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
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).
|Throughput for samples with gold content > 0.5 ppm, samples / hour||70|
|Sample volume, mL||300|
|The sample particles sizes should be no more than, mm||3|
|Facility height together with crane for assembly of radiation shielding, m||4.1|
|Width (klystron modulator and chiller located separately), m||4|
|Maximum power consumption, kW||70|
|Electron energy range, MeV||7-9|
|Maximum electron beam power, kW||10|
|Radiation on the surface not more, mSv/h||1|
|Diameter of detectors of high-purity germanium spectrometers, mm||110|
|Energy resolution of spectrometers for energy 122 keV, eV||722-726|
|Energy resolution of spectrometers for energy 662 keV, eV||1337-1375|
|Quantity of spectrometers||2|
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 samples||ppm||Standard samples||ppm|
|MST 209||24.3||MST Gq157d||0.85|
|MST G173e||3||OREAS 682||0.074|
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.