| The waste produced by various radioactive substances is called "nuclear waste".For some nuclear waste with short radiation period and low radiation,it is generally sealed in storage tank to make its natural decay radiation become ordinary waste and then treated directly.However,the storage and installation of some high radiation nuclear waste is still an urgent problem because of its long decay period and high corrosiveness.If not treated Properly,the leakage of radioactive materials will cause environmental damage,directly affect the survival of human beings and animals,and cause irreversible impact.Because of its wide range of hazards,for the treatment of high-level radioactive nuclear waste,many countries generally separate and solidify the package,which is deeply buried in a relatively stable rock layer several thousand meters underground.In this paper,the ultra-low frequency method is used to detect the underground rock strata and select the rock strata suitable for high radioactive nuclear waste storage.The extremely low frequency method(ELF-CS)is the abbreviation of the artificial source extremely low frequency electromagnetic method(ELF-CS).Because of its wide coverage,two positive connecting ground antennas of several thousand meters are used to form a large range of "ground grid" at both ends of the antenna as the grounding body to transmit 0.1Hz-300 Hz extremely low frequency signals.In practical application,because of the stable signal,wide coverage,high signal-to-noise ratio,small interference in the transmission process,large detection depth,light and fast equipment,saving the difficulty of manual handling heavy instruments,simple operation,overcoming the defects and difficulties of other electromagnetic methods for deep detection,it is a new detection method and method for geologists and researchers Technology.A large number of data show that the ELF method not only has a good effect on earthquake prediction,but also has accurate detection and budget for deep prospecting,water resources exploration,deep rock exploration,etc.In this thesis,the ultra-low frequency method is mainly used to find a place where the information of strata is stable and suitable for nuclear waste storage.When the lake Arctic low frequency transmitter sends out the ELF signal,it uses the primary field generated by the transmitter in the waveguide area as the source,and the electromagnetic wave propagates vertically to the underground.According to the conductive medium in the underground rock,it generates eddy current,which propagates upward as the secondary field and penetrates the ground and faces upward.At this time,it is considered that the resultant field is obtained.The apparent resistivity is obtained through impedance analysis The amplitude and phase change can reverse the deep underground structure.Because the underground environment is complex and diverse,the intrinsic parameters of different substances are different.The calculation of apparent resistivity in this paper involves the dielectric constant,permeability and conductivity of underground substances.In the laboratory,impedance analyzer is used to measure the changes of these three parameters with frequency.It is verified that the effect of the change of permittivity and permeability on the change of apparent resistivity can be ignored,and the main factor affecting the apparent resistivity is the change of conductivity.In the research of the detection method of the nuclear waste storage area by the extremely low frequency method,a system of detecting the nuclear waste storage area by the ELF method is designed by using the software radio technology,and the overall scheme design,hardware system design and software system design of the system are carried out.It is very important to detect the distribution information of the underground medium effectively and to study the combination of the conductivity of the substance and the underground electricity for the detection of the deep underground structure. |
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