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All of today's nuclear power plants run on nuclear fission.


Today's nuclear plants get their energy from uranium-235, which is a scarce mineral. If the whole world was powered this way, we'd start to run out of it in less than 4 years:

8.070 million tonnes uranium_natural
Global uranium mineral reserves, measured in energy units
The calculator understands "tonnes uranium_natural" as an energy unit. It's based on the fact that natural uranium is just 0.7% uranium-235 (the isotope we extract energy from). The rest is uranium-238, which isn't useful for energy unless we use breeder reactors.

Uranium 2020: Resources, Production and Demand ('Red Book')
"The total recoverable identified resources to $260/kg U is 8.070 million tonnes U."
Electrical output divided by the heat energy of the nuclear reactor
Nuclear power plants convert heat (from uranium-235, currently) into electricity. The process is approximately 33% efficient.

Citation: Key World Energy Statistics 2020 (IEA report) - Page 73 - Glossary - Nuclear
9937.70 Mtoe/year
Global energy usage - total final consumption (TFC)
Includes: fuel (80.7%) + electricity (19.3%) AFTER it is generated.

Does not include the fuel used in generating electricity. See [energy.tes] for that.

Citation: "Key World Energy Statistics 2020" IEA
- Page 47 - Simplified energy balance table - World energy balance, 2018
uranium.reserves * nuclear_power_plant.efficiency
years energy.tfc

We'd run out even faster if all nations were developed.

Since uranium-235 and uranium-238 occur together in naturein the following proportion: uranium-238 (99.3%) and uranium-235 (0.7%). The proportion does not vary, no matter what part of the Earth's crust the uranium is mined from., the 238 component ends up as waste.

These two problems could be solved with breeder reactors that make use of uranium-238 and/or thorium - both of which are far more abundant fuels. However, major innovations are needed before this is viable and safe.

For now, nuclear power is best suited as only a baseload.

There is also some talk about extracting uranium from seawater, but the viability of this is questionable (like other trace minerals), because the concentration is extremely low.

Safety concerns


If uranium gets into the wrong hands, it can be used to make thermonuclear bombs. Nuclear power plants need strong redundant security measures to mitigate this risk.


This has happened twice in history: Chernobyl and Fukushima.


Nuclear fusion is not currently viable for generating power. It has great potential solve the energy crisisit could power the world for billions of years, from only tiny amounts of abundant material, and with almost no pollution, but it is nowhere near ready yet (despite some misleading news headlines).

The most recent breakthrough was in December 2022. Fusion research & development is certainly worthwhile, but we can't "put all our eggs in one basket". Climate change is near a tipping point, so we need clean energy sooner than fusion might be available.