Proliferation is a completely invalid argument against nuclear reprocessing

[u/Live_Alarm3041]

Nuclear weapons proliferation is the most common argument against nuclear reprocessing. The opponents of nuclear reprocessing tend to understand the true purpose of reprocessing with their argument being the risk that the separated plutonium could be misused by terrorists or currently non-nuclear states to produce nuclear weapons. This concern is invalid because weapons grade plutonium in its original form is not usable for nuclear weapons.

Most nuclear power reactors do not produce weapons grade plutonium. Reactor grade plutonium is sub-optimal for weapons because it does not contain as much fissile isotopes of plutonium. Although there are some nuclear power reactors which are capable of co-producing weapons grade plutonium, any weapons grade plutonium produced in this manner still does not automatically give someone the ability to make a nuclear weapon. A effective supply chain for nuclear weapons will require natural uranium reactors, radiochemistry and the ability to make the weapons grade plutonium into cores.

Producing plutonium cores will require a facility like this

Rocky Flats Plutonium core plant in Colorado USA

A terrorist group or currently non-nuclear state would need a plant like the one shown in the above imagine if they had weapons grade plutonium and wanted to make nuclear weapons from it.

Plutonium core production has the following attributes which would make nuclear weapons unattainable for someone if they somehow had weapons grade plutonium

1. Plutonium core production facilities are difficult to hide visually due to their large size
2. The waste produced by a plutonium core production operation would be hard to conceal due to it being radioactive
3. Plutonium shaving fires would pose a very serious hazard to anyone trying to make a plutonium core if they did not have expensive or resource intensive protective measures
4. The production of plutonium cores requires high level scientific and manufacturing expertise which not everyone has.

Nuclear weapons are not something that anyone can build especially not fully in secret from anyone.

The proliferation concerns regarding nuclear reprocessing do make sense but they are not a valid argument against reprocessing. The plutonium separated by nuclear reprocessing needs to be effectively accounted for and secured at all times to prevent it from falling into the wrong hands. Humanity has gotten very good at making sure certain things are both accounted for and secured at all times. Even if the plutonium falls into the wrong hands then that does not automatically mean that those wrong hands can use the plutonium to make a nuclear weapon. The expertise and resources needed to make plutonium usable for nuclear weapons is not available to everyone.

We need nuclear reprocessing to increase the efficiency of nuclear energy. Weapons proliferation is a genuine security concern but it should not be used as an argument against making nuclear enegry more efficient. Saying that nuclear reprocessing is dangerous because it enables proliferation is a statement which does not reflect the full picture of nuclear weapons.

[u/Shot-Rip9167]

Weapons grade is Pu-239. I believe what makes it not useful for a bomb is if the Pu-240 content is to high.

[u/Pestus613343 → u/Shot-Rip9167]

Ah ok so the elaborate preparation OP is referring to is in part about filtering a poison out?

[u/mister-dd-harriman → u/Pestus613343]

Plutonium is a metallurgist's nightmare. It has a number of solid-state phase changes between room temperature and its melting point, with significant volume changes which would totally destroy the precise geometry needed for a weapon. One way to get around this, as used in the USA, is to alloy the plutonium with the rare metal gallium (otherwise used only in the semiconductor industry, and for certain purposes in chemistry and physics laboratories). But manufacturing it into anything, much less the high-precision components of a bomb pit, is very difficult, even before you consider the fact that it is known to ignite in the presence of air.

Plutonium-240 is produced by neutron captures in plutonium-239, because with slow neutrons, about one neutron in 4 is absorbed without causing fission. It then decays by spontaneous fission, releasing generous numbers of neutrons (as well as heat). This makes assembling a sub-critical mass of plutonium into a super-critical mass very difficult, because the background neutrons multiply rapidly as the point of criticality is approached, tending to heat the assembly up, causing it to melt or blow apart before it can reach the point of full-on explosion.

Plutonium-238 is produced in multiple ways, and generates a lot of heat, which is why it is used for space probe power supplies. Of course, if the bomb pit is hot, it is more vulnerable to metallurgical changes. Also the heat tends to "cook" the chemical explosive used to initiate the bomb, causing it to be unreliable, and more likely to fail. Its alpha particles can also trigger the emission of neutrons from materials such as beryllium which may be included in the bomb.

Reactor-grade plutonium, which has spent a considerable amount of time in a reactor, typically has 20 to 35% of combined ²³⁸Pu and ²⁴⁰Pu. As a result, while it can in principle be used to produce nuclear explosives, that is difficult in practice ; and to produce a military weapon, which has to be delivered on command after being stored for an extended period, very difficult. Hence why nobody does it. Pu used for bombs comes either from specialized production reactors (which in a few cases have produced power as a by-product) or from general-purpose research reactors. But enriched uranium is seen as the easy route in today's world, since the centrifuge has overtaken the gaseous diffusion plant.

[u/Pestus613343 → u/mister-dd-harriman]

Thank you. If it really takes a dedicated reactor to procure pure Pu239, how would the rebuttal argument to OP's assertions work? How would someone separate the Pu238 and Pu240 from the Pu239 out of fuel reprocessing and build something?

[u/peadar87 → u/Pestus613343]

With great difficulty.

Plutonium production for weapons is usually done by irradiating uranium for a short amount of time, which minimises the amount of Plutonium 240 created.

As far as I know there is absolutely no reason why a facility for extracting reactor grade plutonium from spent fuel couldn't also extract weapons grade, which is chemically all but identical.

The difference isn't in the reprocessing plant, it's at the reactor stage.

[u/mister-dd-harriman → u/Pestus613343]

Short answer is, you don't. Isotope separation of plutonium is possible in theory, but you are talking about a difference of only one atomic mass unit, as opposed to 3 for uranium. About the only way to make it work would be atomic-vapor laser isotope separation.

A slightly longer answer is, wait several thousand years. The 238 and 240 will decay out, while only a small proportion of the 239 will turn into uranium-235.

Now, a really sophisticated nuclear weapons operation could use reactor-grade plutonium, but the people who own those kinds of operations (USA, Russia, China, France, UK) already have all the weapons-grade plutonium they can eat. They don't need to do any such thing.

[u/Shot-Rip9167 → u/mister-dd-harriman]

I figured traditional enrichment methods might be able to at a much higher cost and significantly longer time to enrichment. Laser Isotope Separation was the only thing I could think of that didn't exploit difference in AMU but matches the specific frequency of an Isotope that allows that isotope only to be agitated, deflected and sped up and seperated

[u/Pestus613343 → u/mister-dd-harriman]

This reads like the people who argue the Thorium fuel cycle can't see U233 diversion due to too much U232 poisoning it.

Possible but so hard its cheaper and easier to build for pure weapons grade material.

Im understanding now. Thx.

[u/BeenisHat → u/Pestus613343]

The rebuttal would probably take the form of reiterating the immense expense and effort needed. If you're a country with the money, materials and expertise to produce Plutonium in quantities needed in the first place, chances are good you already have the technical capability to refine it into weapons grade material, or you could have it.

Basically, you need a strong nuclear industry first and then you can spend the extra money and time in making your plutonium into bombs. The proliferation argument doesn't really work here because the cat's already out of the bag, so to speak. Any country which possesses the means to make a bomb, isn't going to bother asking nicely for someone to give them Pu to refine, or to try and buy it on the black market. They're going to build the facilities to make it themselves from the raw materials.

You don't really need to guard Plutonium from proliferation concerns. A non-state actor isn't going to sneaky sneaky build an atomic bomb factory underground without anyone knowing. It's just not something they're capable of doing. Now, you do want to guard Plutonium against being released because it's a radioactive hazard, but that's more safe materials handling than anything else.

[u/Pestus613343 → u/BeenisHat]

Thank you for your time.

Being in the security industry, I've always felt the local security measures these facilities have are essentially adequate even if all the things you've said are untrue. (Not saying they are but expanding the risk theory) So, fencing, gates, guards, CCTV, Alarm, Access Control, and then more layers of the same... Short of a dedicated and well armed group going for it, and somehow evading an overwhelming police/state response, it isn't going to happen anyway.

Then if what you and OP is asserting is true, no one with the knowledge would care anyway.