The DS86 neutron dosimetry enigma: An analysis of some missing pieces to the puzzle

Abstract

Atom bomb survivors from Hiroshima and Nagasaki form, in principle, the most comprehensive database for the effects of radiation on man. The basic parameters required to define this database are the gamma-ray and neutron exposure doses experienced by each survivor. The importance of quantifying this database has long been recognized throughout the world. International programs conducted over the last four decades attest to the significance of this goal. Unfortunately, the quest for accurate gamma-ray and neutron exposure doses at the Hiroshima and Nagasaki sites has proven illusive. Efforts in the most recent of these programs, designated as Dosimetry System 1986 (DS86), have revealed a serious discrepancy between neutron transport calculations and thermal neutron activation measurements at the Hiroshima site. The magnitude of this discrepancy is especially difficult to explain in view of the extensive experimental and calculational efforts that have been expended to quantify this database. This serious and persistent discrepancy will be called the DS86 neutron dosimetry enigma. It is established that the DS86 neutron dosimetry enigma is a complex puzzle that precludes simple solutions. This conclusion is deduced through the identification and detailed description of a number of missing pieces of the puzzle. Each missing puzzle piece introduces distinct effects that must be addressed properly before there is any chance of resolving this enigma. While these missing puzzle pieces cannot resolve the DS86 enigma, they can be combined in different ways to provide insight into different aspects of the puzzle. Implications and conclusions that can be inferred from these missing puzzle pieces are presented and analyzed.