Japan's Prime Minister calls breach at nuclear plant "grave and serious". This means that there is uncontrolled release of radiation into the environment. The gravity of the situation is expected to far exceed the scale of Chernobyl.
According to Dr. Kaku, "If it goes to a full-scale evacuation of all personnel, it means that firefighters are no longer putting water onto the cores. That's the only thing preventing a full-scale meltdown at three reactor sites. Once they evacuate, then we past the point of no return. Meltdowns are inevitable at three reactor sites, leading to a tragedy far beyond that of Chernobyl, creating permanent dead zones in Japan."