Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[nikkkom]

The plan to keep basements flooded for a decade doesn't sound good to me.
Everything metallic will rust through for sure; what about concrete in the foundations? Is it designed to be stable in permanently wet state?

 

[etudiant]

The plan to keep basements flooded for a decade doesn't sound good to me.
Everything metallic will rust through for sure; what about concrete in the foundations? Is it designed to be stable in permanently wet state?

The long term stability of the structure is clearly a concern, but as with everything else about this disaster, it is uncharted territory. There have been recommendations to block the flow of groundwater into the facility by creating a deep barrier of frozen ground uphill from the site.
That might then allow the site to be drained, as the fuel will also be cool enough for dry storage in a few more years. Unfortunately, the site is still murderously radioactive and likely to stay that way for decades, so until the robotics industry steps up its game, it is probably safer to leave the place submerged.

 

[nikkkom]

The long term stability of the structure is clearly a concern, but as with everything else about this disaster, it is uncharted territory.

Not sure about it. The history of Chernobyl could provide quite a number of lessons.

 

[Rive]

Recent revelations of significantly radioactive ground water levels rising and ground water reaching harbor in significant amounts contradicts this picture. Clearly, water flows out of basements into the ground.

It's a bit more difficult.

There is a groundwater level around the unit/turbine building, and there is another around the main seawater pumps near the harbor (which level is lower).

The water level of the turbine buildings is kept lower than the local groundwater level, which causes a massive inflow. This inflow prevents the groundwater contamination around the turbine building and increases the water amount stored in the site.

However, there are some 'forgotten' power cable trenches between the turbine buildings and the main seawater pumps. These trenches are filled with water from the turbine building. And the water level of these trenches - which is ~ the same as in the turbine building - is clearly higher than the groundwater level around the seawater pumps. This causes an outflow there.

Actually, they are halfway with the solution. The groundwater bypass - once becomes operational - will reduce the groundwater level around the turbine building: so they can reduce the water level in the buildings (and in the trenches) and still keep the inflow in the turbine building.

Also, they made some drilling and chemical injections/solidification near the harbor: this is already started to raise the groundwater level there (around the seawater pumps).

Once/if the groundwater level around the pumps becomes higher than in the trench, they win.

If it's not possible or they can't make it, then they will have to freeze those trenches (but as it seems now, nothing else).

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130806/0800_kumiage.html After solifidying the ground in the area along the sea, the ground water level started rising and it is feared that it has started overflowing and pouring into the sea. Tepco was planning to start pumping up that ground water at the end of this month, but after receiving instructions from the NRA to start as soon as possible, it is starting this week to dig small wells and to pump up water. The water will be temporarily stored in an underground facility, and later it will be stored in the storage tanks within the plant premises. Between July 31 and August 5, in the measurement wells on the side of unit 2, cesium concentration rose 14-fold, and all beta (including strontium) rose 46-fold. Tepco doesn't know the reason for the rise and is researching the details of the cause. Now, two years and 4 months after the accident, the concrete situation and the spreading of consequences of contaminated water outflows are still unknown, and responses are following each other like searching one's way in the dark with one's hand.

http://www.tepco.co.jp/en/nu/fukushima-np/f1/smp/2013/images/2tb-east_13080502-e.pdf Detailed Analysis Results in the Port of Fukushima Daiichi NPS, around Discharge Channel and Bank Protection Underground Water Obtained at Bank Protection, 5 August 2013

 

[turi]

They had a look at the Unit 2 PCV on 2nd of August but weren't able to gather as much information as they wanted. They should have retried it today:
http://210.250.6.22/en/nu/fukushima-np/handouts/2013/images/handouts_130731_09-e.pdf

 

[tsutsuji]

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130807_07-e.pdf (7 August 2013) Draining Plan between the Water Intake Channel of Unit 1 and Unit 2 at Fukushima Daiichi Nuclear Power Station


http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130722_07-e.pdf (22 July 2013, 47 pages, English) Increases in the Concentration of Radioactive Materials in Seawater and Groundwater on the Ocean Side of the Site: Current Situation and Countermeasures

A summary:

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130803/index.html (3 August 2013) The NRA has set up a new working group dedicated to the contaminated water outflow into the sea. It had its first meeting on 2 August 2013. It admitted that it is feared that the ground water has already overflowed over the solidified ground layer, as the water level rose. As a countermeasure, they announced a plan to install new equipments called "catch basins", and to start pumping up water at the end of this month. Opinions were voiced such as the opinion that the countermeasures must be taken more quickly than planned and the opinion that the ground water flow must be analysed in detail. The NRA has set up another working group whose task is to analyse the spreading of radioactive substances that poured into the sea and to assess the consequences on the environment. Tepco estimates the tritium released into the sea from May 2011 to July 2013 to be between 20,000,000,000,000 and 40,000,000,000,000 Bq. This is about the same amount as the yearly release that is allowed under the regulations for the plant under normal operation. As regards cesium and strontium, it will take more time to produce an estimate because this requires analysing the underground migrations.

< The contaminated ground water problem >

Ground water containing radioactive substances are a problem in the area where Fukushima Daiichi units 1,2,3 and 4 are located.

From north to south, units 1,2,3 and 4 are located in a row.

Each unit consists, from the mountain side to the sea side, of a reactor building and a turbine building, and between there and the sea there are a number of ramified underground tunnels called "torenchi" in Japanese (from the English "trench"), inside which seawater intake pipes or electric cables are passing.

The ground water containing highly concentrated radioactive substances is mainly accumulated inside the turbine building basements or inside the trenches, but it is thought that some of it has seeped out into the surrounding ground.

(a) The seawater brought by the tsunami (b) water that has been in direct contact with the meltdown fuel (c) ground water flowing from the mountain side. These are the components of the large quantities of contaminated water containing radioactive substances released by the accidents.

The trigger of the problem is the detection of highly concentrated radioactive substances in ground water measurement wells on the sea side near unit 2 in May 2013.

In particular, the tritium concentration had risen, reaching a value 10 times higher than the value measured in a survey performed at the end of 2012.

The tritium concentration in the sea water in the harbour had also risen.

In July 2013, after it was understood that since April the ground water in the well had been moving up and down in coupling with the sea water level, Tepco admitted that contaminated ground water was pouring into the sea.

Tepco and the NRA hold a few considerations concerning the contamination of the ground water.

First, shortly after the accident in April 2011, when contaminated water poured into the sea in the vicinity of unit 2's water intake, some of this water spread underground, so that it is possible that it is detected in the ground water.

As the outflow route was understood to be through the trenches between the turbine building and the sea, as a countermeasure to prevent outflow into the sea, Tepco dammed up the trenches between the mountain side and the sea side.

Thereafter, it was indicated that there is a possibility that the highly concentrated contaminated water accumulated in the trenches passed through earthquake-damaged parts and spread through the permeable gravel layer.

It had been understood since the accident that close to 20,000 tons of contaminated water was accumulated in the trenches, but no radical solution such as purification or removal was carried out.

Furthermore, it is feared that some of the large quantities of contaminated water accumulated in turbine building basements are leaking out through the trenches even now.

Tepco's response to the present problem is severely criticized.

It took them one month to admit that ground water is leaking into the sea.

Tepco admitted how bad that response was, by saying: "concerned by commercial damage caused by bad image [to local fisheries?], as a priority, we withheld the conclusions until we obtained the data that support a final conclusion, rather than having an attitude of actively disclosing the risks".

Tepco did not put into practice one of the lessons from the accident formulated as "implement multi-layered countermeasures based on the worse case scenario".

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201308030046 (03 August 2013)

calculations show that if the water levels continue to rise at the current pace, contaminated water will flood the surface in about three weeks.

...

According to one calculation, about 100 tons of groundwater would have to be pumped up daily to prevent the water from leaking into the ocean. But the plant is running out of storage space for the contaminated water.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130809/index.html In order to lower the ground water level, Tepco started drawing water from small scale wells near the shore protection bank at 02:00 PM on 9 August 2013. By the middle of next week, Tepco plans to insert thirty 5-metre long pipes into the ground and together they will provide a 100 ton/day water removing capacity.

 

[zapperzero]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130809/index.html In order to lower the ground water level, Tepco started drawing water from small scale wells near the shore protection bank at 02:00 PM on 9 August 2013. By the middle of next week, Tepco plans to insert thirty 5-metre long pipes into the ground and together they will provide a 100 ton/day water removing capacity.

Amateur hour all over again. These guys never heard of Archimedes probably. That... is not how you dry out a piece of land.

 

[Rive]

Amateur hour all over again. These guys never heard of Archimedes probably. That... is not how you dry out a piece of land.

It's a trap.

With too low groundwater level the outflow from the trench to the groundwater would increase.
With too high groundwater level the outflow of the groundwater to the sea would increase.

As it seems now with the given water level in the trench there is no good (fast) solution.

 

[etudiant]

Drying out the site is probably undesirable, because the nuclear fuel is surely safer under 20 feet of water than exposed to open air.
What is wanted is to halt the flow of water through the site, because that carries ongoing contamination to the sea. However, because the ground water flow is down from the hills and into the sea, it must not only be prevented from entering the site, but also the sea must be prevented from replacing the ground water outflow with a saline inflow.
So the real requirement is to dike off the plant completely, which will require major work, because the bedrock is 60 feet down, if memory serves. The proposal to freezes the ground uphill from the site to create a barrier to the water inflow seems a reasonable first step which however must be coordinated with the already ongoing seawall construction to avoid pooling contaminated water on the surface of the site.
Is anyone in charge at Fukushima who has the ability to communicate how the various measures taken fit into the long term plan? It would be so helpful.

 

[etudiant]

Drying out the site is probably undesirable, because the nuclear fuel is surely safer under 20 feet of water than exposed to open air.
What is wanted is to halt the flow of water through the site, because that carries ongoing contamination to the sea. However, because the ground water flow is down from the hills and into the sea, it must not only be prevented from entering the site, but also the sea must be prevented from replacing the ground water outflow with a saline inflow.
So the real requirement is to dike off the plant completely, which will require major work, because the bedrock is 60 feet down, if memory serves. The proposal to freezes the ground uphill from the site to create a barrier to the water inflow seems a reasonable first step which however must be coordinated with the already ongoing seawall construction to avoid pooling contaminated water on the surface of the site.
Is anyone in charge at Fukushima who has the ability to communicate how the various measures taken fit into the long term plan? It would be so helpful.

 

[nikkkom]

Drying out the site is probably undesirable, because the nuclear fuel is surely safer under 20 feet of water than exposed to open air.

IIRC in Fukushima there are no known instances of accident-produced nuclear fuel outside of containments, so no fuel can be exposed to *open* air by drying.

In Chernobyl predictions that solidified core melt would generate dust by alpha-spalling proved wrong. In fact it turned out that corium "lava" is durable, is was hard to fracture it for obtaining samples.

 

[nikkkom]

The water level of the turbine buildings is kept lower than the local groundwater level, which causes a massive inflow. This inflow prevents the groundwater contamination around the turbine building and increases the water amount stored in the site.

However, there are some 'forgotten' power cable trenches between the turbine buildings and the main seawater pumps. These trenches are filled with water from the turbine building. And the water level of these trenches - which is ~ the same as in the turbine building - is clearly higher than the groundwater level around the seawater pumps. This causes an outflow there.

How many centuries TEPCO needs to find and block those trenches? :(

 

[SteveElbows]

I have been waiting for news of the next attempt at looking in the pedestal area of reactor 2. The previous attempt as detailed on August 2nd took too long, so they had to end it prematurely. (as discussed in this document: http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130802_06-e.pdf )

But as I have not seen any fresh documents, I am assuming the next attempt is running behind schedule? I can see from one of the Japanese daily updates that something that sounds like the water sampling that was supposed to happen the day before the next attempt may have taken place, but the computer translation of the paragraph in question is very poor. So I was wondering if someone would be kind enough to translate it properly?

2号機原子炉格納容器の滞留水採取作業を実施。採水終了後、装置(サンプリングホース・カメ ラ)をガイドパイプに収め、X-53 ペネの中に引き抜き、ペネからガイドパイプを引き抜くことができ なかった。8/8、装置(ガイドパイプ)の引き抜き作業を実施したところ、ガイドパイプについては回 収できたが、カメラとサンプリングホースの吸い込み口部分が無くなっていることを確認。8/12 以 降、作業の検討などを踏まえて、原子炉格納容器内部調査の未実施分を調査する予定。

It's from the 2nd page of this document: http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130809_03-j.pdf

Many thanks.

 

[Rive]

How many centuries TEPCO needs to find and block those trenches? :(

It'll be some weeks to get through the usual papermill of permissions and such: also some time the prepare the equipment they need and start.

What is a more relevant question here (IMHO): how could they forget those trenches? There was a really serious leak there at the beginning of '11.04.

 

[tsutsuji]

2号機原子炉格納容器の滞留水採取作業を実施。採水終了後、装置(サンプリングホース・カメ ラ)をガイドパイプに収め、X-53 ペネの中に引き抜き、ペネからガイドパイプを引き抜くことができ なかった。8/8、装置(ガイドパイプ)の引き抜き作業を実施したところ、ガイドパイプについては回 収できたが、カメラとサンプリングホースの吸い込み口部分が無くなっていることを確認。8/12 以 降、作業の検討などを踏まえて、原子炉格納容器内部調査の未実施分を調査する予定。

It's from the 2nd page of this document: http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130809_03-j.pdf

Many thanks.

[On 7 August 2013] Unit 2 PCV accumulated water sampling work was performed. After completing the water sampling, the equipment (sampling hose, camera) was put back into the guide pipe, and pulled into penetration X-53, but it was not possible to pull the guide pipe from the penetration. On 8 August, as we undertook the work of pulling the equipment (guide pipe), we could retrieve the guide pipe, but we found that the camera and the sampling hose's sucking mouth part were missing. From 12 August onwards, based on the study of the work, we plan to perform the still not executed part of the PCV internal survey.


Thanks, Steve, for keeping us informed of the unit 2 PCV investigations.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130810/index.html In wells located 2 m away on the mountain side, the ground water level was found to be about 60 cm above the solidified ground underground wall (16 m deep, but the shallowest part 1.8 m from the ground surface is hard to solidify, and water can overflow the wall in that part). This means that the solidified ground underground wall has lost its function.

 

[Rive]

This means that the solidified ground underground wall has lost its function.

Now they have a target level to reach with the water pumping.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130812/index.html There was an NRA working group meeting on 12 August. They announced a plan to remove 60 ton/day from the unit1 and unit 2 area in order to keep the water level below the underground wall. Together with the unit 3 and unit 4 area, they want to remove 80 ton/day from next month. The NRA instructed to reinforce water level monitoring during the typhoon season.

 

[LabratSR]

I have been waiting for news of the next attempt at looking in the pedestal area of reactor 2. The previous attempt as detailed on August 2nd took too long, so they had to end it prematurely. (as discussed in this document: http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130802_06-e.pdf )

But as I have not seen any fresh documents, I am assuming the next attempt is running behind schedule? I can see from one of the Japanese daily updates that something that sounds like the water sampling that was supposed to happen the day before the next attempt may have taken place, but the computer translation of the paragraph in question is very poor. So I was wondering if someone would be kind enough to translate it properly?



It's from the 2nd page of this document: http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130809_03-j.pdf

Many thanks.

http://ex-skf.blogspot.com/2013/08/fukushima-i-nuke-plant-reactor-2.html

 

[Bandit127]

Ten workers at the crippled Fukushima nuclear power plant were exposed to radiation from contaminated mist, TEPCO says. Workers in the building were prohibited from using tap water, which comes from the same tainted source 10 km from the facility.

http://rt.com/news/fukushima-workers-contaminated-radiation-393/

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130813/index.html When they left the plant premises at 00:40 PM on 12 August, 10 employees were found to be contaminated mainly on their face and head. The highest contamination was 19 Bq/cm², which is 5 times Tepco's internal standard. The cause is being investigated. The mist generators installed as a countermeasure against heat strokes in the surroundings of the earthquake-isolated building are suspected. The contaminated employees were working indoors, but they took the bus in front of the earthquake-isolated building which is used as a base. Also, an air radiation alarm rang in this area in front of the earthquake-isolated building.

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130812_03-e.pdf Alarm Went off at the Dust Monitor Installed in front of the Main Anti-earthquake Building

http://www.tokyo-np.co.jp/article/national/news/CK2013081302000129.html The contaminations are between 4 and 19 Bq/cm², which is 5 times Tepco's internal standard but less than the legal limit requiring decontamination. Tepco said [such contamination] "does not bear consequences on health". In order to investigate the cause, Tepco will check the mist generator's sprinklers, check each contaminated employee's movements, and examine the possibility that the bus could have projected contaminants upwards.

 

[SteveElbows]

Thanks very much for the translation tsutsuji.

Documents in english related to the subsequent reactor 2 investigation (after that water sampling one) are available in english now: http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130812_06-e.pdf

As usual the image quality is rather poor and the ambient dose info obtained isn't released yet. I wonder when they hope to do the actual investigation of the pedestal area, using penetration X-6 instead of X-53.

 

[Rive]

As usual the image quality is rather poor ...

Once they release the video of the investigation I plan to look after that.

 

[LabratSR]

The video is posted.

http://photo.tepco.co.jp/en/date/2013/201308-e/130812-02e.html

 

[Rive]

Not much can be done with the images I'm afraid:
- they are using some kind of filter to remove the worst of the radiation 'hits': this filter is interfering with the averaging
- they did not show the most interesting places/did not checked the interesting places
- the light is still low

Anyway, at least the noise could be removed.

 

[Rive]

One more thing: I bet they are also using some variation of this trick, the video has many 'still' parts, ideal for averaging...

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130815/index.html After the pumping from small scale wells that was started on 9 August, Tepco began on 15 August before midday the full scale ground water pumping using some of the planned thirty 5-metre deep pipes whose installation has been completed. After 18 August, when all pipes will be completed, the pumping capacity will reach 60 ton/day. Since pumping began, the ground water level has declined by about 50 cm. Even after the ground solidifying work will be completed, up to 35 ton/day of ground water is expected to seep out to the sea through the solidified layer, so that a radical solution is still wanting.

 

[LabratSR]

From Ex-SKF - Fukushima I Nuke Plant: Alpha Nuclides Found in Condensed Water from Reactor 3's PCV Gas Control System

http://ex-skf.blogspot.com/2013/08/fukushima-i-nuke-plant-alpha-nuclides.html

 

[SteveElbows]

Any chance of some info about this japanese document regarding installation of permanent monitoring equipment for reactor 2? Again computer translation is not great which is why I ask, but it does sound like the survey revealed problems so they have to think again about this plan?

http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130814_13-j.pdf

 

[tsutsuji]

Any chance of some info about this japanese document regarding installation of permanent monitoring equipment for reactor 2? Again computer translation is not great which is why I ask, but it does sound like the survey revealed problems so they have to think again about this plan?

http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130814_13-j.pdf

01/03

02/03

03/03

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130819/index.html

1) The radiation alarm rang from 09:30 to a little after 10:00 AM on 19 August in front of the seismic-isolated building. Two workers who were waiting for the bus there were found to have been contaminated up to 13 Bq/cm², which is 3 times Tepco's internal standard. However they have no internal contamination. Tepco checked that the alarm rang as a consequence of rising cesium concentration in the air. The mist generator, which was suspected for the contamination of the 10 workers on 12 August, was not being used on 19 August.

2) Water was found leaking outside the dam surrounding tanks on the mountain side of unit 4. The leakage came from a rainwater exhaust pipe and was stopped by closing a valve. The radiation near the surface of water puddles (approximately 90 litre) was 100 mSV/hour. Tepco is investing the cause, suspecting that a contaminated water tank must somehow be leaking.

http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130819_03-j.pdf Seismic Isolated Building Dust monitor alarm (Japanese)

http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130819_05-j.pdf Leakage in H4 tank area (Japanese)

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130820/0515_kanri.html

Although the dam surrounding the tank area is designed to prevent contaminated water leakage, the valve equipping the rainwater exhaust pipe was left open, and leakage outside the dam could be stopped by closing the valve.

Tepco said "If we don't evacuate rainwater, we can't distinguish whether the water inside the dam is water leaked from the tanks or not. For that reason, the valve is usually open."

However, as it would be impossible to respond if a similar contaminated water leakage happened again, Tepco said it would study leakage detection and management methods.

The NRA said it is provisionally classifying the event as an International Nuclear Event Scale level 1 event.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130820/index.html One of the 26 tanks in the area, supposed to be filled with 1000 tons of water was found to contain only 700 tons. That means that 300 tons have leaked. This water is the output of the cesium removal process. Although it does not contain cesium, it contains strontium and the beta radiation is 80,000,000 Bq/l. Tepco will remove the Earth contaminated by the water leak and closely monitor the consequences.

http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130820_01-j.pdf Leakage in H4 tank area (Japanese)

 

[blab31]

NHK : "Although it does not contain cesium, it contains strontium and the beta radiation is 80,000,000 Bq/l."

If I read correctly, from your document - http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130820_01-j.pdf - Cs134 is still 46,000 Bq/l and Cs137 100,000 Bq/l, far higher than it should be after cesium removal systems.

I guess it's the usual TEPCO mistake, but japanese document shows 8x10E4 all beta, while english press release - http://www.tepco.co.jp/en/press/corp-com/release/2013/1229867_5130.html - is 8x10E-4 all beta. Same thing with cesium, 1x10E2 (japanese) versus 1x10E-2 (english).