Liquid-metal lead-bismuth target for high-energy protons as an intense source of neutrons in accelerator-controlled systems

Abstract

Great interest has been observed in recent years in the accelerator-controlled (electronuclear) systems, where an intense source of neutrons, which consists of a target generating neutrons under the action of accelerated ions (usually protons), is placed in a neutron multiplying or/and moderating blanket.Development and substantiation work is being conducted with different intensities on such systems for three purposes. 1. Production of Energy Using the Uranium-Thorimn Cycle [1]. The blanket is a suberitical thermal or fast reactor with solid fuel. Reactivity accidents are ruled out on account of the suberiticality, and the use of uranium-thorium cycle greatly decreases the production of highly toxic actinides and plutonium, a potentially dangerous element from the standpoint of solving the problems of nonproliferation of nuclear weapons.2. Transmutation of Long-Lived Actinides and Plutonium Utilization. It is in this field that the supporters of suberitical electronuclear systems strive to prove their advantages over fission reactors. These arguments can be systematized approximately as follows.a) The large amount of accumulated plutonium, both reactor plutonium and weapons plutonium from disassembled nuclear warheads, make urgent the problem of utilizing it from the standpoint of nonproliferation of nuclear weapons and protection of the environment, since plutonium is a highly radiotoxic element. Weapons plutonium can be used as fuel in fast reactors, but on account of the presence of 238U any reactor produces plutonium.The subcriticality of an electronuclear system makes it possible to vary the composition of the nuclear fuel in the blanket over wide limits, and the system can operate on pure plutonium fuel.Some scientists, especially American scientists, believe that in the future nuclear power should operate with the minimum possible amount of plutonium, and subcritical setups have a niche in such a system. b) Transmuted actinides and fission products can be continuously introduced into and extracted from a subcritical system with liquid plutonium fuel, and a continuous chemical reprocessing can be organized at the same time. The total radiotoxicity of the fission products and actinides which are loaded into and produced in such a system can, in the opinion of specialists, decrease much more rapidly than in fast burnup reactors and therefore such a system is more efficient. c) For proton energies -1.5 GeV up to 50 secondary neutrons per proton are formed in a target consisting of a material with a high atomic number (lead, bismuth, and others), i.e., approximately 30 MeV of energy is released per neutron. At the same time, in the case of the fission of nuclear fuel about 80 MeV are released (-2.5 neutrons per fission event with energy release -200 MeV). This fact in principle makes it possil~le to achieve in the blanket of an electronuclear setup a higher neutron flux density than in a reactor, since the extraction of heat increases with the flux. In turn, higher fluxes make it possible to increase the trans...

The Chemical Kinetics of Alkaline Extraction of Tellurium from Lead-Bismuth Eutectic

“…8) Each tellurium concentration data point was converted into the form shown in Eqs. (4) and (6). This data was then plotted and a least squares fit performed to determine a first and second order reaction rate constant for each operating temperature.…”

“…A key characteristic of polonium is that, when mixed with lead or bismuth, it forms relatively stable intermetallic compounds, i.e., PbPo with lead and Bi 2 Po 3 with bismuth. 3,4) Moreover, if both lead and bismuth are present, it preferen-ORIGINAL PAPER tially forms PbPo. 2) Similarly, tellurium forms two intermetallic compounds with lead and bismuth (i.e., PbTe and Bi 2 Te 3 ), of which the lead-based compound is more stable than the bismuth-based compound, i.e., ÁG f PbTe¼À75 kJÁmol À1 Te vs. ÁG f Bi 2 Te 3 ¼À26 kJÁmol À1 Te.…”

The Chemical Kinetics of Alkaline Extraction of Tellurium from Lead-Bismuth Eutectic

“…3,4) Moreover, if both lead and bismuth are present, it preferen-ORIGINAL PAPER tially forms PbPo. 3,4) Moreover, if both lead and bismuth are present, it preferen-ORIGINAL PAPER tially forms PbPo.…”