Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[clancy688]

Me neither...

The problem lies with the source of information. Since speculation is officially forbidden by the board rules, we are only allowed to discuss official informations. Even so, the current discussions here are bending the rules quite heavily. I'm very thankful toward the moderators for giving us a little more discussion space than normally allowed by the rules.

But most of our informations come from TEPCO. It's obvious that there's no other source, Fukushima Daiichi is TEPCO's doing and it's their job to clean it up. Which probably means that, in case of real-time informations about plant status, TEPCO's going to be the source of 99,9% of all information, and that for the next thirty to forty years.

Therefore we can only discuss the things they give us. We cannot speculate or dismiss conservative or moderate looking informations as "false" and "lies" just because we don't trust TEPCO any more.
Working with biased informations won't give us the exact current status of the plant, but it will provide an overview and an overall bearing.
Working with speculations on the other hand is no scientific approach and won't give us any reasonable anwers. We'd probably get similar results by dicing the plant's status.

 

[Bandit127]

I am at times rather harsh towards nuclear industry. And I did post quite a number of my thoughts here. Even though this did upset a few pro-nuclear people, I was not banned and my posts were not deleted.

I am not picking on you Nikkom, but just using the last post in a thread that has seemingly got political. Although some good points have been made, please consider taking it elsewhere so that this thread can remain factual and a high quality resource of information for the rest of the world.

In fact, after all this time probably still the best resource.

 

[MJRacer]

True.

From pages 20 and 21 of http://www.iaea.org/inisnkm/nkm/pages/2011/NEMschool2011/topics/topic0/Fukushima Overview_Sekimura.pdf (Overview of the Accident in Fukushima Daiichi Power Plants by Naoto Sekimura).

Unit 2
B: O.P. +10.2m (Not Flooded)(Air-Cooled)

Unit 4
B: O.P. +10.2m (Not-Flooded)(Air-Cooled)

Unit 6
B: O.P. +13.2m (Not-Flooded)(Air-Cooled)

So, 3 EDGs were air-cooled and not-flooded. If one EDG was able to save Units 5 and 6, maybe the EDG in Unit 2 could have saved Units 1 and 2 and the EDG in Unit 4 could have saved Units 3 and 4. However, the electrical panels in Units 2 and 4 were flooded. Also, IIRC, one seawater pump was saved (Unit 6) and a submersible pump was improvised to save Unit 5. I don't think any of the seawater pumps for Units 1 and 4 were saved, but don't quote me on that.

Correction: All seawater pumps were submerged in the tsunami. Units 5 and 6 had been out of serviice for 2 and 7 months, respectively, at the time of the earthquake and, thus, the decay heat that needed to be removed would have been much less than if they had been operating. The temporary seawater pump that was installed to provide cooling for Units 5 and 6 did not become operational for 8 days or until March 19.

 

[duccio]

It came to my mind that containment is great for protecting from radiations and from the "banging" of water into steam in case of loss of pressure, but it gets on the way of cooling the fuel once it's at atmospheric pressure. On top of RPV there is a pool full of water that - considering the height of the fuel bundle - should be 4+4 meters deep. In case of accident wouldn't it be easier to just open the top of the RPV before the meltdown and let the water flow in and evaporate at 100 degree with no hydrogen release? The downside is quite clear (no shielding in case of meltdown) but from the different reports I read, it was really difficult for the men on the field to connect the hoses to the proper pipes (submerged/damaged/on pressure... ). That way they would just have to fill the pool with whatever water they would find.

I'm defiinitely no expert and maybe I said the silliest thing on Earth, but I would really like to understand what's missing in my reasoning :/

 

[etudiant]

Your idea is a core element in the design of the newer AP1000 reactors just approved by the US NRC.
The problem was that the reactors at Fukushima were difficult to depressurize because the valves needed power to be opened. So a bad accident was made much worse.

 

[mheslep]

It came to my mind that containment is great for protecting from radiations and from the "banging" of water into steam in case of loss of pressure, but it gets on the way of cooling the fuel once it's at atmospheric pressure.

That's a very good point.

 

[Astronuc]

It came to my mind that containment is great for protecting from radiations and from the "banging" of water into steam in case of loss of pressure, but it gets on the way of cooling the fuel once it's at atmospheric pressure. On top of RPV there is a pool full of water that - considering the height of the fuel bundle - should be 4+4 meters deep. In case of accident wouldn't it be easier to just open the top of the RPV before the meltdown and let the water flow in and evaporate at 100 degree with no hydrogen release? The downside is quite clear (no shielding in case of meltdown) but from the different reports I read, it was really difficult for the men on the field to connect the hoses to the proper pipes (submerged/damaged/on pressure... ). That way they would just have to fill the pool with whatever water they would find.

I'm defiinitely no expert and maybe I said the silliest thing on Earth, but I would really like to understand what's missing in my reasoning :/

The problems arise from the Mark I containment, which is certainly non-optimal for the scenario that evolved at Fukushima.

The accident was 'beyond design basis' and the damage due to the tsunami was extensive beyond any scenario for which the utility had planned, so they were left essentially defenseless.

The plant staff had so little time to respond, and the response was muted with complete loss of both off-site AND on-site power, such that it became a cascade of failures that culminated in severe damage to three reactors.

After Mark I, there are Mark II and Mark III containments of later generation BWR systems. Modern BWR systems, e.g., ABWR and ESBWR, are even more robust.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120208/index.html Unit 2 thermometer:

8 February 05:00 : 66.7°C
8 February 10:00 : 68°C

 

[zapperzero]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120208/index.html Unit 2 thermometer:

8 February 05:00 : 66.7°C
8 February 10:00 : 68°C

It's quite frustrating. We only have this one indication that something is not as it should be. But what? Where? What to do about it?

What do we know about the water level in the RPV? Nothing? I have two conflicting theories as to why the other two sensors' indications are in lockstep, and I can't choose between them.

 

[Jim Lagerfeld]

It came to my mind that containment is great for protecting from radiations and from the "banging" of water into steam in case of loss of pressure, but it gets on the way of cooling the fuel once it's at atmospheric pressure. On top of RPV there is a pool full of water that - considering the height of the fuel bundle - should be 4+4 meters deep. In case of accident wouldn't it be easier to just open the top of the RPV before the meltdown and let the water flow in and evaporate at 100 degree with no hydrogen release? The downside is quite clear (no shielding in case of meltdown) but from the different reports I read, it was really difficult for the men on the field to connect the hoses to the proper pipes (submerged/damaged/on pressure... ). That way they would just have to fill the pool with whatever water they would find.

I'm defiinitely no expert and maybe I said the silliest thing on Earth, but I would really like to understand what's missing in my reasoning :/

I thought you might be interested in this tidbit from the Washington Post:

"NRC e-mails reveal disagreement about how to advise the Japanese. The NRC staff chafed at some unorthodox advice coming from an ad hoc group of scientists assembled by Energy Secretary Steven Chu. Famed physicist Richard Garwin, one of Chu’s group, proposed setting off a controlled “shaped” explosion to break through the concrete shield around the primary steel containment structure to allow cooling water to be applied from the outside."

http://www.washingtonpost.com/busin...-and-tsunami/2012/01/09/gIQA2ll6uQ_print.html

 

[tsutsuji]

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120208_05-e.pdf latest Fukushima Daiichi unit 2 upper bottom head temperature data
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120208_06-e.pdf latest Fukushima Daiichi unit 2 upper bottom head temperature plot
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120208_07-e.pdf Fukushima Daiichi unit 2 charcoal filter nuclides, February 6
http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120208_06-j.pdf (not yet translated into English) Fukushima Daini restoration plan. According to the schedule on page 22 (23/35), the measures to "secure one step further cold shut down" by "restoring the main equipments" will be completed within the first half of 2012 at units 3 and 4 and within the second half of 2012 at units 1 and 2.

 

[Cire]

It's quite frustrating. We only have this one indication that something is not as it should be. But what? Where? What to do about it?

What do we know about the water level in the RPV? Nothing? I have two conflicting theories as to why the other two sensors' indications are in lockstep, and I can't choose between them.

There are several reasons why the temperature could be changing. None of which are dire.

1. The flow of water into and out of the RPV may have changed due to settling or relocation of whatever is left inside of the reactor. I personally believe the core is still in the RPV's albeit scattered and down at the bottom.

2. The fluctuations could be purely electrical in nature (ie. the sensor is failing/failed ) the amplifiers have lost their cold junction or corrosion has attacked the thermocouple or any of its wires/connections. The erratic swings in values would suggest this.

3. If the RPV's had reached the temperatures that have been speculated on the magnetically coupled thermocouples would have dropped off the RPV and would be hanging by their wires and wouldn't reflect actual RPV temperatures any longer.

4. A single sensor data set doesn't make a trend.

 

[Azby]

I thought you might be interested in this tidbit from the Washington Post:

"NRC e-mails reveal disagreement about how to advise the Japanese. The NRC staff chafed at some unorthodox advice coming from an ad hoc group of scientists assembled by Energy Secretary Steven Chu. Famed physicist Richard Garwin, one of Chu’s group, proposed setting off a controlled “shaped” explosion to break through the concrete shield around the primary steel containment structure to allow cooling water to be applied from the outside."

http://www.washingtonpost.com/busin...-and-tsunami/2012/01/09/gIQA2ll6uQ_print.html

Thanks, Jim. I'm passing this link on. The fact that the article links to so many of the original emails is unusual and very helpful.

Azby

 

[zapperzero]

There are several reasons why the temperature could be changing. None of which are dire.

1. The flow of water into and out of the RPV may have changed due to settling or relocation of whatever is left inside of the reactor. I personally believe the core is still in the RPV's albeit scattered and down at the bottom.

2. The fluctuations could be purely electrical in nature (ie. the sensor is failing/failed ) the amplifiers have lost their cold junction or corrosion has attacked the thermocouple or any of its wires/connections. The erratic swings in values would suggest this.

3. If the RPV's had reached the temperatures that have been speculated on the magnetically coupled thermocouples would have dropped off the RPV and would be hanging by their wires and wouldn't reflect actual RPV temperatures any longer.

4. A single sensor data set doesn't make a trend.

A thermocouple hanging off should not show higher temps. Generally speaking, the fact that temps have dropped quite slowly and uniformly after injected water volume was increased says that there's probably nothing wrong with the sensor.

The water may have simply stopped flowing that way. Other things could have happened. Net result is more water in the basement and additional work for the filtration system.

It's frustrating to know that we won't know for years, is all. At least, there apparently isn't Xe or I so...

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120209/index.html On 9 February, Tepco is putting a remote controlled camera underwater in unit 4's pool to check the fuel. Similar underwater camera surveys will also be performed several times in March to check the fallen building debris and see if the fuel is damaged. Tepco plans to start removing the fuel by March 2014.

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120209_05-j.pdf The hoses are perforated by chigaya grass (imperata cylindrica).

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120209_06-j.pdf As it had declined, unit 2's feed line flow rate was adjusted from 6.4 to 6.8 m³/hour at 09:47 on 9 February. The core spray flow rate remains unchanged at 6.8 m³/hour.

http://mdn.mainichi.jp/mdnnews/business/news/20120208p2g00m0bu116000c.html "Power firms to install vent facilities in all domestic nuclear plants" (...) "will have a filtering function to remove radioactive substances from vapor before releasing"

 

[tsutsuji]

http://www.tepco.co.jp/tepconews/library/movie-01j.html (last tab) Unit 4 underwater video
http://tepco.webcdn.stream.ne.jp/www11/tepco/download/120210_02j.zip (download)
http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120210_03-j.pdf Diagram

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120210/index.html The visibility was 5 metre. No fuel damage or deformation was observed.

 

[zapperzero]

http://mdn.mainichi.jp/mdnnews/business/news/20120208p2g00m0bu116000c.html "Power firms to install vent facilities in all domestic nuclear plants" (...) "will have a filtering function to remove radioactive substances from vapor before releasing"

A sudden outbreak of common sense, I think it's called.

 

[etudiant]

A sudden outbreak of common sense, I think it's called.

I thought all these plants already have hardened vents.
Are we talking about improved vent actuation methods, that work even if power is lost, or are we talking about filtered emergency venting such as is in place in some Finnish reactors that rmattila has given us helpful insight on.

 

[tsutsuji]

Cabinet investigation committee:

http://icanps.go.jp/eng/120125ShiryouEng.pdf Investigation items for the Final Report

The international experts are invited to participate in a tour to the Fukushima Daiichi NPS on February 23 (Thursday). Please be aware that we will not make any press arrangement for the tour. The meetings with the Investigation Committee will be held on the 24th and 25th of February (Friday and Saturday) at the Keio Plaza Hotel in Shinjuku. The meetings, conducted with simultaneous interpretation, will be open to the press. After the session on February 25 (Saturday), the Investigation Committee and international experts will attend a press conference.
http://icanps.go.jp/eng/120125KaikennaiyouEng.pdf

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120211/index.html Unit 2 Thermometer:

8 February : 64.1°C
10 February 09:00 : 71.1°C
11 February 03:00 : 71.3°C
11 February 09:00 : 71.3°C

The other two thermometers have further dropped to around 35°C. Tepco said "we are watching the situation. If the temperature rises further than this, we will raise the injection rate".

http://www.nikkei.com/news/category...09180EAE2E2E2;at=DGXZZO0195583008122009000000 :

11 February 17:00 : 69.5°C
11 February 18:00 : 71.2°C

The injection rate was raised by 1 m³/hour to 14.6 m³/hour at 22:45 on 11 February.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120212/index.html :

11 February 23:00 : 74.9°C
12 February 00:00 : 71.1°C
12 February 01:00 : 69.5°C
12 February 02:00 : 71.9°C

 

[swl]

4. A single sensor data set doesn't make a trend.

I find your interpretation of statistics enlightening.

In other news, TEPCO has increased the reactor-2 cooling water flow to the highest rate since the earthquake. Could they have done this in response to the recent 75 degree indication? And since they increased the flow rate at 15 minutes prior to the public hourly data point, I wonder what the TC indicated prior to the flow increase.

 

[nelle]

I am not surprised by this news.
I have been graphing the hourly temperature data since they released it.

You can see the data here (although it hasn't yet been updated past 4pm on Feb 11): http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/2u_temp2-e.pdf
and the drawing with the location of the 3 temp sensors in question here: http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/2u_temp-keisoku-e.pdf

If this sensor is functioning, and TEPCO seems to think it is, considering the volumes of cooling water they are injecting.

Here are my two charts
Feb 1 thru Feb 10 and Feb 4 thru Feb 11 at 4pm

 

[elektrownik]

2/12 10:00 78.3

 

[tsutsuji]

In December, Tepco released a study in which they calculated an estimate of the proportion of uncovered fuel in each unit. I am curious to know how this estimate is changing for unit 2 with the present temperature values.

http://www.yomiuri.co.jp/science/news/20120212-OYT1T00271.htm?from=main2&from=os4 :

12 February 14:20 82°C

At 15:30 Tepco increased the injection rate by 3 tons/hour to 17.4 tons/hour. No xenon detected.

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120212_02-j.pdf I can't find the 74.9°C value for 11 February 23:00 here. Instead they wrote "2/11 23:00 71.2".

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120212_03-j.pdf Here they wrote "2/11 23:00 74.9"

http://www.ustream.tv/channel/%E3%83%95%E3%83%AA%E3%83%BC%E3%82%B8%E3%83%A3%E3%83%BC%E3%83%8A%E3%83%AA%E3%82%B9%E3%83%88-%E5%B2%A9%E4%B8%8A%E5%AE%89%E8%BA%AB%E3%81%AB%E3%82%88%E3%82%8Bustream Video of Tepco's press conference on 12 February afternoon. Junichi Matsumoto: "The probability of a temperature indication failure is high".

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120212_05-j.pdf (temperature plot) The amplitude of vibration/instability has started becoming greater after 12:00 noon on 12 February.

 

[elektrownik]

"The temperature at the No.2 reactor of the Fukushima Daiichi nuclear power plant keeps rising even after the injection of more cooling water on Saturday night. [...]
TEPCO is set to dump in boric acid to prevent any nuclear criticality later on Sunday and increase the volume of cooling water by 3 tons per hour.

Under new guidelines, the company must keep reactor temperatures at 80 degrees or below, given thermometers’ margin of error of up to 20 degrees."
http://www3.nhk.or.jp/daily/english/society.html

 

[elektrownik]

Reactor 2 90C now

 

[Shinjukusam]

Reactor 2 90C now

Where are you getting that from? NHK is only reporting the highest being 82 at 14:20 Japan time.

 

[elektrownik]

Where are you getting that from? NHK is only reporting the highest being 82 at 14:20 Japan time.

NISA press conference, it was live some time ago on ustream

 

[Shinjukusam]

NISA press conference, it was live some time ago on ustream

Much obliged.

 

[Yamanote]

This can also be seen already in the post from tsutsuji-san:

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120212_05-j.pdf (temperature plot) The amplitude of vibration/instability has started becoming greater after 12:00 noon on 12 February.