Tests in Mirny
Currently, the "Diamond" LLC is developing a prototype of neutron separator operating according to the method of tagged neutrons (TN). This method allows to determine the presence of diamonds in kimberlite rocks without destroying it. It involves the irradiation of diamonds and kimberlite by fast neutrons with an energy of 14 MeV. It is very important to show that irradiation by fast neutrons does not change the properties of the diamond, and does not induce significant induced radiation activity in the irradiated ore.
To do this, the tests were carried out in Mirny on irradiation of diamonds and geological kerns by fast neutrons. For measurements in Mirny portable TN detector DVIN-1 was taken, which served as a source of neutrons with an energy of 14 MeV.
The tests were performed under the contract with ALROSA company, which provides for the tests a collection of 90 diamonds from Mir, Udachnaya and Aikhal mines(see. Figure 1).
Fig.1 Diamonds from Mir mine delivered for the tests.
In the neutron separator the kimberlite ore is loaded into the trays, each of which is irradiated not more than 4 seconds with fast neutron flux with intensity of (5-10) 107 s-1 . At the tests the time of diamonds irradiation ranged from 4 sec to 32 min.
After irradiation, the diamonds will be analysed in the Research Geological Exploration Company "ALROSA" and detailed study of the characteristics of crystals will be obtained. Apart from visual inspection of crystals (shape, transparency, stain, safety, fracturing of crystals, the presence of impurities), to be held in the diamond-IR spectroscopy, photoluminescence spectroscopy at liquid nitrogen temperature in the range 325-740 nm, and the absorption spectra were measured in a visible region range 375-750 nm.
An important result of the tests was the documentation of the lack of induced radiation activity which excess the natural background in diamonds, kimberlite ore and the surrounding area.
The measurements of the spectra of different geological kerns were also carried out to develop methods for determining the elemental composition of the samples using the method of tagged neutrons (see. Figure 2).
Fig. 2 Irradiation of geological core sample by tagged neutrons beams.