To meet future energy requirements, the Generation IV International Forum charted the direction of nuclear reactor development by identifying key reactor systems for development. These new reactor systems are meant to optimize safety, efficiency, sustainability, and proliferation resistance for economically viable nuclear energy. Sodium (Na) cooled and lead (Pb) cooled reactors (LFR and SFR respectively) use liquid metals to cool the core. Liquid metal cooling is advantageous because it provides superior heat transfer, improved efficiency, and compact designs, but it poses unique challenges. While both Pb and Na cooled reactors provide operation at high temperature and low pressure (with a significant margin to coolant boiling), Na is very reactive with air and water, and Pb is corrosive to steels at high temperatures. Experimentation at operating conditions is required to learn the behavior of novel fuels types under irradiation. Experience with LFR and SFR fuels in the United States is currently still limited and R&D efforts are needed to support pre-licensing and start of construction activities, as well as to identify technological gaps and other key topics to be addressed. To address these challenges, Niowave proposes to collaborate with LANL and the University of Michigan to fabricate and test novel lead and sodium cooled fast reactor fuel designs in a low flux reactor. This will provide a stepping stone approach to irradiate novel fuels to help provide critical data for fuel licensing and eventual deployment. In fall 2021, Niowave will have a licensed, 230 W subcritical reactor operational for testing and in 2025 will have an operational 230 kW system for fuel irradiation. In Phase I, Niowave will work with its existing collaborators at LANL and UofM to build new relationships with fuels experts at national labs or universities to select fuel candidates to fabricate and test. In Phase II, Niowave and collaborators will continue this collaboration to fabricate and test these fuels in its 230 W subcritical reactor. These new candidate fuels will aim to solve key issues such as eliminating sodium bonding in SFR fuel assemblies. For example, one fuel candidate being considered for this work to solve this issue is vibro-packing uranium nitride fuel spheres into cladding to eliminate the need for sodium bonding in SRF fuels. Additionally, the flexibility of Niowaves system will allow for key in-situ temperature measurements, live flux measurements, and live monitoring of fission gas release to be measured. Irradiations will generate key data for evaluation of fuel performance and identify red flags in candidate advanced fuels before time consuming, highly regulated, and costly testing in a reactor is required.
