​Twenty-five years ago the IAEA started its International Probabilistic Safety Assessment Review Team (IPSART) service to Member States. IPSART is an independent peer review of Probabilistic Safety Assessment (PSA) studies and PSA applications performed by different organizations in Member States. IPSART missions are conducted upon an official request submitted to the IAEA by the interested Member State. In total, more than 70 missions and review reports have been conducted and produced; these reports have served as a basis for refinements to the PSA studies.
 
Independent peer reviews are broadly recognized as an important means of providing the technical quality and consistency of the results and insights from risk assessment studies. Moreover, currently, a renewed interest towards the IAEA’s IPSART service is being observed. This can be attributed to the fact that important lessons have been learned for further improvement of the PSA methodology based on the analysis of the actual accident progression during the Fukushima accident in March 2011. Responding to the challenge, the IAEA included a module in its IPSART service titled “Review of the PSA Issues Highlighted by the Fukushima Accident”.
 
This year, two IPSART missions were conducted: a Follow-up IPSART Mission to Borssele NPP (PWR, KWU design) in the Netherlands and an IPSART Mission to Kozloduy NPP (VVER-1000 design) in Bulgaria.
 
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The mission to Borssele NPP was a follow-up of the full IPSART mission held in 2010; that mission reviewed a comprehensive PSA scope including all PSA levels, plant operational modes, initiating events and hazards (excluding seismic).
 
The objective of the Follow-up IPSART Mission in April 2013 was to review the updated and extended PSA model and documentation and to check how the comments documented in the official IPSART report for the mission conducted in 2010 have been addressed. Additionally, this mission carried out a trial application of the new IPSART module “Review of the PSA Issues Highlighted by the Fukushima Accident”.
 
Six invited experts from Germany, Hungary, Spain, Switzerland and the USA, led by the IAEA Safety Officer Artur Lyubarskiy, worked at the Borssele NPP site for 10 days to complete the review. The Follow-up IPSART Mission identified that many refinements have been implemented to the PSA study for Borssele NPP following the IAEA’s recommendations, especially in the areas of external hazards analysis and Level-2 PSA. Generally,  sound progress in addressing the IAEA’s recommendations has been identified. The plant is committed to using the plant-specific PSA as a living tool to support safe plant operation.
 
The IPSART mission to Kozloduy NPP was conducted in June 2013. It was led by IAEA Safety Officers Artur Lyubarskiy and Irina Kuzmina. Five experts from Armenia, Hungary, Russia, Switzerland and the USA were invited to contribute to the review. The review was performed within two weeks at the Kozloduy NPP site.
 
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The PSA scope reviewed included Level-1 PSA for Units 5 and 6 of Kozloduy NPP for internal initiating events caused by random component failures and human errors, internal fires and floods, and seismic events. The plant operational modes addressed in the reviewed PSA study included full power and low power/shutdown operation. In addition, the aspects of Living PSA and PSA applications were reviewed.
 
The overall conclusion from the IPSART mission to Kozloduy NPP is that a comprehensive risk analysis study has been done by the Bulgarian PSA team in accordance with current state-of-the-art in PSA methodology and IAEA Safety Guide on Level-1 PSA, SSG-3. The findings and recommendations for further refinement of the PSA study have been documented and discussed between the expert team and the PSA team. Specifically, it has been recommended by the IPSART mission that the scope of the PSA for Kozloduy NPP should be extended to include a broad spectrum of other internal and external hazards.
 
The IAEA IPSART service is a useful resource for independent peer review of PSA studies; it is especially valuable for countries with relatively small nuclear programmes lacking sufficient capacity for PSA expertise. IPSART missions provide advice on addressing risk insights in decision making, including compliance with safety goals and application of a formal Integrated Risk Informed Decision Making Process.
 
IAEA encourages Member States to invite IAEA IPSART missions to review PSA studies and PSA application projects for NPPs and other nuclear installations.
 
To read more about the IPSART Review Service, click here.