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THEFIRSTNUCLEARERA(BYALVINWEINBERG, OAKRIDGE)
SUB-TITLED:THELIFEANDTIMESOFATECHNOLOGICALFIXER
REVIEWEDBY
RICHARD STEEVES
TEACONFERENCE,OCTOBER1,2019
ALVINWEINBERG:LIVED1915– 2005:EARLYDAYS(1939-1943)
• Alvin’sPhD(UniversityofChicago)useddiffusiontheorytounderstandneurophysiology,butwithWWIIstarting,hewasaskedtoapplyhisdiffusionskillstoseeifberylliumwouldbeagoodmoderatorforachainreactor.(Thenhisboss,CarlEckart,suddenlytookoffforCalifornia!)
• EugeneWignerarrivedinearly1942,andinformedAlvinthattherealpurposeoftheprojectwastocreateplutonium(239Pu)foruseinanatomicbomb,aswellastostudythenatureofthechainreaction.
• Bothmenworkedoutatheoryofhowthechainreactioncanbeachieved,andthebestwaystostudyandanalyzeit.
FERMI’SPIONEERS:- PHOTOOFEUGENEWIGNER
• EugeneWigner,Nobellaureate(‘63)foratomicnucleartheory;lived1902– 95à
• ArthurCompton,Nobellaureate(‘27)forComptoneffect.• LeoSzilard,conceivedthenuclearchainreaction(‘33).• WalterZinn,calculatedpilesizeforreactors.• BobChristy,helpedWeinbergwithuraniumlatticedesign.• GaleYoung,aclosecollaboratorwithWigner.• (EdwardTeller&RobertOppenheimervisitedoccasionally.)
HOWCANWEMAKEANUCLEARCHAINREACTION?• BACKGROUND:
• Ofthe2isotopes,238Uand235U,only235Ufissionswithslowneutrons;bothfissionwithfastneutrons.Immediatelyafterthefirstfissioninablockofsoliduranium,neutronsareslowedbycollisionswith238U,andareremovedfromthe“chain”aseach238Uisconvertedintoplutonium(239Pu).Thus,tomaintainachainreaction,onemustfirst:
• 1)Slowtheneutronsoffissionto“thermal”energylevelswitha“moderator”,sotheneutronscanfissiontheremaining235Uwithhighprobability.
• 2)Dispersetheuraniumatomswithinthemoderatorsuchthattheneutronsareslowedimmediately.(ImagineUnucleiasraisinsinabigcakeofgraphitemoderator.)
• 3)Makethepile(ofdisperseduraniumlumps)largeenoughsotheneutronsescapingfromthesurfaceofthepilearejustbalancedbytheneutronsproducedbythefissioning235Unucleiinsidethepile.Whenthetwoareinbalance,thepileis“critical”.
ANALYSISOFAFISSIONCHAINREACTION
• Ifwemakethepilelargerthanidealforcriticality,thenthereactorissaidtobesuper-critical,andthechainreaction“runsaway”.
• Ifthepileissmaller,subcritical,thechainreactiondwindlesanddies.
• Themultiplicationconstant,K,=1forperfectchainreaction,althoughtoobtainaworkingpileofpracticalsize,kmustbe>1by3- 4%.
COMINGBACKFROMTHEORY TOSOMEHISTORY:
• Backin1941thiswaswellunderstoodbyFermiandWigner,butnotbyWeinberg,who,evenwhenheunderstoodit,doubteditwasfeasibletoachieve(ratherlikeexceedingthespeedoflight).
• Fermiwasonlyabletoobtainak valueof0.87inOct.1941,soheimprovedhis“pile”(Staggsquashcourt)byconducting31experimentsin1942-43.Aftermuchrefinementofthepilelattice,andremovalofborontracesfromthegraphite,thechainreactionwasfirstdemonstratedonDec.2,1942.
• (Sincethesquashcourtwassmall,only50peoplecouldbeinvited;sinceWeinbergrankedat54th ,hewasregretfullynotamongthem.)
THEW(WATER)REACTORSTOMAKEPLUTONIUM(PU)
• DesignswerebeguninApril1942(8monthsbeforek=1)formakingPu(forbombs),coolingmaterialwasdiscussedatlength,andWignerfinallychosewater.PlansweresubmittedinJan.1943;the500MWreactorwasbuiltinHanford WA(byDupont)toproduce500gm/day.• Inretrospect,WeinberglikenedWigner’screationofacomplexreactortoMozart’scomposingapianoconcerto;Wignermayhavetaken4months>Mozart’sfewdays,butthecomplexitywasenormous.Heviewedeveryday’sdelayformakingthebombasagifttotheNazis.
CONCEPTOFTHEBREEDER REACTOR
• OnApril26,1944FermiandLeoSzilardoutlinedideasforfastreactors,andnextdaySzilardcameupwiththename“breeders”,whichproducedmorePlutoniumthantheyconsumed.• Backthentheybelievedthatbreederswereessentialforfutureenergy,giventheirassumptionthatUreserves(fromtheBelgianCongo)wereonlyafewthousandtons.
PRESSURIZEDWATERREACTORSBEGANIN1944.WIGNER&WEINBERGà
• Experimentswithnon-enrichedUinlightwaterrevealedthatk didn’tquitereach1,eveninitsbestlatticeconfiguration.WeinbergreasonedthattheycouldmakemorePu(forbombs)byusinglow-enricheduranium(LEU),moderatedandcooledwithpressurized lightwater.Thesetwoimprovementsbecamethestandardforbuildingfuturelightwaterreactors(LWRs).
POLITICSOFTHEBOMB:LEOSZILARD’SCAMPAIGN
• Inearly1940Leoproposedthatallpapersonfissionbewithheldfrompublication.
• Byearly1945weheardofgreatprogressinLosAlamosonbombdesign.Leowasconvincedthatbombingcivilianswouldplaceamoralonusonus,notunlikethatbornebytheGermans,whohadusedpoisongasinWWI.
• Hethereforeledattemptsbyscientiststomobilizeagainstitsuse.*ArthurComptoncounteredthiswithspecificchoicesandadvice.
• ___________________________________________• *See:APerilandaHope:TheScientificMovementinAmerica,1945-7,byAliceSmith
THEMOVETOOAKRIDGE– MAY1945
• Clinton,partofArthurCompton’sMetallurgicalLab,wasasiblingofhisotherbranch,ArgonneLab.RunbyDupont andtheCorpsofEngineers,itsatmos-phere wasverydifferentfromthatofauniversity.
• ThisX-10researchreactor wasbuiltin9months,goingcriticalonNov.4,1943,andeventullydeveloping1MW.Sixother,verydifferentresearchreactorswerebuilthereoverthenextfewdecades.
RICKOVERANDTHENAUTILUS
• CaptainHymanRickoverfirstcametoORNLafterWWIItoattendWeinberg’scourseonreactortheory.Yearslater,when“Rick”andhisnavalteamreturnedtodecideonacoolantforhisnuclearsubmarinereactor,theyhadtobepersuadedtoaccepttheideasofcompactnessandsimplicity(boilingwater)overefficiency(hotsodium).
• PhotosshowtheNautilusreactor(above)andthesubmarineduringseatrials.à
ALVINDIRECTSTHEOAKRIDGENATIONALLAB(ORNL)1948- 1974
• AlvinWeinbergacceptedthepositionaftermanyothershadwalkedaway.Thiswasformanyreasons,partlybecausehelovedtheregion,butmostlybecausehewasabletoappreciatetheuniquescientificcontributionsbytheORNLtotheutilizationofneutronsfromhigh-powerresearchreactors.• Intheearlydaystheyexploredallsortsofpowerreactors,comparingtheadvantagesanddisadvantagesofeachtype.Alvincalculatedthattherewere~1,000possiblewaysofcombiningvariousfuels,coolantsandmoderators.Butoncepressurizedwatergainedafoothold,otherpossibilitieswerepreemptedasbeingtooexpensive.
NUCLEARENERGYFORPROPULSIONOFAIRCRAFT- NEPA
• Thegoal(demand)ofthemilitarywastoflyonnuclearpowerfordays(orweeks)withoutevertouchingtheground.(ICBMswereonlyadreambackthen.)• Thiswaswishfulthinking,fornuclearreactorsareutterlyunsuitableforthis.Thesmallestreactorwouldweigh50tons,andshieldingthecrewwouldhaveaddedanother100tons.
AQUEOUSHOMOGENEOUSREACTORS– 4ADVANTAGES• 1.Solidfuelelementsareeliminated,reducingcomplexityandcomplications.• 2.Gaseousfissionproduct(135Xe),afission“poison”,canberemovedeasily.• 3.Solidfissionproductscanberemovedcontinuouslywithoutshutdown.• 4Controlrodsarenotneeded,reducingcomplexityandpossiblecatastrophe.
• AHRs:- 2DISADVANTAGES…!• 1.Theentirecirculatingsystem(pumps,heatexchangers)becomesradioactive,somanualrepairswouldbehazardoustopersonnel.
• 2.Controloffuelinventorywouldbedifficult,especiallyiffuelprecipitated;ifitsegregatedinonespot,itmightover-heatthere.
MOLTENSALTSHAVE3BIGADVANTAGESOVEROTHER HOMOGENEOUSAQUEOUSSYSTEMS
• 1.ThethermodynamicstabilityoffluoridesaltsofU&Th allowsthemtobeinherentlycompatiblewithstainlesssteelpipes,withoutusingmetaloxidesforpipeprotection.
• 2.Thesesaltsboilatsuchhightemps(1700ºC),theycanoperateatnormalpressures,insharpcontrastwithwater(whichneeds67Xatmospheric).
• 3.Thoriumaswellasuraniumdissolvesinmoltenfluorides,whichenhancesversatility.NoteAlvinàatthecontrols.
MOLTENSALTREACTORS ARESAFE.
THETHORIUMTHERMALBREEDERWASLEFTTODIE
• Alvinbecameobsessedwiththeideathathumankind’swholefuturedependedonthebreeder.Hepublishedextensively(1958– 59)andtravelledaroundtheworld,givingoptimisticlectures.A1962AECreportfeaturedthethermal breeder,butinspiteofallthat,crucialsupportforitsfurtherdevelopmentwasneverprovided.WHY?
• 1.Thefast breederarrivedfirst,andwasgivenpreliminarysupport.• 2.Themolten-salttechnologyisentirelydifferentfromotherreactors.MiltonShaw(directorofreactordevelopmentatAEC)thoughtso.
ISNUCLEARPOWERECONOMICALLYFEASIBLE?
• AsLWRsincreasedinnumberandsize,àGEandothers(Westinghouse)offeredthematpriceslowerthancoalplantprices.
• Later,however,theyfoundthattheeconomicscalinglawofbigger-is-cheaperdidnotapply,especiallyasextrasafetyfeatureswereadded,soconstructioncostsmounted.
NUMBEROF LIGHTWATERREACTORS(LWRS)INCREASED
• AsLWRswerebuiltrapidlyinUSAàwherefossilfuelsareplentiful.TheywereacceptedevenmoreinEurope,wherefossilfuelsarelessfrequent.
• By1972over400largenuclearreactorswereeitheroperating,inconstructionoronorderaroundtheworld.
NUCLEARREALITY:THEFAUSTIAN BARGAIN
• Nuclearrealitybecamefarlessutopianasthe1960’sà 1970.AswarnedbyFermibackin1944:• 1)Nuclearreactorscreateradioactivityonanenormousscale.Ifareactorfailedcatastrophically,radioactivitywouldbespreadwidely.• 2)Breedersproducematerialsthatcanbeweaponized.Iffissilematerialweredivertedclandestinely,theworldmightbethreatenedbynuclearmalevolence.• Alvin’smostinfluentialcriticswereRalphNaderandlater,HenryKendalloftheUnionofConcernedScientists(UCS).
THEWEAPONSCONNECTION
• Ina1985book,writtenwithM.Alonzo,AlvinexplainsthatacountrybentontheclandestineproductionofnuclearbombswouldNOTchooseFermi’srouteofextractingplutoniumfromapowerreactor.(Iraq,Israel,PakistanandSouthAfricaobtainedtheirbombmaterialslongbeforetheyhadpowerreactors.)• Whilethisdoesnotprovethatacountrywithaflourishingnuclearpowerindustrycouldn’tdecidetousethattechnologytoweaponize,itbegsthequestion:Isthisworrynecessary,orwasitjustmanufactured?
WASTEDISPOSAL
• Wastesposeamuchsmallerhazardthanreactorsdo.Solidifiedwastes,aftercoolingoutsidefordecades,producerelativelylittleenergy.Ifwaterreachedwastepackages,radioactivitycouldbeleachedanddispersedtoalargepopulation,butonlyslowly.Ifatransportaccidentoccurred,largerdoesofradiationcouldreachasmallpopulation,buttheriskoflargedosesofradiationtolargenumbersofpeopleisprecludedbythermodynamics.• Meanwhile,AustralianresearchershaveinventedSynroc,asyntheticceramicthatisresistanttoattackbygroundwater,andSwedenisusingcoppercanisterstoencapsulatewasteinstablestrata.
COULDWEHAVEDONEBETTER?ALVINSUGGESTEDTHESE4IDEASFORTHEFUTURE.
• 1.Putallreactorsonrelativelyfewsites(~100inUSA).Wehave80acceptablesitesnow,soweneedonly20more.• 2.Increasesecurityatallthesesitestoavoiddiversionorterrorism.• 3.Professionalizeallnuclearoperators,similartoairlinepilots.• 4.Reorganizetheutilityindustrybyseparatingnucleargeneration ofelectricityfromitsdistribution.Theformershouldbeinthehandsofaverysingle,powerfulentity,possiblythegovernment.
KEY“STRENGTHS”PERTAININGTOTHORIUM
• 1.Thecapacityformorecompletefission(higherburnups);hence,less“waste”.• 2.Highermeltingtemperaturesandimprovedthermalcharacteristics.• 3.LessproductionofPuandminoractinides,allowingThoriun tobearobustfertilematrixforconsumingsurplusPufromusedfuelinventories.
• 4.Thecapacitytoreachhigherconversion(breeding)ratiosinthermalandepithermalneutronspectra.
• 5.Canbeafueladditivetouraniumoxide,improvingoperationandsafety.• 6.Thesesynergiescombinetoallowmoreefficientuseoffuelsmoresafely,andthisisallindependentofusingthemoltensalttechnology.
ALVINWEINBERG’SLASTINGWORDSOF
WISDOM
HEREAREMYWORDSOFWISDOM:TAKECAREOFTHEELDERLYASWELLASOURBABIES!
