Advancing the understanding of spent fuel pools during loss of cooling accidents

Pool storage containers - Swedish Nuclear Fuel (SKB)

Photo credit: Pool storage containers: Swedish Nuclear Fuel (SKB)

Following the Fukushima Daiichi nuclear power plant accident, the international nuclear community initiated a deep assessment of the safety of spent fuel pools (SFP), which store spent fuel from nuclear reactors. A number of actions were launched since the accident in an attempt to mitigate the risk of a potential SFP accident.

The NEA Working Group on the Analysis and Management of Accidents (WGAMA) is responsible for activities related to potential accidental situations in nuclear power plants and helping to understand and to reduce the risk and the consequences of an SFP accident is a focus area for the group.  

Approximately 30 experts from WGAMA assembled at the French Institute for Radiation Protection and Nuclear Safety (IRSN) in Cadarache, France to discuss how to advance the understanding of SFP phenomena during a loss of cooling accident.

The working group, representing 10 different countries at the meeting, also considered the ‘POLCA’ (Pool during Loss of Cooling Accident) proposal, a potential future joint project that would pursue the experimental analysis of the behaviour of SFPs in the situation of a loss of cooling accident.


Members of the Working Group on the Analysis and Management of Accidents visiting the ASPIC and MIDI facilities at IRSN in Cadarache, France

The POLCA joint project would aim to:

  • enhance knowledge on SFP accidents;
  • support better understanding of large scale pools to provide thermal hydraulics data;
  • support the thermo-hydraulics model development and validation for SFPs under loss of cooling accident;
  • evaluate some mitigation strategies concerning assembly management.

The POLCA project would focus on the experimentation of large scale facilities (MIDI and ASPIC) with dedicated instrumentation to the thermohydraulic behaviour of SFPs during loss of cooling accidents. It would also aim to contribute to the enrichment of an experimental database, useful to improve thermohydraulic numerical tools in pool conditions.

Several designs of heat removal systems in nuclear power plants consider large pools with immersed heat exchangers. Recently these pools have been considered within some passive systems for reactor decay heat removal systems. Therefore, the knowledge of natural circulation flow within the MIDI facility is of interest for the validation of any scientific calculation tool used to model such passive systems.

Photo credit Large scale MIDI facility at IRSNPhoto credit: Large scale MIDI facility at IRSN.  

The POLCA joint project proposal will be presented to the Committee on the Safety of Nuclear Installations (CSNI) for their endorsement.

During the meeting at IRSN, the experts also exchanged on the status on SFP regulation, accident analysis, and the R&D activities needs for SFPs in their countries.

You can read more about the NEA’s work on nuclear power plant accident management on the WGAMA webpage.

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