Also called spallation. I have seen spallation at the HERMESIII accelerator, but usually with a high-Z target. Not much from Al, plenty from W.
It’s a possibility to get n from high energy photons, but the lower the Z, the smaller the cross section.
I kind of like the suggestion that it was Viking nukes! Or maybe a “natural reactor” like at Gabon that has not been discovered yet.
I like the idea of Viking Nukes! LOL!
I thought spallation was only caused by impact of momentous particles. (That is, not including photons.) You knock a nucleus on the front, and, Newton’s Cradle style, a neutron pops out the back. (Which in any case is different from star formation which completely blows the nucleus apart. )