PowerpeakingsinmixedTRIGAcores

ModernMonte–Carlocodes(e.g.MCNP)allowcalculationofthepowerdensitydistributionin3Dgeometryassumingdetailedgeometrywithoutunit-cellhomogenization.Thepowerdensitydistribution(anditsmaximumvalue—thepeaking)canbecalculated‘point-wise’withtheresolutionofapproximately1mm.ResultsofthedetailedpowerdensitydistributioncalculatedbyMCNParepresentedfor250kWTRIGAMarkIIreactor,assumingvariousrealisticandhypotheticalcore-loadingpatternswithfocusonthemixedcores.Combinationsof8.5w/o,12w/o,20w/oand30w/olow-enriched(20%)freshTRIGAfuelrodsaresystematicallytreatedinthemixedcores.Thepowerpeakingfactorvalueandpositionstronglydependsonthecoreconfiguration.Powerpeakingsareusuallyfoundinfuelrodswithhigheruraniumcontentespeciallyiftheyareinsertednearthecorecentre.Theresultsareconservativeandcanbeappliedinplanningrealisticmixedcore-loadingpatterns.