Uranium mines and non-uranium radioactive mines, in order to control the precipitation of radon and reduce the hazards of radon, must comply with the following safety requirements in the development and mining process: Alnico (AlNiCo) is the first developed a permanent magnet is made of aluminum, nickel, cobalt, iron and other trace metals composition of an alloy.According to different production process is divided into sintered Alnico (Sintered AlNiCo), and cast aluminum nickel and cobalt (Cast AlNiCo).Product shape of the round and square. Sintered products limited to the small size, their production out of rough tolerance is better than the rough cast product can be better workability. Alnico Magnet,Alnico Magnets,Alnico V Magnets,Alnico Rod Magnets,Alnico 3,Alnico 5 Jinyu Magnet (Ningbo) Co., Ltd. , https://www.magnetbonwin.com
1. When designing a mine, both the development plan and the mining method must be based on the spatial extent of the limited radioactive radiation and create conditions conducive to protection. The main focus should be on reducing the source of cockroaches and their daughters, which is conducive to strengthening ventilation, rapid drainage, and reducing dust production.
2. In ore-rich areas, roadway exploration should be minimized, and hole exploration should be used instead of hole exploration to reduce the exposed surface of rock ore.
3. The roadway for mining and development shall be arranged in the surrounding rock outside the vein, that is, the “external pulse development†shall be adopted to reduce the amount of excavation work within the radioactive vein. On the one hand, this kind of extra-disciplinary development greatly reduces the exposed area of ​​radioactive ore bodies. On the other hand, the extra-vehicle roadways also create partition ventilation for the ventilation during mining, prevent series connection, form through-flow airflow, prevent air leakage and improve efficiency. Advantageous drainage conditions such as air volume rate to prevent the expansion of radioactive pollution.
4. Centralized mining operations, limiting the number of mid-sections for simultaneous mining, and the number of middle-stage operations should not exceed 4 to 5, including: middle prospecting section, mid-harvesting section, middle mining section, recovery pillar or filling middle section. Limit the number of stope mining at the same time, prevent “flowering everywhereâ€, set up mining sites everywhere, stop and stop the management disorder of the operation. This is to reduce the total exposed area of ​​the ore body and to control the precipitation of strontium.
5. Strict mining sequence, the implementation of the "from the top down, from the inside out" mining sequence; strict use of "regressive mining", that is, from the mine boundary to the direction of the central wellbore mining, a section is taken, immediately sealed off the goaf Close the gob in time to reduce the flooding of the plutonium from the goaf.
6. The mining method is preferred. In addition to selecting the mining method according to the characteristics of the deposit and the surrounding rock properties of the top and bottom plates, it is necessary to select those that minimize the exposed area of ​​the ore body, the low depletion rate of the ore loss, the low ore breaking rate, and the short residence time of the ore in the stope. There are mining methods that run through the wind. From the point of view of radioactive protection, deep hole collapse is better than shallow hole collapse; filling method is better than retention method. The deep hole caving method not only reduces the blasting workload, prevents the ore from being excessively pulverized, but also reduces the precipitation of strontium, and also reduces the amount of radioactive dust and radioactive aerosol generated.
7. Large diameter borehole ventilation. U.S. uranium mines, for gently inclined ore bodies, when the depth of mining is not large, a 1.5m diameter large borehole is used as a ventilation duct to feed fresh air from the borehole to achieve district ventilation and reduce pollution. China has mass-produced the patio cone drilling rigs , and some can also drill the ventilation wells of 800mm to 1m aperture to realize the mechanization of the patio ventilation, which is of great significance for flood control.
8. Close the mining area and isolate the exposed surface of the new ore. In order to control the precipitation rate of cockroaches and the amount of cockroaches escaping, in addition to the timely closure of the goaf, the mining roadway that has been excavated and the unexploited work surface shall be temporarily closed; the airtight material shall be used to seal , isolate the ventilation tunnel. For exposed areas of new ore deposits that are temporarily unavailable or not yet exploited, and roadways containing radioactive minerals, anti-mite protection layers such as mud should be sprayed. The theory proves that a film with a certain material thickness of 2 min on the mineral wall can reduce the precipitation rate of strontium by more than 50%. The exposed surface of rock ore is sealed with lignin sulfate, synthetic rubber, sprayed water glass, etc., and special tests are carried out in foreign uranium mines with remarkable effects. The use of polyurethane foam to close the old roadway and goaf to prevent the sputum and its daughters from polluting the main wind flow has received good results. The vinylidene chloride emulsion tested in China closes the exposed surface of the ore and reduces the precipitation of strontium by 70%.
9. Closed gobs to prevent human wind pollution. Because of the cloud tin radon comes mainly from the mined-out area and the surrounding rock fracture, so airtight construction of anti-radon isolation Gob radon precipitation plays an important role. Take the wind tunnel of the 7th district of the old factory as an example. It is located in the marble of the crack development. It is connected to the goaf at a distance of 100m from the human air outlet. The pressure-type fan is installed at 290m away from the tuyere, and the inlet section is under negative pressure. Therefore, it is polluted by the radon in the goaf and the crack. After two times of sealing, the brick wall is sealed and plastered, and the radon concentration of 280m from the human mouth is reduced from 1.47 Ci/L to 0.64×10. 10Ci/L.
10. Promote the mechanization of shipments, and remove the ore that has been collected from the tunnel as soon as possible; use remote control for drilling rigs, loading machines, and electric rafts to reduce the number of workers and promote “distance protectionâ€. More loaded with less or less retained ore in the well, reducing the precipitation of cockroaches from the gravel.
11. The roadway drainage ditch shall be provided with a cover plate and the pit water shall be discharged to the outside of the pit in time to reduce the precipitation of plutonium from the underground water.
Alnico alloys can be magnetised to produce strong magnetic fields and have a high coercivity (resistance to demagnetization), thus making strong permanent magnets. Of the more commonly available magnets, only rare-earth magnets such as neodymium and samarium-cobalt are stronger. Alnico magnets produce magnetic field strength at their poles as high as 1500 gausses (0.15 teslas), or about 3000 times the strength of Earth's magnetic field. Some brands of alnico are isotropic and can be efficiently magnetized in any direction. Other types, such as alnico 5 and alnico 8, are anisotropic, with each having a preferred direction of magnetization, or orientation. Anisotropic alloys generally have greater magnetic capacity in a preferred orientation than isotropic types. Alnico's remanence (Br) may exceed 12,000 G (1.2 T), its coercivity (Hc) can be up to 1000 oersteds (80 kA/m), its energy product ((BH)max) can be up to 5.5 MG·Oe (44 T·A/m). This means that alnico can produce a strong magnetic flux in closed magnetic circuits, but has relatively small resistance against demagnetization. The field strength at the poles of any permanent magnet depends very much on the shape and is usually well below the remanence strength of the material.
Alnico alloys have some of the highest Curie temperatures of any magnetic material, around 800 °C (1,470 °F), although the maximal working temperature is normally limited to around 538 °C (1,000 °F).[4] They are the only magnets that have useful magnetism even when heated red-hot.[5] This property, as well as its brittleness and high melting point, is the result of the strong tendency toward order due to intermetallic bonding between aluminium and other constituents. They are also one of the most stable magnets if they are handled properly. Alnico magnets are electrically conductive, unlike ceramic magnets.
Alnico magnets are widely used in industrial and consumer applications where strong permanent magnets are needed; examples are electric motors, electric guitar pickups, microphones, sensors, loudspeakers, magnetron tubes, and cow magnets. In many applications they are being superseded by rare-earth magnets, whose stronger fields (Br) and larger energy products (BHmax) allow smaller-size magnets to be used for a given application.
November 20, 2021