Chris Busby is calling for sealing off the Fukushima reactors, since they are still releasing huge amounts of radionuclides. Cost is no object. I would say that the whole site needs to be entombed, since steam and smoke are coming out of fissures in the ground. Also a boronated concrete barrier needs to be built underground, to stop the leakage of corium into the groundwater and the sea.
Busby has also done tests on an air-conditioning filter in a Tokyo apartment (here and here), and has found huge amounts of cesium and uranium in it. Where there is uranium, there is plutonium too. These radionuclides are incredibly toxic.