Tritium Fuel Cycle Technology Readiness Assessment for the DEMO-FNS Reactor: Part 3

The tritium fuel cycle (FC) is one of the main systems of a fusion plant. Currently, active work is under way in Russia and worldwide to improve FC technologies in order to increase its efficiency and safety. Another area of work is demonstration and testing of technologies for large-scale systems of future fusion plants, which are characterized by large fuel flows and significant amounts of tritium in the systems. In order to plan work on the design and construction of fusion plants, it is necessary to analyze existing technologies and their readiness for use in FC. This article continues the analysis of the readiness of FC technologies of the DEMO-FNS facility in Russia started by the authors earlier. The Technology Readiness Level (TRL) methodology is used for the analysis, according to which technologies in the target application area correspond to different readiness levels from TRL 1 (basic principles observed and reported) to TRL 9 (actual system "flight proven" through successful mission operations). The article analyzes the technologies of tokamak pumping, tritium safety, and creation of materials for tritium handling. It is shown that in Russia vacuum technologies are poorly developed (TRL 2) and critically depend on the use of imported equipment. Methods for the analysis of tritium and its compounds, including technically complex ones, are actively used in Russia at various enterprises, but serial production of the necessary equipment exists for a small list of relatively simple methods, other methods are represented only by prototypes (often single samples), and the application of many analytical methods critically depends on the supply of foreign high-tech equipment. The technologies for creating multilevel protection and for capturing and processing of tritium waste are largely developed (TRL 6 and TRL 5), are applied in tritium laboratories and production facilities, and generally correspond to the world level. The level of readiness of materials for tritium handling (TRL 7) makes it possible to utilize existing technologies to produce equipment, components, and piping for FC systems outside the reactor vacuum vessel while operating at elevated temperatures. In the case of in-vessel components operating under severe neutron irradiation conditions, structural and functional materials should be appropriately tested (TRL 2-3). The level of readiness of the listed technologies is insufficient for application in the FC of the DEMO-FNS facility. It is necessary to increase the level of technology readiness within research and development programs, to create specialized stands for testing and demonstration of technologies, and to create experimental fusion plants for testing and integration of technologies.