2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) | 2019
Estimation of the Irradiated Graphite Surface Nanolayer Thickness Enriched by 14С Isotope
Abstract
In the present paper we evaluate the thickness of the reactor graphite surface nanolayer enriched by 14C isotope formed during reactor operation. This graphite surface 14C enriched nanolayer is proposed to be removed using our new inert gas plasma decontamination technology. Surface decontamination of the nuclear power plant (NPP) constructions is provided by ion bombardment of the nano- and micro-sized radionuclides layer from the surface under treatment (cathode) and their diffusive transfer to collector plate (anode). There are many evidences that, e.g. 14C is predominantly located on the surface of irradiated reactor graphite instead of the inside of the graphite bulk. It is due to 14C main formation mechanism via effective neutron activation of the gaseous nitrogen, which is used as a coolant of the graphite piles. So, it is important to find N2 molecules concentration and subsurface depth penetration inside of graphite samples. In this way plasma sputtering technology can significantly reduce the irradiated reactor graphite activity at the decommissioning of uranium-graphite reactors. Additionally, this technology can be used to separate various atomic species sputtered from the graphite sample (together with their radioactive isotopes) by their sedimentation temperature and to form nanosized layer enriched with preferred radionuclides of controlled thickness. It provides to obtain new materials like a beta-active nano-micro-sandwich with adjusted output fast electrons energy spectrum. It can be used in the nuclear medicine field and for a new type of the betavoltaic batteries.