Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

The Concept of a Thermionic Reactor-Converter with Evaporative Heat Transfer

3/20/2021 2022 - #01 Physics and methods for direct conversion of nuclear energy

Alekseev P.A. Lazarenko G.E. Linnik V.A. Pyshko A.P.

DOI: https://doi.org/10.26583/npe.2022.1.10

UDC: 621.039.578:629.7

As a result of the analytical study of the designs of thermionic reactor-converters, four groups of technical solutions have been identified that differ in the method of heat transfer from the fuel to the emitters of the thermionic converter: one with direct in-core transfer (combining the fuel element cladding with the emitter) and three with thermionic converters taken away from the core, in which heat is removed either by heat pipes (common or individual for each fuel element) or is arranged according to the principle of a steam chamber.

The article discusses the advantages and disadvantages of each of these methods. It is shown that today the most developed design remains the version with in-core power conversion and, in the future, it will be based on a steam chamber, since it excludes the ingress of gaseous fission products into the interelectrode gap, as well as the effect of fuel swelling on the interelectrode gap size, and ensures the constancy of temperature and heat flux density on the surface of all the emitters of the thermionic converters, which makes it possible to choose the optimal operating point for them.

A model of a thermionic reactor-converter has been developed: it is equipped with a steam chamber containing a core and a zone of thermionic converters, in which the fuel element of the core and the power generating channels of the thermionic converter are spatially separated, covered with a capillary-porous structure and interconnected by a cellular capillary-porous spacer for returning the liquid metal coolant and passing its steam.

Neutronic calculations have shown the possibility of carrying out a reactor campaign lasting more than ten years, subject to nuclear safety rules, if a gadolinium oxide coating is applied to the surface of the fuel elements and the reactor vessel in the area of the core.

The evaluation of thermal and electrophysical characteristics show that, due to the constancy of temperature and heat flux density on the surface of all the emitters and optimization of the power conversion process for all the thermionic converters, it is possible expect a maximum efficiency of 20%.

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