| Chongqing city is rich in mineral resources,and has a great variety and production in mineral。Besides contain demanded mineral component,all these minerals also associated some natural radioactive material which exceeds standard rate。because associated mineral contains natural radioactive nuclide in a higher level,in the processes of exploit,refining,machining,and utilized,these natural radioactive materials contained in associated mineral will be migrated,concentrated,and diffused,the product and waste which contains natural radioactive nuclide will also lead radioactive pollution to the environment in some degree。Therefore,the research on radioactive pollution present state in the process of mineral deposit exploit and utilize will supply basic data and science fundamental for protect human healthy and make radioactive pollution prevention policy。This dissertation is supported by the Chongqing EPA research subject《the investigation of associated radioactive mineral in chongqing》,according to 1643 coal minerals and 2830 non-coal minerals in whole city,seclect 20 typical mining area as research target。By means of field survey ,sampling and laboratory analysis,we abtained some data in these aspect:γradioactive-dose level in mineral deposit ground;Rn-222 concentration in air,Ray-226,Th-232and K-40 radioactive specific activity in mineral and ambient soil ;tatalα,βcontent in water around mine。Research result shows thatγ-radioactive dose rate difference in each mine is obvious,these data ranged in 61 nGy/h-439 nGy/h,the average value is 119.8 nGy/h,the maximalγ-radioactive dose rate occurres in Jixing mine of Nanchuan。By the model predictive,the maximal effectiveγ-radioactive dose in public and occupation is 0.54 mSv/a and 0.61 mSv/a,which all below year limited value(1mSv/a,20mSv/a)。Rn-222 concentration in 20 mines ranged in 8.29-617 Bq·m-3,the average value is 83.55 Bq·m-3,the predicted result of internal radioative dose shows that internal radioactive dose in these three mine all exceed year limited value,but year career radioactive dose is below limited value。Among all the nuclides in Tianshengqiao coal mine in Qianjiang,Nanchuan Jixing and zengzi rock and aluminum mine ,the specific activity value of Ra-226 is obviously higher than the maximal measurement value in soil of reference point,in Nanchuan zengzi rock and aluminum mine,the specific activity value of Th-232 is obviously higher than the maximal measurement value in soil of reference point,however,the specific activity value of all mines are general below the average value in soil of reference point。Through the preliminary research to the 20 mines,and deeper research in part of mines with the higher radioactive level。The result suggest that the value of store field for product of coal and coal cinder is obviously higher than tailing pile,ambient soil and vegetable plot,it also higher than the maximal value in environment reference point。The higher 222Rn concentration points are all distributed in pit and well of mine。Totalα,βcontent in mine water is obviously higher than drinking water in adjacent area,while drinking water in mine area is higher than drinking water in urban that mine belongs to。This dissertation discussed the identification criterion of associated mine,it suggests that based on the calculation formula of internal radiation index IRa=ARa/400 and external radiation exposure index Iγ=ARa/330+ATh/260+AK/3800,when it is satisfied IRa≥1 or Iγ≥2,then it is identified as associated mine。Through calculate verify,the result we gained is very good ,γ-radioactive dose rate is significant correlated in level 0.01 with internal radiation index and external radiation exposure index;according to the calculate result,the IRa of Jixing coal mine is 1.90,Iγis 2.43,the result indicates it belongs to associated mine。The innovation of this dissertation rest on first research to ionizing radiation level in all typical mines of chongqing,makes clear the radioactive pollution state in mineral exploiting and utilizing processes,then compared with environment reference point,predicted the radiation dose to public and professional personnel,and innovately discussed the identification criterion of associated mine in china。...
|
PDF Full Text Request