Phenomena Identification and Ranking Table: R&D Priorities for Loss-of-Cooling and Loss-of-Coolant Accidents in Spent Nuclear Fuel Pools

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The main objective of the report is to identify research and development priorities related to loss-of-cooling and loss-of-coolant accidents in spent fuel pools. This is done by applying a PIRT process methodology to identify phenomena that are both of high safety importance and of high uncertainty and therefore deserve further comprehensive analytical and/or experimental studies.
The PIRT process is applied on at-reactor SFPs. The study is generic with regard to reactor and fuel design, it covers boiling water reactor (BWR), pressurised water reactor (PWR), Russian-type pressurised water reactor (VVER) and Canada Deuterium Uranium (CANDU) reactor power plants. Two general types of accidents are studied: a loss-of-coolant accident with fast drainage of the pool water, and a loss-of-cooling accident with slow uncovery of the spent fuel by gradual water evaporation and boil-off. Three separate sub-PIRTs are developed for three consecutive phases of the considered accident scenarios: the pre-uncovery phase, the uncovery phase and the fuel damage phase. This temporal subdivision is made, since the three phases can be dominated by different phenomena.
The study is restricted to phenomena that occur in the spent fuel pool. Phenomena occurring predominantly outside the SFP, e.g. heat and mass transfer in the pool building, are beyond the scope of the study. However, these phenomena are discussed in terms of boundary conditions to the SFP, when they are deemed to be important to the in pool accident progression.