Skin dose from neutron-activated soil for early entrants following the A-bomb detonation in Hiroshima:: contribution from β and γ rays
Skin dose from neutron-activated soil for early entrants following the A-bomb detonation in Hiroshima:: contribution from β and γ rays
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DOI：
10.1007/s00411-008-0172-1
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发表时间：
2008-07-01
影响因子：
1.7
通讯作者：
Hoshi, Masaharu
中科院分区：
文献类型：
--
作者：
Tanaka, Kenichi;Endo, Satoru;Hoshi, Masaharu
据报道，在广岛和长崎的原子弹爆炸幸存者中，包括在爆炸后进入城市的“早期进入幸存者”，都有脱毛现象。对广岛这些幸存者的皮肤经中子活化土壤通过β和γ射线的吸收剂量进行了初步估算。使用蒙特卡罗辐射输运代码MCNP-4C，对地面上活化土壤的外部照射以及活化土壤颗粒对皮肤和头发的污染进行了估计。假设皮肤上有26 μ m厚的活性土壤作为一个例子，皮肤剂量估计约为0.8戈伊，对于包括爆炸后头7天在震源地面以上1米处的照射情况。在这种情况下，总皮肤剂量的99%来自土壤中的活化放射性核素，即，0.19和0.63戈伊。相比之下，发现由于土壤颗粒的皮肤污染对皮肤剂量的贡献约为1%。为了使其与地面上中子活化土壤的暴露量相当，皮肤上的土壤厚度需要约1毫米，这似乎很难保持很长时间。7天皮肤剂量的55%是在轰炸后的第一个小时内提供的。我们估计的皮肤剂量低于传统报道的脱毛阈值2戈伊。然而，应当指出，不能排除更极端的接触情景的可能性，例如皮肤上受到更严重土壤污染的入境者。
Epilation was reported among atomic bomb survivors in Hiroshima and Nagasaki, including "early entrance survivors" who entered the cities after the bombings. The absorbed dose to the skin by neutron-activated soil via beta and gamma rays has been estimated in a preliminary fashion, for these survivors in Hiroshima. Estimation was done for external exposures from activated soil on the ground as well as skin and hair contamination from activated soil particles, using the Monte Carlo radiation transport code MCNP-4C. Assuming 26 mu m thickness of activated soil on the skin as an example, the skin dose was estimated to be about 0.8 Gy, for an exposure scenario that includes the first 7 days after the bombing at 1 m above the ground at the hypocenter. In this case, 99% of the total skin dose came from activated radionuclides in the soil, i.e., 0.19 and 0.63 Gy due to beta and gamma rays, respectively. In contrast, contribution to skin dose due to skin contamination with soil particles was found to be about 1%. To make it comparable to the exposure by neutron-activated soil on the ground, a soil thickness on the skin of about 1 mm would be required, which seems to be difficult to keep for a long time. Fifty-five percent of the 7-day skin dose was delivered during the first hour after the bombing. Our estimates of the skin dose are lower than the conventionally reported threshold of 2 Gy for epilation. It should be noted, however, that the possibility of more extreme exposure scenarios for example for entrants who received much heavier soil contamination on their skin cannot be excluded.