Someone please correct me if I'm speaking inaccurately, but early reactor design (1950s/60s/70s) focused on light water reactors, which meant enriched U-235 fuel (@ ~3%?). By design, these reactors also convert a portion of their U-238 to P-239, only some of which is then consumed in the reactor.

Consequently, for widespread nuclear reactors (read: in many countries), you also had widespread proliferation of lightly enriched uranium (in the fuel) and proliferation of plutonium (produced in the fuel as the reactor runs).

Both of these remove the most time and energy consuming step (low level enrichment) as an obstacle to state nuclear weapons development.

And they're fundamental to the way light water reactor technology works, especially with the limitations of the period. So the only way you could have had proliferation-resistance would have been to have some sort of global fuel-control and -custody agreement (presumably run by the United States, USSR, and maybe France, depending on the time period). Which sovereign countries would have likely felt some kind of way about.

The number of new nuclear reactors only stopped growing in the 80's. In any case I don't think access to material is the limiting factor in nuclear proliferation. If we're talking about the US and USSR, it's completely irrelevant, even if they had 100x more reactors since they already have more than enough bombs to more or less to blow up the entire world. Other western countries either have enough nukes already or don't need or want them and I don't see why would they export technology or material to countries which are hostile to them.

It's not obvious to me that having more nuclear reactors in the US, Britain or Germany would had made it significantly easier for rogue states like Iraq, Iran or North Korea to developed nuclear weapons.

So you're talking about having more nuclear power, but only in First World economies?

That seems... ethically dubious.

Why is it anymore ethically dubious than having more solar or wind power in first world countries? But no, I'm not necessarily saying that. I just disagree with the claim that if nuclear power continued growing at the same rate as it did prior to 1979 that would somehow have lead to higher proliferation of nuclear weapons.

It's ethically dubious because solar or wind power wasn't an option in the 50s-70s. So you're effectively gating the majority of the world off from nuclear power, enjoyed by developed economies. Which would have developed economies of scale (see: France) with the end result of developed countries having access to cheaper power than developing ones.

And I'm confused. Your reasoning around why more reactors wouldn't have increased nuclear weapon proliferation was contingent on only the US, USSR, Britain, and Germany (and presumably countries like them, to an approximation) having more reactors.

Either you get to say that (a) all countries, or (b) only "responsible" (for lack of a better word) countries should have used more nuclear power.

If (a), then you have increased proliferation risk. If (b), then you're establishing (and presumably militarily enforcing) a two-tier ability to access cheap energy, that favors developed nations.

There are relatively few countries which wanted to develop nuclear weapons over the past ~60 years and were unsuccessful in doing so. I see nothing wrong with banning the export of technology and equipment needed to develop them to those countries (AFAIK: Iran, Iraq & Libya). In fact that is already the case and Israel and US already used/are using military or clandestine means to prevent those countries from developing them. So basically I find it hard to imagine that the situation would be significantly different than it is now.

But lets I assume you're right and 'a' is somehow correct (I don't agree with the premise that increase in global nuclear power generation capacity would somehow automatically result in a higher risk of nuclear weapons actually being used) that would still mean that the western world, Russia, China, India, Pakistan and all other countries in their sphere of influence or aligned to them would have access to cheaper power (which is at least 80-90% of the global population). And I don't consider 'because Iran does not have access to nuclear power then it would be unfair for anyone else to have' to be very good argument.

In fact even if only developed countries had access to nuclear power (which is obviously not fair and not realistic anyway, good luck preventing Russia and China export their reactor to whoever they want) I still think that would be preferably to nobody having it.