ok....that is not reassuring news!:(

The major weakness of a BWR and ABWR is its dependence on secondary systems to keep it from melting down. It relies on the correct operation of all of its control rods and the continued circulation of water to keep it from overheating.

If you cut the fuel line to the engine of your car or stop the flow of coolant the engine will simply stop from fuel starvation or overheating. Not so with a nuclear reactor. If the system that is needed to lift the control rods up into the reactor fails for whatever reason or if it becomes physically impossible to move them (i.e. when the core reactor vessel is dislocated in a quake) you are fucked. The reactor will become impossible to stop and the only thing you can do is make sure it doesn't overheat. Of course, this requires the continued, controlled flow of cool water at the bottom and the expulsion of hot steam at the top and the correct operation of the emergency cooling systems. Now, if the ducts needed to carry the water into the core vessel were to shear off from, oh I don't know... an earthquake, the reactor will boil dry and then you're fucked. The reactor will start to accumulate energy and heat up, to the point where the core temperature exceeds the melting temperatures of the metals used to construct the very reactor. Voilà: a meltdown. The core will eventually burn its way through the secondary vessel and the flooring all the way down to the ground the plant is build on. A complete meltdown is comparatively harmless compared to what happens before the the core melts through the secondary containment vessel. No explosions occur and the thing will just sit there glowing when it's done melting its way through to the bedrock.
The only real problem is that there are many tons of water present within the two containment vessels, and if that body of water were to make sudden contact with the hot core the whole building will blow up, throwing tons of radioactive material out into the atmosphere.

The boys at GE did of course try to keep this from happening by creating a donut-shaped containment tank at the bottom of the secondary containment vessel to prevent any water from coming into contact with a core melting its way down. They did however assume that the primary vessel would remain upright and the cooking core would drop through the donut hole in the middle.

You can imagine what will happen when the core vessel is dislocated to the side by a earthquake.

Happy thoughts... happy thoughts...

No Japan nuke power plants have all-day firefighting system

[SIZE="2"]Saturday, July 21, 2007 at 07:38 EDT[/SIZE] [SIZE="2"]From Kyodo via Japan Today
[/SIZE]
TOKYO ― No Japanese nuclear power plants have an all-day firefighting system in which firefighting employees are ready to cope with possible fires throughout the day. The lack of such a system was revealed in reports submitted Friday to the Ministry of Economy, Trade and Industry by 10 major Japanese electric power companies after inspections of their emergency firefighting systems.

The inspections also disclosed that seven of the 10 power utilities have no chemical fire engines at their nuclear power stations. Economy, Trade and Industry Minister Akira Amari ordered 11 nuclear-related power companies earlier in the day to draw up specific measures to strengthen firefighting systems at their nuclear facilities and to report on the steps to the government by next Thursday.

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Meanwhile the Japan Times reports that radioactive material leaked for 3 days after the earthquake because "workers did not follow the manual".

The Asahi calls nuclear workers "inept".

But the government doesn't want the IAEA poking their noses in.

I wonder if/when other countries might start to get concerned by this.

samuraiwig wrote:I wonder if/when other countries might start to get concerned by this.

Like what, North Korea?

Doctor Stop wrote:Like what, North Korea?

Well, it's pretty easy fodder for Kim. And they rarely miss a cheap propaganda trick (like trying to exclude Japan from the 6 nation talks on the grounds they will just do whatever the US says anyway;)).

I meant others nearby, like South Korea and China; countries that do a lot of trade with Japan; countries with large numbers of expats here; members of the IAEA; etc.

Kind of funny that Japan is anti-nuclear weapons but then builds a whole bunch of immobile potential nuclear bombs in their own country...

Make no mistake: Japan can go nuclear in under two weeks if they want to.

Hell, they probably already have a few, in pieces that only need careful assembly before deployment.

Tsuru wrote:Make no mistake: Japan can go nuclear in under two weeks if they want to.

Hell, they probably already have a few, in pieces that only need careful assembly before deployment.

I heard that before. I also heard a report that even if Japan had zero nuclear weapons tech, it would only take them about 15 weeks to develop it from scratch. Every country that ever had sufficient nuclear material and the will to make a bomb has succeeded in detonating one. The jury is still out on Korea.

Thinking of "Japan" and "nuclear" at the same time stimulated a few under-utilized neurons that came up with this:

Missing plutonium

Here's a happy picture from the affected plant:



The Stop Hamaoka site that Doctor Stop links to has popped up here before from time to time but is still very relevant. This article, in particular, is well worth a read.

edit: never mind

Yomiuri: Govt OK's IAEA check of quake-hit nuclear plant

...The government has decided to accept the IAEA offer, as a senior official of the NISA put it, "Because there have apparently been false news reports overseas, which describe the problems at the [Kashiwazaki-Kariwa] plant as being as serious as the Chernobyl disaster [that occurred in 1986 in Ukraine]"...

That explanation doesn't hold water. Even Niigata prefecture were pushing the central government to accept the IAEA offer.

Charles wrote:I".....even if Japan had zero nuclear weapons....".

There have been some interesting stories before about nuclear free Japan and what they may, or may not have!

and the will to make a bomb has succeeded in detonating one

True, but you don't have to detonate the bomb. Just insure (by detonation usually) the trigger works and you have your bomb without scarring people!

Mulboyne wrote:The Onion's view

I just love the survivors pic!

Heise: Japanese seismologist warns of a possible nuclear disaster

Katsuhiko Ishibashi, a professor at the University of Kobe, believes Japan's nuclear power plants are threatened by earthquakes. In an interview with the online edition of the technology magazine Technology Review (German) the seismologist calls attention in particular to the danger that a Maximum Credible Accident (MCA) at the Hamaoka power plant might spread radioactive contamination across the Tokyo metropolitan area. The five nuclear reactors of the plant were situated "right in the middle of a Class 8 earthquake zone," the professor observed. Such an earthquake would be several orders of magnitude larger than the Niigata quake, which in July of this year had damaged the world's largest nuclear power plant at Kashiwazaki-Kariwa, he went on to say. Among experts an earthquake in Hamaoka was thought to be imminent, he stated. "And the capital Tokyo is less than 200 kilometers away. For two thirds of the year the wind blows in that direction," he added.

Mr. Ishibashi was also critical of the standards a nuclear power plant in Japan has to meet to be granted an operating license. "The US standards are a lot more demanding. I don't believe that the territory of Japan is suitable for nuclear power plants." A short time ago the seismologist had still been a member of the nuclear commission of the government responsible for earthquake safety. Mr. Ishibashi had left the commission in protest: "My dissatisfaction with the prevailing standards was not the only reason. I also thought the way discussions were being handled was wrong." Suggestions for improving nuclear safety had been rejected, he declared.