Optimizationofseed-blankettypefuelassemblyforreduced-moderationwaterreactorOriginalResearchArticle

waterreactor(RMWR)withtheseed-blankettypefuelassemblestoachieveahighconversionratio,negativevoidreactivitycoefficientandahighburnupbyusingMOXfuel.Fromtheviewpointofreactorsafetyanalysis,thefueltemperaturecoefficientswerealsostudied. Fromtheresultoftheburnupcalculation,ithasbeenseenthatratioof40–50%ofouterblanketinaseed-blanketassemblygiveshigherconversionratiocomparedtotheothercombinationofseed-blanketassembly.Andtherecommendednumberof(seed+blanket)layersis20,inwhichthenumberofseed(S)layersis15(S15)andblanket(B)layersis5(B5).Itwasfoundthattheconversionratioofseed-blanketassemblydecreases,whentheyarearrangedlookslikeaflowershape(Hanagara). Bytheoptimizationofdifferentparameters,S15B5fuelassemblywiththeheightofseedof1000mm×2,internalblanketof150mmandaxialblanketof400mm×2isrecommendedforareactorofhighconversionratio.Inthisassembly,thegapofseedfuelrodis1.0mmandblanketfuelrodis0.4mm.InS15B5assembly,theconversionratiois1.0andtheburnupis38.18GWd/tin(seed+internalblanket+outerblanket)region.However,theburnupis57.45GWd/tin(seed+internalblanket)region.Thecyclelengthofthecoreis16.46effectivefullpowerinmonth(EFPM)bysixbatchesandtheenrichmentoffissilePuis14.64wt.%.Thevoidcoefficientis+21.82pcm/%void,however,itisexpectedthatthevoidcoefficientwillbenegativeiftheradialneutronleakageistakenintoaccountinthecalculation. ItisalsopossibletouseS15B5fuelassemblyasahighburnupreactor45GWd/tin(seed+internalblanket+outerblanket)region,however,itisnecessarytodecreasetheheightofseedto500mm×2toimprovethevoidcoefficient.Inthisreactor,theconversionratiois0.97andvoidcoefficientis+20.81pcm/%void.Thefueltemperaturecoefficientisnegativeforbothofcases.