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Purification by high vacuum fusion and progressive solidification of uranium from electrolytic origin; Purification par fusion sous vide eleve et solidification progressive d'uranium d'origine electrolytique

Abstract

Within the general framework of research on uranium purification by zone melting, an attempt was made to determine the degree of purification which could be obtained by a simple gradual solidification of a normal nuclear-pure uranium paying close attention to the rate and direction of solidification. This uranium of intermediate purity would provide a starting material more suited to the first purification which is a vertical zone-melting process, so-called 'floating'. For this purpose, ingots of electrolytic uranium were melted under vacuum (2 to 5 x 10{sup -6} mm) in a long crucible after a slow rise in temperature to eliminate as much as possible the gases and volatiles impurities. This degassing and impurities volatilisation are completed by maintaining both at a high temperature for a considerable time. The beth is then made to solidify from the one an in the other the crucible by slowly moving the solid-liquid interface at a constant rate so as to obtain an impurity distribution according to the laws established by PFANN. Various experimental methods have made it possible to show that the metal which solidifies first is much purer than that at the other end of the ingot. The degree of purification of the  More>>
Authors:
Poeydomenge, P [1] 
  1. Commissariat a l'Energie Atomique, Saclay (France). Centre d'Etudes Nucleaires
Publication Date:
Jan 15, 1964
Product Type:
Thesis/Dissertation
Report Number:
CEA-R-2384
Resource Relation:
Other Information: TH: These sciences; 5 refs
Subject:
36 MATERIALS SCIENCE; ELECTRIC CONDUCTIVITY; GRAIN SIZE; KINETICS; PURIFICATION; RECRYSTALLIZATION; REFINING; SOLIDIFICATION; STRAIN HARDENING; TEMPERATURE CONTROL; URANIUM; VACUUM MELTING; ZONE MELTING
OSTI ID:
20818065
Research Organizations:
CEA Saclay, 91 - Gif-sur-Yvette (France); Faculte des Sciences de l'Universite de Paris, 75 (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR06R2384118194
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
55 pages
Announcement Date:
Dec 30, 2006

Citation Formats

Poeydomenge, P. Purification by high vacuum fusion and progressive solidification of uranium from electrolytic origin; Purification par fusion sous vide eleve et solidification progressive d'uranium d'origine electrolytique. France: N. p., 1964. Web.
Poeydomenge, P. Purification by high vacuum fusion and progressive solidification of uranium from electrolytic origin; Purification par fusion sous vide eleve et solidification progressive d'uranium d'origine electrolytique. France.
Poeydomenge, P. 1964. "Purification by high vacuum fusion and progressive solidification of uranium from electrolytic origin; Purification par fusion sous vide eleve et solidification progressive d'uranium d'origine electrolytique." France.
@misc{etde_20818065,
title = {Purification by high vacuum fusion and progressive solidification of uranium from electrolytic origin; Purification par fusion sous vide eleve et solidification progressive d'uranium d'origine electrolytique}
author = {Poeydomenge, P}
abstractNote = {Within the general framework of research on uranium purification by zone melting, an attempt was made to determine the degree of purification which could be obtained by a simple gradual solidification of a normal nuclear-pure uranium paying close attention to the rate and direction of solidification. This uranium of intermediate purity would provide a starting material more suited to the first purification which is a vertical zone-melting process, so-called 'floating'. For this purpose, ingots of electrolytic uranium were melted under vacuum (2 to 5 x 10{sup -6} mm) in a long crucible after a slow rise in temperature to eliminate as much as possible the gases and volatiles impurities. This degassing and impurities volatilisation are completed by maintaining both at a high temperature for a considerable time. The beth is then made to solidify from the one an in the other the crucible by slowly moving the solid-liquid interface at a constant rate so as to obtain an impurity distribution according to the laws established by PFANN. Various experimental methods have made it possible to show that the metal which solidifies first is much purer than that at the other end of the ingot. The degree of purification of the metal at the beginning of the ingot has been evaluated either quantitatively by measuring the ratio of the electrical resistivities at room temperature and at the liquid nitrogen temperature, or qualitatively by an examination of the micrographic structure and by a study of the recrystallisation of the metal. On the one hand the purified metal re-crystallises during iso-chromic annealings carried out at increasing temperatures, at a temperature much lower than the initial metal or than the end of the ingot. The passage from the cold-worked state to the recrystallised state is followed by micro-hardness measurements. On the other end, only is the purified metal, strongly cold-worked by unidirectional melting, is the phenomenon of 'dissociative growth' of the grain observed, so-called secondary recrystallisation. in appendix, the method for measuring the electrical resistance by induction (with direct current)is studied from the fundamental and experimental point of view. The author applied it to the particular case of uranium for measuring the low-temperature resistance of the bars from the same which solidified first to the least pure ended the ingot. (author) [French] Dans le cadre de recherches generales sur la purification de l'uranium par fusion de zone, on a entrepris de determiner le degre de purification que l'on pourrait atteindre par une simple solidification progressive a vitesse et direction soigneusement controlees d'un uranium de purete nucleaire courante. Cet uranium de purete intermediaire fournirait un materiau de depart approprie au mode de purification ultime qu'est la fusion a zone verticale, dite ''flottante''. Dans ce but, des lingots d'uranium d'origine electrolytique ont ete refondus sous vide (2 a 5 x 10{sup -6} mm) dans une longue nacelle en UO{sub 2} apres une monte lente en temperature pour eliminer le maximum de gaz et d'impuretes volatiles. Ce degazage et cette volatilisation d'impuretes sont completes par maintien prolonge a haute temperature du bais liquide. Celui-ci est ensuite solidifie d'une extremite a l'autre de la nacelle par deplacement a vitesse lente et constante du front de solidification de facon a obtenir une repartition des impuretes selon les lois etablies par PFANN. Differentes methodes experimentales ont permis de montrer que le metal solidifie en premier lieu est nettement plus pur que celui de la partie solidifie a l'extremite opposee du lingot. Le degre de purification du metal en tete du lingot a ete apprecie, soit quantitativement par mesure du rapport des resistivites electriques a la temperature ambiante et a celle de l'azote liquide, soit qualitativement par l'examen de la structure micrographique et par l'etude de la recristallisation du metal. D'une part, le metal recristalise au cours des recuits isochrones effectues a temperatures croissantes a une temperature nettement inferieur a celle du metal initial ou de queue du lingot. Le passage a l'etat ecroui a l'etat recristallise est suivi par mesures de la microdurete. D'autre part, seul le metal purifie tres fortement ecroui par laminage unidirectionnel est le siege au cours d'un recuit de recristallisation prolonge, du phenomene de ''croissance dissociative'' du grain, dit recristallisation secondaire. En appendice, la methode de resistivite electrique par induction (a courant continue) est etudie du point de vue fondamental et experimental. L'auteur l'a applique a un cas particulier de l'uranium pour mesurer a basse temperature la resitivite des barres depuis la region hautement solidifie le plus pres jusqu'a la queue des barres la plus impure. (auteur)}
place = {France}
year = {1964}
month = {Jan}
}