[mrguyorama]

As discussed in one of the decommissioning articles someone else posted, it does make the beam dumb radioactive! I hadn't thought about it but it makes sense with how much energy you are pumping into not that many atoms in the end, and when you do that, you tend to get radioactive atoms.

[pfdietz]

The protons that are hitting the dump are at energy far beyond the binding energy of a nucleus. When they hit nuclei there, they shatter them. A shower of progressively less energetic particles forms, including large numbers of newly freed neutrons.

There are accelerator-driven fission reactor ideas that would use ~1 GeV protons (much less energetic than the protons here) to produce neutrons to drive a subcritical target. These might be useful to destroy certain nuclear waste isotopes.

[Sharlin]

Not just any energy but ultrarelativistic protons! That’s going to result in all sorts of interesting daughter nuclei when they slam into the atoms in the buffer.