What is a meltdown?

Japanese officials say that at least 160 people have been exposed to excessive radiation as partial meltdowns occurred at two crippled plants.

CBS News anchor Russ Mitchell reports that officials are concerned that water levels have dropped so much inside two of the reactors that parts of the uranium-filled fuel rods are exposed. In the worst-case scenario, that could contribute to a meltdown.

But what exactly does that mean?

Japan's ambassador to the United States conceded Sunday that part of the fuel rods inside the Fukushima nuclear power plant may be melting - but, he said, the reactor core is not. A big concern is that the water levels inside the reactors has sunk, leaving the uranium-filled fuel rods exposed. A full "meltdown" is, of course, something the Japanese are trying to avoid.

Even two days after they shut down, Fukushima's reactors are still generating heat.

"From the nuclear fuel roads. It's much like if you have an electric stove, and you immediately turn it off, if you put your hand on the stove, you will not be very happy," said Dale Klein, the former chairman of the Nuclear Regulatory Commission.

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Simply put, a "meltdown" is when the nuclear fuel inside the reactor gets so hot, it literally melts. Uranium pellets are inside the long fuel rods. If the reactor is not cooled properly, the tubes can fall apart, with the radioactive material falling to the bottom.

"It's like a car accident -- it can be a fender bender all the way up to a major collision," Klein said. "So when you talk about fuel melting, you can have just a few pellets melt, or you can have a large number of pellets to melt."

The key issue is whether the reactors are being adequately cooled with water. If not, melting could begin.

"When the fuel melts, it will flow like wax into the bottom of the reactor vessel head, and if there's water there, it will solidify and freeze. End of story," Andrew Kadak, a professor of nuclear science at MIT said.

Fears of a radiological release are legitimate, but Kadak says, no one should imagine a mushroom cloud.

"Of course, we're just hypothesizing, the releases will occur when the plant decides to open the reactor containment to relieve the pressure," Kadak said.

Experts say the situation at Fukushima is similar to what happened at the Three Mile Island nuclear plant, in Pennsylvania, in 1979. Kadak recalled that there was a considerable melting of the core, "but essentially all of the material was contained in the concrete containment. Namely, very little of it was released."

Unlike volcano dust, which can be carried long distances by winds, the Nuclear Regulatory Commission says the West Coast of the U.S. is not in danger.

"Even if there were a significant release, it would be dispersed probably before it came to the United States, but at the present time it seems unlikely that there will be a major radioactive release," according to Klein.

"60 Minutes" Rewind: Ten years' worth of "60 Minutes" reporting on the Chernobyl nuclear disaster, health effects on local children, and the "sarcophagus" built to contain the ruined reactor.

[jcwebb82]

I must point out that the image at the very top of the page with the "play video" hotspot portrays a Pressurized Water Reactor, all the plants involved in Japan are Boiling Water Reactors. One key difference between the two technologies -- besides the whole "Boiling" thing -- is that there is a direct connection from the reactor core (and damaged fuel rods) and the steam turbines, condenser, and other items outside the containment shell.

[GreenGestalt]

Can you say "China Syndrome", boys and girls? hehe I knew you could...


Really, the "Spin" is so worthy of Faux NewzSpeak...


Except for (as occured) steam explosions, nuclear plants really can't make nuclear explosions. Nuclear capable material is another matter, they manufacture it...


What we face now is the "China Syndrome" where the nuclear material transmutes into a form of hybrid matter similar to liquid but like high density plasma, where it burns itself to incredible temperatures and melts through the ground. "To China" like old cartoons... Cept it doesn't reach Cathay, it goes about 10 meters or so into the soil, then explodes all over in hyper radioactive steam into the groundwater and ocean and atmosphere depending on local conditions...


In short, radioactive sludge all over...



B-b-but the slick ads produced by Billionaires that suck the government's teat said that nuclear energy is safe and efficient...


It's the most expensive way to boil water yet devised by mankind.
And, IMO, it only exists to justify (power as a by-product) making nuclear material for the reactors "Breed" deadlier materials at their core, like Plutonium. If they weren't set up this way, meltdowns would be nigh impossible. Lots of retired/fired nuclear engineers work out and publish non-breeder reactor designs that can NOT melt down and can NOT make Fission/Fusion bomb usable material, even "Eater" ones that would devour the deadly stuff into less deadly stuff and then be convertible to eat the less deadly stuff.


But the powers that be just want nuclear material for genocide against humanity. They want, like 1984 "Oceana has always been at war with Eurasia"...

[cdrsubkiller1982]

Your deep lack of understnding of the likely outcome in Japan along with randon rants against the "Billionaires (I read anyone who has money and is for more safe nuclear power)" as the root cause of all evil is really sad. You seem to have a grasp of some of the technology but chose to slant it in such a negative and inaccurate way I can only assume you are in some kind of anti-nuclear cult.

Sorry, but we can't stuff the genie back in the bottle.

[eiddam]

It seems with all the catastrophes occuring, and one country has made it known to be number one, the Quake, that produced the Tsunami was deliberatly done by HAARP or such???---Just Food For Thought!

[lungbung]

Fascinating, I always wondered how that process worked. Wow.

www.anon-tools.es.tc

[mitch0927]

Feeble minds say feeble things.

[Demoserver]

Keep it up and see where you end up.

[national1942]

Does it feel like the end of the world is coming??? Are you ready?? Jesus loves you. Turn to Him.

[ellensmithee]

Yippee! The world is ending! Start your sinning now! Now's the time to make pacts with the D#vil!

[Jhihmoac]

"Bless me father, for I have sinned..." Yeah, right...They just tell you, "Get in back of the longest line with the rest of the minions..." SHEESH!

[RedWings_ninety_one]

The final day is set for December 21, 2012

[anzianok]

Not any more than it did during the Inquisition, Black Plague or Holocaust. The only difference today is that telecommunications help us know when disaster is striking somewhere. We're much better equipped to handle disaster than humanity ever has been, so I'd say we're getting farther from the end of the world.