A Demonstration of the Risk-Informed NEI 18-04 Design Evaluation Model for the Modular High Temperature Gas Reactor

Several advanced reactor designs are now under active development in the U.S., promising sustainable solutions to the growing world energy needs as well as serving an ever-expanded spectrum of energy applications which are now not limited to electricity production.The designs currently considered are quite diverse and different from the more established light water reactor technology that has dominated the operating commercial nuclear landscape.While advanced reactor concepts were first explored in the dawn of the nuclear age, they are now being reconsidered under the light of modern needs, and specifically, for their flexible operating conditions and inherent safety characteristics.In response, the U.S.Nuclear Regulatory Commission staff is moving forward with development of the 10 CFR Part 53 rulemaking, which is a more risk-informed, technology-agnostic framework for licensing and regulating such new designs.The nuclear industry response to this regulatory initiative resulted in the technical report NEI 18-04 Revision 1, which provides an implementation roadmap of the risk-informed approach when defining the safety case for a new plant design.The implementation of this safety case may be a non-trivial exercise for an actual reactor design.This paper provides a demonstration of performing such analysis for a representative advanced reactor.Public information from the General Atomics High-Temperature Gas Reactor design was considered in this demonstration.The analysis workflow was facilitated with the FPoliSolutions' proprietary Risk-Informed System Engineering (RISE) digital platform, a product that was presented in previous publications.RISE is one application of FPoli's enterprise digital platform, called FPoliAAP, which was created to facilitate orchestration of complex workflows leveraging recent technologies developed at national laboratories such as INL's RAVEN and EMRALD frameworks.The analysis described in the paper includes the selection and classifications of events, the integration of probabilistic risk analysis artifacts, and event modeling simulations for consequence evaluations.The results are then used for SSCs safety classification and, ultimately, a synthesis of the safety case for the design in line with the frequency-consequence targets as presented in NEI 18-04.The purpose of the analysis, as framed in RISE, is to readily produce outputs and views which aids users and regulators in making risk-informed decisions to demonstrate their plant safety case consistent with RG 1.203, RG 1.233 and 10 CFR Part 53.