NAVAL MEDICAL RESEARCH INSTITUTE NATIONAL NAVAL MEDICAL CENTER BETHESDA 14 MARYLAND NH6-l All NMRI-160A EGH jt 20 June 1946 MEMORANDUM To Lt Colonel Leigh C Fairbank Corps of Engrs Military Operations Division Manhattan Project Headquarters War Department P o Box 2610 Washington D c Subj Measurement of the residual radiation intensity at the Hiroshima and Nagasaki atomic bomb sites report on forwarding of Ref a Your memo to Capta in Hakansson dated 17 Jun 46 · l· In accordance with your request contained in reference a the subject report and a chart show ing the Nagasaki bomb effect area are forwarded herewith 2 You will note that this report has been classified SECRET by this Institute A classification to roP SECRET was considered indicated by Captam George M Lyons MC UENR and the matter referred to the appropriate authority for action No information on its f fnal classification·has been received 3 Acknowledgment of receipt of subject report is requested Z l1 t o ----- - 1n MC U So Navy Command ing Encls HW 1 Subject report l 2 Chart 1 3 Receipt 1 DEUSSIAED - Authority ' ·· 'J ' 3 BY L ' a C NARS Date' b • NAVAL MEDICAL RESEA H INSillUTE £u O £ L £¥7£ L D ffe L 1 BETHESDA MA RYLAND - MEASUREMENT OF THE RES DUAL RADIATION INTENSITY AT THE HIROSHIMA AND NAGASAKI ATOMIC BOMB SITES -- DECLASSIF Authority rvND'¥1oO ss_ • • NAVAL MEDICAL RESEARCH INSTITUTE NATIONAL NAVAL MEDICAL CENTER SECRET ------ BETHESDA MARYLAND 16 April 1946 D ASUREMENT OF THE RESIDUAL RADIATION INTENSITY AT THE HIROSHIMA AND NAGASAKI ATOMIC BOMB SITES NMRic l60A SUMMARY 1 Measurements ot the residual radioaotivity at the Hiroshima and Nagasaki atomic bomb sites were made by means of a portable Geiger-ltfuller counter during the period 70 to 100 days following the explosions Most of the measurements were made at Nagasakh those at Hiroshima being made only on the 87th and 88th days following the explosion there -- 2o A series of maps is presented giving the results of this study A characteristic feature of each ot these explosions was that two distinct areas ot residual activity were produceds an approximately circular area 600 to 1000 meters in radius about the point on the ground directly beneath the point of explosion in the air 11 and an elong te bilaterally symmetrical area of residual activity starting approximately 2 kilometers downwind from the hypocenter The former area of residual activity is believed to have been caused primarily by the intense neutron bombardment of the ground resulting in radioactive isotope transformation of several of the elements present in the earth The downwind area of activity is believed to be the result primarily or deposition or fission products from the radioactive cloud whic is known to have passed over the area under consideration 3 Equations are given describing approximately the intensity or the residual radioactivity as a function of distance from the explosion center for t e central' areas at Hiroshima end Nagasalcio The intensity of residual-----aotivity even at the hypooenter of thes 8 areas s was round to be tar below -· -the dose necessary to produce perceptible physiological ef'f'ects The -- highest values recorded were 70 to SO mioro roentgens per hour• ___ 4° A striking difference as noted · howevers between the downwind areas a t Hiros_hima and Nagasakio At Hir shima the maximal residual activity observed in the downwind area was slightly' less than that in the cent·ral area At Nagasaki on the other hand downwind near the small village of • • • ---- ______ Nishiyama 11 a maximal value or 1080 mioro roentgens per hour was reoorded This _value appr_oaohes the magnitude of the maximal tolerance dose of 4200 - ___ micro-_roentgens per hour o It is believed that the difference between the downwind areas at Hiroshima and Nagasaki might be due to the fact that a different type of bomb was employed at each oityo 5o In order to determine the effect on exposed personnel of the relatively high residual activity in the Nishiyama area 0 blood studies and case histories were obtained on a group of' 60 inhabitants of Nishiyama 100 days following the explosiona The topography of the region is suoh that the village was in the s adow of a ridge with respect to the explosion proper and yet is in the area of maxim al residual activityo The blood find ings and histories of the inhabitants were normalo 60 A group of J panese investigators from the Kyushu Imperial University made a similar study on the inhabitants of Nishiyama three times during October 1945 on days 53g 67 0 and 80 following the explosiono It was possible to study 25 ind-ividuals of their series 100 days following the explosiono A plot of the oomposite data reveals that a significant peak leucocytosis oocurred in these individuals 70 to 80 days following the explosiono A mean leucooyte count of 16g200 per mm 3 was observed at 80 days Thus significant fJ al though slight P phys iologioal ef feots were produoedo-- _____ It was possible to estimate the total integrated roentgen dosage received · '----- by the inhabitants of Nishiyama to be 56 roentgens• It would appearo therefore0 that this quantity of radiation is capable of producing a measurable physiological ohangeo 7o An equation was derived empirioally giving approximately in ·roentgens the intensity of the radiationg producing radiation siokness released by the explosic of a plutonium bomb of the New Mexico type as a function of distance frcm the explosion The radiation considered is of three types gamma rqs O fast neutrons O and slow neutrons The equation followss I 2 o72 X 10 9 e 0 0 Q015x 0 X_ 10_e_0o0078A 4o S4 X lQ9 8 00o00237X _ __ _ __ 10_ 2033 0 I ---------- ---------x2 x2 gamma rays fast neutrons x2 slow· neutrons I is the total radiation· in roentgens at distance in m_eters from the explosiono The equation is valid for distances greater than 800 nieters p and gives low values at shorter distances o A table is pr_esented giving the radiation intensities oaloulated from the above equation for the Nagasaki explosiono DECLASSIFIED Authority NND ¥100 i6_ • BACKGROUND • The atomic bombs exploded• at Hiroshima on 6 August 1945 and at Nagasaki on 9·August 1945 liberated tremendous quantities of energy both mechanical 0 in the form of the air blastoand electromagnetic · in the form of thermal and ionizing radiatio·ns·o In additiono large numbers of high energy neutrons were released which f-o rmed artificial radioactive isotopes of elements of substances in their paths o Isotope production is also possible by gamma rq absorptiono This o however was estilliated to be· fi everal orders of magnitude less than the isotope p_roduction by neutron aptureo · As a consequence of the explosions O a residual ·radioactivity was induced in the areas of Hiroshima and Nagasakio The residual activity probably · resulted from one or·both of two causess a the production of radioactive isotopes in -the ground materials by the extreme·ly intense neutron and gamma ray production incident to· the explosion 0 end · b ·the deposition on the ground of radioactive explosion products 0 eog 0 fission·productso · · The purpose_ of this investigation was to -make physical measurements and computations of the intensity and distribution of the residual activf ty arid to determine its -relation to possibly harmful physiological effectso 9 METHOD Measurements of the residual activity were made by means of the Naval Research Laboratory Portable Radioactivity Dosage Meter employing a selfquenching copper cathode Geiger-Miiller counter tubeo • The· counter was calibrated' _in terms of' micro-roentgens per hour µ r hr against 24035 mgo of' radium enclosed in a platinum capsule of Oo5 mino wall thicknesso It was assumed that· l mgo radium through 0 5 mm o of platinum produces 804 r hro at a distance of 1 omo · 1'hus the radium standard used to calibrate the counter was assumed to produce 204 5 r hr at 1 Olll• The radiation intensity at various distances was- calculated by the formulas· 0 0 1 where I is the r hr o at distance Radium C through air t 15° ·c x I0 m J L m CIilo 20406 r ro 4 0 54 x 10°6 tor gamma radiation from 0 The counter • was constructed by Lt jg Mo Eicher H S o USNR under the supervision of Dro Ho Friedman and his staff at the Naval Research Laboratory Anacostiai end was modified by Captain D Lo Collins o AUS ot the Manhattan Distrioto r-----»ECLASSIFIED I Authority IVNJ ¥i 056_ 0 • • Meter readings at various distanoes frpm the standard were plotted against the calculated radiation intensities for those distancesg and the resulting curve was used-to oonvert meter readings-obtained in the field into µrl'rlro valueso The sensitivity of the counter varied from day to day -so that frequent re-calibration was necessaryo· In general 0 however 0 the sensitivity remained oonstant during a given sequence of measurementso Dur ing use in the field the counter was placed at a fixed di tanoe of one meter above the ground by means of a suitable rigid supporto A f w measurements· were also made with th counter 5 om above the ground Whenever possible the location of each point of measurement was aca curately fixed on aerial p4 to mosaics of the area being surveyedo When photographs were not -available 0 positions were plotted on mapso Adequate photo co erage was available for most of the Nagasaki measurements The- _ survey compris_ed about 1000 individual measurements 900 in the Nagasaki _ area_ SD d 100 in the Hiroshima area Earth samples were collected in many locations for further study in the United States In addition to the physical measurements o a brief evaluation of the physiological effects- of the residual radiation was made by obtaining case histories and blood studies on some 60 persons resid g i the Nagasaki area of activity but who were not exposed to the bomb explosion propero RESULTS The areas of residual activity at both Hiroshima d Nagasaki were found tp be of two fol IDS I a well-defined 0 roughly circular area about the hypocenter of the explosion 0 and a diffuse-anq generally larger bilaterally symmetrical area _some distance downwind from the hypocentero The term centerK will denote the exact site of the bomb explosion in the air above the gr9und 0 and the term hypocenter will denote the po·int on the surface of the ground directly beneath the explosion center The geographical areas of residual activity about the hypocenters will be known-a a the Hiroshima cent r area and the Nagasaki center area 0 respectively The geographical area of activity downwind from the hypocenter at Hiroshimao which exhibit d the highest radiation values near the village of Takasu 3o2 kilometers west of the hypooenter will be termed the Takasu area The corresponding area at Nagasaki began near the Nishiyama Reservoir 2 7 kilometers east of the hypocenter and its area of maximal intensity will be termed the Nishiyama areao The geographical distribution and intensity of ·the residual radioactivity at Hiroshima and Nagasaki are shown in a series or four maps Figure 1 shows the distribution of the activity in the Hiroshima area and figure 2 shows the distribution in the Nagasaki areao Figures 3 and 4 show in more detail the distribution of the activity in the N asaki areao figure 3 stressing the Nishiy8Illa area and figure 4 the oenter area 0 -·--·»ECLASSIFIED Authority tVND ¥ic 05S_ • It is to be emphasized that the values shown on all of these maps are for the dates indicated and that the activity is diminishi ng steadilyo For purposes of comparison of time periods the convention is adopted of express ing time in terms of days following the explosiono In the case of Hiroshima this will be given as H the number of days p and in the case of Nagasaki as N the number of days o Table l is giv_en for convenience in effecting this transformation All dates given in the te etp unless otherwise noted 0 are Japanese time • As s_hown - 1 --- figure 1 the central area of activity at Hiroshima on 1 November 1945 H 87 exhibited a maximum intensity of 81 µ r hro and was roughly radially symmetrical about the hypocentero The displaced area of radioaot_iv ty near the villag_e of Takasu lay ownwind along the path of the prevailing winds_on·the day of the explosion and probably represents the site of deposition of the radloaotive fission products formed in the explosion process he high l3 1 intensity i -ecorded was 42 J Lr hro Thereforeo · -the residual ac ivity iri the -H iroshima area as a whole was far below physio 1 logically significant intensity• _ · O In order to ·express th residual activity as a function of distance from the oente r Q oh of- the are ·enclosed by the intensity contour lines was measured with -a planimeter and a mean radius about the hypocenter was thereby obtained It was assumed that the residual activity in the central ea resulted largely from the neutron bombardment which occurred at the ime o the explosion and that the activity induced reflected this neutron 7ntensity As a first approximation it might be expected that_ neutron tensity would follow the inverse square law and_a so that som att nua t1on would occur as a result of passage through air h relationship of distance and neutron intensity 0 and hence residua activityo might be expressed by an equation of the types I 0 e JLX et I o --- 2 x where I 0 is the hypothetical residual activity at the explosion site properp and µ is an attenuation ooefficiento Table 2 includes the data from which such an equation was empirically derived for the residual activity in the Hiroshima central area 0 The equation followss I s 8 -Oo00276x loOl x 10 e X bl 2 2 Where is the residual activit r hro and xis the distance fro the air burst in meters o A height f meters above the ground w assumed 1 for the point of explosion so that distallce from the center could be computed from the distance from the h ocentero The intensity values cal culated from equation 2 YP ·th those actually observedo and attenuation coet'fioient reehfaildrly well ' h that tor the neutron intensity as a function t' di o r-o s · ou agree w1 O stanceo sfo DECLASSIFIED Authority NN D ¥1Qoss_ I • • As may be seen in figure 2 the general pattern of residual activity at Nagasaki was similar to that at Hiroshimao The central area of activity at Nagasaki on 18 October 1945 N 70 exhibited ·a maximum value of 72 µr hro and the extent of the residual activity in the center area was comparable to that at Hiroshimao An area of residual activity displaced downwind approximately the same distance as at Hiroshima was found in the Nishiyama area in the direction of the winds prevailing· on the day of the explosiono One important difference may be observed between the situation at Hiroshima and that at Nagasakio The activity in the Nishiyama area at Nagasaki was conlD siderably greater than that in the Takasu area at Hiroshimao Many values in excess of 800 11-r hro were obtainedg and the ·highest value -measured was 1080 µ-r hro This -difference may in part be due to the fact that the bomb exploded·_ at Hiroshima was u235 g wher as the Nagasaki bomb as p utoniumo The activity in the Nishiyama area is almost certainly the·result of fission products deposited from the cloud formed by the explosion · The weather at 1100 on 9 August 194·5 at· Nagasaki was clear and war wi h a light west southwest wind of a velooity of 3 meters ·per second 2 o Residents in the Nishiyama area tell or the cloud passing over the region and droplets of yellowC brown liquid falling af'ter the explosion· occurredo A range_ of hills is interposed between the Nishiyama reservoir and the explosion hypocenter figo 3 o and the east side of the Nishiyama valley is well out of the direct line from the explosion centerp yet relatively high residual radioactivity was observed in_ the areao Furthermore definite traces of resid al activity were deteoted on the Shimabara Peninsula figo 2 some 20 miles west of the Nagasaki hypocenterD and the Japanese reported traces of activity in - Kumamoto some 50 miles w est of the hypo·centero Figu e indioates the relationship between the Nagasaki cent r area and the Nishiyama area more olearlye It may be seen that at the tune of · measurement the two areas were distincto The 11 µ r hro contour represents the lowest activity which was significantly different from background by the instrument used in the study Aside from the large dif ference in intensity or radiation noted in the two areas certain other differences were observedo In the center area no differe ce in counter reading was deteotable whether the oounter was held l meter above the ground or 6 cm 0 above the groundo Furthermore$ the counter tube was equipped with a bubble window for beta ray measurements and only a slight inoreas in meter readCI ing not more than 5 per cent was noted when the bubble window was exposedo In the Nishiyama area on the other hand the meter reading was almost doubled when the counter was moved fromgl meter above the ground to within 5 omo of the groundo On exposing the bubble window the reading could be inoreased by approximately 20 per oent thus indioating appreciable beta ray activity in the Nishiyama areao Finally it was observed that some variation in radiation intensity occurred in the Nishiyama area depending on whether the counter was held over a relatively undisturbed area suoh as open fields a or over areas such as roads and wellaused trailso The readings were con sistently higher in the former case than in the latter o -----»Authority NN D eJ005S_ 06- • • The distribution of residual · activity in the ·Nagasaki center area is shown in detail in figure· 4 The coutour lines were drawn on the basis or approximately 600 in4ividual measurements in this areao and they may be seen to be roughly radially symm etrical 0 although not as clearly as in the Hiroshima center area The departure from true symmetry may be explained in · large part by the broken nature of the terrain in this · area It is believed that the elongated shape of the 69 J 1 r ru- contour is due to the fact that a hill O on w oh the Urakami Prison was located is in that area Likewise a sma ler isolated 69 J Lr hr contour occurred on the side of a hill to·· the southeast of the· hypocenter - It is readily seen that although one point may be further reJ loved fr m the pypooenter than another poin s the former m8¥ actually be closer to the center by being on a hill 0 and h ce would be expos d to a higher int_ensity of incident radiation As discussed previously for Hiroshima· it was again- assumed that in the Nagasaki center area the residual activity resulted from neutr n bombardment and the relationship or residual activity o di tance from th center could· be expressed as a first approximation by the equations· · • f__ • I f The data from which the constants for this equation were obtained are given in table 3 0 and the equation describing the relation between distanc from the center fUld residual activity at Nagas i follow ·s _ · · · ·_ 1 a 5 24 x · 8 · o o oQ070x e · a X where s the residual activity in µ-r hr• and is the distance from the center · in meterso A height of 490 meters ibove the hypgcenter was assumed tor the center in his case 1 The calc lated intensity values agree moder tely well with those observed and the o and p values are cam parable with those calculated for Hiroshim ao · • Shown in figure 4 are also the-various estimates of the exaot looation of t e hypocenter 0 and thes e may be seen to tall within a re8'on- ble cluster The sight center was located by sighting 111 ong ·fallen tree trunks around the periphery ot the losion areao and plotting the interseottqn o the cross bearings obtained by means of a transit This hypocenter falls within th_e zone ot highest residual activity The JapanelJ e group from the Kyushu Dnperial University estimated the Shinohara center• from their residual activity measurements and the Japanese ·center was estimated by a Tokyo group from triangulation studies of the physical damage These hypocentera also fall within the area of highest residual activityo Ot all the four areas exhibiting residual activity at Hiroshima and Nagasaki only one appeared to-possess activities ot phy iological - ----DECLASSIFIED Authority f JND Mc O SS • • signif'icance 0 namely the Nishiyama area By chance the small village of Nishiyama 0 comprising· several hundred in population was situated a long the west shore o f'· the reservoiro · As may be seen in figure 3 this location is very near the region of highest activityo It exhibited a mean radiation intensity of 700- µr hr1o on N 96 and wa s also out or direct· line or the explosiono In view ·or these conditions the population o f Nishiyama represented an ideal group £or observation ·of 'the effects of' the residual activity uncomplicated by the immediate effects of' the explosion It was possible· to obtain oase histories and blood studies on 60 men women a oliildren · in Nisniyama and a swmnary of' the blood findings is presented in table 4 9 o t may be seen that on 16 to 19 November· 1945 0 approximately 100 days following the explosion N 99 to ·N l02 the blood picture was essentially normalo The mild normochromic normocytic anemia wa s apparently not unusual in the Japanese rural population and this is likewise true of the ·mild eosinophiU a However£ · a group or Japanese investigators from the Kyushu Jmperi l University had obtained leucocyte counts from the inhabit a nt ·of' Nish1 yama on l October 15 October and 28 October 1945 representing respectively N 53 N • ·s7 11 and N 800 It was possible -to identify 26 persons in their series with corresponding persons in the series examined at N 100 · These data are given in table 5 a nd a variation in mean leucocyte count with time is plotted in figure 5 It ma y be seen that a significant peak leucocytosis occurred 70 to 80 days following the explosion but t t the condition had regressed 100 days following the expl siono_ A wide inqividual_variation n the response was oparaoteristio as ___ indicated by t le arge inorease in standard deviation The case -· · histories yielded n further significant findings The temporary leucocytosis at about three weeks indicates that the maximal tolerance dose of radiation was exceeded for ·a sufficient length of time in Nishiyama to produce significant physiological eff'ectsp but that it fell below the maximal tolerance dose fairly quiokly and In the Nagas-aki oentral area six to 12 weeks after the explosionp interviews with residents revealed that a considerable number of them had re-entered· the area wi'thin a day or two following the explosion having been fortunate enough to be aw8'¥ on that day• Many of' these persons had rebuilt their homes and replanted their small truok gardens P and careful questioning could elicit no subjective symptoms that might be a Sociated with the bomb or its a fter effects In fact an almost invariable result of the ques1 ioning w as he voluntary information that -t e truck gardens were oon s iderably more fertile than before the explosion o It seemed remarkable th the average Nagasaki resident apparently viewed the ato io bomb as merely another implement in the armementarium of war and did not appreciate its full -import •·Th s are due Major S 0 Berg AUS under whose guidanoe the laboratory stwhes were made an to w Blagg CPhM USN Mo Saltsman FhM2c USNR J Jo MoManus PhM2o USNJi ·and T Co Lohnes Ph 42o USNR for the actual determinations 0 -· --»ECLASSIFI- in--- Authority t JND fi00 6_ -a • DISCUSSION • In order to obtain measurements of the residual activity at a later datei1 permission was obtained for two groups of Japanese scientists from the Kyushu Imperial University and the Tokyo Institute of Physics and Chemistry to make such observations at Hiroshima and Nagasakio Their findings are reported separately 3i 4 and half life estimates for the residual activity at Nagasaki and Hiroshima were obtainedo The best estimate for the half-life at the Hiroshima center area on 7 February 1946 H 185 appears to be between 180 and 300 days 3 o The half c life at the Nagasaki center area on 28 October 1946 N 80 aocording to the Kyushu group 6 was 70 d s D and on 23 December 1945 N l36 according to the same group 4 it was 90 dayso According to the oaloulations in table 6i1 which were based on composite dataii on 27 December 1945 N l40 the Nagasaki center area exhib' ted a halfc life of 82 to 2Gp days o mean 146 days depending on the distance from the hlPoce_ntero It is of interest that according to caloulations of the· Japanese 3 for Hiroshima the halt-life increases with distance froll l the hypocenteri whereas from table 6 it is seen that the re erse is true at N_agasakio The meaning of this variation is not clear D and the variat·ion y not be realo Japanese estimates are also available for the half life of the activity_ in the Nishiyama area 4i 5 o On 28 October 1945 N 80 the half-life was es imated to be 44 days o and on 23 December 1946 N l36 it was 90 days o 0 0 It is olear that the haltC life of the residu l activity at both Hiroshima and Nagasaki is steadily increasing· as- ·the intensity 0£ the radiation is decreasing with timeo This is in aocord with the well reoognized phenomenon of decay ot mixtures of radioactive substances o As the shorter half'C2li fe components disappear O the overca1all half-life of the mixture approach that of longest haltc 2life component present This is undoubtedly the_ oase 1 1 Hiroshima and Nagasakio 0 The rate ot deo8¥ of complex mi ure of radioaotiv e · subs1 8l 1 oes may be expressed by the general equations 4 -· where I 0 may be consider- ed in this case to be the radiation intensity 1n roentgens per hour r hr 0 at one- hour following the explosiQnii the intensity in r hro at t hours following the· explosionD and as a specific deo£q oonstanto Through the courtesy of Dro Joseph Hotfmano the value for for the downwind cloud track at New Mexico was es im ated at lo2l It is assumed that the same value tor n obtained in the Nishiyama area at Nagasaldo - As stated earlier O measurements at the village of Nishiyama on 13 November 1945 N 96 yielded valuea ot approximately 700 __ l'r hro for the residual radiation intensityo S ubstituting the values for s o and in equation 4 yields the value I as follows s sJ 1021 Io m 7o0 X lOC 4 r hro 96 dqs X 24 llr dq G 807 r hro Authority • • Therefore 0 the time intensity relationship for the village ot Nishiyama may be expressed by the equations 5 or log I 009395 lo21 log t 6 Solµtion or equation 6 for t when the intensity reached Oo 1 r hr yields value of 554 hourso Thus o the-residual intensity at Nishiyama was above· the maximal tolerance dose for approximately 23 days In order to estimate the total roentgen dosage received by the inhabitants of this area o the time intensity curve was integrated The simplifying assumption was made that because of time lag in the· transport of the cloud by the wind an4 for the oond nsate to fall from the cloud o the radiation intensity on the ground at Nishiyama was zero for six minutes 0 0 1 hr following the explosion o and then the intensity rose instantly to its full value at six minutes This obviously is an idealized representationi however o it s rves as an approxima ti no Thus a total dosage for Nishiyama may be computed by integrating equation 5 between the limits of 0ol hour and 554 hours · a Fro this value it ·m·ay be concluded that a total dos age 0£ 56 received over ·a period of 23 days is sufficient to produce a signifioant leucooyte response There is some question as to whether the leuoocytosis represents a primary stimulatory response to the radiationo or whether it r presents a compensatory rise following a period of leucopenia However o in view of the lag in the leucocyte response the latter conjecture would appear to be favoredo The summated roentgen dosage received by the inhabitants of Nishiyama is plotted in figure 5 and it may be seen at the bulk of the total r entgens was received in the first few days following the explosion tfnfortunateJ y blood studies are not available for the first 53 days following the explosion 0 so that- only a tentative oonclusio n oonca oerning -0lood ·changes during this period oan be drawn ata of the Tokyo group 6 concerning the distribution of residual aotiv i ty about the hypooenter in the Nagasaki oenter area on N 140 was analyzed as a function of distance from the center A conversion factor of 1 J 0 lo726 µ r 2rro was used to convert their intensity values II and the · treatment of the data is shown in table 7 The constants of the empirioally derived equation were found to be closely similar to those obtained in · equation 3 for this relationship at N 7 0 The equation fort 140 follows 8 8 e-0o0086x 9o73 X 10 7 I 2 0 X -·---J ECLASSIFIED - - Authority fVND eJOOS -- • • where I is the residual activity in µr h r'o and ls the distance from the oenterCE in meterso In view of the wide divergence in technic of measurement and of the variability of he intensities owing to differences in terraina the agreement between equat ons 3 and 7 is very goodo Such agreement tends to substantiate the original assumption that the residual activity reflegts the original · neutron intensity occurring· as a result of the explosiono To further substantiate this view it was possib e to derive equations describing the intensity of radioactivity induc in human bone and in elemental sulfur as a function of distance from the exp osion cent er at Hiroshimao The original data were obtained from the r epor of Yamasaki and Sugimoto 7 D and these data together with the fitted o ves are shown in figures 6 and 7 o The radioactivity induced in bqne is dtfe ·t th o ture of slow neutrons by phosphorus D yielding p32 by the reaction P3 n y P3 o The radioactivity induced in sulfur is due o the ca ture of ·fast neutro IJP by the sulf'ur with the ·loss of a proton 0 yielding P 2 by the reaction SX' np P3 2 o as The equation for the activity of bone found to bes I 609 SI a function of distance was 9 o0o0078x 10 e X ---__ ---- X 2 8 where l is the number of beta particles x 10°3 emitted p r minute per gram of bone corrected to 6 August 1945D and xis the distance from the center in meters o The equation for the activity df sulfur as a function of distance was found to bes I s 3o47 X 10 6 e o0o00237x -- ----- x2 9 where I is the number of beta particles x 1oc 3 emitted per minute per gram of sul ur corrected to 6 August 194 60 and xis the distance from the center in meterso There is striking agreement between· the attenuation coefficients µ values in equations 8 and 9D and the coefficients in equations 2P 3g and 7o Thus the assumption that the distribution intensity o·r residual aotivity mirrors the distribution of' neutron intensity produced by the blast is still further strengthenedo · An attempt can now be made to approximate the relationship between neutron intensity and distance at the time of the explos ionD and then to express the neutron intensity in terms of roentgen units so that the · ----DECLASSIFIED - - - - Authority tVN D ¥ 05 • • biological effects may be· estimatedo It is convenient to separate the neutrons into two categories 0 slow and fast and for the present purposes slow neutrons are considered to have a mean energy of' 200 electron voltsp and £ast neutrons of' greater than 3 million electron voltso Finally the relationship between gamma radiation intensity and distance from the explosion may be approximated end expressed in tenns of' roentgens o and the bulk of' the radiation responsible for the production of radiation sickness may thus be accounted f'oro The fast neutrons are considered f'irsto According to a Manhattan District Project Report -by Klema 8 0 · a total of' 606 x 1021 fast neutrons energies above 3 Mev passed through a sphere 202 meters in radius in the New Mexioo explosiono Such a sphere has a surface of 5ol3 x 109 am 2 o Therec forep the intensity at 202 meters was lo27 x 1012 fast neutrons om2 o As dis cussed previouslyD neutrons are expected as a first approximationo to obey the inverse s·quare law with he inoo oration of an attenuation factor thus s 0 I 0 I x2 ec µ x Io • or e µ x C 12 2 In this caseo _ is the f'ast -neutron intensity lo27 x 10 om at distance x of 202 meters and µ- is cons· idered to be the constant O000237 obtained rom the analysis of' the Japanese sulfur data previously disoussedo Solution for oo the fast neutron intensity at 1 meter gives a value of_8o37 x 1017 fast neutrons cm2 o This value corresponds to the total number lo05 x 1023 of fast neutrons that passed through a sphere 1 meter in radiuso It is of' considerable interest at this juncture to note tha t the Japanese 4 on the basis of' their residual activity measurements are in agreement amo themselves that the total number or fast neutrons liberated was 1 x 1023 0 The daily minimum toleranoe dose of fast neutrons was estimated by Professor G Ho Dessauer of' the University of' Rochester as being 200 fast neutrons cm 2 secondo In one day 0 theng a total of 200 x 60 x 60 x 24 2 lo728 x 107 fast neutrons om2 may be tolerated and this is equivalent to the roentgen tol rance limit of 0 1 rv Therefore it may be said that l r 1°728 x 10 fast neutrons am2 Converting the neutron intensity value at l meter to intensity in terms of r a value of 4o84 x 109 r is obtainedo and this may be considered to be-i00 Using the value of 0000237 tor µ the equation 0 Q 0 109 e-Oo00237x Im---------4o84 X 10 x2 may be written where is the number of' r ooourring at a distanoe of' x meters from the explosion owing to fast neutrons v The effect of sl neutrons m be expressed in like manner o Aooord ing to two Manhattan Distriot Projeot Reports 8 9 a total of 308 x 1024 --· ---»-ECLASSIFIED Authority t JND ¥100 SS_ • • slow neutrons mean energy 2oo·eleotron volts passed through a sphere 1 meter in radiuso Again it is of interest to note that -the Japanese 4 have estimated the total number of slow neutrons to be 6 x 10240 Sinoe a sphere 1 meter in radius has a surface area of lo26 x 10 5 om2 0 it is readily calculable that an intensity of 3o02 x 1019 slow neutrons cm2 ooourred at 1 metero · Again according to Professor DessauerD the daily minimum toleraJ lce dose of slow neutrons was estimated to b·e 1500 slow neutrons cm2 secondo Thus in one day a total of 1500 x 60 x 60 x 24 lo296 x 108 slow neutrons om2 may be tolerated 0 and this value is equivalent to Ool ro Asslmling the conversion factor l r a lo296 x 109 slow neutrons cm2 0 the slow neutron intensity at l meter may be expressed as 2o33 x 1010 ro Using this value as c 0 and the value for µ as OoOO'f 8 which was obtained by analysis ot the· Japanese bone activi y data 0 it is pos ible to write the equations I e 2033 X lOlO 8 -0o0078x 11 ------- x2 where I is the number of r occurring at a distance of x meters from the explosTon owing to slow neutrons o The last major faotor resp·onsible for the production of radiation sickness is the gamma rays produced by the ·explosion of the bombo ·The exact relation between gamma ray intensity and distance from the e plosion has been formulated by Weisskopf 9 0 and includes several factors which are important at distances less than 800 meters 0 such as the secondary gamma ray production of the radioactive isot pes produced in the ground by the neutron bombardmento For the prese t purpo11e1 1 however 0 it is possible to formulate a more simple relationship which wil serve as an approximation for the longer distances O these being ·of ··more importance medicallyo ·Values for 10 and µ were derived from the data in a Manhattan District Memorandum Report 10 for distances greater than 800 meters 0 and the relationship between gamma ray intensity in r unitso 1 0 ·and distance in -meters from the explosiono _o may be expressed oy the equations Im 2o72 X l09 8 a0o0016X 12 x2 The value of 000016 for µ in equation 12 is somewhat lower than expected 0 and corresponds to an extremely penetrating ge mma radiation of energy con sider bly in excess ot one Mevo This value 0 however 0 was obtained empirically from the best data availableo and may be modified by future i'indingso The total radiation received immediately in the form of fast neutrona 0 slow neutrons o and gamma rays mq be expressed in r miita as a function ot distance from the explosio by a summation of equations 10 0 llo and 12 thus 8 I a 2o72 X 109 ea0o_0016x_ x2 gamma rays -· ----DECLASSIFIED - Authority NN D ¥jDo S_tj 4 8 0 9 4 X 10 e x2 0o00237x fast neutrons • 2 0 33 X 1010 e- o0078x - x2 slow neutrons l'Z UJ • • where I is the radiation in r units received immeq iately at a distance of x meters f'rom the explosion This equation is valid for distances greater than BOO meters 0 and for distances less than 800 meters it yields minimal values for Io Figure 8 h s been constructed from equation 13 to indicate graphically-the contribution of each of' the three factors to the total radiation emi t ed at the time of the explosion and table 8 shows the -relative importance of the three factors at various distances from the explosion oenter and hypocenter at Nagasakio Substantiation of equation 13 is expected to cane from a study of the radiation effects observed in the bomb victims at Nagasaki and some modifi c tion of' the constants mEzy have to be madeo This study is being carried out under the supervision of Captain Shields Warren MC USNRa and the results are to be reported latero In addition correlated studies on the nature of the ·residual radioactive materi ls in the ground at Nagasaki and Hiroshima are b ing carried out in this laboratory and will be reported separatelyo Finally estimates of the heat intensity as a function of distance at Nagasaki are being made in collaboration with the Bureau of Standards and these results will also be reported separately ACKNOWLEDGMENTS The uthors wish - o express their most sincere thanks to Captain Shields Warren MC USNR 0 who as Officer-in-Charge of NavTechJap Team 11 facilitated this study in· every regarcl o ·Acknowledgment is due the members of the Naval Technical -Mission to Japan and of the Second Marine Division 0 in particular the Mapping and Reproduction Seotiong who cooperated whole 0 heartedly in the p_ros ecution of the field measurements o We should also like to thank CPhM M JD Had4on 0 USN for the rendering of the figures in this reporto Finally o we w i sh to express our appreciation to the Manhattan DistriQt and specifically to -Colonel Stafford Lo Warren and Captains Ho Lo Barnetto Ro A TybQut 0 and Do Lo Collins O • for information and assistance during the course •of this study 0 NELLO PACE Lieutenant Commandero H S g USNR ROBERT E SMITH Lieutenant Commander H S USNR APPROVEDs Eo Go HAKANSSON ·Captain o MC g USN Commanding Ao Ro BEHNKE Captain MC USN Researoh Executive -· --DECLASSIFIED Authority IVND ¥100 S -- -14- •• lo 2o REFERENCES Kimurao Moo and Tazima Eo O Epicentre centre in the air and hypocentre vertical projection of epicentre on the earth of explosio an_Q the size of the fire ball o Naval Medical Research Institute and Naval Technical Mission to Japan Series of Japanese Reports on the Atomic Bomb O Report Noo 17 0 6 Dec 19450· · Harnsberger ' _ Ho FoD McKnighto Fo Gog and Wheeler Oo RG11 Daily weather data11 Nagasaki Ci y 0 11 July 31 August 1945 Naval Medical Research Institute and Naval Technical Mission to Japan Series of Japanese Reports on the Atomic Bombl Report Noo 291 1 Sep 19450 Miyazaki Yoa and Masuda ToD Radioactivity due to the atomic-bomb at Hiroshima and its surrounding distriots 0 Naval Me dical Research Institute and Naval Technical Mission to Japan Series of Japanese Reports on the Atomic Bomb 0 Report Noo 16 0 Jan 19460 Shinoharao Koo Morita 0 0 0 and Kohra 0 KGo Radioactivity of the ground at Nagasaki City Em d its neighborhood 11 Part IIa Naval Medical Research · Institute and Naval Technical Mission to Japan Series of Japanese Reports on the Atomic Bomb 0 Report Noo 13 0 Jan 19460 Shinoharao Ko Okada0 To II Morita 0 So Kohra o Ko Inoue o Ko o arid Kawai 0 No 11 Radioactivity of the ground at Nagasaki City and ts neighborhood o · N9 val Medical Research Institute and Naval Technical Mission to Japan Series of Japanese Reports on the Atomic Bombo Report Noo 11 o Nov 19450 • · Masudao Too Sakata 0 Tos and Nakane 0 Ro o Radioactivity due to the atomic bomb at Nagasaki and its surrounding districts Naval Medica Research Institute and Naval Technical Mjs si n to Japan Series of Japanese Reports on the Atomic Bomb 0 Report NoQ 140 Jan 19460 Yamasaki Fo end Sugimoto Ao o Radioactive phosphorus P 32 produced in the hmnan bones and sulfur insulators in Hiroshima Naval Medical Research Institute and Naval Technical Mission to Japan Series of Japanese Reports on the Atomic Bomb o Report Noo 1 7 6 Dec 19450 Klem o E o Do Ju y 16th nuclear explosions fast ne utron measur_ements using sulfur as the detector Manhattan District Report LA 361 o 1 Oct 19450 Weisskopf o Vo Neutron and gamma ray effects after the nucle·ar explosion II 0 Manhattan District Report LAJ4S 250 31 May 19450 Weisskopf Vo Hoffman o J O O Aebersoldo p O and Hempelmano Loo Manhattan District Memorandum to Co Kistiakowsky 5 Sep 19450 Cl 3o 4o So 60 · So 9o lOo • -·---·------DECLASSIFIED Authority f JND ¥300 SS_ Authority • • DECLASSIFIED I JND f1c 5S Table lo Conversion ot Japanese and United States dates to number ot d s following the explosion at Hiroshima H and Bag as aki N♦ Date Jap H UoSo N Date Japo UoSo H N Date UoSo Japo · a N 92 93 94 5 96 97 98 99 100 101 102 103· 104 106 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 116 116 117 118 119 120 121 122 12·3 124 126 126 127 128 129 130 131 132 133 134 - 6 Aug 45 5 Aug 45 0 1· 6 7 8 2 7 9 8 3 10 9 4 10 11 5 · 11 12 6 12 13 7 14 13 8 14 15 9 16 15 10 16 17 11 · 17 18 12 ·18' 19 13 19 20 ·14 20 21 15 21 22 16 22 23 17 18 23 24 25 24 19 26 25 20 27 26 21 · ·21 28 22 29 28 23 29 30 24 31 30 5' 1 Sep 31 26 2 1 S p 27 3 2 28 4 3 29 4 5 30 6· 6 31 6 7 32 8 7 33 8 9 34 9 10 35 10 11 36 11 12 37 12 13 38 13 14 39 14 16 40 16 15 41 17 16 42 18 17 43 19 18 44 20 19 46 I _ 21 Sep 20 Sep 22 21 23 22 o 24 23 1 25 24 2 26 26 2 7 3 26 28 4 27 6 29 28 6 29 30 7 1 Oct 30 8 2 l Oct 9 3 2 10' 4 3 11 5 4 12 6 5 13 7 6 14 8 7 8 15 9 16 10 9 10 17 11 18 12 11 19 13 12 20 14 1 21 15 14 22 16 15 23 17 16 24 18 17 26 19 18 26 20 19 ·20 27· 21 28 22 21 29 23 22 30 24 23 31 26 24 32 26 26 33 27 26 34 28 27 35 29 28 36 30 29 37 31 30 38 1 Hov 31 39· 2 1 Nov 40 3 2 J l 42 4 6 3 ' 46 47 48 49 50 51 52 63 64 55 56 67 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 76 76 77 78 79 80 81 82 43 44 45 46 47 48 49 50 51 52 53 54 56 ·55 67 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 83 · 80 84 81 86 82 86 83 87 84 88 86 89 86 90 87 91 88 6 Nov 5 Nov 6 7 8 7 8 9 9 10 10 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 30 1 Dec 30 1 Dec 2 2 3 3 4 4 5 6 6 6 7 7 8 8 9 9 10 10 11 11 12 12 13 13 14 14 15 16 16 16 17 17 18 18 19 19 20 20 21 • Date Japo Date Japo H N UoSo 22 Dec 45 21 Dec 45 22 23 23 24 24 26 25 26 26 27 28 27 29 28 30 31 1 Jan 46 2 3 4 29 30 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 Feb ·2 3 4 5 31 l Jan 46 2 3 4 6 6 7 8· 9 10 11 12 13 14 15 16 17 18 19 20· 21 22 23 ·24 25 ··26 27 28 29 30 31 l Feb 2 3 4 ----·»ECLASSIFIED Authority I JN D M00 5 _ • Table l Continued 138 139 140 141 142 143 144 145 146 147 148 149 150 135 136 137 138 139 140 141 142 143 144 145 146 147 151 148 152 149 153 150 154 161 155 152 ·166'153 157 164 158 156 159 166 160 157 161 158 162 159 163 160 164 161 165 162 166 163 167 164 168 165 169 166 170 167 171 168 172 169 173 170 174 171 175 172 176 173 177 174 178 175 179 176 180 177 181 178 182 179 183 180 Date UoSo 7 5 Feb 6 8 7 9 10 8 9 10 6 Feb· 11 12 13 14 16 16 17 18 19 20 21_ 22 23 24 26 26 27 28 l Mar 2 3 4- 5 6 11 12 13 14 15 16 17 18 19 20 21 22 23 · 24 26 26 27 28 l Mar 2 3 4 6 7 6 8 9 7 8 10 9 11 10 12 13 14 15 16 17 18 19 20 21 22 23 11 12 13 14 15 16 11· 18 19 20 21 22 H N Japo 184 181 186 182 186 183 187 184 188 185 189 186 190 187 191188 192 189 193 190 194 191 195 192 196 193 197 194 198 195 199 196 200 197 201 198 202 199 203 200 204 201 206 202 206 203 207 204 208 205 209 206 210 2 i f 211 208 212 209 213 210 214 211 216 212 216 213 217 214 218 216 219 216 220 217 221 218 222 219 223 220 224 221 225 222 226 223 227 224 228 225 229 226 UoSo 24 Mar 23 Mar 24 26 26 26 26 27 28 27 28 29 29 30 30 31 1 Apr 31 l Apr 2 2 3 3 4 4 5 6 5 6 7 8 1 8 9 9 10 10 11 11 12 12 13 13 14 14 15 15 16 16 17 18 17 18 19 19 20 20 21 21 22 22 23 23 24 24 26 25 26 26 27 27 28 28 29 29 30 l MS¥ 30 l May 2 2 3 3 4 4 5 6 6 7' 6 8 H N 23'0 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 260 251 252 253 254 255 256 257 258 259 260 261 262 263 264 266 266 267 268 269 270 271 272 273 274 275 227 228 229 230 231 232 233 234 35 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 261 262 253 254 255 256 257 268 259 260 261 262 263 264 266 366 267 268 269 270 271 272 • • Table 2o- Calculation of equation for expression or residual activity at Hiroshima in terms of the distance from the air burst point height assumed to be 570 meters of the bombo This equation is for the residual activity as of 1 November 1945 0 87 days following the explosion H 87 o Distanoe 0 DistanoeD x 0 from d from air burst hypopoint center meters meters x2 73o4 57407 330p288 13004 68407 3410900 Intensity 0 Calculated Calculated Calculated Is of resiIo µ I dual µr hro µr hro activity µ r hro 62 06 ol2 X 10 8 69o3 -ca 57o3 Oo99 x 108 s·8o8 0000342 24706 62106 386si300 4408 0o96 X 108 47o0 0o99 X 8 10 32o5 0o99 X 108 19o2 0000209 37908 68409 469»050 32o0 53203 78004 6090100 18o9 0000278 c c 86900 103903 l 0 Q80si060 10o7 Oo00276 Mean •Calculated from equations loOl x __ · 8 ToOl x 10 10a 8 0_o00276x x2 Where I is the residual activity in µ- r hro· and xis the distance from the air burst point in meters - DECLASSIFIED Authority tVND ¥10055_ 5o3 • • ··Table 30° Calculation of equa ion-for expression of residual - · activity at Nagasaki in terms of the distanoe from the air burst point height assumed to be 490 meters of the bombo This equation is for the residual activity of 18 October 1945 0 70 days following the explosion N 70 as Distance d 0 from ·hypoC center meters Distance 0 x from air burst point meters 46o9 ll 802 18001 26000 40805 534ol 49202 504ol 62200 55407 63709 72'4o9 Intensity 0 Io ot residµal activity µ r hro x2 242s 300 2540070 272s 535 69o3 67o3 Calculated Calculated Calculated Io JL I µ rfiiro µ r bro 0001200 5o27 X 10 8 0000983 4o96 X 108 0000657 4o72 X 108 0000297 4o78 X 108 0000360 6069 X 10 4408 3070700 40609 70 525g470 32o0 l8o9 0000700 5o24 X •Calculated from equations 5o24 108 e-Oo0070x e ____ 2_ _ _ __ X __ X where is the residual activity in µ r ii and x is the distance from the air burst point in meters -·------- - --- DECLASSIFIED Authority NND ¥ 00 60o5 49o7 35ol 1408 602 l0o7 Me I 8 69o0 108 • • Table 4oc Summary of the blood findings on inhabitants of the village or Nishiyama approximately 100 days following the explosion N 99 to N 102 Variable examined Age in years Erythrocyte count per mm 3 HemoglobinD grams per 100 CCo Leuoooyte count per mm3 Differential leuoooyte count Segmented neutrophiles 0 per oent Lymphoo eso per cent Monooyteso per oent Eosinophileso per cent BasophilesD per cent Hema tocrit per cent Mean corpuscular volume 0 µ 3 Mean corpuscular hemoglob m 0 µµgm o Noo of cases DECLASSIFIED Authority tVN D¥jc O_s j '- 2 61 61 ·61 1D470DQQQ o0 4 750 1 61 34 16 · 0 0 61 61 61 61 61 _o 28 ·28 30 Mean corpuscular hemoglobin conoentrationQ per cent Volume index Color index Range 28 28 30 32· 70 21 Cl 0 O Cl C c CJ C CJ C ° 86 4D980o00Q l4o2 130000 76 50 12 28 2 c ' 37024 4Dl39 0 500 12o0 7D356 5706 32o7 40'1 4o7 Oo2 43 107 ·37o2 36 29o4 1906 39 Oo80 lo24 Oo73 lol2 CJ Mean 89ol 33o3 lo034 lo032 • • Table 5o Le cocyte counts of 25 r sidents of Nishiyama who were not exposed to the atomic banb explosion but who resided ·in Nishiyama continuously s inoe the explosiono The data on 1 0 15D and 28 October 1945 N 53P N 610 d N 80 were obtained by Japanese investigators from the Kyushu Imperial University Nae NAKAO Tsuki NAKAO Takaichi NAKAO Taka NAKAO Taeko NAKOA Tsunehisa YAMAGUCHI Iwamats u N AK0A Eijiro UR AKA WA Xiichi URAUWA G paohi NAKAO Fumi Leuooovte count mm3 100· N 80 N 67 N Age Sex Japo N 63 Noo l Oct 46 15 Oct 45 28 Oct 46 17 Nov 45 10D600 90000 160400 65 6D800 F -124 8g5OO 4g8OO 6g400 60200 48 M 123 l2gOOO l4g8OO 10 000 41 F 135 110600 25gOOO 8 0 800 23glOO 18 F 122 170000 300700 60600 11· M 88 120600 170400 13 500 60200 8 700 68 M 80200 5'1800 40500 60200 60 M 40900 8g8OO 6'1900 90300 60 M 60900 90800 60400 100300 68 M 10600 2 90300 4 900 7 700 ·40500 61 F 60800 60200 90200 7 200 45 F 106 811600 130000 11 0100 44_ F 70500 63 7 200 270700 3Os 8OO 44 M 3 160200 80400 360300 37g8OO 41 13 11 400 F 10100 190600 16s 1OO 39 F 112 110700 38' M 126 1 1 0 400 12s 200 80200 2Os 8OO BD600 · 6 100 6 600 70 800 30 F 26 60200 200000 12 100 60500 25 F 121 11 0500 230400 180900 25 F 1Q6 120400 llg9OO 100400 10 2 0 15 600 17 F s 8OO 140800 160300 16 M 90100 6silOO 180900 130200 8 0 200 14 14 6S 40O 180800 16'1300 13 M 90700 30 100 · 10500 170400 11 120600 M 100800 60800 150900 8 0 300 1 M J i'- c c c c URAUWA Suga NAXOA Matsu MATSUO Takis abur·o NAKAO Tsuta RASHIGUCHI Ohika URAK AWA Torao YAMAMOTO He rue YAMAGUCHI Yoshino NAXAO Masaka NAKAO Kazuko NAXAO Toshikazu ltATSUO Akira OltAWACHI Masahiko NAKAO Kiyoshi MATSUO adayuki Na 25 -·--·»ECLASSIFIED Authority fVN D°¥100 Sti -- c c c c Mean 90592 Sof o 3s 439 14 800 70404 160184 8g43O 7s 3OO 10691 • • Table 60 Calculation of half lite of residual activity at Nagasaki based on data obtained by NavTeohJap Teem llc 100 on 18 October 1945 N· 70 and data obtained by Japanese investigators 6 on 27 December 1945 N 140 Distance 0 d 0 from hypoc center me-t ers DistanoeD xD from air burst IntensityD I700 at meters µr hro µr 4ro 99o5 500 63o4 5206 0000267 25906 24908 550 36o9 280·3 0000379 18209 N 10 Intensity I1 4oo at N 140 Half'c tlife X days 600 34603 42701 650 2108 16o5 13ol 0000487 l 42o3 0000618 11202 - 805 ' 49909 700 800 408 0000730 95o0 66'108 760 4o9 2o7 0000851 8106 Mean 9 0alculated from equ tion 8 · I70 6024 X 14506 8 ·ooo0070x 10 e 2 X 9 Calculated from equations 1140 a 9o73 x 108 ec 10o0086lx 2 ·X where I a intens ty of residual activity in µr 4ro and a distance from air burst point in meters heig t of burst a 490 meters ---»EcLAss° Authority I V N 1 • • Table 7o- Calculation of equation for expressi n of residual activity at Nagasaki in terms of the distance from the air burst point height assumed to be 490 meters of the bombo The equation is for Japanese residual activity data 6 as of 27 December 1945 140 days following the explosion N 140 Distance 0 x from air burst point meters Distance 0 d from hypocenter meters 62 49309 106 6606 251 336 51604 52o2 266 669 4306 218 53603 287 624 3408 271 55909 313i 541 26ol 9o69 X 108 5608 9o83 X 108 5108 0000676 0000814 163 108 8 · l0ol3 x 10 9o90 0000742 344 0 429 17o4 X 8 10 25ol 9o38 X 108 180 l 9o03 X 10 9o73 X 108 0000930 415 64201 412 325 807 ' 0 0000861 Mean Calcul ted from the equations 9073 I 13 X l08 e-0000861 X 2 X where is the residual activity in µ r hro and xis t e distance from the air burst point in meters DECLASSIFIED Authority fVND ¥300 ss_ 33o5 l0ol5 0001153 58609 4206 X 0000853 323 µ r hro µ r hro µr hro 2430944 50103 Calculated · Calculated Calculated I µ Io Intensity I of residual activity x2 8 9o4 - Table 80° Caloulation 0 from equation 13 0 ot the total radiation intensity£ I 0 · in roentgen units produced by gamma rayso r a fast neutrons 0 fna and-slow neutr-ons O I n as a function of the distance in meters 0 a from the explosion oeni r 0 at the time of the explosion at Nagasaki Distance from -hypo center meters 0 -·- Distance from center x meters x2 r 1mits r units 1tn 1sn r units Total I units Iy r 500 700 4900000 1943 1880 202 4025 750 896 8020816 883 721 27 1631 1000 1114 1 0 240 0 996 413 278 3 694 1250 1343 1 0 803 0 649 201 111 l 313 1500 1677 2 0 486 0 929 103 46 1750 1816 302970866 54 20 2000 2059 402390481 29 9 38 2250 2303 603030809 16 4 20 2600 2549 60497 0401 9 DECLASSIFIED Authority fVND MCOSt j -- -· 2 149 ·• 74 11 IN HIROSHIMA DATA TAKEN 1-2 NOV 45-H 87-H 88 I 250 I 500 I I 750 1500 25 • • 64 28 • •19 22 r hr values ore given beside flJ resentotiv locations The I lµr hr contour is approximated •20 •37 28• •22 25 • I' 1750 ·%MURA - f I SA J ·· •• _ l · w MOTO 080 µr llr µr r i 1 17 i #cYtJ 8 Oct tY Y reported d1oac liy J ane e r ' _ · '• -· • 1 KAGAMI •1'YATSUSHIRO DRIFT OF RADIOACTIVE MATERIAL SHIMO-JIIIA IN NAGASAKI 15AREfo 5 o It I I I I 10 I I KILOMETERS I _ tASHIK 7- t AV TECH JAP TEAM II • MAP PREPARED BY N NMRI-HAOOEN '46 IN URAKAMI ANO NISHIYAMA AREAS OF NAGASAKI I 0 I 500 I I I I I I I 1000 METERS I I 1500 • 213pr hr Fiqure 3 1 NMRI-HADDEN 46 RESIDUAL RADIOACTIVITY AT NAGASAKI ATOMIC BOMB SITE RADIOACTIVITY MEASUREMENTS MADE IN TH E PERIOD 15 OC T- 2 7 OCT 45-N 67-N 79 Ml SUBISHI URAKAMI ICE PLANT SCHOOL FOR BLIND A O 0 0 HURC 100 20 0 300 METERS 400 500 69µ hr contour contour 1 µr hr contour JAPANES CENTER MAP PREPARED BY NAV TECH JAP TEAM II DECLASSIFIED Authority I JND Mc $S Figure 4 NMRI-HADDEN '46 g 0 1 Q 80 25poo c t l l J n IJ IJ I 70 20 000 60 Time at which intensity fell to 0 1 r per day rt E E Cl 0 n 0 0 Q C 0 u 50 G a - t 15 000 Summated r dosage Q • u 0 u • - 0 G 0 Leucocyte count E E 10 000 --- -------------- --------------- -----Days following explosion Figure 5 - Mean leucocyte count on 25 residents of Nishiyama and summated roentgen dosage received as a function of doys following the Nagasaki atomic bomb explosion _ The leucocyte data for days 53 68 and 80 are from Japanese sources and the value ot O days was assum·ed to be normal The vertical bars represent plus and minus one standard devia1lon • - - 30'0 Curve constructed from the equation g 9 -0 0078 X I 6 x 10 e x2 0 Ii -3 I Where I miry'gm bone x 10 6 Aug 5 • X Distance from center in meters • • c en 100 '0 a • C CD m • • • 0 • 250 ••• 500 Meters 1000 from Figure 6 - Residual activity in bone Yamasaki and Sugimoto DECLASSIFIED Authority f JND f1D0$S • • hypocenter at Hiroshima from data of • Curve constructed from the equation I 3 4 7 x I06 e -0 00237X 2 •• 0 e0 X • Where 2 0 nligm I l I mi t sulfur 3 x 10- 6 Aug 45 I • X Distance from center in meters CD C •o c • en Q u 1 0 - • 0 Q • • 0 Q m 0---- -------- ----------L---------'---------- L -----------' 250 DECLASSIFIED Authority IVND MQO SS 500 750 Meters from hypocenfer Figure 7 - Residual Yamasaki activity and in Sulfur Sugimoto ctt Hiroshima from 1000 I data of 2500 r----r---- --- ---- -- ---- --- ------ 'T ---- ---- ----- ----r---- ----r--- ---r-- • I 2 72 x 109 -0 0015X X gamma rays 4 84 x 109 e 0 00237X X 2 3 3 x o'o e 0 0078X X fast neutrons slow neutrons 1500 II C H 1000 Fast neutrons and slow neutrons 500 1000 1500 2000 X METERS FROM EXPLOSION CENTER DECLASSIFIED Authority t JND Mc o SS Figure 8 - Contribution of gamma rays fa st neutrons and slow neutrons t o t he total roen tgen dosage received im mediate ly at various distances from the explosion of a plutonium bomb 2500