' - UNCLASSIFIED INTER-OFFICE MEMORANDUM DATE TO Ge Kistiakowsq FROM v SUBJECT l September 1 945 Weisskopf Po Aebersold L H He11pelmann F Reines CALCULATED BIOLOGICAL EFrnJTS OF ATOMIC EXPLOSION IN HlROSHI• AND Ifl u sAKI The accompanying table indicates the blast pre11sures and radiation and heat intensities ldlich haw been calculated for the atomic explosion at Hiroshi a and Naguald be· calculations indicate the followings 1 Blast effect fiying debris tailing buildings violent displacement etc may- be lethal as far as Class A damage 1-1 2 m 110 radius am possibq further Freak SlU rlval s ot individuals within this area would certainly occur According to the information obtained during the bombing of English cities such survivals might even crucur in the areas of greatest danage i e within 1 2 lllile of th a point directly beneath the explosion 2 Tha gaimna radiation emitted within few seconds after the explosion would probably be lethal for 80 -900 metera aince the lethal dose of this type ot radiation is SD0-900 roentgens would be killed by- radiation period at weeks no damage Freak survivors of the blast within this area Death in these cases might be delayed for a The number·or neutrons reaching the groum would probably cause 3 SeTere thermal burns third degree of the exposed skin would probably occur st tor one mile Clothing would afford considerable protection of the skin from the heat and light raysJ Em n the lightest type of ahelter woul d afford complete protectiono Because of the short intense exposure these burns would probably be even more serious than the most severe sunburns even though the spectrum of light from the explosion compares with that of sun J ight 4 Biological danage due to radiations from radioactive mte rl al deposited on the ground cannot be calculated since the latter is not lmo It is likely to be insignificant but umsual meteorologic ilenomena resu1ting in local precipitation or deposition of active ma terial on falling dust particles cannot be m cluded - 5 Other serious biological effects due to su f'focation burning ta death etc canno be predicted CD v V Weisekopt' P Aebersold L Hempelmann F Reines encl N VERIFIED UNCLASSIFIED FINAL DETEBIIINATION UNCLASSI Fl ED L M Redman LANL Classification Office S os §JL'v-µ Name F orm 25 UNCLASSIFIED ZoU Ot 31 ate CLASSIFJ ATION CANCELLED PER DOC REVIEWJAN 1973 CALCULATIOIS 01 HIROSHIMA KXPLOSIOR Rad1ue in Meters on ground Distanoe from bomb in meters Roentgens 0 550 35 000 590 800 2 500 27 0 g4o 1000 600 1000 114o 14oo 24oo actual Slast ps1 He t Light like s nl i gh t 1 om 100 Depth of Skin Heated to 100° in mm c 7 5 23 0 39 5 25 0 3 0 1 8 300 15 0 19 5 1 5 1500 130 9 0 1 1 0 1 0 2500 10 4 o 3 3 - o a e-- z zc x - U 2 u -o - I- L1 J 4 0 uu So Q