Year
2003
Abstract
The paper describes the final phase of the ISTC Project ? 596, and presents the latest results of the development and application of digital technology in devices of fissile material (FM) detection and control with pulsed neutron sources. To digitize the scintillation signals, a system with four independent channels and with a step of digitization equal to 10 ns was applied. A model of the graphite-moderated customs device for the FM detection was designed. It was a parallelepiped with external dimensions of 1300x1300x1200 mm, inside of which there was a cavity sized 500×500×1200 mm. Inside the cavity, there was a stilbene scintillator of ?40×40 mm, and samples of FM. The neutron generator of DT reaction had a yield at a level of 108 n/s, and was placed outside of the device. The samples were 2%-enriched cylindrical uranium blocks with total 235U mass of 165 grams. The performed complex of experiments has shown that such a device is capable of separating neutrons and photons in (10-150) µs after a source neutron pulse, and allows obtaining various time functions of fission neutrons and photons in cases, when the uranium is surrounded with cadmium covering, and without it. The digital technology of scintillation signal processing was also used in a model of customs device operating by the principle of registration of FM fission neutron coincidences. The model consisted of four plastic scintillators sized 500×500×50 mm each. The scintillators were assembled in a tetragonal structure, inside of which there was a hydrogen-containing neutron moderator, lead shields, FM samples and a pulsed DD neutron source. Calibration experiments performed with FM samples of different weight have shown that the sensitivity of the device is at a level of (5-8) grams of 235U for the analysis time of 5 s, and the yield of a pulsed DD neutron source at a level of 106 n/s.