Author/Authors :
JeffreyC.King، نويسنده , , MohamedS.El-Genk، نويسنده ,
Abstract :
Compact,fastspectrum,nuclearreactorsarebeingconsideredtosupportNASAʹsfuturespaceexplorationsometimeinthenextdecade.Inordertosecurelaunchapproval,thesereactorsshouldremainsufficientlysubcriticalwhensubmergedinseawaterorwetsandandsubsequentlyflooded,followingalaunchabortaccident.Insuchanaccident,theneutronspectruminthereactoristhermalized,typicallyincreasingreactivity,andpotentiallymakingthereactorsupercritical.Incorporating“SpectralShiftAbsorbers”(orSSAs),whichhavesignificantlyhigherabsorptioncross-sectionsforthermalversusfastneutrons,couldoffsetthereactivityincrease.Ithasalwaysbeentheassertionthattheworst-casesubmersionaccidentinvolvesafullyfloodedreactor;however,thisworkshowsthat,dependingonthetypeandamountofSSAinthereactor,asubmergedbutunfloodedreactorcouldbemorereactive.AscreeningoftheexistingnucleardatabaseforpotentialSSAsyielded28elementsandnuclides,whichareexaminedindetailasadditivestoarepresentativehomogenousspacereactorcorebyvaryingtheSSA-to-U235atomratio.TheeffectofplacingathincoatingofdifferentSSAmaterialsontheoutsidesurfaceofthereactorcoreisalsoinvestigated.NineSSAs(boron-10,cadmium,cadmium-113,samarium-149,europium-151,gadolinium,gadolinium-155,gadolinium-157,andiridium)arerecommendedforfurtherconsiderationinactualspacereactordesigns.
