Warnery E, Ielsch G, Lajaunie C, Cale E, Wackernagel H, Debayle C, Guillevic J
Institut de Radioprotection et de Sûreté Nucléaire, Bureau d'étude et d'expertise sur la radioactivité naturelle, IRSN, PRP-DGE, SEDRAN, BRN. BP17, 92262 Fontenay aux Roses, Cedex, France; Mines ParisTech, Centre de Géosciences, Equipe de Géostatistique, 35 rue Saint Honoré, 77305 Fontainebleau, France.
Institut de Radioprotection et de Sûreté Nucléaire, Bureau d'étude et d'expertise sur la radioactivité naturelle, IRSN, PRP-DGE, SEDRAN, BRN. BP17, 92262 Fontenay aux Roses, Cedex, France.
J Environ Radioact. 2015 Jan;139:140-148. doi: 10.1016/j.jenvrad.2014.10.002. Epub 2014 Nov 8.
Terrestrial gamma dose rates show important spatial variations in France. Previous studies resulted in maps of arithmetic means of indoor terrestrial gamma dose rates by "departement" (French district). However, numerous areas could not be characterized due to the lack of data. The aim of our work was to obtain more precise estimates of the spatial variability of indoor terrestrial gamma dose rates in France by using a more recent and complete data base and geostatistics. The study was based on the exploitation of 97,595 measurements results distributed in 17,404 locations covering all of France. Measurements were done by the Institute for Radioprotection and Nuclear Safety (IRSN) using RPL (Radio Photo Luminescent) dosimeters, exposed during several months between years 2011 and 2012 in French dentist surgeries and veterinary clinics. The data used came from dosimeters which were not exposed to anthropic sources. After removing the cosmic rays contribution in order to study only the telluric gamma radiation, it was decided to work with the arithmetic means of the time-series measurements, weighted by the time-exposure of the dosimeters, for each location. The values varied between 13 and 349 nSv/h, with an arithmetic mean of 76 nSv/h. The observed statistical distribution of the gamma dose rates was skewed to the right. Firstly, ordinary kriging was performed in order to predict the gamma dose rate on cells of 11 km(2), all over the domain. The second step of the study was to use an auxiliary variable in estimates. The IRSN achieved in 2010 a classification of the French geological formations, characterizing their uranium potential on the bases of geology and local measurement results of rocks uranium content. This information is georeferenced in a map at the scale 1:1,000,000. The geological uranium potential (GUP) was classified in 5 qualitative categories. As telluric gamma rays mostly come from the progenies of the (238)Uranium series present in rocks, this information, which is exhaustive throughout France, could help in estimating the telluric gamma dose rates. Such an approach is possible using multivariate geostatistics and cokriging. Multi-collocated cokriging has been performed on 11 km(2) cells over the domain. This model used gamma dose rate measurement results and GUP classes. Our results provide useful information on the variability of the natural terrestrial gamma radiation in France ('natural background') and exposure data for epidemiological studies and risk assessment from low dose chronic exposures.
在法国，陆地伽马剂量率呈现出重要的空间变化。以往的研究得出了按“省”（法国行政区）划分的室内陆地伽马剂量率算术平均值地图。然而，由于数据缺失，许多地区无法被准确描述。我们这项工作的目的是通过使用更新且更完整的数据库以及地统计学方法，更精确地估算法国室内陆地伽马剂量率的空间变异性。该研究基于对分布在法国各地17404个地点的97595个测量结果的分析。测量工作由辐射防护与核安全研究所（IRSN）完成，使用放射性光致发光（RPL）剂量计，于2011年至2012年期间在法国牙科诊所和兽医诊所中暴露数月。所使用的数据来自未暴露于人为源的剂量计。为了仅研究陆地伽马辐射，去除宇宙射线贡献后，决定对每个地点的时间序列测量算术平均值进行处理，并根据剂量计的暴露时间进行加权。其值在13至349纳希弗/小时之间变化，算术平均值为76纳希弗/小时。观察到的伽马剂量率统计分布向右偏斜。首先，进行普通克里金法以预测整个区域内1×1平方千米单元格的伽马剂量率。研究的第二步是在估算中使用辅助变量。IRSN在2010年完成了法国地质构造分类，根据地质情况和岩石铀含量的当地测量结果确定其铀潜力。该信息以1:1000000的比例尺在地图上进行了地理参考定位。地质铀潜力（GUP）被分为5个定性类别。由于陆地伽马射线主要来自岩石中（238）铀系的子体，而该信息在法国全境详尽，有助于估算陆地伽马剂量率。使用多元地统计学和协同克里金法可以实现这样的方法。已在整个区域的1×1平方千米单元格上进行了多配置协同克里金法分析。该模型使用了伽马剂量率测量结果和GUP类别。我们的结果为法国自然陆地伽马辐射（“自然本底”）的变异性提供了有用信息，也为流行病学研究和低剂量慢性暴露风险评估提供了暴露数据。
