In a previous post on the Japanese reactor problems I noted
Hydrogen explosions indicate a very serious problem. There should be no hydrogen generated under normal conditions. Or abnormal conditions. The situation must be very abnormal.And the serious problem I feared appears to have happened. A breech of the fuel rods, the reactor vessel, and the containment building.
There appears to be signs of a core "meltdown".
SOMA, Japan – Japan's nuclear crisis deepened dramatically Tuesday. As safety officials sought desperately to avert catastrophe, the government said radioactive material leaking from reactors was enough to "impact human health" and the risk of more leaks was "very high."This is not good at all. If the shutdown and post shutdown cooling had gone well the reactors should have been past the peak of the danger zone by now.
In a nationally televised statement, Prime Minister Naoto Kan said that radiation has spread from four reactors of the Fukushima Dai-ichi nuclear plant in Fukushima province that was one of the hardest-hit in Friday's 9.0-magnitude earthquake and the ensuing tsunami.
He urged anyone within 19 miles (30 kilometers) of the plant to stay indoors or risk getting radiation sickness.
Sky News has more details.
A third explosion has been heard at a quake-stricken Japanese nuclear power plant, raising fears of a nuclear meltdown.It has been a long time since I studied this but as I recall the only time you would see a large release of hydrogen gas from a shut down reactor is if the fuel rods were at a very high temperature thus making it possible to use the water available as an oxidizer thus releasing hydrogen. This is some very bad news. Very very bad. Thus these accidents will be studied for years to come. I'm going to go out on a limb here and say that compared to Three Mile Island these plants are very poorly designed. It may have something to do with the military heritage of the US plants.
The blast tore through the unit 2 structure at the Fukushima Daiichi complex and a hole has been found in the container.
Japanese cabinet secretary Yukio Edano has told a press conference there is also currently a fire in unit 4 reactor.
Prime minister Naoto Kan said radiation has spread from the reactors and that anyone living less than 20km away from the facility should leave the area.
He said that those within the 20 to 30km radius should stay inside as the risk of a nuclear leak is rising.
Mr Edano said efforts are being made to cool down all of the reactors using water injection but that radiation levels could affect people's health.
Two previous explosions occurred in buildings housing unit 1 and 3 reactors following last Friday's massive earthquake and tsunami.
Update: 15 March 2011 1331z
It appears there are quite a few of these GE designed reactors in the US.
On Monday, GE Hitachi Nuclear sent the following statement, in full: "The BWR Mark 1 reactor is the industry’s workhorse with a proven track record of safety and reliability for more than 40 years. Today, there are 32 BWR Mark 1 reactors operating as designed worldwide. There has never been a breach of a Mark 1 containment system.""Never been a breach"? They may have to revise that statement in the very near future.
The six reactors at the Fukushima Dai-ichi power plant, which had explosions on Saturday and Monday, are all GE-designed boiling-water reactors, known in the industry as BWRs. Five have containment systems of GE's Mark I design, and the sixth is of the Mark II type. They were placed in operation between 1971 and 1979.
A fact sheet from the anti-nuclear advocacy group Nuclear Information and Resource Service contends that the Mark I design has design problems, and that in 1972 an Atomic Energy Commission member, Dr. Stephen Hanuaer, recommended that this type of system be discontinued.
I go back and forth on the nuclear power question a lot. In the past few years I have been swinging towards - nuclear power is OK until we get something better. May be not though. Maybe the pressures on civilians (profits) is not commensurate with the requirements of plant safety. One clue is that the US Government insures the nuclear industry in America. It also regulates the industry. So there is some confluence of interest there.
We won't know anything for sure until the fires die down and the smoke clears.
Update: 15 March 2011 1411z
The weakness of the boiling water plants has been known for some time.
However, as early as 1972, Dr. Stephen Hanuaer, an Atomic Energy Commission safety official, recommended that the pressure suppression system be discontinued and any further designs not be accepted for construction permits. Shortly thereafter, three General Electric nuclear engineers publicly resigned their prestigious positions citing dangerous shortcomings in the GE design.Wow. But that does explain the tall "towers" near the plants. They are there to "spread the radiation around" in case of an accident. Which is not a bad idea. If there is not too much of it.
An NRC analysis of the potential failure of the Mark I under accident conditions concluded in a 1985 report that Mark I failure within the first few hours following core melt would appear rather likely."
In 1986, Harold Denton, then the NRC's top safety official, told an industry trade group that the "Mark I containment, especially being smaller with lower design pressure, in spite of the suppression pool, if you look at the WASH 1400 safety study, you'll find something like a 90% probability of that containment failing." In order to protect the Mark I containment from a total rupture it was determined necessary to vent any high pressure buildup. As a result, an industry workgroup designed and installed the "direct torus vent system" at all Mark I reactors. Operated from the control room, the vent is a reinforced pipe installed in the torus and designed to release radioactive high pressure steam generated in a severe accident by allowing the unfiltered release directly to the atmosphere through the 300 foot vent stack. Reactor operators now have the option by direct action to expose the public and the environment to unknown amounts of harmful radiation in order to "save containment."
But it is bad design IMO to design a containment failure into the system. What if it fails? You have a designed in breach. Idiots.
Cross Posted at Classical Values