Investigation And Evaluation Of Radiation Environment Of A Typical Decommissioned Uranium Mining And Milling Facilities

So far, acceptance of treatmentent engineerings of 14 retired uranium mine had been completed in china, two of which was transferred to local management institutions in 1995, and the other of which are under working at present. According to the need of the treatment work, a large number of retired management of the scientific research work had been carried out. Guiding ideology, the implementation of the principle, the technical route of the uranium mining facilities and radioactive waste management had been basically established.This article chose the domestic retired uranium mining and milling facilities in Jiangxi Province as the research object, which had completed governance over years. Monitoring program has been developed according to the corresponding national standards. With radon exhalation rate, the concentration of radon and its daughters, γ air and soil absorbent rate of uranium, distribution of natural radionuclide’s radium as a data collection object, this paper studied the radiation environment of the mine situation. In this paper, with the mine and the surrounding areas as the study of space, the radiation environment of the region were evaluated from the perspective of irradiation and external irradiation, in accordance with the basic requirements of the nuclear industry radiation of environmental assessment and dose estimation models.Monitoring results: average radon emanation rate after treatment of the mine decommission was 0.406 Bq/(m2·s), below 0.74 Bq/(m2·s) the regulatory limits of Technical regulations for the environmental management of decommissioning of uranium mining and milling facilities. The average radon emanation rate of main tailings, deputy tailings, hydrometallurgy plant and dump were respectively 0.4366 Bq/(m2·s), 0.367 Bq/(m2·s), 0.441 Bq/(m2·s) and 0.339 Bq/(m2·s). Gamma radiation levels, on average, is 11.37×10-8Gy/h, below(6.93 + 17.4) ×10-8Gy/h, the regulatory limits of Technical regulations for the environmentalmanagement of decommissioning of uranium mining and milling facilities. Gamma air mean absorbed dose rate of main tailings, deputy tailings, hydrometallurgy plant and waste dump were respectively 6.29 ×10-8Gy/h, 7.48 x 10-8×10-8Gy/h, 17.78 ×10-8Gy/h and 13.94 ×10-8Gy/h; Annual radon release a quantity was 28.4×1011 Bq, the average radon concentration is 43.34 Bq/m3. Average radon concentration of main tailings, deputy tailings, hydrometallurgy plant and waste dump were respectively 44.2Bq/m3 and 38.8 Bq/m3, 52 Bq/m3 and 48.2 Bq/m3, potential unequilibrium radon concentrations were 75.8 nJ/m3, nJ 89.63 nJ/m3 and 89.63 nJ/m3 and 61.11 nJ/m3,below regulation limit 416 nJ/m3(0.02WL), the regulatory limits of Technical regulations for the environmentalmanagement of decommissioning of uranium mining and milling facilities. But there are individual radon exhalation rate measurement point to exceed bid in deputy main tailings, the tailings, hydrometallurgy and waste dump. Radium content of uranium soil samples of 1 #, 2 #, 3 #, 4 #, which were in the south of the main tailings and the deputy tailings, and of # 12 which was to the west of hydrometallurgy plant exceeds bid.It shows the mine management is not perfect enough, and need to further improve the governance.This article adopted the model to estimate the influence of 222 Rn and their daughter on the surrounding environment. The results are as follows: the maximum of radon concentration in the air is 1.23 Bq/m3, which appeared in the ESE orientation, and of which the evaluation center located in 0~1 km area; individual effective dose of children’s random caused by radon and its daughter was 0.0194 mSv, whose center of the evaluation was ESE, locating in 0~1 km area; the maximum potential individual effective dose of children’s random was 0.0957 mSv/a, whose center of the evaluation was in E, locating in 0~1 km azimuth area; public collective effective dose within the 80 km evaluation scope caused by inhalation of unequilibrium radon and its progeny was 0.1889 Sv, below 1 mSv the specified value of Basic standards for protection against ionizing radiation and for the safety of radiation sources.