THE EFFECT OF FISSION-PRODUCTS ON THE RATE OF U3O8 FORMATION IN SIMFUEL OXIDIZED IN AIR AT 250-DEGREES-C

The effect of fission products on the rate of U3O8 formation was inves tigated by oxidizing UO2-based SIMFUEL (simulated high burnup nuclear fuel) and unirradiated UO2 fuel specimens in air at 250 degrees C for different times (1-317 days). The progress of oxidation was monitored by X-ray diffraction, revealing that the rate of U3O8 formation declin es with increasing burnup. An expression was derived to describe quant itatively the time for U3O8 powder formation as a function of simulate d burnup. These findings were supported by additional isochronal oxida tion experiments conducted between 200 and 300 degrees C.