Rare earth silicate (Ce, La, Nd, Ca, Th) SiO4 and cheralite (Th, Ca, Ce, La) (Psi)O4 are the responsible minerals for the anomalies of Morro de Ferro

International Nuclear Information System (INIS)

Fujimori, K.

1982-01-01

The Rare Earth silicate (La, Ce, Nd, Ca, Th)SiO 4 and cheralite (identified by Prof. Freeborn on a sample prepared from drilling core) were recognized as the most probable radioactive minerals that gave origin to high radioactive anomaly at Morro do Ferro hill together with coffinite, thorite, pyrochlore, apatite, etc., that are found in small quantity. The acids produced by decomposition of pyrite and fluorite have etched these radioactive minerals giving the high radioactive anomaly caracterized by high grade desiquilibrium of 232 Th serie. (Author) [pt

Cheralite quartzides in Itiuba mountains-Bahia, Brazil

International Nuclear Information System (INIS)

Gorsky, E.; Gorsky, V.A.

1974-01-01

Quartzitic pebbles of anomalous radioactivity were found by the geologists of the 'Comissao Nacional de Energia Nuclear' of Brazil (CNEN) in November 1964 in the Vicinity of Santa Rosa, municipality of Jaguarari, Bahia. A radioactive anomaly of large extension was subsequently localized by scintilometric prospecting in February 1965 over precambrian quartzites on Morro do Barbosa (near Santa Rosa). Samples of the radioactive rocks were investigated by the Mineralogical-Petrographical Section of the CNEN. The results of the investigation are reported

Low-degree partial melting of metapelites - another possible implement for selective concentration of uranium: Example from the Rozna uranium deposit, Bohemian Massif

International Nuclear Information System (INIS)

Leichmann, J.; Matula, M.; Broska, I.; Holeczy, D.

2002-01-01

Monazite, as the main carrier of U and Th in host biotite gneiss at the Rozna uranium deposit, was replaced by allanite during the process of partial melting. The transformation was accompanied by a release of U, and to a lesser extent of Th, from the monazite lattice. The liberated U and Th crystallized in the extracted granitic melt mainly in the form of thorogummite or cheralite. The granites are depleted in HFS and LREE. Garnet-poor granites are depleted in HREE as well, whereas garnet-rich types are enriched in HREE. (author)

Crystal chemistry of M{sup II}M′{sup IV}(PO{sub 4}){sub 2} double monophosphates

Energy Technology Data Exchange (ETDEWEB)

Bregiroux, Damien, E-mail: damien.bregiroux@upmc.fr [Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris, 11 place Marcelin Berthelot, 75005 Paris (France); Popa, Karin [“Al.I. Cuza” University, Department of Chemistry, 11-Carol I Blvd., 700506 Iasi (Romania); Wallez, Gilles [Institut de Recherche de Chimie Paris (IRCP), CNRS – Chimie ParisTech – Paris Sciences et Lettres PSL UMR8247, 11 rue Pierre et Marie Curie, 75005 Paris (France); Sorbonne Universités, UPMC Univ Paris 06 (France)

2015-10-15

M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds have been extensively studied for several decades for their potential applications in the field of several domains such as matrices for actinides conditioning, phosphors etc. In this paper, the relationships between composition and crystal structure of these compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. M{sup II}M′{sup IV}(PO{sub 4}){sub 2} structures stem from two different archetypes: the cheralite and the yavapaiite structures, with some exceptions that are also described in this article. The ratio of the cations radii appears to be the most relevant parameter. The high ratio between the ionic radii of the divalent and tetravalent cations in yavapaiite derivates results in the ordering of these cations into well-differentiated polyhedra whereas cheralite is the only non-ordered structure encountered for M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds. - Graphical abstract: In this paper, the relationships between composition and crystal structure of M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. - Highlights: • Crystal structure–composition relationships of MIIM′IV(PO4)2 compounds. • Review of the various processes used for the synthesis of these compounds. • Their most reported properties are described and discussed.

Monazite as a suitable actinide waste form

Energy Technology Data Exchange (ETDEWEB)

Schlenz, Hartmut; Heuser, Julia; Schmitz, Stephan; Bosbach, Dirk [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Energie und Klimaforschung (IEK), Nukleare Entsorgung und Reaktorsicherheit (IEK-6); Neumann, Andreas [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Energie und Klimaforschung (IEK), Nukleare Entsorgung und Reaktorsicherheit (IEK-6); RWTH Aachen Univ. (Germany). Inst. for Crystallography

2013-03-01

The conditioning of radioactive waste from nuclear power plants and in some countries even of weapons plutonium is an important issue for science and society. Therefore the research on appropriate matrices for the immobilization of fission products and actinides is of great interest. Beyond the widely used borosilicate glasses, ceramics are promising materials for the conditioning of actinides like U, Np, Pu, Am, and Cm. Monazite-type ceramics with general composition LnPO{sub 4} (Ln = La to Gd) and solid solutions of monazite with cheralite or huttonite represent important materials in this field. Monazite appears to be a promising candidate material, especially because of its outstanding properties regarding radiation resistance and chemical durability. This article summarizes the most recent results concerning the characterization of monazite and respective solid solutions and the study of their chemical, thermal, physical and structural properties. The aim is to demonstrate the suitability of monazite as a secure and reliable waste form for actinides. (orig.)

Mobility of thorium from the Morro do Ferro

International Nuclear Information System (INIS)

Eisenbud, M.; Lei, W.; Ballad, R.; Franca, E.P.; Cullen, T.L.

1981-08-01

An estimated 20,000 metric ton (MT) deposit of Th is located near the summit of the Morro do Ferro, a hill near the center of the Pocos de Caldas plateau in the State of Minas Gerais, Brazil. Most of the Th is contained in microscopic crystals of cheralite, monazite and zircon in a matrix of highly weathered alkalic igneous rock interlaced by a stockwork of magnetite dikes. Because of similarities in the chemistries of Th and Pu under many environmental conditions, a study of the rate of mobilization of Th from this deposit is being undertaken to improve our understanding of how rapidly Pu would be mobilized from a nuclear waste repository that has been breached. The deposit also contains appreciable quantities of U and rare earth elements, and their mobilization rates are being investigated, but only the Th data are presented here. Mobilization is being studied: a) by measuring the rate of Th transport by a stream that drains the hill, and b) by analysis of dated cores from sedimentary deposits in the drainage basin. The mean total Th concentration (dissolved plus suspended particulates)in samples of stream water collected during the past year was 0.39 μg/l. The standard error of the mean was 0.07 μg/l. To a first approximation, the estimated annual mobilization rate of the Th deposit has been calculated to be 4 x 10 - 8 per year. If this rate of mobilization persists, the life of the Th deposit would thus be about 25 million years. (Author) [pt

Mobility of thorium from the Morro do Ferro

International Nuclear Information System (INIS)

Eisenbud, M.; Lei, W.; Ballad, R.; Penna Franca, E.; Cullen, T.L.; Freeborn, P.

1982-01-01

An estimated 20,000 metric ton deposit of Th is located near the summit of the Morro do Ferro, a hill near the centre of the Pocos de Caldas plateau in the State of Minas Gerais, Brazil. Most of the Th is contained in microscopic crystals of cheralite, monazite and zircon in a matrix of highly weathered alkalic igneous rock interlaced by a stockwork of magnetite dikes. Because of similarities in the chemistries of Th and Pu under many environmental conditions, a study of the rate of mobilization of Th from this deposit is being undertaken to improve our understanding of how rapidly Pu would be mobilized from a nuclear waste repository that has been breached. The deposit also contains appreciable quantities of U and rare earth elements, and their mobilization rates are being investigated, but only the Th data are presented here. Mobilization is being studied (a) by measuring the rate of Th transport by a stream that drains the hill, and (b) by analysis of dated cores from sedimentary deposits in the drainage basin. The mean total Th concentration (dissolved plus suspended particulates) in samples of stream water collected during the past year was 0.39 μg/ltr. The standard error of the mean was 0.07 μg/ltr. To a first approximation, the estimated annual mobilization rate of the Th deposit has been calculated to be 4 x 10 -8 per year. If this rate of mobilization persists, the life of the Th deposit would thus be about 25 million years. (author)