EVENT AND DESCRIPTION OF EXPOSED GROUPS 1.2 a carried out, nor was its opefating condition known to be satisfactory undar the emergency condition prevailing at the time of use. For these reasons the later readiggs, which were higher than the early survey Hy an average of 50 percent .when corrected to]the same times, Whole Body Gamma Doses Tur EstimaTep Vauues of external dose given in Table 1.1 were calculated from readings of radiation field survey instruments.* Averages of a numberof dose rate measurements on each island at a given time were used. The readings were taken in air, approximately three feet above ground,several days after the inhab- were used in computing the dbses listed. The instruments used for the latdr measurements were calibrated just prior to the surveys. 30 a eeee- ORIGINAL SOURCE SPECTRUM ame INFINITE PLANE JB'IN AIR ( I | I | i a I ' ‘ ' « od 5 t I 1 . t t ! I wi 8 20 4 ! e ' ° t =< ud ‘ i ; - « ' uw 1 ' i | ' | ' | ' ‘ | roo ' i ' 1 1 ; . ; !' ' ' ' ' 1 I ' ‘ ' l ' ' t \ ' a ; t ! ' ' t a 1 ‘ : I I ' 1 ' I ‘ t ' at 1 I ‘ ' \ ‘ ! ' I t ' | ! | oli Q iit 200 ] 400 ' 1 600 1 r 1 ji 1 800 1000 ENERGY (KEV) ! ( ’ FicurRE 1.2—Distribution of inherent energies of gamma radiation from mized fission products, and histoyram of degraded energics produced by Compton scattering at level of infinite plane 3 feet in air above uniformly-distribute fission products field. itants were evacuated. Before this time, ade- quate surveys with well calibrated instruments had not been possible, although readings had been taken with a single survey meter at the time of evacuation. However, preliminary ‘alibration of this instrument had not been *Army Navy catalog AN/PDE-39, 1.21 Characteristics of the Gdmma Radiation The fallout material, when [leposited on the ground, formed a large planay source of radiation. The energy distribution of the radiation reaching aun exposed individudl was influenced by its passage through the intervening air. A knowledge of the energy speqtrum of the ra-