The Japanese can’t catch a break at the Fukushia Daiichi plant:

Technicians are battling to stabilise a third reactor at a quake-stricken Japanese nuclear plant, after it was rocked by a second blast in three days.

The Fukushima Daiichi plant’s operators said they could not rule out a fuel rod meltdown, after a cooling system broke.

They are injecting seawater into reactor 2 after its fuel rods became almost fully exposed.

This came after another explosion of built-up hydrogen, one predicted by the plant operators, that injured 11 people but only one seriously.  The containment remained intact, but the cooling system failure means that they will have to scrap yet another reactor in an attempt to safely end the nuclear reaction and avoid a meltdown.

The US moved one of its carriers after higher levels of radiation were detected 100 miles off the shore in the vicinity of the plant, but as North Shore Journal notes, the danger was not terribly significant (via Instapundit):

For per­spec­tive, the max­i­mum poten­tial radi­a­tion dose received by any ship’s force per­son­nel aboard the ship when it passed through the area was less than the radi­a­tion expo­sure received from about one month of expo­sure to nat­ural back­ground radi­a­tion from sources such as rocks, soil, and the sun.

Still, if that’s the dose received 100 miles away after wind dispersal and dissipation, it’s small wonder that the Japanese are evacuating the area near the plant.  No nation has the history of radiation poisoning that Japan does, and one has to believe that this danger will loom the largest among the people even after the tsunami damage that killed thousands of people.  The government will face a great deal of scrutiny for years to come for its actions in these few days, and they appear to understand that.

At CNN, Jim Walsh explains the problems with dumping seawater into a hot reactor and why the venting will create a long-term problem for Japan:

The likelihood of an explosive meltdown a la Chernobyl seems remote, in other words, but that doesn’t mean that Japan won’t have significant levels of environmental contamination. Walsh notes that the set of circumstances facing Fukushima Daiichi wouldn’t get replicated in the US because the US wouldn’t get hit with an 8.9 quake nearby one of our nuclear reactors, although we do have an operating nuclear power station in San Onofre, California, one designed to use seawater as a coolant. Any new reactors would almost certainly use a much different design — most likely the pebble-bed reactors that would eliminate almost entirely the risks associated with the Fukushima Daiichi type of reactor as we see now.