Risk-Informed Analysis for an Enhanced Resilient PWR with ATF, FLEX, and Passive Cooling

Abstract

This report documents the activities performed by Idaho National Laboratory (INL) during the fiscal year (FY) 2019 for the DOE Light Water Reactor Sustainability (LWRS) Program, Risk-Informed System Analysis (RISA) Pathway, Enhanced Resilient Plant (ERP) Systems research. The purpose of the RISA Pathway research and development is to support plant owner-operator decisions with the aim to improve the economics, reliability, and maintain the high levels of safety of current nuclear power plants over periods of extended plant operations. The concept of ERP refers to the combinations of Accident Tolerant Fuel (ATF), optimal use of Diverse and Flexible Coping Strategy (FLEX), enhancements to plant components and systems, and the incorporation of augmented or new passive cooling systems, as well as improved fuel cycle efficiency. The objective of the ERP research effort is to use the RISA methods and toolkit in industry applications, including methods development and early demonstration of technologies, in order to enhance existing reactors safety features (both active and passive) and to substantially reduce operating costs through risk-informed approaches to plant design modifications to the plant and their characterization. The FY 2019 efforts documented in this report is an extension of those conducted in FY 2018. The same analysis process, risk analysis approaches, and analysis tools as in FY 2018 are used for near-term ATF cladding [i.e., Iron-Chromium-Aluminum (FeCrAl) cladding and Chromium (Cr) coated cladding] designs under the postulated loss of feedwater (LOFW) and steam generator tube rupture (SGTR) accident scenarios. In addition, FLEX analysis was presented for an overview of FLEX equipment and strategies implemented in nuclear industry after Fukushima accident. A FLEX model was developed and incorporated into the generic SAPHIRE model to assess the risk impact from FLEX. FLEX HRA analysis was performed which suggested an approach to HRA with FLEX strategies. Passive cooling system analysis includes an overview of the DNC system, the RELAP5-3D simulations of the DNC system in selected SBO scenarios, and the evaluation of the DNC system risk impact using the generic PRA model.