission dynamics based on two-dimensional Langevin equations was applied to calculate the anisotropy of the fission fragments angular distribution and average pre-scission neutron multiplicities for the compound nucleus 248Cf formed in the $${16}$O+$^{232}$Th reactions. Postsaddle nuclear dissipation strength of $(12–14) \\times 10^{21} s^{−1}$ was extracted for Cf nucleus by fitting the results of calculations with the experimentaldata. Furthermore, it was found that the results of calculations for the anisotropy of the fission fragments angular distribution and pre-scission neutron multiplicities are very sensitive to the magnitude of post-saddle nucleardissipation.
Energy Technology Data Exchange (ETDEWEB)
Suh, Suk Yong; Sung, Ki Woong; Kang, Joo Sang; Lee, Jong Jik [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
1995-02-01
So called `cold fusion phenomena` are not confirmed yet. Excess heat generation is very delicate one. Neutron generation is most reliable results, however, the records are erratic and the same results could not be repeated. So there is no reason to exclude the malfunction of testing instruments. The same arguments arise in recording {sup 4}He, {sup 3}He, {sup 3}H, which are not rich in quantity basically. An experiment where plenty of {sup 4}He were recorded is attached in appendix. The problem is that we are trying to search cold fusion which is permitted by nature or not. The famous tunneling effect in quantum mechanics will answer it, however, the most fusion rate is known to be negligible. The focus of this project is on the theme that how to increase that negligible fusion rate. 6 figs, 4 tabs, 1512 refs. (Author).
... results in predictable healing. Autograft is currently the “gold standard” source of bone for a fusion. The ... pump. With this technique, the patient presses a button that delivers a predetermined amount of narcotic pain ...
Multidimensionally-constrained relativistic Hartree-Bogoliubov study of nuclear spontaneous fission
Zhao, Jie; Niksic, Tamara; Vretenar, Dario
2015-01-01
Recent microscopic studies, based on the theoretical framework of nuclear energy density functionals, have analyzed dynamic (least action) and static (minimum energy) fission paths, and it has been shown that in addition to the important role played by nonaxial and/or octupole collective degrees of freedom, fission paths crucially depend on the approximations adopted in calculating the collective inertia. The dynamics of spontaneous fission of $^{264}$Fm and $^{250}$Fm is explored. The fission paths, action integrals and the corresponding half-lives predicted by the functionals PC-PK1 and DD-PC1 are compared and, in the case of $^{264}$Fm, discussed in relation with recent results obtained using the HFB model based on the Skyrme functional SkM$^*$ and a density dependent mixed pairing interaction. Deformation energy surfaces, collective potentials, and perturbative and nonperturbative cranking collective inertia tensors are calculated using the multidimensionally-constrained relativistic Hartree-Bogoliubov (M...
Precise determination of the 235U reactor antineutrino cross section per fission
Giunti, C.
2017-01-01
We investigate which among the reactor antineutrino fluxes from the decays of the fission products of 235U, 238U, 239Pu, and 241Pu may be responsible for the reactor antineutrino anomaly if the anomaly is due to a miscalculation of the antineutrino fluxes. We find that it is very likely that at least the calculation of the 235U flux must be revised. From the fit of the data we obtain the precise determination σ235 = (6.33 ± 0.08) ×10-43cm2 /fission of the 235U cross section per fission, which is more precise than the calculated value and differs from it by 2.2σ. The cross sections per fission of the other fluxes have large uncertainties and in practice their values are undetermined by the fit.
Institute of Scientific and Technical Information of China (English)
喻章程; 解衡
2013-01-01
The simulation and numerical computation with FLUENT code are conducted for the fuel zone of fusion-fission hybrid reactor.Two coolant flowing arrangement schemes,uniform flow,and proportional flow based on the gross heat of each fuel cell,are compared for optimization.The results of the numerical computation show that the heat conduction between adjacent fuel cells is weak and the heat is carried away by the coolant in the duct,and it is almost completely equal to the heat produced by corresponding fuel cell except the fuel cell 1.Then the value of heat structure of the coolant duct is the gross heat of each fuel cell that means there is no need to remodel the fuel zone with system analysis program.The fuel zone has lower maximum temperature and more even temperature distribution in the case of proportional flow compared with uniform flow,but the effect of flattening temperature is not obvious.The capacity of heat transfer of ex-core nature circulation in the imaginary LOCA is also evaluated.The results show that the reactor core will be melted within 520s after shut-down without the nature circulation and the maximum temperature in the fuel region will be only elevated to 584.4℃ within 1000s after shut-down if with the nature circulation.%根据聚变-裂变混合堆概念堆型的燃料区水冷设计,通过FLUENT建模和模拟计算,比较了均匀流量和按燃料单元发热量比例分配流量两种冷却剂布置方案.数值计算结果表明,这两种布置方案中燃料单元之间的导热很小,除燃料单元1中冷却管道外,其余的冷却管道带走的热量几乎等于相应燃料单元的发热量,在用系统分析程序等效建模时,不必重新确定冷却管道的热构件；对后一种布置方案燃料区的最高温度更低,温度分布更均匀,但温度展平效果并不明显.计算了堆外自然循环系统在假设的失水事故(LOCA)中的导热能力.结果表明,如果不采用自然循环系统,停堆后520s
The fundamental role of fission during r-process nucleosynthesis in neutron star mergers
Energy Technology Data Exchange (ETDEWEB)
Goriely, S. [Universite Libre de Bruxelles, Institut d' Astronomie et d' Astrophysique, CP-226, Brussels (Belgium)
2015-02-01
The rapid neutron-capture process, or r-process, is known to be of fundamental importance for explaining the origin of approximately half of the A > 60 stable nuclei observed in nature. Despite important efforts, the astrophysical site of the r-process remains unidentified. Here we study r-process nucleosynthesis in a material that is dynamically ejected by tidal and pressure forces during the merging of binary neutron stars. r-process nucleosynthesis during the decompression is known to be largely insensitive to the detailed astrophysical conditions because of efficient fission recycling, producing a composition that closely follows the solar r-abundance distribution for nuclei with mass numbers A > 140. Due to the important role played by fission in such a scenario, the impact of fission is carefully analyzed. We consider different state-of-the-art global models for the determination of the fission paths, nuclear level densities at the fission saddle points and fission fragment distributions. Based on such models, the sensitivity of the calculated r-process abundance distribution is studied. The fission path is found to strongly affect the region of heavy nuclei responsible for the fission recycling, while the fission fragment distribution of nuclei along the A ≅ 278 isobars defines the abundance pattern of nuclei produced in the 110
Study of dissipative dynamics in fission of hot nuclei using Langevin equation
Chaudhuri, G
2004-01-01
The fission of highly excited compound nuclei formed in heavy ion induced fusion reactions has emerged as a topic of considerable interest in the recent years. Dissipative dynamical models based on the Langevin equation were developed and were applied successfully for fission dynamics of highly excited heavy nuclei. However, Wall Friction(WF), the standard version of nuclear friction when incorporated in the Langevin dynamical model was not able to reproduce simultaneously experimental data for both prescission neutron multiplicity and fission probability. Consequently, an empirical reduction in the strength of the wall friction was found necessary to reproduce the experimental numbers by many workers. Interestingly, a modification of the wall friction was proposed recently where the reduction was achieved microscopically. This modified version is known as the chaos weighted wall friction(CWWF) which takes into account non-integrability of single particle motion. The work in my thesis aims at using this stron...
A fission fragment detector for correlated fission output studies
Energy Technology Data Exchange (ETDEWEB)
Mosby, S., E-mail: smosby@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Tovesson, F.; Couture, A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Duke, D.L. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colorado School of Mines, Golden, CO 80401 (United States); Kleinrath, V. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Idaho State University, Pocatello, ID 83201 (United States); Meharchand, R.; Meierbachtol, K.; O' Donnell, J.M.; Perdue, B.; Richman, D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Shields, D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Colorado School of Mines, Golden, CO 80401 (United States)
2014-09-01
A digital data acquisition system has been combined with a double Frisch gridded ionization chamber for use at both moderated and unmoderated neutron sources at the Los Alamos Neutron Science (LANSCE) facility. The high efficiency of the instrument combined with intense LANSCE beams and new acquisition system permits fission output measurements across 11 orders of magnitude incident neutron energy. The acquisition and analysis system is presented along with the first in-beam performance tests of the setup.
Cluster fission from the standpoint of nuclear fission
Energy Technology Data Exchange (ETDEWEB)
Lee, Sangmoo [Tsukuba Univ., Ibaraki (Japan). Inst. of Physics
1996-03-01
Atomic nucleus belongs to a quantal finite many body system. Nucleus shows great resemblance to cluster, above all metal cluster, although the strength of interaction is different. The works of Brechignac group, Saunder, Martin and P. Froeblich are explained by the critical size Nc as the central term. The differences between cluster and nucleus are investigated and a future view of cluster fission is explained. (S.Y.)
Stochastic approaches to dynamics of heavy ion collisions, the case of thermal fission
Energy Technology Data Exchange (ETDEWEB)
Boilley, D.; Abe, Y. [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Suraud, E. [Universite Paul Sabatier, 31 - Toulouse (France). Lab. de Physique Quantique; Ayik, S. [Tennessee Technological Univ., Cookeville, TN (United States)
1994-03-30
In order to study the influence of fluctuations on various phenomena linked to heavy ion collisions, a Langevin equation has been derived from a microscopic model. Parameters entering this equation are completely determined from microscopic quantities characterizing nuclear matter. This equation has been applied to various phenomena at intermediate energies. This paper focuses on large amplitude motions and especially thermal fission. Fission rate is calculated and compared to experimental results.
Analysis of the effect of UO{sub 2} high burnup microstructure on fission gas release
Energy Technology Data Exchange (ETDEWEB)
Jernkvist, Lars Olof; Massih, Ali [Quantum Technologies AB, Uppsala Science Park (Sweden)
2002-10-01
This report deals with high-burnup phenomena with relevance to fission gas release from UO{sub 2} nuclear fuel. In particular, we study how the fission gas release is affected by local buildup of fissile plutonium isotopes and fission products at the fuel pellet periphery, with subsequent formation of a characteristic high-burnup rim zone micro-structure. An important aspect of these high-burnup effects is the degradation of fuel thermal conductivity, for which prevalent models are analysed and compared with respect to their theoretical bases and supporting experimental data. Moreover, the Halden IFA-429/519.9 high-burnup experiment is analysed by use of the FRAPCON3 computer code, into which modified and extended models for fission gas release are introduced. These models account for the change in Xe/Kr-ratio of produced and released fission gas with respect to time and space. In addition, several alternative correlations for fuel thermal conductivity are implemented, and their impact on calculated fission gas release is studied. The calculated fission gas release fraction in IFA-429/519.9 strongly depends on what correlation is used for the fuel thermal conductivity, since thermal release dominates over athermal release in this particular experiment. The conducted calculations show that athermal release processes account for less than 10% of the total gas release. However, athermal release from the fuel pellet rim zone is presumably underestimated by our models. This conclusion is corroborated by comparisons between measured and calculated Xe/Kr-ratios of the released fission gas.
Semi-empirical Study on Yield Mass Distribution for n+238U Fission
Institute of Scientific and Technical Information of China (English)
XU; Yong-mei; LIU; Li-le; SHU; Neng-chuan; CHEN; Yong-jing; LIU; Ting-jin; SUN; Zheng-jun
2015-01-01
A semi-empirical model method is developed for calculating the yield mass distributions and energy dependence for neutron-induced 238 fission.The system potential energy is consisting ofthe macro-energy and 2shell corrections,corresponding to the SL,SI and SII fission channels.The yield could be expressed with a five-Gaussianlike formula with 13 parameters,which were
Study of the fission process of deformed Na clusters in liquid-drop stabilized jellium model
Directory of Open Access Journals (Sweden)
M Payami
2008-07-01
Full Text Available In this work, using the liquid drop model in the context of the stabilized jellium model, we have studied the fission of charged Na clusters. In this study we have assumed a deformed non-spherical shape for the cluster. The ground state energies, critical sizes, fission barrier height, and the evaporation energies have been calculated. The results show a better agreement to the experimental results compared to our earlier work.
Langevin description of fission fragment charge distribution from excited nuclei
Karpov, A V
2002-01-01
A stochastic approach to fission dynamics based on a set of three-dimensional Langevin equations was applied to calculate fission-fragment charge distribution of compound nucleus sup 2 sup 3 sup 6 U. The following collective coordinates have been chosen - elongation coordinate, neck-thickness coordinate, and charge-asymmetry coordinate. The friction coefficient of charge mode has been calculated in the framework of one-body and two-body dissipation mechanisms. Analysis of the results has shown that Langevin approach is appropriate for investigation of isobaric distribution. Moreover, the dependences of the variance of the charge distribution on excitation energy and on the two-body viscosity coefficient has been studied
DSP Algorithms for Fission Fragment and Prompt Fission Neutron Spectroscopy
Zeynalova, O.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.; Fabry, I.
2009-10-01
Digital signal processing (DSP) algorithms are in high demand for modern nuclear fission investigation due to importance of increase the accuracy of fissile nuclear data for new generation of nuclear power stations. DSP algorithms for fission fragment (FF) and prompt fission neutron (PFN) spectroscopy are described in the present work. The twin Frisch-grid ionization chamber (GTIC) is used to measure the kinetic energy-, mass- and angular distributions of the FF in the 252Cf(SF) reaction. Along with the neutron time-of-flight (TOF) measurement the correlation between neutron emission and FF mass and energy is investigated. The TOF is measured between common cathode of the GTIC and the neutron detector (ND) pulses. Waveform digitizers (WFD) having 12 bit amplitude resolution and 100 MHz sampling frequency are used for the detector pulse sampling. DSP algorithms are developed as recursive procedures to perform the signal processing, similar to those available in various nuclear electronics modules, such as constant fraction discriminator (CFD), pulse shape discriminator (PSD), peak-sensitive analogue-to-digital converter (pADC) and pulse shaping amplifier (PSA). To measure the angle between FF and the cathode plane normal to the GTIC a new algorithm is developed having advantage over the traditional analogue pulse processing schemes. Algorithms are tested by comparing the numerical simulation of the data analysis of the 252Cf(SF) reaction with data available from literature.
Prompt Neutron Emission in 252CF Spontaneous Fission
Hambsch, F.-J.; Oberstedt, S.; Zeynalov, Sh.
2011-10-01
The prompt neutron emission in spontaneous fission of 252Cf has been investigated applying digital signal electronics. The goal was to compare the results from digital data acquisition and digital signal processing analysis with results of the pioneering work of Budtz-Jørgensen and Knitter. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 107 fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. The results are in very good agreement with literature. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.
Energy Technology Data Exchange (ETDEWEB)
Bonneau, L
2003-11-01
A lot of experimental data on nuclear fission has been being collected for the last 65 years, allowing theoreticians to confront their models with reality. The first part of this work is dedicated to the computation of fission barriers. We have extended the HF + BCS (Hartree Fock + Bandeen-Cooper-Schrieffer) method in order to include a new set of polynomials on which wave functions can be broken to, more accurately than on Hermite's polynomials in the 2 fragment configuration. The fission barriers of 26 heavy nuclei from Thorium-230 to Nobelium-256 have been assessed and compared to experimental data, it appears that differences are no greater than 1 MeV. We have discovered a neat correlation between the variation of the experimental fission lifetimes of even Fermium isotopes and the computed heights of second barriers. Moreover our model reproduces the hyper-deformed well of Thorium-230 with a good agreement on the well depth. The second part deals with the scission region. We have performed Hartree-Fock calculations in order to explore different ways of fragmentation. We have shown that the harmonic oscillator gives a valid description of such ways. In order to compute the mean value of J{sup 2} in the fragments we have been driven to propose an adequate definition of that quantity consistent with the non-locality property of the J{sup 2} operator. (A.C.)
Energy Technology Data Exchange (ETDEWEB)
Holdren, J.P.; Berwald, D.H.; Budnitz, R.J.; Crocker, J.G.; Delene, J.G.; Endicott, R.D.; Kazimi, M.S.; Krakowski, R.A.; Logan, B.G.; Schultz, K.R.
1987-09-10
The Senior Committee on Environmental, Safety, and Economic Aspects of Magnetic Fusion Energy (ESECOM) has assessed magnetic fusion energy's prospects for providing energy with economic, environmental, and safety characteristics that would be attractive compared with other energy sources (mainly fission) available in the year 2015 and beyond. ESECOM gives particular attention to the interaction of environmental, safety, and economic characteristics of a variety of magnetic fusion reactors, and compares them with a variety of fission cases. Eight fusion cases, two fusion-fission hybrid cases, and four fission cases are examined, using consistent economic and safety models. These models permit exploration of the environmental, safety, and economic potential of fusion concepts using a wide range of possible materials choices, power densities, power conversion schemes, and fuel cycles. The ESECOM analysis indicates that magnetic fusion energy systems have the potential to achieve costs-of-electricity comparable to those of present and future fission systems, coupled with significant safety and environmental advantages. 75 refs., 2 figs., 24 tabs.
Dating thermal events at Cerro Prieto using fission track annealing
Energy Technology Data Exchange (ETDEWEB)
Sanford, S.J.; Elders, W..
1981-01-01
Data from laboratory experiments and geologic fading studies were compiled from published sources to produce lines of iso-annealing for apatite in time-temperature space. Fission track ages were calculated for samples from two wells at Cerro Prieto, one with an apparently simple and one with an apparently complex thermal history. Temperatures were estimated by empirical vitrinite reflectance geothermometry, fluid inclusion homogenization and oxygen isotope equilibrium. These estimates were compared with logs of measured borehole temperatures.
Fission Fragment Angular Distributions measured with a Time Projection Chamber
Energy Technology Data Exchange (ETDEWEB)
Kleinrath, Verena [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-04-28
The subject is presented in a series of slides with the following organization: Introduction (What is anisotropy? Relevance (Theory and ratio cross section), Previous measurements); Experiment (Particle tracking in the fissionTPC, Neutron time of flight, Data analysis & uncertainty calculation, Preliminary result for ^{235}U); and Future Work (Refine ^{235}U result, Process ^{239}Pu data).
The dependence of cumulative 238U(n,f) fission yield on incident-neutron energy
Institute of Scientific and Technical Information of China (English)
ZHENG Na; ZHONG Chunlai; MA Liyong; CHEN Zhongjing; LI Xiangqing; LIU Tingjin; CHEN Jinxiang; FAN Tieshuan
2009-01-01
This work is aim at studying the dependence of fission yields on incident neutron energy,so as to produce evaluated yield sets of the energy dependence.Experimental data at different neutron energies for gas fission products 85m,87,88Kr and 138Xe resulting from the 238U(n,f) reaction are processed using codes AVERAGE for weighed average and ZOTT for simultaneous evaluation.Energy dependence of the cumulative fission product yields on the incident neutron is presented.The evaluated curve of product yield is compared with the results calculated by the TALYS-0.64 code.The present evaluation is consistent with other main libraries in error permission.The fit curve of 87,88Kr can be recommended to predict the unmeasured fission yields.Comparisons of the evaluated energy dependence curves with theoretical calculated results show that the predictions using purely theoretical model for the fission process are not sufficiently accurate and reliable for the calculations of the cumulative fission yields for the 238U(n,f).
Fusion solution to dispose of spent nuclear fuel, transuranic elements, and highly enriched uranium
Energy Technology Data Exchange (ETDEWEB)
Gohar, Yousry E-mail: gohar@anl.gov
2001-11-01
The disposal of the nuclear spent fuel, the transuranic elements, and the highly enriched uranium represents a major problem under investigation by the international scientific community to identify the most promising solutions. The investigation of this paper focused on achieving the top rated solution for the problem, the elimination goal, which requires complete elimination for the transuranic elements or the highly enriched uranium, and the long-lived fission products. To achieve this goal, fusion blankets with liquid carrier, molten salts or liquid metal eutectics, for the transuranic elements and the uranium isotopes are utilized. The generated energy from the fusion blankets is used to provide revenue for the system. The long-lived fission products are fabricated into fission product targets for transmutation utilizing the neutron leakage from the fusion blankets. This paper investigated the fusion blanket designs for small fusion devices and the system requirements for such application. The results show that 334 MW of fusion power from D-T plasma for 30 years with an availability factor of 0.75 can dispose of the 70,000 tons of the U.S. inventory of spent nuclear fuel generated up to the year 2015. In addition, this fusion solution eliminates the need for a geological repository site, which is a major advantage. Meanwhile, such utilization of the fusion power will provide an excellent opportunity to develop fusion energy for the future.
Adjoint affine fusion and tadpoles
Urichuk, Andrew; Walton, Mark A.
2016-06-01
We study affine fusion with the adjoint representation. For simple Lie algebras, elementary and universal formulas determine the decomposition of a tensor product of an integrable highest-weight representation with the adjoint representation. Using the (refined) affine depth rule, we prove that equally striking results apply to adjoint affine fusion. For diagonal fusion, a coefficient equals the number of nonzero Dynkin labels of the relevant affine highest weight, minus 1. A nice lattice-polytope interpretation follows and allows the straightforward calculation of the genus-1 1-point adjoint Verlinde dimension, the adjoint affine fusion tadpole. Explicit formulas, (piecewise) polynomial in the level, are written for the adjoint tadpoles of all classical Lie algebras. We show that off-diagonal adjoint affine fusion is obtained from the corresponding tensor product by simply dropping non-dominant representations.
Adjoint affine fusion and tadpoles
Urichuk, Andrew
2016-01-01
We study affine fusion with the adjoint representation. For simple Lie algebras, elementary and universal formulas determine the decomposition of a tensor product of an integrable highest-weight representation with the adjoint representation. Using the (refined) affine depth rule, we prove that equally striking results apply to adjoint affine fusion. For diagonal fusion, a coefficient equals the number of nonzero Dynkin labels of the relevant affine highest weight, minus 1. A nice lattice-polytope interpretation follows, and allows the straightforward calculation of the genus-1 1-point adjoint Verlinde dimension, the adjoint affine fusion tadpole. Explicit formulas, (piecewise) polynomial in the level, are written for the adjoint tadpoles of all classical Lie algebras. We show that off-diagonal adjoint affine fusion is obtained from the corresponding tensor product by simply dropping non-dominant representations.
Fission properties for r-process nuclei
Erler, J; Loens, H P; Martínez-Pinedo, G; Reinhard, P -G
2011-01-01
We present a systematics of fission barriers and fission lifetimes for the whole landscape of super-heavy elements (SHE), i.e. nuclei with Z>100. The fission lifetimes are also compared with the alpha-decay half-lives. The survey is based on a self-consistent description in terms of the Skyrme-Hartree-Fock (SHF) approach. Results for various different SHF parameterizations are compared to explore the robustness of the predictions. The fission path is computed by quadrupole constrained SHF. The computation of fission lifetimes takes care of the crucial ingredients of the large-amplitude collective dynamics along the fission path, as self-consistent collective mass and proper quantum corrections. We discuss the different topologies of fission landscapes which occur in the realm of SHE (symmetric versus asymmetric fission, regions of triaxial fission, bi-modal fission, and the impact of asymmetric ground states). The explored region is extended deep into the regime of very neutron-rich isotopes as they are expec...
Dynamical dipole mode in heavy-ion fusion reactions
Energy Technology Data Exchange (ETDEWEB)
Parascandolo, C., E-mail: concetta.parascandolo@na.infn.i [Universita degli Studi di Napoli ' Federico II' and INFN, Sezione di Napoli, via Cintia, I-80126 Napoli (Italy); Pierroutsakou, D. [INFN - Sezione di Napoli, via Cintia, I-80126 Napoli (Italy); Martin, B. [Universita degli Studi di Napoli ' Federico II' and INFN, Sezione di Napoli, via Cintia, I-80126 Napoli (Italy); Agodi, C.; Alba, R. [INFN - LNS, via Santa Sofia 62, I-95125 Catania (Italy); Boiano, A. [INFN - Sezione di Napoli, via Cintia, I-80126 Napoli (Italy); Coniglione, R. [INFN - LNS, via Santa Sofia 62, I-95125 Catania (Italy); De Filippo, E. [INFN - Sezione di Catania, 95123, Catania (Italy); Del Zoppo, A. [INFN - LNS, via Santa Sofia 62, I-95125 Catania (Italy); Emanuele, U. [INFN, Gruppo Collegato di Messina and Dip. di Fisica, Universita di Messina, Messina (Italy); Farinon, F. [GSI, Planckstrasse 1, D-64291, Darmstadt (Germany); Guglielmetti, A. [Universita degli Studi di Milano and INFN, Sezione di Milano, via Celoria 16, I-20133 Milano (Italy); Inglima, G.; La Commara, M. [Universita degli Studi di Napoli ' Federico II' and INFN, Sezione di Napoli, via Cintia, I-80126 Napoli (Italy); Maiolino, C. [INFN - LNS, via Santa Sofia 62, I-95125 Catania (Italy); Mazzocchi, C. [Universita degli Studi di Milano and INFN, Sezione di Milano, via Celoria 16, I-20133 Milano (Italy); Mazzocco, M. [Dip. di Fisica and INFN, Universita di Padova, via F. Marzolo 8, I-35131 Padova (Italy); Romoli, M. [INFN - Sezione di Napoli, via Cintia, I-80126 Napoli (Italy); Sandoli, M. [Universita degli Studi di Napoli ' Federico II' and INFN, Sezione di Napoli, via Cintia, I-80126 Napoli (Italy); Santonocito, D. [INFN - LNS, via Santa Sofia 62, I-95125 Catania (Italy)
2010-03-01
The dynamical dipole mode, excited in charge asymmetric heavy-ion collisions, was investigated in the mass region of the {sup 192}Pb compound nucleus, formed by using the {sup 40,48}Ca + {sup 152,144}Sm reactions at approx11 MeV/nucleon. Preliminary results of this measurement, concerning both fusion-evaporation and fission events are presented. As a fast cooling mechanism on the fusion path, the dynamical dipole mode could be useful for the synthesis of super heavy elements through 'hot' fusion reactions.
The VERDI fission fragment spectrometer
Directory of Open Access Journals (Sweden)
Frégeau M.O.
2013-12-01
Full Text Available The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This configuration, where the stop detector will provide us simultaneously with the kinetic energy of the fragment and timing information, significantly limits energy straggling in comparison to legacy experimental setup where a thin foil was usually used as a stop detector. In order to improve timing resolution, neutron transmutation doped silicon will be used. The high resistivity homogeneity of this material should significantly improve resolution in comparison to standard silicon detectors. Post-neutron fission fragment masses are obtained form the time-of-flight and the energy signal in the silicon detector. As an intermediary step a diamond detector will also be used as start detector located very close to the target. Previous tests have shown that poly-crystalline chemical vapour deposition (pCVD diamonds provides a coincidence time resolution of 150 ps not allowing complete separation between very low-energy fission fragments, alpha particles and noise. New results from using artificial single-crystal diamonds (sCVD show similar time resolution as from pCVD diamonds but also sufficiently good energy resolution.
Fukumitsu, Kansai; Hatsukano, Tetsu; Yoshimura, Azumi; Heuser, John; Fujishima, Kazuto; Kengaku, Mineko
2016-03-01
Mitochondria dynamically change their shape by repeated fission and fusion in response to physiological and pathological conditions. Recent studies have uncovered significant roles of mitochondrial fission and fusion in neuronal functions, such as neurotransmission and spine formation. However, the contribution of mitochondrial fission to the development of dendrites remains controversial. We analyzed the function of the mitochondrial fission GTPase Drp1 in dendritic arborization in cerebellar Purkinje cells. Overexpression of a dominant-negative mutant of Drp1 in postmitotic Purkinje cells enlarged and clustered mitochondria, which failed to exit from the soma into the dendrites. The emerging dendrites lacking mitochondrial transport remained short and unstable in culture and in vivo. The dominant-negative Drp1 affected neither the basal respiratory function of mitochondria nor the survival of Purkinje cells. Enhanced ATP supply by creatine treatment, but not reduced ROS production by antioxidant treatment, restored the hypomorphic dendrites caused by inhibition of Drp1 function. Collectively, our results suggest that Drp1 is required for dendritic distribution of mitochondria and thereby regulates energy supply in growing dendritic branches in developing Purkinje cells.
Fusion yield measurements on JET and their calibration
Energy Technology Data Exchange (ETDEWEB)
Syme, D.B., E-mail: brian.syme@ccfe.ac.uk [EURATOM-CCFE Fusion Association, Culham Science Centre, Abingdon, OXON OX14 3DB (United Kingdom); Popovichev, S. [EURATOM-CCFE Fusion Association, Culham Science Centre, Abingdon, OXON OX14 3DB (United Kingdom); Conroy, S. [EURATOM-VR Association, Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Lengar, I.; Snoj, L. [EURATOM-MHEST Association, Reactor Physics Division, Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); Sowden, C. [EURATOM-CCFE Fusion Association, Culham Science Centre, Abingdon, OXON OX14 3DB (United Kingdom); Giacomelli, L. [EURATOM-ENEA-CNR Association, CNR-IFP and Univ. di Milano-Bicocca, Milan (Italy); Hermon, G.; Allan, P.; Macheta, P.; Plummer, D.; Stephens, J. [EURATOM-CCFE Fusion Association, Culham Science Centre, Abingdon, OXON OX14 3DB (United Kingdom); Batistoni, P. [EURATOM-ENEA Association, Via E. Fermi,40, 00044 Frascati (Italy); Prokopowicz, R.; Jednorog, S. [EURATOM-IPPLM Association, Institute of Plasma Physics and Laser Microfusion, Hery 23, 01-497 Warsaw (Poland); Abhangi, M.R.; Makwana, R. [Institute for Plasma Research, Bhat, Gandhinagar, 382 428 Gujarat (India)
2014-11-15
The power output of fusion experiments and fusion reactor-like devices is measured in terms of the neutron yields which relate directly to the fusion yield. In this paper we describe the devices and methods used to make the new in situ calibration of JET in April 2013 and its early results. The target accuracy of this calibration was 10%, just as in the earlier JET calibration and as required for ITER, where a precise neutron yield measurement is important, e.g., for tritium accountancy. We discuss the constraints and early decisions which defined the main calibration approach, e.g., the choice of source type and the deployment method. We describe the physics, source issues, safety and engineering aspects required to calibrate directly the Fission Chambers and the Activation System which carry the JET neutron calibration. In particular a direct calibration of the Activation system was planned for the first time in JET. We used the existing JET remote-handling system to deploy the {sup 252}Cf source and developed the compatible tooling and systems necessary to ensure safe and efficient deployment in these cases. The scientific programme has sought to better understand the limitations of the calibration, to optimise the measurements and other provisions, to provide corrections for perturbing factors (e.g., presence of the remote-handling boom and other non-standard torus conditions) and to ensure personnel safety and safe working conditions. Much of this work has been based on an extensive programme of Monte-Carlo calculations which, e.g., revealed a potential contribution to the neutron yield via a direct line of sight through the ports which presents individually depending on the details of the port geometry.
Chopra, Sahila; Hemdeep, Kaur, Arshdeep; Gupta, Raj K.
2016-02-01
Background: In our earlier study of the 12C+93Nb→*105Ag reaction at three near- and below-barrier energies (Ec .m .=41.097 , 47.828, and 54.205 MeV), using the dynamical cluster-decay model (DCM) with various nuclear interaction potentials (the Blocki et al. pocket formula and others derived from the Skyrme energy density formalism) for compact, coplanar (Φc=00 ) nuclei, we found a large non-compound-nucleus (nCN) contribution in the measured fusion cross section of this reaction. Purpose: In the present work, we look for the effect of using non-coplanar, compact configurations (Φc≠00 ), in the Blocki et al. pocket formula of the nuclear proximity potential, on the non-compound-nucleus (nCN) contribution, using the DCM. Methods: Allowing the Φ degree of freedom in the DCM formalism, we calculate the compound-nucleus (CN) and nCN cross sections. The only parameter of the DCM is the neck-length parameter Δ R , which also fits the empirically determined nCN cross section nearly exactly, under the assumption of considering it like a quasifission process where the fragment preformation factor P0=1 . Results: With the Φ degree of freedom included, at the higher two energies the nCN cross section gets enhanced, and hence the pure CN cross section is decreased, since the calculated (total) fusion cross section is fitted to experimental data. The parameter Δ R for the nCN contribution is smaller, and hence the reaction time larger, than for the CN decay process. Also, the contributing angular momentum ℓmax value increases in going from Φc=00 to Φc≠00 for both the CN and nCN processes. The intermediate mass fragments (IMFs), measured up to mass 13 in this reaction, are shown extended up to mass 16, and the fusion-fission (f f ) region is identified as A /2 ±16 , the same as for the Φc=00 case. Conclusions: As a result of enhanced nCN cross section due to Φc≠00 , the CN fusion probability PCN for *105Ag changes its behavior from an increasing to a
Energy, material and land requirement of a fusion plant
DEFF Research Database (Denmark)
Schleisner, Liselotte; Hamacher, T.; Cabal, H.
2001-01-01
The energy and material necessary to construct a power plant and the land covered by the plant are indicators for the ‘consumption’ of environment by a certain technology. Based on current knowledge, estimations show that the material necessary to construct a fusion plant will exceed the material...... requirement of a fission plant by a factor of two. The material requirement for a fusion plant is roughly 2000 t/MW and little less than 1000 t/MW for a fission plant. The land requirement for a fusion plant is roughly 300 m2/MW and the land requirement for a fission plant is a little less than 200 m2/MW....... The energy pay back time, defined later in Section 6, is little more than half a year for a fusion plant with capacity 1 GWe. Only the electrical energy is accounted for as released energy not the thermal energy. In all these indicators, fusion compares well with conventional technologies while it consumes...
Huppertz, Berthold; Gauster, Martin
2011-01-01
The villous trophoblast of the human placenta is the epithelial cover of the fetal chorionic villi floating in maternal blood. This epithelial cover is organized in two distinct layers, the multinucleated syncytiotrophoblast directly facing maternal blood and a second layer of mononucleated cytotrophoblasts. During pregnancy single cytotrophoblasts continuously fuse with the overlying syncytiotrophoblast to preserve this end-differentiated layer until delivery. Syncytial fusion continuously supplies the syncytiotrophoblast with compounds of fusing cytotrophoblasts such as proteins, nucleic acids and lipids as well as organelles. At the same time the input of cytotrophoblastic components is counterbalanced by a continuous release of apoptotic material from the syncytiotrophoblast into maternal blood. Fusion is an essential step in maintaining the syncytiotrophoblast. Trophoblast fusion was shown to be dependant on and regulated by multiple factors such as fusion proteins, proteases and cytoskeletal proteins as well as cytokines, hormones and transcription factors. In this chapter we focus on factors that may be involved in the fusion process of trophoblast directly or that may prepare the cytotrophoblast to fuse.
Energy Technology Data Exchange (ETDEWEB)
Rodriguez-Guzman, R. [Kuwait University, Physics Department, Kuwait (Kuwait); Robledo, L.M. [Universidad Autonoma de Madrid, Departamento de Fisica Teorica, Madrid (Spain)
2016-01-15
Mean-field calculations, based on the D1S, D1N and D1M parametrizations of the Gogny energy density functional, have been carried out to obtain the potential energy surfaces relevant to fission in several Ra isotopes with the neutron number 144 ≤ N ≤ 176. Inner and outer barrier heights as well as first and second isomer excitation energies are given. The existence of a well-developed third minimum along the fission paths of Ra nuclei is analyzed in terms of the energetics of the ''fragments'' defining such elongated configuration. The masses and charges of the fission fragments are studied as functions of the neutron number in the parent Ra isotope. The comparison between fission and α-decay half-lives, reveals that the former becomes faster for increasing neutron numbers. Though there exists a strong variance of the results with respect to the parameters used in the computation of the spontaneous fission rate, a change in tendency is observed at N = 164 with a steady increase that makes heavier neutron-rich Ra isotopes stable against fission, diminishing the importance of fission recycling in the r-process. (orig.)
Technical Application of Nuclear Fission
Denschlag, J. O.
The chapter is devoted to the practical application of the fission process, mainly in nuclear reactors. After a historical discussion covering the natural reactors at Oklo and the first attempts to build artificial reactors, the fundamental principles of chain reactions are discussed. In this context chain reactions with fast and thermal neutrons are covered as well as the process of neutron moderation. Criticality concepts (fission factor η, criticality factor k) are discussed as well as reactor kinetics and the role of delayed neutrons. Examples of specific nuclear reactor types are presented briefly: research reactors (TRIGA and ILL High Flux Reactor), and some reactor types used to drive nuclear power stations (pressurized water reactor [PWR], boiling water reactor [BWR], Reaktor Bolshoi Moshchnosti Kanalny [RBMK], fast breeder reactor [FBR]). The new concept of the accelerator-driven systems (ADS) is presented. The principle of fission weapons is outlined. Finally, the nuclear fuel cycle is briefly covered from mining, chemical isolation of the fuel and preparation of the fuel elements to reprocessing the spent fuel and conditioning for deposit in a final repository.
Measurement of reaction cross sections of fission products induced by DT neutrons
Energy Technology Data Exchange (ETDEWEB)
Nakano, Daisuke; Murata, Isao; Takahashi, Akito [Osaka Univ., Suita (Japan)
1998-03-01
With the view of future application of fusion reactor to incineration of fission products, we have measured the {sup 129}I(n,2n){sup 128}I reaction cross section by DT neutrons with the activation method. The measured cross section was compared with the evaluated nuclear data of JENDL-3.2. From the result, it was confirmed that the evaluation overestimated the cross section by about 20-40%. (author)
A novel fuzzy sensor fusion algorithm
Institute of Scientific and Technical Information of China (English)
FU Hua; YANG Yi-kui; MA Ke; LIU Yu-jia
2011-01-01
A novel fusion algorithm was given based on fuzzy similarity and fuzzy integral theory.First,it calculated the fuzzy similarity among a certain sensor's measurement values and the multiple sensors' objective prediction values to determine the importance weight of each sensor and realize multi-sensor data fusion.Then according to the determined importance weight,an intelligent fusion system based on fuzzy integral theory was given,which can solve FEI-DEO and DEI-DEO fusion problems and realize the decision fusion.Simulation results were proved that fuzzy integral algorithm has enhanced the capability of handling the uncertain information and improved the intelligence degrees.
Radiochemical studies on nuclear fission at Trombay
Indian Academy of Sciences (India)
Asok Goswami
2015-08-01
Since the discovery of nuclear fission in the year 1939, both physical and radiochemical techniques have been adopted for the study of various aspects of the phenomenon. Due to the ability to separate individual elements from a complex reaction mixture with a high degree of sensitivity and selectivity, a chemist plays a significant role in the measurements of mass, charge, kinetic energy, angular momentum and angular distribution of fission products in various fissioning systems. At Trombay, a small group of radiochemists initiated the work on radiochemical studies of mass distribution in the early sixties. Since then, radiochemical investigations on various fission observables have been carried out at Trombay in , , and heavy-ion-induced fissions. An attempt has been made to highlight the important findings of such studies in this paper, with an emphasis on medium energy and heavy-ion-induced fission.
Improved fission neutron energy discrimination with 4He detectors through pulse filtering
Zhu, Ting; Liang, Yinong; Rolison, Lucas; Barker, Cathleen; Lewis, Jason; Gokhale, Sasmit; Chandra, Rico; Kiff, Scott; Chung, Heejun; Ray, Heather; Baciak, James E.; Enqvist, Andreas; Jordan, Kelly A.
2017-03-01
This paper presents experimental and computational techniques implemented for 4He gas scintillation detectors for induced fission neutron detection. Fission neutrons are produced when natural uranium samples are actively interrogated by 2.45 MeV deuterium-deuterium fusion reaction neutrons. Fission neutrons of energies greater than 2.45 MeV can be distinguished by their different scintillation pulse height spectra since 4He detectors retain incident fast neutron energy information. To enable the preferential detection of fast neutrons up to 10 MeV and suppress low-energy event counts, the detector photomultiplier gain is lowered and trigger threshold is increased. Pile-up and other unreliable events due to the interrogating neutron flux and background radiation are filtered out prior to the evaluation of pulse height spectra. With these problem-specific calibrations and data processing, the 4He detector's accuracy at discriminating fission neutrons up to 10 MeV is improved and verified with 252Cf spontaneous fission neutrons. Given the 4He detector's ability to differentiate fast neutron sources, this proof-of-concept active-interrogation measurement demonstrates the potential of special nuclear materials detection using a 4He fast neutron detection system.
Zhao, Lantao; Li, Shuhong; Wang, Shilei; Yu, Ning; Liu, Jia
2015-06-01
The mitochondrial calcium uniporter (MCU) transports free Ca(2+) into the mitochondrial matrix, maintaining Ca(2+) homeostasis, thus regulates the mitochondrial morphology. Previous studies have indicated that there was closely crosstalk between MCU and mitochondrial fission during the process of ischemia/reperfusion injury. This study constructed a hypoxia reoxygenation model using primary hippocampus neurons to mimic the cerebral ischemia/reperfusion injury and aims to explore the exactly effect of MCU on the mitochondrial fission during the process of ischemia/reperfusion injury and so as the mechanisms. Our results found that the inhibitor of the MCU, Ru360, decreased mitochondrial Ca(2+) concentration, suppressed the expression of mitochondrial fission protein Drp1, MIEF1 and Fis1, and thus improved mitochondrial morphology significantly. Whereas spermine, the agonist of the MCU, had no significant impact compared to the I/R group. This study demonstrated that the MCU regulates the process of mitochondrial fission by controlling the Ca(2+) transport, directly upregulating mitochondrial fission proteins Drp1, Fis1 and indirectly reversing the MIEF1-induced mitochondrial fusion. It also provides new targets for brain protection during ischemia/reperfusion injury.
DEFF Research Database (Denmark)
Sørensen, Jakob Balslev; Milosevic, Ira
2015-01-01
the vesicular SNARE VAMP2/synaptobrevin-2 and the target (plasma membrane) SNAREs SNAP25 and syntaxin-1 results in fusion and release of neurotransmitter, synchronized to the electrical activity of the cell by calcium influx and binding to synaptotagmin. Formation of the SNARE complex is tightly regulated...... and appears to start with syntaxin-1 bound to an SM (Sec1/Munc18-like) protein. Proteins of the Munc13-family are responsible for opening up syntaxin and allowing sequential binding of SNAP-25 and VAMP2/synaptobrevin-2. N- to C-terminal “zippering” of the SNARE domains leads to membrane fusion...
Fission dynamics of the compound nucleus 213Fr formed in heavy-ion-induced reactions
Indian Academy of Sciences (India)
Hadi Eslamizadeh
2013-04-01
A stochastic approach based on one-dimensional Langevin equations was used to calculate the average pre-fission multiplicities of neutrons, light charged particles and the fission probabilities for the compound nucleus 213Fr and the results are compared with the experimental data. In these calculations, a modified wall and window dissipation with a reduction coefficient, $k_{s}$ , has been used in the Langevin equations. It was shown that the results of the calculations are in good agreement with the experimental data by using values of $k_{s}$ in the range $0.3 ≤ k_{s} ≤ 0.5.$
Institute of Scientific and Technical Information of China (English)
Zafar Yasin; Warda Iram; Muhammad Asghar; M. Ikram Shahzad
2011-01-01
Fission cross sections strongly depend on the ratio of the level density parameter in fission to neutron emission,af/an.In this work,a cascade-exciton model implemented in the code CEM95 has been used to observe this effect for proton induced fission cross sections of tungsten,lead and bismuth.The method was employed using different level density parameter ratios for each fission cross section calculation.The calculated fission cross sections are compared with the available experimental data in the literature.It has been observed that a change of the ratio of the level density parameter,af/an,is necessary with the incident energy of the proton,to best estimate the fission cross sections in CEM95.