OECD/NEA R&D priorities for loss-of-cooling and loss-of-coolant accidents in Spent-Fuel-Pools

Abstract

Motivated by the 2011 accident at the Fukushima Daiichi Nuclear Power Station, the Nuclear Energy Agency (NEA) Committee on the Safety of Nuclear Installations (CSNI) of the Organisation for Economic Cooperation and Development (OECD) launched several activities with the aim to support the post-Fukushima accident decision making process. One of these activities, discussed in the present paper, consisted in the production of a Phenomena Identification and Ranking Table (PIRT) in order to systematically highlight Spent-Fuel-Pool (SFP) accident-related phenomena that are of both high importance and high uncertainty, and thus of primary interest for further experimental or modeling activities. For that purpose, an international panel of experts identified and ranked more than a hundred physical phenomena with regard to their safety importance and current level of knowledge. Altogether eighteen unique phenomena were identified as having priority research needs. About half of these phenomena are related to thermal-hydraulics and heat transfer in the SFP, and they are judged to be important to the coolability of the spent fuel in loss-of-cooling and/or loss-of-coolant accidents. The other half comprises fuel-related phenomena such as fuel volatilization, cladding oxidation in mixed steam–air environment and nitrogen-assisted oxide breakaway at moderate temperature, judged as important and poorly modeled in the scope of SFP accidents. The final part of the paper discusses the research programmes performed on Spent Fuel Pool loss-of-cooling and loss-of-coolant accidents since the publication of the PIRT report in 2018 and the remaining R&D needs.