Study of hydrogen generation and radionuclide release during wet damaged oxide spent fuel storage
This paper describes the results of the experimental study of hydrogen and gaseous fission products (GFP) accumulation under conditions simulating the interim storage of damaged VVER-440 spent nuclear fuel (SNF) in the leak-tight canisters after successful canister draining but without fuel drying. Physical and chemical processes during wet storage of damaged oxide SNF are discussed. The experiments were carried out in two stages: 1) filling a leak-tight canister containing fuel pellet fragments with water and 2) draining the leak-tight canister and holding wet SNF inside.
The experiments were carried out successively with one and the same canister and differed only in the holding temperatures: 25°C and 80°C.
The data on the release of radionuclides to liquid phase during underwater storage of SNF was obtained from the experiments. Steady-state concentrations of uranium and cesium isotopes were found to be reached when storing SNF under water for more than a month. The kinetics of hydrogen and gaseous fission products accumulation in gas phase during wet spent fuel storage in a leak-tight canister after draining coincide for both experiments. This kinetics demonstrates a sharp decrease of the hydrogen and gaseous fission products accumulation rate after 46 hours of the experiments. The data obtained can be applied in development and verification of modeled processes of damaged SNF behavior during SNF wet storage under radiolysis conditions.
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