Westinghouse Approach to Flexible Power Operation in PWRs

摘要

Nuclear plants throughout the world areexperiencing a strong imperative to implement FlexiblePower Operation (FPO), mainly as a result of thesignificant increase in solar and wind generationcapacity. The load cycles associated with renewable aredifferent from the historic demand cycles assumed in theoriginal plant design. The transition to FPO may havemany effects on the plant and on the fuel and NuclearSteam supply system. Westinghouse has developed anefficient approach to addressing the NSSS issues relatedto FPO that identifies which NSSS related confirmationsare required prior to FPO operation as well as otheractivities that should be performed in FPO will continuefor a long period.This Westinghouse approach for accommodating theimpact of FPO on the fuel is based on the Core OperatingGuidelines (COG) which Westinghouse has issued toprovide the reactor operator with guidance on how thecore should be operated during load follow and extendedreduced power operation in order to maintain operationwithin the current operating limits and safety analysis.The COG also provides specific guidance on when furtheranalysis or actions may be necessary. If operation occurswithin the COG then the impact of FPO on the fuel andreload safety analysis is small and can be easilyaccommodated.The Westinghouse approach for the other NSSScomponents involves specific analysis to assess changesto the original plant design analysis resulting from poweruprates, plant lifetime extension, and other plantmodifications. Margin in key parameters are quantifiedand used to determine how much FPO can beaccommodated within the current plant design analysis.The Westinghouse approach to accommodating FPOalso relies on the identification and monitoring ofparameters that serve as indicators of the key impacts ofFPO. Westinghouse has developed the capability foronline monitoring of these key parameters. Examplesinclude the BEACON code which has the ability toperform continuous on-line monitoring of both powerdistribution and margin to PCI limits based on in-coredetectors. And the WESTEMS system monitors fatigueat specific locations, giving plant operators crucialinformation about the condition and potential lifespan ofplant components. Threshold values are also providedfor these key parameters that combined with the online monitoring capability allow the plant operator to predictwhen additional assessments, inspections, or changes inoperating strategy might be necessary.