VoidinducedreactivityinamixedMTRcoreOriginalResearchArticle

Experimentsinresearchreactorsoftenposethenecessityofvoidinsertioninseveralcorepositions.Also,sub-cooledboilingmayintroducefluctuatingquantitiesofbubbles.Thereactivitychangeanditseffectonthesafetyareimportantmattersthatmustbeassessed.Inthepresentwork,thereactivityinducedbyvoidinsertioninvariouslocationsofthepooltype,mixed(highandlowenrichmenturaniumfuel)coreoftheGreekResearchReactor,wasmeasured.Theinducedreactivityduetothevoidintroductionwasdeterminedbymeasuringthereactorperiod.Themeasuredreactivitywasfoundtobestronglyspace-dependent.ResultsobtainedwiththediffusioncodeCITATIONwerefoundingoodagreementwiththeexperiment.Conclusionsonthebestutilizationofdiffusioncodeswhencalculatinglocalvoideffectsonreactivity,inregionsofsteepfluxgradients,weredrawn.Thesensitivityofthelocalvoidreactivitytothecoreposition,aswellastothefuelenrichmentandburn-upwasexamined.Ananalyticalpointreactormodelwithtwoneutronenergygroupswasdeveloped,toinvestigatequalitativelytheeffectsofparametersrelatedtovoidreactivity.Theanalyticalresultswerefoundingoodqualitativeagreementwithmeasurementsandnumericalsimulations.