Final evaluation of plant safety

After completion of the design process, the failure probabihty both at the structure, system and component level and at the facility level is evaluated and an overall performance evaluation carried out. At the end of the design process, the external event hazard is available in detail. The performance evaluation in relation to external events includes the following steps  

Step 1 Selection of the success path and/or accident sequences to be considered in the safety analysis. 

Step 2 Evaluation of individual structure, system and component fragilities on the basis of the design documentation. A simplified evaluation can be carried out on the basis of the design review and design code analysis. The outcome of this evaluation is the median capacity and associated variability. The capacity variability can be evaluated using generic data and 

Step 3 Use Eq. (1) to calculate the failure probability and compare Pp with the performance goal (check Eq. (3)) for any structure, system or component. Combine individual structure, system and component fragilities to derive the overall fragility for the research reactor (an example of seismic fragility is given in Appendix 2). Weak links can be identified and design changes recommended. 

Step 4 Calculate the release arising from structure, system or component failures consistent with the safety analysis. Evaluate the global probability of release at the facility level, for comparison with basic safety requirements. 

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