V. S. Barashenkov

Neutron yield in high-energy deuteron-nuclear reactions

The authors have calculated the neutron yield and the heat released in a large, practically infinite uranium target under bombardment by 1-2-GeV deuterons by the Monte Carlo method. The authors attempt to refine the data presented in previous studies by using a more accurate technique for calculating the interaction of the flux of fast particles with matter and by describing more accurately the interaction of the hadrons and the deuterons with the nuclei. They find that deuteron bombardment produces only 10% more neutrons than proton bombardment.

Peculiarities of the energy loss spectrum of high energy particles penetrating thin silicon plates

Energy losses in thin plates of silicon for protons, 12C ions and mixtures of nuclei from helium to oxygen with energy 3.65 GeV/nucleon, have been measured. The spectrum of the released energy shows a kink in the region of E = 5 MeV and is described by a sum of two exponentials. The slope of the more slowly decreasing exponential, which is the more important for estimation of radiation induced errors in semiconductor devices, shows a very weak dependence on the type of bombarding particles. Mathematical simulation of internuclear cascades confirms the experimental conclusions.

γ-background induced in structural materials of spacecrafts

Abstract Features of the γ-radiation of the induced activity in structural materials Al, Ti, Fe, Cu, W, Pb and in one of the alloys exposed to cosmic proton and albedo neutron fluxes in close-to-earth orbits are investigated by using a Monte Carlo simulation of internuclear cascade development. Disc-shaped targets of 100 cm in diameter and different thicknesses have been considered. The influence of the South Atlantic Anomaly is considered. The spectral distribution of the γ-background intensity is analysed for flight durations from 24 hours to several years. It is shown that the induced radioactivity is comparable to the orbital background γ-radiation and in some energy ranges even exceeds it.

Neutron yield in fissile targets irradiated with high-energy protons

The construction of meson factories and of other high-energy particle accelerators of high currents has made it possible to build extremely intense (~101s-1018 sec -I) sources of neutrons which are generated by multiplication of currents of particles produced in highenergy splitting reactions [1-3] in fissile targets. These sources can be used in nuclear physics experiments, materials science research, and other applications [2, 4]. Some laboratories have made experimental measurements of the neutron fluxes and the liberation of heat in various blocks at neutron energies of up to 1.5 GeV; for example [5, 6], the results agree with the theoretical calculations of [3, 7-10]. But these experiments were made at low intensities of the beams of the generating protons when a coolant, reducing the heating, and structure elements which can substantially reduce the intensity of the neutron beam need not be introduced into the target. The neutron flux is also reduced when oxides or carbides are used in the fuel elements of the targets.

Characteristics of electronuclear targets containing water

ConclusionsThe replacement of liquid-metal lead or sodium coolant with water has virtually no effect on the intensity of the neutron flux in the blanket of an electronuclear installation and the formation of239Pu nuclei. The accumulation of239Pu nuclei is accompanied by a rapid growth of the heat release in the target and a decrease of the production rate. On account of the block effect, the heterogeneity of the target results in an appreciable increase of the neutron flux and breeding. At the same time, when a hydrogen-containing target is used, the heat release increases considerably.Taking into account the chemical bond in the water molecules and the energy dependence of the neutron cross sections in the thermal region has virtually no effect on the characteristics of an electronuclear installation, and they can be neglected in calculations.

Electronuclear breeding of nuclear fuel in thorium targets

ConclusionsElectronuclear breeding of fuel in thorium and uranium targets differs mainly in that in the case of thorium the neutron flux and the production of the easily fissioning isotope decrease by approximately one third, the total heat release decreases by more than a factor of 2, and at the same time the temperature gradients at the center of the target increase. As we have already mentioned above, if distance within the target is expressed in the units of g/cm2, then the spatial distribution of different quantities is found to be close in the uranium and thorium targets.

Time dependence of the characteristics of an electronuclear generating system (“runaway effect”)

The objective of this study was to construct a time-dependent breeder reactor model using the Monte Carlo method. This was necessary previous calculations using a constant target composition resulted in a rapid flux increase (runaway effect) and the transfer from a plutonium production reactor to a uranium 238 burning reactor. In this study, the runaway effect was considered using a natural uranium target, and the equation describing the change in the concentration of easily fissionable nuclei was solved and evaluated for t = 0 to t = 12 months. Maximum plutonium production was found to occur between three and six months, after which the rate of accumulation slowed due to a sharp increase in the plutonium fission rate. With the increase in plutonium fission, there was also a substantial increase in neutron leakage from the target and heat production in the target.