Occluded Gas Content in Fast Breeder Reactor Fuels

Abstract

A comprehensive analytical methodology based on hot vacuum extraction principle was developed for the determination of total/occluded gas content in ceramic fast reactor nuclear fuels such as (U, Pu)C and (U, Pu)O2 of different bulk compositions. In view of the stringent specifications imposed on these fuels with respect to total gas, detailed investigations were carried out to understand and interpret the implications of the definition of the occluded gas content. These investigations include selecting the temperature and duration of heating, method of gas collection (with and without gas refrigeration) as well as measuring the gas composition employing quadrupole mass spectrometer. Hydrogen was found to be the major constituent of the occluded gas (>95%) followed by minor quantities of N2, CO and CO2. These observations showed the necessity of introducing a vacuum degassing step after sintering and also helped in redefining the specification of total gas content. The total gas content is less than 0.1 cm3.g−1 excluding hydrogen. The measurement error is ±5%.