Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[NUCENG]

Do we know more on this for the various reactors/plants? Which pumps did fail?

All of them failed due to loss of Power. Whether or not they were physically damaged is irrelavent at Fukushima, but should be considered during investigation and development of lessons learned.

 

[NUCENG]

The following article http://astand.asahi.com/magazine/judiciary/articles/2011051100015.html?iref=chumoku expresses the view that most diesel generators at Fukushima Daiichi are water-cooled : "The tsunami hit the seawater pumps and water intake became impossible. As a consequence, the 10 water-cooled emergency diesel generators stopped (...) Unit 2, unit 4 and unit 6 have one air-cooled emergency diesel generator each. (...) Those at unit 2 and unit 4 failed too. They are located high above sea level, which raises the possibility that what failed was the metal-clad switchgear which acts as the electric power receiving end at the building"

A photograph showing seawater pumps being removed for inspection at Ikata NPP can be viewed at : http://mytown.asahi.com/areanews/ehime/OSK201105190135.html

Switchgear or fuel tanks could have been damaged with the same result as flooding the generator rooms themselves. If it turns out impossible to protect the whole site, protect the essential parts of the site from inundation.

 

[NUCENG]

Broken pipes discovered at Hamaoka's No. 5 nuclear reactor
http://www.asahi.com/english/TKY201105210146.html

[URL]http://www.asahicom.jp/english/images/TKY201105210310.jpg

[/URL]

I have seen pictures of similar damage to condenser tubes from a broken baffle plate in a US BWR. The circulating water pumps are sending millions of kg of seawater water through the condenser. It5 doesn't take long to put tons of water into the condensate and the feedwater system dutifully pumps that water into the reactor.

 

[Most Curious]

Do the seawater pumps have a safety for loss of NPSH?

Surely they sucked air when the sea retreated in the moments before the tusnami!

Secondly, do the seawater pumps supply the various condensers directly or is there an intervening surge tank or pond?

 

[Most Curious]

I have seen pictures of similar damage to condenser tubes from a broken baffle plate in a US BWR. The circulating water pumps are sending millions of kg of seawater water through the condenser. It5 doesn't take long to put tons of water into the condensate and the feedwater system dutifully pumps that water into the reactor.

Are nukes like coal plants in that the main condenser actually draws a vacuum on the turbine outlet ? If so, a tube rupture would allow a LOT of seawater to flow into the condensate return system!

 

[robinson]

Considering the amount of water being pumped to cool an operating reactor, (even one shutting down), any interruption of cooling water from the ocean source might be catastrophic. I thought they had a secondary system to cover that eventuality?

 

[NUCENG]

Yes. It is daughter of Ba-140, which in turn can be found in the decay chains of both U-238 and U-235, iirc. But I can't find a chart so... let's wait for the experts.

Use:

http://atom.kaeri.re.kr/index.html

Click on the chart and enter the isotope you are interested in the box at the top left of the screen (e.g., BA140). If it is a daughter fission product there will be a field for "Parent Nuclide" Click on that and you will go to that nuclide and you may find it too has a parent nuclide. By exploring these links you can build a complete decay chain.

 

[WhoWee]

Considering the amount of water being pumped to cool an operating reactor, (even one shutting down), any interruption of cooling water from the ocean source might be catastrophic. I thought they had a secondary system to cover that eventuality?

About 7,000(?) posts ago I also pondered the possibility of a mechanical backup. It seems reasonable something could operate off the excess heat - like a giant thermostat - to open and let sea/fresh water in - then close when the temperature drops?

 

[NUCENG]

Ok, on google maps i checked but it is very difficult to see it due to the poor resolution. On the picture below, you see on the right the four water intakes (one for each reactor, N°1 is smaller because the reactor is smaller in fact). Then if you move a little bit on the left, then you will see some spherical grey objects, aligned parallel to the intake, these are the pumps: 2 for N°1, 3 for N°2 to 4 but at N°4, because they were doing maintenance on the core, it seems they were also doing maintenance on the pumps because they seem to be removed on this picture. You can see that they are very vulnerable from tsunami standpoint (they must be close to the sea to some extent of course!) and they are also critical in order to keep the cold source working!

http://www.netimago.com/image_202942.html

I add this other satellite view, you see very well the difference between the N°1 and the others (size of intake and N° of pumps)

http://www.netimago.com/image_202943.html

I add a picture showing how they look like -these are from N°5 reactor and got hit by this big blue structure, but they look similar to the others:

http://www.netimago.com/image_202944.html

Do you see them?

Note 1 : I add this other picture showing the all 6 reactors from the sea, so you see very well the size of the various intakes and the grey pumps in the alignment:

http://www.netimago.com/image_202948.html

Note 2: At DAINI plant, which is newer, they added some buildings close to the sea but to me, these pumps are still outside, close to these buildings (the 3 aligned white/grey circles each time)

http://www.netimago.com/image_202950.html

Each of the plants has three circulating water pumps (Unit 1 may only have 2). Those are the largest pumps in your pictures. Each plant probably also has two general service water pumps and two emergency service water pumps. If you look at Unit 4 you see the four small pumps and three circular areas at the inlet that are where the motors for the circulating water pumps should be. Since the plant was in an outage the motors may have been removed for maintenance. Or they may have been destroyed in the tsunami.

 

[NUCENG]

I like your analysis. I think the red is red marker powder.
Let me throw my $0.02 in the rubble debate, from a very different angle.

I had been looking for a way to avoid having to think of burning concrete and burning metals, because I didn't understand why such high temperatures would not also produce other observable effects. Seems I found it.

The yellow stuff is indeed insulating foam. To be more precise, it is polyurethane foam, widely used for insulation and as a fire retardant. If you are looking for an explanation for what generated massive amounts of black smoke on several occasions, this may be it. A small electrical fire in a cable duct (a la Browns Ferry) can be enough to get it going.

Diablo Canyon incidents:
http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1988/in88004s1.html

LATER EDIT: the small orange-brown pieces you ask about are also insulating foam. It gets like this from being exposed to UV light.

What would be the ignition source if power was out? The Information notice involved fires in a fire barrier for the EDG exhaust system at Diablo Canyon. The diesels weren't operating at Fukushima.

 

[Astronuc]

For experts: how can you interpret that water from N°1 is significantly less contaminated (orders of magnitude lower for most isotopes) than N°2 and N°3, and that Ba-140, La-140 (short half life) and Sr 89 and 90 are much lower in this N°1 water (see page 3 of pdf)?

Is La-140 a daughter isotope in the decay process of other elements?

Interestingly, and complementing the contributions of others, . . .

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fisfrag.html#c3

 

[NUCENG]

The easiest explanation is there's some steel thing with a fresh thick coat of radioactive cesium. Could be anything, really, although spent fuel should be much hotter.

Does equipment get that hot? Hmm... the cooling loop is pretty hot with very short-lived stuff, but may also get contaminated with all sorts of activated junk from the reactor.

I'm pretty sure I read somewhere that turbine blades are rad waste by the time they're done with them.

During BWR plant operation there are areas that get to 1 Sv per hour primarily near steam piping due to N-16 gamma radiation. These areas are locked high radiation errors where personnel access is not allowed during operation. Examples include the steam jet air ejector area, the reactor water cleanup area, and the steam tunnel between the reactor building and turbine building.

 

[Astronuc]

I have seen pictures of similar damage to condenser tubes from a broken baffle plate in a US BWR. The circulating water pumps are sending millions of kg of seawater water through the condenser. It5 doesn't take long to put tons of water into the condensate and the feedwater system dutifully pumps that water into the reactor.

I think I mentioned this earlier or perhaps elsewhere, but there was a US plant that had a LP turbine throw some blades through the condenser. Tubes were ruptured, and river water entered the feedwater system. It also happened late winter/early spring, so the water had an elevated salt content from the run off from area roads that are salted in winter.

The issue for the utility was impact of salt on IASCC/IGSCC of the stainless steel component and surfaces, particularly the control rods and control rod drive mechanisms.

 

[NUCENG]

Reactor is source of steam, then steam is going to turbine, this turbin is connected to pump, water source is torus, pump is pumping water from torus to RPV and steam which go to turbine is condensated in torus.
http://a2.sphotos.ak.fbcdn.net/hphotos-ak-ash4/188425_211896475487877_113650851979107_876237_7212984_n.jpg

In normal lineup RCIC initially pumps water from the clean condensate storage tank. Suction can be switched to torus, but that is not the first choice.

 

[Astronuc]

Are nukes like coal plants in that the main condenser actually draws a vacuum on the turbine outlet ? If so, a tube rupture would allow a LOT of seawater to flow into the condensate return system!

It's been years since I've done a calculation on the turbine side, but I remember a vacuum drawn on the condenser since the water temperature is cold (relative to the turbine) and the vapor pressure is very low - less the 1 atm. That water would be passed to the reheaters coming off the LP stages.

 

[NUCENG]

Do the seawater pumps have a safety for loss of NPSH?

Surely they sucked air when the sea retreated in the moments before the tusnami!

Secondly, do the seawater pumps supply the various condensers directly or is there an intervening surge tank or pond?

Yes the pumps may trip on overspeed, over current, ground fault, discharge valve closure or high vibration. Specifics may vary from plant to plant. Fukushima plants are once-through designs. The Circulating Seawater Pumps pump directly to the condensers and back to the sea. Other plants that have cooling towers will have supply pumps and separate circulating water pumps. Cooling towers are used to reduce heat returned to the water source on smaller rivers and lakes. The sea is a very large heat sink so Fukushima can use the once through design.

 

[NUCENG]

I saw two interviews on TV with people who were actually working at the plant, inside the plant at the time of the earthquake. It was pretty much get out any way you could, and run away. During the quake, which lasted quite a while. Eyewitness reports of large cracks in the reactor buildings, massive damage to the facility, one American there stated they pried open the safety doors to get out of the building.

Then later when the tsunami was coming everyone ran for high ground. Nobody stayed at the controls when the tsunami hit. This was on television, CNN I believe.

I saw one of those reports - an electrician who was inside the reactor building. But what I was wondering was if anyone in the control room operating crew had been interviewed yet. They are the only ones who can answer to "pucker" or panic.

 

[NUCENG]

Astronuc, NUCENG, et. al.

What are we to understand from the 215 Sv/Hr readings in No.1's drywell?
[215 is the latest number from TEPCO's daily update]*

Does this indicate ongoing criticality or has a fragment of corium 'just' migrated nearer the sensor?

What should we expect to happen next if there is corium in the drywell, with or without ongoing fission?

Additionally, why is the pressure in the RPV edging ever upwards?

TIA

* see also: http://www.cbsnews.com/stories/2011/05/25/ap/business/main20065975.shtml

"In addition, some chunks of the fuel appeared to have entered the inner containment chambers, or drywell, causing some damage."

Possibilities:

High radiation

• More of the core is being released to the drywell where it is not shieded by RPV so radiation continues to increase.
• Instrument failure
• Unlikely, but possible, Recriticality

Corium in drywell

• May continue to melt through vessel, Drywell liner, concrete, etc.
• May solidify in place as decay heat continues to drop and cooling efforts continue.

Pressure

• Pressure rising because containment is not completely failed
• Instrument failure
• pressure rising due to continuing heating from corium inside or outside the vessel
• pressure rising due to continuing release of hydrogen anbd other non condensibles.
• pressure may drop if containment fails further
• unlikely but possible recriticality

In short, your guess of what comes next is probably as good as mine.

 

[NUCENG]

It looks like an 'old school' BWR cannot take a direct hit from a 6-7 magnitude quake, tsunami or not.

This report is a verbatim quote from other news reports. My first criticism is the description of a 3 cm or 7 cm fault. A linear crack is not a significant leak. Leakage requires a differential pressure AND a break AREA. If this is a newsperson misquote and the answer is 3 cm² or 7 cm² that is way less than the area that would be classified as containment failure. Other posts have indicated that unit one reached pressures more than double the containment vessel limit and TEPCO reports also indicate high temperatures which could have ruptured containment penetrations increasing leakage. The data released on 5/24 from TEPCO indicates similar failure precursers in units 2 and 3. In looking at the graphs, annunciator and alarm logs and reports I have read I have not found any data that indicates a failure before the tsunami. I posted separately about the reported high radiation at the site boundary at 1529 on 3/11/2011. If TEPCO has information about seismic damage to safety systems, they haven't released it to my knowledge. On the other hand, TEPCO spokesman have been beaten up so often (deservedly so) that they may not be willing to say anything is out of the question.

Call me devils advocate. Again, I am not saying there wasn't seismic damage. there were reports of water leakage inside reactor buildings, but apparently it was not radioactive as some workers feared. Unit 3 had a fairly significant delay before starting RCIC or HPCI and there is no clear explanation why. But both systems were used later. There was speculation that the Unit 1 Isolation Condenser failed due to sesmic damage, but now it appears that was operator action that secured the system after only a few minutes. I just haven't seen any conclusive evidence of safety system failures prior to the tsunami.

 

[elektrownik]

wastewater disposal facility is leaking water...:
http://www3.nhk.or.jp/daily/english/26_18.html
reactor 1,2 and 3 drywell damaged:
http://www.yomiuri.co.jp/dy/national/T110525006455.htm

 

[zapperzero]

http://www.tepco.co.jp/en/press/corp-com/release/11052508-e.html

This is in regards to detection of radioactive materials, specifically Pu-238, 239, and 240.

What does this tell us? The report states that TEPCO tested up to 500m from the reactors, but should they be testing further away. I *assume* that these materials could travel as other materials such as cesium and iodine.

Is it significant that they are still finding it? I understand that Pu has a very long half-life, however, the second report (pdf) says that the values have NOT changed greatly.

Thank you for your time and thoughts.

It means some of the fuel has been vaporized or otherwise turned into dust and then got out. If it was there earlier, it's normal for it to be there now. It would be abnormal if the concentration had increased.

Plutonium travels as dust, not dissolved in water like Cesium and Iodine. You'd expect it to fall out sooner, if it wasn't blown up very high.

 

[zapperzero]

Use:

http://atom.kaeri.re.kr/index.html

Click on the chart and enter the isotope you are interested in the box at the top left of the screen (e.g., BA140). If it is a daughter fission product there will be a field for "Parent Nuclide" Click on that and you will go to that nuclide and you may find it too has a parent nuclide. By exploring these links you can build a complete decay chain.

Excellent resource, thanks.

 

[Rive]

It means some of the fuel has been vaporized or otherwise turned into dust and then got out. If it was there earlier, it's normal for it to be there now. It would be abnormal if the concentration had increased.

Plutonium travels as dust, not dissolved in water like Cesium and Iodine. You'd expect it to fall out sooner, if it wasn't blown up very high.

This also imply the possibility of direct release from an RPV (or less likely from an SFP): otherwise it would be trapped in the torus.

 

[Rive]

Possibilities:
...
unlikely but possible recriticality
...

When the possibility of recriticality come in sight I made some digging through the relevant 'googles' and every source suggested that recriticality is expected in a severely damaged core during 'reflood'. Already molten core or corium was never mentioned IIRC. Is recriticality possible in corium too? It has no internal cavities for water

 

[jim hardy]

be patient guys my first try at photo well maybe second

Has this been posted?

found it at Cryptome..was taken March 16, and the deck looks a lot worse in later photos.
it's in the zipped file of full size photos and has this name: aerial-2011-3-18-14-50-0.jpg
(editing mine, with MS-Paint, which clobbers the resolution)

you can see the concrete cap not there but i can't tell for sure about the yellow thing on right. In the hi-res it's a maybe.

Would one who knew how to lighten be able to see down into that black hole and tell if yellow containment cap is there?

 

[biffvernon]

It was pretty much get out any way you could, and run away.

That's the rational human response to what appears at the time to be a life-threatening event.
Nuclear power stations ought to be designed to be safe whenever all the staff unexpectedly rush for the exit and the electricity supply fails. How many of the world's power plants fit that?

 

[tsutsuji]

US BWRs I am familiar with have pump houses to protect the cooling water pumps for General Service Water, Emergency Service Water and Circulating Water systems. These buildings are safety-related, sesmically qualified and water tight where to protect the pump motors. Impeller shafts drive the impellers through a water sealed fitting on the motor floor. Power cables can be elevatedor routed in water tight conduits. So it is possible to protect pumps from flooding damage even if they are located near the water edge.

An electric motor does not need to have contact with the atmosphere, so it is possible to create very watertight designs. For example a conventional submarine basically consists of a very watertight electric motor. Mechanical shocks caused by boats or cars or oil tanks brought by the tsunami wave could also be averted with some sort of concrete bunker.

Do the seawater pumps have a safety for loss of NPSH?

Surely they sucked air when the sea retreated in the moments before the tusnami!

You may want to have a look at my reply to a similar question at https://www.physicsforums.com/showthread.php?p=3306874#post3306874

 

[NUCENG]

That's the rational human response to what appears at the time to be a life-threatening event.
Nuclear power stations ought to be designed to be safe whenever all the staff unexpectedly rush for the exit and the electricity supply fails. How many of the world's power plants fit that?

One of the lessons learned from TMI2 was the need to control the access amd distractions in the control room. Employees and others crowded into the control room to help. They didn't run away. It was necessary to order people to leave the site. Technical Support Centers and Emergency Operating Facilities have been put in place outside the control room on site and off site respectively. These facilities have dedicated communications and monitoring systems. The EOF has specific provisions for the media, Links to regulators, police, emergency response providers and local and state government are provided. These groups feed recommendations and support to the control room with less noise, congestion, and distraction.

 

[seeyouaunty]

This report is a verbatim quote from other news reports. My first criticism is the description of a 3 cm or 7 cm fault. A linear crack is not a significant leak. Leakage requires a differential pressure AND a break AREA. If this is a newsperson misquote and the answer is 3 cm² or 7 cm² that is way less than the area that would be classified as containment failure.

Tepco said if it hypothesizes that a breach of about 3 cm wide occurred at the reactor 1 containment vessel 18 hours after the quake and widened to about 7 cm 50 hours later

http://search.japantimes.co.jp/cgi-bin/nn20110526a1.html

Seems to me that if there is a crack that is 7cm wide (not long, but wide) that would make the opening at least ~40cm². Its worth noting that this is a hypothesis by Tepco to explain the various instrument readings from the reactor, so they probably have a particular flow-rate in mind for the theoretical leak.

"If we do our analysis on the premise that there was a leak in the piping, it matches (data) in reality," a Tepco official said at a news conference.

 

[elektrownik]

What is with unit 2 sfp ? They can't fill it with water, size is the same like in unit 4, but in unit 4 after injection water level is ~6400mm, in unit 2 (after injestion) only ~3500mm, also the temperature jumps are strange, maybe sensor damage ? Temperature is bigger after water injection...
for example
5/22 11:00 2000mm 46C
5/23 05:00 4000mm 70C
5/26 05:00 3000mm 45C

 

[zapperzero]

That's the rational human response to what appears at the time to be a life-threatening event.
Nuclear power stations ought to be designed to be safe whenever all the staff unexpectedly rush for the exit and the electricity supply fails. How many of the world's power plants fit that?

Many. Most, in fact. Nuclear plants are the exception, really. Anyway, even these reactors can scram all by themselves and keep cool automatically for as long as power and water is available. The operators are there to finesse things like fuel consumption and respond to emergencies... just like in an airliner.

One stupid difference from an airliner is they can't generate electricity for themselves. It would be trivial to retrofit. You could patch a derivation and a small steam turbine in anyone of the existing circuits. You could put three of them in just to be sure, make one run off steam coming out from that emergency pressure valve that vents to the outside air. It could do double duty as a nice, apocaliptically loud evacuation siren if you dimension it properly.

 

[Rive]

About 7,000(?) posts ago I also pondered the possibility of a mechanical backup. It seems reasonable something could operate off the excess heat - like a giant thermostat - to open and let sea/fresh water in - then close when the temperature drops?

All this is about the design basis. Of course it's possible to design more systems, pools, heat exchangers, cooling towers but first you have to set up your design basis. Then if something bad happens you can check if it was an error in build, in design or in design basis.

 

[tsutsuji]

Each of the plants has three circulating water pumps (Unit 1 may only have 2). Those are the largest pumps in your pictures. Each plant probably also has two general service water pumps and two emergency service water pumps. If you look at Unit 4 you see the four small pumps and three circular areas at the inlet that are where the motors for the circulating water pumps should be. Since the plant was in an outage the motors may have been removed for maintenance. Or they may have been destroyed in the tsunami.

Yesterday I found a Tepco report confirming that unit 4's 3 main seawater pumps were removed for maintenance : https://www.physicsforums.com/showthread.php?p=3321704#post3321704

What is the purpose of "service water pumps" ?

I add a picture showing how they look like -these are from N°5 reactor and got hit by this big blue structure, but they look similar to the others:

http://www.netimago.com/image_202944.html

The trajectory of the big blue structure, a gantry crane, is shown on page 40 of http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110525_01-j.pdf. I guess this is the crane that is used, among other purposes, when the pumps are removed for maintenance.

English version is now available at http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110525_01-e.pdf

 

[NUCENG]

Yesterday I found a Tepco report confirming that unit 4's 3 main seawater pumps were removed for maintenance : https://www.physicsforums.com/showthread.php?p=3321704#post3321704

What is the purpose of "service water pumps" ?



The trajectory of the big blue structure, a gantry crane, is shown on page 40 of http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110525_01-j.pdf. I guess this is the crane that is used, among other purposes, when the pumps are removed for maintenance.

General service water pumps feed non-safety coolers/ Emergency service water feeds the safety related coolers such as the diesels.

 

[tsutsuji]

General service water pumps feed non-safety coolers/ Emergency service water feeds the safety related coolers such as the diesels.

Thanks. The two safety-related ones are probably those belonging to the 12 (=6 units x 2) failed "RHR sea water systems" mentioned on page 50 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110525_01-e.pdf