Application of SLP PSA

Ideally a SLP PSA may used for the outage planning in an iterative way. The draft outage plan is assessed by a SLP PSA. Sensitivity studies are used to minimise the risk associated with certain tasks. The SLP PSA may be used to justify the moving of some tests and preventive maintenance from an outage to the full-power operation or to justify the selection of simultaneous or sequential testing practices 

It has to be noted that a SLP PSA is not an ideal tool for day-to-day outage planning due its rather complex models. However, no other tool can mach the SLP PSA capabilities addressing dependencies, complex human interactions and similar phenomena. 

By identifying the risk significance of the unavailability of the safety and support systems, a SLP PSA may provide a feedback to the development of the additional Technical Specifications for outages. 

During the performance of a SLP PSA, accident sequences which strongly depend on recoveries initiated by the operators may be identified. For those recoveries, emergency operating procedures may then be developed utilising SLP PSA generated insights. 

Plant specific SLP PSAs were performed in many European countries (Sweden, UK, France, Spain, Switzerland, Finland, Belgium etc.) and in most cases were successfiilly used to avoid high risk configurations and to identify backfits for specific operating conditions. After implementing the backfits, the contribution of SLP PSA to the overall risk was often significantly reduced. 

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This section discuses various modelling issues which are of relevance for a full scope shutdown and low power PSA models. The modelling issues discussed include the definition of plant operating states, initiating events, screening analyses, modelling of accident sequences, dependency analysis, quantification of sequences and applications of SLP PSA. 

The frequencies of lEs considered in the Full-Power PSA may be only the starting point in defining the lEs frequencies for SLP PSA. Many of the Full-Power PSA lEs are not directly applicable and the... 

Some systems may require specific modelling for a SLP PSA because they are not considered in the power PSA. An example is the Spent fuel pool cooling system. Some operating modes of the RHR system may be specific to a POS. System recoveries credited in power PSA may not be applicable due to on-going activities or due to limited accessibility, etc. 

Specific studies were undertaken on the applicability of operational events analysed with SLP PSA on German reactors. 

The SLP PSA study for Borselle NPP was completed in 1994. It turned out to be one of the major studies as far as the applications of innovative methods and approaches. The study considered both internal and external initiators and Level 2 Analysis. Limited Level 3 Analysis was partially performed. 

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