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Conference Article: Quality control of uranium-plutonium mixed carbide and nitride fuels

Maeda, A.; Iwai, T.; Ohmichi, T.; Handa, M. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan))

Abstract

The special characterization methods and apparatus developed for the quality control of uranium-plutonium mixed carbide and nitride fuels are described. For the determination of oxygen in carbides, it is very important to prevent the samples from oxygen contamination before loading them into an analyzer. A new sample preparation procedure was developed, i.e., carbides were pulverized, weighed and hermetically pressure sealed immediately into platinum capsules in a high purified argon atmosphere (oxygen and moisture levels less than 2 ppm). It was revealed that even in such a high purified argon atmosphere, fine carbide powders were oxidized with oxygen and moisture. The true oxygen content was successfully estimated by extrapolating the oxygen values determined at various exposure times to zero. The carbon loss via methane gas produced by the reaction of carbides with trace moisture at room temperature was relatively small presumably because of the adsorption of methane on fuel surface. For .X-ray diffraction analysis, a sophisticated method was adopted to preserve samples from oxidation during measurement, namely, the mixture of the fuel powder with a small quantity of epoxy resin was mounted on a sample holder in the argon atmosphere. The gas occluded in the fuels was measured by the apparatus with a newly designed gas line filter. For mixed carbide fuels, most of the gases evolved below 1473K was hydrogen. Above this temperature, carbon monoxide equilibrated with oxycarbide was released continuously. An electron probe microanalyzer connected with glove boxes was constructed. About thirty modifications were incorporated to facilitate the repair of the analyzer contaminated with plutonium.

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key words: fuel pellets; lmfbr type reactors; microstructure; mixed oxide fuels; plutonium nitrides; quality control; sample preparation; uranium nitrides; x-ray diffraction
Reference:
Technical committee meeting on advanced fuel for fast breeder reactors: Fabrication and properties and their optimization. Vienna (Austria). 3-5 Nov 1987
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--466, pp:34-41