AHC: Highest number of nuclear-armed states

My thought was just that in a world with a total breakdown of NNPT style controls US/GB/FR would be quite likely to sell/give weapons to most of NATO/other close allies, this would likely be much cheaper than setting up local production and if you are buying the missiles or fighter bombers to deliver them does it matter that you buy in the bomb as well.
 
My thought was just that in a world with a total breakdown of NNPT style controls US/GB/FR would be quite likely to sell/give weapons to most of NATO/other close allies, this would likely be much cheaper than setting up local production and if you are buying the missiles or fighter bombers to deliver them does it matter that you buy in the bomb as well.
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WI Great Britain sold nuclear reactors and nuclear bombs to many British Commonwealth nations and a few colonies. Since comes weapons come with leashes, supply chains and exchange officers, White Hall could still maintain control of most of those nukes.
 

Delta Force

Banned
My thought was just that in a world with a total breakdown of NNPT style controls US/GB/FR would be quite likely to sell/give weapons to most of NATO/other close allies, this would likely be much cheaper than setting up local production and if you are buying the missiles or fighter bombers to deliver them does it matter that you buy in the bomb as well.

Nuclear weapons would still have strings attached even in a world in which they are available for purchase. I don't see the major nuclear powers selling outside of their alliances. Also, they would require maintenence to be performed. The vaunted Iranian F-14 force was rendered impotent due to a lack of qualified maintenence crews and spare parts. The fleet didn't even succumb to anything that remarkable in the early days, some rubber seals were actually the first critical components to fail. Nuclear weapons would likely have similar if not greater issues.

Also, nuclear weapons are remarkably inexpensive and easy to build and maintain compared to other weapons. Nuclear infrastructure and knowledge is widespread, and even simple weapons are among the most powerful weapons ever built. There are less components in a nuclear weapon than a tank or fighter jet too. South Africa ran its program for $400 million out of a machine shop and completed six nuclear weapons and parts for a seventh. That's less than most conventional weapons development and/or procurement programs.
 
A simple program could be based around reprocessing plutonium from a relatively small reactor, but a more advanced program needs uranium and tritium (used in thermonuclear weapons). Uranium requires extensive energy resources to operate the enrichment facilities (traditionally near gigawatts of hydropower, coal, or nuclear capacity), and tritium is best produced in heavy water reactors. Heavy water reactors need heavy water (an isotope extracted from regular water), which tends to be produced at large hydroelectric facilities due to the energy and water requirements.

Tritium is made on the large-scale by fissioning Li-6. There is no special requirement for a heavy water reactor. HEU can also be substituted to a degree with Pu-239 in thermonuclear weapons though it's lower critical mass complicates design.

The largest bottleneck is acquiring weapons grade material, either plutonium or highly enriched uranium. HEU is probably more difficult to acquire due to the need for enrichment facilities of some kind, traditionally gaseous diffusion although more recently centrifuges. Plutonium can be acquired by reprocessing spent nuclear fuel.

Long burnup times which are standard across the board for power reactors means that the Pu-239 from such a route is heavily contaminated with Pu-240. As a short-lived alpha emitter it produces considerable heat which seriously complicates weapon design.

The easiest plutonium pathway is using a gas cooled reactor, which can use natural uranium and common gases such as carbon dioxide, although it isn't as good at making tritium.

Gas cooled reactors are an awful route for making weapons.

The low thermal capacity of nearly all gases forces you to highly pressurise the gases and run your reactor at very high temperatures. High pressures in tun mean you need a heavily constructed reactor vessel and complicates on-line loading and unloading of the reactor.

Heavy water is the ideal, since it is the best for tritium, but while it can use natural uranium it requires heavy water.

Heavy water makes up one of the largest capital costs in building a CANDU reactor.

Light water doesn't really excel at weapons production, since it needs low enriched fuel and doesn't excel at tritium production, but it's a good option for naval propulsion and commercial programs and thus the most common type of reactor in general use.

Light-water moderated reactors don't accel at weapons production because they require enriched fuel.

Gas cooling was a common option when nuclear energy started (the first commercial power reactors were gas cooled units in the United Kingdom) and it could make a comeback in the future due to its high efficiency and high output temperatures (waste heat has potential industrial and heating uses), but it's currently not commercially available and the most advanced commercial plants (British Advanced Gas Cooled Reactors) are 1960s/1970s technology.

Gas cooling was only really common in the UK in the early years of nuclear power. Not because it was good, but rather pure nationalistic spite as not to be seen copying the Americans.

At high temperatures, gas cooling has nearly all the same drawbacks as water cooling; it operates at very high pressures and the gasses are poor thermal conductors.

The answer is thus that it depends. A simple program just needs a small reactor and reprocessing capabilities, but a large and/or advanced one would really benefit from access to large hydroelectric facilities to help run enrichment plants (nuclear can take over later) and provide heavy water.

If you want nuclear weapon material you'd go as simple and as low cost as possible. That means light-water cooled, carbon moderated and natural uranium fueled, running at atmospheric pressure and potentially even open pooled style for easy fuel swapping. You could easily insert tubes filled with either natural lithium or Li-6 into the reactor to produce large quantities of tritium.
 

Delta Force

Banned
Tritium is made on the large-scale by fissioning Li-6. There is no special requirement for a heavy water reactor. HEU can also be substituted to a degree with Pu-239 in thermonuclear weapons though it's lower critical mass complicates design.

Heavy water reactors produce around twenty times as much tritium per energy output as other types of reactors, so while there isn't a requirement for them it's the best way to optimize output. More information in Table 2 on page 221 of this book and page 13 of this document.

Long burnup times which are standard across the board for power reactors means that the Pu-239 from such a route is heavily contaminated with Pu-240. As a short-lived alpha emitter it produces considerable heat which seriously complicates weapon design.
I forgot about that. Unless the reactor is going to constantly go through loading and offloading cycles, the best way to counteract that is with an online refueling system, so the fuel can be taken in and out as required. That means separate fuel tubes too. I don't know if online refueling is possible for a PWR, but it has been done with BWR reactors, and it's common on heavy water and gas cooled designs.

Gas cooled reactors are an awful route for making weapons.

The low thermal capacity of nearly all gases forces you to highly pressurise the gases and run your reactor at very high temperatures. High pressures in tun mean you need a heavily constructed reactor vessel and complicates on-line loading and unloading of the reactor.
Actually, the later series Magnox reactors and all the Advanced Gas Cooled reactors were built with steel reinforced concrete rather than pressure vessels. They don't require complicated equipment to build and are even considered safer than steel vessels.

Heavy water makes up one of the largest capital costs in building a CANDU reactor.
Well, I certainly didn't say it was cheap.

Light-water moderated reactors don't accel at weapons production because they require enriched fuel.
That would seem to be an important caveat. Usually light water is both coolant and moderator, but the RBMK was a water cooled graphite moderated design that seemed to have some features that could lend themselves to weapons production, notably the online refueling capabilities/fuel tubes.

Gas cooling was only really common in the UK in the early years of nuclear power. Not because it was good, but rather pure nationalistic spite as not to be seen copying the Americans.

At high temperatures, gas cooling has nearly all the same drawbacks as water cooling; it operates at very high pressures and the gasses are poor thermal conductors.
It's important to distinguish between the early gas cooled designs in current use and some of the later ones that were tested and that are proposed for future use. The British and French lacked heavy water for heavy water reactors and didn't have much electricity to spare during their economic recovery for light water, so enrichment wasn't a feasible option either. Gas cooling was thus a second best option, as they would only require natural uranium and could reprocess the spent fuel for plutonium. Without the need for extensive enrichment capabilities the military program could supply more electricity to the grid as well.

As you point out, these early gas cooled designs had lower efficiency than even the light water designs. Carbon dioxide isn't the best gas for a nuclear reactor from an efficiency and maintenance point of view, but it's easy to acquire. In addition to that issue, the early gas cooled reactors were Rankine cycle/steam turbine units, so they lost further efficiency by transferring the energy in the gas to water. The water cooled reactors can do that directly.

However, in terms of advanced reactors, a gas cooled design using helium cooling can achieve very high temperatures (hence their name very high temperature reactors) and use the helium to directly drive Brayton cycle gas turbines, a technology first used in natural gas power plants in the 1960s and now very well refined. It's possible to get similar levels of efficiency from steam, but that requires using supercritical steam technology that has only been used in a few coal fired power plants and poses additional challenges for a nuclear unit given the need for higher safety standards.

If you want nuclear weapon material you'd go as simple and as low cost as possible. That means light-water cooled, carbon moderated and natural uranium fueled, running at atmospheric pressure and potentially even open pooled style for easy fuel swapping. You could easily insert tubes filled with either natural lithium or Li-6 into the reactor to produce large quantities of tritium.
The RBMK is supposed to have been a very inexpensive design, so this seems like a possible option as well. I'm only aware with it being used for the RBMK though, so I'm not sure what issues are tied to the technology as opposed to that specific design. Also, it doesn't really explain why other countries went for gas cooling to fill the same role in their early nuclear programs, and my guess for that is the technology probably has low efficiency.
 
Heavy water reactors produce around twenty times as much tritium per energy output as other types of reactors, so while there isn't a requirement for them it's the best way to optimize output. More information in Table 2 on page 221 of this book and page 13 of this document.

Tritium is an unintentional byproduct. Reactors loaded up with Lithium (of any moderation type) produce far more tritium than any heavy water reactor without the incredible expense of heavy water and the incredible expense of separating it (remember, tritium is an isotope of hydrogen complicated extraction)

I forgot about that. Unless the reactor is going to constantly go through loading and offloading cycles, the best way to counteract that is with an online refueling system, so the fuel can be taken in and out as required. That means separate fuel tubes too. I don't know if online refueling is possible for a PWR, but it has been done with BWR reactors, and it's common on heavy water and gas cooled designs.

And seriously increases design complexity along with expense.

Actually, the later series Magnox reactors and all the Advanced Gas Cooled reactors were built with steel reinforced concrete rather than pressure vessels. They don't require complicated equipment to build and are even considered safer than steel vessels.

After the RBMK series, the Maxgnox reactor was probably the most poorly thought-out reactor design in history. Seriously, who designs a reactor and then calls it "MAGnesium, Non-OXidising" leading to the fuel-rods oxidizing in long-term storage because they were madde of magnesium.

Well, I certainly didn't say it was cheap.

Expensive and completely unnecessary for what you're trying to achieve.

That would seem to be an important caveat. Usually light water is both coolant and moderator, but the RBMK was a water cooled graphite moderated design that seemed to have some features that could lend themselves to weapons production, notably the online refueling capabilities/fuel tubes.

When I suggested light-water cooled but something else moderated I was referring to the type of reactor used by the US in weapons materiel manufacture; a light-water cooled, graphite moderated series of reactor used at the Hanford site.

It's important to distinguish between the early gas cooled designs in current use and some of the later ones that were tested and that are proposed for future use. The British and French lacked heavy water for heavy water reactors and didn't have much electricity to spare during their economic recovery for light water, so enrichment wasn't a feasible option either. Gas cooling was thus a second best option, as they would only require natural uranium and could reprocess the spent fuel for plutonium. Without the need for extensive enrichment capabilities the military program could supply more electricity to the grid as well.

As you point out, these early gas cooled designs had lower efficiency than even the light water designs. Carbon dioxide isn't the best gas for a nuclear reactor from an efficiency and maintenance point of view, but it's easy to acquire. In addition to that issue, the early gas cooled reactors were Rankine cycle/steam turbine units, so they lost further efficiency by transferring the energy in the gas to water. The water cooled reactors can do that directly.

However, in terms of advanced reactors, a gas cooled design using helium cooling can achieve very high temperatures (hence their name very high temperature reactors) and use the helium to directly drive Brayton cycle gas turbines, a technology first used in natural gas power plants in the 1960s and now very well refined. It's possible to get similar levels of efficiency from steam, but that requires using supercritical steam technology that has only been used in a few coal fired power plants and poses additional challenges for a nuclear unit given the need for higher safety standards.

Not really relevant to making weapons. They're all far more complicated than required for weapons.

The RBMK is supposed to have been a very inexpensive design, so this seems like a possible option as well. I'm only aware with it being used for the RBMK though, so I'm not sure what issues are tied to the technology as opposed to that specific design. Also, it doesn't really explain why other countries went for gas cooling to fill the same role in their early nuclear programs, and my guess for that is the technology probably has low efficiency.

Again, the RMBK was also a power reactor. If you just want the bomb then your really shouldn't bother with the expense and hassle of integrating pressure systems and and other associated system into your reactor.

The only people I can think of that went for gas-cooling were the British and the French. They chose it because they wanted dual-use nuclear reactors that could have produced power and weapon's material. If they had just wanted weapon's material it would have been wiser to just build a large open-pool reactor running at atmospheric pressure.
 
(snip)

You just showed the reason that others might need/want nuclear weapons. The USA becomes isolationist again, and European nations, secure behind their nuclear forces, simply concern themselves with domestic affairs and insuring that they can trade freely for oil. (And their nukes are sufficient to tell the USSR, "You can invade if you want to--but MAD is in effect..."

In short, areas of the world that the USA doesn't care to defend, and that don't want someone else marching in, may want them.

The problem is that after WW2 the US has a series of international responsibilities it simply cannot give up, even if an isolationist government came to power. Japan and West-Germany are under American occupation after WW2 and even after they are granted nominal independence large American armies are stationed on their territory, I cannot see any post-war American government willing to up and leave these countries that so recently were a substantial threat to US security and allow them to become powerful puppet states of the USSR. Certainly reduced global involvement of the US in international affairs (maybe no formal Western Bloc/NATO?) would open the door for more countries around the world to increase their own military forces, since they would not be able to depend on the US for defense, but many of the countries with the greatest capability to become nuclear powers in a short period of time (but aren't nuclear powers in OTL) are ones the US cannot simply abandon on the international stage for purely self-interested reasons (eg. occupied Japan, West Germany).

Post war Australia would be an interesting option, it certainly has the uranium for nuclear program, although the small population post ww2 might make actually developing a nuclear program a problem, although an interesting possibility would be them becoming major partners with the British in their nuclear program in the 1950s and hence sharing the resultant "Blue Streak" weapons. I don't really know much about US/Australia historical relations, but how feasible would it have been for the US to have withdrawn itself from its responsibility to defend Australia post-WW2 (I know there was a large American presence in Australia during WW2). Maybe an American or an Aussie on this board can offer some insight?

As other people have noted their is the potential for other countries that don't really have the resources/technical know-how to become nuclear powers due to weapon sharing with a P5 nuclear power. This works in theory, but I have to wonder, just how many states would countries like the US and USSR be willing to arm with technologies that could be turned against them, even nominal allies. A good OTL example of this would be North Korea, which although it is a nominal ally of China, I sincerely doubt the Chinese government is comfortable with the North Koreans developing medium-range nuclear ballistic missiles. The politics of nuclear weapons sharing in a world without the non-proliferation treaty would certainly be an interesting topic to explore.

Of note, the US is obligated to defend Canada with a nuclear shield whether it is isolationist or not for practical reasons as any enemy incursion to Canada would strongly undermine the American defensive position. This is why in OTL Roosevelt made a speech in 1939 that if Germany attempted an invasion of Canada it would face a declaration of war from the US (see the Kingston Address). It would be very hard to manufacture a situation where Canada is unable to rely on American weapons (including nuclear) for its defense and thus generate a need for its own program (which even then would probably consist of buying technologies from the US like the UK in OTL).

PS: I am not going to weigh in on the technical details of nuclear weapons creation and maintenance, as I fully admit that I am not a nuclear physics expert and any info I would add to that debate would simply be drawn from internet searches
 
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