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that plant is going to cost big time , Japan can rehouse and encourage businesses and get back on its feet but not with that goliath slung round its neck

Tepco were shut down for how long ?1yr? 2yrs? and had to bring their sites into line only a few yrs ago then they had their biggest plant go down in the 07 quake that had to be brought up to spec they were being pressured to get the 2 fukushimas up to standard when bam that is a hell of a lot for a company to survive

@es that would probably never have made msm a few weeks ago it is good (in a bad way) that finally the press are becoming aware that it is news and people want to know

Edano.. I haven't checked for a few days so Im' not certain

I will check later,, Edano

Local Criticality: Learn what it means and what is happening now at Fukushima
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Subcritical (K<1) – 99 or less fission events will occur from 100 fission events
Critical (K=1) – Exactly 100 new fission events will occur from 100 previous fission events.
Supercritical (K>1) – More then 100 fission events will occur after 100 fission events.
Prompt Critical (K>1) – When the immediately released neutrons are enough to create an equal or greater number of fission events.

The neutron splits Uranium-235 and that atom releases 2-3 neutrons on average 2.4

Not every neutron is released immediately. The ones that are released immediately are called the prompt-neutrons. Immediately after the fission event the prompt neutrons will create another fission event in microseconds. Also after the initial fission event short-lived radio isotopes are released that eventually release neutrons as well. These neutrons are called delay neutrons, which can be delayed by minutes versus microseconds. Such a chain reaction involving the growth dependent upon delayed-neutrons is a bomb is super slow motion, controllable.

So we have Prompt-Neutrons and Delay-Neutrons creating more fission events in a chain reaction. In nuclear power a balance of the two is crucial in maintaining perfect criticality.

The control rod is a material that effectively absorbs neutrons. It is raised to initiate the nuclear reaction to power the plants steam generators. Once the specific reaction level is reached the control rods are slightly adjusted to reach a perfect critical. Where the chain reaction sustains itself indefinitely as only one fission event is achieved from one fission event. This results in a gently glow of fission versus a chain reaction from a bomb. Only mild changes to the control rods over time are needed as maintenance operation.

If the rods are extracted to far the core will under go prompt-criticality. Meaning the number of prompt-neutrons, the ones immediately released, will be enough to create equal or greater number of fission events immediately afterwards. The fission events will grow so fast we can not control it. This is ideal in a bomb and can happen in a run away chain reaction of fuel rods. This is called going prompt-critical and is avoided at all cost.

The US Army had an accident when a worker removed the control rod too far during start-up maintenance and caused a near instant prompt-criticality resulting in the explosion of the water from flash steaming. One of the workers was pinned to the roof with pieces of the reactor through his body, from groin to shoulder, dead.
This will give you an idea how fast this can go bad without control rods.

Now, distances the neutron must travel also determines the criticality level. The farther it must travel means lesser chances of creating a fission event in another Uranium-235 atom. This is calculated when the fuel rods are designed, built and deployed. Every factor that effects the criticality level is closely monitored and thoroughly controlled.

So now here is why a local criticality is bad news. It means there is a stable chain reaction growing. The temps will get hot enough to melt all the fuel into a corium blob. And remember how distance also effects criticality?

When the uranium-235 gathers together in a blob the prompt-critical threshold is lowered dramatically. The number of prompt-neutrons increase and the number of delay-neutrons will decrease. The Russians avoided a prompt-criticality by sacrificing hundreds of workers lives to stop one reactor, Chernobyl. Here we have three reactors going bad and 100 tons of spent fuel fully exposed to the atmosphere with the Fukushima 50. This disaster is seriously under manned and is headed to a much larger disaster fast.

Once prompt-criticality is reached, absolutely nothing will stop that chain reaction except for one thing, another larger chain reaction spending its fuel rapidly.

At least one core has gone supercritical so far. When it goes prompt-critical it will explode like a nuclear weapon gone bad. It will detonate just like any other nuclear fission bomb but the yield will be lower in relation to the fuel provided. This is in theory, but it is a strong theory backed up by many.

Did you understand that? The yield of going prompt-critical is in direction proportion of how much fuel is available. Any one reactor core going prompt will use all the fuel on site. I do not know the figures to calculate a fizzled nuclear explosion.

sorry that was so long.. read up.. will return later