Sample records for th-u-cycle izuchenie rezhima

  1. 232Th, 233Pa, and 234U capture cross-section measurements in moderated neutron flux (United States)

    Bringer, O.; Isnard, H.; AlMahamid, I.; Chartier, F.; Letourneau, A.


    The Th-U cycle was studied through the evolution of a 100 μg 232Th sample irradiated in a moderated neutron flux of 8.010 14 n/cm 2/s, intensity close to that of a thermal molten salt reactor. After 43 days of irradiation and 6 months of cooling, a precise mass spectrometric analysis, using both TIMS and MC-ICP-MS techniques, was performed, according to a rigorous methodology. The measured thorium and uranium isotopic ratios in the final irradiated sample were then compared with integral simulations based on evaluated data; an overall good agreement was seen. Four important thermal neutron-capture cross-sections were also extracted from the measurements, 232Th (7.34±0.21 b), 233Pa (38.34±1.78 b), 234U (106.12±3.34 b), and 235U (98.15±11.24 b). Our 232Th and 235U results confirmed existing values whereas the cross-sections of 233Pa and 234U (both key parameters) have been redefined.

  2. Measurement of the (236)U(n, f) Cross Section at n_TOF

    CERN Document Server

    Sarmento, R; Vaz, P; Colonna, N; Calviani, M


    A precise knowledge of the (236)U neutron-induced fission cross-section is required for the development of accelerator-driven systems and reactors based on the Th-U cycle. The evaluated data presently stored in the nuclear data libraries rely on outdated experimental measurements and show large discrepancies in the energy region between 1 keV and 100 keV. More recent measurements made at LANSCE and GELINA yielded results which are in disagreement with the literature for the resonance region and below 10 eV. In order to improve the present knowledge of the (236)U(n, f) cross-section, a new measurement was performed at the neutron Time-Of-Flight facility n\\_TOF at CERN. A Fast Ionization Chamber was used, in which four samples of (236)U and two of (235)U were mounted. The (236)U(n, f) cross-section was determined relative to the standard (235)U(n, f) reaction. The contribution from the (235)U contamination in the samples was subtracted, together with the alpha-particle background. Finally, the data were correct...

  3. Thorium oxide dissolution: kinetics and mechanism

    International Nuclear Information System (INIS)

    Simonnet, Marie


    Studies of new energy sources are necessary to meet the rising global demand. In the nuclear area, Th-U cycle has been reinvestigated to supplement or replace the currently used U-Pu cycle. This project though needs further improvement to be operated in an industrial plant, especially on the reprocessing process, which consists in fuel dissolution in nitric acid medium, followed by liquid-liquid extraction. Still, unlike uranium, thorium oxide does not dissolve in concentrated nitric acid. Small amounts of fluoride are required to achieve the dissolution. The dissolution is rather slow and HNO 3 -HF mixture is very corrosive. The aim of this project is thus to find an efficient dissolution method which both decreases corrosion and improves dissolution rate. The synthesized thorium oxide powder has been dissolved in chosen conditions. Effects of solid parameters, dissolution method and dissolution medium have been studied. Results show a strong dependence on oxide crystallinity. No improvement on dissolution rate was observed with power ultrasounds, except for the temperature increase, which greatly enhances dissolution rate. No other complexing agents than fluoride allows total dissolution. Rising HNO 3 and HF concentrations increases dissolution rate until the amount of fluorides is so high that a precipitate forms at the surface. This study led to the proposal of a dissolution mechanism whose limiting step is the formation of an activated complex. Based on kinetics and equilibrium equations, initial dissolution rate was then written as a function of the different studied parameters. Experimental results were finally fitted by this relation to find kinetics and thermodynamics constants, proving the accuracy of the proposed mechanism. (author)

  4. Neutron elastic scattering cross-sections measurement on carbon and fluorine in epithermal energy range using PEREN platform; Mesure des sections efficaces de diffusion elastique des neutrons sur le carbone et le fluor dans le domaine epithermique sur la plate-forme PEREN

    Energy Technology Data Exchange (ETDEWEB)

    Thiolliere, N


    Molten Salt Reactor (MSR) based on Th/U cycle is one of the new generation concepts for nuclear energy production. A typical MSR is a graphite-moderated core with liquid fuel ({sup 7}LiF +ThF{sub 4} + UF{sub 4}). Many numerical studies based on Monte-Carlo codes are currently carried out but the validity of these numerical result relies on the precise knowledge of neutron cross sections used such as elastic scattering on carbon ({sigma}{sub C}), fluorine ({sigma}{sub F}) and lithium 7 ({sigma}{sub Li}). The goal of this work is to obtain {sigma}{sub C} and {sigma}{sub F} between 1 eV and 100 keV. Such measurements have been performed at the Laboratoire de Physique Subatomique et de Cosmologie (LPSC) de Grenoble on the experimental platform PEREN using slowing-down time spectrometers (C and CF{sub 2}) associated to a pulsed neutron generator (GENEPI). Capture rates are obtained for reference materials (Au, Ag, Mo and In) using YAP scintillator coupled to a photo-multiplier. Very precise simulations (MCNP code) of the experimental setup have been performed and comparison with experiments has led to the determination of {sigma}{sub C} and {sigma}{sub F} with accuracies of 1% and 2% respectively. These results show a small discrepancy to evaluated nuclear data file (ENDF). Measures of total cross-sections {sigma}{sub C} and {sigma}{sub F} at higher energy (200 - 600 keV) were also carried out at Centre des Etudes Nucleaires de Bordeaux using a transmission method. Mono-energetic neutrons were produced by protons accelerated by a Van de Graaff accelerator on a LiF target and transmitted neutrons are counted in a proportional hydrogen gaseous detector. Discrepancies of 5% and 9% for {sigma}{sub C} and {sigma}{sub F} respectively with ENDF have been shown. (author)

  5. Nuclear reactors and technology in the next stage

    International Nuclear Information System (INIS)

    Orlov, V.


    Author deals with the perspectives of development of nuclear power. It is possible to create in a fairly short time reactors and fuel technology that would meet the main requirements for large-scale power production, i.e.: (a) to afford a 100-fold reduction in the specific consumption of uranium, by utilizing thousands of tonnes of Pu accumulated in the spent fuel from the reactors of the fl t stage; .to rule out nuclear disasters, by taking advantage of the intrinsic properties and behavior of reactor, coolant, fuel, etc., with the plants made simpler and cheaper; (b) to hit a balance between the radiotoxicity of waste and that of feed uranium, by providing neutron transmutation; (c) to create power reactors and fuel cycle technology that would not afford extraction of weapon-grade materials. To fulfil all these requirements, it is necessary to provide substantial neutron excess in a chain reaction for Pu breeding, to use fuel with an equilibrium composition, to bum actinides and LLFPs. All this can be done only in fast reactors. Fast reactors can also provide fuel for thermal reactors that might still be used for some applications, operating in a Th/U cycle, which is the best option for such facilities. Novel engineering solutions will be necessary: high-density heat-conductive fuel (UPuN), chemically inert high-boiling coolant (Pb), dry reprocessing. These issues have been studied well enough to allow embarking on the development of advanced fast reactors. Minatom institutions are finalizing a detailed design of a demonstration BREST-300 plant, complete with an on-site fuel cycle that will meet the requirements of large-scale nuclear power. Hopefully, construction of this plant at Beloyarsk site with its subsequent trial operation would open a door to the next stage in nuclear power development. (author)

  6. A road map for the realization of global-scale thorium breeding fuel cycle by single molten-fluoride flow

    International Nuclear Information System (INIS)

    Furukawa, K.; Arakawa, K.; Erbay, L. B.


    composed of a simple single-phase molten-fluoride, which is used for all purposes of THORIMS-NES including the transmutation of waste nuclei as a most suitable working medium. This Th-U fuel cycle has significant advantages in negligible production of Trans-uranium elements, nuclear proliferation resistance, economy, etc., and in a high potential for producing hydrogen-fuel by easier high-temperature heat production in future. For its realization we have to develop the following steps successively: (A) Mini FUJI (7-10 MWe): laying foundation for the basic MSR technology and specialists, reconfirming/improving the ORNL-MSR-Program results, the successful 4 years operation experience of MSRE (Molten-Salt Reactor Experiment); (B) FUJI-Pu (100-300 MWe) : incinerating initial plutonium containing MS-fuel prepared easily by dry processing (simplified FREGATE project without solid-fuel reproduction) from spent solid fuels of existing nuclear power stations, and producing U 2 33. It means smooth/gradual shifting from present U-Pu cycle era; (C) AMSB: producing U 2 33 depending on the matured MSR technology 20-30 years later. (D) THORIMS-NES: globally deploying the regional centers. Now the real Th-U Breeding Fuel-cycle would be implemented for global survival in the issues of not only energy, environment and poverty but also the perfect elimination of the wars through the extinction of nuclear weapons by nuclear burnup of nuclear weapon materials, for which purpose the Th-U cycle has a significant advantage over the U-Pu cycle. In this study all items mentioned are explained, evaluated and discussed thoroughly for the sake of global survival