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| Investigation of the Levels of 222Rn & 220Rn and γ Dose Rate in A Lead Mine of Yunnan Province |
| TANG Li1, WANG Chun-quan2, ZHOU Yu-bin2, OU Shu-ping2, YU Kai-wen2, LIU Hong-xing2 |
1. Yunnan Center for Disease Control and Prevention, Kunming 650022 China;
2. Lancang County Center for Disease Control and Prevention, Lancang 665600 China |
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Abstract Objective To investigate the radioactive level of a lead underground mine in Yunnan Province and analyze possible measures of radiation protection of the underground mine to be taken. Methods Concentrations of 222Rn & 220Rn and γ dose rate are measured in five underground holes of the lead mine with different elevation applying instant measuring technology. Results 222Rn concentration is 1 367 Bq/m3, 220Rn concentration is 24 Bq/m3, potential alpha energy concentration of 222Rn daughters, 3.04μJ/m3 and γ dose rate, 0.08μGy/h. 222Rn concentration distribution is different (P < 0.05) and 220Rn concentration distribution is identical (P > 0.05) among different monitored underground holes of the mine. 222Rn concentration distribution of monitored underground hole with the highest elevation is different from that of other every hole (P < 0.005), and 222Rn concentration of the hole is less than that of other every hole. 222Rn concentration distribution is identical between the stope and resting area of underground mine (P > 0.05), and 220Rn concentration distribution is different (P < 0.05). 220Rn concentration of the stope is higher than that of resting area of underground mine. Conclusion 222Rn concentration exceeds managed target value (1 000 Bq/m3) specified by the national standard in the underground area of lead mine. Present ventilation system of underground mine doesn't reduce 222Rn concentration effectively. 222Rn concentration of underground mine is 50 times as much as 220Rn concentration. Potential alpha energy concentration of 222Rn daughters does not outnumber specified limit value (3.57 μJ/m3) of the national standard. γ dose rate does not surpass specified limit value (1 μGy/h) of the national standard and keeps within the background range of Yunnan Province. Workers of underground mine should receive individual dose monitoring and occupational health examination.
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Received: 15 June 2013
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