Calculation of Temperature Conditions of a Plasma Sputtering Cell for Decontamination of Nuclear Power Plant Constructions

Abstract

We are developing a technology for the “dry” deactivation of nuclear power plant (NPP) constructions by ion sputtering of surfaces with microsized radioactive contaminants. Our technology is implemented by plasma discharge in an inert gas medium with mass transfer of sputtered material and its deposition in the diffusion mode on the anode substrate. In our technology, unlike traditional radiochemical methods, radionuclides do not transfer into liquid radioactive waste (LRW), but condense in a compact solid form, which makes it possible to use them. Since our technology can be applied both during decommissioning of NPPs (including deactivation of neutron-irradiated nuclear graphite) and during routine operation and scheduled repairs of nuclear reactors, it is possible to extract the necessary isotope concentrate in the required quantities using an intense neutron flux in the NPP. The design of a plasma sputtering cell to remove radionuclides from the irradiated graphite and the NPP construction surfaces involves ignition of a direct current plasma discharge in an inert gas (for example, argon) at a pressure P ~ 0.1–1 atm and control of the temperature conditions of the sputtering material deposition. In this paper, the temperatures of the anode (tantalum collector) and the cathode (sputtered graphite) have been calculated depending on the input power to the argon plasma discharge. Data on the temperatures of the cathode and anode (collector) surfaces make it possible to control the elemental composition of the sputtered atoms and to form nanoscale layers of radionuclide concentrate on collector for use in radiation medicine and new betavoltaic batteries. Thus, the technology is important not only for the deactivation of NPPs but also for the formation of nanoscale layers of beta-active materials.