NucleardesignOriginalResearchArticle

Thehigh-temperatureengineeringtestreactor(HTTR)hasbeendesignedforanoutlettemperatureof950°C.Thatisthehighesttemperatureintheworldforablock-typehigh-temperaturegas-cooledreactor(HTGR).Thefunctionsofthereactivitycontrolsystemaredeterminedconsideringtheoperationalconditions,andthereactivitybalanceisplannedsothatthedesignrequirementsarefullysatisfied.Moreover,thereactivitycoefficientsareevaluatedtoconfirmthesafetycharacteristicsofthereactor.Thepowerdistributioninthecorewasoptimizedbychangingtheuraniumenrichmenttomaintainthefueltemperatureatlessthanthelimit(1600°C).Deviationfromtheoptimizeddistributionduetotheburnupoffissilematerialswasavoidedbyflatteningtime-dependentchangesinlocalreactivities.Flatteningwasachievedbyoptimizingthespecificationsoftheburnablepoisons. Theoriginalnucleardesignmodelhadtobemodifiedbasedonthefirstcriticalexperiments.TheMonteCarlocodeMVPwasalsousedtopredictcriticalityoftheinitialcore.Thepredictedexcessreactivitiesarenowingoodagreementwiththeexperimentalresults.