Mobilising the right competencies - PSA review and methodology development

About KEPCO E & C

KEPCO E & C is a world-class power company, active across the power value chain including generation, transmission, transformation, and distribution. The company is a leader in the nuclear power sector, with involvement in operational and new-build nuclear power plants at home and overseas.

Background to the project

KEPCO was involved in the bidding process for a fourth nuclear power plant for the Finnish nuclear power company Teollisuuden Voima Oyj (TVO) in Olkiluoto, the so called OL4 reactor. KEPCO approached Vysus Group in order to seek assistance with reviewing their current Probabilistic Safety Assessment (PSA) for the APR1400 generic reactor design. The review needed to be done against Finnish and European requirements and international best practice.

KEPCO also wanted a number of PSA methodology documents to be developed by Vysus Group and a methodology document on how to incorporate PSA results into the classification process of Structures, Systems and Components (SSCs). The methodologies outlined in the documents needed to comply with applicable Finnish regulatory guidelines (YVL). In order to meet TVO’s timelines, KEPCO needed to have these developed early in the bidding process.

How we helped

One of the main challenges KEPCO faced was the large volume of complex work that needed to be completed in a short period of time. Vysus Group, with its network of world leading experts, was able to quickly mobilise the right competencies to deliver the requirements to a high standard. Robust systems and seamless project management processes enabled the team to coordinate across multiple locations – ensuring that work continued around the clock. Quality and consistency was rigorously controlled, overseen by an expert panel which reviewed all findings before the documents were finalised and delivered to KEPCO.

As the Finnish nuclear regulatory body (STUK) was in the process of updating their regulatory YVL guides, Vysus Group
had to use available preliminary versions - and our knowledge and experience from having performed PSAs for more than 25 years. Some of the topics (such as decommissioning PSA) were relatively novel, so it was necessary to perform literature surveys to support the development of methodology documents.

Vysus Group’s network of experts, SSC Classification Process supported by robust systems and seamless project management processes enabled the team to coordinate across multiple locations.

Project scope

The project deliverables included:

A full review and gap analysis of existing PSA against identified requirements and guidelines where the review findings (gaps) were classified in a structured manner depending on their importance/severity in order for KEPCO to be able to prioritise their future activities. This included:

General review of the PSA including
• Presentation and interpretation of PSA results
• QA procedures
• PSA documentation
• Review of internal events
• Review of internal fire/flooding PSA (from screening process to quantification and interpretation of results)

Review of seismic analysis
• Seismic and Fragility analysis and incorporation in PSA model
• No site-specific analysis was performed which limited this to general methodology V.

Review summary
• The entire review/gap analysis was documented, identifying the pros and cons

Development of methodology documents including a summary of relevant requirements and guidelines. The following set of methodology documents were developed:

Full-Power external events Level 1 PSA, including:
• Fire
• Flood
• Seismic and other external events

Low power and Shutdown (LPSD) PSA (Level 1 and Level 2)
• Spent Fuel Pool PSA
• Decommissioning PSA
• Incorporation of PSA results int
• SSC Classification Process

Powerful results

The OL4 reactor bid process has since been put on hold by TVO but, with Vysus Group’s help, KEPCO completed with submission on time and within budget.