Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[tsutsuji]

http://www3.nhk.or.jp/news/html/20120206/t10015820341000.html Unit 2 thermometer : 71°C at 11 AM, and 69.2 at 5 PM on 6 February. Tepco plans to further increase the water injection rate by 3 tons/hour in the night of 6 February. Judging from xenon concentrations, Tepco says no recriticality is occurring.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120206/1915_senmonka.html Hiroaki Suzuki of the Institute of Applied Energy mentions two possible causes : the water flow changed after injection was restarted in January, or a piece of fuel fell down from above to a location close to the thermometer.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120206_02-e.pdf the data of the three RPV bottom thermometers

 

[zapperzero]

And from tepco press conference:
"Tepco announced they are going to add 960 Kg of boric acid tonight in JST."

Well, well. The plot thickens. So, if they do it and the temperature change is reversed, we could then conclude re-criticality?

 

[elektrownik]

del this

 

[tsutsuji]

http://sankei.jp.msn.com/science/news/120207/scn12020701100002-n1.htm Boric acid injection was started in the early morning of 7 February.

 

[jmelson]

And from tepco press conference:
"Tepco announced they are going to add 960 Kg of boric acid tonight in JST."

Oh MAN! This is a scary development! And, in the reactor whose condition we seem to know the least about.

Jon

 

[jmelson]

http://www3.nhk.or.jp/news/html/20120206/t10015820341000.html Unit 2 thermometer : 71°C at 11 AM, and 69.2 at 5 PM on 6 February. Tepco plans to further increase the water injection rate by 3 tons/hour in the night of 6 February. Judging from xenon concentrations, Tepco says no recriticality is occurring.

If there's no recriticality, why the HELL are they adding boric acid?

Jon

 

[Cire]

If there's no recriticality, why the HELL are they adding boric acid?

Jon

It's called being proactive instead of being reactive.

 

[Borek]

Truth is, for some people whatever they do, they do wrong.

If they add boric acid, it means they are adding it because they know there is a recriticality, they just doesn't tell anyone. If they don't add boric acid, why the hell they don't add this if there is an obvious recriticality? It is their fault both ways.

 

[tsutsuji]

http://www.bloomberg.co.jp/news/123-LYZRMA6JTSE801.html Boric acid was added from 00:19 to 03:20 AM on 7 February. The core spray system injection rate was increased nearly two-fold from 04:24 AM. Temperatures:

6 February 17:00 : 69.2°C
6 February 23:00 : 69.9°C
7 February 05:00 : 72.2°C
7 February 07:00 : 70.1°C

 

[mheslep]

Truth is, for some people whatever they do, they do wrong.

If they add boric acid, it means they are adding it because they know there is a recriticality, they just doesn't tell anyone. If they don't add boric acid, why the hell they don't add this if there is an obvious recriticality? It is their fault both ways.

Sshhh. You could put the internet out of business.

 

[jim hardy]

duh,,,

if you've been adding water you're diluting the boric acid that you put in there a while ago.
better toss in a few spoonfuls now and then .

 

[joewein]

The only usable diesel generator (Unit 6B) was apparently in a separate building (the Diesel Generator Building). (See Figure II-2-25, page II-77 for location of building and inset in Figure II_2-20, page II-73 for schematic showing elevation.)

Otherwise, Units 5 and 6 might have been lost also.

The difference was that this one was air-cooled. So when the cooling water intake was knocked out, the other EDGs in units 5 and 6 became unusable despite not being flooded, but this could keep going and save the day.

 

[MJRacer]

The difference was that this one was air-cooled. So when the cooling water intake was knocked out, the other EDGs in units 5 and 6 became unusable despite not being flooded, but this could keep going and save the day.

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.

 

[swl]

Truth is, for some people whatever they do, they do wrong.

If they add boric acid, it means they are adding it because they know there is a recriticality, they just doesn't tell anyone. If they don't add boric acid, why the hell they don't add this if there is an obvious recriticality? It is their fault both ways.

Sounds like they are doing the right thing in this case. The temperature rose, they checked the reactor gasses, and now they have responded by injecting boric acid. I would be interested to learn what isotopes were detected in the gas analysis.

 

[zapperzero]

Truth is, for some people whatever they do, they do wrong.

If they add boric acid, it means they are adding it because they know there is a recriticality, they just doesn't tell anyone. If they don't add boric acid, why the hell they don't add this if there is an obvious recriticality? It is their fault both ways.

You know... the only thing that bothers me about the same is the equal and opposite reaction from those (not you, obviously) who want to believe there is no possibility of anything going wrong.

"Doubling the core spray volume and adding boric acid? An excess of precaution. Nothing to see here, move along."

But there is something to see. That thermo-couple is working just fine, we just don't know what's heating it up. I asked the question about recriticality not because I like tragedies, but because I really wanted to know what you guys think!

Evidently, I was not the only one to ask that question, as TEPCO has been checking for xenon (a fact of which I was unaware at the time):

http://www.businessweek.com/news/2012-02-07/tepco-injects-boric-acid-into-reactor-as-temperatures-rise.html

 

[tsutsuji]

http://www.bloomberg.co.jp/news/123-LYZRMA6JTSE801.html Boric acid was added from 00:19 to 03:20 AM on 7 February. The core spray system injection rate was increased nearly two-fold from 04:24 AM. Temperatures:

6 February 17:00 : 69.2°C
6 February 23:00 : 69.9°C
7 February 05:00 : 72.2°C
7 February 07:00 : 70.1°C

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120207/index.html The core spray system flow rate was increased by 3 tons/hour at around 4 AM on 7 February. Total flow rate: 13.5 tons/hour. Tepco is surveying with deep care the effects of the flow rate increase over the next 24 hours or so.

http://www.nikkei.com/news/headline...19695E2E5E2E3E38DE2E5E2E0E0E2E3E0E2E2E2E2E2E2 :
7 February 08:00 : 71.4°C
7 February 10:00 : 69°C

http://www.nikkei.com/news/headline...19695E2E5E2E6948DE2E5E2E0E0E2E3E09180EAE2E2E2 :
7 February 13:00 : 71.5°C
No xenon was detected on 7 February.

http://sankei.jp.msn.com/science/news/120207/scn12020714230004-n1.htm
7 February 17:00 : 68.5°C (and the other two thermometers have dropped to around 41°C)

http://www.tokyo-np.co.jp/article/national/news/CK2012020702000039.html The core spray system had been interrupted for 6 hours on 26 January in order to change a pump. Tepco says the way the water is flowing might have changed at that time, no longer reaching the areas close to the fuel as well as before. Institute of Applied Energy department head Masanori Naito said some fuel might have fallen into the RPV bottom and formed a small heap.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120207_06-e.pdf Diagram showing the 3 thermometers located at 0°, 135° and 270° of angle. The hot one is the one located at 0° on the mountain side.

 

[dezzert]

Truth is, for some people whatever they do, they do wrong.

If they add boric acid, it means they are adding it because they know there is a recriticality, they just doesn't tell anyone. If they don't add boric acid, why the hell they don't add this if there is an obvious recriticality? It is their fault both ways.

No, actually the truth is if you post a pro-nuclear non technical blurb on this forum its OK, but an anti-nuclear non technical blurb is instantly removed.

And you can delete me from this forum cause it doesn't really deal with technical issues, only what Tepco feeds you. There are incredibly important technical issues that this forum avoids. Unless of course its a pro nuclear view.

Brilliant

 

[Cire]

No, actually the truth is if you post a pro-nuclear non technical blurb on this forum its OK, but an anti-nuclear non technical blurb is instantly removed.

And you can delete me from this forum cause it doesn't really deal with technical issues, only what Tepco feeds you. There are incredibly important technical issues that this forum avoids. Unless of course its a pro nuclear view.

Brilliant

To directly address your question (was there one?). I've found this forum to be moderated quite well. This topic for the most part remains technical and a great source of information on the state of the plants.

For or against the use of nuclear power really isn't relevant to the discussion here is it?

 

[etudiant]

No, actually the truth is if you post a pro-nuclear non technical blurb on this forum its OK, but an anti-nuclear non technical blurb is instantly removed.

And you can delete me from this forum cause it doesn't really deal with technical issues, only what Tepco feeds you. There are incredibly important technical issues that this forum avoids. Unless of course its a pro nuclear view.

Brilliant

I do not think your comment about the scope of this forum being restricted to the TEPCO data releases is at all correct. Nor have I seen the kind of selective message purging you suggest.
It would be more helpful to list the top technical issues that you believe this forum refuses to discuss.

 

[nikkkom]

No, actually the truth is if you post a pro-nuclear non technical blurb on this forum its OK, but an anti-nuclear non technical blurb is instantly removed.

And you can delete me from this forum cause it doesn't really deal with technical issues, only what Tepco feeds you. There are incredibly important technical issues that this forum avoids. Unless of course its a pro nuclear view.

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.

 

[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"