27.06.2013

Under order of ALROSA Company, Neutron Technologies conducted the research that demonstrated how the tagged-neutron method helped in finding diamonds in kimberlite.

The diamond recovery today comes to fragmentation and grinding of the blue earth to fine sand. After each stage the kimberlite ore is X-rayed, so that the diamonds glow and thus may be detected among the rest of the mineral.

The main drawback of this process is that the grinding may destroy valuable big diamonds of 5 carats and heavier.

Under order of ALROSA, Neutron Technologies developed the method to detect big diamonds in kimberlite without its destruction to complete disintegration.

The idea of the method is that the target object is exposed to fast neutron radiation of 14 MeV. Such neutrons excite the substance nuclei; the excitation is removed by hard gamma-quantum radiation. Eventually, the fast neutrons make the target object irradiate gamma-quanta of 1–10 MeV. This «glow» is specific for each element and it is the gamma-quantum specter that reveals the element composition of the material and, in particular, finds diamonds composed of carbon in the rock. The prominent advantage of the tagged-neutron method (TNM) is detection of 3D position of the target substance. Thus, the method both signals that a rock contains a big diamond and indicates where the diamond is. Therefore, the kimberlite ore may be sorted and the rocks containing big diamonds may be identified on the grinding stage.

The method of automatic diamond detection in the kimberlite ore was developed and the created prototype of the diamond detection unit measured the size of the detected diamond in various screening conditions. ALROSA provided 33 kimberlite samples of 50 kg in total for Neutron Technologies to exercise the method.

As the samples were being examined with tagged neutrons, one of them showed a considerable extra concentration of carbon.

When the samples were returned to the town of Mirniy, the unusual piece was analyzed. The sample showed two heterogeneous diamond inclusions of up to 7 mm diameter that consisted of small particles of 1–2 mm.

The pictures of the sample and diamond inclusions are given below.

TNM technology was developed by the scientists of the United Institute of Nuclear Research in Dubna. The technology served as a ground for various explosives/drugs detectors which batch production is being performed by Neutron Technologies, a project company of ROSNANO. The detector is based on the unique neutron generator produced by Dukhov All-Russia Research Institute of Automatics (Moscow). Now 77 TNM-based portable explosives detectors are used at the stations of Severo-Kavkazskaya and Oktyabrskaya Railroads, as well as at the subway stations in Moscow, Saint Petersburg, Kazan and Novosibirsk.

The acquired results open new opportunities in finding diamonds in kimberlite with TNM.