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Finland in Front: The World’s Likely First Spent Fuel Repository Moves Toward Licensing
The year 2024 is shaping up to be a historic one for Posiva, the waste management organization owned by Finland’s two nuclear power plant utilities, Fortum and Teollisuuden Voima. The company is looking to receive regulatory approval of its operating license for the Onkalo deep geological repository for high-level radioactive waste by the end of the year.
M. Nedim Cinbiz, Chase N. Taylor, Erik Luther, Holly Trellue, John Jackson
Nuclear Technology | Volume 209 | Number 1 | January 2023 | Pages S136-S145
Technical Note | doi.org/10.1080/00295450.2022.2121583
Articles are hosted by Taylor and Francis Online.
The emergence of microreactor technology has helped to drive supporting nuclear materials qualification and acceptance processes. One essential component in these small reactors is a solid moderator, which typically consists of metal hydride and cladding. While the behavior and performance of metal-hydride moderators go back to early advanced reactor development for nuclear-powered aviation and space propulsion, there remains a knowledge gap in the understanding of hydrogen transport–related phenomena and irradiation performance for hydride moderators. This impacts the acceptance/qualification of hydride moderators for microreactors.
The goal of this technical note is to lay out a potential path forward for advanced moderator qualification and acceptance for designers and developers of microreactors. The proposed approach has benefited from a model microreactor core with the design parameters of a hydride moderator. Based on the model core and design parameters, a simple chart was developed for the major challenges of hydride moderators where potential incidents, causes, effects, and resolutions are described. The relation between the offered resolutions and the maturity of the metal-hydride moderator technology was emphasized using technological readiness. Technological readiness levels (TRLs) were clustered to three sets: physical phenomena related, reactor irradiations, and system demonstration. Some essential needs to fill the knowledge gaps are discussed for physical phenomena–related TRLs. For reactor irradiations, the importance of identifying goals and priorities is stressed to reach certain TRLs. For system demonstration, it is noted that metal-hydride moderator qualification must comply with the overall microreactor design.