Experimental Validation of Hydrogen within a Filter-Vented Canister Containing Fukushima Fuel Debris

Abstract

This paper describes experimental evaluation of hydrogen removal from possible designs for passive filter vented storage of fuel debris from the Fukushima Daiichi Nuclear Power Station. Retrieved fuel debris will be first placed into a small cylindrical “unit can.” Four unit cans will be stacked inside a canister whose lid contains two high efficiency filters in series. Since the fuel debris contains water, hydrogen is generated in the canister by radiolysis and it must be discharged through filters to avoid forming a flammable mixture within the canister. A first group of experiments was designed to investigate hydrogen removal through a series of filters to create a performance curve for the hydrogen mole fraction difference across the filter as a function of its flow rate through the filter. These data were used to provide the value for the hydrogen flow resistance across the filter and to confirm models that include mass transfer to and from filter surfaces and between the interior and exterior of the canister lid. A second group of experiments was designed to investigate the distribution of hydrogen within a full size canister using lid designs tested in the first experiment group. These data confirmed that hydrogen will be essentially well-mixed in a canister, and mixing would be even better with decay power present. The conclusion is that possible designs for passive filter vented interim storage are safe with respect to flammable gas behavior.