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Five Years since Fukushima

Revisiting the Prospects of Nuclear Energy in Japan

An Interview with Kei Shimogori

By Sara Itagaki
May 11, 2016

Since the nuclear accident triggered by the Tohoku earthquake and tsunami on March 11, 2011, Japan’s energy calculations have drastically changed. The immediate loss of nuclear power, which provided 30% of the country’s electricity, was a huge blow for Japan’s energy security and environmental outlook. Over five years have passed since the triple disaster, and the overhaul of Japan’s energy strategy is finally coming to effect. To better understand the future of nuclear energy in Japan and the implications for the broader Asia-Pacific, NBR spoke with Kei Shimogori (Institute of Energy Economics, Japan) about the changing policy environment for nuclear energy and the long-term prospects for Japanese energy security.

What are the key lessons from the Fukushima accident for nuclear energy use?

I would like to point out two lessons here based on the report from the International Atomic Energy Agency (IAEA) about the Fukushima Daiichi accident. The first lesson is on the vulnerability of nuclear power plants to external hazards. During the earthquake, there were no indications that the main safety features of the Fukushima Daiichi nuclear power plant were compromised by the vibratory ground motions. However, the original plant design did not provide safety margins for extreme external flooding, such as the 33-foot-high tsunami that hit Japan. The Fukushima accident reminded regulators and utilities that the safety of nuclear power plants needs to be re-evaluated on a periodic basis to adopt advances in scientific knowledge and promptly implement necessary corrective actions or compensatory measures.

The second lesson is to seriously consider the importance of the “defense in depth” concept under which a plant’s defense mechanism is provided by multiple and independent means at each layer of protection. The design of the Fukushima Daiichi nuclear power plant did not fully address external hazards like a tsunami, and, as such, the means for injecting a coolant in the event of total power loss had not been sufficiently prepared. If the defense-in-depth concept was more deeply considered at the design stage, the subsequent meltdown could have been avoided. Thus, this concept is the key to ensuring a high level of nuclear safety, but the concept needs to be embedded at all levels through adequate independence, redundancy, diversity, and protection against internal and external hazards.

Beyond these immediate lessons on accident prevention, regulators and utilities also need to focus on improving mitigation measures. Measures for mitigating the impact from core damage had not been sufficiently implemented before the Fukushima accident. Therefore, venting equipment with filters is now being installed at some reactors in Japan to reduce the release of radioactive materials after an accident.

How has the power sector adapted to the decreased share of nuclear energy in Japan’s energy mix?

Japan has successfully avoided a blackout since the accident because utility companies have used fossil fuel power plants to compensate for the lack of nuclear energy. However, doing so has increased the cost of importing fossil fuels, leading to higher electricity rates and a historically large trade deficit. In light of these challenges, utilities have made efforts to restart their idle reactors while complying with the new regulatory requirements, but their progress has not been significant.

It is clear that the government plans to continue the use of nuclear energy. After the Fukushima accident, the Ministry of Economics, Trade and Industry outlined Japan’s energy mix through 2030 based on a comprehensive review to overhaul the country’s energy policy. This plan implied that Japan will continue to use nuclear energy, although nuclear energy’s share of 20%–22% of total electricity represents a decrease compared with plans before the accident.

Yet, because the private utilities operate all the nuclear power plants in Japan, despite being under the umbrella of the government’s nuclear energy program, the choice of whether to extend the operating period of the reactors, replace the old reactors with new ones, or construct new reactors will depend on the management decisions of the utilities companies. Therefore, there is a possibility that the 2030 target will not be achieved depending on how the restart process and deregulation of the electricity markets move forward.

Accelerating the restart review process is one of the challenges for the nuclear sector in Japan. According to the OECD’s Nuclear Energy Agency, one of the foundational elements for nuclear energy regulators is a staff that is well-trained and engaged. Unfortunately in Japan, because the new regulator, the Nuclear Regulation Authority, was established only after the accident, the agency’s dearth of high-quality human resources has caused a delay in the restart review process. Additionally, the deregulation of domestic electricity markets will increase market competition in wholesale electricity, which may force the premature shutdown of some old nuclear power plants. This is because the investment required to extend their operating lifetime or to improve nuclear safety may exceed the economic benefit in tight markets. Also, the longer time periods required for recovering costs and the greater uncertainties with nuclear power make it difficult to construct new reactors in deregulated electricity markets.

The triple disaster and public protests against nuclear energy in reaction to local damage has allowed debates on nuclear energy use to resurface, including concerns over safety, economic efficiency, and dependence. How has the government addressed these concerns?

In order to address public concerns over safety, the Nuclear Regulation Authority was established to provide stronger requirements for nuclear energy facilities. This new and independent body will improve transparency and governance and thereby help repair the reputation of nuclear authorities, which was damaged after the crisis due to the intimacy of the government and regulators. The government will now follow the Nuclear Regulation Authority’s judgment on whether utility companies have conformed with the requirements and then proceed with the restart. In the case of a restart, the government must make an effort to obtain the understanding and cooperation of the host municipalities and other relevant parties.

Additionally, in response to the rising costs of energy after the crisis, the government established the Power Generation Cost Verification Working Group in 2015 to provide estimates of the levelized cost of electricity (LCOE) in Japan. The most recent estimates indicate that the LCOE is lowest for nuclear: measured by yen per kilowatt hour (kWh), the cost of nuclear is 10.1 yen/kWh, followed by coal (12.3 yen/kWh), gas (13.7 yen/kWh), oil (30.6–43.4 yen/kWh), solar (29.4 yen/kWh), and wind (21.6 yen/kWh), with significant uncertainties in the longer-term prices for fossil fuels, solar, and wind. [1] The LCOE of solar photovoltaic and on-shore wind systems is projected to decline to 12.5–16.4 yen/kWh and 13.6–21.5 yen/kWh, respectively, by 2030. However, the LCOE of nuclear energy is still expected to be lower.

In its Strategic Energy Plan, the Japanese government mentions that energy policy should ensure “3E+S,” which stands for energy security, economic efficiency, environment, and safety. In this context, compared with fossil fuels or other energy sources, nuclear energy has three characteristics: one is the supply stability of the resources. The uranium resources are distributed among politically stable countries and nuclear fuel has usually been loaded for four to five years. The second is low and stable operational costs. The fixed costs are larger than variable costs for nuclear energy, so the LCOE of nuclear energy is low if nuclear power plants can stably operate in the long term. The third is that energy from nuclear plants is free from greenhouse gas emissions. Also, the life-cycle emissions, including construction of the plant, mining and processing the fuel, disposal of used fuel, and decommissioning, are far less than those of fossil fuel power plants. In this context, the government recognizes nuclear energy as “an important base-load power source as a low carbon and quasi-domestic energy source.” [2] At the same time, the government also stated that “dependency on nuclear power generation will be lowered to the extent possible” based on the public concern about nuclear safety. [3] However, given that the energy mix target through 2030 included a significant share of nuclear energy, there is no doubt that the government plans to use nuclear energy continuously.

If Japan plans to rely on nuclear energy, it should consider how to ensure the ongoing safety of the restarted reactors. Strengthening regulatory requirements is not the only way to improve nuclear safety. The experiences of the U.S. Nuclear Regulatory Commission and the nuclear industry in the United States after the Three Mile Island accident provide several lessons on improving both the safety and performance of nuclear plants. The regulators should communicate with the utilities and nuclear industry to make more rational regulations based on plants’ operating experiences. Also, utility companies should cooperate with each other and take voluntary measures to improve their reactors’ safety and performance—for example, by promoting a probabilistic risk assessment approach and peer-review process.

Has increased domestic pressure over nuclear energy use since the accident affected Japan’s leadership on global governance issues such as safety and institutional standards and nonproliferation?

The Fukushima accident has not affected Japan’s policy on nonproliferation issues. Drawing on the experiences and lessons learned, Japan continues to actively contribute to strengthen nuclear nonproliferation through reinforcement of the IAEA safeguards, stringent export controls, and participation in nuclear security summits. Japan agreed to the IAEA’s integrated safeguards in 2004, and IAEA inspections did not find any indication of the diversion of nuclear material placed under safeguards or of undeclared nuclear material or activities. Japan is the first case in which integrated safeguards were implemented in a state with large-scale nuclear activities, and since then the country has maintained one of the strictest nonproliferation regimes in the world.

In addition, the government promotes a nuclear fuel cycle that reprocesses spent fuels and effectively utilizes the plutonium retrieved. This policy reflects Japan’s emphasis on the efficient use of resources and the goal of reducing the volume and harmfulness of high-level radioactive waste. With respect to the use of plutonium, the government has maintained the policy of not possessing plutonium reserves without a specified purpose. Thus it is clear that Japan manages plutonium appropriately while remaining highly accountable to the international community.

Nuclear expansion is a clear trend in Asia-Pacific, which is home to 45 of the 64 nuclear reactors currently under construction. Given Japan’s experience, what role could the country play in the regional governance of nuclear technology and emerging nuclear states?

Japan could support development of human resources and institutional infrastructure in the region through cooperation with international organizations like the IAEA or regional organizations, for example the Forum for Nuclear Cooperation in Asia or the Asian Nuclear Safety Network. If a significant accident were to occur at a nuclear power plant in the region, given Asian countries’ geographic proximity, it would cause widespread damage in other countries and heighten public concerns over nuclear safety and radioactive hazards. Therefore, it is necessary to review appropriate nuclear security and safety management measures and to establish a shared awareness in light of the energy situations, infrastructure, technological levels, and other circumstances of emerging nuclear countries in Asia. In this context, the Japanese government and regulators could coordinate with their counterparts in other countries to establish an information-sharing system for accidents and consider cross-border cooperation.


[1] Ministry of Economy, Trade, and Industry (Japan), “Report on Analysis of Generation Costs, Etc. for Subcommittee on Long-Term Energy Supply-Demand Outlook,” Power Generation Cost Analysis Working Group, May 2015, 11–13,

[2] Ministry of Economy, Trade, and Industry (Japan), Strategic Energy Plan (Tokyo, April 2014), 24,

[3] Ministry of Economy, Trade, and Industry (Japan), Strategic Energy Plan.

Sara Itagaki is a Project Associate with NBR's Trade, Economic, and Energy Affairs group.

Kei Shimogori is a Researcher for the Nuclear Energy Group of the Strategy Research Unit at the Institute of Energy Economics, Japan (IEEJ). Her current research focuses on nuclear power policy and developments in Japan and the world, as well as on shale gas developments in North America. In her time at IEEJ, she has also written on electricity market reform and nuclear power in the United Kingdom.

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