A METHOD OF CALCULATING FISSION GAS DIFFUSIONnFROM U02 FUEL AND ITS APPLICATION TO THE X-2-f LOOP TEST

摘要

A method for calculating the fraction of the rare gas fission products that diffuses out of a UO2 fuel element under conditions in a reactor is outlined. The method is based on the values of the diffusion constant found in labora¬tory experiments, as described in CRDC-718, and assumes that these remain unaltered during the period that the fuel is in the reactor. The method has been applied to two types of oxide in the X-2-f loop test of 1956 and the results com¬pared with the amounts of fission gas found by analysis of the gases collected in sheath puncture experiments, as des¬cribed in CRDC-719. The calculated values depend heavily on the estimated temperatures in the fuel. They are in close agreement with the experimental values provided that, in calculating the temperature, certain assumptions are made regarding the thermal expansion of the oxide cylinder.