Is Worse Yet to Come in the Fukushima Nuclear Disaster?

[FourScore]

Fire at Fourth Reactor: Is Worse Yet to Come in the Fukushima Nuclear Disaster?
By Simon Shuster Tuesday, Mar. 15, 2011

...The nightmare scenario, however, would unfold if rescue workers fail in their frantic attempts to cool the fuel rods, as they've been trying to do for several days. "The likelihood is low but it still exists," Savin says. "If one reactor has a full meltdown, and you reach a critical mass of melted nuclear fuel built up inside the reactor, it could cause an atomic explosion." Other experts say they wouldn't use the word "explosion" for such an incident. Says Alexander Uvarov, the editor of Atominfo, a Russian online journal on the nuclear industry: "I wouldn't personally use that phrase, simply because in the public mind that phrase evokes the image of Hiroshima. But yes, it is an explosion, or perhaps more like a very large burst."

Such a blast would certainly not have nearly as much force as an atom bomb, Savin agrees, but it would pump a large radioactive cloud into the atmosphere that could then be carried by the wind. "That's when the situation would start to look a lot more like Chernobyl for many years to come." Adds Uvarov: "The best way to prevent that is by covering the fuel with a thick layer of water, as they've been trying to do . Of course that water will continue to steam away from the super-hot fuel, but if the layer is thick enough you would not have that explosion." But, he adds, "if the melted fuel does gather inside the reactor and is exposed to the air, it could indeed explode, and that would spray all kinds of nasty particles into the atmosphere." (See "Fukushima: Chernobyl Redux?")...

SNIP

"...There is the sense that the Japanese were either unprepared or had serious flaws in their contingency plans," says Uvarov. "There has not been full disclosure about the situation there. Of course I can understand the desire to contain panic, and to save the ugly details for a better time. But that leaves experts to draw conclusions from available facts, which are so far not encouraging."

At the very least, the facts suggest that a quarter century after Chernobyl, the world has still not immunized itself from the threat of such disasters. They are the price the world inevitably pays for nuclear energy, and now it is Japan's tragic turn to foot the bill. The total cost — in human lives, sickness and environmental devastation — will only become fully clear years from now, once the fallout from Fukushima runs its course.

Read more: http://www.time.com/time/world/article/0,8599,2059232,00.html#ixzz1GmSzYon3

[BeFree]

1. Sure Hope Not

Hope is that Change will happen and it all just settles down.

[dkofos]

2. YES This will not be over for months, and it will get worse.

[Statistical]

3. I hate it when people are sloppy with words ...

"one reactor has a full meltdown, and you reach a critical mass of melted nuclear fuel built up inside the reactor, it could cause an atomic explosion"

A critical mass can't cause a nuclear detonation. It requires a super critical mass. If a critical mass formed in the reactor it would get very very very very hot very fast. That would result in a massive pressure spike which would rupture the reactor. The heat increase would produce hydrogen and you could have another CONVENTIONAL hydrogen explosion. That would propel nuclear material high into the atmosphere. Basically a worse case scenario and a disaster on the scope of Chernobyl.

Calling that a nuclear explosion is fear mongering. 99% of people reading nuclear explosion that will think.


A nuclear detonation requires a super critical mass. Something that can't be formed in a reactor and can't be created with reactor grade fuel (low enriched uranium). Creating a super critical mass requires an implosion device to compress the nuclear material (thus increase its density and criticality) very quickly (as in hundreths of a second).

Even in a nuclear weapon if done "too slow" a critical not supercritical chain reaction will occur and the heat, stress, and pressure will push the material apart before it can go supercritical.

[villager]

4. so it would "merely" be like a vastly effective "dirty bomb" then ...

Not sure that's exactly "comforting," however...

[Statistical]

6. Not very comforting. Chernobyl wasn't comforting.

However it wasn't a nuclear detonation and it would have the massive shock wave and fireball that a nuclear detonation would create. It wouldn't instantly kill everyone within miles of ground zero and create hurricane force winds.

[bananas]

14. Wrong - there was a nuclear explosion at Chernobyl equivalent to a small tactical nuke

http://en.wikipedia.org/wiki/Chernobyl_disaster

A second, more powerful explosion occurred about two or three seconds after the first; evidence indicates that the second explosion resulted from a nuclear excursion.
...
However, the ratio of xenon radioisotopes released during the event provides compelling evidence that the second explosion was a nuclear power transient. This nuclear transient released ~0.01 kiloton of TNT equivalent (40 GJ) of energy; the analysis indicates that the nuclear excursion was limited to a small portion of the core.

0.01 kiloton = 10 ton, which is equivalent to a small tactical nuke:

http://en.wikipedia.org/wiki/Davy_Crockett_%28nuclear_device%29

The M-388 round used a version of the W54 warhead, a very small sub-kiloton fission device. The Mk-54 weighed about 51 lb (23 kg), with a selectable yield equivalent to 10 or 20 tons of TNT (very close to the minimum practical size and yield for a fission warhead).

[Name removed]

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[villager]

20. Ineffective?

:shrug:

[snappyturtle]

5. If they could successfully keep water where it's needed, I think we

could have some hope. However, it appears the efforts are similaar to pourinng water into a sieve and even then,, I just read, the military, given the task to dump water on reactor 3, can't and was called off in fear of the high radiation in the steam arising from it. In the end, I think the 'end' of the situation will culminate rather quickly now.

[Kablooie]

7. Does anyone know how long it takes for the fuel to cool to a safe level?

Is it days? Years?

[nadinbrzezinski]

9. No lonnger a hazard a few thousand

to where it is can be re-roofed and ignored a few hundred.

By hot means not temp, but radiation

[Statistical]

12. About 5 years to be cool enough for dry cask. Although the decay is continual the entire time.

So the amount of cooling required will continue to decline as time passes although the rate of decrease will also continue to slow down.

[Kablooie]

13. So they'll have to continually dump water on the thing for 5 years?

That's a pretty tough assignment.

[Statistical]

15. Maybe less but it is a long term project.

5 years is the time period before fuel is ready for dry cask. It likely is well below ignition point long before that.

IF (big IF) they keep everything contained likely the next major move would be removing all the fuel from the 7 spent fuel ponds and consolidating them in a newly constructed pond nearby. One with proper generators, pumps, and monitors rather than the adhoc cooling they are doing now.

The reactors are far too damaged to attempt to remove the fuel so they will continue to cool them for years. It was 5 years before TMI reactor was cool enough to open and inspect.

[Octafish]

10. THAT's what's been missing from the coverage.

It was like something tugging at the back of our collective mind...

"If one reactor has a full meltdown, and you reach a critical mass of melted nuclear fuel built up inside the reactor, it could cause an atomic explosion."

[localroger]

11. Not an "atomic explosion"

It wouldn't be a hydrogen explosion like the ones we've seen so far either, since the buildings are no longer there to trap enough gas to make such a large bang.

What it would be is a STEAM explosion when the molten reactor reaches groundwater. It would throw an enormous amount of radioactive debris high into the atmosphere. It wouldn't be as bad as Chernobyl, because these reactors are much smaller and there's no burning graphite moderator. But it would still be very, very bad, making hundreds of square miles of land effectively uninhabitable and causing many cancers in people exposed at greater distances.

[flamingdem]

16. What's your take on radioactive clouds reaching the US should that happen? nt

[flamingdem]

17. The worst case scenario is being denied on the MSM

even though there is every reason to believe they won't be able to keep the rods cooled due to excess radiation at the plant.

Why do so many claim "nothing will reach the USA" when clearly a steam explosion could cause this even if not at the scale of Chernobyl.

[Kablooie]

18. To play devil's advocate:

The worst case scenario should not be announced until it has occurred.
To discuss the possibility is reasonable but to tell the populace to prepare for it while it is still speculation could be unnecessarily inflammatory.

[flamingdem]

19. I agree seeing the panic over Iodide

but personally I want to know since there will be a window of time to make preparations.

If a radioactive cloud is heading to the West Coast I wonder what they'll say then.

I can see the airports being jammed and freeways as well.