Conventional nuclear power

Currently, all of the world's nuclear power plants(...)( any exceptions are experimental and not scaleable yet ) run on conventional nuclear power: nuclear fission that depends heavily on uranium-235.

Scarcity of uranium-235

Major problem

uranium.reserves

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.

Citation:
Uranium 2020: Resources, Production and Demand ('Red Book')
"The total recoverable identified resources to $260/kg U is 8.070 million tonnes U."

nuclear_power_plant.efficiency

33%

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

energy.tfc

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

This is the main reason why nuclear power only provides a small fraction of the world's energy. Uranium-235 is a scarce mineral - far more scarce than fossil fuels.

If all the world's energy were to come from nuclear, we'd run out of uranium-235 in about 4 years. (see maths) years energy.tfc(calculation loading) (more)~ We'd run out even faster if all nations were developed.

~ In either case, conventional nuclear power can't really meet global energy demands. Best case, it might be sufficient for baseload electricity only (which is a smaller part of total energy demand).

Possible solutions:

Breeder reactors, to make use of uranium-238, which is over 100 times more abundant.
Extracting uranium from seawater^{[unlikely to be viable]}

Nuclear waste

Long-term problem

Since the reactors only make use of the uranium-235 component, the remaining matter becomes "spent fuel" and must be disposed of. This nuclear waste is still radioactive enough to cause harm to anyone exposed to it without protective equipment. It remains this way for millions of years.

Possible solutions:

Breeder reactors, which could keep obtaining energy from the spent fuel (mostly uranium-238) until there's barely any radioactive waste left at all.

Risk of meltdowns

Generally manageable

Meltdowns have happened twice in history: Chernobyl and Fukushima. Nuclear plants have since been designed to not repeat the mistakes of the past. ^{[ELABORATION needed]} Then again, some people say there are still unknown risks. ^{[debate needed, perhaps]}

Weapons proliferation

Under control

Reactors are well designed to prevent people from stealing uranium to make thermonuclear bombs. Governments of course still have nuclear warheads, which is still a major issue in itself.