US small reactor supplier TerraPower and Japan expand cooperation

US-based TerraPower, the Japan Atomic Energy Agency (JAEA), Mitsubishi Heavy Industries (MHI) and Mitsubishi FBR Systems (MFBR) have agreed to expand their existing Memorandum of Understanding, signed in January 2022. The memorandum concerns the development of sodium-cooled fast reactors.

In December 2018, the Japanese government adopted a strategic plan for the development of fast reactors, setting out a process for evaluating the performance of various types of fast reactors to be developed through competition among private companies. The plan was subsequently revised by a Cabinet decision in December 2022, when two decisions were made.

First, a sodium-cooled fast reactor was selected as the conceptual design for a demonstration reactor, with development due to begin in fiscal year 2024. At the same time, a manufacturer was selected to be responsible for the fast reactor’s design and related research and development, which will proceed in line with the government’s objectives and policy directions.

Plans to build a demonstration sodium-cooled fast reactor

In July this year, MHI was selected by the Japanese government to lead the conceptual design of a 650MWe pool-type, sodium-cooled fast reactor demonstration project, scheduled to begin operation in the 2040s. MHI will oversee the reactor’s design and research and development in cooperation with MFBR. The resulting reactor design is expected to be ready around 2030.

TerraPower and its Japanese partners have now expanded their Memorandum of Understanding to jointly explore the possibility of cooperating on a reactor design based on Japan’s demonstration programme and TerraPower’s existing technologies. The memorandum has been revised to include improvements to the safety of metallic fuel and an increase in the output of the Natrium fast reactor to improve its cost competitiveness.

US support and TerraPower’s vision

TerraPower has received co-funding from the US Department of Energy through its Advanced Reactor Demonstration Program to test, license and build an advanced reactor by 2030. The company has selected Kemmerer, Wyoming, as its preferred site for the Natrium nuclear power plant demonstration project, which is expected to feature a 345MWe sodium-cooled fast reactor with molten-salt energy storage.

If needed, this technology can temporarily increase the unit’s output to 500 MWe, allowing the plant to respond to daily changes in electricity demand and integrate smoothly with variable renewable energy sources.

"We are excited to expand our cooperation with JAEA as Japan seeks to bring advanced nuclear reactors to market," said TerraPower President and CEO Chris Levesque. "To achieve our climate goals, countries around the world will need to start deploying advanced reactors, and this agreement will help us assess the potential for large Natrium units that can support Japan’s emissions reduction goals."

Benefits of fast reactors and JAEA’s history

In addition to their ability to “burn” radioactive actinides, fast reactors offer the prospect of using uranium resources much more efficiently than conventional power reactors. Fast reactors have been operated in various countries since the 1950s, with some generating electricity commercially.

JAEA already has experience operating sodium-cooled fast reactors, including Monju in Fukui Prefecture and the Joyo experimental fast reactor in Ibaraki Prefecture. However, fast reactor development in Japan was halted after the government decided in 2016 to decommission Monju, following a series of problems that included a sodium coolant leak in 1995.

JAEA President, Masanori Koguchi, announced that JAEA would play a significant role in the strategic plan for fast reactor development.

"We believe that international cooperation is one of the key issues for effective development. Through this expanded Memorandum, we will support cooperation between Japan and the US on fast reactor development," Koguchi added.