Sunday, August 31, 2014

#Fukushima I NPP Progress Report on Ice Plug in Reactor 2 Trench: Time for Plan C (and Diaper Polymer May Be Back...)

Plan A, if you recall, was to freeze the highly contaminated water at the head of the trench right outside the Reactor 2 turbine building (Shaft A, on the northeast corner of the turbine building) to create an ice plug by placing several freezing pipes in the trench. Why is a plug needed? Because TEPCO wants to drain the highly contaminated water from the trench.

What TEPCO did not say was the existence of many obstacles at the trench head - i.e. numerous pipes for electrical wires and water transport. So the freezing pipes couldn't be placed in part of the duct where these pipes go through, and after two months of trying TEPCO admitted to the problem that the water remained unfrozen. Also, TEPCO admitted that there was a constant flow of water from the turbine building into the trench through many openings (pipes go through the building walls into the trench after all) that prevented the water from freezing. (Duh.)

(A red-shaded rectangle in the bottom right in the slide below is the intended ice plug)

So, on to Plan B.

Plan B, if you recall, was to dump crushed ice and dry ice to lower the temperature of the water in the trench to 5 degrees Celsius so that (in TEPCO's mind) the water would freeze even if there was a flow of water:

Plan B ran into trouble almost as soon as it started in late July, when crushed dry ice clogged the pipe in early August and crushed ice was seen floating around on the water surface (see photo). In the end, laws of physics prevailed and the contaminated water did not completely freeze, as TEPCO finally admitted, albeit in a very convoluted way in their report to Nuclear Regulation Authority on August 19, 2014 (Japanese only, PDF).

The report by TEPCO claims that 92% of the ice plug was formed in the Reactor 2 Shaft A. Well, a failure is a failure, as TEPCO admits the water continues to flow from the turbine building into the trench even at a faster speed now that the opening is narrower.

What's worse, in the open duct that TEPCO dug at a different location (southwest corner of the Reactor 2 turbine building), the water hasn't frozen at all despite 2 months of effort using the freezing pipes.

The water temperature remains mostly above 8 degrees Celsius:

and no sign of ice:

So now, time for Plan C.

So what is Plan C? Use some (yet to be determined) type(s) of filler to completely fill the trench head, while the water is still running.

So, what are the materials TEPCO says they are considering? According to TEPCO's report on August 19, 2014 (page 24),
  • sand (drawback: can't stop water, can't be dumped in large amount)

  • iron sand (can't stop water, can't be dumped in large amount)

  • sodium polyacrylate, aka "diaper polymer" (has to be used in combination with other methods)

  • grout (depending on the types, may not fill small/large gaps)

  • solidifying material (mixture of powder and liquid; powder may clog up the pipe)

  • waterglass (cannot fill openings)

Hmmm, diaper polymer, waterglass... where did I see this before?

April 2011, at the water intake for Reactor 2, where pouring diaper polymer and concrete in the pit didn't stop the extremely contaminated water from pouring into the plant harbor. That water did not stop until waterglass was injected into the base rock UNDERNEATH the trench.

I have a feeling they will soon need Plan D.

But why fight running water? Why can't they just pump out the water right there at the shaft?

Or as one of the long-time readers of this blog "netudiant" suggested before, why not build a mobile ALPS on a barge inside the harbor?

I think I know the reason: It simply doesn't occur to them. Just like it didn't occur to them to transport batteries for controlling the reactors without the required government permit, on March 12, 2011. (See my post from October 6, 2012.)


Anonymous said...

Gundersen recently wrote this to sum up what happened on 11 March:

Anonymous said...

"...why not build a mobile ALPS on a barge inside the harbor?"

Because such barge cannot be protected from any tsunami.

The height calculation of a tsunami protecting wall can be right or wrong, but any barge on the wrong side of that wall (and close to it) would be scrap anyway.

Vyse Legendaire said...

Had to laugh at seeing 'mobile' and 'ALPS' together in the same sentence. You do know ALPs was permanently decommission because it didn't work, right?

Anonymous said...

Why is good, old fashioned concrete not on the list (actually it would be a special heavy type using barytes aggregate)? I think I know the reason: it occurs to Tepco that such a move would put them on the slippery slope to the outcome they dread most, entombing sarcophagi, a la Chernobyl.


arevamirpal::laprimavera said...

Vyse, what's slated for decommissioning is AREVA's decontamination system.

Anonymous said...

Let's all sing...

'We're busy doing nothing,
Busy the whole day through,
Trying to find lots of things not to do...'

Anonymous said...

2nd Verse

We're busy going nowhere
Isn't it just a crime?
We'd like to be unhappy but
We never do have the time

Anonymous said...

All the materials mentioned (concrete included) has one big disadvantage: right near the place where they want to use them there is a big, deep vertical hole.

What I can't understand is that why they want to preserve those pipes. They has no use. They could just cut them and plug the hole, without any further overthinking.

Anonymous said...

Anon @ 11:58

Tepco doesn't want to fix the leaks!

What's so hard to understand?

Tepco is being very gently encouraged to fix the leaks, but the truth is that if the leaks are fixed, Tepco has even more problems dealing with yet more highly contaminated water. Tepco is running out of storage tanks, ALPS doesn't work. All the other 'decontamination processes have failed. So what's so hard to understand? It suits Tepco very well to let the leaks continue.

PM Abe will just say that all the radioactive water is confined to the inner port - the masses will acquiesce and the status quo will remain the same (other than the gross health impact sometime in the future)

Anonymous said...

... and ... if Tepco plugs the leaks the contractor gravy train sees its demise [problem became too simplified].

Anonymous said...

. Do not be fooled by the charade.
They know it won't work.
They know they have to keep dumping water into the ocean.
But they have to make it look like they are doing something.
While they continue to dump water into the ocean
.it is very simple.
. If you do nothing but dump in ocean people angry.
If you tell them you try no matter how foolish, less angry.

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