Study of evaporating the irradiated graphite in equilibrium
low-temperature plasma
E.V. Bespala1, I.Yu. Novoselov2, A.O. Pavlyuk1, and S.G. Kotlyarevskiy1
1Pilot and Demonstration Center for Decommissioning of Uranium-Graphite Nuclear Reactors, Seversk, Russia
2Tomsk Polytechnic University, Tomsk, Russia
E-mail: bespala_evgeny@mail.ru
Keywords: irradiated graphite, plasma, processing, decontamination
Abstract
The paper describes a problem of accumulation of irradiated graphite due to operation of uranium-graphite nuclear reactors. The main noncarbon contaminants that contribute to the overall activity of graphite elements are iso-topes 137Cs, 60Co, 90Sr, 36Cl, and 3H. A method was developed for processing of irradiated graphite ensuring the volumetric decontamination of samples. The calculation results are presented for equilibrium composition of plasma-chemical reactions in systems “irradiated graphite-argon” and “irradiated graphite-helium” for a wide range of temperatures. The paper describes a developed mathematical model for the process of purification of a porous graphite surface treated by equilibrium low-temperature plasma. The simulation results are presented for the rate of sublimation of radioactive contaminants as a function of plasma temperature and plasma flow velocity when different plasma-forming gases are used. The extraction coefficient for the contaminant 137Cs from the outer side of
graphite pores was calculated. The calculations demonstrated the advantages of
using a lighter plasma forming gas, i.e., helium.
DOI: 10.1134/S0869864318010109
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