A LIQUID EUTECTIC JET AS A NEUTRON SOURCE FOR A SUBCRITICAL NUCLEAR REACTOR DRIVEN BY PROTON ACCELERATOR

摘要

Nowadays the specialists discuss the possibility to design a safe subcritical reactor driven by charged particle accelerator. The reactor power is regulated with neutron fluxes produced due to interaction of a particle beam with the suitable targets placed inside a reactor core. The problem the authors have to be solved is the elaboration of a neutron generator (analogue of a reactor control channel). A proton beam is injected into the channel and interacts with the jet liquid target. The vertical eutectic jet is directed up towards the beam. It allows to "stretch" the target giving more even distribution of neutron flux density along its length. The engineering solution of the proposed design will be more simple if the same eutectic is a coolant for the reactor core fuel assemblies. Gas-dynamic way (without any solid foil) is proposed for separation of accelerator vacuum from the jet target. Supersonic jet of inert gas is ejected from a circular nozzle in the vicinity of the accelerator beam outlet for this reason. Gas is then circulated via the circular collector to the nozzle forechamber. Lower surface of the collector simultaneously skims the droplets of the jet. Liquid target medium is pumped in the upward direction, reaches the skimmer and interacts with the particle beam. As a result the flow disintegrates; the liquid drops fall down to be collected In the bottom part of the channel containing the target medium. The proposed scheme has two loops: a gas loop for shutting of accelerator vacuum and an eutectic loop containing heat exchanger and filter. The using of the vertical liquid jet as the target medium eliminates the problem of local heat deposition because new and new portions of the eutectic interacts with the beam. The height of the nondisintegrate part of the jet depends on the jet total head and on the jet nozzle diameter. Eutectic alloy 55.5% Bi – 44.5% Pb is chosen as the target media. Available experimental data are used to calculate the value of the heat generation for the 1-GeV incident protons. The highest possible proton current value is determined to obtain the highest value of the local power strength equal to 3 MW/l. The temperature and thermal power strength distributions along the height of the fluid column are calculated for chosen parameters of the spallation neutron source. The neutron yield value is estimated using the "CASCADE" computer code. It is possible to distribute the proposed neutron sources if necessary inside a reactor core.