An experiment measuring the temperature to which small samples of W, Ta, Mo, Cu, Zr, Ni, Fe, Ti, Sn, and Pb are heated by IGRIK radiation is performed. The technology for placing the thermocouples is described, the results of an analysis of the elemental composition of the samples are presented, and the experimental results from measurements of the heating temperature are also presented. The PRIZMA.D and MCNP computer codes are used to calculate the neutron and γ-ray energy losses in samples irradiated by a reactor pulse. The heat-up temperature is calculated. Discrepancies in calculations performed of the neutron and γ-ray energy losses in samples of the materials using different nuclear data libraries are shown. It is shown that the heating temperature calculated on the basis of the calculation of the neutron and γ-ray energy losses in the material of the samples, using the PRIZMA.D program with the BAS nuclear data library, agrees with the experimental value to within 5%. The agreement obtained with the MCNP code using the ENDF-B5 and -B6 libraries is no worse than 10-15%.Computational and experimental studies of the radiation-induced heating of structural materials have been conducted in the last few years [1, 2]. Three-dimensional cooputer programs, for example, the domestic program PRIZMA.D with the BAS nuclear data library [3,4] and the American program MCNP [5] with the ENDF-B5 and -B6 libraries, are available for performing computational studies. They have been verified on many physical characteristics of different pulsed reactors but not on the effects due to radation-induced heating. The nuclear data describing the mechanisms of neutron and γ-ray energy losses need to be verified. These are the processes that are the object of study in the present work. In the experiments, which were begun in 2000 on the IGR pulsed uranium-graphite thermal reactor, the heat-up temperature due to neutron and γ radiation was measured for the following materials: W, Ta, Mo, Cr, Cu, Zr, Ni, Fe, C, Ti, Al, Sn, Pb, and (CH 2 ) n . In 2003 the experiments were continued on the IGRIK solution pulsed fast reactor [6]. The results of a computational and experimental study of the radiation-induced heating of Pb, Ta, W, Sn, Mo, Zr, Cu, Ni, Fe, and Ti samples are presented in the present paper.
The results of investigations of the operation of the IGRIK pulsed homogeneous solution research complex in the unconventional (for pulsed reactors) two-pulse mode with successive reactivity increments with generation of prompt-or delayed-neutron pulses are presented. Experimental data which give an idea of the processes occurring in the reactor core in the two-pulse regime are obtained. These data made it possible to determine whether or not the IGRIK reactor can be operated in this regime and the limitations imposed by the physical processes and special design characteristics of the system. It is shown that are pulses can be generated in several different ways. The dependences of the fission-pulse characteristics in a given regime on the initial conditions and the methods for obtaining the pulses are investigated. Methods are proposed for increasing the operational possibilities of the reactor.Over more than 30 years of operation, the IGRIK reactor has proven itself to be a powerful pulsed source of neutron and γ radiation, making it possible to vary the fission-pulse parameters over a wide range [1,2]. The pulsed regime has been perfected and does not differ in any fundamental way from the operating regime of other research reactors in this class. A rapid increase of reactivity is achieved by using four rods with independent pneumatic drives. In the ordinary pulsed regime, all rods are moved synchronously, which gives a pulse with the nominal parameters. To obtain a regime with paired pulses, each rod can be moved independently using a programmed facility -a block of temporal commands, which ensures that the rods are removed from and inserted into the core according to a prescribed program in an interval from 0 to 99 sec. The shortest interval between commands is 0.1 sec.The radiation characteristics of the IGRIK reactor (the neutron fluence in the experimental channel is ~1.5·10 15 cm -2 , the γ-ray dose is ~1.4·10 6 rad, the radiation acts for 2 to 20 msec) which are realizable in this regime make it possible to solve diverse research problems. However, there remain problems that can be solved only by perfecting regimes which are unconventional for a pulsed reactor:• a two-pulse regime where two successive fission pulses with duration from 4 to 10 msec and separated by 0.7 to 10 sec are generated; • a two-pulse regime with one pulse generated by delayed neutrons, which is characterized by action time from 0.1 to several seconds and a relatively low yield of neutron and γ radiation. Recording the Pulse Parameters. The time dependence of the energy release, the form of this dependence, the ratio of the integrals in the first and second pulses, and the time interval between the pulses were determined in this work. The problem in this case is complicated by the large difference between the pulse parameters -up to several orders of magnitude in amplitude and up to a factor of a thousand in duration. For example, the duration of the quasipulse which develops as a result of supercriticality on delayed neutrons is a...
The operation of the IGRIK pulsed homogeneous solution research complex in a multipulse regime followed by a reactivity increase is examined. The experimental data give an idea of the processes occurring in the reactor core when the multipulse regime is implemented. These data showed that the IGRIK reactor can be operated in this regime, and they made it possible to determine the range of the pulse parameters and the limitations which the physical processes and the special design features of the system impose. It is shown that there are several possible variants for the generation of a series of successive pulses. The dependences of the fission-pulse characteristics in this regime on the initial conditions and the pulse implementation methods are investigated.The IGRIK pulsed reactor, which is a solution reactor, was put into operation in1976 [1,2]. The core of the reactor consists of a solution of uranyl sulfate in light water. A feed pump dispenses the solution from a storage tank into the core vessel immediately before a pulse is obtained. IGRIK operates in three basic operating regimes -pulsed, quasipulsed, and static.The pulsed regime is obtained by fission of uranium nuclei by prompt neutrons with four pulse rods extracted from the core at the same time. The total reactivity excess of the rods is 6β eff . The initial level of the fuel solution in the core vessel is changed to obtain the required energy release. The energy released over a single pulse is 5-60 MJ. The pulse width at half-height ranges from 2 to 20 msec.The quasipulse regime is a modification of the pulse regime where the pulse is due to delayed neutrons. The reactivity which is introduced varies in the range (0.5-1.2)β eff above the critical state on delayed neutrons. When the system is transferred above the prompt criticality state, a wide fission pulse on prompt neutrons actually obtains in the range (0.07-0.2)β eff and the "tail" of this pulse, which is formed by the delayed neutrons, contains up to 50% of the total energy released. The pulse duration in this regime varies from 0.02 sec to several tens of seconds.The reactor can operate in the static regime at power levels up to 30 kW for along time (several hours). The prescribed power is reached by adding the required amount of the fuel solution into the core vessel. A decrease of the power is compensated by periodically adding fuel solution from the storage tank.The reactor is used mainly to obtain single fission pulses. Each successive pulse is generated, as a rule, several hours after the preceding pulse. However, a series of successive pulsed separated by a short time interval is needed for some experiments in nuclear physics. The present article examines variants of successive extraction of all four rods one at a time from the core in order to obtain four or more fission pulses. When pulses are produced in this manner, ordinary pulses and quasipulses can be obtained. Consequently, for this operating regime it is especially important to take account of the factors influencing the rea...
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