我国非铀矿山222Rn和220Rn水平初步调查研究

目的 测量非铀矿山²²²Rn、²²⁰Rn水平,了解我国矿山氡超标比率和矿工受照剂量。方法 根据典型抽样方法选择12个省17类44座矿山,采用LD-P分辨型探测器测量²²²Rn、²²⁰Rn累积浓度。结果 ²²²Rn、²²⁰Rn浓度呈对数正态分布,金属矿(25座,147处)²²²Rn浓度算数均值(AM)和几何均值(GM)分别为(1211±2359)和(311±5.5) Bq m³;²²⁰Rn浓度AM和GM分别为(269±700)和(71±4.4) Bq m³。非金属矿(18座,118处)²²²Rn浓度AM和GM分别为(98±207)和(55±2.5) Bq m³;²²⁰Rn浓度AM和GM分别为(60±76)和(38±2.4) Bq m³。测量地下矿井40处,其中6处²²²Rn浓度均值超过1000 Bq m³ (工作场所氡浓度限值),占抽样率15.0%;约有7%测点²²²Rn超过浓度3700 Bq m³ (我国铀矿冶氡浓度限值),个别测点超过10 000 Bq m³。井下和地面工作区室内²²²Rn平衡因子分别为0.33±0.15和0.47±0.18。²²⁰Rn平衡因子的波动范围较大,为0.001～0.032。地下矿山矿工的年均受照剂量约为8.15mSv。结论 我国金属矿山特别是有色金属矿井下²²²Rn浓度偏高的问题依然严重,值得关注和进行跟踪研究。

A preliminary investigation of 222Rn and 220Rn levels in non-uranium mines in China

Objective To measure levels of ²²²Rn and ²²⁰Rn in typical non-uranium mines, China, and to estimate dose from the occupational radon exposure in the miners.Methods Using typical sampling scheme, 44 mines were selected in 12 provinces, which can be classified into 4 categories and 17 types of mines. The radon-thoron discriminative detectors were used to measure ²²²Rn and ²²⁰Rn concentrations in mines.Result The concentration of ²²²Rn or ²²⁰Rn was log-normally distributed. The arithmetic mean (AM) concentration and geometric mean (GM) concentration of ²²²Rn and ²²⁰Rn in 25 metal mines (n=147) were estimated to be (1211±2359) Bq m³ (AM) and (311±5.5) Bq m³ (GM), and (269±700) Bq m³ (AM) and (71±4.4)Bq m³ (GM), respectively. The mean concentrations of ²²²Rn and ²²⁰Rn in 18 non-metal mines (n=118) were (98±207) Bq m³ (AM) and(55±2.5) Bq m³ (GM), and (60±76) Bq m³ (AM) and (38 ± 2.4)Bq m³(GM), respectively. In total, we measured ²²²Rn concentration in 44 underground mines,6 of them, accounted for 15%, with the mean radon concentration exceeding 1000 Bqm^-3 (limit of workplace in China). Approximately 7% of radon concentration in mines measured were higher than 3700Bq m³ (current limit in uranium mine in China), some points even exceeded 10?000 Bq m³. Based on this typical measurements, the equilibrium factor for ²²²Rn was estimated to be 0.33±0.15 in underground mines and 0.47±0.18 in nearby houses. Equilibrium factor for ²²⁰Rn ranged from 0.001 to 0.032. Using the data obtained in this typical survey, the average annual effective dose of underground miners exposed to radon and thoron was estimated to be 8.15 mSv/a.Conclusions High levels of ²²²Rn exists in metal mines, such as copper, tin, lead and zinc, gold, and aluminum mines among others. More study and administrative measures are needed to address the radiation protection of workers occupationally exposed to high radon in mines.