Improving Gross Count Gamma-Ray Logging in Uranium Mining With the NGRS Probe

Abstract

Abstract-AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration measurement by means of gamma ray logging. The determination of uranium concentration in boreholes is performed with the Natural Gamma Ray Sonde (NGRS) based on a NaI(Tl) scintillation detector. The total gamma count rate is converted into uranium concentration using a calibration coefficient measured in concrete blocks with known uranium concentration in the AREVA Mines calibration facility located in Bessines, France. Until now, to take into account gamma attenuation in a variety of boreholes diameters, tubing materials, diameters and thicknesses, filling fluid densities and compositions, a semi-empirical formula was used to correct the calibration coefficient measured in Bessines facility. In this work, we propose to use Monte Carlo simulations to improve gamma attenuation corrections. To this purpose, the NGRS probe and the calibration measurements in the standard concrete blocks have been modeled with MCNP computer code. The calibration coefficient determined by simulation, 5.3 s-1. ppmU-1 ± 10%, is in good agreement with the one measured in Bessines, 5.2 s-1. ppmU-1. Based on the validated MCNP model, several parametric studies have been performed. For instance, the rock density and chemical composition proved to have a limited impact on the calibration coefficient. However, gamma self-absorption in uranium leads to a nonlinear relationship between count rate and uranium concentration beyond approximately 1% of uranium weight fraction, the underestimation of the uranium content reaching more than a factor 2.5 for a 50 % uranium weight fraction. Next steps will concern parametric studies with different tubing materials, diameters and thicknesses, as well as different borehole filling fluids representative of real measurement conditions.

Analysis and Research on Working Performance of Shearer Based on Discrete Element Method

“…As a key index for evaluating the working performance of the shearer, the coal mining rate directly affects the productivity, load fluctuation, tool wear, dust output and dynamic reliability of the shearer [8]- [14]. With the rapid development of the world economy and coal industry, more and more scholars and manufacturers have applied different methods to the study of fully mechanized mining face shearers.…”

“…With the rapid development of the world economy and coal industry, more and more scholars and manufacturers have applied different methods to the study of fully mechanized mining face shearers. Most of the studies on shearer mining rate are theoretical research, tests and finite element analysis [8], [15]- [17]. Miller et al studied the influence of hydraulic fracturing on the coal mining rate and constructed a method to improve the coal mining rate of thick and hard coal seams through pulse water prefracturing technology [18].…”