Кафедра "Прикладная Ядерная Физика"
Национальный исследовательский ядерный университет "МИФИ"

Научные исследования

Научные исследования

Characteristics of detectors for prevention of nuclear radiation terrorism

Shevchenko P.N.*, Dudin I.V.*, Zapary P.V. *, Samosadny V.T., Ryabeva E.V.
National Research Nuclear University NRNU MEPhI

There is consideration of types of detecting systems in use for the task of nuclear terrorism cases prevention to disclose and identify the a dangerous source and to find the correct direction to the radioactive source.

The fist type of system to determine geometrical structure of radiation field is modular detector with anisotropic sensitivity. The principle of work of a modular detecting device is the simultaneous operation of several detecting modules with anisotropic sensitivity to gamma radiation. Basic error for detection of direction to the gamma rays sources (for 137Cs) not more than 10 is reached for four (NaI(Tl) module system.

For the detection of neutron radiation sources and analyzes their spectra using a multilayer neutron detector based on layers of helium-3 counters and polystyrene. The design of such a detector is optimized so that it has the highest efficiency for 252Cf fission neutrons detection and for a softer spectrum of the fissile material, placed in a simple protective case made of steel with a thickness of 0.5 cm and 4 cm thick polyethylene.

Finding the directions to the gamma radiation source


A-Layout of 4-modular detecting system with cylindrical scintillations (green) and shield (yellow)


B-The dependence of the ratio of the number of photons detected by one module to the total number of photons detected by all modules together (relative count rate) on the angle - the direction of the source of γ-radiation. The numbers on the curves indicate the numbers of the module


C-Mobile complex for finding direction and remote disclose of gamma sources

Basic error for detection of direction to the gamma rays sources (for 137Cs) not more than 1° is reached for four (NaI(Tl)) module system Collimation to the 2π steradian (half –space); Energy range for registered radiation from 0.1 MeV to 2.5 MeV; The car velocity -60 km/hour; Distance between the source and the car-200 m.

Disclose of neutron sources


D-Multi- layer neutron detector layout. 1 – steel frame; 2 –protecting layer from borated polystyrene, 3 – electronics; 4 –layer from helium-s counters; 5 –moderating layers from polystyrene


F-Dependence of minimum of fission material mass on measuring time For several distances between the source and detecting system