| Thorium in the crust in the reserves than uranium enrichment,thorium fuel for nuclear power technology has been pilot development,thorium resources development and utilization has been put on the production schedule.In this paper,the method of radioactive detection in block-like thorium ore on-line mineral processing(inspection)was studied.The thorium ore beneficiation on-line detection device was designed.MCNP5 was used to simulate the shape and volume of thorium ore,the placement of the detector,the thickness of the conveyor belt,Shielding thickness,scintillator volume,ore spacing and other factors on the ray on-line γ measurement,and through the experiment on the placement of the detector,the detector spacing and ore spacing to be verified,and the determination of the on-line detection device The detection limit.The results of the research are as follows:(1)From the simulation: For the NaI(Tl)detector of Φ50 × 100mm3,when the volume of the ore is less than 100 cm ^ 3,the detection efficiency of the vertical placement of the detector is greater than that of the horizontal display mode.In the 343cm3 ~ 500cm3,the detector placed in the horizontal detection efficiency of vertical placement detection efficiency of 1.2 times,when the ore volume is greater than 500cm3,raised to 1.5 times.Through the physical test,it is concluded that the detection efficiency of the horizontal display is larger than that of the vertical placement method for the NaI(Tl)detector of Φ75 × 75mm3,and the detection efficiency ratio is about 1.1.(2)From the simulation: for the thorium characteristic γ activity of 5000 Bq / kg of ore,the adjacent thorium ore center spacing in the 5cm ~ 55 cm change,the horizontal display detector from the rate of 5.48 cps into 1.334cps;vertical placement of the detector,the resulting count rate from 5.14 cps to 1.28 cps.Through the physical test,it is found that the detection rate of the detector should be set in the design of the on-line detection device when the γ-ray energy is 2.62 MeV energy window(2.53 MeV ~ 2.67MeV)and the counting rate decreases with the increase of the detection distance.As short as possible,can effectively improve the detection efficiency,adjacent ore spacing should be set as much as possible,can effectively improve the accuracy of ore sorting.(3)When the thickness of the lead shield is greater than 8mm,the effect of the surrounding γ emission rate can be reduced to 1.699 × 10-3cps.(4)Thorium ore on-line detection device for thorium ore in the measurement time of 1s when the device detection limit of 0.067 cps,so to meet the requirements of online testing.This experiment is subject to conditions,some experiments are not perfect,so some understanding may also be more superficial,to be further study in the future. |
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