Behaviour of Short-Lived Fission Products Under Fuel Accident Conditions: Chalk River Studies

Abstract

We have carried out three in-reactor tests to determine the behaviour of short-lived fission products (Xe,Kr,I) under accident conditions. Oxidizing conditions enhanced release by a factor of about 4.5 During fuel dryout, there was some release during the heat-up stage, but most occurred on rewet, consistent with transport in cracked fuel. In contrast, maximum release was observed during the rapid heat-up stage (less than 30 s) in blowdown tests, possibly associated with increased diffusion, grain boundary sweeping and microcracking. Despite the significant temperature transients (fuel central temperature increasing from 1700 degrees c to 2300 degrees C in dryout and blowdown), integrated releases were only 0.1 - 1% of total fuel inventory. No iodines were observed at the spectrometer or on piping downstream of the fuel test section.