Development of the portable equipment complex for control of subcriticality of neutron multiplying systems

Development of portable pulse neutron generators with a wide range of parameters (neutron yield – up to 10 pulse/sec, frequency of pulses follow– up to hundreds of hertz) and a corresponding recording equipment allow to realize a portable complex of the equipment for control of subcriticality of multiplying systems. Among such systems the storages of spent fuel, suppressed reactors, storages of radioactive waste and some other objects are of the greatest interest from the standpoint of the measuring control. Reliable measurement of large negative reactivities is the very important in the problem of safety control on the foregoing systems. During many years the pulsed neutron method was used for measurement of neutronphysical characteristics of reactors with different energy spectra of neutrons simulating on critical assemblies. As a neutrons source the pulse neutron generators (PNG), developed in All-Russian Research Institute of Automatics, were used. PNG’s operating experience on vacuum neutron tubes in research institutes, at industrial enterprises, in geological and geophysical parties has shown efficiency of their operation, reliability, simplicity of operation and safety. Features of physical processes in ionic sources of vacuum neutron tubes determine both merits and demerits of the given type. Merits of the generators are simplicity of their design, instant availability for operation, high neutrons yield in pulse, absence of neutron radiation between neutron pulses, high neutrons yield per unit of reserving energy. Demerits are rather low endurance and stability of neutron flux connected with features of the arc discharge and explosive character of desorption of working gas from a source electrode. Generators intended for solution of wide range of science and industry tasks – PNG-01, PNG-02, PNG-03, PNG-013 have been developed in All-Russian Research Institute of Automatics [1]. Feature of these base series of PNG consists in following: irradiators of neutrons of all generators are powered by the unified power and control unit. It allows the consumer to create with the minimal financial expenses a system of neutron sources with wide range of neutron characteristics. However there is a whole series of tasks demanding a concrete specialized development of PNG. For the task of creation of portable equipment complex for control of subcriticality of multiplying a number of components in available experimental samples of neutron generators is modernized. In particular, PNG-101 having the following characteristics: neutron flux – 10 n/s, neutron yield per pulse – 10 neutrons, duration of pulse less than 0.8 μsec, frequency of pulses – up to 100 Hz, resource on maximal frequency – 100 hours, sizes of the neutron source (PNG’s tube) – 34 mm in diameter, 1327 mm long.