OPTIMIZING THE VALUE OF THE MASS OF SAMPLES AND THE TIME OF THEIR IRRADIATION IN INSTRUMENTAL NEUTRON-ACTIVATION ANALYSIS OF GEOLOGICAL SAMPLES

The conditions for optimizing the instrumental neutron-activation analysis (INAA) of natural samples with the use of thermal and epithermal (that is, passed through a cadmium filter) neutrons of a reactor were considered. A combined procedure of INAA was proposed, which comprises (1) analysis with thermal neutrons and the estimation of the level of the maximum possible measurable activity of the main nuclides with a high cross section of (n, gamma) reactions, and (2) subsequent analysis with epithermal neutrons with the use of the optimum values of the mass of samples calculated preliminarily (by the equation proposed) and other optimum parameters of the experiment (the integral flux of neutrons, time of cooling, etc.). The procedure developed provides a way of increasing the number of determined elements, lowering their determination limits, and widening the range of analyzed samples.