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Uranium mining, ore difficult to distinguish visually, geophysical methods may be utilized radioactive ore body, the grade is determined, check points and mineral stone.
I. Cataloging of radiation sampling
The task of radiation sampling and cataloging is to conduct radioactivity measurements on the surface of the exposed ore, determine the thickness and grade of the ore body, delineate the ore body boundary, guide the mining work, calculate reserves and losses, and deplete. Radiation sampling is divided into γ sampling, γ energy spectrum sampling, γ-β comprehensive sampling, all of which are quantitative measurements, and the cataloging is semi-quantitative measurement, only for γ equivalent map or grade equivalent map.
There are two methods for gamma sampling and cataloging: two-measurement difference method with lead screen and no lead screen; and one measurement orientation method for automatic elimination of interference. The thickness of the ore body is determined by the 1/2 maximum strength method (see Figure 1) and the given strength method (see Figure 2). The given intensity ΔI value is calculated according to formula (1):
Figure 1 1/2 maximum density method to explain the thickness of the ore body
Figure 2 Schematic diagram of determining the ore body boundary by a given intensity method
â–³I=U o AK p (1-S e )100 (1)
Where U o - the uranium ore boundary grade;
A - conversion factor, γ / (0.01% U).
After finding the area S surrounded by the anomalous curve and the ore body thickness H, the uranium grade U can be calculated according to formula (2):
The line spacing is 25-100 cm in the mineralized section and 100-200 cm in the non-mineral section. The measuring point spacing is generally 20cm, and the special case is encrypted to 10cm.
Second, the stope geophysical follow-up sampling
Geophysical follow-up sampling is one of the main processes of uranium mining and is the key to guiding normal production and reducing loss and depletion. The gamma sampling is performed on the working face or the roof of the stope according to a certain degree of mesh, and the boundary of the ore body is delineated to indicate the mining direction. The blasting gamma measurement is performed on the surrounding wall of the stope to guide the cutting and finding work, and if necessary, the gamma measurement of the blasting is performed. The calculation of ore, ore grade, and loss depletion is based on the geophysical follow-up sampling data.
Third, drilling and blasthole gamma measurement
The gamma hole can be used instead of the core sample, the ore body is delineated, and the thickness and grade are determined. Therefore, uranium mines should use drilling instead of pit exploration to explore branching ore bodies and blind ore bodies. The drilling depth can reach 100m, generally 3~20m. The γ measurement is also required for the shallow hole of the working face and the blasthole of the surrounding wall. In order to ensure the quality of the hole measurement, the ore powder in the hole must be flushed before the hole is measured.
Drilling and blasthole measurement spacing, mineralized section 10 ~ 20cm, maximum 40cm, non-mineral section 0.5 ~ 1m.
Fourth, gamma sampling catalogue main instrument
The main instruments for gamma sampling cataloging are listed in Table 1.
Table 1 γ sampling catalog main instrument
equipment name
Model
Measurement
Use
Production plant
Scintillation mine radiometer
Gamma directional radiometer
Portable logging tool
Radiometer
FD-122G 1
FD-42
FL-61K
KF-604
0 to 10000 γ
0～40000γ
0～100000γ
0.01% to 5.00%
γ sampling cataloging and measuring holes
γ sampling catalog
γ logging (deep hole)
γ sampling cataloging hole (50m)
State-owned 261 factory
Shanghai Electronic Instrument Factory
Shanghai Electronic Instrument Factory
Sixth Institute of Nuclear Industry
The instrument in the table measures the ore uranium content indirectly according to the measured ore gamma intensity. At present, foreign countries are testing the method of directly measuring the uranium content in the ore, such as the direct measurement of uranium by slow-release neutrons, and the soft-hard γ-ray intensity ratio method.
V. Rapid analysis of ore checkpoints
Generally speaking, each ore mine set up one or several checkpoints on the ore produced, metal implement measurement and quality supervision. Types of ore checkpoints There are mine car ore checkpoints, car ore checkpoints, train ore checkpoints, ropeway mine ore checkpoints, and tape ore checkpoints, depending on the location and transport ore container category.
The gamma intensity measuring instruments commonly used in ore checkpoints are shown in Table 2. In order to ensure the quality of the analysis, the installation position of the radiation meter, the conversion factor determination method and the instrument calibration method must be correctly selected. The instrument is calibrated once a quarter, and the whole vehicle or picking block is sampled for physical and chemical analysis for half a year to eliminate systematic errors.
Table 2 Main instruments of ore checkpoint
equipment name
Model
Measurement
Use
Production plant
Check station transistor radiometer
FXY-217G 1
0 to 5 × 10 4 H 2
Analyze mine and car ore grade
State-owned 261 factory
Uranium bismuth spectrum inspection station radiometer
FXY-221
Uranium 0.01% to 1.00%
é’0.03%~1.00%
Ibid.
Ibid.
Cableway inspection station radiometer
FXY-1901
0.01% to 1.00%
Analysis of the ore grade
Ibid.
Train ore grade analyzer
FXY-1904
0.03% to 0.5%
Analysis of train ore grade
Ibid.
Mine car inspection station radiometer
FXY-1905
0.01% to 1.00%
Analysis of ore grade
Ibid.