In this paper:
http://wwwphy.princeton.edu/mumu/target/King/king_WEBR6_pac99.pdf "Potential Hazards from Neutrino Radiation at MUON Colliders"
High energy muon colliders, such as the TeV-scale conceptual designs now being considered, are found to produce enough high energy neutrinos to constitute a potentially serious off-site radiation hazard in the neighbourhood of the accelerator site. A general characterization of this radiation hazard is given, followed by an order-of-magnitude calculation for the off-site annual radiation dose and a discussion of accelerator design and site selection strategies to minimize the radiation hazard.
It suggests "muon colliders" could produce neutrino beams powerful enough to pose a potentially dangerous radiation hazard, but I don't recall it going into the details of why the danger existed. How is that possible? Neutrinos are not usually very interactive, and the only other time I heard of "deadly neutrinos" was in regard to a supernova explosion, where if you were within 1 AU, it would be enough to be deadly, but if you were within 1 AU, you would be inside the stellar envelope anyways, and thus the neutrinos would be the last thing you'd be concerned about. I can't possibly imagine that a man-made source could come anywhere close to the power of a supernova, much less in emitted neutrinos.
The only thing I can think of is that, apparently, as the neutrino energy increases, they become more interactive, and the muon collider would be generating neutrinos with per-particle energies far in excess of those produced by a supernova. Thus while the total neutrino areal energy density would be nothing compared to that in a supernova, the much higher per-particle energy would dramatically boost the interactivity. Is this the correct explanation?