A scientific paper published more than 20 years ago was recently rediscovered by the internet:

Sugawara et al. 2003, “Destruction of Nuclear Bombs Using Ultra-High Energy Neutrino Beam”

https://arxiv.org/abs/hep-ph/0305062

A lot of this goes over my little post-Covid head, but the summary seems to be that, theoretically, an advanced high energy collider, similar to but larger and more powerful than the Large Hadron Collider could slam muons into each other and create a laser–like beam of neutrinos. OK, cool. But where I get fuzzy is the discussion of the “mean free path” of the neutrinos. By tinkering with the exact energy of the neutrinos, you can set the MFP to the exact distance from the collider to the target. The beam of neutrinos pass virtually unhindered through the Earth, then, at a fairly specific spot, they create a shower of hadrons. That’s where I’m lost: do the neutrinos suddenly decide “ok, let’s interact with the atoms in dirt right here,” or what, exactly? I’m puzzled.

But in any event, that shower of hadrons *is* perfectly capable of interacting with normal matter, such as the fissile material in a nuclear bomb. In a matter of seconds or minutes, the uranium or plutonium will heat up enough to cause the surrounding high explosives to catch fire or detonate, while messing with the nuclear properties of the warhead itself. They estimate that the bomb will “fizzle” with about 3% the yield it was designed for.

The anti-weapon weapon is hilariously impractical: even with advanced superconducting electromagnets the collider will be on the scale of kilometer in size, costing hundreds of billions. Each shot will require the power output of a nation, and will only target a single nuclear weapon, whose position must be known to just a few feet. And it kinda seems like this vast ring-like structure must be aimed physically. Good luck with *that.*

It seems like “physically possible, engineeringly impractical, financially impossible” project. Something nobody could pull off on Earth. On the other hand, the sci-fi possibilities are clear. Aliens, say, show up. Their scouts check out Earth, realize we’re loaded with troublesome nukes, so their von Neuman bots start carving up the moon. They dig a trench around the moons equator and fill that trench with a vast accelerator… with the reaction chamber pointed right at Earth. A relatively small jiggering of the chamber can aim the resulting neutrino beam to any desired spot on Earth; slight adjustments to the colliders power sets the precise range. Nukes in solos start melting down. Nukes on planes kept in constant motion, however, would likely be safe. Nukes on subs? If they can precisely track submerged boomers, they can probably target them.