Nuclear power in Japan: history and outlook

Japan is an industrialized, developed country that relies heavily on energy to support its economic growth. Before the Fukushima accident in 2011, Japan’s electricity generation mix was dominated by nuclear power. However, following the accident, most nuclear reactors were shut down, and by 2020, the breakdown of electricity generation was 32% natural gas, 31% coal, 18% renewables (hydro, solar, wind and others), and just 6% nuclear power [1]. This article focuses on nuclear power generation in Japan, presenting its history, the reactor technologies used and the innovative power plant and reactor projects currently under development.

History of nuclear power generation in Japan

Japan began developing its nuclear program in the 1950s and commissioned its first nuclear power plant, Tokai, in 1966 [2]. The country rapidly expanded its nuclear infrastructure and built several more nuclear power plants over the following decades. Nuclear power played a key role in reducing Japan’s dependence on energy imports and supporting the country’s rapid economic growth.

However, the Fukushima Daiichi nuclear accident in 2011 profoundly altered the perception of nuclear power in Japan and led to the temporary closure of most of the country’s nuclear reactors. Since then, Japan has taken steps to enhance the safety of its nuclear facilities and has gradually restarted some reactors in line with new safety standards. By 2020, only nine reactors were in operation, with a total capacity of around 9 GW, a fraction of pre-Fukushima nuclear capacity [3].

Nuclear reactor technologies used in Japan

Most nuclear reactors operating in Japan are boiling water reactors (BWRs) and pressurized water reactors (PWRs) [4]. These second- and third-generation reactors use enriched uranium as fuel and water as moderator and coolant. The reactors in operation in Japan are mainly imported or locally developed models based on American and French technologies.

Japan also has a heavy water reactor (CANDU) and a fast neutron reactor (Monju), although the latter was decommissioned in 2016 due to safety issues and high costs [5].

Innovative power plant and reactor projects in Japan

Despite the challenges posed by the Fukushima accident and the declining share of nuclear power in the country’s electricity generation, Japan continues to invest in the development of new reactor technologies and innovative power plant projects.

A notable example of a nuclear power plant project under development in Japan is the Ohma power plant, which is to be equipped with an advanced boiling water reactor (ABWR) with a capacity of 1.38 GW [6]. Construction of this plant was suspended after the Fukushima accident, but resumed in 2015, with commissioning scheduled for 2027 [6].

In terms of innovative reactor projects, Japan is investing in the development of small-scale modular reactors (SMRs) and advanced fast neutron reactors. SMRs are compact, modular nuclear reactors that can be built and deployed faster and at lower cost than conventional large-scale reactors. Japan is currently working on the development of several SMR designs, such as the advanced modular integrated reactor (IMR) and the integrated molten salt reactor (IMSR) [7].

Japan is also interested in developing fast-neutron reactors to reduce nuclear waste production and make more efficient use of nuclear fuel resources. Although the Monju reactor has been decommissioned, Japan continues to collaborate with other countries, such as Russia, on fast-neutron reactors and nuclear fuel cycle research [8].

Nuclear power plants in Japan

Countries producing nuclear power

Sources :

• [1] Ministry of Economy, Trade and Industry (METI), Japan (2021). 再エネ・エネルギー基本情報 [Renewable Energy and Energy Basic Information]. https://www.enecho.meti.go.jp/statistics/renewable_energy/
• [2] World Nuclear Association. (2021). Nuclear Power in Japan. https://www.world-nuclear.org/information-library/country-profiles/countries-g-n/japan.aspx
• [3] International Atomic Energy Agency (IAEA). (2021). PRIS – Country Details: Japan. https://pris.iaea.org/PRIS/CountryStatistics/CountryDetails.aspx?current=JP
• [4] Japan Atomic Industrial Forum (JAIF). (2021). Japan Nuclear Power Plant Map https://www.jaif.or.jp/en/maps/
• [5] World Nuclear Association. (2021). Fast Neutron Reactors. https://www.world-nuclear.org/information-library/current-and-future-generation/fast-neutron-reactors.aspx
• [6] World Nuclear News. (2019). Construction work resumes at Ohma nuclear power plant. https://world-nuclear-news.org/Articles/Construction-work-resumes-at-Ohma-nuclear-power
• [7] International Atomic Energy Agency (IAEA). (2020). Advances in Small Modular Reactor Technology Developments – 2020 Edition. https://www.iaea.org/publications/14761/advances-in-small-modular-reactor-technology-developments
• [8] World Nuclear Association. (2021). Nuclear Power in Russia. https://www.world-nuclear.org/information-library/country-profiles/countries-o-s/russia-nuclear-power.aspx