77 Analysis of Shutdown Mode at BarsebÄck 2; an Approach to a Combined PSA, HFA and Deterministic Analysis (PSAM-0117) Available to Purchase

The aim of the shut down analysis was to produce a full Safety Analysis Report (SAR) for the shutdown and outage states including re-fueling. The SAR should contain both a deterministic and a probabilistic analysis (this is a requirement in Sweden today). The two analyses were performed in parallel with both common parts and common support activities. The probabilistic analysis should comprise both Level 1 and Level 2. The main intention of the parallel process was to form a homogeneous analysis, i.e. that equal limitations, conditions and assumptions were used. Another intention of the parallel process was to facilitate the interface between the analyses. The deterministic analysis is also becoming more realistic, which also is a reason to keep the analyses together.

Project goal, content of the analysis, method descriptions and acceptance criteria were defined in common documents. It was identified that there was a need to define specific acceptance criteria for the shutdown modes. This is due to that the acceptance criteria normally are defined for full power operation with all safety systems and barriers intact and in operation (this also included the definition of plant conditions).

The analysis should form a basis for the SAR, why normal PSA assumptions regarding plant operating modes and system configurations could not be accepted. The analysis would have to consider all possible situations that were stipulated by the Technical Specification (TS). The issue was that the TS should not allow a configuration that had not been analyzed. A thorough identification of different system configurations in the different phases was conducted. All initiating events were then mapped so that they could be assigned to one or more system configurations for each possible phase.

The main task for the HFA (Human Factor Analysis)) was to define the initiating events caused by manual actions. The mapping of initiating events caused by manual actions was focused at:

• Loss of residual heat removal

• Loss of coolant

• Dropped load / damage during transport

• Criticality events

The HFA (Human Factor Analysis) analyzed the organization for planning and conduction of the work during shutdown. The Performance Shaping Factors (PSF:s) from this analysis were used in the quantification of the human errors.

The analysis was not complete when Barsebäck 2 was shutdown in 2005. This paper describes the approach of the analysis and the analysis as far as it was conducted.