Problems at 6 Japanese Nuclear Reactors ... 2 Have Already Likely Melted Down

Early this morning, the Fukushima I nuclear power plant melted down. See this.

Now, MSNBC reports:

A partial meltdown is likely under way at second quake-stricken nuclear reactor [the Fukushima III reactor], Japan's top government spokesman said Sunday.

Fuel
rods were briefly exposed and radiation levels briefly rose above the
legal limit at the nuclear plant where both reactors are located, said
Chief Cabinet Secretary Yukio Edano.

His statement came after
Japan's largest electric utility started releasing steam Sunday at the
second nuclear reactor while trying to stop a meltdown that began a day
earlier in another.

MSNBC also notes
that "the government [is] warning there could be an explosion at a
second reactor [i.e. plant number 3] crippled by Friday's devastating
earthquake."

BBC points out that a meltdown at number 3 could be more serious than number 1, because it uses plutonium as well as uranium:

The plant’s operator says pressure is rising inside reactor No. 3 after it lost its emergency cooling system.

A similar problem led to a blast at the plant’s No. 1 reactor on Saturday. …

But the BBC’s Chris Hogg in Tokyo says the second reactor is a different type which uses MOX (plutonium plus uranium) fuel and the consequences of a problem there are potentially more severe.

Hopefully, the problems at the 4 other troubled Japanese nuclear reactors will be contained.

Many experts have said the disaster is not as bad as Chernobyl. But Forbes' William Pentland notes, nuclear expert Kevin Kamp says:

"Given
the large quantity of irradiated nuclear fuel in the pool, the
radioactivity release could be worse than the Chernobyl nuclear reactor
catastrophe of 25 years ago.”

And the Telegraph writes:

Tokyo,
at least, appeared to have got away without the scale of casualties
seen in other parts of Japan. That was before news of an explosion, and
warnings of a possible "meltdown", at the Fukushima nuclear power
plant. As the evening turned to night, the world's second-largest
metropolis was still waiting to know whether it had been exposed to
what would be perhaps the world's worst nuclear disaster.

Comments

[Rastadamus]

Babylon is falling....

[strannick]

Yea. So we pray for them.

[AN0NYM0US]

GW try this current headline from AP

Japan races to avert multiple nuclear meltdowns

http://www3.wdtn.com/dpps/news/international/nuclear-plant-partial-meltd...

[Mr Lennon Hendrix]

How do they not know how  bad it is?  If it melted down, and the others are likely to too, shouldn't they evacuate the...whole island? 

[falak pema]

Six card flush...bad hand...deadly consequences.

[Bob Sponge]

How to donate for those inclined...

http://news.yahoo.com/s/yblog_newsroom/20110311/wl_yblog_newsroom/japan-earthquake-and-tsunami-how-to-help

[Cindy_Dies_In_T...]

Hi all:

for those who missed it, this is a nuclear guy who taught in the Navy. I found it helpful to put things into context.

http://blogs.scienceforums.net/swansont/archives/8132

’m not an expert on nuclear reactors. I taught in the nuclear power program of the US Navy some years ago, meaning I was competent to discuss some aspects of reactors, and specifically the type the navy uses. So I’m also not some random guy in the street. With that disclaimer in mind, there are a few items to mention with regard to the reactor issues in Japan following the earthquake.

This is not another Chernobyl. The reactor design is very different, and the circumstances are different. The Chernobyl accident (link for the more technically inclined) involved an operating reactor that went prompt critical as the result of operational errors, deliberate disabling of certain safeguards as part of a test, and design flaws. This caused a steam explosion and chemical fires as the carbon moderator caught fire.

A closer analogy would be Three Mile Island.

There have been reports of an explosion, but it must be stressed that this was not a nuclear explosion. The reactors have been shut down. It’s not so easy to cause a nuclear explosion in the first place (bombs require a level of expertise), and a shutdown reactor does not have the capability of sustaining the fission reaction. This leaves us with steam pressure buildup or hydrogen as the most likely culprits, i.e. it’s thermodynamics or chemistry, not nuclear physics, which explains the explosion.

The reactor is shut down, so what’s the danger? The products of a fission reaction are typically radioactive, and subsequent decays also release energy. Shutting down the reactor reduces the fission rate by many orders of magnitude, so it’s effectively zero in terms of heat output, but the radioactive fission products still release up to 6-7% of the plant’s power output. The actual value depends on the operating history; the fission products with long half-lives take longer to build up to steady-state values. This value will drop fairly quickly as the short-lived isotopes decay, but it’s still significant — a reactor rated at 1000 MW will still be producing tens of MW of decay heat. The reactors in question at Fukushima Daiichi are rated at 460 or 784 MW

So shutting down does not mean it’s Miller Time? Right. You need to run pumps and do something with the energy, which usually means piping water to a cooling tower, which means you need to run pumps, and those require electricity. It seems silly, at first glance, that a reactor would need a source of power to run it, but the turbines are probably designed to run at the high power output of the reactor and not off of decay heat. So you have an external power line (lost in the quake), local generators (apparently also damaged) and battery backup. Redundant systems. However, it seems that the damage was severe, so the primary and first backup systems are still offline, and if cooling was lost (batteries have a finite lifetime), the water in the core can boil away.

That sounds bad. Yes. As long as the core stays covered with water, things should be fine. But uncovered, the temperature can rise and fuel elements can begin to melt. Hydrogen is produced, which can explode, and boiling water becomes steam, which raises the pressure in the containment vessel. The latter is why the containment vessel would be vented. You would need to replace that water into the system, which also requires pumps. (This what had happened at TMI, though in that case, the cooling pumps were shut off deliberately owing to a flawed procedure)

So this is serious. Nothing here is meant to imply otherwise. But the term “meltdown” (or worse, if preceded by “Chernobyl-like”) raises all sorts of imagery, most of which is inaccurate.

Here are some links from what look to be credible sources. This is a dynamic situation, so there is a shelf-life to the details

[katsung]

Harassed. So delete the text

[Cindy_Dies_In_T...]

Sky News:

Tim@Sky: 

The Foreign Office say: " The Japanese Meteorological Association announced on 13 March that there is a 70% chance of a magnitude 7 or greater earthquake in the same region as the 9.0 quake within the next 3 days. This may trigger another tsunami and aftershocks of more than magnitude 6.0. "