Tests of the prototype of a setup for the detection of diamonds in kimberlite by tagged neutrons method that Diamant LLC. held on the territory of the Pomorsk geological factory of Severalmaz branch of ALROSA company in July-September 2015, are successfully completed.
Currently, commercial production of diamonds is reduced to repetitive operations of crushing and grinding of kimberlite. After each stage, the crushed ore is subjected to various methods of enrichment. For example, it is irradiated with X-rays and diamonds begin to luminesce, allowing to find them among the rest of the breed.
The main disadvantage of this process is that the crushing can be destroying or damaging most valuable large diamonds. The method of tagged neutrons allows to find diamonds in the kimberlite rock without destroying it. Today almost all of the technological processes in the diamond mining industry work with the diamonds uncover from the rock. This method allows you to find a diamond inside a piece of kimberlite ore, without its destruction.
The method consists in irradiating the inspection object by fast neutrons with an energy of 14 MeV. Such neutrons excite the core material is removed excitation emission of hard gamma rays. As a result, under the influence of fast neutron the object of inspection begins to emit gamma rays with energies of 1-10 MeV. This glow is individual for each element and because of this nature of the spectrum of gamma rays is possible to determine the elemental composition of the material, in particular, find diamond consisting of carbon in a piece of rock. An important advantage of the tagged neutrons method is that it is possible to determine the three-dimensional position of the hidden substance. That is, not only to say that in a piece of rock has a diamond, but also to determine, where it is located. This makes it possible to carry out the selection of kimberlite ore and identify pieces of rock containing diamonds before crushing stage.
For resolving the separate components of the unit for detection of diamonds and verifying that it is working in the field conditions, has been created and tested a prototype. The prototype installation was carried out with 1697 measurements of core material from the Karpinski and Arkhangelsk diamond pipes, and also with various background materials from the tailings and off-balance ore. At the same time carried out a large series of measurements with diamond simulants, which are placed in the ore of different sizes.
An important result of the test was the safe operation of neutron module systems in the field conditions. Neutron generator worked 218 hours without any significant problems. There were no problems with the functioning of the gamma detectors. Diamond detection algorithm has been tested on large statistics measurements with the simulators.
Here is the main characteristics of the installation:
- Minimum detectable mass of diamonds - 2 carat (6 mm)
- Ratio of ore to diamond size – 10:1
- Probability to find diamonds – 97 %
- Probability of false alarms – 7%
- Output of concentrate - 3%
The tests fully confirmed the abilities of the tagged neutrons method to detect diamonds in the kimberlite without its crushing and correctness of the chosen design solutions.
Picture1. Employees of Diamant Ltd. during tests of the prototype at the Pomorsk geological factory of Severalmaz (Archangelsk).
Picture2. A sample of kimberlite ore particle size of -150+ 100 mm with a diamond simulator inside.
Picture3. Diamonds founded in the concentrate.