Ukrainian nuclear weapons

[uk 75]

This is not a question of whether Ukraine should or could deploy nuclear weapons but a look at what such weapons would be?

Defensive

The simplest nuclear option would be demolition munitions along the front with Russia. These would resemble weapons deployed during the Cold War.

In a similar Cold War style deployment Ukraine could develop nuclear warheads for its short range missiles and artillery.

Offensive

TEL mounted missiles similar to the SS12 and 23 weapons developed in the Cold War would allow nuclear strikes against Russian military targets outside Ukraine.

A serious minimum nuclear deterrent would require missiles capable of hitting Moscow and St Petersburg.

 

[Scott Kenny]

You forgot nuclear artillery as a possibility, though I suspect that TBMs would be preferable due to range.

The downside of 155-200mm nuclear artillery is the relative inefficiency of the implosion, requiring more fissionables per boom than a larger diameter device. For a nation with little to no in-house fissionables production, you'd want to get the most amount of warheads out of the least amount of fissionables, which means choosing not to build nuclear artillery until you have the fissionables production to make it worthwhile.

 

[UpForce]

Mid-November there was an article in The Times suggesting (based on a conference paper by a think tank) Ukraine could develop a rudimentary nuclear weapon in months. Dr. Jeffrey Lewis (a.k.a. "ArmsControlWonk", commenting on a social media service soon after publication) thought this unlikely, listing a number of reasons but in so doing not omitting possible ways forward.

Ukraine, according to him, is indeed in possession of ~7 tons of reactor Pu, in spent fuel. A further 200 kg becomes available each year. That is plenty for the purpose (hundreds of simple fission weapons, 4 kg minimum).

The US did build a weapon from reactor Pu in 1962 but the yield of such a device, as per Lewis, is uncertain. U.S. Dept. of Energy did, in 1997, state that the minimum would be a few kilotons, probably significantly higher than that (I'm entirely uncertain about the form factor and deliverability of such a device, didn't look into it). However, the ~7 tons of reactor Pu has to be chemically separated from 1,350 tons of high-radioactive spent fuel.

Lewis compares the separation challenge to a recent Chinese example, a new facility capable of processing 50 tons of fuel per annum. This capability cost them about a billion dollars. In 1977 Oak Ridge National Laboratory claimed a more rudimentary plant could become operational in a mere four to six months but the Government Accountability Office stated this wasn't highly probable, save for some circumstances (high risk push, basically, something Ukraine could be viewed as incentivized for). Office of Technology Assessment/Congressional Research Service thought this simple processing capability could be realized in two to three years at a cost of (current) $130M.

Ukraine is currently engaged in a reactor project with Bulgaria and a storage facility build with the U.S, Estonia, Italy, Germany, Netherlands. Integrating a weapons project to all this is questionable and any facility, if somehow found (out) by the enemy, would undoubtedly feature high in their targeting priorities. Therefore Lewis concludes that while it isn't impossible for Ukraine to acquire a national nuclear weapon, it would face complications and be costly. Hope I made his argumentation justice.

While the question here isn't whether Ukraine could or would go forward with this, I believe these limiting factors might inform the discussion on the likeliest type of weapon, i.e. for the near future and primarily a very limited production number of reactor Pu smallish (?) yield fission devices, very optimistically test-ready (IOC being another matter) four months to three years from now.

This of course assuming the project isn't somehow well into way already.

Unsure about the effect a national capability (and its type, should there be timely available options beyond a reactor Pu approach) would have on deterrence for it has worked on multiple levels already and won't be entirely bilateral even in case of Ukraine (publicly) going ahead with this.

 

[Scott Kenny]

The key there of course, is the ability to refine Pu out of spent fuel.

IIRC Ukraine does not currently have such a facility*, and building one would be expensive and obvious.

* Reason they don't is everyone ganging up on them for counter-proliferation reasons. Same reason they don't have a uranium refinery in country.

 

[Foo Fighter]

I beleive that with the dissolution of the USSR, the Ukrainians wrote nuclear weapons out of their constitution and handed what they had to Russia.

 

[zen]

What we cannot avoid is the possibility Ukraine is discussing options with it's close allies. Who may have such facilities.....
And who would see a joint effort as in their collective interests.

Arguably Ukraine and certain neighbours can now see their independence as a tradable commodity in the eyes of the Great Powers.
This tends to be the recipe for why a number of states have driven forward their own nuclear weapons programs.
Fear of betrayal.

 

[BROF]

The 1962 AEC experiment was not a weapon, and did not use LWR reactor Pu (ie separated from LWR spent-fuel, VVER in case of Ukraine). LWR reactor Pu does not lend itself to any meaningful military use, unless burn-up is limited to such an extent, in order to limit Pu-240 fraction, that it would be completely impractical for power generation (what Ukraine needs the most right now), and necessitate rather difficult processing of very large amounts of spent fuel for a very dubious quality Pu anyway.
Things might be somewhat different as regards RBMK SFAs now stored at Chornobyl ISF2, even if contrary to what was claimed in Western countries, RBMK SFAs were never processed to separate Pu, neither in the USSR, nor in Russia nor Ukraine (the USSR had enough supply from dedicated Pu-production reactors).
Anyway, Ukraine is a party to the NPT since 1995 and has a AP in force. Removing SFAs from IAEA safeguards (when IAEA is very much needed at Zaporizhzhia) and starting a programme to separate Pu from SFAs for a military purpose would lead the EU, EUMS and at least the current US administration to terminate immediately their assistance to Kyiv. As for the next US administration, well the NPT is an international treaty under the UN, so perhaps they might disregard such a violation of NPT obligations, but they seem anyway more inclined to let down Ukraine than anything else.
As regards the NWs Ukraine inherited after the dissolution of the USSR in 1992, even if they would still exist under Ukrainian ownership, they and their delivery systems would long have ceased being operational.

 

[UpForce]

A direct quote from Dr. Lewis

Also, Ukraine *could* manufacture nuclear weapon with what's called "reactor Pu" -- although the yield would be uncertain. There are people who refuse to believe this, but the US did it in 1962 and declassified that fact in 1977.

Attached to his post are two (very) grainy images,

one reading: "REACTOR PLUTONIUM AND NUCLEAR EXPLOSIVES", "Robert W. Selden", "Lawrence Livermore Laboratory", "RCEPP Toronto, debate stage hearings, exhibit No. 279, filing date Jan 19/77"

the other: "ALL PLUTONIUM CAN BE USED DIRECTLY IN NUCLEAR EXPLOSIVES", "The concept of "denatured" plutonium - plutonium which is not suitable for explosives - is fallacious.", "A high content of the plutonium 240 is a complication. Given free choice, a designer would likely choose low Pu 240 material."

A commenter (whom I don't know) below Dr. Lewis' post suggested that the Pu used in the '62 experiment was drawn from a British Magnox reactor, not US stock. I don't know and haven't looked further into it. As the discussion here is about the types of (more or less indigenous?) nuclear weapons available to Ukraine, on my part I won't broaden the discussion into how existing treaties might play into their overall considerations on the matter, only how they could directly limit their production/technological possibilities.

This may then inform a more wide ranging weighing of options elsewhere, perhaps without ascribing future reactions to different actors with absolute certainty. In my (current) reading, history doesn't warrant binary options when it comes to nuclear actors and proliferators. Deterrence is by nature empirical and its indeterminate aspects inseparable from the risks it carries. The irony of how Ukraine's commitment to the Budapest Memorandum and/or NPT - to which oblique references have been made here - and trust to its parties was utterly betrayed is not lost on anyone.

"Reactor Pu" was one technological avenue I had seen for Ukraine to even theoretically acquire a nuclear capability in short (enough?) order discussed by an expert in any detail (not that I've scoured for these). Anyway, I would be interested in others as well.

 

[Scott Kenny]

I'm not sure how small a complication the 239/240 ratio is.

IIRC Pu240 is a significant damper in terms of fission. You'd need highly efficient implosion and extra neutron injection.

Edit: I did not remember correctly.

 

[sdmuleman]

I'm not sure how small a complication the 239/240 ratio is.

IIRC Pu240 is a significant damper in terms of fission. You'd need highly efficient implosion and extra neutron injection.

The more significant problem is spontaneous neutron emission causing pre-detonation in simpler weapon designs. It is of some importance in an efficient fission weapon to obtain a very high density of fissile material prior to starting the reaction (much beyond just that for a critical mass), and to start the reaction by injection of a large number of neutrons at exactly the right time. This ensures the maximum degree of fission during the short time while the mass remains dense enough to be critical. Very shortly after fission starts, energy release is sufficient to cause expansion beyond the critical point (more crudely, the reactor literally blows itself apart). Pu-240 has a high enough spontaneous neutron emission rate that it significant increases the chances of initiating the chain reactor too early.

The net result is a low yield - on order of 1 kt for the original fat man design (vs ~20 kt actual).

There's a number of more advanced design features that make this issue less significant - faster implosion, lower pit mass, boosting, etc. However, these have their own complexities.

Higher Pu-240 fractions also makes for more radioactivity and heat generation, both of which make weapon fabrication, storage, etc. more difficult.

So it is true that you can make a functional weapon from reactor grade Pu, but it's not an optimal choice.

More significantly in the context of this thread, reprocessing the spent reactor fuel they may have to extract plutonium and refining this into a usable form is far from a simple or trivial operation, nor one that's feasible in improvised facilities. This is true even with 50's era Soviet attitudes toward worker and environmental safety, and reasonable modern standards for both add another layer of complexity.

 

[Scott Kenny]

More significantly in the context of this thread, reprocessing the spent reactor fuel they may have to extract plutonium and refining this into a usable form is far from a simple or trivial operation, nor one that's feasible in improvised facilities. This is true even with 50's era Soviet attitudes toward worker and environmental safety, and reasonable modern standards for both add another layer of complexity.

Having an existential threat blowing up your country RIGHT NOW tends to make pretty loose standards as regards worker safety.

 

[Mr.T]

I beleive that with the dissolution of the USSR, the Ukrainians wrote nuclear weapons out of their constitution and handed what they had to Russia.

No , US basically went on disarming former soviet states to prevent spread of nuclear weapons to 'rouge' players ,they also hired scientists working on NBC waepons and sustained chem and biolabs for same reason , Ukraine being super broke sold weapons stationed on its soil over which it did not exercise operational control, nuke keys were in Kremlin pre 1991 and post 1991. So in reality Ukraine sold of someone else nuclear waste it could not use or afford to maintain and Chernobil was still fresh on their minds.

US contracted Moscow to process the nukes into fuel for US reactors , 1/5 of which still run on this fuel. Russians also bought or cleared debts with some of Tu-160 while rest of bomber fleets were cut up as were thousands of missiles .Meanwhile worlds arms bazzar opened in Ukraine home to 3rd largest conventional arms arsenal ( soviets left all the gear there) , lord or war and likes operated mainly in Ukraine .Ukrainian arms fueled every 3rd world war you could find.

In any case memorandum was like trust us bro , worthless , non legally binding and US broke it a year or two later by sanctioning Belarus and Ukraine. So anyone pointing to it as some holly grail document is just being stupid. Post 1991 ex soviet union was ripe for pilagining and that is exactly what happened everyone and their aunt went on a pilaging spree , US banksters and economists literally created the oligarchy when they auctioned state assets for peanuts to select elites with no money , wrote Russian Constitution etc...... ran Yeltsin like a pupet.

 

[Foo Fighter]

Just a thought, and aimed at nobody at all, how many 'bots' do we have posting here?

 

[iverson]

Having an existential threat blowing up your country RIGHT NOW tends to make pretty loose standards as regards worker safety.

All isotopes of a given element are chemically identical, if I remember correctly. So the usual ways of purifying a substance aren't applicable. Hence the use of gas-diffusion and centrifuges for Uranium enrichment.

Such things can obviously be done--given enough time and a large enough budget. But both are in short supply in Ukraine's case.

On the other hand, I can easily see Taiwan, Japan, South Korea, and even Poland or Sweden pursuing nuclear weapons if long-established alliances seem unreliable and "nuclear might makes right" becomes a the standard in conflicts between nuclear and non-nuclear powers.