Services for probabilistic risk assessment (PRA)

VTT’s services for PRA in the nuclear domain

VTT supports the safe and efficient use of nuclear power, including nuclear waste management, by offering services on PRA modelling, analysis, reviews, training, method development and tool development.

VTT’s PRA knowledge covers all three levels of PRA. For level 1, VTT is capable of performing analyses on internal and external hazards, power operating mode PRA, low power PRA and shutdown PRA. VTT has executed commercial projects on human reliability analysis (HRA), digital I&C systems, and fire and flood analyses. For level 2, VTT offers dynamic containment event tree analysis that integrates deterministic and probabilistic analyses. For level 3, VTT offers consequence assessments and develops state-of-the-art methods. VTT can also perform PRA modelling and analysis for non-reactor nuclear facilities, as well as non-nuclear industry applications. In commercial projects, VTT has also performed PRA for the encapsulation of spent nuclear fuel, a district heating network and a military unit under attack.


Defence in depth and PRA, SKI Report 2008:33.

Scientists at VTT have been active especially in the areas of digital I&C and HRA. VTT’s experts possess methods to analyse and model the reliability of the hardware and software of digital I&C systems in PRA. The failure probabilities of safety I&C software modules can be estimated based on the software complexity, and verification and validation procedures. VTT has know-how on the state-of-the-art HRA methods and has experience on performing HRA reviews against regulations and international guidelines.

VTT supports risk-informed applications including in-service-inspections, allowed outage times, safety classification and technical specification.

VTT’s FinPSA software supports PRA activities. VTT also provides a number of PRA supporting deterministic analyses such as severe accident analyses, thermo-hydraulic analyses and fire simulations.

Reference projects
  • Development of an application for utilizing PRA in the assessment of security measures (STUK)
  • Development of a software reliability analysis method for nuclear power plant’s PRA (TVO and Fortum)
  • Review of the HRA of power plant units (STUK)
  • PRA for the spent fuel pool storage — Fire and flood analyses (TVO)
  • Review of reliability analysis software
  • PRA for the final encapsulation and repository facility for spent nuclear fuel (Posiva)
  • Reliability analysis of a district heating network (Helsingin Energia)
  • Reliability analysis of a military unit under attack (Finnish Defence Forces)