Using extracted electron beam from the 30 MeV microtron of IPP a thermal neutron source was built for activation analysis. Combined (Ta–Pb)-target is used as a gamma-neutron converter, and high-pressure polyethylene is used as a moderator. For the purpose of activation analysis special channels of different sizes were made in the moderator, with, in particular, a large pocket of about 103 cm3 in volume for irradiation of extended objects. Detailed spatial neutron flux distribution was measured, and the neutron flux density is of the order ofn·109 n·cm–2·s–1. The set up was used for detemination of Sb, As, V, Cr, Mn, Ni, Ga, Br, Re, Cd, REE content in oil, fuel oil, petrol, gaseous condensate under normal conditions. The sensitivity of noble elements determination in non-destructed loaded boards approaches 1 mg of total mass in the assembly, and equals 0.05 ppm for Au detemination in rocks and minerals.