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. iv Table ES-1. Time to Core Damage Comparison for LOFW Scenarios with ATF Designs. Scenario Description Time to Core Damage (hr:min) Zircaloy FeCrAl Δt (FeCrAl) Chromite Δt (Chromite)

Risk-Informed Analysis for Enhanced Resilient Nuclear Power Plant with Initiatives including ATF, FLEX, and Advanced Battery Technology

“…If FLEX DGs are not available, it is assumed it leads to the CD state. The failure of this heading is determined by a static fault tree logic developed in the author's previous report (Ma, Z. et al, 2019a). The logic is also modeled within the EMRALD software.…”

“…Another focus area of the ATF efforts is to conduct a benchmark study between two probabilistic risk assessment (PRA) models-one is the generic pressurized water reactor (PWR) SAPHIRE model used in the FYs 2018 and 2019 ATF analyses under the ERP project (Ma, et al, 2018;Ma, Z. et al, 2019a;Ma, Z., et al, 2019b), and the other is the plant-specific PRA model of a reference PWR plant in U.S.. The benchmark study was motivated by mutual interests of the ERP team and the reference plant.…”

“…This section provides summarized descriptions of the computational tools used in the report. Although most of them were introduced in FYs 2018, 2019, and 2020 (Ma, et al, 2018;Ma, et al, 2019a;Ma, et al, 2019b;Ma, et al, 2020), the tools are described here in order for this report to be independent and complete.…”

“…Therefore, no event tree is developed. While this assumption could not be confirmed with the INL references (Ma, et al, 2018;Ma, et al, 2019a;Ma, et al, 2019b), it is assumed that similar evaluations and assumptions were made for the generic PWR model.…”

“…In the figure, the five basic events are modeled in the heading model as below. Each basic event contributes to the failure of Heading #1, and its failure probability is assumed from(Ma, Z. et al, 2019a):• DGs_Fail_CCF_Run: CCF of FLEX DGs to Run• DGs_Fail_CCF_Start: CCF of FLEX DGs to Start • DGs_Fail_Run: FLEX DGs Fail to Run • DGs_Fail_Start: FLEX DGs Fail to Start • DGs_Fail_TM: FLEX DGs Fail Due to Test and Maintenance.…”