Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[radio_guy]

There were aerial thermal images released fairly early on, back when they lacked other means to try to establish a rough idea of temperature of pools & reactors.

I did see those from back in march, I believe from satellite and I should have clarified a bit.

The line of thinking when cameras were mentioned was inspecting what was going on with the core, and I think closer than satellite level thermal imaging would be a great way to figure it out, and give some ideas where and what shape the core or what's left of it would be in.

on adding the camera through the water inlet:I suspect that's possible and I was just not thinking in terms of large scale length of controls. I think bore scope and 100'-200' comes to mind.

 

[seeyouaunty]

There were aerial thermal images released fairly early on, back when they lacked other means to try to establish a rough idea of temperature of pools & reactors.

The attached jpg shows the thermal images you mention. I can't remember where i got the picture from, its been sitting on my desktop for a while.

 

[SteveElbows]

Well, there's a pipe. When they put water into it, the water ends up in the RPV. There's your access.

Is it fair to think of it as a simple pipe though? I tend to imagine it as them pumping water into existing systems, and such systems may involve far more than piping. There may be multiple points where any probe would meet something other than easy to navigate pipe, barriers to entry that it won't get round but water will.

 

[zapperzero]

Is it fair to think of it as a simple pipe though? I tend to imagine it as them pumping water into existing systems, and such systems may involve far more than piping. There may be multiple points where any probe would meet something other than easy to navigate pipe, barriers to entry that it won't get round but water will.

There are, for sure. Kinks and bends and valves and all that. Some borescopes are steerable just for this reason.

 

[razzz]

Here's an interesting hypothesis regarding the spent fuel pools and explosions:

http://tec-sim.de/images/stories/fusfpfail.pdf

Well that was interesting. It was all the fuel pools fault because unknown check-valves failed after a loss of power turning the feed lines into siphoning lines lowering the water levels until air reaction with fuel rod created hydrogen that eventually exploded disrupting the remaining water in the pools to create an airlock (air bubble) in the plumbing thus halting the siphoning action. This hypothetical scenario happens 4 times (4 SFP).

They completely ignored loss of coolant in the RPV probably glowing white hot cracking itself or connections and blowing seals. Note their 8-1 drawing shows vents above the drywell concrete sectional cap near floor level.

Also never discussed why SFP 4 fuel assemblies appear undamaged while they describe uncovered fuel assemblies burning like torches.

 

[v13]

Not being an expert, I want to try to add something to the conversation:

It seems to me (based on what I read here) that all reactors suffered somehow the same or similar problem, but one of them did not explode. So the key to understanding what happened should be reactor #2. It should be much easier for tepco to study #2 since it hasn't exploded.

Also, using that thought, the thermal images show that the smaller building at the top of reactor #2 (behind the "NHK WORLD" logo) is also warm (just like the sea). Don't know if this helps.

 

[StrangeBeauty]

...study #2 since it hasn't exploded.

Yes, it did explode.

I suggest going (way) back in the thread and reading, or at least going here to get a synopsis:
http://en.wikipedia.org/wiki/Fukushima_I_nuclear_accidents

 

[NUCENG]

OK here is the most interesting data on this subject. I am choosing reactor 2 because reactor 3 has a very annoying gap of data from around 3pm-3.30pm.

Pages 10 and 28 of the following document show what the RCIC was doing at reactor 2 between 14:41 and 15:47:

http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_6_Katogensho2.pdf

I have attached just a couple of the charts to this post to give you a taste of what I am looking at without having to look at the whole pdf if you don't want to. Anybody prepared to have a stab at describing what this shows?

pp1,2.APRM Average Power Range Monitors 6 channels show scram at around 1446 hr
p3. Narrow Range and Wide Range Reactor water level shows shrink due to void collapse at scram followed by level recovery due to feedwater control system opening wide to recover level. Main Steam Isolation valve closure then bottled up the reactor and SRV cycling to maintain pressure within ipen and closed setpoints.
pp 4,5 Core Spray - electrical noise on p4. this system should not have any flow at high pressure. p5 is as expected.
pp 6, 7. High Pressure Coolant Injection not used.
p 8. residual heat removal RHR pumps A and C started at 1508 hr probably in containment cooling mode with suction on torus. Would need valve operation information to be certain.
p 9. RHR service water pumps A and C start to support containment cooling mode. (cooling water to heat exchanger)
p10 Reactor Core Isolation Cooling RCIC started automatically on low reactor water level at 1450 but was turned off manually to prevent overfilling RPV (RWL does not appear to have reached high level trip on pp 3,4. Normal operating practice. RCIC restarted at 1502 at approx 27 l/s injection to vessel from condensate storage tank.
p 11. not sure but top graph may be low level enable signal for RCIC.
p 12,13. EDG 2A and 2B started on LOPA Loss of Offsite Power. EDG 2A was loaded about 1506 hr.
p 14 LOPA at 1447, No loss of coolant accident LOCA signal
p 15. Narrow range and wide range reactor pressure. After scram and void collapse pressure dropped, After Main steam isolation valve closure pressure rose to SRV cycling setpoint.
p 16 SRV F was cycling. gradual change in cycling rate shows decay heat decreasing.
p 17 Main steam isolation valve closure at 1448
p 18. Probably main steam flow rate t/hr showing MSIV closure.
pp 19-20 nothing to note
p 21. RWL slow change up to 1800 mm and dow to 300 mm uder operation of RCIC and SRVs
pp 22-25.nothing significant to note
pp 26, 27. Loss of AC trips RHR and RHRSW pumps at 1537.
p 28. RCIC flow dialed back due to increasing RPV level and RCIC secured at 1528. Restarted at 1540 at 31 l/s.
p 29. EDG 2A tripped at 1537. EDG 2B tripped at 1542 due to tsunami, flooding.
pp 30-32. nothing to note
p 33. RPV pressure continues to cycle on ERV setpoint
p 34. SRV F continues to cycle.
p. 35. Nothing significant.

 

[NUCENG]

They were not reported missing before the explosion. They were reported missing on March 16, the day after the explosion, and clearly the press release said they were missing due to the explosion.

http://www.theaustralian.com.au/news/breaking-news/cracked-roof-two-missing-workers-at-fukushima-reactor-no4/story-fn3dxity-1226022252864

They were found about two weeks later, dead because the lost blood and went into shock.

http://www.businessinsider.com/fukushima-two-missing-workers-found-dead-2011-4

There does seem to be an effort after the fact to say they were a victim of the Tsunami, not the explosion - wonder why?

The following Press release was before the first explosion:
Press Release (Mar 12,2011)
Plant Status of Fukushima Daiichi Nuclear Power Station (as of 0AM March 12th )


All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.

Unit 1 (shut down due to earthquake)
- Reactor was shut down and nuclear steam is cooled by the isolation condenser.
- Currently, there is a possibility of a release of radioactive materials
due to decrease in reactor water level. Therefore, the national government
has instructed evacuation for those local residents within 3km radius of
the periphery and indoor standby for those local residents between 3km and
10km radius of the periphery.

Unit 2 (shut down due to earthquake)
- Reactor was shut down and although nuclear steam had been cooled by the
Reactor Core Isolation Cooling system, the current operating status is
unclear. However, reactor coolant level can be monitored by a temporary
power supply and the level is stable.
- Currently, there is a possibility of a release of radioactive materials
due to decrease in reactor water level. Therefore, the national government
has instructed evacuation for those local residents within 3km radius of
the periphery and indoor standby for those local residents between 3km and
10km radius of the periphery.

Unit 3 (shut down due to earthquake)
- Reactor was shut down and is cooled by the Reactor Core Isolation Cooling
system.
- Currently, we do not believe there is any reactor coolant leakage inside
the reactor containment vessel.

Unit 4 (shut down due to earthquake)
- Reactor has been shut down and sufficient level of reactor coolant to
ensure safety is maintained.
- Currently, we do not believe there is any reactor coolant leakage inside
the reactor containment vessel.

Unit 5 (outage due to regular inspection)
- Reactor has been shut down and sufficient level of reactor coolant to
ensure safety is maintained.
- Currently, we do not believe there is any reactor coolant leakage inside
the reactor containment vessel.

Unit 6 (outage due to regular inspection)
- Reactor has been shut down and sufficient level of reactor coolant to
ensure safety is maintained.
- Currently, we do not believe there is any reactor coolant leakage inside
the reactor containment vessel.

We measured radioactive materials inside and outside of the periphery of
the nuclear power station (outdoor area) by monitoring car and confirmed
that there was no difference from ordinary level.

No radiation impact to the external environment has been confirmed.
We will continue to monitor in detail the possibility of radioactive material
being discharged from exhaust stack or discharge canal.

Two subcontract workers were injured in the nuclear power station premise.
One with a broken bone was transported to the hospital by an ambulance and
the other by a company car.
Further, there are 2 TEPCO employees whose presence has not been confirmed.

We are presently checking on the site situation of each plant while keeping
the situation of aftershock and Tsunami in mind.

 

[SteveElbows]

pp1,2.APRM Average Power Range Monitors 6 channels show scram at around 1446 hr...

Excellent, thanks for the detail, much appreciated. I am not going to pretend to understand every aspect of that but its great to see it explained and at least a proportion of it sinks into my mind.

So would I be right to think that, just looking at that data, things went ok in the time period covered? My presumption is that most of the data for 2 & 3 at this early period does not tell a tale of woe or of bad failures, but I wanted to learn more about what a 'normal' post-SCRAM & grid power loss event would look like, and I wanted to rule out any of the more interesting patterns on the graphs being tales of problems.

So thanks to you and the others who gave early feedback about this stuff, I will try to build upon this and get a proper understanding of these systems.

Can I ask whether you have looked at the control rod data that was released as part of this same 'data from the time of the earthquake & tsunami' bundle the other day? I could understand some of it, and again there were a couple of instances where it was showing the number -99 or the word BAD, and I wasnt sure whether this was a sign that there were problems at some stage with control rods, or whether this kind of data blip is to be expected under the circumstances, or whether I was reading it wrong. Let me find the document that I am talking about and I will post again on this subject.

 

[NUCENG]

I think that it's oversimplified to say the roofs would still have been there, many other things would have been there i think... (of course I'm talking about the other reactors than just N°1).

Heavy damages to the structures and all the equipements around have considerably increased the difficulties for workers around to restore or contain the situation...

This venting mess (with all the problems that occurred on the vent system) is a good part of the current situation IMO. Not the initial cause of course.

Yes it would be oversimplified to say the roofs would still be there. That's why I did NOT say they would still be there. I said I didn't know but MAYBE they would still be there. MAYBE not, but delayed venting surely didn't make the explosions less likely. Fair enough?

 

[PietKuip]

I did see those from back in march, I believe from satellite and I should have clarified a bit.

The line of thinking when cameras were mentioned was inspecting what was going on with the core, and I think closer than satellite level thermal imaging would be a great way to figure it out, and give some ideas where and what shape the core or what's left of it would be in.

on adding the camera through the water inlet:I suspect that's possible and I was just not thinking in terms of large scale length of controls. I think bore scope and 100'-200' comes to mind.

I collected some thermal images here:
http://www.flickr.com/photos/26255918@N08/sets/72157626384577079/detail/

The were taken from high up, but not a satellite. It was a Japanese army helicopter. They stopped at the end of April.

Yes, these things are not too big to drive around on a small robot: http://commons.wikimedia.org/wiki/Category:NEC_Thermo_Shot

 

[NUCENG]

Excellent, thanks for the detail, much appreciated. I am not going to pretend to understand every aspect of that but its great to see it explained and at least a proportion of it sinks into my mind.

So would I be right to think that, just looking at that data, things went ok in the time period covered? My presumption is that most of the data for 2 & 3 at this early period does not tell a tale of woe or of bad failures, but I wanted to learn more about what a 'normal' post-SCRAM & grid power loss event would look like, and I wanted to rule out any of the more interesting patterns on the graphs being tales of problems.

So thanks to you and the others who gave early feedback about this stuff, I will try to build upon this and get a proper understanding of these systems.

Can I ask whether you have looked at the control rod data that was released as part of this same 'data from the time of the earthquake & tsunami' bundle the other day? I could understand some of it, and again there were a couple of instances where it was showing the number -99 or the word BAD, and I wasnt sure whether this was a sign that there were problems at some stage with control rods, or whether this kind of data blip is to be expected under the circumstances, or whether I was reading it wrong. Let me find the document that I am talking about and I will post again on this subject.

I am trying to catch up. What is the link? All I looked at so far was the unit 2 data you posted a link for.

 

[ihatelies]

Two subcontract workers were injured in the nuclear power station premise.
One with a broken bone was transported to the hospital by an ambulance and
the other by a company car.
Further, there are 2 TEPCO employees whose presence has not been confirmed.

We are presently checking on the site situation of each plant while keeping
the situation of aftershock and Tsunami in mind.

So did they find them, then lose them again? Because 4 days later they said this:

During a news conference, the agency said the workers, whose names were not released, were in the turbine area of the No.4 reactor when the blast occurred. The Fukushima plant had been damaged after Friday's earthquake and tsunami.

http://www.theaustralian.com.au/news/breaking-news/cracked-roof-two-missing-workers-at-fukushima-reactor-no4/story-fn3dxity-1226022252864

And two weeks later they found them dead of internal bleeding in the turbine basement. I thought this an interesting cause of death, because they could have said they died of blast damage from the explosion, and no one would have given it a second thought, however internal bleeding likely came from some other cause.

 

[SteveElbows]

I am trying to catch up. What is the link? All I looked at so far was the unit 2 data you posted a link for.

OK the link to the japanese page which links to all the pdf's is this one, I haven't noticed whether its available in english yet:

http://www.tepco.co.jp/nu/fukushima-np/index10-j.html

Some of it is presented in an infuriating way, and some of the files are rather large.

Section 3 has documents which relate to control rods and some other stuff mixed in.

For example this is the file for reactor 1:

http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_3_Keihou1.pdf

It starts with a lot of printed logs that get very busy when the earthquake hits. Later in the document there are some tables of data that are presented in an annoying way. Finally after many pages the control rod-related data starts, and is presented in several different ways. The report formats varies considerably between reactors, some have more japanese than others, and some reactors have more snazzy visualisations of the control rod positions and what looks like other important reactor core data. Lots of the data is repetitive as it covers the normal operating hours before earthquake.

In any case, I presume that nothing bad happened to control rods, but as there are a few glitches in the data at certain moments in time, Id love someone knowledgeable to review this. For example with reactor 1 data there is a bunch of numbers but at one brief point the word BAD features. Also what looks like a 15:00 visualisation of the rods all showing the -99 value. The -99 one is on nearly the last page of the document, and is somewhat obscured by being printed in the same place on the same page as another type of data. I expect its nothing/normal but I just want to be more certain.

 

[MiceAndMen]

They completely ignored loss of coolant in the RPV probably glowing white hot cracking itself or connections and blowing seals. Note their 8-1 drawing shows vents above the drywell concrete sectional cap near floor level.

I don't see a drawing in there labeled "8-1" but it sounds like you're talking about page 18. The drawing that shows vents directly from the drywell to the refueling floor originated with the Areva presentation that came out weeks ago. See page 20

http://www.fairewinds.com/sites/default/files/AREVA%20Fukushima.pdf

The AREVA presentation has gotten a lot of attention here and elsewhere (mostly elsewhere) but that drawing continually escapes criticism for some reason.

 

[NUCENG]

OK the link to the japanese page which links to all the pdf's is this one, I haven't noticed whether its available in english yet:

http://www.tepco.co.jp/nu/fukushima-np/index10-j.html

Some of it is presented in an infuriating way, and some of the files are rather large.

Section 3 has documents which relate to control rods and some other stuff mixed in.

For example this is the file for reactor 1:

http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_3_Keihou1.pdf

It starts with a lot of printed logs that get very busy when the earthquake hits. Later in the document there are some tables of data that are presented in an annoying way. Finally after many pages the control rod-related data starts, and is presented in several different ways. The report formats varies considerably between reactors, some have more japanese than others, and some reactors have more snazzy visualisations of the control rod positions and what looks like other important reactor core data. Lots of the data is repetitive as it covers the normal operating hours before earthquake.

In any case, I presume that nothing bad happened to control rods, but as there are a few glitches in the data at certain moments in time, Id love someone knowledgeable to review this. For example with reactor 1 data there is a bunch of numbers but at one brief point the word BAD features. Also what looks like a 15:00 visualisation of the rods all showing the -99 value. The -99 one is on nearly the last page of the document, and is somewhat obscured by being printed in the same place on the same page as another type of data. I expect its nothing/normal but I just want to be more certain.

Thank you. I will give it a shot. My Japanese is abot 40 years old. I am even afraid to try it in a sushi house because I am afraid of insulting the sushi chef. Wouldn't want to get some bad fugu.

 

[SteveElbows]

Thank you. I will give it a shot. My Japanese is abot 40 years old. I am even afraid to try it in a sushi house because I am afraid of insulting the sushi chef. Wouldn't want to get some bad fugu.

Well I was quite surprised how much of these documents meant at least a bit to someone like me who has no japanese or special technical reactor knowledge, so I think you'll be ok :)

As mentioned before the main problem with all this data is that it ends too early to see the vivid details of things going wrong. I can only imagine what a nightmare it was for those trying to deal with all the reactors to be in the dark, data-wise, for much of this period as well.

 

[Bodge]

...

Certainly the Reagan and her crew had the equipment and knowledgeable personel to determine exactly what the substances in that cloud were. I've not seen any data.

You read my mind.

What isotopes were in that cloud?

Additionally, where is the film footage of the minutes and hours after the explosion at three?

We have all seen the infamous video of the mushrooming debris cloud ascending to 1km+, what happened next?

There is so much data withheld that the question has to be WHY aren't many simple questions already answered?

If news is positive I'd expect it to be released.

 

[Bodge]

...

You know what I don't understand? TEPCO is pumping water in, using existing piping. If they can do that, they can also push a flexible borescope in, without altering their setup or opening additional valves or anything. Why aren't they?

They might not like what they find or they might not want us to know.

Or management really is FUBARED and radiation induced cognitive impairment is taking its toll.

 

[Cire]

...If the fuel melted and the RPV breached early on, as they have admitted in #1, then yes the temps and pressures they've been issuing for weeks do seem pretty suspect, don't they?

I don't believe TEPCO has stated the RPV has failed in unit 1. They had a core melt event, that's not the same as the RPV being breached. Three mile island showed us how robust the RPV can be in a fuel melt event.

If the bottom of the RPV melted out you wouldn't be getting temperature readings from sensors at the bottom of the RPV.

 

[tsutsuji]

I did see those from back in march, I believe from satellite and I should have clarified a bit.

In case you want to see the whole series of helicopter borne thermal images released by the ministry of defense, they are available at http://www.mod.go.jp/j/approach/defense/saigai/tohokuoki/temp.html

 

[Bodge]

I don't believe TEPCO has stated the RPV has failed in unit 1. They had a core melt event, that's not the same as the RPV being breached. Three mile island showed us how robust the RPV can be in a fuel melt event.

If the bottom of the RPV melted out you wouldn't be getting temperature readings from sensors at the bottom of the RPV.

So if the majority of the core remains in the RPV, are we still at risk of catastrophic explosions at 1-3 ?

 

[razzz]

I don't see a drawing in there labeled "8-1" but it sounds like you're talking about page 18. The drawing that shows vents directly from the drywell to the refueling floor originated with the Areva presentation that came out weeks ago. See page 20

http://www.fairewinds.com/sites/default/files/AREVA%20Fukushima.pdf

The AREVA presentation has gotten a lot of attention here and elsewhere (mostly elsewhere) but that drawing continually escapes criticism for some reason.

I double checked, it is still page 20 of 30 as my Foxit .pdf Reader produces it. Labeled 'Figure 8-1 Reactor Well Seals'
I take it, above the drywell cap, air is able to move freely from the vents shown.

The plant lacked a way to deliver coolant and the SFPs blew up and the reactor meltdowns are just collateral damage makes no sense esp. concerning Unit 4.

http://tec-sim.de/images/stories/fusfpfail.pdf"

 

[Gary7]

Just regarding the USS Ronald Reagan, I looked for information regarding the ballistic radiation readings and subsequent food contamination and three-day emergency, but I could not find any. There was an early report of radioactivity in the drinking water, which was later shown to be a false positive. There is an excellent AP article that describes events on the Ronald Reagan here.

http://www.1310news.com/news/world/article/202681--uss-ronald-reagan-fought-contamination-amid-effort-to-aid-disaster-stricken-japan?ref=topic&name=index.php&title=

More details here

http://waronterrornews.typepad.com/home/2011/03/japan-uss-ronald-reagan-update.html

Furthermore, all of this transpired on the 13th of March (Sunday). If I recall correctly, the explosion at Unit #3 occurred on Monday the 14th. So the radiation that the USS Ronald Reagan encountered had to have come from Unit #1.

 

[SteveElbows]

It sounds like we may learn how much of the steam at reactor 2 is from fuel pool as opposed to suppression chamber in a few weeks:

http://www3.nhk.or.jp/daily/english/19_04.html

TEPCO says it is laying power cables for a cooling system for Number 2 reactor's spent fuel pool. A heat exchanger will be brought into the facility early next week to start operating the cooling system by the end of this month.

Workers entered the Number 2 reactor building on Wednesday for the first time since a hydrogen explosion on March 15th. They tried to check radiation levels but left the building after 14 minutes because it was filled with steam, making further work impossible.

The utility says the vapor appears to be coming from the damaged suppression chamber as well as from the fuel pool itself.

Senior TEPCO official Junichi Matsumoto says he believes cooling the spent fuel pool will help reduce steam inside the reactor.

 

[pdObq]

Section 3 has documents which relate to control rods and some other stuff mixed in.
For example this is the file for reactor 1:
http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_3_Keihou1.pdf

[...]

Also what looks like a 15:00 visualisation of the rods all showing the -99 value. The -99 one is on nearly the last page of the document, and is somewhat obscured by being printed in the same place on the same page as another type of data. I expect its nothing/normal but I just want to be more certain.

On some pages it says "-99 = Missing control rod position". Don't know how to interpret that.

 

[TCups]

I double checked, it is still page 20 of 30 as my Foxit .pdf Reader produces it. Labeled 'Figure 8-1 Reactor Well Seals'
I take it, above the drywell cap, air is able to move freely from the vents shown.

The plant lacked a way to deliver coolant and the SFPs blew up and the reactor meltdowns are just collateral damage makes no sense esp. concerning Unit 4.

http://tec-sim.de/images/stories/fusfpfail.pdf"

The "Presentation" content regarding siphoning from the spent fuel pools seems like new and potentially important information. I don't think this topic or possibility has been previously considered or discussed in this thread, has it?

http://tec-sim.de/images/stories/fusfpfail.pdf

 

[pdObq]

I seem to remember having read in one of the documents posted in this thread that one of the cooling systems operates, in automatic mode, between a couple setpoints (water levels in the RPV, iirc).

Yes, just for those too lazy to take a look into those documents , here are a few graphs attached from http://www.ornl.gov/info/reports/1981/3445600211884.pdf (p. 38ff (p. 50ff), see also post #7747), that show what happens when everything works as it should (it's a computer simulation, just in case someone is wondering).

One can see nicely how the RCIC cycles on and off keeping the water level between the upper and lower level, and also how safety relief valves open above a certain pressure and close again, thus cycling the RPV pressure.

[Since apparently one can upload only up to 3 attachments, it's a big collage. It was resized when uploading to forum max size. Oh well... I guess it's still readable.]

 

[pdObq]

And two weeks later they found them dead of internal bleeding in the turbine basement. I thought this an interesting cause of death, because they could have said they died of blast damage from the explosion, and no one would have given it a second thought, however internal bleeding likely came from some other cause.

Why? Isn't internal bleeding exactly what one would expect from a strong shockwave running through a poor fellow?

See, e.g. http://en.wikipedia.org/wiki/Blast_injury (bolding by me):

In general, primary blast injuries are characterized by the absence of external injuries; thus internal injuries are frequently unrecognized and their severity underestimated. [...] Blast lung refers to severe pulmonary contusion, bleeding or swelling with damage to alveoli and blood vessels, or a combination of these. It is the most common cause of death among people who initially survive an explosion.​

See also here, http://www.bt.cdc.gov/masscasualties/blastessentials.asp , under primary blast injuries:

Injury from over-pressurization force (blast wave) impacting the body surface: TM rupture, pulmonary damage and air embolization, hollow viscus injury.​

I am not really familiar with all that "medical slang" but that sounds a lot like "internal bleeding" would summarize it reasonably well for medical laymen like me.

 

[Cire]

So if the majority of the core remains in the RPV, are we still at risk of catastrophic explosions at 1-3 ?

I don't believe so. The core geometry is mangled and the fuel is sitting in borated water which has poisoned the fuel and reactor.

I suspect the largest problem now is that of washing out the core. If they can capture the outflow and process out the contaminants, cool it and pump it back in then the situation will be much more stable..

With the 16+ pressure relief values on the RPV I don't believe its possible to over-pressurize it.

With water in the bottom of it or the dry well flooded I don't see how you can melt through it either.

 

[pdObq]

You know what I don't understand? TEPCO is pumping water in, using existing piping. If they can do that, they can also push a flexible borescope in, without altering their setup or opening additional valves or anything. Why aren't they?

They might not like what they find or they might not want us to know.
Or management really is FUBARED and radiation induced cognitive impairment is taking its toll.

Come on guys, what do you expect from people who want to spray water into the SFPs with riot police trucks, who don't accept robots flown in from Europe specifically designed for nuclear accidents, and instead use two bomb disposal robots with a radiation meter taped to one of them.

 

[pdObq]

A few questions regarding the temperature sensors to figure out how trustable the temperature readings still are.

1. Does anyone know what kind of temperature sensors they are using? (Thermocouple, resistive, semiconductor, ...)
2. How is the sensor signal read out from the sensor to the control room? Are there amplifiers, AD converters, signal conditioning electronics and stuff like that located in the drywell close to the sensors?
3. How are the sensors mounted at their various locations? (Thermally conductive glue?)
   Is it conceivable that they can detach due to heat and humidity?

Concerning unit 1, if the sensors were just floating in the air, would it make sense that steam from the steamy atmosphere in there condenses on them and keeps them at roughly 100 degC ?

 

[mikefj40]

Just picked this up on the Twitter... Purportedly new images of tsunami flooding from TEPCO http://www.tepco.co.jp/tepconews/pressroom/110311/index-j.html

TEPCO slideshow: http://cid-0b14c7ab35e39ebd.photos.live.com/play.aspx/%5ENFNPP1%20Tsunami%20Flooding

Forgive me if these have already been posted. They're new to me.

 

[mikefj40]

They're new to me.

Most of them, not all...

 

[TCups]

Just picked this up on the Twitter... Purportedly new images of tsunami flooding from TEPCO http://www.tepco.co.jp/tepconews/pressroom/110311/index-j.html

TEPCO slideshow: http://cid-0b14c7ab35e39ebd.photos.live.com/play.aspx/%5ENFNPP1%20Tsunami%20Flooding

Forgive me if these have already been posted. They're new to me.

The interesting thing, to me, is the perspective. It is easy to underestimate the size of the wave and the amount of water inundating the NPP. Look at the pipes going to the vent towers. They are big enough to drive a SUV through! I didn't appreciate the size and weight of the pipe sections before.

 

[mikefj40]

I didn't appreciate the size and weight of the pipe sections before.

I'd conclude that the earthquake and tsunami didn't break the connection to the stacks. Venting was observed on the 12th and 13th. Post #7684.

The highly kinetic environment caused by the explosions broke the stack ventilation.

I have to add AFAIK and FWIW...

 

[NUCENG]

OK the link to the japanese page which links to all the pdf's is this one, I haven't noticed whether its available in english yet:

http://www.tepco.co.jp/nu/fukushima-np/index10-j.html

Some of it is presented in an infuriating way, and some of the files are rather large.

Section 3 has documents which relate to control rods and some other stuff mixed in.

For example this is the file for reactor 1:

http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_3_Keihou1.pdf

It starts with a lot of printed logs that get very busy when the earthquake hits. Later in the document there are some tables of data that are presented in an annoying way. Finally after many pages the control rod-related data starts, and is presented in several different ways. The report formats varies considerably between reactors, some have more japanese than others, and some reactors have more snazzy visualisations of the control rod positions and what looks like other important reactor core data. Lots of the data is repetitive as it covers the normal operating hours before earthquake.

In any case, I presume that nothing bad happened to control rods, but as there are a few glitches in the data at certain moments in time, Id love someone knowledgeable to review this. For example with reactor 1 data there is a bunch of numbers but at one brief point the word BAD features. Also what looks like a 15:00 visualisation of the rods all showing the -99 value. The -99 one is on nearly the last page of the document, and is somewhat obscured by being printed in the same place on the same page as another type of data. I expect its nothing/normal but I just want to be more certain.

Results of a quick scan:

No significant problems associated with rods. all SCRAMs were completed and guaranteed shutdown as far as I can see. from alarms logs, and graphs.

Unit 1 had high pressure injection for about 12 minutes as reactor pressure dropped due to combined cooling from injection and isolation condenser. SRVs sis not cycle during the period covered by graphs.Bothe EDGs started and successfully loaded. No data at time of tsunami.

Unit 2 - see previous post

Unit 3 Multiple SRVs cycled unlike Unit 2. Neither HPCI nor RCIC appears to have auto-initiated or they were secured by operators. No coolant injection until 1602 hrs when RCIC was started. Both EDGs started and were loaded successfully and tripped at about 1538 (tsunami) Data has gaps: No data for SRV B and D and no flow information for RHR and RHRSW.

Very important: If level 0-reference is Top of Active Fuel Unit 3 core uncovery began at about 1600 on 3/11. Because multiple SRVs were cycling and HPCI apparently did not start, the coolant discharged through SRVs was more than RCIC could make up so level continued to drop after RCIC started. It would be assumed they were able to recover level after the time of these graphs or it would have been unit 3 needing to be vented first.

Unit 5 Data is incomplete: no data from time of scram or time of tsunami. Data does show both EDGs started.

There is a great deal of mor information available on that site that could use an interpreter. My next goal is to check the computer lists of alarms to match it up to information in graphs.

 

[MiceAndMen]

I'd conclude that the earthquake and tsunami didn't break the connection to the stacks. Venting was observed on the 12th and 13th. Post #7684.

The highly kinetic environment caused by the explosions broke the stack ventilation.

I have to add AFAIK and FWIW...

And this picture shows the staircase on the south side of Unit 4 survived the tsunami as well.

http://www.tepco.co.jp/en/news/110311/images/110519_1_10.jpg

I know that has been discussed before, but I don't remember where exactly.

The ground level of the tanks in this photo is about 10 meters O.P.

http://www.tepco.co.jp/en/news/110311/images/110519_1_1.jpg

... making this photo very scary looking indeed...

http://www.tepco.co.jp/en/news/110311/images/110519_1_5.jpg

 

[westfield]

In their scenario, no-one is pumping water into the drywell. I don't know... the core may be out of the drywell, or not.

You know what I don't understand? TEPCO is pumping water in, using existing piping. If they can do that, they can also push a flexible borescope in, without altering their setup or opening additional valves or anything. Why aren't they?

Deploying a borescope would most certainly require them to rejig the pipe configuration and would definitely require an entry point to be opened for the borecam umbilical.


Regardless, I don't believe it would be possible given how many physical constraints there would be in the pipe system - pumps(even stationary) and filters are two things that immediately preclude using a borescope - seems highly unlikely any water injection lines into an RPV would not have at least one filter.

If it was even possible to do that what would they see? The inside of a sparge ring or the annulus between the RPV and shroud? Not that useful.

If they thought it was possible would they would risk getting an instrument stuck in their only water injection line?


Clearly what they need is a wireless, rad hard, temperature tolerant , waterproof, steam proof, camera "pill" that can somehow get through pumps and filters undamaged and that can transmit data wirelessly through tons of water, concrete and steel. Perhaps they havn't had the chance to pop down to Akihabara yet ;)

 

[zapperzero]

Deploying a borescope would most certainly require them to rejig the pipe configuration and would definitely require an entry point to be opened for the borecam umbilical.

If it was even possible to do that what would they see? The inside of a sparge ring or the annulus between the RPV and shroud? Not that useful.

Rejig how? Definite yes on the entry point, but since the connection they are using is outside the reactor building, I don't see that as a problem. Any pumps there may be are stopped, the whole jig is letting 9 cubic metres per hour through and I'm not sure I understand why there must be filters on that line. That may be just me being stupid, of course.

They might see a broken ring seal, meaning they have been pumping water into the drywell instead of the RPV all along. They might see a glow from the corium and that would be informative. They might not, and that would rule out some scenarios too. They might see there's nothing recognizable left of the shroud. If they manage to retrieve the scope, they might get some interesting trace chemicals to analyze.

 

[zapperzero]

p 15. Narrow range and wide range reactor pressure. After scram and void collapse pressure dropped, After Main steam isolation valve closure pressure rose to SRV cycling setpoint.
p 16 SRV F was cycling. gradual change in cycling rate shows decay heat decreasing.
p 21. RWL slow change up to 1800 mm and dow to 300 mm under operation of RCIC and SRVs
p 34. SRV F continues to cycle.
p. 35. Nothing significant.

Iirc, just one SRV cycling means it was operating automatically, because normal procedure is for the operator to open alternate SRVs, and so avoid local heating of the pool. Correct? Any guess on cause/consequences?

EDIT: this is reactor 2 data and the working assumption of TEPCO is the torus is broken in #2. This NRC document
http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0933/sec3/108.html
says

Continued steam blowdown into the pool will increase the local pool temperature. The condensation rates at the turbulent steam/water interface are eventually reduced to levels below those needed to readily condense the discharged steam. At this threshold level, the condensation process may become unstable; for example, steam bubbles may be formed and shed from the pipe exit, oscillate, collapse, and give rise to severe pressure oscillations which are then imposed on the pool boundaries.

EVEN LATER EDIT, IMPORTANT: don't let Dymytry near that doc. He'll get the conniption fits if he sees it.

 

[NUCENG]

Deploying a borescope would most certainly require them to rejig the pipe configuration and would definitely require an entry point to be opened for the borecam umbilical.


Regardless, I don't believe it would be possible given how many physical constraints there would be in the pipe system - pumps(even stationary) and filters are two things that immediately preclude using a borescope - seems highly unlikely any water injection lines into an RPV would not have at least one filter.

If it was even possible to do that what would they see? The inside of a sparge ring or the annulus between the RPV and shroud? Not that useful.

If they thought it was possible would they would risk getting an instrument stuck in their only water injection line?


Clearly what they need is a wireless, rad hard, temperature tolerant , waterproof, steam proof, camera "pill" that can somehow get through pumps and filters undamaged and that can transmit data wirelessly through tons of water, concrete and steel. Perhaps they havn't had the chance to pop down to Akihabara yet ;)

If they are adding water through the core spray lines the borescope would need to be able to go through a spray nozzle. If they go in through the RHR system they need to go through the Recirc system jet pumps. If they go in with RCIC or HPCI they would need to go through the feedwater header holes. They would have a long way to go after they get into be able to get to the area below the core support plate. The most direct path would be through the jet pumps to the area of the lower plenum. All of these systems are in the lower level of the reactor building close to the torus in an extremely high radiation area.

A borescope expedition may be possible in spite of the difficulties. But here is the real question. Depending on what they see, what could they do differently than what they are already doing?

 

[Cire]

A few questions regarding the temperature sensors to figure out how trustable the temperature readings still are.

1. Does anyone know what kind of temperature sensors they are using? (Thermocouple, resistive, semiconductor, ...)
2. How is the sensor signal read out from the sensor to the control room? Are there amplifiers, AD converters, signal conditioning electronics and stuff like that located in the drywell close to the sensors?
3. How are the sensors mounted at their various locations? (Thermally conductive glue?)
   Is it conceivable that they can detach due to heat and humidity?

Concerning unit 1, if the sensors were just floating in the air, would it make sense that steam from the steamy atmosphere in there condenses on them and keeps them at roughly 100 degC ?

1. Thermocouple.

2. Likely. The amplifiers are probably subject to high levels of radiation atm.

3. The sensors are mechanically connected to the pipes/vessel etc.

4. Possible.

Don't forget the sensors also where damaged when they subject to temperatures greatly exceeding their maximum rating. I don't believe the values they report now can be trusted with any certainty.

 

[Cire]

If they are adding water through the core spray lines the borescope would need to be able to go through a spray nozzle. If they go in through the RHR system they need to go through the Recirc system jet pumps. If they go in with RCIC or HPCI they would need to go through the feedwater header holes. They would have a long way to go after they get into be able to get to the area below the core support plate. The most direct path would be through the jet pumps to the area of the lower plenum. All of these systems are in the lower level of the reactor building close to the torus in an extremely high radiation area.

A borescope expedition may be possible in spite of the difficulties. But here is the real question. Depending on what they see, what could they do differently than what they are already doing?

You're not getting an image sensor anywhere near those high levels of radiation unless all you want to see is white noise.

That implies you have to snake the worlds longest fiber optic bundle through, valves, piping, debris into an environment that would bake said fiber bundle.

Nobody is going to look inside the RPV until radiation levels drop to the point that people can access the dry well.

 

[westfield]

Rejig how? Definite yes on the entry point, but since the connection they are using is outside the reactor building, I don't see that as a problem. Any pumps there may be are stopped, the whole jig is letting 9 cubic metres per hour through and I'm not sure I understand why there must be filters on that line. That may be just me being stupid, of course.

snip>.

This is boring - Can we just leave this at the most obvious reason and the reason you didn't try and argue : they don't want to risk compromising the only cooling they have just to take an image of dubious usefulness inside the RPV? Thats more than a good enough reason to kill this discussion without getting too technical.

We could get into the piping complications of which there are potentially many but why bother, they are not going to try and send a borescope through that line. They will find a far more suitable entry point if\when they do try and image the inside of the RPV.

If you cannot see why there would very likely be filters on a water line leading into an RPV and you cannot understand why a borescope cannot get past most pump impellers, stationary or otherwise, then it's prob best to drop the idea.

 

[Rive]

You're not getting an image sensor anywhere near those high levels of radiation unless all you want to see is white noise.

'Radiation hardened cameras' (google it) are available for nuclear industry. But Westfield is right, no use for such cameras now, they have to bring the reactors in cold shutdown first, and then secure everything before visually checking the internals of the containment/RPV. Such pictures will be needed only for the decommissioning, which will not happen in the next few years.

Unit 5 Data is incomplete: no data from time of scram or time of tsunami. Data does show both EDGs started.

It was on outage, so no SCRAM was needed?? :-)

 

[MoonofA]

'Radiation hardened cameras' (google it) are available for nuclear industry. But Westfield is right, no use for such cameras now, they have to bring the reactors in cold shutdown first, and then secure everything before visually checking the internals of the containment/RPV. Such pictures will be needed only for the decommissioning, which will not happen in the next few years.

If there is an accessible 150mm line going into the drywell or reactor vessel this little machine would be the right thing to use.
http://www.khgmbh.de/wEnglisch/fernhantierung_kleinesinspektionsfahrzeug.php?navanchor=1010051

It was specially build for such purposes. These robots were offered by Germany to the Japanese at the start of this mess, but the offer was not taken.

I have copied parts from an image movie which shows the various nuclear accident robots Germany has for just such purpose. You can watch it here:
http://www.youtube.com/user/MoonofA#p/u/0/dbdwUnUvmFw

Edit: The French have similar equipment available on 24/7 standby

 

[zapperzero]

This is boring - Can we just leave this at the most obvious reason and the reason you didn't try and argue : they don't want to risk compromising the only cooling they have just to take an image of dubious usefulness inside the RPV? Thats more than a good enough reason to kill this discussion without getting too technical.

We could get into the piping complications of which there are potentially many but why bother, they are not going to try and send a borescope through that line. They will find a far more suitable entry point if\when they do try and image the inside of the RPV.

If you cannot see why there would very likely be filters on a water line leading into an RPV and you cannot understand why a borescope cannot get past most pump impellers, stationary or otherwise, then it's prob best to drop the idea.

Yeah. Okay. I'm too stupid to understand an impeller pump, a bundle of fiber optic is just the kind of object you would use to plug a pipe shut, you have an opinion on whether there likely are filters and pumps on that line and it's way more valuable than mine because...

I can also see the usefulness argument. Who cares if there's still core in the RPV?

But yea, let's stop this here, the SNR is bad even without feelings getting in the way.

 

[razzz]

Via http://ex-skf.blogspot.com/"

From Yomiuri Shinbun (9:14PM JST 5/18/2011):

中部電力は１８日、運転停止作業中に冷却水に海水が混入するトラブルが起きた浜岡原子力発電所（静岡県御前崎市）５号機に隣接した補助建屋の排気ダクトの出口で、ごく微量の放射性核種「ヒ素７６」を検出したことを明らかにした。

Chubu Electric announced on May 18 that a minute amount of arsenic-76, radionuclide, was detected at the exhaust duct of the ancillary building to the Reactor 5 reactor building at Hamaoka Nuclear Power Plant, where the sea water got mixed up in the reactor coolant while the reactor was being shut down.

　周辺環境への影響はないという。

The company says there is no ill effect on the environment.

　同社は、トラブルの影響で、海水中に存在する「ヒ素７５」が原子炉内で放射化したものとみている。

The company thinks arsenic-75 present in the seawater turned radioactive inside the reactor.