Abstract :
Theresultsofvariousaccidentscenariosimulationsforthetwomajormodularhightemperaturegas-cooledreactor(HTGR)variants(prismaticandpebblebedcores)arepresented.Sensitivitystudiescanhelptoquantifytheuncertaintyrangesofthepredictedoutcomesforvariationsinsomeofthemorecrucialsystemparameters,aswellasforoccurrencesofequipmentand/oroperatorfailuresorerrors.Inaddition,sensitivitystudiescanguidefurthereffortsinimprovingthedesignanddeterminingwheremore(orless)R&Disappropriate.BothofthemodularHTGRdesignsstudied–the400-MW(t)pebblebedmodularreactor(PBMR,pebble)andthe600-MW(t)gas-turbinemodularheliumreactor(GT-MHR,prismatic)–showexcellentaccidentpreventionandmitigationcapabilitiesbecauseoftheirinherentpassivesafetyfeatures.Thelargethermalmarginsbetweenoperatingand“potentialdamage”temperatures,alongwiththetypicallyveryslowaccidentresponsetimes(approximatedaystoreachpeaktemperatures),tendtoreduceconcernsaboutuncertaintiesinthesimulationmodels,theinitiatingevents,andtheequipmentandoperatorresponses.
