Sunday, May 27, 2012

TEPCO to Attempt Removing 2 New Fuel Assemblies from Reactor 4 SFP at #Fukushima I Nuke Plant

The original plan of the "roadmap" was to build a protective structure over the reactor building first, and then start removing the fuel assemblies in December 2013.

From Yomiuri Shinbun (5/27/2012):


TEPCO has decided to remove part of the new fuel assemblies stored in the Spent Fuel Pool of Reactor 4 at Fukushima I Nucleaer Power Plant in July.


It will be the first removal of nuclear fuel since the start of the accident.


There are 1535 fuel assemblies stored in the Reactor 4 Spent Fuel Pool, including 204 new fuel assemblies. The plan was to build a "cover" structure for the building equipped with a crane [to remove the fuel assemblies], and start removing the fuel assemblies in December 2013.


The new fuel has no problem of heat from the fission products and are easier to handle than the spent fuel. TEPCO has decided to remove a few new fuel assemblies and inspect the condition.

The worker who tweets from Fuku-I says TEPCO will take out 2 assemblies. Since they have never been used, they can be lifted in the air, he says.

Even so, it doesn't seem to me to be a critical, essential task to be done at the plant right now. It seems like an unnecessary, risky endeavor.

What is instructive is some of the tweets in response to the worker's tweet. "Oh is there anything left in the Reactor 4 SFP?" or "The fuel assemblies still keeping the shape?" TEPCO's videos of the Reactor 4 SFP (here and here, for example) means nothing to them and many others, though they seem to believe the worker.

For the possible locations of the new fuel bundles in the Reactor 4 SFP, see my 4/25/2012 post (look for the darkest colored assemblies).


Anonymous said...

To me, this is a good thing. It demonstrates an increased urgency, which TEPCO and the JP government have been lacking.

There is a risk, but there will always be a risk. In a new enterprise like this, baby steps are needed, so two rods from the group of new fuel makes sense as a start.

Also, I don't know how many casualties will result if the spent fuel pool burns, but I would not be at all surprised if the experts were to tell us that 10,000 cancers might be prevented for every fuel rod that doesn't burn when this thing eventually collapses and burns.

It's progress. Slow progress. But an improvement all the same.

Anonymous said...

I disagree. It's risky in the environment still cluttered with a lot of debris and temporary scaffolding. The unused fuel bundles don't pose risk, inside or outside the pool, but trying to remove may create risk.

How come you are suddenly eager to take risk?

If they're doing this just to placate those so-called experts from the US, I hope those experts will be fully willing to take the responsibility in case of an unexpected accident.

Atomfritz said...

I am not sure about the actual motives behind this.

Afaik there hasn't been an experiment like this before, using corrosive seawater as spent fuel coolant.
So it could be helpful to know actual data about corrosion.
However it would be of limited value as one cannot actually interpolate from corrosion on new fuel elements to that one happening on the burnt-up hot fuel, which is more reactive and erosion-prone (due to convection).
Anyway, it would give a hint about the to-be-expected best possible fuel shape when the pool finally gets extracted.
Judging from the high pool water contamination, there are damaged/leaking fuel assemblies to be expected, complicating the extraction.

And, I am not sure if the two fuel assemblies will be extracted by a precision crane or just by a normal construction crane. The latter could lead to complications, fuel getting jammed or damaged otherwise.

Remember, even precision fuel extraction cranes fail, sometimes having led to fuel fires at open air.

For example, the decommissioning of the Calder Hall class Magnox reactor fleet in UK far before the scheduled decommissioning date was a consequence of the Chapelcross incident.

At this incident, spent fuel was dropped from a fuel handling machine and it was pure luck that it landed in water, else it would have caused a catastrophic fuel fire.
The cause was a design flaw of the fuel handling machine, and as the remedial of this flaw would have been too costly, the Brits preferred to decommission their entire fleet of their first generation Magnox reactors.

So I hope Tepco prepares well so that there won't be accidents at actual hot fuel extraction.
At least I hope they'll tell us the examination results of the two assemblies.

Anonymous said...

I agree that any reduction in the nuclear inventory in any of the spent fuel pools of the damaged reactors is a good thing. Considering all the hand-wringing that has been done about SPF4, I would think that reducing the burden in the pool, potentially improving circulation, reduction in risk potential (two less assemblies to catch on fire, which is the scenario most people seem to be freaking out over), plus a proof of concept test for the crane assembly, are all good things.

Anonymous said...

risky thing.
Why anticipate the building of a proper confinment and extraction mechanism, just for the less dangerous part. This is really the lowest hanging fruit, and a dangerous one.

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