36Cl measurements in hiroshima granite samples as part of an international intercomparison study

Abstract

Within the effort to resolve the so-called Hiroshima neutron discrepancy, an international intercomparison study has been carried out on granite samples from Hiroshima, with participating institutions from Japan, the US, and Germany. (36)Cl and (152)Eu produced in these samples by thermal neutrons from the A-bomb explosion were assessed independently by means of different techniques. At the Maier-Leibnitz-Laboratory near Munich, Germany, (36)Cl concentrations were measured by accelerator mass spectrometry. Measured (36)Cl/Cl ratios ranged from 1,670 x 10(-13) (at a distance of 146 m from the hypocenter) to 2.2 x 10(-13) (at a distance of 1,163 m from the hypocenter). One granite sample not exposed to A-bomb neutrons was measured as a control, and a (36)Cl/Cl ratio of 2.6 x 10(-13) was obtained. On average, our experimental results are 20-30% lower than those provided by model calculations based on the dosimetry system DS86. The results presented here do not support previous assessments of (36)Cl, (60)Co, and (152)Eu which had suggested much larger thermal neutron fluences than those calculated on the basis of DS86 for distances from the hypocenter of more than 1,000 m.

Funding crisis at the Radiation Effects Research Foundation

“…It is a measure of the importance of continuing the Japanese atomic bomb survivor cohort that a new set of dose estimates for the cohort, the so-called DS02 dosimetry, has been recently developed, funded at great expense primarily by the US and Japanese governments and approved for use at RERF by senior committees of both countries (Roessler 2003). The DS02 dosimetry, although (as it turned out) not substantially different from the previous (DS86) dose estimates, largely resolved apparent contradictions with thermal neutron dose activation measurements (Cullings and Fujita 2003, Huber et al 2003, Straume et al 2003 and thus validated in large part the estimates of radiation risk ascribed to gamma rays, the more relevant exposure to workers and, to a lesser extent, the general population.…”

Risk quantification

“…The final major turn in the evolution of the A-bomb dosimetry may have occurred. Huber et al [3] present in this issue one intriguing part of the recent development; their paper outlines the resolution that now begins to be accepted even for the thermal neutron activation data.…”

“…They are concerned with dosimetric problems in the two major radioepidemiological investigations, the follow-up of the atomic bomb survivors and the evolving radiation studies in the Southern Urals. One contribution [3] relates to a large effort that now appears to have reached its final resolution. The other contributions [4,5] address a still unresolved issue which calls for a similarly large effort.…”

Obituary: Prof. Dr. Albrecht M. Kellerer (1935–2022)

“…This dose reconstruction led to the Dosimetry System 2002 (Young and Kerr 2005) and finally demonstrated that the neutron doses to the survivors in Hiroshima were largely correct and the deduced radiation risk estimates reliable. Thanks to the continuous interest and tireless support of Albrecht Kellerer that this long-lasting project could be realized (Rühm et al 1998(Rühm et al , 2000(Rühm et al , 2007(Rühm et al , 2010Kellerer and Rühm 2002;Huber et al 2003Huber et al , 2005Straume et al 2003Straume et al , 2004Nolte et al 2005Nolte et al , 2006Hoshi et al 2008;Wallner et al 2010).…”