Nuclear Power Plant Systems

While Carbon Neutrality becomes a global goal to achieve, power shortage in winter, fuel price escalation due to the Russian invasion in Ukraine and ensuing electricity price escalation have become realistic risk. Under such environment, the Government GX Executive Implementation Council expressed its basic policy of operating nuclear power plants beyond 60 years, and developing and constructing next-generation innovative nuclear reactors. This motivated expectations for nuclear power plants.

Development activities are being geared for innovative light water reactors with increased nuclear safety as compared to the existing conventional large-scale light water reactors, and small-scale nuclear power units having advantages of low investment risk in the deregulated electricity market and rational features on nuclear safety. In North America, some of such small-scale reactor concepts are on the review process by the regulatory bodies. Technological development is in progress, under governmental support in various countries, for high temperature gas reactors available for hydrogen production, or fast reactors capable of maximum use of uranium resources and decreasing high level radioactive waste. In Japan, demonstration plant projects of these reactors are being geared. Some JEMA member companies involve themselves in their own technological development and in various forms of international cooperation as joint development with foreign companies, investment to foreign projects, etc.

Development of safety strengthened light water reactors

Safety-strengthened and innovative light water reactors (medium/large-scale), coexistable with intermittent renewable energy sources, are being developed. These reactors will offer nuclear power plants with maximum safety and reliability and meet the new safety regulatory standards, which were newly enacted in response to the Accident at the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company. These reactors, therefore, equip themselves with intensive robustness against natural disasters such as earthquakes or tsunami, or against severe accident using state-of-the-art knowledge and technologies such as accident resistant fuel, and against external threat (terrorism) such as large-size aircraft crash; and others. Preliminary discussion started in FY 2024 with the Nuclear Regulatory Authority on SRZ-1200 as a typical candidate. The reactor concept is based on the extension of existing technology. Social implementation is expected at an early opportunity.

Plutonium utilization in light water reactors

Nuclear power reactors use uranium as fuel. Natural uranium contains only 0.7% of fissile U-235 and the residual 99.3% is less fissionable, mostly U-238. But the U-238 is converted in the reactor to plutonium isotopes by nuclear reactions and can be used as fuel. Some of the existing nuclear power plants are experiencing use of U-Pu mixed oxide fuel (MOX) extracted from the reprocessed spent fuel.

Development of small light water reactors

Small light water reactors have advantages of limited gross outputs and improving both safety and economy in a simple system, an example being the emergency core cooling systems (passive safety systems) with no large water pumps or power generators. First commissioning of small light water reactors can be foreseen in around 2030 if regulatory reviews, and marketing in North America go smoothly. Japanese firms are engaged in investing in foreign companies and joint development projects. Early deployment of excellent small light water reactors, when proven in other countries, is expected in Japan.

High temperature gas-cooled reactors

High temperature gas-cooled reactors can generate heat as high as 950 deg C in the reactor and are expected to develop new industrial opportunities in carbon-free energy including hydrogen production. Inert gas of Helium is used as a coolant, and the fuel is composed of fuel micro-particles coated with pyrolytic carbon and silicon carbide in multiple layers. High temperature gas-cooled reactors also have high safety features of preventing fuel overheating in an accident owing to their low thermal power densities and high radiant heat transfer. A demonstration project of high temperature gas cooled reactor is expected in Japan.

Fast reactors

Plutonium utilization in nuclear power generation can be made effective by plutonium fissions by fast neutrons through controlling neutron moderation in the reactor (FR: Fast Reactors). In FY 2023, the fast reactor demonstration plant development plan has been fixed and the core organization for its construction has been identified. In parallel with the demonstration project in Japan, further international cooperation in real projects for fast reactor development is expected, an example being, a new fast reactor “Natrium” in the US. The construction permit has been applied and the groundbreaking for a unit took place.

Status of nuclear fusion research

The experimental reactor JT-60SA, a Japan-European Joint Project for plasma research, has achieved in October 2023 the first plasma generation. The international ITER joint project, too, is steadily ongoing. For facilitating industrial application, a new Japan Fusion Energy Council (J-Fusion) has been founded in March 2024. The Cabinet Office took the initiative for its foundation. JEMA strengthens its relevant activities through cooperation with related organizations, based on the outcome of JEMA dedicated committee, “Issues for industrialization,” for example.