Kinetic Theory Analysis of Radionuclide Behavior in the Vacuum-Cesium System of a Thermionic Converter Reactor
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KINETIC THEORY ANALYSIS OF RADIONUCLIDE BEHAVIOR IN THE VACUUM-CESIUM SYSTEM OF A THERMIONIC CONVERTER REACTOR V. V. Abannikov,1 Yu. Yu. Kloss,2,3 O. K. Shaikhatarov,2,3 O. I. Dodulad,2,3 D. V. Shcherbakov,2,3 and D. Yu. Lyubimov2,4
UDC 533.72
The behavior of radionuclides (Kr and Xe) and process gases (CO) in the vacuum-cesium channel of a thermionic converter reactor is modeled by solving Boltzmann’s equation numerically. Modeling techniques and a software system were developed in the course of this work. Series of calculations were performed for the variation of the initial flux of radionuclides, the dependence of the radionuclide flux at the egress on the flux at the ingress was obtained, the dependence of the carbon monoxide pressure in the opening of the connecting channel on the size of the opening was obtained, and the overgrowth time of the opening due to the condensation of cesium carbonate was estimated.
One of the most promising trends in modern physics is the development of space apparatus capable of developing high power output for, as an example, round-the-clock observation of technogenic and natural processes in different regions on Earth. Their requisite power cannot be attained by means of conventional solar power systems, so that the development of nuclear plants is called for. Thermionic converter reactors on thermal and intermediate neutrons have been developed in project design work on space nuclear power plants [1]. One element of such a reactor is the electricity generating channel (EGC) containing a ventilated fuel pin with nuclear fuel based on uranium dioxide. The normal operation of multielement EGC with oxide nuclear fuel with communicating cavities of the fuel pin and an interelectrode gap as well as, in particular, changes in the output electrical characteristics are affected by numerous factors, for example, the presence of fission products, which are formed in the fuel during reactor operation, in the gap [2]. The metallic products of fission and their oxides enter the interelectrode gap, diffusing through a trap and the gas removing system, and become concentrated on the walls. The gaseous fission products, for example, krypton and xenon, do not condense in the trap and the gas removing system, ingress into the gap and then into the vacuum-cesium system [3]. The products of β-decay of krypton and xenon can affect the electric power output of the EGC because of adsorption on the surface of a collector [4]. Testing in a loop channel is conducted in order to validate the serviceability and optimize the EGC. Using a gamma-spectrometric system placed in the vacuum pipeline of the pump-out line, the radionuclides are recorded and the volumetric activity of the pumped-out gases is measured [5]. A problematic task in this case is to determine the pressure and flux of the gaseous fission products in the generator of the working-body vapor (cesium), because it is difficult to determine the yield of radioactive gases from the fuel and the results do not permit determining with adequate acc
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