一次钴-60污染事件的多机构应急调查测量及其结果分析比较

MEASURING RESULTS OF AN EMERGENCY SURVEY AND COMPARISON OF ACTIVITY IN WATCHBAND CONTAMINATED BY ^(60)Co

本文描述了一起涉外钴 60污染不锈钢表带产品部件———表带拆生针剩余坯料的现场取样程序 ,从已查获的 9kg(约 3 2 1 0 0根 )表带拆生针剩余坯料中抽取 61 9根样品 ,由国内较具权威的三家放射性测量机构对各自样本独立进行测量分析 ,另一家放射性测量机构参加样品成对测量比对 ;给出了各放射性测量机构对同一总体中抽取的各自样本的测量分析结果。测量结果表明 ,所抽取的 61 9根样品中 ,有 1 41根含放射性钴 60 ;其钴 60的活度浓度值明显呈两组数据分布。对各机构测量分析的结果 ,进行了配对t统计检验 ;结果表明 :在 95 %的显著性水平下 ,没有理由认为他们测量分析的各自样本中放射性钴 60的活度浓度值不相等。对三家放射性测量机构测量各自样本中样品的放射性钴 60活度浓度值进行合并统计 ,高值组 1 43个样品 ,平均值和标准差分别为 2 2 4.8和 1 1 .9Bq/g ;低值组 3 8个样品 ,平均值和标准差分别为 72 .4和 1 1 .5Bq/g ;最大活度浓度值为 2 85 .7Bq/g;即使是单根不锈钢表带拆生针坯料样品中的最大活度浓度 ,也在某国电离辐射防护办公室通报的活度浓度 (1 0 0 0Bq/ 0 .2g)的 1 / 1 7以下。

The sampling program and measuring methods for activity concentration in spindles of watchband contaminated by cobalt 60, which were sold in some countries, are described. 619 samples of the spindle were randomly sampled from some 32100 spare spindles,of which 141 spindle samples contain cobalt 60. The distribution of activity concentration of cobalt 60 measured by 3 laboratories well known in China is given respectively. The range of activity concentration of cobalt 60 in samples is 37.9～285.7 Bq/g, which obviously present 2 groups of distribution, the average activity concentration of cobalt 60 for higher level samples is 224.8± 11.9 Bq/g ( 1σ,n =103),and for lower level samples is 72.4±11.5 Bq/g,( 1σ,n =38). The maximum activity concentration of cobalt 60 in samples given by these laboratories is 285.7 Bq/g, which is 17 times as low as 1000 Bq/0.2 g given by the Office for Protection against Ionization Radiation (OPIR) of a certain country.