Related anecdote: I visited the National Ignition Facility [1] last year, where everything was pretty much up and running but they still hadn't finished putting in all the shielding that needs to surround the target chamber before they start actually doing fusion shots. We were assured that if they had done a fusion shot before installing the shielding then everyone in the (extremely large) building would have been dead due to (if I recall correctly) neutron absorption.

Side note: the National Ignition Facility is freaking awesome.

[1] http://en.wikipedia.org/wiki/National_Ignition_Facility