2 Japanese nuclear reactors may be in meltdown

[gary]

Looking at NHK weather report, winds are predominantly prevailing West to
East 10 to 18 km/h and not to expected to strengthen in the next 24 hours.

So hopefully the winds will blow some radiation out to the Pacific.

Cold front coming in and rain and snow predicted first in the west and later on the
east coast.

TEPCO report via NHK that as at 12:29 AEST, "half the rods are still exposed" on No. 2 and that "they cannot deny
that they may be melting".

TEPCO report radiation levels around the reactor reached 8 times legal levels for a person to be exposed to over one year.
It has since gone down and they are investigating "why the radiation levels are fluctuating so much".

Workers at No 2 that were asked to leave for safery reasons do not include those who are actively attempting to
cool the reactor.

[MrB (Simon)]

ahaaa

[Octane (Humayun)]

I stayed up last night reading the links on how reactors work -- very enlightening. Thanks for posting the blog link and BoingBoing link.

It's just utterly horrific what's happened in Japan. Nature can be a cruel mistress.

H

[DavidU (Dave)]

There is now a fire in a 4th reactor.

[CraigS]

It seems inconceivable that the cooling system design was vulnerable to tsunami damage in an earthquake prone region of the world …

I guess we'll find out eventually (perhaps, too early to know), but exactly in what part of the cooling systems did the water ingress cause the problems ?

(Perhaps a rhetorical question).

[mswhin63 (Malcolm)]

Originally Posted by CraigS

It seems inconceivable that the cooling system design was vulnerable to tsunami damage in an earthquake prone region of the world …

I guess we'll find out eventually (perhaps, too early to know), but exactly in what part of the cooling systems did the water ingress cause the problems ?

(Perhaps a rhetorical question).

I think it was mentioned earlier that it had knocked out all the diesel generators to run the pumps. They tried to truck in some pumps which also failed or were not able to come in.

[CraigS]

Originally Posted by mswhin63

I think it was mentioned earlier that it had knocked out all the diesel generators to run the pumps. They tried to truck in some pumps which also failed or were not able to come in.

Hmm .. it wouldn't seem to be that difficult to protect diesels from water ingress .. (that's if someone thought of it, in the first place, I suppose).

[Steffen]

There is no risk of a "China Syndrome", because China doesn't lie opposite of Japan…

Cheers
Steffen.

[MrB (Simon)]

It would be the "Off-the-coast-of-Argentina Syndrome" or "South Atlantic Ocean Syndrome"

[gary]

NHK report that the explosion in No 3. was likely caused by spent fuel
rods being exposed to air.

Once fuel rods are spent, they are removed from the reactor by crane and kept
submerged in a concrete pool filled with water near the top of the reactor vessel.
Since the spent rods take three to four years to cool, it is important that cold
water is continually pumped in and circulated around them.

The pumping system failed due to the power outage and the spent rods became
partially exposed to air and hydrogen was produced which later ignited.

So just as the integrity of the main reactors vessels is paramount, the integrity
of the pools that hold the spent rods is also vitally important.

Unfortunately wind directions around the crippled reactors is westward.

[CraigS]

Gary;

This couldn't get much uglier !!

Rods being exposed to air ??

[casstony]

Perhaps reactors should only be built on stable continents, away from tsunamis, away from water catchments, near an emergency gravity fed water supply, away from regulatory failure................. or maybe we should steer more taxes toward developing more competitive solar technology which people would adopt because it made financial sense.

[gary]

Originally Posted by CraigS

Gary;

This couldn't get much uglier !!

Rods being exposed to air ??

Hi Craig,

It's not a good day.

So not only will a battle being going on to keep the rods inside the reactors cool,
there is a second battle front which is to ensure that the rods that have been spent
and are outside the reactors themselves remain cool as well.

NHK reports that one of the radiation leakage incidents may have been as a result of
the spent rods becoming exposed in the pool. These were associated with a reactor
that the NY Times reports had been under refurbishment for months before the
quake. The NY Times reports that when the spent rods become exposed,
"That is almost as dangerous as the fuel in working reactors melting down,
because the spent fuel can also spew radioactivity into the atmosphere."

What is sobering are the NHK reports of the radiation levels in parts of the
plant facilities themselves where at one point it peaked at 400 millisieverts an hour.
The NY Times suggest that 75 minutes exposure to those levels will result
in severe radiation sickness. NHK reported that exposure to 500 millisieverts for
two hours would result in certain death.

Levels in the areas outside the plants were significantly lower. However, one would have
to be severely concerned for the workers inside the plant who are trying to
stabilize the various events they are dealing with. Many of these would be experts
in their areas and one would only assume many will be totally aware of the peril
they face. Heroes? I for one think by any definition of the word. All we can do is
wish them good luck.

[CraigS]

Yes Gary;

I was thinking that the source information for all these reports we keep getting, must be coming from somewhere close to the problems.

All I keep think about is that dreadful scene from the movie K-19.

Methinks the political head responsible for Japanese Energy should be on suicide watch, also.

Its overwhelmingly sad and shocking.

I just can't wrap my mind around how the engineering has failed them !
So many minds involved in the design of these plants for so many years … all the technology .. and yet a simple thing like protecting the diesels from water ?? There's got to be much more to it all than this …

[toc (Tim)]

I remember reading that the Germans came up with a reactor design that involved carbon spheres to isolate the fuel, and made it impossible for a meltdown to occur. Might have dreamed it though.

EDIT: Found it on Wikipedia:

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

Looks like it has problems as well...

[casstony]

There must be some way to get nuclear energy safetly. Maybe we could have the reactor out in space and transport the energy produced to Earth. I know we could figure it out if we just put our minds to the task.

[CraigS]

Advances will happen as a result of incidents like this.

This is how technological progress occurs.

Quantum leaps in this area represent higher risk.

I'd still like to understand more about what has actually happened over there.
I have doubts that we're getting the full (& accurate) picture.

Nuclear is here to stay.

[GrahamL]

Tony from the replys in stephens link last page.

The Fukishima nuclear reactors are Boiling Water Reactors, BWRs. So they were designed and built by the GE-led, BWR reactor consortium.
It is reassuring to note that the new American “Standard Design ” reactors, so painstakingly being designed, reviewed, modified and certified, ALREADY INCLUDE extra provisions for the remote set of circumstances that affected one of the 53 nuclear reactors in Japan forced by the Japanese Earthquake and subsequent tsunami.
New American “Standard Designs” are re-designed so that they have no problems if commercial power is unavailable; and All not just some of the emergency diesel generators did not start.
The new “Standard Designs” nearing final approval, after almost five exhaustive years, of analsysis, modification, and approval and final certification of every nut and bolt in the design. They were redesigned to not need the power for the pumps, at all. These new “Standard Designs” rely on placing the coolant tank above the reactors and letting the emergency cooling water flow down into the reactor vessel by gravity, without needing any pumps. Secondly, they have been redesigned so that the coolant capacity is much larger inside the reactor vessel, requiring less from outside to be added.
Third, the larger coolant capacity reactors are not so time critical to a meltdown. They extend the time to a meltdown without cooling to several hours instead of 45 minutes, allowing more time to thoughtfully react.
Fourth, they have been redesigned so that natural thermal convection will circulate the coolant water, inside the reactor, thus eliminating the need for power to the pumps, or the pumps at all.
Isn’t it further proof that the new reactors and the new NRC certification scheme of “Standard Design”, makes much more sense. It used to be that letting progress occur by each new plant be a single design, perhaps incorporating new features unique to itself, and much more anticipatory rather than reviews while under construction, or in post-accident design fixes

[Rob_K]

Originally Posted by casstony

Maybe we could have the reactor out in space and transport the energy produced to Earth.

We already have one - it's called the Sun.

Cheers -

[TrevorW]

Lets not forget they've survived horrific radiation fallout before, they can do it again