Possible use of the small ?Argus? reactor for activation analysis of samples from gold-bearing deposits

Autor: V. I. Drynkin, A. L. Kerzin, V. E. Khvostionov
Rok vydání: 1987
Předmět:
Zdroj: Soviet Atomic Energy. 62:218-220
ISSN: 1573-8205
0038-531X
DOI: 10.1007/bf01123489
Popis: Modern geochemical search and prospecting methods for gold-bearing deposits, as well as the joint treatment of raw-material resources, require mass determinations not only of gold and silver but also of other elements forming part of an ore body. The latter is important fvr a possible concurrent extraction of elements and for determining the geochemical relationships (ratio of the indicating elements, form of the correlations, etc.) which can improve the reliability of predictions of the mineralization of areas to be explored. Assays with a gold-detection threshold of 0.2 g/ton are preferred among the analytic techniques of determining gold and silver in representative samples (20-100 g) [i]. In the last few years, accelerators [2] and isotope sources with a neutron yield up to i0 *~ sec-* [3, 4] have been employed in prospecting work, grading of samples, and for checking processing work. The irradiation technique makes it possible to determine gold and silver in representative samples with detection limits of 0.3 and 10-20 g/ton, respectively. In our opinion, the small-size "Argus" reactor with its power output of up to 50 kW (thermal neutron flux density of about 10 *2 cm-~.sec -*) offers new possibilities for developing nuclear-physics analysis techniques; the output exceeds the neutron fluxes of the aboveindicated neutron sources by several orders of magnitude [5]. Distinctive features of the reactor: guaranteed safety (the self-regulation of the chain reaction is important in this regard); possible placement of the reactor at the user proper without expensive health shielding media; simplicity and ease of operation; and relatively low cost. In order to assess the analytical possibilities of the Argus reactor, we used samples which has been picked from gold-bearing deposits and included practically all ore types (the collection was prepared byA. N. Shatsov, G.A. Milovskii, andA. R. Khrust); we also used RUS 1-4 and RZS 1-3 standard-composition samples of gold-containing ore. The samples had various matrices with large variations of the concentration of the elements; it was therefore possible to assess the real detection limits of gold and silver. The samples also contained dispersed elements and rare-earth elements which are important for establishing search criteria. We indicate below the concentration of the elements (% by mass) in the matrix of the geological samples: Na Cu Fe Zn As Sb n.10-2-- n.t0-3-- n.0.2-- n.t0-3-- n.lO-2-- n,t0-z11,0 24,0 49.0 52.0 52.0 0.6 Samples with a weight of 1.5-20 g were placed into polyethylene capsules. The irradiation time varied between 0.5 and 5 h (l.5-g sample was used only for analyzing standardcomposition samples). The samples were irradiated in reactor channels having various spectral parameters of the thermal and epithermal neuron fields. The cadmium ratios R of the gold were (l-mm-thick cadmium was employed): Channel TsEK EK-I EK-2 EK-3 EK-5 R 1.59 2.54 2.14 3.13 2.56 The relatively low cadmium ratios (ranging from 1.59 to 3.13) point to good chances of reducing the background radiation resulting from the elements in the matrix (except for Sb and As) and a number of impurities (Sc, Cr, Na, and K) near the analytic peak and of substantially reducing (by a factor of ten) the total activity of the samples almost without any loss in sensitivity.
Databáze: OpenAIRE
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