日经综述：日本考虑建设下一代快中子增殖反应堆，三菱重工参与600MW研究堆、2028年前后才决定是否进入基本设计

TOKYO -- Japan is weighing the construction of a next-generation fast breeder nuclear reactor, a technology that would reduce the country's dependence on imported uranium.
The world is seeing new movement toward the development of such fast reactors with India in hot pursuit of leaders China and Russia. Japan previously attempted to develop the technology at the Monju nuclear power plant, but decommissioned the prototype reactor a decade ago.
Fast reactors sustain nuclear fission reactions using high-energy -- or "fast" -- neutrons, resulting in greater fuel efficiency because the reactors do not slow down the neutrons as is the case in light-water reactors. Fast reactors primarily use liquid sodium for cooling.
The fact that the process lets uranium fuel be reused has always been a key selling point for resource-poor Japan. Such reactors make it possible to use uranium-238 -- typically not fissionable -- as a fuel while converting it to plutonium, theoretically making more efficient use of uranium.
Russia, China, India and France are among the countries working to develop such reactors as part of their long-term energy strategies.
Russia has the lead in development progress, with its BN-600 reactor at the Beloyarsk nuclear power plant in operation since 1980. The country also has a BN-800 research reactor running, an improvement on the BN-600.
Russia's state nuclear company, Rosatom, plans to begin construction of a commercial BN-1200 reactor, which has a 1,200 megawatt capacity. The plant is expected to begin operating around 2034.
China has also been developing such reactors with full support from Russia, including design support for the China Experimental Fast Reactor, or CEFR, which first reached criticality in 2010.
China now has an experimental CFR-600 reactor in Fujian province, and is planning a commercial CFR-1000 with a 1,200 MW capacity.
Both China and Russia have light-water construction technology that is sufficiently developed for export. The reason for their attention to fast reactors is that they allow fuel to be reused continuously, which is meaningful for national strategies of non-dependence on uranium imports.
In April, India leapt forward by achieving criticality with its Prototype Fast Breeder Reactor, with 500 MW of capacity. "This advanced reactor reflects the depth of our scientific capability and the strength of our engineering enterprise," Indian Prime Minister Narendra Modi posted on X.
India has ample monazite mines that contain thorium. Thorium cannot be used as a nuclear fuel on its own, but can be converted to fissionable uranium-233 using the neutrons from a fast reactor. This is one reason fast reactors could be a dream technology for India, eliminating its reliance on uranium fuel.
The U.S. has effectively ended its research and development of fast breeder reactors. Some private-sector players there are working on next-generation fast reactor development, but few have ever operated actual reactors.
In the West, the U.S., Japan and France once worked together on research and development, but the complexity of fast reactor tech has led to a slowdown.
Controlling such reactors is said to be harder than mainstream light-water reactors due to the use of fast neutrons. Fast reactors require a more complicated setup overall than light-water reactors, including facilities for sodium cooling and reprocessing.
The introduction of safety standards and a focus on cost have also been stumbling blocks to advanced nuclear research and development in Japan, the U.S. and Europe.
In 1995, an accident with Japan's Monju prototype resulted in the reactor being permanently shut down. The decision to decommission it came in 2016, and that work is ongoing today.
Japan's fast reactor ambitions looked doomed, but the country has not given up.
In fiscal 2023, the Japan Atomic Energy Agency -- which also oversaw Monju -- and contractor Mitsubishi Heavy Industries began work on a project for a 600-MW research reactor. The decision will be made on whether to move to the basic design phase in around 2028.
Japanese Prime Minister Sanae Takaichi treats the development of next-generation reactors as crucial. The country has allocated a cumulative 171.4 billion yen ($1.11 billion) of its budget toward the effort from fiscal 2023 through fiscal 2027.
How France decides to act going forward is one of the key variables. When Japan decided in 2016 to decommission Monju, it was thought that the country could participate in and jointly develop France's planned ASTRID demonstration reactor project. But France froze the project in 2019, leaving Japan's own development efforts in limbo.
French President Emmanuel Macron has made nuclear energy development a priority and has once again begun positioning fast-reactor development as a national strategic objective.
France is the only Western country with extensive experience in fast-reactor development. In December 2024, the Japanese and French governments signed an agreement to pool operational experience and technical expertise to improve the safety and economics of sodium-cooled fast reactors.
Next-generation nuclear technologies cannot be commercialized without private-sector operators willing to run commercial reactors.
When Monju's future was under review in 2016, Japan's technology minister asked electric utilities to help keep the project alive, but the request was rejected.
The reactor project scheduled for a construction decision in 2028 is being led by the Ministry of Economy, Trade and Industry, which works closely with industry and electric power companies. The industry minister also chairs the government's fast-reactor development council.