The High Flux Reactor (HFR) in Petten, the Netherlands, is a research reactor operated by Nuclear Research & consultancy Group (NRG). The 50MWthermal tank-in-pool reactor provides experimental facilities for materials research and production facilities for medical isotopes. The need for a full-scope Level 1-Level 3 (L1-L3) Probabilistic Safety Assessment (PSA) was identified during the most recent 10 yearly evaluation (periodic safety review, PSR.
The PSA scope is determined by the following applications: (1) to demonstrate compliance with the risk criteria as defined by the Nuclear Energy Act (Kernenergiewet, KeW), (2) the NRG policy with respect to Integrated Risk Management and (3) the HFR change management procedure. The result is a PSA which can be used for analysis of proposed design modifications, supporting PSR, and decision making during regular and exceptional situations.
An important feature of the KeW is that remnant risk of the installation comply with two metrics: the individual risk for an individual at any location outside the facility boundaries and the societal risk for the actual population outside the facility. This risk is caused by the different sources of radioactivity present in the HFR. However, comparing the risk of the different sources of radioactivity using L1 results (a surrogate risk metric) is meaningless. For example, the (possible) released activity due to a spent fuel accident can vary significantly compared to a core damage accident, as can the frequency of occurrence.
The L3 PSA aggregates the risk due to all sources. This results in the total risk due to the HFR, including risks with (relatively) high frequency and small dose and risks with low frequency and high dose. Furthermore, the L3 PSA shows that the risk of accidents with successful containment isolation is not negligible. The L3 PSA demonstrates that the HFR complies with the limits defined in the KeW.
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