This was discussed in a comment on another post on 2023-01-29. The reaction was unenthusiastic, but perhaps that’s to be expected for innovative technological fixes to problems which it’s more acceptable to lament as insoluble.
Lancing the Earth with a beam weapon to let out deep strata’s heat from natural radioactive decay sounds like a nifty idea to me. And, with a big enough zapper, it works everywhere, not just near tectonic plate boundaries where the the hot stuff is close to the surface.