Tuesday, August 6, 2013

#Fukushima I Nuke Plant Groundwater Contamination: TEPCO's Ad-Hoc Underground Impermeable Wall in Embankment Made It Worse

This is just too ... (I can't even come up with the right word to describe).

Amateurish, maybe. Pathetic, maybe. And sad.

Because radioactive materials started to get detected in June this year in observation holes along the embankment in orders they didn't expect, TEPCO hastily decided in early July to inject waterglass in the soil of the embankment to create an impermeable wall in the ground. Since it is hot during the day at the plant, they made the workers work at night in full protection gear, from 7PM to 7AM, in the area with high radiation.

According to the articles below, we now know what many of us may have been suspecting all along. The idiom "Haste makes waste" exists for TEPCO.

It turned out that injection of chemicals to create the impermeable wall was too successful. It not only stopped the flow of groundwater, but raised the groundwater level significantly. So now, the groundwater is probably going up and over the hastily built underground impermeable wall, and through the porous, top part of the embankment into the open culvert.

The embankment is artificial, built on top of a natural sandy beach which had existed before the plant was built. There is no way to inject chemicals to solidify the top 1.8 meters. Even if it is possible, the water will simply go around the sides.

(The opening sentence of Nikkei's article below is wrong, though. There is no highly contaminated water leaking from the plant, yet. The highly contaminated water is mostly in the underground trenches, where it has been since 2011. Some may be leaking into the groundwater flowing from the west and that groundwater may be leaking into the open culvert.)

From Nikkei Shinbun (8/3/2013):


Contaminated water from Fukushima I Nuke Plant may be leaking into the ocean over the underground impermeable wall


Regarding the problem of highly contaminated water leaking from Fukushima I Nuclear Power Plant, it was revealed on August 2 that it was highly likely that the contaminated water is going over the underground "impermeable wall" and leaking into the ocean. Nuclear Regulatory Authority's working group met on August 2, and commissioners including Toyoshi Fuketa pointed out the possibility and TEPCO admitted to the possibility. As there are worries over the effect on marine creatures including fish, Nuclear Regulatory Authority ordered TEPCO to come up with emergency countermeasures.


In order to prevent the underground contaminated water from leaking into the ocean, TEPCO has been injecting special liquid called waterglass [sodium silicate solution] along the embankment to solidify the soil and build an impermeable wall since early July. The wall is set deeper than 1.8 meters from the surface.


The working group came to the conclusion that because the underground impermeable wall stopped the flow of groundwater, the level of groundwater rose recently, and went over the top of the wall. Not only the groundwater could go over the impermeable wall but go around the wall and leak from the sides of the wall.


TEPCO will start digging wells near the impermeable wall to draw groundwater and lower the water level. The company hopes to finish by the end of this month. Groundwater is flowing in from the mountain side (west) at the rate of 100 tonnes per day, and TEPCO needs to draw more than that amount. Storage of the water thus drawn will be discussed later.

(Diagram from Nikkei Shinbun, English labels are by me.)

Now, what is the point of drawing the contaminated groundwater along the embankment? In haste? Particularly when the levels of cesium, all-beta, and tritium in the open culvert have not risen in a significant manner? Do they even stop and think?

They have to somehow stop the groundwater upstream, before it reaches the space between the turbine buildings and the embankment and gets contaminated.

According to an article by Mainichi Shinbun that only appeared in Fukushima local edition (7/24/2013), the embankment was a landfill:


This area was reclaimed in the 1960s when the plant was being constructed. TEPCO explains that the land was made by piling up mudstones and sandstones on the beach.

And just like anything else - from removing fuel rods from the spent fuel pools to removing the corium from the broken reactors - TEPCO has been made to promise the wells will be dug "ahead of schedule", starting this weekend, according to Yomiuri Shinbun (8/6/2013).

The Yomiuri article makes no mention of what will happen to the water drawn from the wells.

What's the point of drawing the water "ahead of schedule" when you don't even know what to do with it?

I am more convinced that construction of the impermeable wall in the ocean by driving sheet piles in the open culvert with vibratory hammer has caused the leak by disturbing the underground trenches and joints that were already damaged by the March 11, 2011 earthquake and tsunami. The trenches and shafts were filled with highly contaminated water from April/May 2011 leak from the turbine buildings for Reactors 2 and 3.

TEPCO did not want to deal with the highly contaminated water, and instead decided to inject waterglass, thinking that would stop any water from flowing into the ocean.

My guess is that by hastily injecting waterglass TEPCO wanted at least few weeks of non detection or low detection of radioactive materials from the observation holes, so that they could somehow proceed on releasing the uncontaminated groundwater drawn from upstream into the ocean.

For now, TEPCO cannot release any water, and groundwater keeps flowing from west to east without any hindrance.

The photo below is from July 16, as workers injected waterglass in an effort to stop the groundwater (from TEPCO's Photos and Videos Library 7/17/2013):


Anonymous said...

You have the part right about working to divert water flowing from the upstream side first. When building a dam, the first thing you do is build a temporary dam to stop the flow. Side channels or pipes help divert the water around the work site until you can can get four sides built like a cofferdam but this one being underground walls.

TEPCO sunk a bunch of wells upstream, that didn't do anything except attract more water. They needed the glass injections dams first...upstream. Then two more sides and finally the seaside wall to complete a modified cofferdam.

Good thing they didn't try to stop the flow over the top on the seaside wall. It is the only safety relief overflow that they have beside flow going around the unfinished wall.

If the glass injection project is working that great then they should stop what they are doing and pickup and move upstream and start there. Last thing they need is saturated ground when the next big quake strikes.

Anonymous said...

Great post and comments admin..
posted to nuclear-news.net
hope it flies!

Post a Comment