Rääf C, Finck R, Martinsson J, Hinrichsen Y, Isaksson M
Medical Radiation Physics, Department of Translational Medicine, Malmö, Lund University, SE-205 02 Malmö, Sweden.
J Radiol Prot. 2020 Sep;40(3):790-814. doi: 10.1088/1361-6498/ab993a.
The averted cumulative lifetime attributable risk (LAR), the residual dose and highest ground deposition of Cs complying with a reference dose level of 20 mSv yr to an individual returning after one year to an area contaminated by unfiltered releases of fission products from a nuclear power plant (NPP) were evaluated by applying an existing exposure model designed to compute age- and gender-dependent time-integrated LAR. The model was applied to four types of nuclear fallout scenarios, partly based on data from the Chernobyl and Fukushima releases and from theoretical source terms from Swedish NPPs. For rapid decontamination measures that achieve a 50% relative reduction in external dose rate within 1 year, compliance with the reference level 20 mSv yr can be attained for an initial Cs ground deposition of up to 2 MBq m with relaxed food restrictions. This compliance can be attained at even higher ground deposition (up to 4.5 MBq m) if using the strict food restrictions employed in Japan after 2011. Considering longer than 1 year return times it was also found that the benefit of implementing decontamination decreases rapidly with time (2-3 years half-time), especially if the fallout has a high initial Cs to Cs activity ratio and if the ecological half-time of the external dose rate is short (<5 years). Depending on fallout scenario the averted cumulative LAR for newborn girls by decontamination that is achieved after 5 years is only between 6% and 11% of that obtained by evacuation alone during the same time, indicating a rather limited radiological benefit of decontamination if delayed more than a few years. We conclude that decision makers and emergency response planners need to consider that protracted decontamination measures may have limited radiological benefit compared with evacuation in terms of averted future cancer cases, albeit it may have other societal benefits.
通过应用一个现有的用于计算年龄和性别相关的时间积分终生归因风险（LAR）的暴露模型，评估了避免的累积终生归因风险（LAR）、残留剂量以及铯的最高地面沉积量，该模型适用于一名在一年后返回受核电站（NPP）裂变产物无过滤释放污染地区的个人，其参考剂量水平为每年20毫希沃特。该模型应用于四种核沉降情景类型，部分基于切尔诺贝利和福岛释放的数据以及瑞典核电站的理论源项数据。对于在1年内使外部剂量率相对降低50%的快速去污措施，在放宽食品限制的情况下，当初始铯地面沉积量高达2兆贝可每平方米时，可符合每年20毫希沃特的参考水平。如果采用2011年后日本实施的严格食品限制，在更高的地面沉积量（高达4.5兆贝可每平方米）时也可实现符合该参考水平。考虑到返回时间超过1年，还发现实施去污的益处会随时间迅速降低（半衰期为2 - 3年），特别是如果沉降物的初始铯与铯活度比很高，并且外部剂量率的生态半衰期较短（<5年）。根据沉降情景，5年后通过去污实现的新生女孩避免的累积LAR仅为同期仅通过疏散获得的LAR的6%至11%，这表明如果延迟数年以上，去污的放射学益处相当有限。我们得出结论，决策者和应急响应规划者需要考虑到，与疏散相比，就避免未来癌症病例而言，长期去污措施的放射学益处可能有限，尽管它可能有其他社会益处。
