Sustaining fusion is very difficult (we really haven’t solved it yet!). Runaway fusion is only really possible if you can simulate stellar conditions, which requires extreme amounts of energy that must be fed in continiously to maintain temperature and confinement. Plus, the radioactive byproducts are much shorter-lived, and so pose much less of a risk of causing lasting ecological damage. Also, just as a FYI, the LHC has not produced any mini black holes or magnetic monopoles. Anything of the sort would be a major accomplishment, far surpassing the discovery of the Higgs Boson.