Risk-Informed Performance-Based Technology. Inclusive Guidance for Advanced Reactor Licensing Basis Development (NEI 18-04)

Abstract

This guideline presents a modern, technology-inclusive, risk-informed, and performance-based (TI-RIPB) process for selection of Licensing Basis Events (LBEs); safety classification of structures, systems, and components (SSCs) and associated risk-informed special treatments; and determination of defense-indepth (DID) adequacy for non-LWRs. This guidance document provides one acceptable means for addressing the aforementioned topics as part of demonstrating a specific design provides reasonable assurance of adequate radiological protection.

Modernization of Technical Requirements for Licensing of Advanced Non-Light Water Reactors: LMP Lessons Learned, Best Practices, and Frequently Asked Questions

“…Task 5a in Figure 3-2 in NEI 18-04 [32] One of the RSFs for the MHTGR was identified as "control core heat removal." In considering how Design Basis Events might increase in consequences if that Required Safety Function (RSF) was not fulfilled, it was determined that fuel temperatures could increase and depending on the extent to which heat removal was not controlled, the fuel temperatures could exceed ANY temperature limit including the limits where the TRISO fuel particles would fail.…”

“…As discussed throughout NEI 18-04 [32] and the supporting LMP reports, the application of the LMP methodology may be implemented as an iterative process. In addition, there is flexibility in how and when the process tasks in the LMP methodology are applied.…”

“…The answer to this question is addressed in the text that discusses Figure 3-2 in NEI 18-04 [32] and is expanded on in the LMP LBE report in the text that discusses Figure 1-1. [23] To provide further clarification on this question, the following considerations are offered:…”

“…The use of controlled maintenance programs as part of the conduct of operations are part of the Programmatic Capability described in the LMP methodology [32] in Sections 4.4 and 5.8. There are some conceptual similarities between the 10 CFR 50.65 Maintenance Rule and the LMP approach to setting and monitoring performance of SSCs; however, they are not substitutes for one another and have significant differences in scope and implementation.…”

A Limited-Scope Probabilistic Risk Assessment Study to Risk-Inform the Design of a Fuel Storage System for Spent Pebble-Filled Dry Casks

“…The main objective of the RI is to demonstrate risk-significance criteria with the associated uncertainties of the event sequences. To estimate the risk importance, several risk metrics are suggested and measured for expressing risk based on relative and absolute risk significance [57]. The absolute risk metrics are represented by core damage frequency (CDF), large early release frequency (LERF), or Birnbaum Importance, whereas, for ranking the risk order or establishing the regulations, relative risk measures, including Fussell-Vesely, Risk Achievement, or Risk Achievement Worth, can be used [58].…”