Shielding survey and dosimetry study
To evaluate the late biological consequences of the atomic bombs requires the most precise knowledge possible regarding the radiation exposure of those in the study samples. Compilation of the data needed for the basic radiation estimates requires a comprehensive program embodying studies and consideration of many intrinsic and concomitant factors which can be grouped under two headings: exposure to atomic radiation – initial energy released; air dose; shielding; body dose (total dose, selected tissues, differences in biological response); and possible contaminants – residual radiation; fallout; X-ray dosimetry study (diagnostic, therapeutic, industrial); radioactive isotopes; natural background radiation.
With the collaboration of the Oak Ridge National Laboratories (ORNL), and with consultation from the Japanese National Institute of Radiological Sciences, ABCC is engaged in a continuing program of research to solve these problems.
Considerable information is needed before individual doses can be calculated with any degree of certainty. Although good estimates exist as to the general magnitude of radiation from atomic explosions, the bombs used on Hiroshima and Nagasaki were not monitored for their radiation potential. Therefore, this has been estimated from data on similar, but not identical, nuclear weapons. In addition, dose calculation requires an exact knowledge of the whereabouts of the individual at the precise moment of explosion. Finally, the effects of shielding by a variety of structures and circumstances play a considerable role in the total dose received.
As early as 1951 shielding was under investigation at ABCC and by 1953 efforts were being made to estimate the radiation dose received by individuals. Great impetus was given to the work in mid-1956 when, under the sponsorship of the Civil Effects Branch of the Division of Biology and Medicine, USAEC, a program of collaboration with ABCC was established in the Health Physics Division of ORNL and designated ‘Ichiban.’ The program was directed at the following problems: accurate description of the environment of each survivor at the time of the explosion (shielding survey history); determination of the characteristics and magnitude of the radiation field produced by each weapon (air-dose curves); determination of the spatial distribution of radiation in various shielding configurations; and liaison to assist ABCC in the application of the findings of the Ichiban team, to be effected by periodic visits to Japan and by correspondence, aimed at the communication of new dosimetric information, its integration into the program, the resolution of technical problems, and exploration of factors incompletely evaluated.