https://arxiv.org/pdf/2501.06623
And I'll include this colourful quote:
"This is orders of magnitude larger than the largest nuclear explosion ever detonated, so this is not to be taken lightly."
I quickly read through and may have missed it but I do not see any mention of the timescale over which this would work just that it could sequester ~30 years worth of CO2 output.
> The long-term effects of global radiation will impact humans and will cause loss of life, but this increased global radiation is “just a drop in the bucket”. Every year, we emit more radiation from coal power plants and we have already detonated over 2000 nuclear devices. Adding one more bomb should have minimal impact on the world.
I don't think "eh, what's one more detonation?" is persuasive when you're talking about a device more than 10x the size of all previous ones put together, being set off in direct contact with the seabed. Most of the fallout from nuclear testing came from the handful of ground burst tests that weren't fully confined, so I'm skeptical that "try to make it a clean fusion design" would actually be enough here. It would be cool if that were solvable though.
Most of fallout in a "regular" nuclear weapon comes from uranium fission by products and from neutrons activating the surrounding materials. In addition, most thermonuclear (fusion) bombs use natural uranium tamper to contain the fusing hydrogen. This tamper soaks up fusion neutrons and fissions, and that actually produces a significant part of the overall yield.
But that's not the only option. It's possible to use a lead tamper instead, so it won't produce any fission byproducts. The Soviet Tsar Bomba did that, and it resulted in the cleanest nuclear explosion on a per-kiloton-basis.
It's also possible to add a boron neutron absorber around the fusion stage to further limit the amount of fusion neutrons that can create dangerous activated materials.
Of course, even a relatively clean weapon is still going to produce plenty of pollution.
Yes, but if the bomb is surrounded by a blanket of boron, it will absorb most of the fusion neutrons. Not _all_, but a significant part of them.
The budget is actually not unreasonable. Fusion warhead scaling is easy, especially if you are not worried about practicalities for combat applications. You just keep on adding bigger stages.
And a boron blanket is literally a boron blanket. You can't do any real engineering for it, it's going to become a highly ionized plasma within the first moments of the explosion, held together only by inertia.
I think in practice going straight to a huge megabomb straight off would not be wise but maybe we could try one of our existing spare nukes as a prototype test? Then you'd get more data on how it would work.