Tungsten container
Radioactive substances commonly used in medical treatment are divided into two categories, one is radiopharmaceuticals, the other is radionuclides.
Radiopharmaceuticals refer to special drugs containing radionuclides for medical diagnosis and treatment. A radionuclide-labeled compound or biological agent used in the body for medical diagnosis or treatment. Such as radiation therapy drugs 32P, 89Sr and 90Y that emit pure β -rays.
Radionuclides: for example, 226 radium is a natural radioactive source. Due to its long half-life, it has been replaced by artificial radionuclides of 60 cobalt, 137 cesium and 192 iridium.
In order to protect workers from radiation damage, the national regulations on radiation protection stipulate that the maximum allowable amount is 5Rem (measurement of radiation exposure unit). The basic principles of radiological protection are:
1. Reduce the exposure dose
The amount of exposure is proportional to the radioactive intensity of the source. In the case of not affecting the work, the amount of operators should be reduced as far as possible, so that it is within the allowable standards formulated by the state.
2, shorten the exposure time
Exposure increases with time of exposure. Under the condition that the quality of medical care is guaranteed, the work should be done quickly and the stay time around it should be reduced.
3. Increase the radiation distance
The exposure is inversely proportional to the square of the distance. Long handle tools or manipulator can be used for remote operation to reduce the amount of radiation, so as to protect workers.
4, increase protection shielding
The use of protective barriers, such as tungsten alloy shielding containers, can effectively reduce exposure. Tungsten alloy shielding vessel can shield up to 80% of the radioactive material contained.
The main function of tungsten alloy shielding vessel is to shield radioactive materials. It is made of high gravity tungsten alloy as production material. Studies have confirmed that the shielding of heavy metals is produced by density, and the higher the density, the better the shielding. The density of high specific gravity tungsten alloy can reach 16.5-19.0 g/cm3, which has a good shielding effect on radioactive substances. Compared with existing lead shielded tanks, tungsten alloy shielded containers show more environmental advantages. Tungsten alloy itself non-toxic will not produce radioactive substances, waste parts can be recycled processing without pollution.
Sintering process is the main production process of tungsten alloy shielding vessel. Sintering is a heat treatment process, the strength and density of the compact or powder body are very low. In order to improve the strength of the billet or powder body, heat treatment is required under appropriate conditions. This is to heat the billet or loose powder body to the temperature below the melting point of its basic components (about 0.7~0.8T absolute melting point), and hold the heat at this temperature, so as to combine the powder particles and improve their performance.
Sintering has a decisive effect on the properties of tungsten alloy shielding vessel. The result of sintering is that the powder particles bond together, the sintered body increases in strength and, in most cases, in density. In the sintering process, the billet to undergo a series of physical and chemical changes, the beginning is the evaporation or volatilization of water or organic matter, the elimination of adsorbed gas, the elimination of stress, the reduction of oxide on the surface of powder particles; This is followed by interatomic diffusion, adhesive flow and plastic flow, the increase of contact surface between particles, recrystallization, grain growth and so on.
