On the right is the baseball stadium known as Safeco Field in Seattle, USA. It is famous for its retractable roof, which rolls back for sunshine on the rare days in Seattle when there is sunshine.
Why bring this up? Sooner or later, Fukushima must be covered with a roof to prevent radiation leakage to the environment. Having a retractable roof may seem a bit of technology overkill, but I mention it because it allows for the possibility that the roof could be assembled at a distance where radiation is lower, and then rolled on rails over the tops of the buildings.
Based on the Safeco Field experience, I believe that structures like this could be constructed for the four damaged reactor buildings at a total cost of less than half a billion dollars and be ready within six months. In the short term, of course, temporary but faster solutions could be employed.
(True, Cowboys Stadium — site of the 2011 Superbowl — has a bigger retractable roof, but it slides in two rather than sideways. )