Gas-Liquid Two Phase Coupling Model And Engineering Application For Radon Transport In Loose Fragmented Radioactive Medium

In-place leaching of explosively fragmented uranium ore is an economic and high efficiency mining technique suitable for recovering uranium from low grade hard-rock type uranium ore body. However, the air pollution in place leach stope caused by the radon from the fragmented uranium ore is a sever problem which needs to be solved as soon as possible. The regularity for radon transport in the uranium ore heap to be leached in the underground stope is a fundamental research subject for controlling the air pollution caused by radon by ventlation, which is of great significance both in theory and practice for the safety production, green mining of uranium resource and sustainable development of uranium mining and metallurgy industry.This dissertation was supported by the National Natural Science Foundation of China project-studies on multi-phase and multi-process coupling model and numercial simulation for radon transport in loose fragmented radioacive medium (No.10575048). The uranium ore heap to be leached in the underground stope was simplified as a kind of radon emanating loose media, and studies were carried out on the radon migration through gas-liquid two-phase fluid in loose fragmented radioactive medium using analytical method, physical modeling, numerical modeling and field test. The main innovative achievments are summed up as follows:(1) The self-developed apparatus for the research of gas-liquid(water) single-phase and two-phase seepage in loose fragmented radioactive medium was patented in China. Base on the characteristicse of the particle size distribution of the uranium ore heap to be leached in the underground stope, seven samples were prepared with different particle size distributions in obedience with Rosin-Rammler distribution law. The apparatus was used to study the influence of characteristic particle size, particle size distribution index, porosity and saturation of the medium on gas-liquid(water) two-phase seepage。(2) On the basis of the test results of gas-liquid(water) two-phase seepage, the Artifical Neural Network(ANN) models for predicting gas-liquid(water) two-phase effective permeability were established using BP neural network algorithm from the characteristic particle size, particle size distribution index, porosity and saturation. And the method which could predict gas-liquid two-phase effective permeability of prototype on the basis of model test is established using dimension analysis.(3) The self-developed apparatus for measuring transient radon emanation capability and proposed method for calculating transient radon emanation capability in loose fragmented radioactive medium was also patented in China. Seven samples were prepared with different particle size distributions in obedience with Rosin-Rammler distribution law, the apparatus was used to measure the variation of radon concentration of seven samples with time, and to study the influence of the radon concentration,characteristic particle size, particle size distribution index and moisture of the medium on the transient radon emanation capability.(4) The test results on transient radon emanation capability were used to establish the Adapive Neuro-Fuzzy Inference System(ANFIS) models for predicting transient radon emanation capability from radon concentration,characteristic particle size, particle size distribution index and moisture. And the method which could predict transient radon emanation capability of prototype from the model tests was proposed using dimension analysis.(5) The principles of two-phase flow through a porous medium, radon migration by diffusion and seepage, radioactive decay and regular pattern of radon dissolved in water was used to establish gas-liquid two phase coupling model for radon transport in loose fragmented radioactive medium.(6) The Computational Fluid Dynamicis(CFD) model was established to simulation the radon migration through gas-liquid two-phase fluid in the uranium ore heap to be leached in the underground stope. The simulation results of radon concentration distribution and emanation in uranium ore heap and the stope provided the theoretical proof for controlling air pollution caused by radon in the stope.