Changes in Atomic Bomb Survivors' Dosimetry with the New Dosimetry System DS02

From 1987 through the late 1990s, thermal neutron activation measurements of materials exposed to the atomic bomb in Hiroshima appeared to show a different distance trend than estimates from dosimetry system DS86, calling into question the accuracy of DS86 and ultimately resulting in the formation of a joint US-Japan scientific working group to develop an improved system, DS02. DS02 recalculates both the source term and radiation transport using the newest methods and input data, with new estimates of explosive yield (15kt→16kt) and height of detonation (580m→600m) of the Hiroshima bomb, but no similar change in Nagasaki. DS02 developers evaluated new measurements in all previous categories and two new categories, made designed measurement inter-comparisons on split samples, and achieved a resolution of the apparent neutron discrepancy. DS02 free-in-air gamma kerma is about 10%>DS86 at distances>1km where almost all survivors were located; neutron kerma ranges from about 10%>DS86 at 1km to 15% 2km in Nagasaki. Average changes in shielded kerma and representative organ doses vs. distance are reviewed, concluding with a discussion of plans to improve dosimetry implementation at the Radiation Effects Research Foundation (RERF) by using tools such as the Geographical Information System (GIS).