Level 2 PSA for the US and UK EPR

Jacobsen Analytics have provided support over the last 5 years to Areva NP Inc (USA) and Areva NP SAS (France) throughout the development of the Level 2 PSA for the EPR design. Our initial involvement in the project was for the US Design Certification project, and we subsequently supported Areva NP SAS for the adaptation of the Level 2 PSA for use in the submission to the UK Generic Design Assessment process. We have also continued to support the US Design Certification process for the EPR in the area of Level 2 PSA during the USNRC's regulatory review of the submission.

The EPR Level 2 PSA is a fully linked model, integrated with the Level 1.

Our scope of work for the US EPR Design Certification Level 2 PSA included:

  1. Development of Level 1 to Level 2 linking via assignment of Core Damage Endstates
  2. Development of Containment Event Tree (CET) models in Riskspectrum
  3. Development of supporting fault tree models
  4. Development of Release Category allocation for CET endpoints
  5. Quantification of the model
  6. Development of supporting phenomenological evaluations on direct containment heating, hydrogen loads, loads at vessel failure failure, in-vessel and ex-vessel steam explosions
  7. Review of other supporting phenomenological evaluations

The EPR Level 2 PSA was developed to be a high quality Level 2 PSA using contemporary approaches. Key features of these approaches were:

  1. the use of an integrated model within Riskspectrum,
  2. extensive use of Monte-Carlo simulation for the modelling and generation of phenomenological event probabilities,
  3. incorporation of Severe Accident Management actions, including rigorous consideration of HFE dependencies in the Level 2 and with the Level 1, and
  4. quantitative uncertainty propagation, integrated across the Level 1 and Level 2.

For the UK EPR Level 2 PSA developed for the submission to ONR for Generic Design Assessment, our contrbution was:

  1. Extension of the analysis to shutdown
  2. Modification of Containment Event Tree models and integration of these with UK EPR Level 1
  3. Quantification and results analysis
  4. Preparation of sections of Areva's UK PCSR Chapter 15.4

Further information on the UK EPR Level 2 PSA can be found at UK EPR PCSR Chapter 15.4 web version