Design Of Nuclear Model Well And Its Gamma Ray Logging Curves Simulated With Monte Carlo Method

Based on the sub-project-Design and Construction of the Nuclear Model Well which is belonged to China Nuclear Industrial Geological Bureau's project- Research and Application to the New Method and Technology of Uranium Exploration, and after sufficient investigation to the model wells and study about the feasibility, a nuclear model well related with four logging methods (natural gamma ray logging, gamma ray spectrometry logging ,density logging and X-ray fluorescence logging) is designed in this paper. Natural gamma ray spectrometry logging instruments, density logging instruments and X-ray fluorescence logging instruments could be calibrated with this well and it is able to undertake the teaching practices of the four logging methods including natural gamma ray logging, natural gamma ray spectrometry logging, density logging and X-ray fluorescence logging. This kind of nuclear model well is initiated at home and abroad.The design of this model well contains the general layout of the well, the materials and size of its shaft, the content of radioactive materials as well as the density and size of each layer, and the materials and thickness of the radiation shielding layer. Also, the solution to the problem about the overflow of Radon from radioactive layers is furnished in this paper. In this paper, two design schemes that design scheme with low radioactivity and design scheme with slightly higher radioactivity are furnished for the design of the content of the radioactive materials in calibration layer for gamma ray spectrometry logging. In the design scheme for radiation shielding layer of the calibration layer for gamma ray spectrometry logging, two design schemes for choosing materials which are heavy concrete and common concrete are given. For each design scheme, the thickness of the radiation shielding layer is calculated with numerical method on the premise that the result could meet the requirement of national radiation protection standard. Combined with the actual situation and from the perspective of stability of this well, the final design scheme for materials and thickness of the shielding layer is put forward.The model for the calibration layer of gamma ray spectrometry logging with Monte Carlo procedure is built, then run the procedure and the output of the procedure is analyzed. According to the analysis, the final design scheme for radiation shielding layer is reasonable and feasible.Then we make use of MCNP5 to build the model for the calibration layer of gamma ray spectrometry logging and two schemes are made which are simulation of dry hole and simulation of the hole full of water. From the analysis and treatment for the output of this procedure, gamma ray logging curve simulated (counts) and gamma ray spectrometry logging curve simulated for both schemes are obtained. Based on that, gamma ray spectrometry of each probe point in the borehole is obtained. Through calculation, gamma exposure rate of each probe points in the borehole is obtained too, so the gamma ray logging curves simulated (gamma exposure rate) for each scheme are made in this paper. And analysis is given for those curves simulated.