Monte Carlo simulations and experimental results on neutron production in the uranium spallation target QUINTA irradiated with 660 MeV protons.

The activation experiment was performed using the accelerated beam of Phasotron accelerator at the Joint Institute for Nuclear Research (JINR). The natural uranium spallation target QUINTA was irradiated with protons with energy 660 MeV. Monte Carlo simulations of neutron production were performed using the Geant4 code. The number of leakage neutrons from the sections of the uranium target surrounded by the lead shielding and the number of leakage neutrons from lead were determined. The total number of fissions in the setup QUINTA was determined. Experimental values of reaction rates for the produced nuclei in the 127I sample were obtained and several values of reaction rates were compared with the results of simulations. Experimentally determined fluence of neutrons in energy interval 10-175 MeV using the (n,xn) reactions in the 127I(NaI) sample was compared with the results of simulations. Possibility of transmutation of the long-lived radionuclide 129I in the QUINTA setup was estimated.

On the possibility of detecting fissile nuclear materials using coincident gamma rays.

Almost every radiation monitor installed at the customs and border control points designed for detection of nuclear fissile materials uses gas neutron counters tracing decay neutrons. They have a low background level, but at the same time small efficiency. This work describes the nuclear fissile materials detection methodology based on the instantaneous gamma-radiation accompanying the decay. The tests results of designed and produced radiation monitors based on this principle to control pedestrian and vehicles are presented.

Identification of radioactive materials in moving objects.

Control over the transportation of the radioactive materials crossing the borders of Uzbekistan is actually today not like before, because of increased threat of terrorism and urges of terrorist organizations to use radioactive materials in their terrorist activities. There are many companies producing radiation control systems. All such systems existing nowadays are based on the principles of intensity comparison for radiation detected by the system in the absence of control object and the intensity of the radiation when object appears. This method works well only in the conditions of constant or weakly changing background. However, at significant deviation in the value of background the number of false alarms set off by the systems increases. The present work describes the method for radioactive materials detection in the moving objects independent of the significant background deviations and present radiation monitoring establishment based on this principle.

Efforts of Uzbekistan to prevent nuclear terrorism and smuggling of radioactive and nuclear materials.

Uzbekistan is located on the cross-roads from the north--Russia, Western Europe--to the south--Afghanistan, Iran, Iraq and others. The appearance of terrorist organizations urged some Asian countries to make the nuclear weapons, the making the task of stopping the transportation of nuclear materials and technologies from the north (from countries possessing nuclear weapon) to the south (to countries desiring to have weapons and its components) a reality. To resolve this problem, on the main transportation routes, "Yantar" stationary radiation monitors of Russian production were installed, and development and production of monitors of our own make was started. This paper covers these works as well as those on preventing possible terrorist attacks on nuclear objects of Uzbekistan.