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Short answer
If “safe” is taken to mean “causes few deaths and illnesses per unit of electricity generated and can be operated with an acceptably low probability of major accidents,” the balance of evidence says that nuclear power is already one of the safest large-scale energy sources, and it is getting safer. It is not risk-free: severe accidents are possible and long-lived radioactive waste must be managed indefinitely. But measured against the everyday harms of coal, oil, gas or even hydro, nuclear’s health and environmental record is remarkably good, and modern designs greatly reduce the residual risks.
Detailed discussion
How do we measure safety?
a. Routine health impacts (air pollution, radiation releases).
b. Accident fatalities and land contamination.
c. Long-term waste risks.
d. Security and proliferation risks (outside the scope of this brief reply).
Empirical record of fatalities
• A synthesis of peer-reviewed studies compiled by Our World in Data finds about 0.07 deaths per terawatt-hour (TWh) of electricity for nuclear power, compared with 24.6 for coal, 18.4 for oil, 2.8 for gas and 0.04 for wind and solar [1].
• These figures include the three large civil nuclear accidents to date––Three Mile Island (1979, no direct deaths), Chernobyl (1986, dozens of confirmed acute deaths and an estimated few thousand eventual cancer deaths) and Fukushima Daiichi (2011, no radiation fatalities but ~2,300 indirect evacuation-related deaths). Even after those events, nuclear has killed orders of magnitude fewer people per unit of energy than fossil fuels [1][3].
Probability and consequences of severe accidents
• Probabilistic safety assessments performed for U.S. reactors estimate the chance of a core-damage event at roughly 1 in 10,000 reactor-years, declining for newer “Generation III+” plants with passive safety systems [4].
• Sandia National Laboratories’ accident consequence analyses show that even a full core melt would rarely cause large public radiation doses if modern containment and emergency measures work as intended [4].
• The Economist’s 2022 review notes that, including Fukushima, the historical frequency of severe accidents is roughly consistent with such probabilistic estimates and is far lower than the catastrophic-failure rate of large hydro dams [3].
• The IAEA’s 2024 Nuclear Safety Review concludes that “global nuclear safety performance remains high,” highlighting declines in unplanned reactor shutdowns and continued reinforcement of post-Fukushima protections (e.g., flood and blackout defence, filtered venting) [2].
Routine operations and radiation exposure
• Typical public doses near well-run plants are below 0.01 mSv per year—less than 1 % of natural background radiation [2].
• Occupational doses have also fallen; average worker exposure at U.S. plants is about one-tenth of the legal limit and continues to decline [2].
Waste management
• Spent fuel is highly radioactive but small in volume—about 3 m³ per GW-year. All of it worldwide could fit in a football-field-sized warehouse packed 10 m high.
• Dry-cask storage has had no radiation injuries since its introduction in 1986, and deep-geological repositories (e.g., Finland’s Onkalo) are beginning to operate, suggesting long-term isolation is technically feasible [2].
New reactor designs
• Generation III+ water-cooled reactors (EPR, AP-1000, Hualong One) add passive cooling, core catchers and double containment.
• Small Modular Reactors and some Generation IV concepts (sodium, molten-salt, high-temperature gas) are designed so that decay heat can be removed without pumps, pushing core-damage probabilities to 10⁻⁷ /reactor-year or lower, according to vendor safety cases reviewed by regulators [2][4].
Remaining concerns
• Human error, ageing infrastructure and external hazards (earthquakes, floods, sabotage or war—as seen at Ukraine’s Zaporizhzhia plant) mean diligence is essential.
• Public perception lags the statistical reality; as Scott Alexander notes in his review of “Safe Enough?”, nuclear safety is judged against a “zero-risk” ideal rather than against real-world alternatives, stalling deployment despite its good record [5].
Conclusion
Nuclear power is not absolutely safe—no energy source is—but the data show that it is among the safest ways we currently have to make reliable, large-scale electricity, and technological as well as institutional advances continue to lower its residual risks. The main safety challenges today are sociopolitical (public acceptance, robust regulation, security in conflict zones) rather than technical lethality.
Sources
[1] Our World in Data – “What are the safest and cleanest sources of energy?” (https://ourworldindata.org/safest-sources-of-energy).
View: Aggregated epidemiological studies show nuclear has the second-lowest death rate (0.07 deaths/TWh), far below fossil fuels and slightly above wind/solar.
[2] International Atomic Energy Agency – “Nuclear Safety Review 2024” (https://www.iaea.org/sites/default/files/gc/gc68-inf2.pdf).
View: Global nuclear safety performance is high and improving; post-Fukushima corrective actions, ageing-management programmes and new passive-safety designs further reduce risk.
[3] The Economist – “How safe is nuclear energy?” (19 July 2022) (https://www.economist.com/graphic-detail/2022/07/19/how-safe-is-nuclear-energy).
View: Statistically, nuclear is safer than coal, oil, gas and hydro; public dread is disproportionate to measured risk.
[4] Sandia National Laboratories – “Nuclear Energy Safety Studies” (https://energy.sandia.gov/programs/nuclear-energy/nuclear-energy-safety-studies/).
View: Probabilistic risk assessments and accident consequence models show very low frequencies of severe accidents and limited off-site health impacts when modern mitigations are in place.
[5] Astral Codex Ten – “Your Book Review: Safe Enough” (https://www.astralcodexten.com/p/your-book-review-safe-enough).
View: Public and regulatory expectations often hold nuclear to a perfection standard, despite evidence that it is already “safe enough” compared with alternatives.