Study On Radioactive Contamination Behaviors And Its Removal Technology From Diferent Uranium Mining Industry Materials

Radioactive contamination is one of widely concerned pollution problems in today’s society.It causes not only great damage to the ecological environment,but also serious damage to human health.The uranium mining industry in China has the characteristics of unbalanced distribution of uranium ore,complicated technology and large employees,so the radioactive contamination is urgent to be managed.Therefore,it is very important to explore the rules of radioactive contamination and its decontamination process.At present,scholars at home and abroad have carried out some researches on the rules of radioactive contamination and its decontamination process,but there are few researches about the contaminated materials widely used in uranium mining industry.Aiming at the rules of radioactive contamination and the problem of removal,firstly,several common materials（stainless steel,PVC,plexiglass and rubber）in uranium ore metallurgy were selected as the research samples.The existing forms of uranium on the samples surface,the change of quality of samples before and after contaminated,the change of the surface morphology characteristics of the samples under different acid and alkali systems,the variation of uranium with corrosion depth in the sample section all were investigated.Secondly,the effects of decontamination time,nitrate concentration,temperature and ultrasonic wave on the cleaning effect of radioactive contamination on the surface of four kinds of materials（PVC,plexiglass,stainless steel and rubber）were studied.Specific research results include the following two aspects:1.Radioactive contamination rules of common materials in uranium mining and metallurgyThe experimental results show that under the carbonate system,as the concentration of uranium solution is 56.24 mg/L,the surface pollution activity of four kinds of materials is similar,and as the concentration is488.40 mg/l,it can be seen that the surface contamination activity of rubber is larger than the other three kinds.As the concentration is 4.58/L,the surface contamination activity of rubber is the largest,the second PVC,stainless steel and plexiglass are not significantly different;rubber is the most susceptible to radioactive contamination in four materials,followed by PVC,and the changes in surface pollution activity of stainless steel and plexiglass are similar;from SEM analysis,The difference of radioactive contamination of each material is mainly affected by the degree of roughness and loosening of the surface.The rougher of the materials surface,the higher surface contamination degree.Under the nitric acid system,as the uranium concentration is larger than a certain value,the starting value of the surface contamination activity of each material ranking from large to small is rubber>Stainless steel>Plexiglass>PVC,the growth rate in turn is rubber>Stainless steel>Plexiglass>PVC.That means,rubber is the most susceptible to radioactive contamination,the stainless steel second,and finally Plexiglass and PVC;combined with sample quality changes,sample surface and cross-sectional SEM analysis results,it is clear that the increasing of radioactivity of each material is mainly due to the oxidation corrosion of the sample in the acidic uranium solution;From XPS analysis,uranium on the sample surface exists mainly in the form of UO₂（NO₃）₂·6H₂O and UO₃.2.Study on radioactive decontamination of common materials in uranium miningIn the condition of 32℃and 2%nitrate,four materials decontaminated with ultrasonic,its decontamination efficiency increased with cleaning time;Also the cleaning efficiency has been improved with the higher nitrate concentration;Except for rubber,the other three materials are decontaminated in nitric acid concentration of 8%1 hours,the contamination activity value can be less than 1 Bq/cm²;Ultrasonic assistance can improve the cleaning efficiency,but the improvement of different materials is different,the improvement ranking from large to small are rubber>PVC>Stainless steel>plexiglass;It is obvious that temperature effect on the cleaning efficiency,and the improvement of cleaning efficiency of different materials from large to small is:Plexiglass>PVC>Rubber>stainless steel.