Probabilistic Safety Assessment (PSA) Benchmark for Multi-Unit/Multi-Reactor Sites

Closed for Proposals

Project Type

Coordinated Research Project

Project Code

I31031

CRP

2147

Approved Date

2017.07.13

Project Status

Closed

Start Date

2018.02.14

Expected End Date

2022.02.15

Completed Date

2023.09.18

Participating Countries

United Arab Emirates, Argentina, Canada, China, Finland, Ghana, Hungary, India, Republic of Korea, Pakistan, Romania, Russian Federation, Tunisia, Ukraine

Description

Many nuclear power plants (NPPs), either of the same or of different types, designs, or age, are co-located on a single site. While operators and regulators recognize the potential for multiunit accidents, clearly demonstrated during the Fukushima-Daiichi accident in March 2011, past probabilistic safety assessments (PSA) of NPPs have only estimated the risk arising from damage to?one single NPP at a time.?This CRP will bring together experts from the Member States with water cooled reactor technologies to utilize, test?and further develop their current (or planned) PSA?methods and?assumptions?by conducting, and comparing results of, a meaningful benchmark exercise. The exercise will involve development of Multi-Unit/Multi-Reactor-Type PSA (from here on referred to as MUPSA),?based on single-unit PSA available in Member States. The insights gained from the exercise may identify technology solutions to reduce?those risk contributors that are specific to multi-unit effects.

Objectives

Promote international collaboration among IAEA Member States through the sharing of expertise and participation in the common benchmark calculations.

Specific Objectives

Identify main risk contributors that delineate multi-unit risks from single-unit risks.

Develop best practice guidance for conducting Level 1&2 multi-unit PSAs.

Successfully complete the benchmark exercises and document lessons learned.

Impact

- The CRP developed the first coordinated benchmark methodology for multi-unit PSA.
- It highlighted the need to assess whole-site risk beyond single-unit summations.
- Helped identify gaps in current PSA frameworks regarding shared SSCs, interdependencies, and external hazards.
- Supported capacity building and PSA development across participating Member States, including countries without NPPs yet.

Relevance

The CRP addresses:
- A critical safety gap exposed by the Fukushima accident (complex interactions in multiunit sites).
- A need for new methodologies for emerging nuclear technologies like SMRs and modular HTGRs.
- Provides technical foundations for safety evaluations and regulatory development in multi-unit NPP environments.