- --• • -J 29 January 1946 SUBJECT Receipt for Secret DocWll3nt TO Brigadier General Grandison Gardner USA Deputy to the Chairman U S Strategic Bombing Survey AAF Annex #1 Gravelly pt Washington 25 D C a· 1 or Receipt is hereby acknowledged of one 1 copy or Report the British Mission to Japan on an Investigation of the Effects of the Atomic Bomb Dropped at Hiroshima and Nagasaki Copy #3 FOR GENERAL GROVES t DECLASSIFIED thority -jj00 9 R E P O R T I 0 F • TH BRITISH UISSIOU TO JAP H AH IrVESTIGATIOH OF TliE Ef'FECTS OF THE ATOJIC BO ffiS DROPPED AT Hih'lSHI A AUD ll ASAKI I I DECLASSIFIED - Authorit y I ' • l TABLE 0 F CONTENTS FORE iORD - 1 I NTRODU CTION 1 1 Object and Scope of the Investigation• · 1 2 Lio itation'e of tfethod - 1 s edictions 2• THE T T1 0 T A R GE T S 2 1 Differences in Attack - 2 1 1 Diff erenoes Betvieen the Two Bomb• - · J 2 1 2 Differences in Position 3• 2 2 Hiroshima - 2 3 · Nagaeaki - 2 4 Points of Similarity and Difference - BLAST 3e l EFFECTS CHIEF FEA'IURES - 3 1 1 Kaas Diotcrtion 3 1 2 Dishing of 1 3 Ro of■ Infrequency of Suction Efr eots - 3 1 5 Diffraction - - DECLASSIFIED uthori _IV - ND I 1 OD - • TYPES OF STRUCTURE AND DA AGE - 3 2 1 R C Framed Buildings - 3 2 2 Steel-Framed Multi-Sto ey Buildings• · 3 2 3 Steel-Framed Single Storey Buildings 3 2 4 Buildings With Load-Bearing Walls - 3 3 2 6 Japanese Houses - 3 2 G Timber-Framed Single Storey Buildings - 3 2 7 Bridge•- BLAST E F PE CT S 3 2 8 • Continued Air Raid Shelter s • 3 2 9 llachine Tools• 3 3 PUBLIC UTILITIES 3 3 1 Railways and Trmiiny - 3 3 2 Jioad Vehioles 3 3 S Eleotricity Supplies 3 3 4 Water Supplies• 3 4 4• B E 3e3e5 Gas Supplies - 3 3 6 Sewerage System - ESTDIATIO f OF EQ1JIVALENT CHARGE OF ·TBT • fl EFFECTS 4 1 THE TOTAL RADIATION SPECTRUM • 4e2 FLASH BURN AND OTHER HEAT EFFECTS - 4 2 1 Polial pd Granite - 4 2 2 Bubbling o Tiles Concrete and llortar Rendering• - ND3' 0 DECLASSIFIED - Authority _II ff _ - • NETI EFFECTS 4 2 4 Road Surfaces - 4 2 5 Treated and Untreated Timbers 4 2 6 Painted Timbers 4 2 7 Other Pa1nteJ Shadows - 4 2 9 Human Skin - 4 2 10 Vegetation t 4 3 THE FIRE PROBLEM - 4 3 l Beat Radiation• 4 3 2 Convected Heat• 4 3 S Secondary Fire - 4 3 4 Fire Spread - 4 3 5 Nature of Fires 4e4 RADIO-ACTIVITY• 4 4-1 Induood Ra41o-Aotiv1ty 4 4 2 Primary Fia si on Pr odu ot a- 4 4 3 Effeot of Gazmna Raya - 4 4-s 1 Clinical Effeot• 4 4 3•2 Radius or Effect of Gamma Ray• 4 4 s s Shielding from Gamma Raye 4 4 3 4 Effect of -GQlJll Raya o Reproduction• • • 5• CA S U AL T I E S 5 1 SECONDARY CAUSES - 5 2 RELATIVE IMPORTANCE OF DIFFERE1lT CASUALTY PRODUCDlG 'AGEllTS - 5e3 NUMERICAL ESTIMATES - 6• s s 1 s s 2 Casualties in Nagasaki - 5 3 3 Standardized Killed Bate • C O N C LUU S I O N S AH D A P P L I C- A T I O N S 6♦ 1 APPLICATIONS UNDER THE CO lDITIONS OBSERVED• 6 2 LO 'IER BURSTS - s 2 1 Direct Blast Effect- · 6 2 2 Refleoted Blast Efteot - 6 2 3 Radiation E£feot - s 2 4 Fission Produota - 6 3 PEl ETRATIBG BWBS - 6 4 OVERALL PICTURE - G DECLASSIFIED uthority JV ND 11 Ob • • F O R E W O R D The party l'lhioh wae sent to Japan by the British Chiefa of Staff comprised representatives of the Civil Defence Departmen of the Home Office and of Service Ministries It included also a representative or the Government of India The list of personnel is given below The initial arrangements for t he trip Dre made by the British Bombing SurToy Unit the errangemente overseas were made by th United States Strategic Bombing Survey Unit and to each keen appreciation is expressed for all the provisions made by them Tho accompanying Report covers the work of the Home Office Team but the Service and India Representatives were interested in the same subjects and oooperated f reely and effectively They will report independently upon topics of special interest to their reapeot1ve Services The British tenms the USSBS Physioal Dam ge end other team1 again oooporated treoly and the results obtained by eaoh mission ere being made available to the other uoh in ormation has alraady been exchanged and grate ul thanks are due to u s S B s for their unstinted help and oocperation The bulk of the information on casualties imich is included in the Report waa placed at the disposal 0£ the Briti•h Mission by the Medioal Section of the Joint Commis1ion for the Investigation of the Etfeote ct the Atomic Bomb under Colonel Oughterson to llhom and to whose team the mios on is greatly indebted The materiol me the special charge ot one ot the SerTice representative• - Colonel o M Solandt to whom in turn beat t hanks arc aooorded The Brit11h Report of the Home Office team is in the nature of a preliminary or interiJI report The u s s B S will be ieauing • muoh fuller and more oomprcheneiTe report when the masa ot data they have accumulated has been analy1ed o nd referon e 1hould be made to thia · tor their m are oonaiderod Tiem and op1n1oa•• L IS 7 0 F P E R S O N 11 E L HOJIE OFF ICE AIR UINISTRI AIR STAFF Professor w w Thoma• K A D Phil JI Inst C E F R I B A Dr J Brononkl JI A Ph D - Group Captain A Ee Dark C B E SqJ1dron Leader R G Whitehead D F C MINISTRY OF AIRCRAFT PROD• uctioD J B Halker A R I B A • Gr up Capt F G S · Kitohell O B E H Elder A R I B A - P A Badland B Sc•• A 11 Inst c B A M I Struot E• - - DECLASSIFIED Authority IV ND 11 oo · s WAR OFFICE colonel O SA AC v Solandt R w Bevan • • ROME OFFICE AD 'IRALTY DWOR lleA•• B So • F H Po vry B So I Lieut Cmdr A V Inst » Evans GOVERIDtENT OF INDIA A o c Dr Yet mg B So A lf Inst F Walley B So • ' s Par thasarathy F Inst P F R I O A J Inst SU l Jt ARY · The lteport h basod on the survey made by the British team of tho d lllage oaueod by the ntomio bomb■ l'llttioh uero dropped OD tho Japaileoe o1tiea of Ri1'01htu and Nagaaokt t 11 of a preliminary oharaoter and a fuller report Will lntor bo available prsparod by the United State $trato io Bomb1ne Survey with d1oee team• the Britiah tea eooporated 1 Dosoriptions are iven of tho typo and extent of the mater- · ial damage in oaoh ot the two o1tie1• Fire waa the oauso of muoll 0£ tho do ltruotion nnd there 1• nidenoe that sotte of the f iroe were 1n1t1atod by pri ary and othora by ee ondart agenoi••• Radii ot domnge were eotimtod for Japanese dwellings and for other buildings e g reinforoed oonorete and steel-freed ntructuro1 buildt n • with load-bouing wallo eto H detailed in the Table ot Contenta The effects of heat radiation end aleo of nuoleQJ radiatioD vrere investigated and ue deam-1b•d• Both effect• are eeriou• and differentiate between the action of the atomic bomb and ordinary HE weapon Seotion 6 of tho eport deal with ·c0nolu11one and J pplioationa and th r• eatt mat•• have been cado of what might be expected in Europe ond in Britoin trcm atomio bombs d-etonated under similar and under dit£erent oondition end from poseible penetrating bOlllbh r -7Ob DECLASSIFIED thorio II r J D'J ' REPORT OF BRITISH TH E IS SION TO JA PAU on A ItWE -TIGATION F 't HE E FECTS OF THE ATC IC JBS DROPPED AT HIROSHDfA MID NJ GASAKI - 1 I NT RO DU C T I ON 1 1 T W SCOrE O di I b VESTIGA'l'IO l Th - object and scope of the scientific mission to Japan were laid down i n directives siQncd on behalf of the Chiefs of taff by Mr Vice ·arshal illiams Assistruit Chief of the Air Staff f perations that to the Home Office party bcini also countcrsigbed by Sir ileginald Stradling Chief Advisor to the Research and E perinants Department on behalf of the Civil Defence nepart- me nt of the Home Office The object ot the mission was to studJ t he eff eta of bombing in Japan and specifically of t1 e two atomic banbs at Hiroshima a nd Uagasaki Tho scope of the mission was conf ed to these effects the directives instructed it not to enquire into r esearch con3tructional or operational aspects of atomic banbing The brief attached to the directive unde rlined ulti l ately the aim of the miesion was less to list the damage 'Which it f und in Japan than to draw lessons from mat llas found which would be applicable t o European targets and 1n particular to Civil Dotenco in Great Britain o quote tho intro- ductory sentences from the brief - 11 II DECLASSIFIED A uthodty III ND3 ooS'l u s s B S and by • others No att empt was made with the inst ruments at oar disponal to make detailed fresh determination F nough measurements hotTever were taken i n each place t o confirm the general laoation of G Z as that marked as the centr e of the circl es on the acc o ying maps and to give reasonable estimates of the height of burst These are Hiroshima - Just belo 2000 ft Nasasaki - Appr oximately 1750 f't J These are the distances betneen G and A X Sinco G Z was effectively at sea level at both pl aces they may be taken as heights of br rst above sea level Differences in the position of G Z r elative to the main built- up area in Hiroshima a 11d Nagasaki are remarked under 2 2 and 2 3 below 2 2 HIROSHI iA - is a cit y built on th islands and shores of the delt where the river Otaga1Ta f alls into the Inland Sea ilthougb there are hills r ising to 700 f t and 800 ft tb the inm ediate no_rthwest nnd northeast the city itself stretches over f l at ground in all directions tor roughly tT10 miles from its centre t he built-up a r ea waa ap1 roxi mately 13 s quare miles or t his tot al pre-raid cover s uggests that ovo 20cg was devot ed to some kind of industrial or busineao enterprise inciufng extensive military storage and shi i ng facilities The major industrial pl rts ar modem and distributed peripherally along the southern and wes emn outskirts 'ot tho city at distances of bet1teen 11 2 and 2 miles tr t fie centr The city also contained a considerable nUJllber of reinforced concr ete buildings owned by banks insurance companies depart·ent stores papers and similar mercanti le ent6rprises DECLASSIFIED Authority tV ND I1obS - - • A detailed description of the roid exists in an aooount prepared by the Prefect on lat September Ae at Hiroshima bombing was from about 29 000 ft tho bo b foll just after 11 00 a m on 9 August in the industrial area between the two largo Mitsubishi Ordnance Plants north or the bay Again there waa a bright fla1h v hioh gavo plaoe to a haz ot white smoke whioh rapidly darkened itnesses speak of a roaring sound some feeling of pr ssure and wind and or heat Sinoe the population • aW8 l e that an atomio bomb had fallon on Hiroshima the disaster was lees uneX eotod 11edioal and oivllian services_ Novertheleos it overwhelmed the On n g to the smaller area of Nagaaaki the barriern formed by the surrounding mountaino and in pertioular the poaition or o z in the industrial seotion of the city the area ot deetruction a• markedly s aller t an at Bi r oshima boing rou hly 1-1 2 square miles For· thiF reason the JapaDese at first reported the bomb to be a maller version of the Biroahima model The looal population tooling that the bomb had mi11ed the centre ot the town took to the hill• in fear ot a seconde At at Hiroehima thero woro extensive fires but they spr ead co11paratiTely slowly and do not offer the oompaot appearano• of tho area ot burnt out in HirothiJla On the contrary the 1• preaaion wti1oh Nagasaki makes on the visitor is more novel and eerie• Long line or steel framed faotory sheds nearly a mile 011 Ge lean their skeleton ■ away tro11 tho explosion z Concrete buildings haTe the aide• fao1ng t e blast broken in like boxes O er a large area such bla1t reaiatant object as telegraph po e and tran standard• are leani g any trom A z on the surrounding hills trees baTe been blown do1111 to oonaiderable diatanceee more the appearanoe or Thu• agaiaki present• auoh a 01g 1 ruok by tremendou1 burrioane l fr • A oensus OOJ Pleted late in November 1945 gives the population • as 143 000- This is with n 1% of the estilllQte rna·ae l y the JJiasion froD somplea tak on during ito caeuelty enquiries • These features do not show well on panoramic photographs and Photo No 2 does not inoludo them Photovaphe suoh as No 10 give some idea of iho effeots 2 4 POINTS OF SnlILARITY AND DIFFERENCE In awmnery main points of difference are that the bombs were ot different materials and oonstruction detonated at different heights and in different poaitione relative to the main ooncentration or Japanese housiJ' lg9 Further the cities were markedly different i in g ographicol layout in unifor ity o buildinc and 1n the type end strength of non-domostio buildings expoted to rick• As • reault the response of the targets ahowed some marked differenoea We have dra m attention to tho difterenoe 1n the extent and compactne•• of the areas ot fire Ad quate explanations for this differenoe e xist in the ditferenoee of building and building denaity difference in the appearance of the blast damage There ere some At Bagasak 1 a good deal of the damage re10111bled dam ago done by a high steady wind• This appear noe appearanoe ■ wa1 rare at lHroshima more in turn there wore eo suggesting the operation of the negatiTe phase of th6 bla1t waTe of which there seemed aomo 1hat less evidenoe at Nagae i_ Yet these appearances may al10 have sprung from the differences in building typ••· for • much widor range of building trengths which are not al wayB apparent f'rom an e tornal view 11 s o ' result within the unif rm de- structi n of J apanese hcu rns freo k behoviour of such struotures as ' I reinforced conc ete framod buildints at unexpected diste noes is more conmon e t Hiroshima Finally it ohould be rem rE-ed that Hiroshima had been struck by a typhoon tlt tho begin ning of Septfll ber • and by a -• second early in Ootober which did not contribute to the ease of lyeis of resul e thero Against this there is n formidable array of points of simi• larity vihioh fro the bu rdeD of the sections tjiich follow• More im- portant than diff'eretces in the extent of' fire is the high risk of fire oreAted by the bombs The whole ph nonemon cf radiation l'ihother of' heat toward• one end ot the spectrum or of grunrna reya towards the other ie Offllt IOD to all such bombs and to no others wer_e importent Hkenosus in the offeot of blast• Similarly there Air bUl st at these ocneiderable heighte neoessar1ly give a marked downward o onent ot pressuro over a largo area ao that there was a tendonoy to f•ilure ot roofs in both place•• The atriting app ranoe or the trees near G z in both places with their min braDohee town off by do1m d push had the same origin A more important point my be aaoooiated either with air bursting or with the oompletoneaQ of the deetruotion oauae4 by the baab Thie ie the oYer larce diatanoe•• ebaenoe ot any masa1Te piece ot debrie oerriea Small debr1o 1uoh as til••• batten• etc wa■ epporently throWD considerable difttanoea being tound on the flat root of the tall reinforced ooncreto buildings oto Identifiable debrie ot any appreciable t1 e waa howeTer almya £ound oloao to its point ot oriein and llhere aaeei•• slabs auoh ea bridge deoking had been 1hifted the mo•ement •• buildings near o z owed their slrl'aty largely to the f ot that they wero exceptionally strong and also that they wero not subjeoted to auoh large lateral f orces as were buildings more remote For example in Building No 6 1 300 ft from G z at Hiro- shima though it was gutted by fire suffered no structural blast damage One aeven-etorey building No 23 at Hiromimn was ot special construction and although only 1000 ft from G Z trom A z 2250 f' did not auf'fer any serious etruoturd damage ex - oept that to the roof- The behaviour of Building Boe 95 i• alao noteworthy• The portal oonetruction i e designed to give stitfneee to the frame and though orackltng occurred in _1ome of the h'ae members and nll and root _ panel• deflected to some extent no collapse occurred at 1600 ft from ·o z 500 tt fran 111 I R c A z -J Light amed Single-storey Buil dings• Those buildings were mostly of lighter oonstruotion and failed at oonsider- able dht-ano••• through aa111 dietor-tion An interesting example deeoribed 1n the Table and illu1trated in Photo Hot 6 • • that in th• llitsubhhi Steel Work• Target A Building 30 • The root consisted of a reinforced oonorete arohed rib with a ateel ti•• teet from G z Though 4 900 aeTeral baye of the structure oollapeed the truaa tailing under the oonbined action ot the do11nard thruet ot the blaet· and the 00111pre111on foro•- An umun1tion •tore at 4300 rt from G Z at Biro1hl• and •h1elded on two aides by high earth blaet-wlla suff ered oon1iderable root damage and eteel door• are bulged the earth bank and on the inward ■ both on the faoe remote trolll cero• f face nearer 'l'he wlls ot the orka no l·i r the tt a nomo £uro i'ul tl·o pµrlin of thin Ao aentioned - V Jr ' •' o Tho ne u · r building P hoto o 10 an to l collapse - loan - fT O ' OS and etl Uotural da - ot tho bo b ln produo1nc atil' lete l mothod deocr ibott in m 11 1'7 eel O PPJ'Oxi ate ruu a for Ana ot V ND 1ODS t h• nv• •• e circle ageawd1 t'feot1vone aa Utftot - for Zti 1ctul'41 on rudt1 cnrro apcmd1n to tl·oa• a t'UP DECLASSIFIED cy 11 ff 406 a ncl Yo Ute rollorl11g Aroa ot E t'reottvenena tor The •bile · oooewhot t 'Nater r oro ho ro o ·or urtectt vw ettoct• nusuitd Photo Jo 9 t he entire bu 1 11 llB ·uould be di tc 11 ocl and diata'·ce Authori _ th n a a •ttoct0 ot tho bloat on t io_ t eel--tn cl ed typ1 and othor buildlnga _ I otel ·· 30Nl itrl1or• a to J 16 in ·nu cl co t ulldirico ua cl on t tlt 3' these d 11 o atr otuntl · i r ir -- r'l so ci notruc n ooo n CQ · a11 bu lldi nor l do lgn l h dL feroncoe ve stae - b l 9 1500 acrea - ge- 2500 a creo I ao -ofi cot othor bu n LJ18 at le1100 ' atruet l or fic1 1 tho lo dnrotion ' iwl h l ietuut au · JO• Ono rooaou tor thia io tb lt vt tb ot tbe -poaitivo COVilrit j lu GO c- than I wnve luilclin go ortt co parable mdldtcgc eo'VOl' l nboeti of the bl ot o ouch o c r tod iron or tir bor ohoetlnso aro mol O outcopt1ble to de wi tb r I 4 ' ' ht r siir ant co ri au ch e o r 'beotoo tl tlnefer a hiSh prorortiou or tbo poait yo bl Mt p ronaur to tho tore th · • t11 Ulelvoo roil 11herooa 11 frlo'ble cOYering Dtruoturo 1 brok4m before 1t hue had t to tronofer ·ll' 1ch of th load to tho atructure 'rbta f ·oot cnn be oon 1n Tar 1ot 1 tn tho Table ot Ap nd1s 1Ph•ro the wilding 'ml ap1-reciol lf diotortacl ti 52 0 rt • fro v oro t ba allo beloo natniotocl ot B c nd thoretore fJG lOla clt noro roo1etant to blaat than uaual faraot 2 rocei u 1•ncial o •o 0 111 h1 r dill lttc At o tod 'itb aobooto r raotora nr oc i ll the bo vtour or nt d Wildin include ita or1ontat1on nn4 tlulpa ond the extent and d1opoaition or wind- · bnacl Jg hi onl 7 tivo out o £ tit t y tu1ld1na a did flro oontnbuto to the da ge t o th structure -'tero t wtldlns• oro p ropo fit-o 1it lilrollhi Jll roalw la otly GU 't O mdod b r do ottc o re•ponolblo tor a larGo uount ot t •voi aomo l u1141na• nabled eo1 1mteP to be t' ada -- t DECLASSIFIED thority 11-r 1 v ND l1ObS - Q EijrffilE1 eX4 1plee A fuller acoouµt will be prapar later na u rt I Hot a 3 2 4 §u 11dinm1 • l buildinco which ure not numcroul'I ttr ot various typoo - some boing quito ll with 9 - 1 rallo and others ublic buildincs ·ot aoaive eonotrvct ion such c the to nan-catholic cathedral at Jae Q4kl · Pho o I o 1 Tho a cond4ey of'focta ot tiro have in • rrumbor of 1n a nee a cnntrl butod tQ the atru ctural da it haa been abnost ao tba t povoible in sw ti caoee to J1tterentiato botnon this daeage nd that fagao co ttribtttable ¥ blllst The wreclulge of tho 1 Ro1111 n Catholic Ctitbodral 1700 rt rroo ' 'Z ia shoM in -boto 1 o 8 Fire w a undoubtedly rospono1blo for eh ot tho • ere in thto inat e nco tho·1llh strong blast rtecto are opparont One rointorccd concNte doe l'J•• hna been ovortumitd and lies unbro n at th foot ot t he hill upon which th Cathedral otande • the othor can to aeo lying o ort urned within the onoral debr1• 1naid e tho bu ild The exa 1t chani ot tailure 1e not cloar but ouoh he 'f'l __ aight quite well cause aei ieral eollap•e it tm BUppoJ tina ollo or brickwor t wer• badl ehattered b1 laat oi- diarupted t7 collaptting root truaaae at ot th 8truct uroo with lo d-t earmtt wall• nre 1 nduatrial bulld1J'I Ir -iI - -D ECLASSIFIED uthority - IV ND f ObS o inq ot on - tor y h i bt the root belnf t n sa · u a d nus O plo Tlouo 0 at lf1r osn u oo 1oed t wo l uildines one cc • • tho oth ir• 6200 ft ot wbicb B · collapoed eutrorod no stru ctural d aJ Ag nt 51ailarl 1 in Tar et 123 at 720i rt the roor truo e voJ iowi c c'ked unc on •1th croes U • 500 rt ft Oll • ero nutfvl' l no atruct u rul d ti pie rs whil Cll'got I at 6500 a tt nth thicker or th ao au or --- - for BA•ine tb 1r o inion on th behaviour th tea consider t t th r ho tnc I irnrTuf ce - 3 2 5 olition 3000 rt 'poet• 4a to f eq DECLASSIFIED ml oth1'r Wildinsa ordinar 1 liriti b n reat1 AUQQQ t 3000 tt 5000 t t 5000 rt 7000 rt 7500 tt 10 000 ft lJ 000 ft rw v H vor• - c biildlnge rr-· _r•thodly III rJ D 11ObS'l lla coll poo • ot the ordor of - ould l o to ia t n mnsmsJ 1 - or iobor conatructio with• rt1cal n a cont1n oua od aill 'fh ro te B600 col apae rt Sor ioua non atructural -✓ C £ Y D a J 2 6 ·• buildinga wer r t vory ' ' bont In lll roohir 8 and COtl lOU • • f • ' ' Cuob 1 ihey oill boltad to c low ·concrete' tou ldat lt n wall ' ' the upri ta Y ro i'requontly about 4 X 4• OJ aeod 6· teot aptrt 'Ibo oro based upon a moj ' root t1as often tiled nntl cu -rlod n utool o _' heavy t111bor truoses Tho l u ldlnca unlooa adoquntoly 8t1tfonod by internal part1tior o otc were Yc17 auoceptiblo to aaas ettect diatorting 2'Qsdily at web groate1 di liau ceo than the do - c atic proport7 Collapse wa mst orten duo eith jr to xcoof ive htcrlll d111torti n or to the failure of tho tu bor upriebta in tho 11Ulla tho mortlceo end tenons in particular boi ie int 1 of ealmoso In m 1c cae cn the root coll apned wlt ut wuc l ctornl displ 8 oe icmt md muot hl va · teon the C6UdU oi DY CU$'1 U ll les - - -DECLASSIFIED Authority Nfv D 1ODS Bridge - Sime 49 bridges r ere examined vi th- in a radius of about 10 000 ft from G z at Ragas ki At Hiroshima onl y one gridge Ho 29 was destroyed by t he explosion and this was in such a bs d at ate of repair initially that collapse was inevitable nine other bridges of timber conatrQction were destroyed by fires following the explosion the remainder 31 of which suffered no structural damage continued in -uae dthout repair At agas ki four road bridges ere rendered·impassable and two bridges O one carrying the railway and the other a tr im m7 - ·ere so displaced and defor ed that they lere unuoablc until repair3 had been executed The ost spect cular bridg damage at Hiro3hlfua was that suftored by the ' ' Bridge f os 23 and 24 The main girders were practically undamaged thought there was evidence that they had been lilted The docking ho evor pad obviously been separated from the girders lifted 9evoral teot and displaced later lly one toot ay- slab had also received an i ppreciable longitudinal displace nent See Table At Haga 1aki the majority of the road bridgos were con5tructed in reinforced concrete and ere of relatively short span Tht y T ere usually of the beari and slab t pe with 711 thick deck and supported on r c framed piors which were often apparently not s coured to foundtions ' l 'he railway bridges WGre ot the plate girder dock type no1 18 lly si igle track uith the sleeporo fixed ditectl to the stringers Of the reed bridgc3 ren ered unusable ons lo 5 2325 ft front zero wal ' eipply support ad opane in reinforced eoncr te ot three One span v as deetro1ed and lies fractured at the c nt r e some 7 feet upet1•eam i e a 1 trotA li®WrlfEl - DECLASSIFI Authority II fl D' 1 S4'- J '3 S were Bituatod 6500 um gup lien · At Biroab1 ia tt t '0 3 G z ho 'buildings were and - - oro de®liru iodl the e rowno bein5 • the fi8S-Sor o aor'iou i y dtlc agod 1b two car holdel · nuttorod bl dot daag• · h eo mrarde mid to rn • t 'open ' _Tho eworJC waa - • not distortod • I wall otntod that the •ecc ing gao bu mt lt·e a bu go torch but tbat oo oxpl sion took plneo Gos-own doors we duagcd d procluotion stcppod t nderground_t' ctin had not been· they crosoed brt e rA llinod but except whe l O tlle trom c z 8 9 no da iaao was • two bolder of one plant 6500 tt wore diahod ·1n at t ho top and ij' neui ' thought posnible that ao at liiroGbJ Evi tho lack or lateral d1otort 1on was t o co e ont ceounted tor by 'the lon · d lration and longt h phase ·or tho blast ·ave or the poaiti Tb oingle ga - bolder tit onothar plant about 3100 tt • • awq trom O Z na wrecked the otructuro telDJI badley dtatorted fro cero It as stated that an explosion bad ocoumcl 1n tnis case but tho evidonce for it - snot v ry convinolna Ao t · Eiroahu n · VOT7 little U 41V dc nnaae wo th ught to haw croa d br1 1£••• 3 3 6 The se row •••enaee depth or at out one sw - pii ee ot Hiroshi burled to an av race etro are not thought to havo l loen dat a ed Two outlet trap doora 1n the riTer banks are uid to hnT been rI -- DECLASSIFI I Authority I tJ D1'l Obl I 1 of aoubtful • tor t a ' rgoo o f l • o prer cun tlr 10 relitionohi ot Torao I ot GVoUabte thauijb e W • I •• fiauroo b r a'hB and B1aolt l'iul tor t ho eurea at var1oua c liota ncoa fr bore chorgea ot tl 070 lb und 20 280 lb tho it to dodl d that a pauk pl'O occul c at a cttetance · or r toot rraro ot l he1·0 r • 01tiaa u 1n proviwa 'a •oa that Cb do b por aqu4re inch v'J J 3 6 It ie to bouaao ot Brit1ah con atruot ion wovld be l ely to occur at 7000 concludo4 fro i 1t1 on 9 rt tor t l' o Hlroohlrn l n tlto t • at tic pr o suro ot about 2 lu aq lnob 111 produ or4Ckin • tho taco-on or tha blaat oqui'Vblont to n be t altoD o q Wlttt1 ot ro11 re a lb oq 1nch proll8UJ 8 if tho neo tho atoa1o b b T T lara r t han ldt-on t bo 000 J 6 3 lb • 2660 on11 et Uiiaehl or 500 J 6 3 lb J270 tone nt op akt c conSllJg to AC 10 t e opt bo ib ll•• be l S gbt of blarot toy 000 lb • ot' •ioible i t t 1 0 1 t t he equS l lent a con lderod os to 3000 ton ot the 70 n hoi t · t o o 900 t U equivalent to 10 0 'O tons ot 'l' • • tbe con-oo 'lOndt ilg hot ht -- bo I 1 w tt 1 r etaad of that uctually ut1od - 1750-2000 tt I t tJio alrbur- 1 ae ·ou and aac oalculotiano io not -rarnmti the 1 ntroiluotion ot th1s rot'lno tont to proc1uc tho co11 o pa tho cn cl iilg· - r 9 a J pamla tllon the QOdiflod f cl ao c tltoriun for bl Aat da m o Uft1' be opplt 1 dctacri 84 1n c re n collar sea or d1•t rt1on o thfll blut 'll 'up to tt- o 11mlt• or C0 d u ago d1r- ot data not l 1D GVA 1 1 able tho d ira tion w mu be n 1-l en fro the our'W'Oa f'c bo2b1 ln c ot tho 2tJ9 • O i thooe baeoo tbe ba ro charge of Z f 1r required to produce oQl1 pao or q• brlcltwor cat 7000 tt te ••t J tetl to bo 50»- 6000 tone and at 7500 tt ot tho order or 10 0' 0 tonu t1eune hat the t thoae diatauceo lt 1• o vlou trom t ot tho ohar ea talla ott ft'Z'J' rapidly • end it c-antiot bf ro j idmld bltb nuttioiont proc1 alon t o o tl ••ticato• 1' r P • Yof roliablo wt'lber or otber •at too v• t on tie tied on tho aut l ' · optc d £ t 2S tolia' of • t tl at no ictit atontc be i a w 2500 1m l bi • tho eatbuto oor it f oren o ot oxplootTD charao 1 tl ien b 1J0Ulcl be rathor ft • the oqutYa3 etrt woi ht or tho • · than 3000 tona or r n T b bee l rot1on or t o iti'Ya ot tbe lon ao 01' tho blo t v 't h rudluo ot c a Co clooo not inttr GAao •• rap141 y o proviouu calculntUmo 1 tc hi h an oetl ate to l'Wv 1 011 wbou r d ta are availuble tbe totata fi -- -DECLASSIFIED Authorio bio f J tJ Dq1ooS 7 ce thAI hC S 'tee Qot'r' IOll UC a o t l'it1l irul j N3 ca i nvaid tl _ ch1 it un1ng e ° ' 'do 11ro dtation untl nidio-ucti'Vit 001 u ·1- n cauood in · ·vari ot penot iattnz alior 1 Ao thl i ort d ct t it ot t tiea t t p ono or i on o flahll 'lr m t t is 7 la nc t r • 1h re 1• o 1ft tlllina t 1a l aw i OQI C 0 tfect J'l ntq le boti'b • tlt ac lo It '11111 ifflar that this hn nn · t v ott octa ot t ho b otl hcua On 1 n r t or T i ot tJ rr-I ot the t t1 rol o ot ntt-1 utie n 1 t o t DECLASSIFiED Authocity r J IIJD j0059 fmftf f CA lt - t•toc t t I • oit ttna aan Thto tJ • ' v 4oopro ln 1U roub1 • ' 1 til fP'Wto la lo ad • l't wao · _c z ond found ' • up to 1200 ft o • · oro ftoa • • found uh1 lnr · crnin at 1800 rt £ro• 1'1Lttll O WJOnd ' sooo tt • lit t o •J • Japaneee roportt co kt ln • tound l i lftOOUJl • atono 11 nlnu th •lcto e W'lcial• or roado nc r o z to havo t1 akod t • tte lo ot ito « 8t tuo t orycrt ulo tor oeyotala Ma uoo 011 cr1t1a l i n or to cauaga by tho u•l noi m n aktraa la reture Usina thi und t rcrt u 1• ti r ttta _que rtz 1 c en index ot the ho depth ot mirtcco m • t be 3opnnoao pb -1 1 iciata eat J lated at 1500 t tro o a ru rc 'hiM 'to Have ucitci1ed 20000C - 1 JJ 4 on tholr t or ob ut tbororore ett or tl a rlD Ji Thia f 'iC U O io ba-4 uuro nt ot· tho tlaktn of 1-to to a clopth at 1 at- thio dJ l'ltanco vll1 J were not able to confUtJJ arid on i1cm• rep rd TlG tlonot · I tte 1 ao Nportoa 1t bo oi d 300 ft At l r Gaki f JA lt th wnt• • 11 1 uish w'bicb r4a MON aril7 re ndaty uca don Japan n ht uooa both at Hiro and at asa 1 an 1 both wero subject to took the tom Qf ra1•1ng bflbliloa on 1ho oxpo d eurtoco tho bubbloa 'baco t l o • at 1noc-eu s d1tJtrulceu fro r 2000 f • 0 anU round bubbl to l Dther Japoueae f'igu a tt fro t ho rntu a tor til o bub 11 vorar e nln1 leas 11 to to bo 1200°c S itt nt luiv and •n col 01' oc of t'1o boro whicb 111 nabl• Wi 1 o indoponaer t oe 1 oncl ko ten ta- ho t 16 45 1n Hlrodb · at l2SO ft tro1I •ti do• r tb• •• tho down- 1po or 4 • dift tnr oor 1 tod or• fJM1 unatreoted tand bout 4 ndo ttii wao lx rd•Nd by b-lng•• 1n bicb the colourt ra pink ot h tu1 - expoeod 5 to 5 but ho o 1 aurtaco wre 11 defJ ntk 1 1 fi' rmter DECLASSIFIED ' Authority V NDi 1ODS J-f e tot 1 wi th atout ca s th oi'foct on · cru rf'ocos ot tJtir idnd wao 10lnfr or btirnipg _tlp ot curt 00 duott nits AG ro also uttcctea ouaorTOd on p blil tia diroct ly Thcco aurt c -ebOlred the met r ed err ot or sc orohln an c 'larr 1 ng and the clearest sha dowo canvoniont ndex 1• tha corch1ng of hlch o tounu to hav tolei ap poloo in 11 di cttona at Jliroob eoutb ot o z and to at a «Gak1 At lilronbi hi· do I'M or unito fairly unU'o ity r ortb nd thia ocorcfilng dieep ·eared rouchl1 et 9000 tt at n a 1 it ttxtended 1n plucea t 0 000 rt I to 01cc do• a uaod dtd not de it Uy the or pin r n an other tl a trfttcoti o tho ld td Jority ot zero d tor ui 4 tono 4 2 6 a1n oA tlwr o - r its li' 0 rah ch r oleo t ut it •i e J'Od or c dar indlfto rontl 1n the t tor aint iih O nb r- -DECLASSIFI r•tllo ity Ill NI l'f of _ I llustnt rftd o 'Ou ' bumt 'Ir till ro not iccoblo ael at ion beon burn otr treat cl And or colour• dte rod blue ' ot oil paint • In all t o procood1 c wntna obJecta hen th re r aet by inter- u1 nhadowo ch1oldod a port ion ot tb• other nioa exposed aurfec ll 1II 'tho dlroot hoat radiation retained ita original at teJ out 1de it doi ined boundaey- 1t wa had beon no ccorahocl nore or J ooo fho t p'lJ' On oCC4$lon th ohioldina object re t bl ln • oltmp of a e or the leaf or troo it io known tl t ve •tabl e• wlUlin JOO rt ot G• •• or core Since • wlthered and barnt 1t tollow · that 1 hft f la h cuot ba • andod in • t l e le a than ut r d fc r t grAan or 1 at to ohr1'1'0l the required ti -wit h accUl'lloy it ttiat r --· I II rJ D- 'f OOS'l DECLASSIFIED A tho ity 1 ••IUtied to b l a lllflOt o• 1 te 111• · · or -20P 't oC 106 oaAo rtoNDt expaourcua of o • bte lco bo io'M that eo o ·p ople had lAC01J wi th t bei r bnndo Gbnd11 t i Je to cmlold their· m Japo noee - Ya1 o1at• fiho bad a th tlak1o of gru nit o 1t dUl'tlt101 • aecnnd ari 3Ubao here hocso t t hmtod • o Ul ICd 1 1 o ta'e t1robably iO lon o ro weoopliblo to proc1ec AGUt'O nt or hor1 ontal btir r thoy 1 -c ro noral found to bo 1n 11 Dff'O fO - ohioldin oi tr uct ton tl10n tl• In particulcr then coul d tit obourved thu otrild nt pbono non ot t • c oa l•Ut 1 VP4'Ural' o or tho obtido•n or rrow objec o t fiot nt diot leea tro 'tJ acorc to pal'lll lol sota of do• •f eot am ato uaro 11 o roly porcopt 1b h11o dtftNtot1 n other •vi ellQ hav -- Ill ND -1 'f oos DECLASSIFIED Ftho ity d c ntr1wted to tbta bf dittl i otiion rae f und tli to t bc tJ n1to ei and tho htchoat ot th radiatlnc fire • fro the outeot t inwat 1ento hont rad1ction as a poculblo cauno or tire wmmples 19er -e t l orc ore i oUght 1n which other c riunea aight en u iple1J or £1 ·o vo1-c round at lY ltb ii 'TOshim be olbdaated n J ngasa ki 'irhicb it ais difficult to acc unt for c oept by boat radiation ' 'hesu ocluJ tolopbone poloG otc in ioolatod cy f66ld po t11 nnd po n pooltiona e g in OOM toet bove the t otto11 or bolo• tho top and ot hnro 11 uont at t ho tllp o y ieol fro t hl mt only Sen lao Photo o 19 An int est1 ng instance d i ire occurred at Tar •et C u1ldiJl ' G Hero -v rtlcal un no 8 or an t 5700 - t 1nted l mirdo bAd bo n fi ed in front or louvred mte ne r tlio rid o of t o foor o' he lar o ot l J 'rn d sh po otb tor ul cicmut purpc JOe ot inco • Tl c wild nG buetiblo con ruotion mccopt tor tho e bo nia the louvre end 11e lt tnmeo ond the lln • n one occurred in the mot ond for the whole lDn th tol 1350 ft tho btlarda the J ouvr r be co let ly deotroy to burn pc rtion ot t • ro-or ' f and the wind h f1ro hud uprend do pu rlin • 7h re in a the f roxihad in • f co no other trao of tint tort al within tho ulldin which alg'ht bovo ntartod a fire D 1o t'ir d bu1ld1 itbtn conotdo robl di t no • t hat the inlt1ation ot t hiu tire di tion tb n to OX1Joood to tire phono It e moro like du t o prl ey ny ot r cauae l ut only ono or 10 or 12 identical 11lllar risk tone v ti cort tn pro bllity on • • • ae Concludo t the rink or »riuar r1ro to ur ·creoned t indu etr 41 build l' GB is npprot i ablB up to diatar e e n exoe s ot 50 Or• tro G Z 1 3 2 _ Cgn lOcf q oat - to ovidenco could be row or In tbo nature ot 1 blng µ r1 ey ho or it io ditt'icult to v1CIUA11«10hhtm 1 hio onui e c uld ho • o 1'11 6B cau ed boen iaola ted or eonvectim only t it c uld bo iaportant in t ho pr en e of GUOb lnteru1 rad i ate t he 4 3 3 or rtre So®JlYfiFY J tro - 1Uec tric l wi r n ever · ol 9 1hc widoaproac i QOJ e to oleot rical sub ttcms w nld of courw hnva ouus dtctely _ tho circuit braaler·o t o t'1nctlon but • - 1 eto io not neceaoar1 aoonor t h n tho spRrk1n a or ho ting neeoscar y to duatr i al a ull a domont1o 'buil i It e not Jan r of ocond r_· One i rt a u ll fire Si ailar • i o itJ ti reo rill a nu Qt her uacondn ' Y f YJUl f aa portent to proao tbi • 'i Ya • int in lar ·ale lated tiro 1n a o n how v r tairq def'Wtel y e tobliahod to 1 Fir Spread - ' here 1 no doubt t did occur in both c1tteoJ nu ibors or r e 1 oa Ira rate r otr u the utnet of Gcondary or1 in I proad t ti r ot rik • is tho evi c tor t of t ti au oh which ao tire tlghti biuh1Y coulauatible bJ 1 ldin at h In rt toularq in the induatrlal 'bu1141 ·o - DECLASSIFIED Authori tV fV D 1ObS • • boon virtually 1 reproo_r Por e 8tl l - the hoopitol t na nowci between 2000ft cmd JGOO ft fr - all7 u • '• ooa1stoJ th bo b except ion- yet tbe e ine cor croto buildings oro at onco re ldorad uaeloo Mel r oari holt the oocupanto k1lled t ecnuce tl e co ulatlon r heavy ceilinga oO ion £loora ond othor tittin O with which t hoy oro filfod turnod W1controllabq It is• a vocy llain losaon thut c firoproof building 3hould not be converted into a jor flro ri K by ill ohoGan fUrllioM n 10 4 4 P @IO-AC r J 'Y r re offocta 'Dill be dioeusced bore 1n their n tural or · r t h • uro - rays Md -other iOnot rotin rn t11tio11 l P produced t ic r rt ot thn tot l spcetruc of onor itercted by tho titoion p 2 io-aot1ve pr ry F-roducte Ntult 1 tho '1 oions fro Rnd J Indue rndlo- otiv1ty c euoed l y int r ot1 on 1th tteri In t fnllo I no •t or no1 1tr- n pt ho been tho oflooto i roduood bf noutron tro r YP oharnoter both aro bi liq penot t1 o nd pr d't 10 cueb tho n belnga with th1o exooFtion that •hil n utrona J t ' NCO l'1 int ractton with tt r induced mdio- ot1Y1 t n no t r t • ut rona l'OClCtcd thuo · i ndent r of in the hu n l o1- to Le dlo-aoti o ltllBf f T u 1- noutron •P Oe r • • aterly t urbs boure aftol' the explooion at R1ro il11 r a in tho do In turn th1o tJbo wirni r y bavo boe11 tl e r ot t o ho va re tho p rnwt al · o oxpectod to 11 'lpOrta nt thnn i l duced radio act1v1ty 1th bo ibs 1 -Jrnt conco bo no nt lo or th so P1 ' ducto ked vhicb helghto the und p 1rticularly rou h c rmi would c itain mrkedly atar amounts or thoao products in itieo hich 111 ht bo dan orouo ror qa or longer Etrg9tp gt 4 4 3 ovorwh 9m no Jkr p - ot t heao er ·octu 1ngly inportar t lo th ton tnmon boiDee 4 4 3 l Cl n o l f19tg - Tho te g jo ueod e in a gonoral _oonae to 1nolwie all L Onetroting radl tion0 o ll neutron t· t CCU It 1a pr Jiblo t 1DjUJ 1 t other t ypoe ot diation contributed to th tnjurtoua otfect but no atto oa irradiation ot this oort hao ovor boc- n 1'98t 1ntoro t n boro ao that the roaulta a -o ot vo17 n 1aportcm • The orrectn ot tho h - do not d 1ftor rkedly rro the kno weN 'Ihoro no akin lo 1ono 1'hloh could 1t 1a prob b be •ft• ta or - • 7 be unti ll'lar to - DECLASSIFI I J Iv D J 'j'@' I era to deacribe the 1cal reGUlt or 1rr dlation lng on to dlsauaa the J thority on orraota ot - rayo iab ie relativaly rv iotQ t al Nd no otf' wto Sl nce tho r ·· rayct ro voi 7 penot tiro nd tJ In aoneral the gna o o 1n Rnt ca ffect or 1eld ' oa a · ·r o 1 broadly ce rr ct nted description should s diate no ueea sen bl odt dinr hoo e aot in fNq nt l J 1n the et t th1a a AQOild are ertor the lrat p1la lon l oo • • Ill the• ro co so• tho clinical ptctul O bocaa do 1nat ed b y it statiorut of d tiotont blood ri th a caooa pupurlo o a tion ot blood a l 1reatati ana or all 1nde ro tton led to U ha• l'oto cbuo r o oleo ion led ta al - --DEC-LASSIFIED Authority tV tJ D l '1 Obs n i oeauation ponla oh waa ot wh1 ot oonatdarabl •• tho w tl and tl 1 hoaorrhas• were c01110 • llleedine into t t • inteotl the k1dne '• r r in tho nil ca a Q In oevo ro onaoo tho loukopen14 lod to lowered roDiltimco to 1ntoati1on wb_ich mu tnllond in 111 'ey caooo _b y i0p r ding 1ntect1ono in the ·r outh sr4nnl-007tie nng ne itb gonarone of the lips tonrnio ond ooc401onal ' ot tlio pba Doath tu ttmao cases due t4 a co blnation of tho of eotn ot annem o 8 U'o reo ched a 1ntect1 'Ori tb 1n about tl o a ooko end h · In tlie loaa ooko io rutbor d t 'ioult 1 7 oa · ea ilhotled ep1lut1 u otbor Bhowod only nitootaUono putoohlao or rotirial bao rrhOf OO or purr uric ro loukoponi • 80 CO ll ¥ D cal team huvo mt qUito docidod upon ha al ol torle tor a dJe no 1e of 'ntd1at1on o _ss in tb eao 1ldor casi o quot _ bela ca y bG ohanaod by o obanse or tho t sureo in thooo orttorta o o mot tluu eo are avadlabl but there aro o few 1no1dento which ive a ralrly oo4 £' lid• to the rndiuo 0£ •tfect ot t ho croups ot 11C r ars froo otaJd Ula se woi t ork1ng in t bo open but acreenod bi wooden tilild1n _at J600 tt t'ro th aontt'O 'total od 190• ot hOli ei • l tJtvdnin 192 d1at1on n re r than 95 uboo u nt - '1 d fro the erroota or I Authority II ND Jjo 1 Ii n oo r tlult - J le ln tho o n th et ctute or radi on at rr------DECLASSIFI ro kUl d im ed1Ato by obrlo Ot U Sine the bu Udinr o omo oate to ho 4tQupc o bad ere nin tt a SO e dlat nc abou't 40 DO ft hare 1• - full expoa 1 port nnee elDCe it necea agp n t 'bontir • Tho edical section of the Joint Co l o have dovoted COTIOomin tha ahield1nc orr t o et ing GJCDot dota ct of T r-1 UR t pea of buil dina• Thoiso dat are not -et COIIIJ l te · nd cam ot be pro sont 4 int WO r conoerntn th dagree ot bu1ldt naa th t could be on oru w ro people 1tt n • t•• thority · OM •• th qualitativo atate ionts cau be de 1 lding aftol'ded by different 1-yn e of evan rcrl7 aublltantial W®den bou••• aiw Clc tblns • no protect1' n that __J atod in the cubJeot •hould coe th final report ot tho 1ca1 S4tctt on - · ·0EcLASsiF1Eo ere but anyo be d t eo bJ' the rathor erode •lde oe of protection obaot ' V t iona 1nat th ro aubntantitil ret ntol Cod cono roto cuildJ na•• veral tlooro will tic t o illu trat 1 NND-11 ObS _ __- -- ___ -_ a _ -_ __---- - ' wmwmal b atronc' throo-•tocy rein fore concrete l uildtng ot tu- otl'l ct uro exc pt liight doim tho roo G 1 Jriiorm to havo bean 1n •lJ' o buUui •h• have boen lono COl O or hoce us ldnd and 17 taa killoJ ' bu b ant dl1tort1 n lding ie onl J 700 feet troa u i Lum thore t ' 1o not knonn llhettor t t'l aQD o tr Ot'O ruu l- or n a o 'burne - • ' Cr oc HotJ 1 l tor ot theao n JJOt t- he 12th end 2 rd ot d Ot the 2 ' t ectr 01 go o r o rol lUbly al TiOF o wm-wo rs abtoldllci bf oll tbo tlooru in tho building boen ttnl reyo tht'O 18 lnehoe 001101 etl or or plalt•r - 2t inohea of cind•r• in atddition the n lcQ rt g U'SU41JW - P» 14 D U2 ot coner et o ' cb noor 5 tnohoo ot ooncl'Qto l t he J 4 a z - h Mmku inch of t11 • fhf o to la t1••• 11t017 rolntorce conCl'Ot• 1ldiftg a11 u t cl 2100 feet tro O i o or ti d 1af r1bu t1 t partn ot th rlo r• t bati ••r tul 1 ot CAt't laltt id tho cac ualt loa ciu• tu tho upper atollla th• 041Nftl 1ou 1n thu baa• nnt n on th t t t 1r4 fl f -·--- - DECLASSIFIED I I _ ity _NND-11oos 1 A eta11'd in r•l ation to tho oh1oldttd inohea r 11 t tt ore ro dist nc ot 2600 -n t'roti a · n thn h tho oart b ov r tLo couth or 4 4 s 9J2m¢u 1 ig on o tb1 aubj ot is iolng l - _ by the Jos r i Co 1dn1o and vl 11 bo reix rtod ' J t n lntor J vor brie out ot the f1u4ingu to U te U'ffi - nt 1 0tlen - ho Al l pl'G rvlv cl within 000 £eot or tho '- boDb vo Pl fl ncy tra t 3000 •tl alacen-1 e tro '2 to t 6SOO r 10 t These have 1 on ot • ntba rro 11 sta a ot pro 11 tho t ' bD d p _tUN 1J1ranta tboi en 6500 to 10 000 t t about J 3 ot Jn • arent4 DOJ llal cbll ren ir ·0EcLASSIF1ED 1· _ _yutho ity nt ha r nt ttor II ND JjOOS'l _ _ _ _ __ _ _ - - - - ' - - - - - - - na V t counta or co J leto n Jamlo Tho 'f l 1 t1on on J'U' n tlon 111 not 'lana re boin · produc0 P'J r th hent no obvious rt on to t oh t f'or ti 1 C 1 Dol oto t l 8 be to o 20 r n • or ca in 'G··· DEcLASSiFIE thodty 1 1 tJ D 1 I lt 1 1 vhlob ct1on 4 2 9 r to l o it hutldin 19B1on t ult rt that f _ ' aDUaltioB elao por conoid bl l po e1blo to aetom1 G olj- 1 b t thoi e wor_e we co v1olontly wit • re1110vod ·b r t'lying debris or mt eh to hob oncauntoi• the h1 h volccity _ iti ·iluo rn uir da ·o · to d 'tblo ®rt f · u4 P atc l appo ro though the Jupn ntie houuo ct ot bo 4opiaoli a Uc bt lt lus■ hoa root ti re nd h ov l tbol 'f'OOf tili t- l tl1 ccount for tho htijb 1 n11ldcmco ot • c nctar r caaualt1 Qt addition -c l toi-eod cot o to bi dldiuaL'I ur- torlcl 'ffhich could fal t hero • tore lath d o na conw ry • pl a ta 11 n I d lAt hl'l ln d ir ----DECLA SSIFI II Authority v ND fo I In notabl th• unt or tocl oble In t eu t utldiilio a tt na • r cal hUnfl on cotitparath ly b rill o th O• noiote w nor bo b '1 l rrta broucht 4 mn tat £0110• d ln • 'fho pro ucti n or t' l A tho turning r lrod no expl - urn roo tbilt i ollo cu tian t inf'o in ful 1 • d d occur at diat ncoa JU P to 10 000 teat f'ND t o b that they e o not co 1Dai nae r ooaonc aey wn1CA1 injuri nlpid ·t re bilrne th inci knc o'£ rlAiD Luri h len p1dl v a 1 u J n at tonal t po od that th 1r 1 xto n l 11 i ob rvor et te'1 t d r oir t n t oir intom 1r o pr tru i G or ruptUN in t Y n tn t l•• t t n to ide J c 1 1 t ·od o Poi c l to· l •• amt to lc ok a i t t J y had cu a wn1von ho l e l r · ioh li to p rot or injuries vo hock f1 M lo ha ori dMned on out h re the d a in tboa in oo ot 0 Ho ital n to not kn It ie 'lihAt t ot oi lrurna Auat oi or t h J'OCOrda or 1080 patf enta r i tti out tl•nt c11n· o at llirocll - ·- -_ - DECLASSIFIED uth rity -- tV NDq1ODS th r wlta ot· $1 on th so 1nc into tho£i witlrln 0-1 1 l-2 and -3 d l ' C he c U e oele cmn derod 1n th • ble Th N th Ch dl r 1 di Qr CG t1CU J• -O 'Wh ch 3tt9 i • ' -1 Ot th HEa x 3 5y tt l t4 t f BIEUJIIBiiT4' r I I 1 pidly t r diotru o ot r 0 1cr u c • or to t jur 11 v t i1 en t£ re In cono ldorl n th1 t blo it 1 i r1curoo ero not re nt ot up of t th • thio rt nt to roe the op ulat1 n in ti nta fao t h s no t tilt ct lon J t n tho 1 bl fJ cti 8 re A llliJ bl rho l pol - -DEC LASSIFIED Authority JV fv Di 1Ob5 1 oftic t iolal t'igu_rea '5th ucUuto deaths te is di 1-h t r icu t h lf 'Qnlnj · lt t C fl ' 'bo -o toun ti tor d U and centH d l jdios 1t not t lentifi d II di•• nev r oount o Wont field a he t'l m n ror i ju rod nro robal l Jr 1e to· 0 1 c ed NI nt to dla d1cl not Co 1 1101p1tnl lt 1• obvlou th at ot no value 1n atu I I --DECLASSlllE Authority Tho ot the bc plt OU t 1a b 11 vcd tt t t· r ri tif1ocl t tV tJ D I 1oj§_ I 1 11 •• oa8Wllty f 1 re or tho lothnllt of tho l at kt 1· ucs o hi 'Jl coed t o bo o t • i tab • cub cct tbo f•t• l ol t rot l c n m a d roconJ fnto • Tb etro -t to preeout t fr d1CAtc r at l1tlj- l data 1z a i cac chi'lA Nr 07'0 oretin1 ua into i X OUp md ac ttertd thro lglmut th clty doi o cy fe V or t uo ro ct lly 1n ·cl ool lfh the b r 11 It ho portton in tho pen i to b to Ali · nfl l lin b1oo io ignore hora wt re coneorr od 111 bo 1n- at1 tad ror t Tar oua YP ot b lildC ntto 61 rt co fro t tho 1W croup · tho Joint Co la ion Tho c ntt0U tod ntrJU lta 01 1G Sn ul1ID2nn -1 3340 traa d 39 0 371 0 1626 1-1 5 24 9 3 1 240 1 -2 1260 22'1 22 160 2-2 5 5121 14 1123 2 s-3 2314 0 37 t • DECLASSIFIE - uthority ll v tJ D 1 ObS n11cote sJ l galtb r 0 1-1 5 1 5- 27 z- - ·· 5- 110 2 6 11 I 2314 Tho Ce oua 'ttieo azs aokod to tOffll int no kilo t'N Widtt h1do tllo popul ti n 'f the b' ut tl J lnt vh• •O tho w1 t air d lar S5 000 11s oo ooo • U bl tho l71eu n• an t lti Ii to oort U t1 o 1'1' n ' t t eu to DO at'le th t y not l c3 tJ uu 60 000 ro ttu u l O 00 r 1 b tJ roua e bo Ybua o r tho ro cillod l tt t likc l i1 fiUW O 'bot 320 000 we Pl• th1ra or ro 1 jurod Th ottic r - - -- DECLASSIFIE I Authority JV tJ D l '1 o It l J en 25 761 21 174 ver a• boto re tho ti U re or doatbs 1a the nu mr o vort l 'iod doa tho ob1 Jxed fro tho Governor or t ctWll deaths rofecture - a I • • The ff l urea nr lnju ntd 1a for tho • otuoll b tpitaliee4 UtSlde It ia uoul l'l c noludud in dical c rcu Loa i bat then approxitiato 40 O kil cct lld t loast 60 ooo inJurod b f t 114 bo b ln ordor to taet t ta on chool chtl di'on at U-Oah 1 thoy the t' ol owl pul otlon ot procc W 'O eppl1ocl to J aurwe ere obtair aaaki 1 tor tl» re--rata 1 The tho 24 co aolldat o lock as sooiat ion a ot' 'b ullt-up ar 11 of tl on 24 unit 1 er J OI lntinn d1otr1bu throuah tbe thauNncl toot annuli oocupie J t n tho ratio oft to oocup t tch t be ' aro a lonr 1ndeX being elwn • kno1rlt to b - o t n t blnl y popu1a toa In tbi• 1 an eatiate or t e 41atrl tion ot po ot lned curw fit ion ln thousand rot to tl1 biet o or t a nub idiar l hlato rtna• • date on cted n ooo - 9 ooo 9_ 000 -10 000 tt r ea that It will boo l'ldalf accoptod l belt on tb1 th mt with a tigu ot 40 000 ktlled ho 1 11td1ool e uthor1-t t a la atrU1n · I 1 fact • otl•t• be b 1ihicb e lMl•• calculated tro populatt ll Md population 6nd pi etor apld ot known f or t O O doad pN- An4 pollt-nud ncud This wen ' d o e•t lllO th4t the iU roehillla ecbool cbildNa rJa1 l vo included a diaproportlonate lei- l n o open o WtlJJle 1n th t latactory for n 'bor ot ind1•tdual bl c ae oola ttor us at oro 1 C uld bo tooted 1 t t be1 _ - lf ---DECLASSIFIED I IV ND11 o 1 ---- -1- Authori g-e1 tral t1t -mwoY•l' io o o abl• undollb · _5 • C • # - t z x · tb• Tnblo that in NtUld u -- aunda C a vnlWi bi ·· ft rat e lr x 1 lnt •t e littlo '_ Ji °'il UJ'OO I at u bet ox- C or ' 'CAJltNi • d J 1lletl death · The utandaroi - ra f rolol thea tieure th1D win 10 000 • ot y oople 1tl Br tiah oubt t ontal bouoo t tho otando rdizod illed in Japan end rate of ne cto sio 0-t ah 11 r o ecda 50 000 thts Jto ndnrd1ud ltilloci ri t of lUod 1n en ot population P per t ncnt - rout hly l roro t th dtnalt tlNt in · 1b1cb t c ·tho t lot that n o to iio bo ib on c be • ot84 to J rotiuc e 1 10ro -tbrm 50 0 4o4d Thi ia probobq th8 con itut ol e ia tho OXJ»etttd n l'lJbor ia un fom alld o do na ty 11 contral Iond-on o vo or ·· i portant fisure • have t al lmldon unt lch th1o ltepor-t It ao paros vi th a t11 1indn1ilirmd ktllad rato tor • po ola- tion halt bi the l pen and halt ln nritilh or bout JS per ton th • nui• ua or ton do d por aero in t-he heavleet bic · diAl ' rudas on tlw dena o P P- ll toct areaa ot ta wur ond ' ok to pro t•d ltY 'the ato 1 c or prat ot ion • ' Authority t t ao foua dan or blmb iu in prod c1 £ caou lt1oD ho proble cr un ullt1es 'lJl perttaul r la esco 1tlo1U ll1 cn va a ncl d1tt'1cult r -· DECLANSSiFiE D l 1 It to oloAr tbo t the fl ff uaao rend• l tt aVONCo racibu I ropo 1r aTO re o na diuo 2 to 2i · a1loa ' • ohall coneldar an everane r ltiab ur n aity or about 15 per acre th a b ouat na · r d • poJ t1on WcoS ty of ab ut 45 per ere In ouch an a-ea t hen th nw L er or bouoeti deooltabecl or i-oqulr1n• do· lit1on •• the l OIW t ot t bo det M th cond1t1ono h1ch •• nt•wio4 ll d ibor ot bouae■ ton or oiticl• tcnalc bo be ap rox1 n 4t1ir1nc oon 1d r•ulo ropt ir in o o 000 be uld • n or d t r ipor4 QV-l t J K D ll 1tuto· a about 50 POO ot or wu d die· u d 1ro five ill • i dte t o lcoaa they • vi rid t cc l• ot the dianstotJ ln 111 vore __o inoicwnt in th• wa r nr1_1 1oh o1tiea ca to on LiYe rJ O l n ur obaer ion o facto17 ahodm ohow _ uee ooctlon 2 t hie no l t otoey truo o ttect a ro ld od la t o 1 nchu tr the C t nal incl chinots aro not l n Wohl - due J otlon 3 2 9 nc1llaey cauo • vhich or tho i ago f - to DECLASSIFIED A uthority v tJ D i 1oos chino tool • 1 oibl o ln • out t i thu rrt r1a lo u can i tit 1 1 JnP4Jl tor t gr t r allin ould be · tho buildin to of wood ich •o bave c lrclwo att ent ir -n at tho honp1tal WU dingo in ·a o voidod -·1 n I eucl 'bul in c·nn _ 1th t w in i rticula r re bJcct to lllll c a nA3 fat· in rt ta aoo s cti n 1 3 Jut thy tf ord t r prot ct 1011 tt n ott1 r typoa ot eor atcuotion chould be -u cL t o to Gll publio r1enee or oh u1l n ·a in Hirooh c uld a c nvartc into halt r r tloor 1 Lt o proof Yn orract ot lo rtn the ot a 0 tnii ibar of£ ctor• culatloh h N o of f'actor lob ia a 01 ibl to r - -DECLASSIFIED - A tho ty r JQ 'f j 1 ----------------__ CSi - i 119 _• - p x tnltr 1 public corvicot nt 41 bnret at a hei ht up _to A oturoo aho 1 thiit tba · rOTI b ot radiua ot lX ut 250 100 rt cauoed t• an ot c oaion o u xperi- or 001 10 r et 110 wouHl outrtco w c 11ti t er r ip ct eortaln'b' ov r tb co tral area or dopr a ton ld de cl upo tho type b L Ll' -' ey tNoturo vo- u t o little treotaa atructUNJlly boyona Jnm r d 1'• t but pl ate glwtera p sontinn fe• aono1 1erable latoral th brtd a be c t 6 2 2 •• B1Qsx1 s r -·- ti ll o t diatanccao of fillet ttw - IE Al r ft DECLASSIFIED i r thority NND 't'f 00_ 3_ oil• or re 1 ••• Ohat1tr•e in blaot effect •• aa tbo r l j I ot lt or te round Nfl ctiou daali'od JO Orlty J knomt that th total area CG l 'be inc pq int ·ot detoa ti on 0£ 1 l Thia 1 a aubJcc o h thor ••t t YOn could likoq to its lnor 6 2 3 qdia 19D ot Bfleot • iatrib-Jtion e tho btaia Jt of d1 tion or Id rid r chea a 1 inc t ro rttonal tot ot • lt can 1 ftr r re• of misbt 11 y be u nm tnot lto 'llhol ly 11 • 1no a ncl hat to h r• CJCliUJW 11• aero or on1 n rA J n t bo inner oirolo rrect iviJ - 'or ple ro t tl - lor -··wUl ro l -DECI ASSIFIED Authority _ V ND l 1 I • t o ra11 rr t I l cfi'ec1 • can r t otn i1 rolwr conJo pri I ¥ fiaalon wi - 11 t n - ' li - active c rta_1 n1 buil lin30 would b 10 1111 or tlOar cro 1nd z would bo ' -XP t r ·• iod of uar-e atraetcd 6 3 » 11 111n1 loJ ant tn th n1r o or atonlc bo--lm ip to to oxpuot • I 1• n t cle r h w t nee • irlONA G 1 ould bo l tm't or in bo err ota 'rinlld h vo m oup1r1ocl in or 1at1on on c le otJ' 'octa- for ouch 1Jlr30 oxploa1onr beol ot1c 1 a bove r flpGc1f1o C nn1durGt1 ona lfo it ratr J' o 6Cono 1c l• it1 t toriat WO'Jl _ 1 t ot tho el • bo oo 1 uraa an obi onod 1 arpl bo tro o •• li • c vor atn b corspactneacs qf tho are or ·dem rttetion t1on would be cor NlopQn-Jir s J• ' Ore sori ' UO I I - A dev lop 1ont #b Qh 1a p cej t• bo concsldo_rocl 1o bat bly ot F notrut1nl b n · Ficuz-ea have · qalv lent to o bare harm o at lea t 3000 ton o r f ns and poiisib y 011 much co 101000 t on It hllm Gno tlillt 3000 tOll i • I io e to•1t tho quantl ty • • lcb 1a u ught to h deton tod in ' the rocont cxploalon or exp oat re A urvoy of n unte •NUnct a m unHio1 i sto ro near Dui 't Jn - n•Tront r a tl o t'4t an carried ut o 900 t't in diu ct 1 ruw tr t1 oooaron ' th e plo 1on n a ut 90 ft • would • nr d iuc sea 11 ort' OJlto RE 2 4 our publta1 ied ca tod 1 a 1 tely u nP J t--O - esti i 1t e ata O JQJ t t'bich WO ho to 61 2 • oa wnin r thit a bo u ot or cr ato of thl l O ft nd itD depth woul d pr bab # m coo4 100 tt aize ou ld vo oont int' d inttiolly nourl hich uoul d be diuporood OUl rO lnclin re • 2 ono1 0 O tono ot oil_ or lt 1ri ver 1 n· o l lilpCJ ov r th fh• orreot on r u'b 1o aor 100 ndon Tube• ou d 'to 1000 tt M tb• point or expJ ouion to o r-l don 1 th· o diatnnce wr da flJ' l rio UiJ at o o ld e or d n · c ord i- nd 1ry fiooi on · • at Burton- m - 1' 1 1 ea tho ••· · t · to co o blo Gt bo ib lrlCht ba ioro In e43nar4l than while vo ·aould not ro ard tho pon trat i nc bo b a nacea rily ho j terr d wo«J On 1to uae woul tt cnol1¥ Uely in 1·oa o tho no -vicca tht t d1f 1culties ot iaorP rd zrtio n ot pu bl i c l Ol loue W rk orwir dzo tion 6 4 otT · 1 rl 1 1C I' tT - 'l'b o vorall p1cturo lthtcl thosu 1 r1nc th r1ace J n ttl lck ud dcvclo ti 111·00 re 11 Tho PQ1nt ' haa be n it1 crc ni J by th aaure o· 1 ot t do lb 1'e pcm aut crroot of 'tl o bo b o otion 4 4 that ri ••cot 'lrc pr nto of tho uerioua now problo ey AUd o conuo ry whiob tho 'bo· b ro4ucoo plan tin a us firo r alst«mt buUdinc on 1 tl e ore sniutf on of an off c ont fir-o a rlvo on a lJn •go IO l• aro iisport uit taa1'o in r ll thtt po1ht th 1 ot o r1tiust o poet ·»ECLASSIFIED Authority JV ND- 1 oos l or tl ba 1 t n '• in aoctlon 5 that b lb ia t lle nw wur of oualtl ot 3 i lfRfElf f- I II ND JjOOS1 I DEcLAssiF1ED uthocity