Bieńkowska, BarbaraDrozdowicz, KrzysztofGabańska, BarbaraIgielski, AndrzejJanik, WładysławKurowski, ArkadiuszTracz, GrzegorzWiącek, UrszulaDankowski, Jan2018-01-112018-01-112014http://rifj.ifj.edu.pl/handle/item/100A technical design of the device for detection of delayed neutrons emitted from neutron-activated fissionable material samples has been performed according to physical assumptions which were earlier elaborated. The DET-12 device was constructed. The detection system was composed, consisting of twelve 3He neutron detectors, related electronics lines, and the data acquisition and recording system. The detectors were adjusted to work in groups by three connected to one preamplifier, considering a weak intensity of emission of the delayed neutrons. Laboratory measurement tests of the device operation were made with use of an isotopic neutron source. A total efficiency of neutron detection in DET-12 was experimentally determined and a relative benchmark calculation was made by means of a Monte Carlo modelling of the neutron transport in the device from the source to detectors.engReport