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Background

Fission is a very controversial topic: some people think some use of nuclear fission will be essential to plug the hole left by fossil fuels before we manage to scale up renewable energy; others think the costs and the problem of disposal of nuclear waste make it unacceptable as an option.  We need to explore this point so that we understand what the costs and benefits are likely to be before we decide whether we want to support an increased role for fission over the next few decades.

There are a number of competing designs for large nuclear fission plants, so we need to understand the pros and cons of each.  In addition, we should also consider the options for using more small scale fission reactors.

Details

Traditional Nuclear Plants

Nuclear power (whether fission or fusion) is simply a source of heat - the least useful form of energy.  In order to convert this heat to something more useful, we typically use it to boil water, which then drives turbines, which generate electricity.  This is why nuclear power is used on land which is near a substantial water supply, and on submarines, but not in planes or cars.

Traditional nuclear plants are reliable and essentially safe, but they do have several significant drawbacks.

• The by-products of fission reactors can be used to produce nuclear weapons, so the more nuclear fission reactors we build, the greater the risk the by-products will fall into the wrong hands.
• We do not have an effective way to dispose of the radioactive waste produced by fusion reactors, which needs to be stored for thousands of years.

Small Alternatives

Some years ago, I heard about a young man who was developing the idea of small 'neighbourhood' nuclear generators, which would be failsafe and comparatively clean, and would be more economical because a standard design could be rolled out in hundreds of places.  That idea seems to have disappeared, but some of the ideas can be seen in a slightly different form: a mobile nuclear reactor, which can be transported to where the power is needed.  Project Pele (as it is called) 'broke ground' in 2024, and is planning to produce an operational reactor in 2026.

Something closer to the original concept can be seen in this video: Why Thorium is about to change the world.  Instead of using high pressure water to cool the plant, the plan is to use molten salt at atmospheric pressure - so it will not explode if anything goes wrong, and you can easily supply a failsafe drainage system to store the radioactive material should anything go wrong.  And the waste products only need to be stored for a few hundred years - something we can reasonably plan to do.

One advantage of small local nuclear generators would be their use in a 'Combined Heat and Power' system, where the waste heat produced by the plant is then used directly in homes and offices, instead of being thrown away.  This increases the overall efficiency of the process, both by using energy which would otherwise be wasted, and also by avoiding the need to use energy to heat the homes and offices.

Alternatives

There are very few alternatives if we want to avoid burning fossil fuel.  The sun does not always shine, and the wind does not always blow; tides flow predictably, but we can't yet use them commercially.  Hydroelectric is more reliable, but it still generally depends on rainfall, and it rather needs access to significant vertical drops so it can't be used everywhere.