CORAD Limited

Design, manufacture, installation and service of linear electron accelerators and facilities with these accelerators
Gamma-activation analysis of gold ores

Facility for Gamma-activation Analysis of Gold Ores "Au-Isomer"

Facility for gamma-activation analysis "Au-Isomer" Measurement results window 8 MeV, 10 kW Linac Container with ore
Facility for gamma-activation analysis "Au-Isomer"
Measurement results window
8 MeV, 10 kW Linac
Container with ore

The testing of our facility «Au – Isomer» for gamma – activation analysis is complete. We developed it together with Baltic Scientific Instruments (Riga, Latvia) for JSC «Gold Mining Company PAVLIK».

The operating principle of the facility is based on the excitation of a gold isomer with energy of 279 keV and a half-life of 7.5 seconds by bremsstrahlung radiation from a linear electron accelerator followed by its registration by high-purity germanium-based spectrometers. This is not a destructive method (an ore sample is not destroyed and can be measured multiple times).

Tech Specs

Throughput for samples with gold content > 0.5 ppm, samples / hour70
Sample volume, mL300
The sample particles sizes should be no more than, mm3
Facility height together with crane for assembly of radiation shielding, m4.1
Width (klystron modulator and chiller located separately), m4
Length, m7
Weight, t118
Maximum power consumption, kW70
Electron energy range, MeV7-9
Maximum electron beam power, kW10
Radiation on the surface not more, mSv/h1
Diameter of detectors of high-purity germanium spectrometers, mm110
Energy resolution of spectrometers for energy 122 keV, eV722-726
Energy resolution of spectrometers for energy 662 keV, eV1337-1375
Quantity of spectrometers2

The facility was tested using standard samples of FGBU "VIMS" made on the basis of ore from PAVLIK deposit, samples of LLC "NTC" Minstandart» made on the basis of quartz sand and a sample from OREAS (Australia):

Standard samplesppmStandard samplesppm
MST 20924.3MST Gq157d0.85
VIMS215GO8.44MST SG147f0.312
MST G172f8.4VIMS211GO0.16
MST G173e3OREAS 6820.074
VIMS214GO2.38MST SGBlank10<0.005

Measurements results of standard samples and limits of permissible error for the 3rd accuracy category acc. to OST 41-08-212-04

The results of 13 standard samples measurements were performed in 21 minutes because for samples less than 0.5 ppm we carried out measurements 2 – 4 times for a higher accuracy. Our control system automatically directs samples for repeated measurements in case of insufficient statistics results of a single measurement and then averages the results of several measurements. The results prove that the facility provides measurements of the gold content of III accuracy category according to OST 41-08-212-04.

The facility was calibrated using standard samples MST 203 with gold content of 24.3 ppm, VIMS212GO with gold content of 0.4 ppm, and MST SGBlank10 with gold content of less than 0.005 ppm. Electrons energy and the accelerator beam current are stabilized automatically at a given level with an accuracy of no worse than 2%. However, the measurement procedure includes calibration for the indicated three standard samples every 4 hours.

The «Au-Isomer» uses essentially the same sample containers movement pattern and irradiation scheme as in gamma – activation facilities in mine Muruntau (Uzbekistan) and JSC "Yangeologiya" (Batagay) launched in 1977 and 1986 respectively.

More than 40 years of operating experience has shown that the movement of sample containers with the use of gravity ensures reliable and smooth operation cycle of these facilities due to the simplicity of the design. The «Au-Isomer» height is only 230 cm due to the curvature of transport channels and installation of two fast shutters (Russian Patent №203146 dated 25.01.2021).

The radiation shielding of «Au-Isomer» consists of iron blocks with weight of no more than 2.4 tons. The crane used to assemble the radiation protection is a part of the facility. For service purposes 5 rear blocks are removed and the accelerator is rolled out of the radiation shielding. This procedure takes no more than 20 minutes. The «Au-Isomer» is mobile as it can be disassembled and moved to another place in 4 x 40 ft. containers.

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