Yeah. I know. I’m a damned alarmist and hysteric when it comes to the Japanese reactor difficulties. It seems I’m not the only one. Michio Kaku describes how things could go if they go bad wrong.

…the worst case scenario is quite different. If radiation levels continue to rise, then at some point the workers may have to evacuate. (A secondary earthquake or pipe break may also aggravate the situation). If the workers abandon the ship, it means that cooling water (which is being shot into the reactors by fire hose) will begin to fall, exposing the rods, and eventually creating 3 simultaneous meltdowns. Then perhaps a steam or hydrogen gas explosion will completely rupture the containment. This will create a nightmare beyond Chernobyl.

Here is a video of Mr. Kaku saying pretty much what he said in the excerpt above:

I’m not optimistic at this point. At all. I expect to see dead zones in Japan by the time the situation is under control.
Dr. Kaku in his latest blog post has some very disturbing news.

The reactor situation in Japan suffered yet another setback today, with water levels in Unit 2 registering 10 million times normal levels. The radiation was so high that workers fled the reactor rather than take a second reading. Radiation levels were an astonishing 1,000 msv/hour (which will cause radiation sickness within an hour and even deaths starting at 6 hours). Given this near-lethal radiation field, workers evacuated Unit 2.
One question is: where did this radiation come from? Most of it was in the form of iodine-134 (with a half-life of 53 minutes) and iodine-131 (with a half life of 8 days). This indicates that the radiation came directly from the core at Unit 2, rather than the spent fuel pond (where most of the iodine has already decayed). So there seems to be a direct path way from the core to the outside, meaning a breach of containment, similar to the situation in Unit 3. In other words, there could be a crack in the pressure vessel surrounding the super hot uranium core, as well as a crack in the outer primary containment vessel surrounding the pressure vessel.

A little math is in order. For ease of calculation let us say that the half-life of I134 is 1 hour and the measurement was made 10 days after the accident started. So let us see 24 hours in a day for 10 days = roughly 240 half lives. Or 1/2240 as much I134 as there was at shutdown. That would mean about 5E-73 as much I134 as there was at shutdown. i.e. basically none. If I134 is detectable the reactor is either not shut down or it is operating in some kind of meltdown mode. Which is to say things are very, very, bad when there are detectable amounts of I134 ten days or more after “shutdown”.
This all fits in well with my discussion Criticality Accident? Unfortunately.
Update: 28 March 2011 0812z
I have been advised that I134 is a daughter product of the decay of Tellurium 134. And the half life of Te134? About 42 minutes. That will not be a steady source of I131 over time. So my analysis stands. We have a criticality accident. Which is very bad news.
Cross Posted at Power and Control