Construction of a generic PSA model for Swedish BWRs

Abstract

The focus of this study is to develop and document a generic PSA model, based on SSM deterministic design requirements. The objective is to be able to use this model as a benchmark tool in the evaluation of new methods for probabilistic safety analysis, or in the evaluation of new design requirements. Three designs that fulfill SSMF 2008:17 design requirements were constructed and implemented into the computer code RiskSpectrum. The results from RiskSpectrum were compared to the results available in the safety reports of Oskarshamn 1, 2 and 3. The conclusions of this thesis are that the results show consistency between construction 1, 2 and 3. Sensitivity analysis of the probabilistic results demonstrates that the PSA models 1, 2 and 3 are robust. A robust concept can operate without failure under a variety of conditions. The study also indicates that models based SSMFS 2008:17 design requirements can lead to a design that is fire resistant. Both construction 1 and 3 live up to the requirements that are essential to represent the generic PSA model, however, construction 3 is more suitable as a benchmark tool as extraordinary fire mitigation measures do not need to be taken into consideration. Lesson to be learned is that one generic design/construction that fulfills SSMFS 2008:17 requirements may satisfactorily describe the plant and provide results with a sufficient level of details. Therefore future efforts should be directed towards the development and use of generic design/PSA models.