Customs monitoring of nuclear

Abstract

The possibility of terrorist groups obtaining nuclear weapons can be prevented only by technical means. In this connection, the systems for primary fast detection and identification of nuclear materials during customs monitoring and additional monitoring of loads, vehicles, and baggage play a larger role.Nondestructive methods of monitoring and identifying materials are based on detecting the characteristic or induced radiation of nuclides and measuring the absorption of radiation from an external source. For nondestructive monitoring of fissile materials, only penetrating neutrons and γ rays are used. For example, in [1] nondestructive elemental analysis in search of explosives and fissile substances when monitoring customs loads is done using a pulsed source of neutrons based on a small linear deuteron accelerator at 3.5 MeV. In [2], it was proposed that a photoneutron source based on γ-ray bremsstrahlung from thick targets consisting of heavy water (1 kg) or beryllium (3.34 kg) and a compact betatron at 3-10 MeV be used for the same purposes. A good example of using the characteristic neutron radiation for a system of passive monitoring of fissioning materials in 200-and 400-liter containers with βand γ-emitting radioactive wastes is [3], where the possibility of detecting neutrons according to the (α, n) reaction and spontaneous fission (counters with 3 He) under conditions of a γ-ray field with dose rate up to 1 Sv/h, which makes it possible to detect 10 mg of plutonium, was confirmed.Modern systems for nondestructive monitoring of shipping containers and vehicles operate or are built on the basis of 3-15 MeV technological linear electron accelerators [4,5]. The possibilities of such inspection systems for monitoring nuclear materials can be greatly expanded by using the fact that of all the known stable and long-lived nuclides (>0.8 yr) only for fissioning and heavy isotopes is the photofission threshold less than 6 MeV but greater than 4-4.5 MeV. For all other nuclides, the threshold for photoneutron reactions is less than 6 MeV and equal to (in MeV): 2 H 2.23, 6 Li 5.67, 9 Be 1.67, 13