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A rogue country that resembles North Korea is trying to activate its new fast breeder reactor, but it turns out it is too fast. They need depleted uranium or thorium to stabilise the reaction. They have some depleted uranium, but not much; since they always used reactors burning natural uranium they never invested a lot in isotope separation.

Over the border there is a demilitarised zone and just across it there is a base manned by soldiers of a great power equipped with depleted uranium ammunition (any reference to existing super powers is a pure "coincidence"). So they send a column of fake tanks in a provocative manner towards that base and get repeatedly shot. Then overnight they send some men to gather the spent projectiles and use the material for their reactor.

Can this work? I don't know how much uranium is contained is a single artillery piece. How many pieces might they need? How much can they provoke them before they start suspecting what is going on?

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  • $\begingroup$ Why would they need depleted uranium? Lead would work just as well (better, in fact) for the purposes of being a neutron barrier. $\endgroup$
    – jdunlop
    Jul 3, 2022 at 17:48
  • $\begingroup$ @jdunlop Thorium and uranium 238 are fertile materials. They absorb a neutron and they become fissile, they absorb another neutron and they undergo fission. During fission they emit back the neutrons, but the net result is zero, in the chain reaction they do not increase the overall number of free neutrons as uranium 235 and plutonium do. But on the other hand they still undergo fission and release energy. $\endgroup$
    – FluidCode
    Jul 3, 2022 at 19:17
  • $\begingroup$ I understand that. But why DU? Natural uranium is 238. Enriched is an increased ratio of 235. They already use natural uranium in their reactors. There's no role for depleted uranium here. $\endgroup$
    – jdunlop
    Jul 3, 2022 at 20:49
  • $\begingroup$ @jdunlop I think you are making a lot of confusion. Natural uranium is uranium 238 with about 0.7% of 235. Natural uranium is usually burned in heavy water or graphite reactors. If I remember correctly North Korea has a graphite reactor. FBR are another beast, they are usually moderated by molten sodium or molten lead (some design may use no moderator at all) and can burn a lot of different fuels, usually plutonium. Adding depleted uranium or thorium to have a slower reaction is a common solution when they happen to be too fast. $\endgroup$
    – FluidCode
    Jul 3, 2022 at 21:12
  • $\begingroup$ That's... what I said? Natural uranium is mostly 238. Enriched has a much increased ratio of 235 to 238. But the natural uranium in a breeder reactor is a blanket that absorbs neutrons. Depleted uranium is just more 238 with less 235, it's not special. So if all you're after is a bigger neutron cross-section, you could add lead or a neutron poison. I've never heard of people using DU in a fast-neutron reactor to "slow it down". $\endgroup$
    – jdunlop
    Jul 3, 2022 at 23:42

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You can use Thorium instead of DU? Problem solved.

All you need is a little chemical and mining expertise to collect tons of Th with little modern infrastructure.

Th usually comes as a byproduct of rare-earths production, but assuming you don't have access to that, you can apply some basic chemical engineering to scale up laboratory methods for extracting Thorium from granite.

Of course, you might find that your good friends that happen to look a lot like China might be willing to share some of their Th reserves from all of the rare earths processing they do. Real-world China has been stockpiling the Th by-products for some time, because they are not insane enough to treat it like horrible nuclear waste, when it is fact barely radioactive with a half-life of 14 billion years - rather they expect it to be valuable as an energy source in the future.

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they send a column of fake tanks in a provocative manner towards that base and get repeatedly shot. Then overnight they send some men to gather the spent projectiles

Real world armies do not operate like NPCs in videogames, where closing one door makes you go from "worst enemy on Earth" to "guy with puppy eyes totally not dangerous". If tanks cross the borders with threatening attitude they will get reaction and that reaction won't stop just when the tanks get neutralized: patrolling and monitoring of the greater area around the trespassing zone and around the border will be more intense for quite some time, there is no way that a group of soldier might go scavenging unnoticed and leave unscathed. Unless it's a very small number, but that the game isn't worth the effort.

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  • $\begingroup$ Yeah, the scavengers are something that I have to sort out. They must be people considered expendable, but if they use dissidents there is the risk that they take the chance and run away. $\endgroup$
    – FluidCode
    Jul 3, 2022 at 15:50
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So I got curious if it were possible to find exact numbers. The short answer is seemingly no. Depleted uranium ammo specs are all apparently at least somewhat classified. Though I was able to find two different numbers that might get you a reasonable estimate. According to this figure, the weight of a 120mm sabot round is 4.6kg. The thing is that we don't know how much of the perpetrator itself is pure depleted uranium. Another figure for the 30mm shells used in the Apache helicopter indicate that it is 75% tungsten and 25% depleted uranium, giving a DU weight of 301 grams and a total shell weight of 1.2 kg. If we then apply the same analysis to tank shells, it would give a minimum of 1.15 kg of depleted uranium.

Having said all of that, this plan it utterly insane as noted by others. While you might be able to clean up shells after a war in a place like Yugoslavia as mentioned earlier, you'll never do so against an alerted enemy. If you really tried sending tanks into a country like South Korea just to provoke a response, they would retaliate far more than just destroying your tanks and then leaving to let you gather the expended ammo.

You need to think about what you would do if you were in charge of the country opposing the one who are developing nuclear weapons and they suddenly did something like this. If you didn't have enough of an excuse to try and bomb their nuclear production just because it existed they just gave you one.

For a couple of useful points about the willingness of the South Korean military to take action, especially at the smaller level, in Operation Paul Bunyon South Korean special forces soldiers actually strapped claymore mines to their own chests and tried to provoke their North Korean counterparts into a response. Meanwhile the Americans brought along an entire battalion of soldiers with tanks and helicopters and had heavy bombers with fighters circling overhead and an aircraft carrier on alert just offshore. And that was all just to cut down a tree that was blocking an observation post after a pair of American officers were killed by their North Korean counterparts while trying to cut it down earlier. South Korea also has a number of conventional strategic ballistic missiles specifically meant as a quick way to respond to a North Korean incursion if needed. They're not just going to destroy a few tanks and then turn around.

Also, if the South Koreans winds up doing most of the heavy lifting, then none of the tank shells fired would be depleted uranium as South Korean shells use tungsten. That's not to mention the fact that any tanks that tried to go South would find that they are running though the most densely packed minefield in the world long before any South Korean or American tanks would ever fire at them.

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Instead, use small amounts of lead.

Lead is just uranium which has fully decayed into a stable form, and it is an effective neutron and radiation inhibitor/blocker. Lead is relatively easy and cheap to source, and would effectively slow down the reaction to a more manageable rate.

As for the option of collecting the enemy's ammunition, I don't think that's feasible. Most ammunition is largely destroyed when it comes into contact with something as rigid as a tank (often in slow-motion videos you can watch bullets shatter like glass), and if it hits the ground instead is usually buried quite deep, making it difficult to access. Besides these factors, an enemy which has a large enough supply of uranium ammo to dump it into a cluster of decoy tanks is going to follow-up the destruction with a full sweep of the area, and then search through the tanks to see if any valuable intel can be gathered. Following that, they will at least be keeping a watchful eye in that area, if not gathering forces for retaliation. This is probably the least safe and effective way to gather such a material.

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  • $\begingroup$ It seems you missed all the comments I exchanged with jdunlop. Depleted uranium is a nuclear fuel, a slow burning nuclear fuel compared to plutonium or uranium 235, but still a fuel. Lead is not a nuclear fuel. $\endgroup$
    – FluidCode
    Jul 6, 2022 at 15:38
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    $\begingroup$ @FluidCode I do see those now, however I don't see how jdunlop was wrong in his comments... it seems that your post needs to be edited for clarification on this, as you wanted something to stabilize the reaction and feasible options were supplied. $\endgroup$
    – Blue Dev
    Jul 6, 2022 at 19:56
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There's a lot of reasons why this is impractical, nearing impossible.

Firstly, as outlined by L.Dutch, you don't get to commit an act of war, and then go back to business as usual. Nothing less would provoke your desired response; the Checkpoint Charlie incident is a great example of being on the absolute brink, with nobody wanting to fire the first shot, because EVERYONE knew what came after.

Second, even such provocation might not even get tanks on the line. Artillery (which does not use DU in its shells), ATGMs, or air power might be used instead of tanks to repel the threat.

Third, even if you get tanks firing at yours, they might not use the "right" ammunition. DU is one of two materials used for APFSDS (Anti-tank penetrator) rounds, the other being Tungsten. DU is generally a better material for the job, but comes with certain...political concerns. APFSDS

Fourth, how, exactly, do you expect to "catch" something going mach 5? The darts do not stay intact when impacting armor, they are destroyed in the process of penetration. You'll need not just tanks to provoke the response, but tanks with some sort of giant "soft armor" on the front that can slow down an AP dart without destroying it.

Edit: Note that an APFSDS penetrator weighs between ~4-10kg, depending on nation, model, generation, etc.

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  • $\begingroup$ A story from the real world: Yugoslavian war. The US forces bomb from above Serbian armoured forces. Since the locals didn't know that the Americans were using DU ammunitions they didn't think about collecting them (even because they were still busy killing themselves) . The fragments of DU ammunitions remained lying there for months if not years until NATO organised a clean up operation and they collected a lot of big chunks. $\endgroup$
    – FluidCode
    Jul 7, 2022 at 16:38
  • $\begingroup$ A 30mm DU shell contains 280g of uranium. I'm not sure what "a lot of big chunks" is supposed to be. "Catching" GAU-8 shells is still not a feasible task, and trying to scavenge shells that impacted "around the target" will put your scavengers back into enemy territory, looking for something that might be a meter underground, or hundreds of meters away from the impact off a ricochet. Finding stuff incidentally over the course of years is not the same as trying to "harvest" spent ammo. $\endgroup$
    – Daniel
    Jul 7, 2022 at 16:52
  • $\begingroup$ "A 30mm DU shell contains 280g of uranium." Thanks. This is part of the information I was looking for. $\endgroup$
    – FluidCode
    Jul 7, 2022 at 16:55

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