The Study Of Affecting Factors And Correct Method For In-situ Gamma-ray Spectrometry

With the development of China's nuclear power industry, the demand for the uranium ore resources will be increasing inevitably, also accompanied by a series of environmental problems of ionizing radiation. In situ gamma-ray spectrometry, as a conventional nuclear geophysical technology, widely be used in uranium deposits in geological exploration, environmental monitoring. However, the gamma-ray spectrometry is often affected by the surface soil thickness,density, humidity, topography and other factors and the measurement results are existence of the larger error.This article from the in situ gamma-ray spectrometry basic principles, calculated the different material quality attenuation coefficient and linear attenuation coefficient, and in accordance with single-energy gamma-ray photon theoretical model studied the different soil thickness, density, humidity and terrain on primary photon fluence rate impact. The results showed that with the increase in the thickness of soil, surface primary photon fluence rate increased rapidly. In the soil of 40,60,60,70cm thick, 662,1460,1760,2620 keV energy peaks of the characteristics of the primary photon fluence rate were reaching saturation, gamma-ray spectrometer at the effective detection within 1 m in depth. Surface primary photon fluence rate with the density of soil, moisture was negatively correlated, with the terrain from the perspective of the detection equipment was positively correlated. When the density of soil from 1.60 gcm-3 to 1.9 gcm-3, 662, 1460, 1760 and 2620 keV characteristics of the primary energy-photon fluence rates were reduced 11.62, 12.10, 12.52, 13.39%, the changes of density were greater impact on high-energy gamma photon. When the humidity from 10% to 20%, 662,1460,1760 and 2620 keV characteristics of the primary energy-photon fluence rates were reduced by 10.74, 10.53,10.38, 9.98%, humidity changes were greater impact on low-energy gamma photon. When the instrument detection angle from 180 degree to 270 degree, 662,1460,1760 and 2620 keV characteristics of the primary energy-photon injection of a growth rate of 50.00%, that is the point of detection change on different impact on the same photon energy.In addition, under the experimental field of soil conditions and scale models of different conditions, the field of soil conditions normalized to the scale model and established correct model, and corrected parts of Shanxi survey results. By density, humidity, density and humidity three ways to correct that the average thorium activity relative error reduced from 13.97 percent to 2.97, 2.73, 2.99%, that the corrected thorium activity significantly reduced the average relative error, but after that the radium, kalium activity has increased an average relative error, so this method also needs further in-depth study.