A proposal of hydrogen safety technology for decommissioning of the Fukushima Daiichi Nuclear Power Station

The safe removal, transportation, and long-term storage of fuel debris in the decommissioning of Fukushima Daiichi is the biggest challenge facing Japan. In the nuclear power field, passive autocatalytic recombiners (PARs) have become established as a technology to prevent hydrogen explosions inside the containment vessel. To utilize PAR as a measure to reduce the concentration of hydrogen generated in the fuel debris storage canister, which is currently an issue, it is required to perform in a sealed environment with high doses of radiation, low temperature, and high humidity, and there are many challenges different from conventional PAR. A honeycomb-shaped catalyst based on automotive catalyst technology has been newly designed as a PAR, and research has been conducted to solve unique problems such as high dose radiation, low temperature, high humidity, coexistence of hydrogen and low oxygen, and catalyst poisons. This paper summarizes the challenges of hydrogen generation in a sealed container, the results of research, and a guide to how to use the PAR for fuel debris storage canisters. • This paper guides using “passive autocatalytic recombiners” in fuel debris storage. • A full-scale prototype visualized the catalytic effect during hydrogen oxidation. • Ventilation issues were clarified by theoretical flow calculations and experiments. • Natural convection velocity via catalytic reaction was evaluated using REKO-4. • Even small catalysts maximize hydrogen conversion in fuel debris storage canisters.