Can Nuclear Power Be a Viable Option for 'Decarbonization'?
A simulation debate analyzing the trade-off between nuclear power's decarbonization potential and safety risks. Examines lifecycle CO2 emissions, nuclear waste management, and the optimal combination with renewable energy from the perspective of energy mix structure.
This article is a simulation debate by fictional debaters. It does not represent the views of any specific individual or organization. It reconstructs arguments from different positions for the purpose of structural understanding of the issues.
Setting the Agenda
Fifteen years have passed since the Fukushima Daiichi nuclear accident on March 11, 2011. Japan's energy policy still remains under the shadow of that accident.
Before the accident, nuclear power accounted for approximately 30% of Japan's power generation mix. All 54 reactors were operational, serving as the core of electricity supply as inexpensive "baseload power." After the accident, all nuclear plants were temporarily shut down, and by 2022, the nuclear power ratio had dropped to merely about 6%.
Fossil fuels filled that gap. LNG, coal, and oil account for approximately 72% of the power generation mix, with CO2 emissions reaching about 400 million tons annually from the energy conversion sector alone. About 40% of Japan's GHG emissions originate from energy sources.
The 7th Basic Energy Plan approved by the Cabinet in 2024 set a target of raising nuclear power to about 20% of the power generation mix by 2040. In addition to restarting existing nuclear plants, it also mentions the development and construction of next-generation innovative reactors.
- 7th Strategic Energy Plan (2024): target nuclear share at 20-22%
- Restarts face local consent and safety review barriers; new builds are politically harder
- Renewables alone can't ensure stable supply; battery and grid investment needed
- Continued fossil fuel dependence contradicts the 2050 carbon neutrality goal
Voices calling for nuclear power to be reevaluated as a trump card for decarbonization versus voices insisting that the lessons of Fukushima must not be forgotten. Can the three requirements of energy security, environmental protection, and safety be reconciled?
Round 1: Position Statements
We should look at the numbers without being swayed by emotions. The lifecycle CO2 emissions of nuclear power generation are approximately 12g-CO2/kWh, which is equivalent to wind power (12g) and hydropower (11g), and lower than solar power (26g). In contrast, LNG thermal power produces 474g and coal thermal power produces 943g.
For Japan to achieve carbon neutrality by 2050, decarbonization of electricity is essential. However, renewable energy alone makes it difficult to respond to output fluctuations (solar power is zero at night, wind power depends on wind conditions). Until large-scale battery technology and costs improve sufficiently, nuclear power, which can generate electricity stably 24 hours a day, is a rational choice as baseload power.
Even in the IEA's Net Zero by 2050 scenario, nuclear power is expected to account for about 8% of global electricity generation in 2050. Setting up opposition between decarbonization and nuclear power is based on an incorrect framework for discussion.
Calling nuclear power "clean" based solely on CO2 emission figures ignores the fact that the dimensions of risk are different.
The decommissioning and decontamination costs of the Fukushima accident amount to 21.5 trillion yen (as of 2016) according to government estimates, and up to 81 trillion yen according to private think tank estimates. Even 15 years after the accident, approximately 27,000 people continue to live as evacuees. This cost is not included in the figure "12g CO2 emissions/kWh."
The issue of spent nuclear fuel disposal also remains unresolved. Japan has not even determined candidate sites for final disposal of high-level radioactive waste. The disposal period requires tens of thousands of years. The ethical problem of passing this "negative legacy" on to future generations cannot be offset by discussions of energy efficiency.
The cost of renewable energy is declining rapidly. Solar power generation costs have fallen by about 90% over the past 10 years and are below the cost of new nuclear construction as of 2025. Battery costs are also expected to be about half the current price by 2030. It is more rational to direct funds that would be invested in nuclear power toward renewable energy and storage technology.
Energy policy cannot be discussed using only the two axes of "CO2" and "safety." It is necessary to add energy security—that is, the ability to secure stable and economical energy supply—as a third axis.
Japan's energy self-sufficiency rate of 11.2% is the lowest among OECD member countries. Dependence on fossil fuel imports is directly linked to geopolitical risks such as Middle East situations and the Ukraine conflict. The surge in LNG prices in 2022 directly impacted people's lives in the form of significant increases in electricity rates.
Nuclear power has been positioned as "quasi-domestic energy." Uranium fuel procurement sources are centered on geopolitically stable countries (Canada, Australia, etc.), and the stockpile effect is high because small amounts of fuel can generate electricity for long periods.
However, the pace of nuclear plant restarts has significantly fallen short of expectations. Conformity assessments with new regulatory standards take an average of more than 5 years, and obtaining consent from local municipalities is even more difficult. Only 12 reactors had been restarted as of March 2026. The gap between policy goals and feasibility is serious.
Round 2: Mutual Criticism
The environmental NGO's claim that "decarbonization is possible with renewable energy alone" underestimates the physical constraints of the power grid system. Japan's peak electricity demand is concentrated in summer afternoons and winter evenings, but solar power output decreases precisely during the latter half of these time periods. Wind power has large seasonal variations.
The battery capacity required to achieve 100% renewable energy would be hundreds of times the current installed capacity. We should realistically estimate the costs and resource constraints of installing this much battery capacity by 2050.
Next-generation innovative reactors—small modular reactors (SMRs)—are being developed based on passive safety design philosophy to structurally eliminate Fukushima-type accident risks. We should not ignore the evolution of technology that reflects the "lessons of Fukushima."
SMRs are "future technology" with virtually zero commercial operation experience. The only NuScale project was canceled in 2023 due to cost overruns. Technical possibility and commercial feasibility are different things, and the argument that "SMRs make it okay" is merely wishful thinking at this point.
From an energy security perspective, nuclear power is not omnipotent. Russia holds about 40% of the world's uranium enrichment market share and is not completely free from geopolitical risks. If we truly aim for energy self-sufficiency, investment in domestically produced solar, wind, and geothermal power is rational.
Both arguments fall into the false dichotomy of "nuclear or renewable energy." The principle of energy policy is "diversity," and the risk of depending on a single power source is what should be avoided most.
Nuclear power has realistic constraints in terms of restart pace. Meanwhile, renewable energy has grid constraints. Neither alone can achieve carbon neutrality by 2050. The question should not be "nuclear or renewable energy" but rather "what energy mix can simultaneously satisfy the four requirements of security, decarbonization, economic efficiency, and safety at the highest level"—this is an optimization problem.
Reading the Structure
This debate over nuclear power and decarbonization reveals three structural challenges.
First, the qualitative heterogeneity of risks. The risks of CO2 emissions (climate change) and nuclear accidents (radioactive contamination) are heterogeneous in terms of probability, scale, and time axis. CO2 emissions certainly cause climate change, but the damage accumulates gradually. Nuclear accidents have extremely low probability of occurrence, but once they happen, they cause catastrophic and irreversible damage. Comparing these two types of risks on the same scale is methodologically difficult in itself.
Second, the double bind of time horizons. The 2050 carbon neutrality deadline is approaching, but nuclear plant restarts and new construction take more than 10 years, and renewable energy grid development takes about the same amount of time. Energy policy is constrained by the contradiction that "we cannot wait" in reality while "rushing increases risks."
Third, the governance problem of "who decides." While energy policy is directly linked to national security, nuclear plant siting concentrates risks on specific regions. There is fundamental tension between national-level rationality and regional-level acceptability. The question posed to Japanese society after the Fukushima accident is not about the accuracy of technical risk assessment, but rather the problem of democratic legitimacy: "who will bear that risk?"
The optimal solution for energy mix cannot be mathematically derived. It is politically constructed as an accumulation of value judgments about "what risks, to what extent, and who will bear them."
References
7th Basic Energy Plan
Agency for Natural Resources and Energy. Agency for Natural Resources and Energy
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Net Zero by 2050: A Roadmap for the Global Energy Sector
International Energy Agency (IEA). IEA
Read source
Progress and Lessons of the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station Accident
Nuclear Regulation Authority. Nuclear Regulation Authority
Read source
World Nuclear Performance Report 2024
World Nuclear Association. World Nuclear Association
Read source
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