Application of the integrated safety assessment methodology to the emergency procedures of a SGTR of a PWR

Abstract This paper describes an application of the Integrated Safety Assessment (ISA) methodology to the safety and reliability assessment of emergency procedures of a nuclear power plant. The concept of ISA has been developed as a result of previous works on safety assessment and dynamic reliability. The method links the physical dynamics of the facility with its operating environment, subject to transitions between different time evolutions due to failures and/or system/operator interventions. For situations dominated by deterministic transitions (i.e. transitions upon deterministic demands as a result, for instance, of exceeding automatic actions or alarm setpoints), the methodology can be considered an extension of PSA and accident analysis techniques that replaces the static event tree with a deterministic dynamic event tree concept (DDET) based on the theory of probabilistic dynamics. In line with current studies carried out jointly by CSN and JRC-Ispra/ISEI, this paper reviews the main features of ISA and describes some of the details of its implementation in the case of a Westinghouse pressurized water reactor (PWR), in particular its application to the assessment of the emergency operating procedure (EOP) to mitigate the steam generator tube rupture (SGTR) initiating event. This application demonstrates the ISA feasibility for risk analysis of operating procedures (OP) by assessing a given set of OPs with a large PWR model of the TRETA-DYLAM-HOI software package, which is able to simulate recovery in a SGTR scenario. Some weak points in the SGTR EOP are identified and suggestions provided for their resolution.