Technical Report on Preliminary Methodology for Enhancing Risk Monitors with Integrated Equipment Condition Assessment

Abstract

Executive SummaryAdvanced small modular reactors (AdvSMRs) may provide a longer-term alternative to traditional light-water reactors and SMRs based on integral pressurized water reactor concepts currently being considered. AdvSMRs are designed to incorporate multiple modules (which may or may not have shared components and structures) at a single location, comprising a full "plant." AdvSMR operation differs fundamentally from full-size plants because the smaller plants may be used for load-following or peakdemand power generation, instead of baseload generation. AdvSMRs are also being considered for dualuse, where process heat would be used for both electricity generation and another purpose such as hydrogen production or water desalination, shown in Figure Enhancing affordability of AdvSMRs will be critical to ensuring wider deployment. Although some of the loss of economies of scale inherent to AdvSMRs can be recovered, controllable day-to-day costs of AdvSMRs will be dominated by operation and maintenance (O&M) costs.Technologies that help characterize real-time risk are important to controlling O&M costs and improving affordability of AdvSMRs. Given the possibility of frequently changing plant configurations in AdvSMRs, advanced plant configuration information, equipment condition information, and risk monitors are needed to support real-time decisions on O&M. For this purpose, approaches are needed to integrate these three elements in a manner that provides a measure of risk that is customized for each AdvSMR unit, and accounts for the specific operational history of the unit. By integrating technologies for condition assessment with risk monitors, asset optimization and improved economics of AdvSMRs may be enabled by:• Maximizing generation by assessing the potential impact of taking key components offline for testing or maintenance, iv• Supporting reduced O&M staff by aiding in optimization of O&M planning (specifically by assessing the contribution of individual components to changes in risk and using this information for scheduling maintenance activities),• Enabling real-time decisions on stress-relief for risk-significant equipment susceptible to degradation and damage, and• Supporting potential remote siting by providing early warning of potential increases in plant risk.This report describes research results from an initial methodology for such enhanced risk monitors (ERMs) that integrate real-time information about equipment condition and probability of failure (POF) into risk monitors to provide an assessment of dynamic risk as plant equipment ages. This integration occurs at the level of the POF within risk monitors.Risk monitors extend probabilistic risk assessment (PRA) frameworks by incorporating the actual and dynamic plant configuration (e.g., equipment availability, operating regimes, and environmental conditions) into the risk assessment. PRA is itself a systematic safety analysis methodology that follows four steps: identify undesirable consequences (e.g., reactor unavailability, core da...

Local-Level Prognostics Health Management Systems Framework for Passive AdvSMR Components. Interim Report

“…More recently, time-based POF values derived from operating experience and traditional reliability analysis have been used (Vesely and Wolford 1988;Arjas and Holmberg 1995); however, these are usually not specific to the component. Ramuhalli et al (2013b) discuss the potential for integrating predicted POF values from PHM systems with risk monitors to obtain a realistic assessment of dynamic risk that is unit-specific and accounts for the operational history of the component.…”

“…A simplified-model AdvSMR (power block) design (Appendix A) is used as the context for the research on the development of a framework for the PHM. (The same simplified design is also used as the context for the research into enhanced risk monitors (Ramuhalli et al 2013b;, and its use here provides the unifying theme for future integration of the PHM methodology into enhanced risk monitors for condition-based risk assessment). This hypothetical design is intended to be prototypical and resembles proposed liquid-metal-cooled designs.…”

“…The condition indicator is then projected to future times using appropriate prognostic algorithms (Coble et al 2012b; to estimate POF distributions for each key SSC at some point in the future. These estimated POF distributions may then be used by enhanced risk monitors (Ramuhalli et al 2013b) to provide a more accurate assessment of the dynamic risk. The ability to predict (or estimate for future times) the POF based on equipment condition assessments and incorporate these in enhanced risk monitors (ERMs) may also help compensate for a relative lack of knowledge about the long-term component behavior of some materials and components that are being proposed for AdvSMRs.…”

“…The example design is defined to provide a simple level of abstraction but contains enough resolution and specific design elements to inform the development of a PRA model that, when quantified, produces a cogent set of results in support of PHM systems for AdvSMRs. The choice of this simplified design also enables the future integration of the results of the PHM methodology with enhanced risk monitors (Ramuhalli et al 2013b;).…”

“…This is followed by the technical assumptions that bound the research described in the rest of this document. Additional details of AdvSMR concepts and likely O&M approaches are provided in the previous reports in this series associated with AdvSMR prognostics and enhanced risk monitor research (Coble et al 2013;Ramuhalli et al 2013b;).…”