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Radioactive protection in rare earth production
According to the characteristics of radioactive hazards, the radiation protection during the production of rare earths should follow the following three principles.
1 Try to shorten the exposure time or the time possible for exposure. For radioactive operations, it is necessary to shorten the operation time;
2 create conditions to set a shielding object between the radiation source and the human body;
3 Increase the distance between the radiation source and the human body, so that the radiation is weakened and the dose is reduced.
The above principles should be carefully observed in the process of rare earth production, especially in workplaces and processes where the radioactivity exceeds national standards, and the possible radiation hazards should be minimized.
Accordingly, the following aspects should be noted for radioactive protection in the production of rare earths.
First, the site should be reasonably selected and the plant area should be properly planned. This is the basis of radiation protection. The newly built plant area shall be arranged on the downwind side according to the local dominant wind direction. Try to avoid the original permanent building so that it is not in the protection monitoring area. When the conditions are not conducive to emissions, the scope of the protection monitoring area should be expanded.
In accordance with the requirements of national standards, Class A and Class B workplaces may be arranged according to the principle of the three districts. The layout of the three districts is shown in the figure below. The main arrangement principle is that the living area, office area and production plant area are strictly separated and have a certain distance. According to the local leading wind direction, the production workshop and the “three wastes†treatment site should assist the downwind side of the workshop and office, and the living area should be located on the upwind side of the plant.
Health
live
Area
"Three Wastes" Treatment Plant
Uranium , thorium , radium recovery pure workshop or rare earth production section with large concentration of radioactive dust
Auxiliary workshop
health
Passing through
office
laboratory
In the picture, the rare earth production plant uranium, thorium and radium recovery pure workshop or radioactive dust precision rare earth production section three-zone configuration diagram
The sanitary passage should include a dressing room, a shower room, a laundry room, and a surface radioactive contamination monitoring station. The flat layout of the sanitary passage should completely separate the clean area from the contaminated area, with special passages and showers between them.
Secondly, choose reasonable technology and advanced equipment to improve the level of mechanization and automation of production, so that the radioactive production site can achieve long-distance or shielding operation. In the case of process and economic conditions, wet processes should be used as much as possible to reduce dust. Use advanced technology and equipment to treat radioactive waste, comprehensive utilization, and reduce pollution. In the production of rare earths, the process of preferential separation of uranium, thorium and radium is used to create non-radioactive or low-radiation operating conditions for subsequent processes, minimizing the scope of radioactive hazards.
Third, the ventilation should be strengthened for dusty processes and places where Rn and Tn can be generated. In the industrial production of rare earths, the design of the plant is generally naturally well ventilated. The concentration of Rn, Tn and its daughters in the workplace does not exceed the maximum allowable concentration, and special protection facilities are usually not required. Only in a very small number of mines, underground belt corridors and warehouses, Rn, Tn gas and its daughters have a slightly higher concentration, and ventilation can be used to reduce the concentration.
Fourth, since the radioactive contamination of the surface of the worker may enter the inside of the body through the digestive tract and the skin, the radioactive contamination of the equipment and the ground can also enter the workplace air through sorption and suspension, and enter the human body through the respiratory tract. Therefore, the floor, walls and facilities, utensils, personal appliances, etc. in the workplace are frequently cleaned to remove radioactive contamination on the surface. When working in a radioactive area, the staff should be personally protected. The masks, gloves, and overalls must be complete. If necessary, wear protective glasses. Do not eat or smoke in the workplace.
In short, the radioactivity in the production of rare earths is objective. In addition to taking reasonable protective measures, strengthening radioactive protection management, conscientiously implementing radiological protection regulations, overcoming paralysis, is also an important part of radiological protection. Of course, it is also necessary to correctly understand the radioactivity in the production of rare earths. It is also a fact that the production of rare earths is a low-level radioactive industry. It is not possible to exaggerate its radiological hazards and waste food and affect production.
references
1, in addition to light Gazette editor, rare earths, 2nd edition, Beijing: Metallurgy Industry Press, 1995
2, GB 11719-89
3. GB 17053-1997
4. GB 16228—1996
5. GB 16245—1996
6, GB 16240-1996
7. Lin Hecheng, Design of Nonferrous Metals, 1997, 24(1): 60
8, GB 8978-1996