Japan Earthquake: nuclear plants

*Joe Neubarth*

Quote by tsutsuji

Concerning unit 4 they said that they could restore a vital pipe called "FPC-68" for that purpose : http://www.tepco.co.jp/en/nu/fukushi...10709_02-e.pdf. Details explaining why they had to stop unit 3 SFP cooling equipment to allow starting the construction of the cover structure at unit 4 are provided in http://www.tepco.co.jp/en/nu/fukushi...10708_01-e.pdf .

As Joewein says above, the cooling has been restored for the SFP at unit 3. What is making you think it has been restored for unit 1 as well ?

On http://www.tepco.co.jp/en/nu/fukushi..._summary-e.pdf the SFP temperature at unit 1 is still marked today with "instrument failure" which makes me doubt much equipment has been restored there.

Concerning unit 2, the SFP circulating cooling system has been running since 31 May, according to http://www.tepco.co.jp/en/nu/fukushi...10711_05-e.pdf page 3. It is also marked as "May 31 17:21 Started full-fledged operation of the alternative cooling system for the Spent Fuel Pool" on http://www.nisa.meti.go.jp/english/p...110711-1-2.pdf page 5.

Considering the degree of site contamination, my hat if off to the Japanese. They have accomplished a lot.

tsutsuji

http://www.asahi.com/national/jiji/JJT201107120052.html At 8:40 AM on 12 July, a leak was observed on a surveillance camera, and the water treatment facility was manually stopped 10 minutes later. The leak location is in the Areva system, in the close proximity of the leak that occurred and was repaired on 10 July. The desalination facility is still running.　Repairs are shown on http://www.tepco.co.jp/nu/fukushima-...10712_02-j.pdf (top picture is before repair, bottom picture is after repair).

http://www.nikkei.com/news/headline/...E3E2E2E2E2E2E2 The leaked volume was 10 l. The leak location was exactly the same as two days ago. The facility was started again at 4:58 PM after changing the fitting for a stainless steel one. It is thought that the zinc-coated cast iron one installed two days ago was corroded by the ferric sulfate flowing in the hose.

http://www.asahi.com/national/update...107110485.html For the purpose of breakwater reinforcement work repairing the tsunami damages at the south of the water inlet, the silt fence will be opened 36 times for two hours each time in the upcoming 3 months to let the steel sheet pile driving boat to come and go. This rises the fear that some of the 1.2 terabecquerels in the water inlet could flow into the sea. The silt fence opening time being limited, Tepco says the consequence on the periphery is limited. Radiation measurements in the sea will be intensified. Local governments have been notified.

http://news.tbs.co.jp/newseye/tbs_newseye4773907.html the nitrogen hose will be connected on unit 3 on 12 July afternoon. The nitrogen injection will start at unit 3 this week (nitrogen injection is already being performed at units 1 & 2).

http://www.yomiuri.co.jp/science/new...OYT1T00502.htm　Minister Goshi Hosono said the details on a new middle to long term study team whose purpose is to study the decommissioning of Fukushima Daiichi will be announced on 19 July. They will have to find a solution so that the final disposal is located elsewhere than in Fukushima prefecture.

http://www.ustream.tv/recorded/15943265 NISA press conference, 12 July : The original heat exchanger at unit 1 SFP can be reused. Tepco hopes the SFP cooling system can be started at the end of July or within the first decade of August.

Operation of the diesel generators was carried out as follows due to the
preparatory construction of Yonomori line for duplication of line (July 11);
D/G 5A started (03:03), connected to the grid (03:19) and stopped
(09:07).
D/G 5B started (03:37) and connected to the grid (03:44).
D/G 6A started (04:17) and connected to the grid (04:21).
D/G 6B started (04:31) and connected to the grid (04:36).
・The power supply from Yonomori line was suspended due to the preparatory
construction for Yonomori line for duplication of line. (05:01, July 11)
http://www.nisa.meti.go.jp/english/p...110712-1-1.pdf

http://www.meti.go.jp/press/2011/07/...10712005-1.pdf page 23 : white smoke observed at unit 4 on 12 July 6:30 AM.

http://www.tepco.co.jp/nu/fukushima-...10712_01-j.pdf page 2 : water injection into unit 4 reactor well and dryer storage pool started at 11:22 AM on 12 July. It had to stop at 12:03 because of a leak in the connection of the injection line.

Cire

Quote by NUCENG

You may be assuming a complete failure of the vessel bottom which may not have happened. The instrument and CRDM penetrations of the vessel are more likely to have failed first allowing corium to exit the vessel. The thermocouples in US plants are qualified to at least 2300 degrees F per USNRC Regulatory Guide 1.97.

According to GE they are actually a Type T Thermocouples with a 350C upper limit. They are magnetically attached which is another big problem. Does anyone know of a magnet that still works when heated over 1000C? Only the thermocouples on the RPV head are attached mechanically.

NUCENG

Quote by Cire

According to GE they are actually a Type T Thermocouples with a 350C upper limit. They are magnetically attached which is another big problem. Does anyone know of a magnet that still works when heated over 1000C? Only the thermocouples on the RPV head are attached mechanically.

My bad, thermocouples were dropped for RG 1.97 per
http://pbadupws.nrc.gov/docs/ML1109/ML11098A049.pdf

You are correct about type T range. Thanks for the correction.

*Barneysee*

Quote by joewein

On June 1 the remain decay heat output in unit 1 was 3.7 MW while in units 2 and 3 it was 6.3 MW, which is 0.26% of thermal output at shutdown. Over the next 8 months that will go down to 0.21% of thermal output at shutdown, so it's essentially steady now (source), since most of the iodine-131 and other shortlived isotopes are largely gone.

Joe, the data you use to estimate the current heat output assumes that there was no leakage of nuclides as has happened at Fukushima.

The actual current heat output should be considerably less than those figures.
From your source:

"This data is not produced from measured data on the actual reactors at Fukushima, but from using a well established model that is routinely used to estimate decay heat from shutdown reactors.

#9044 Jorge Stolfi

once the fuel is completely molten, the radioactive elements that remain in the liquid corium will produce 30% of the decay heat power that would be produced by the intact fuel;
the other 70% of the decay heat power is due to more volatile elements that will end up elsewhere.

joewein

Thanks for pointing that out. I had forgotten about that...

So assuming the cores completely melted in all three units, the current heat output of the cores should be more like 1.2 MW in unit 1 and 2.1 MW in units 2 and 3.

The balance of 2.5 MW in unit 1 and 4.2 MW in units 2 and 3 should mostly be in the leaked water, on RPV and containment walls and around pipes, wherever evaporated volatile isotopes could condensate or get leached out.

Does anybody remember how many curies of Cs-134 and Cs-137 were leaked into the atmosphere according to NISA estimates?

MiceAndMen

Quote by Cire

According to GE they are actually a Type T Thermocouples with a 350C upper limit. They are magnetically attached which is another big problem. Does anyone know of a magnet that still works when heated over 1000C? Only the thermocouples on the RPV head are attached mechanically.

What document is that from?

There is a lot that is unknown about thermal properties during a core melt event.

http://www.tec-sim.de/images/stories...-phenomena.pdf

On page 16 of that document:

Though in the TMI-2 accident no external cooling was available, the vessel wall did not experience any noteworthy thermal attack in contradiction to what all simulations predict to date. The thermal attack on the vessel wall was limited to a hot spot in which the internal vessel wall reached temperatures of ~1100°C in a region of approximately 0.5 meter width, which was rapidly cooled after approximately 1/2 hour.

There is the distinct possibility that molten material relocated out of the RPV without necessarily requiring the entire bottom head to fail. There's also the possibility that such a magnetically attached thermocouple became "no longer attached" to the vessel at some point.

*Barneysee*

Quote by joewein

So assuming the cores completely melted in all three units, the current heat output of the cores should be more like 1.2 MW in unit 1 and 2.1 MW in units 2 and 3.

Considering the tens of thousands of gallons of water which have washed through the containment, those numbers would be an unlikely to achieve upper limit.

But with the good comes the bad - more from Jorge:

Quote by Jorge Stolfi

On the other hand the corium will contain many long-lived isotopes.................

While the contribution of an element to the heat production rate is inversely proportional to its half-life (among other things), its potential for health damage is largely independent of it, at least for lifetimes up to a decade or two. So, while the corium keeps 30% of the decay heat production, it may include a larger fraction of the total health damage potentia of the original fuel.

Thus the decay from this point will be at a slower rate due to the predominance of long-lived isotopes.

In effect, we are now at the same point a plant which had a normal shutdown would have been - several decades later.

htf

Quote by Cire

They are magnetically attached which is another big problem. Does anyone know of a magnet that still works when heated over 1000C?

Cobalt would be a Candidate (T_c ~ 1400K). This is the material with the highest Curie temperature I know of.

Cire

Quote by htf

Cobalt would be a Candidate (T_c ~ 1400K). This is the material with the highest Curie temperature I know of.

Do you use a magnet that can withstand those temperatures when the sensor itself is only designed to measure 350C? It seems like that would be prudent to do so.

I'll have to do some more research and see if I can identify the magnetic material used.

Omega sells several type of magnetic thermocouples. The only note I could find stated "Magnet Will Retain 90% of Its Pull at 370°C (700°F)"

tsutsuji

http://www.nikkei.com/news/category/...0E2E2E2;at=ALL Tepco will install a new mainly-Toshiba-made backup system using zeolite for the water treatment facility, setting August as the target date. In addition to the present reverse osmosis desalination system, evaporation-enrichment systems will be installed in August and in October. Unit 4's SFP cooling system will be started in the last decade of July. Unit 1's SFP cooling system in the first decade of August.

http://www.meti.go.jp/press/2011/07/...10711008-1.pdf This is a formal NISA request requiring Tepco to write a report about its plans concerning the safety of the SFP cooling systems for unit 1 and unit 4, reminding Tepco the deadline of July 17th as part of the "step one" of the "roadmap".

http://www.tepco.co.jp/cc/press/11071309-j.html (not yet translated into English) Tepco's report on the SFP cooling systems for unit 1 and unit 4, as a reply to the above NISA request.

http://www.tepco.co.jp/en/press/corp...1071109-e.html Tepco's report on the safety of the nitrogen injection at unit 3.

http://www.tepco.co.jp/en/press/corp...1071212-e.html this press release is simply called "Water leakage in the reactor building (non-controlled area)". It turns out it is not in Fukushima Daiichi but in Kashiwazaki-Kariwa unit 5.

http://www.tepco.co.jp/cc/press/11071302-j.html (not yet translated into English) This is the second installment of the "Study regarding current seismic safety and reinforcement of reactor buildings at Fukushima Daiichi Nuclear Power Station" and it is about unit 3. The first installment, published on 28 May, was about unit 1 and unit 4 : http://www.tepco.co.jp/en/press/corp...1052801-e.html

Do you remember the figure page 78 of http://www.tepco.co.jp/en/nu/fukushi...10525_01-e.pdf (a slideshow on the "Effects of the Earthquake and Tsunami on the Fukushima Daiichi and Daini Nuclear Power Stations" published in May) showing "Installation of a Backup RHRS pump" to provide sea water cooling for unit 5 or unit 6 ? Whenever I was looking at that picture, I had the painful feeling that the hose would break on the sharp edge of the water intake bank. The artist who drew the picture was not wrong. This is really what happened on 3 July and you probably still have the "hose turned into a fountain" picture released on that day : http://www.tepco.co.jp/en/news/11031...s/110703_1.jpg in your mind. Here is a follow-up :

On July 3, the leakage of seawater at one of outlet piping in residual
heat removal system was detected at Unit5. Though we made countermeasures
to protect the pipe from concrete block corner, same piping condition was
found at the other place in the investigation. From the viewpoint of
preventive maintenance, we stopped residual heat removal system at 6:30
am on 13 July (outside temporary seawater cooling pumps stopped at 6:44
am) and replaced piping.
http://www.tepco.co.jp/en/press/corp...1071301-e.html

And, as usual, another leak today. Where ? At the water treatment facility of course :

http://www.tepco.co.jp/nu/fukushima-...10713_01-j.pdf (page 1) Flushing was started at 11:00 AM on 13 July. While flushing was being performed, a leak was found near the coupling part of a chemical injection line at the coagulation-sedimentation facility at 01:07 PM. But it is a different location from the leak that occurred on July 10th and July 12th. Flushing has been stopped and the leak is being investigated.

http://www.nikkei.com/news/headline/...E39F9FEAE2E2E2 the leaked volume is 5 l. Another PVC fitting is being changed for a stainless steel one. The target utilization rate of the facility is lowered from 80% to 70% for July. However 90% is set as the target for August. With an 80% rate, it would become impossible to reach the goal of treating all the 200,000 tons within this year.

http://www.asahi.com/national/update...107130512.html the utilization rate for the week from 6 July to 12 July was 73%, which is 3 points lower than the 76% achieved a week earlier.

http://www.tepco.co.jp/nu/fukushima-...10713_01-j.pdf (page 2) At around 01:00 PM, the portable monitoring post at the main gate was displaying a zero value. After checking there was nothing abnormal there, the power supply at the seismic-isolated building was restarted at 02:55 PM, which restored a normal value.

clancy688

Quote by joewein

Does anybody remember how many curies of Cs-134 and Cs-137 were leaked into the atmosphere according to NISA estimates?

Cs-134: 1.8E16 Bq, ~486.000 Curie
Cs-137: 1.5E16 Bq, ~405.000 Curie

Source: http://www.kantei.go.jp/foreign/kan/...ttach_04_2.pdf

NUCENG

Quote by htf

Cobalt would be a Candidate (T_c ~ 1400K). This is the material with the highest Curie temperature I know of.

Nuclear plants have tried to eliminate use of cobalt due to neutron activation to Co60 which is a high energy gamma dose source.

htf

Quote by Cire

Do you use a magnet that can withstand those temperatures when the sensor itself is only designed to measure 350C? It seems like that would be prudent to do so.

I don't think so, either. Obviously the designers of the reactors thought: "The RPV won't go beyond 350°C because it must not. If it does a failing temperature sensor is the least problem."

tsutsuji

Responding to a message of the Science Council of Japan, and with the purpose of learning the lessons from Japan, the French Académie des Sciences is publishing a report on the seismic and nuclear events in Japan. The first 2 parts on the earthquake and on the nuclear accident were published on 28 June with a number of attachments at http://www.academie-sciences.fr/acti...t/rads0611.htm . A third part on the medical consequences is not ready yet.

It is written in French, but an English translation is provided for the main text. Here is an excerpt :

The Japanese seismologists responsible for the forecast were convinced that the probability of an earthquake occurring could be calculated in a rational manner, using the definition of characteristic earthquakes for each region. The forecast map, therefore, had not made any provision for an earthquake of magnitude higher than 7.5 in the area closest to the continent and 8.2 closer to the trench. The Tohoku earthquake had a magnitude of 9.0-9.1. On the basis of this forecast, the tsunamis accompanying the earthquakes were not predicted to exceed 4 to 5 metres on reaching the coast. The Tohoku triggered tsunami measured between 15 to 20 metres. The Fukushima nuclear power station site had been built to protect the infrastructures from tsunamis less than 5.7m in height upon reaching the coastline, whereas this tsunami just off the reactor sites measured 14 m with respect to the sea’s normal level.

The main error made by the Japanese specialists was to consider that the past century of seismic events was representative of the continuous, ongoing subduction process. It is, however, known that subduction zones can produce earthquakes equal to or higher than magnitude 9, with lateral movements in excess of 20 to 30 metres, due to stress accumulated over several centuries, i.e., a much longer period than the Japanese specialists had used for their forecasts. The fact that major earthquakes, magnitude 7.5 to 8 had relieved part of the elastic deformation did not preclude that a megathrust earthquake could follow, and indeed this was the case on March 11, 2011. The seismic energy dissipated over the past century only represents 20% of the energy represented by the progressive dip of the Pacific plate sliding under the Japanese archipelago.

(...)

The geological and historic records show that very big tsunamis had hit the Tohoku coastline in years 1611 and 869, and the residual traces are much greater than those left by the earthquakes over the past century (although the lesser magnitude earthquake that occurred in 1896 did produce some really impressive damage)! The cycle for major tsunamis occurring lies between 500 and 1,000 years.

The building of a dense GPS network (30 km between stations) following the Kobe earthquake in 1995 allows scientists to demonstrate that the elastic deformation observed in Japan as a result of the progressing Pacific Plate corresponded to a slip rate close to 80 mm/year, i.e., almost 100% of the subduction rate and not 20% as had been conjectured.

(...)

The Tohoku earthquake serves to show that any forecast based on recent data proves inadequate. We must therefore take both historic and geological data into account if we wish to characterise seismicity over a span of at least several centuries, better still over several millenniums.

pages 10-11 http://www.academie-sciences.fr/en/rads0611_en.pdf

HowlerMonkey

I'm not sure the engineers of 40 years ago had the tools we are using to critique thier reasoning.

*Barneysee*

Quote by HowlerMonkey

I'm not sure the engineers of 40 years ago had the tools we are using to critique their reasoning.

While they wouldn't have known of the 2004 Indonesian tsunami, the story about big tsunami in Alaska would have been in their local newspapers.

Tsunamis are a well known feature of the Pacific rim, especially Japan.

October 1707 an 8.4 earthquake and tsunami 25.7 meters high hit the Kochi Prefecture

April 1771 earthquake magnitude 7.4 near Okinawa - tsunami is thought to have killed about 12,000 people, the highest seawater runup on Ishigaki Island, range between 30 meters and 85.4 meters.

Nov 1854 The Ansei Quake on the south coast of Japan, was actually 3 quakes, two magnitude 8.4 quakes and a 7.4 quake. The first on near what is today Aichi Prefecture and Shizuoka Prefecture with tsunami. maximum wave of 28 meters at Kochi, Japan, the earthquake and tsunami killed 3,000 people.

June 1896 earthquake in northeastern Honshu - tsunami reached a height of 100 feet, 1896 (magnitude 7,2 / wave height 36m)

September 1923 The Great Kanto Earthquake - eastern Japan devastated Tokyo, Yokohama and the surrounding areas, caused tsunamis with waves reaching 12 meters.

1933 (magnitude 8,4 / wave height 28m): http://en.wikipedia.org/wiki/1933_Sanriku_earthquake

1964 in Alaska (at the time Fukushima was being designed) Mag 9.2, tsunami 27-foot (8.2 m)

The waves produced by the 2004 Indonesian tsunami were (27m) high and killed 230,000 people, that seems a fair warning to the current generation.

I agree that we should let bygones be bygones, but let's not make excuses for bad decisions.

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HowlerMonkey	I'm not sure the engineers of 40 years ago had the tools we are using to critique thier reasoning.