Plasma Scraping of 14 C Surface Nanolayer Formed by Neutron Fluence of Graphite Reactor
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lasma Scraping of 14C Surface Nanolayer Formed by Neutron Fluence of Graphite Reactor A. Petrovskayaa, *, A. Kladkovb, S. Surovb, and A. Tsyganova aPlasma
Application Department, Spectrum-Micro, St. Petersburg, 191036 Russia bScience and Innovation, ROSATOM, Moscow, 115035 Russia *e-mail: [email protected]
Received July 22, 2019; revised August 27, 2019; accepted September 20, 2019
Abstract—In this article, we consider some mechanisms of the formation of a nanometer-thick surface layer enriched with 14C isotope. Main channel of 14C surface accumulation is believed to be the neutron capture reaction with 14N atoms of the cooling gas mixture during operation of uranium-graphite reactors, in particular, a high-power channel-type reactor (RBMK-type reactor). For the “dry” collection of thin layers enriched in 14C isotope from the irradiated graphite surface of graphite-type nuclear reactor and further compact burial, we propose argon plasma discharge technology based on the special type of a microdischarge at a high pressure, up to atmospheric pressure. In addition, there are some important technical applications, such as brachytherapy medicine or new beta-voltaic batteries, which require the deposition of thin layers of betaactive isotopes (e.g. 14C) with nanoscale precision to form a controlled output energy spectrum of secondary electrons. The proposed technological scheme can potentially be used both for graphite deactivation in the irradiated reactor during decommissioning of uranium-graphite reactors, and at the same time for fabrication of highly concentrated 14C nanosized coatings for use in radionuclide medicine and beta-voltaic batteries. Keywords: irradiated reactor graphite, neutron flux, 14C isotope extraction, plasma ion sputtering, nanosized beta-active coatings DOI: 10.1134/S1027451020070393
INTRODUCTION Currently, the volume of the irradiated reactor graphite in the world is 100 thousand tons; this circumstance raises the question of the finding effective ways to deactivate irradiated graphite. Recent scientific studies [1–4] of the 14C activity distribution inside of graphite samples/bulks (14C is one of the most doseforming and ecologically dangerous isotopes in the irradiated graphite stack) have shown that a significant concentration of 14C isotope is localized on of the graphite bulk surface. Methods such as scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, Auger and energy dispersive X-ray analysis spectroscopy have been used to investigate graphite surface before and after neutron irradiation [1, 2]. The non-homogeneous distribution of 14C isotope was considered to be due to the neutron capture reaction with 14N and 17O atoms, which are presented as impurities in the manufactured graphite bulks, as well as in the graphite pile cooling nitrogen-helium gas mixture. Another interesting question concerns possible exploration of isotopes from the irradiated nuclear energy equipment and their useful application in dif
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