The Application Of Nuclear Geophysical Methods For Prospecting Uranium Deposits

With the high-speed development of nuclear power station construction in China, the demand of uranium fuel also appears a rapid growth. The proven uranium reserves in China are limited. In order to solve the problem of nuclear fuel supply, it is necessary to research uranium exploration methods deeply. People determined the location of ore bodies according to the geophysical anomaly measured. The diffusive convection theory thinks that the migration distance of radon is only a few dozen meters, so it can not explain the radon anomaly above the deep uranium deposits. In this paper, I summarized the articles about uranium geophysical exploration and radon migration, studied on the characteristics of geophysical field in uranium deposits and the formation mechanism of radon anomaly, and ultimately reached the following conclusions:(1) Uranium deposits are mainly distributed at the gravity lineament and magnetic anomaly areas with gentle variations. The gravity anomaly varies stably at sandstone-type uranium deposits and varies greatly at granite-type uranium deposits. Uranium deposits usually have high polarizability and low resistivity, but the resistivity at paleochannel sandstone-type uranium deposits appears slightly high value anomaly. Interlayer oxidation zone sandstone-type uranium deposits locate at the inflexion of spontaneous potential curve. The wave impedance at sandstone-type uranium deposits is relatively high.(2) Actions of groundwater-carrier and geogas lead to 3 uranium concentration areas: dispersion halo area, groundwater table area,and geochemical barrier near earth surface. These uranium concentration areas shorten the migration distance of radon. The dynamic actions of radon migration are not limited to diffusion and convection. Because actions like clusters effect play a great role in deep subsurface, the real migration velocity of radon is faster than the calculation speed considering diffusion and convection merely.(3)There are primary halos and secondary halos in granite-type uranium deposits and volcanics-type uranium deposits, while the primary halos and secondary halos usually not exist in sandstone-type uranium deposits.High value surface anomaly of radon appears on the top of orebody in granite-type uranium deposits and volcanics-type uranium deposits,and appears on the edge of orebody in sandstone-type uranium deposits. Compared with granite-type uranium deposits and volcanics-type uranium deposits, influence of groundwater-carrier effect is relatively weak in sandstone-type uranium deposits.