3 Japan nuclear reactors had full meltdown, agency says (full?)

Until the plants are in cold-shutdown, and until someone puts a scope inside each reactor vessel, it is pure speculation regarding total melt and pure speculation regarding reactor pressure vessel failure. That includes pure speculation by the managers and the PR team feeding the journalistic frenzy around this story.

Fuel cladding melts at a much lower temperature than the ceramic UO2. The effects being reported can result from fuel pellets scattered about the pipe systems.

At TMI-2, fuel pellets and fuel fragments were found in the emergency core cooling (ECCS) pipe systems that circulated the water coolant. At TMI-2, the pictures taken inside the vessel showed the pellets laying in the lower half of the core region (above the support plate) like rubble. At a BWR, reactor coolant and steam produced by the reactor is in the reactor building, auxiliary building, and turbine building. It should be no surprise that the ceramic fuel pellets are in all three buildings, with only one designed to mitigate the radiation from an accident.

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