ANALYSIS OF GAS SAMPLES COLLECTED FROM THE DOE HIGH BURN-UP DEMONSTRATION CASK

摘要

The DOE and industry collaborators have initiated thehigh burn-up demonstration project to evaluate the effectsof drying and long-term dry storage on high burn-up fuel.Fuel was transferred to a dry storage cask, which wasthen dried using standard industry vacuum-dryingtechniques and placed on a storage pad to be opened andthe fuel examined in 10 years. Helium fill gas sampleswere collected 5 hours, 5 days, and 12 days after closure.The samples were analyzed for fission gases (85Kr) as anindicator of damaged or leaking rods, and then analyzedto determine water content and concentrations of othertrace gases. Gamma-ray spectroscopy found no detectible85Kr. Sample water contents proved difficult to measure,requiring heating to desorb water from the inner surfaceof the sampling bottles. Final results indicated that waterin the cask gas phase built up over 12 days to 17,400ppmv ±10%, equivalent to ∼100 ml of water within thecask gas phase. Trace gases were measured by direct gasmass spectrometry. Carbon dioxide built up over twoweeks to 930 ppmv, likely due to breakdown ofhydrocarbon contaminants (possibly vacuum pump oil) inthe cask. Hydrogen built up to nearly 500 ppmv. and maybe attributable to water radiolysis and/or to metalcorrosion in the cask.