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This chapter recounts briefly the outstanding atomic bomb project contributions which were made by the National Bureau of Standards up to the termination of the Manhattan district on 31 December 1946.
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1. General. Undoubtedly the most spectacular vork undertaken b7 the obscure lhe ini U&l and cri tioal two 7ear1 during which the ma.Jor program or '1le veapon began. Uie purpoae of this chapter to recount briefly the outatanding e.tollic Standard• up to the temin.ntion of the Manhattan Dhtrlct on 31 December
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~boratory, funds to the extent of $100,000 were made available to the proJect at a time when the7 were moat urgently needed. These funds were u.ed mainly for the studT of different aethods of aeparating the iaotopes. Among them was the method of thermal diffuaion throμgh the pilot plant •tace at the Naval Reaearcb Laboratory, end on the aepara.Uen of the uranima laoM>pea b7 caaeoua cllffuaion throuch a poroU11 ..mbrane, vhich, likewise, eventually led to the conatruction and operaUon of an enoraoua d.iftuaion plant at Oak llldce. fhe deTelopment of a centrifugal method for eeparatlnt,: the iaotopea wea undertaken b)' J. W. Beams at the University ot firginia. That method vaa carried In Jm:le,l9lfo,Pre1ident BooaeTelt eatabliahed the lational Defenae fidential work. At that time the Uranium (S-1) Section waa reorgani1ed
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ae.tter ot great uncertainty. 7et upon this the auccese ot the whole proJect rested. rort7 tone of graphite and seven tons ot uranium oxide vere supplied to fel'llli at Columbia tor use ln a further attack on this llke uranlua 235 udergoH thdon when 1 t aa;p\ures a alow aeutrOD.. be separated from the parent aaaa b7 chemical methods. aade, and, on the bade ot the llaUonal .lcadenw ot Sciencee 1 reports,
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presented the request of h1r. section tor an allotment of $267,000, wi\h the statement that ~uch l~r~er expendlturea would probably aoon be rements.l vork went forward at an lncrellsed tempo. In lovember 1941 Bu.eh, after rftYlewing the further advances that President and h11 ad.Yiaora, decided that the Uae had no111 come tor an ihe hokpea, and on the all laportant proble• ot deYelopt.ng sui kble porous aembranes that would not corrode and become cloged. through t!le Uon in \he producUon of plutonium. at Oolwnbia under lend. and at
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Chicago under Alliaon, Yan continued Ullder CoD'pton'• direction at the UniTersU7 ot Chicago. It was here that tile cha1n-reactton was first demonstrhttd by Fermi in 6 «raph1te-ur6111um pile in December 1942. B7 July, 1942, it appeared that the tln~l tntenoive work on the Committee, consiet111€ of Conant. chairman, Brlcgs, Compton, Lawrence, the recenU7 tonaed Manhat~ Dhtrict proJect, vho vag charged with the the poillt where it could. 'be taken over ad.YCA\ageouel1 b)T the Manhattan The toregciag h pnseated 1n •omewha' greawr 4eWl la look 1 1 lnt.J'Jll&Uon h repeated in t.hh chapter, bovner, in order to emphaabe the iapor\ant roll enacted by the Direc,or of the Batlonal Bureau of Bureau atatf were engaged on the atomic bomb proJect. Some of its lead.lac
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and Loi Alamoa Labore.torie1 at the request ot the 11&1' Department. procedure vaa dneloped for produc1- graph! te practically free fJ'oa boron. fhHe oontr1buUon1 vere of great Talue to the proJect, becauae method vae deTeloped •o meaaure the change in the rela\1Te abundance a controllable chain reac\ion tor the prod1a0t1on of plu•oa1111D. It vae known that lapurltiea vb1oh JliPt be preaent in ~. graphite or uranium would capture eome of the neutrone generated by t1edon of the uranium
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suataining reaction from occurring in a uraniwn-«raph1te pile. 'l'hu1 had aever been eerio\1817 affected by the impurities that aov &HUiied Hence, the eata.bli1hllent ot a reliable method tor the 4etermla~t1on ot
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found that the 1urtace ot the t111i1hed graphite bare contained more boron calcium. In Jue, 1941, some of the p1eoes ot metal t.hua obtained were trom thla work wae ~at ~e melting point ot uranium va1 lover )J' at
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boron con1ien' of iihh 11eW •as ioo high, but it could be largely ceciurH tor pur1ff1~ them. Dthninatlona of boron were aov 'Mlag te\erminatlon of rare earths in t.he lapun oxid.e were ot eepeclal a me\hod tor ob\aia.1Ji€ purer black oxide wae foud which con1i1'ed.
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$t!J.'>ffof an acld leach of the material. The B3S contracbd tor the treataent of future ahlpmen'8 and the working over of some of the older ahlpmante b7 this aethod. As a reaul t of the exparlaental work at the IBS on the pur1t1caUon of uranium oxide and on the di•tlllation of calcium, it vas e~ident tn oxide could be obte.1».ed fro11 crude uranium oxide and from pUchblende procedure for ~e finel. purification of nll the uranium 1ubsequ.entl7 wiecl in the plles.
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District assumed respons1b111\7 tor procurement, the anoJ.yi1cal work In 7ebrwar, 1943, vhen the Menhat\an District set up a program tor anal7\ioal control ot materials uaed 1n the piles. 1or example, in
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All .further examples of the d1v•rse na.ture of the problems that euae wa be returned to the orlgln61 ovners in the re1idues left e.f ter remoTal section for check~ aethods of deterlli.naUon of radium.
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teats of the purity of several urwiiurJ oxide aamplea were made bt DeTelopment, the Tolume of testing increaead ~nd ~· aumplea then eubmi tted included a varlet,- of uranium compound.a and other ma.teriale CNI. be obtained. For m~ lmpuri'T elemente, concentrations of a fev
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are aeparated trom \he uraniwa and then determined. apec,rographlcall7. uranlwa vs.a 4eTeloped. at the Jational Bureau of Standarda, and vaa deacrlpl'OYS.4.ed tor the de\eratnatlon ot boron clown \o a limit of 0.1 part. per eleMab llov d.e\eralaed. '7 the ut.hod. are Ag, Al., Al, Au, 1 1 la, le, eleaenta at concent.raUone ran«lng trom a few part• per million for •oat ot the element.•, down to one part in 10<>-alllion ln the caee of
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boron. The other labc.ratoriec on the project and applied in the nru:;l;;:sh of thousandR of e1U:1plea iit the Buren.u during the years 1943-45. impurity element£ to vhich the oe.rr1e~dtst1llatlon method did not appl7. 11. remarkable limit wne achieved. Far exemple, the rare-earth method ot one part in 250-1:11.lllon parts ot ura.nlu.
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mnterlal in the hbtory of an1'-lyUOl.'.1 chemhtey. lurgy of uranium lnveeU~.ted at the BU!"esu included the deTelopment of tlon of density and. hardne•1, 4eYelepment of prooeduree for preparlnt; (1) Mel Ung and eaetlni' uranhunt In th~ early 1te;gee of the project, ut1111s.U<1n ot uranium required the d"'elo:;;naent of methodo for l11T•1HgBUon of \he meltlng of vantum wee initiated at the metal molds, ap. well ae graphite ~ol4e, could be uted for casting ura.n1ua;
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and (c) development of a procedure for ct:..1t1ng bars from each of which two or more S-lach duge tor the pile could be fabricated. ~· The oaai -art were euperior to extruded rod, in r.gard to interior 4etecte, ancl adoption of the oa.ti.Qg process avoided the difficult extruaion process. (2) Development of met.bode tor tabrlcatlng uraniwnz The hot and cold working propertlet of uranl.111:1 were inve•tigated and prooedures Hot rolllllc, at '8mpe:r&.ture1 near the kp of the alpht:. rellge, ..,...._ beoauH of the amout of oxlde rolled. 111.. Cold. rolling vi\h frequent .Ba.re ura\lliwn could aot be drawn 1ati•factor1l1 with uq of the oil copper ae a lu'br1c8lli, bJ eleotrodepoeltlag oopper on the cleaned wire,
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When the anodic cleanimg and the platiDg were conduc\ed ln different bathe, tllm torme.tion d.urlng exposure to the air vhlle transferring trem hee1on of the plating. A procedure vaa 4eYeloped tor cleaning anodicall7 f. Pbf'elcal and Mechanical Properties of UrADiu. Much of the inforaation ln the llteratUl'e on 'h• properties ot uranium vaa inaccurate point 4etera1utions were later ude 'b7 the Heat and Pover D1Y1don on
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znel ting point of uranium, with 5 par ta per 111llion of carbon9 6o pari1 per million of iron. 20 pP.r's per million ot o~gen, and lesser e.moun\e mom~t of \he odd hotope. It vat: mown., however, that \he emiedon complex. and does not at a.11 reoemble the 1pectr£ of chromium, molybdenl&lll, cation of the uraniwn 1pectra..
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A aeparatlon wae affected of the 11ne1 emlt\ed b7 neutral uranium aa.111 to be tm1atlltac\o17 tor ~e purpoae intended. General accouta ot \he electromicratlon and the molecular 41etlllatlon Reparation aethode
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l. Mau Spectro•'•r Anal71e•. At the outset of the var, the When the elecvol7\lc 111gratlon aethod for the eeparation of potaa1l'Wll the bic 333 peak beiag read on • aioroa111.1Deter and the •mall 330 peak on \he entire electrical pick-up for \he 330 peak vaa replaoed with a aore
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stable design while the circuit tor the 333 peak vaa revieed end reeeneltivit7 ot the inatrument, the actual recordizag ot data vaa atlll cum'beraoae aince it vae illpoaslble tor one observer \a read the detleotioD• for both peaks at the same tiae. In addition to read~ the metera, the briJa« in to tocua the ma11 pealca. oord1Jae of data dur1Q& a l'Wl, a oonb'ol waa plaoed 111 the lealsinc circuit aent ot the atoaic boab it va1 nece11&17 '° have a Mthod ot 'eaUng
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rPveal to whc~t extent the pP.rcentage ot uranium 235 had been increased in a eample by the particular treatment in question, and to detect small increM.1Me in this percentc,;.ge. Thie perm1 tted the efficacy of Tarious propoeala for this isotopic enrichment to be tested ~t the early et&bee and thus permit a 1election of the beet, with n ~in1mwn lomof time. rE-te of emhdon of e.lphe.. particlee from the ee.mple ot uranium, using the alpha particlea from the uraniwa 234 taotope aa an indicator. Since th• peroen\sge ef enrichment for the 235 and 234 ieotopH depend on their which enriches 235 vill alao increase the amount ot 234 1n a aimple ratio alplw. psrticlee from 238 ae from 234 because the 234 11 produced from 2'3S 8-Ud the proceae bas been going on in nature a &utflcient time for 23~ is increased, and with it the relat1Te 8Jllount ot 235, there will be more alpha pa.rtiolefl per «ram per eeoond from ~e enriched sample than from a natural utnated aaaple. fhh method was -d.e auff1cien'17 accurate to detect a chaJa«e of 1/10 peroent ln the enrichment. !o do Equipment to do this work wae deyc\oped end conatructed ln the radioi:.ot1v1 ty section and nUJ:lerou.e ae.mplee were teated for verious leboratoriee, which aided greatly ln 1electing suitable methods of enrichment. In pE,rticula.r, the measurements made at the OS were Ter1
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ment of his r·rocesG for isotopic sept-:r&tion. As c bJt-produ.ct of the work in coUJltill€ &.lplw particles from These samples constitute relia.ble sources or bete.-raye lihicb can be used as ete..nderds in the c&libration of beta-re.y counters. Sets or these rtE-ndc.rde were furnished. vnrioue laboratories engaged in radioactive work 1n connection with the var. ln connection with radioactive var-work, it became desirable to methods of produciDt~ auch counters were alov and expendTe. the re.d.1oactiv1 ty section developed a method of copper plntin,g thin aluminum coft solder to convert thee into Geiger-Muller tube counters. The operation WD.a vecy siaple and cheap so that eeveral counters could be made in the time preTioual7 required to make one, with a correapondl»£ nees required for eY&euat1on and tilling without collap1i11g the \ube. eml t alpha. rays, it is desirable to hl!ITP. a counting equipment which will
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nur.iber of these circuits, ad.Justed so thet they Just covered the Tar1oue .eizes of pulaee to be anticipated, the actual distribution of the alpha pel"ticlec in terme or their rRllges from a particular seurce could be found. It proTed to be of grent Talue in identif7iJ1f; ~nd measuring 11otopic mixtures of alpha•ra7 einit\ere when the number of particles vae used to check the percentage and ranee of the alpha psr,1olea tro~ One of 'the problems 1n the procurement ot uranium ore vas the
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The procurement of :1. t rge qu·mtitieE of urc-niw.1 ore by the Government the me~surem~nt of the radium giTes an indirect check on the emount ot the procedure h that, for 11ierHmrement of rr:.dium, the ore sample ts accwnuluted the umount o! rad.1ur. in the sample Crul be compute~.•