Election in South Korea; bad news for clean energy.

[brimstoneSalad]

I think the risk of nuclear weapons proliferation is often understated because people forget to balance the low probability of something bad happening with the high magnitude of the effects.

To the contrary, it's actually massively exaggerated -- like shark attacks and terrorism itself -- because it's scary.

Nuclear power doesn't really increase the risk of nuclear weapons proliferation; it probably reduces them.

1. Nuclear power is the best way to use up old nuclear weapons; current stockpiles are the greatest risk to proliferation.
2. Reactor grade uranium can not be used to make bombs, there is no immediate risk of that (it has to be enriched, at which point you can make bombs from rocks if you have the centrifuges for it).
3. The waste from nuclear reactors can not in itself be used to make a bomb; it also has to be substantially reprocessed. (It can be used to make a "dirty bomb" which is a conventional explosive with radioactive material in it, but that's very different).
4. Nuclear power reduces the impetus for terrorism by increasing the quality of life for people without power, and massively reduces climate change (which is a much more serious existential threat) that will inevitably result in destabilization and increase in terrorism.

Yes, it's unlikely that terrorists working within the UK for example would somehow inflitrate a nuclear power station and get material and use it to make a bomb, but how unlikely are we talking here?

Well, the material can't make a nuclear bomb. So, even if they did -- less than a one in a thousand chance, maybe one in a billion -- they'd just have something they can't use right away for anything but a dirty bomb (which is nowhere near as dangerous, and far less practical than biological weapons). Any theft in the developed world would be a very visible event.
Scenarios that imagine terrorists accessing nuclear waste involve implausible highly trained teams with thermal lances and heavy-lift helicopters.
Nuclear facilities are well guarded and cool waste is sealed in heavy metal vaults; it just not plausible. Anybody with those kinds of resources is going to attack much more vulnerable targets. It's just not a good use of resources and would do nothing but draw attention to them.

The more plausible scenarios involve governments trying to steal waste from under regulators' noses. This can be counteracted with modern imagine technology, like muon tomography. Or we can just collect the waste like Russia does (or did?).

Say there's a 1 in 1 thousand chance that they could do this and kill 1 million people, in assessing risk that could be considered the same as 1000 people certainly dying.

If that were the risk, sure.
It isn't, but even if it were, you have to account for the much larger risk of NOT using nuclear power. Global warming is much more of a sure thing, and the death and chaos it will cause much more serious.

Yes I know the nuclear processes and materials in power stations and weapons are quite different but it's really no coincidence that the UK and US built nuclear weapons and then opened power stations later.

What are you trying to say?

The nuclear bomb was built first because we were in war. That's why we did it.
Power applications came later in peace-time.

That doesn't mean that building a bomb is easier.

Uranium has to be much more enriched to build a bomb, and the structural requirements are much more extreme.
There have even been natural nuclear reactions in the past.
https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

It's very easy to build a nuclear power plant. The tricky part comes in with managing the reaction to keep the volatiles from boiling off and the material from melting into its substrate and extinguishing the reaction.

Also, we have countries like Iran that have nuclear power stations and great worry about what that means for weapons development. So, there is obviously some correlation.

The concern is if they build breeder reactors and make weapons grade material in them which can be chemically separated. That's why they need some external monitoring. Breeders can enrich material, and that's legitimately dangerous, but not all reactors are breeders.

The best system is to give them the fuel, and then take their waste away, so we can make sure they're giving us back everything they get, and not let them process anything. Centrifuges are the problem, not the reactors. You can build a bomb without a nuclear reactor, and a reactor doesn't help you much unless it's a breeder (which is a special design that would be obvious to inspectors, and a technology we don't need to teach them).