Japan Earthquake: nuclear plants Fukushima part 2

[Rive]

Just two photos documenting the sampling of the water and sediment at the bottom of Unit 1 PCV, carried out yesterday.

If that guy really dares to keep the sample in hand, then there is no way it's fuel.

 

[Gary7]

Were i looking for Corium i'd turn off the lights and look in the water for telltalle blue glow of Cerenkov .

Would there still be Cherenkov radiation after 6 years and considering all the impurities in the melt and the deformed geometry, etc...?

 

[jim hardy]

Would there still be Cherenkov radiation after 6 years and considering all the impurities in the melt and the deformed geometry, etc...?

honestly - i don't know whether there'd be enough to see. With the lights out our whole spent fuel pit was aglow. Of course the fresher the element the brighter.

 

[etudiant]

There are several immediately accessible SFPs on the site that could be used to test the idea. Their fuel loadings also date from the accident or prior.
However, the water in the reactor structures is not especially clear according to the images sent back thus far. Would that dim the glow too much?

 

[mheslep]

Would there still be Cherenkov radiation after 6 years and considering all the impurities in the melt and the deformed geometry, etc...?

There are photo multiplier based devices available to pick up the Cherenkov from a single beta decay. As far as what can be seen by eye from fuel in water:

Cherenkov radiation can be used to detect high-energy charged particles (especially beta particles). In nuclear reactors or in a spent nuclear fuel pool, beta particles (high-energy electrons) are released as the fission fragments decay. The glow is visible also after the chain reaction stops (in the reactor). The cherenkov radiation can characterize the remaining radioactivity of spent nuclear fuel, therefore it can be used for measuring of fuel burnup.

http://www.nuclear-power.net/nuclea...-particles/beta-particle/cherenkov-radiation/

 

[turi]

I still haven't seen any info on the unit 1 probe sampling, it has been more than 10 days now. Does anybody know how long approximately such an analysis takes?

 

[Sotan]

Indeed, for a long time I wasn't able to find anything on that subject - not on the Japanese sites either.
Today I found this video of the regular press conference of yesterday April 20:
http://iwj.co.jp/wj/open/archives/374829 (in Japanese)

After the initial data presentation by Tepco people, the first reporter's first question (at 08:05) is:

Watanabe reporter from Jiji Tsushin: "Regarding the sampling that was done at Unit 1 the other day, how much has the analysis advanced?"
Mr. Okamura from Tepco: "We together with Hitachi are still evaluating the data. As soon as we put together some results we will inform you.. We are still analyzing."
Watanabe reporter: "When do you think there will be some data available?"
Mr. Okamura: "At this point I have not heard of any specific time or deadline being set. IRID and Hitachi are verifying the data. After the results are delivered to Tepco we plan to make that information available to you all."

Edit: now that I got to that site I also took a look at an older press conference (led there by the titles on the site, which - by the way - are quite criticizing as regards Tepco).
So, in the press conference of April 3, the spokesperson of Tepco explains that on site they only have available a "simple X-ray fluorescence analysis" method with which to analyze the sample of water and sediment taken from Unit 1 PCV. If I understood correctly, it's a device that bombards the sample with X-rays and then records a spectrum of the radiation emitted, which allows - based on certain specific wavelenghts - the identification of different substances from the sample. Unfortunately, this kind of "simple X-rays analysis" requires a certain amount of... sample, and it appears that when they took the sample it was mostly water, and therefore they have trouble obtaining results. More complicated but also more effective techniques for analysis are available but they require transporting the sample off-site as well as much more time. (So this might explain why it takes so long to get some results, they are actually analyzing the sample in other places, with stronger methods.)

 

[turi]

Muon measurements will be executed at unit 3 as well:
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2017/images/handouts_170424_01-e.pdf

 

[Charles Smalls]

Muon measurements will be executed at unit 3 as well:
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2017/images/handouts_170424_01-e.pdf

Again only scanning the RV bottom head and above? Pointless.

 

[etudiant]

Again only scanning the RV bottom head and above? Pointless.

What would you recommend? If they can establish that the reactor vessel is largely empty, that is a starting point.

 

[jim hardy]

Again only scanning the RV bottom head and above? Pointless.

Pointless ?

What if they find the core in there ?

 

[Charles Smalls]

What would you recommend? If they can establish that the reactor vessel is largely empty, that is a starting point.

Unit 3 had one of the more severe loss of coolant events and is arguably the most damaged of the three.

To target muon scanning with the reactor bottom head as the lowest observation point suggests they expect that same unit to have faired better than 1 and 2. That is illogical.

The better thing to do would be to lower the observation window. The muon and robot investigations of 1 and 2 show clear signs of melt through. Use the findings from the sister units to adapt the investigation strategy. Target the pedestal area in the scan of unit 3. These results would help gather information that could benefit the picture of all 3.

 

[Hiddencamper]

Unit 3 had one of the more severe loss of coolant events and is arguably the most damaged of the three.

To target muon scanning with the reactor bottom head as the lowest observation point suggests they expect that same unit to have faired better than 1 and 2. That is illogical.

The better thing to do would be to lower the observation window. The muon and robot investigations of 1 and 2 show clear signs of melt through. Use the findings from the sister units to adapt the investigation strategy. Target the pedestal area in the scan of unit 3. These results would help gather information that could benefit the picture of all 3.

Unit 3 had its HPCI system in operation until it stalled out on steam pressure. Then it repressurized and level dropped, until the Automatic Depressurization System actuated. ADS ensured the core was depressurized prior to onset of core damage. This means when the vessel finally ruptured it's possible that you didn't had massive debris relocation due to steam explosion or vessel breach.

It doesn't hurt to try to look in the rpv.

 

[Charles Smalls]

Unit 3 had its HPCI system in operation until it stalled out on steam pressure. Then it repressurized and level dropped, until the Automatic Depressurization System actuated. ADS ensured the core was depressurized prior to onset of core damage. This means when the vessel finally ruptured it's possible that you didn't had massive debris relocation due to steam explosion or vessel breach.

It doesn't hurt to try to look in the rpv.

I need to learn more on the Muon imaging technique to get a clear idea of how strict the field of view is, but if it's shaped like the diagrams depict, I think they should have shifted the target area down a few degrees to observe the bottom head and pedestal area instead. There was known to be prolonged period where the fuel was uncovered so it's more likely than not it relocated to the bottom of the vessel if not actually penetrating the RV bottom head.

Two questions for the board: Whereabouts in Unit 3 do we think the explosion occurred? Also, is there a clear timeline of the key events leading up to the Unit 3 melt down written in this thread anywhere? The Wikipedia time lines for Units 1 and 2 are quite good but the one on Unit 3 is quite poor. Thanks in advance for any info as ever : )

 

[jim hardy]

Whereabouts in Unit 3 do we think the explosion occurred?

that's pure speculation
estimates of its energy support the hydrogen hypothesis .

i heard one very early speculative.reference to 'flattop'
there's lots of tinfoil misinformation floating about the internet .

My advice is Stick with the TEPCO analyses.
Sotan has diligently kept us well apprised, Thanks Sotan !

 

[Charles Smalls]

that's pure speculation
estimates of its energy support the hydrogen hypothesis .

i heard one very early speculative.reference to 'flattop'
there's lots of tinfoil misinformation floating about the internet .

My advice is Stick with the TEPCO analyses.
Sotan has diligently kept us well apprised, Thanks Sotan !

I think you may have misread my comment. I'm talking about the "steam explosion or vessel breach" that Hidden Camper mentioned in his comment. I'm asking if there is an official opinion from TEPCO or a common consensus here on where inside Unit 3 the explosion occurred.

 

[jim hardy]

I'm asking if there is an official opinion from TEPCO or a common consensus here on where inside Unit 3 the explosion occurred.

If you find one please share it !

Best I've heard is copious hydrogen in lower reaches of building and that's why black plume was so near vertical.
There exist photos of bent rebar pointing into what i believed at the time(mid 2011) to be sfp or refueling canal.

old jim

 

[krater]

I don't ever remember seeing any follow up information regarding the unit 3 large equipment hatch which was (as I understood it) found open in an early investigation. Was a connection ever drawn between this finding and the likely scenario they posit for subsequent hydrogen explosion in the reactor building?

Edit: Sorry, I am actually referring to the equipment hatch shield plug; the hatch itself was found to be mostly intact but heavily water damaged if I recall.

 

[turi]

Installation of muon measurement device has finished and measurements started:
http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170502_02-j.pdf

 

[Rive]

Was a connection ever drawn between this finding and the likely scenario they posit for subsequent hydrogen explosion in the reactor building?

As I recall, no. There was a similar shield plug relocation found in a different reactor (which was not damaged), so it was accounted on the EQ.

 

[turi]

Irid has a new press release about a "common platform" to be used during fuel debris removal to install individual tools as needed on top of the RPVs:
http://irid.or.jp/en/topics/燃料デブリ取り出し工法の検討「原子炉圧力容器1/

 

[Delta Force]

I haven't been able to find an answer on this, but I'm wondering if there was any attempt to try to vent radioactive gas from the damaged reactors to prevent an explosion, as was successfully done at Three Mile Island. I know some of the reactors that didn't explode had holes cut in their roof, but was there any attempt made at the other reactors?

 

[nikkkom]

I haven't been able to find an answer on this, but I'm wondering if there was any attempt to try to vent radioactive gas from the damaged reactors to prevent an explosion, as was successfully done at Three Mile Island. I know some of the reactors that didn't explode had holes cut in their roof, but was there any attempt made at the other reactors?

There is a 710 page thread on this very site which was tracking the accident live:

https://www.physicsforums.com/threads/japan-earthquake-nuclear-plants.480200/

I bet you can find some detailed, day-by-day information there.

 

[Rive]

I haven't been able to find an answer on this, but I'm wondering if there was any attempt to try to vent radioactive gas from the damaged reactors to prevent an explosion, as was successfully done at Three Mile Island. I know some of the reactors that didn't explode had holes cut in their roof, but was there any attempt made at the other reactors?

'Venting' has a very special meaning when it's about reactors. It's about releasing gases from within the containment of the unit. It is different than 'venting' gases from the rest of the building.

'Venting' happened, on all reactors as far as I remember now.

The building of U1 and U3 exploded before anything could be made about gases in the building//outside the containment. The explosion of U4 was completely unexpected, since it was out of order - and it is not clear that the hole on U2 had anything to do with the fact that the building of U2 did not exploded.

 

[nikkkom]

There is a 710 page thread on this very site which was tracking the accident live:

https://www.physicsforums.com/threads/japan-earthquake-nuclear-plants.480200/

I bet you can find some detailed, day-by-day information there.

...as well as a glimpse at the disconnect between real reliability of nuclear power stations and what nuclear proponents were thinking about it back then:

"""
Mar 12, 2011
At the moment, I don't see a 'real' chance of a meltdown. It is a worst case scenario, which is what licensing space is all about.
Some of the worst case scenarios involve extraordinary, and not necessarily physical real situations. It's a bit like crash testing a car by dropping it out of an airplane at several thousand feet, knowing full well that such a car would never be able to achieve such a velocity on level ground since the engine could not achieve the speed or the tires would blow out well before the speed could be achieved.
"""
(^^^^^^ the above post was written at the time when in reality, Unit 1 fuel has melted already)
"""
Mar 12, 2011
So it's already off and won't explode? Cool, thanks.
"""
(and the very next post is...)
"""
Mar 12, 2011
It looks like the containment building has exploded. My educated guess is, what they feared might happen at TMI has happened here. The core melted down, releasing lots of hydrogen gas in the chemical reaction with the cladding, which then ignited.
"""

 

[nikkkom]

"""
Mar 13, 2011
A shame, because this is shaping up to be a textbook example of nuclear safety. Most of the backups and emergency procedures failed, yet it looks like little radiation has been or will be released. Considering this is a forty year plant that happened to be very near one of the largest earthquakes ever recorded, I'd say nuclear power is vindicating itself.
"""

Yeah right...

 

[turi]

From the end of May 2017 to the beginning of July Tepco will conduct a more detailed survey of the operating floor of unit 1:
http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170518_04-j.pdf

 

[HowlerMonkey]

"""
Mar 13, 2011
A shame, because this is shaping up to be a textbook example of nuclear safety. Most of the backups and emergency procedures failed, yet it looks like little radiation has been or will be released. Considering this is a forty year plant that happened to be very near one of the largest earthquakes ever recorded, I'd say nuclear power is vindicating itself.
"""

Yeah right...

Yeah...a textbook 9.0 earthquake followed by a 49 foot tsunami.

 

[Cire]

Yeah...a textbook 9.0 earthquake followed by a 49 foot tsunami.

I'm trying to think of another industrial/power complex that could have survived a 9.0 quake and 49 foot wave with so little death from the failure of the plant. More people (workers) have been killed in the cleanup by accident then people have been killed by the power plant itself and the release of radiation.

 

[Sotan]

A lot of new information on Tepco's website (unfortunately only in Japanese at this moment).

http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170522_01-j.pdf
Progresses and present state of the processing of water from the buildings basements.

http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170522_03-j.pdf
Mainly about progresses in handling and reducing the radioactivity of water from rain that washes the buildings and soil of the plant.

http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170522_02-j.pdf
(Periodic report on) Reducing the risks in case of earthquake. Mainly deals with 1) plans to dismantle the "smoke stack" of Units 1-2, and 2) Measures to reduce the tsunami risks as regards the sludge resulted from various operations of decontamination

http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170522_04-j.pdf
A review of the PCV investigations carried out until now, with some considerations regarding the ones that will follow.

http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170522_05-j.pdf
Reducing the amount of cooling water pumped into Reactors 1-3

Not enough time to post more now but as I look through them I might add more later.

 

[Astronuc]

Mar 12, 2011
At the moment, I don't see a 'real' chance of a meltdown. It is a worst case scenario, which is what licensing space is all about.
Some of the worst case scenarios involve extraordinary, and not necessarily physical real situations. It's a bit like crash testing a car by dropping it out of an airplane at several thousand feet, knowing full well that such a car would never be able to achieve such a velocity on level ground since the engine could not achieve the speed or the tires would blow out well before the speed could be achieved.
"""
(^^^^^^ the above post was written at the time when in reality, Unit 1 fuel has melted already)
"""

Actually, post is dated March 11, 2011, 9:15 pm EST.
https://www.physicsforums.com/threads/japan-earthquake-nuclear-plants.480200/#post-3182924

That was before any information of the severity of the damage to the units was available. At the time, I, and many others, were unaware that the emergency cooling systems had been disabled and power lost inside units 1, 2 and 3.

According to reports, "On the morning of March 12, the core of Unit 1 melted, and the hydrogen explosion occurred in the reactor building at around 3:30 p.m," which would about 5 hours after my post on March 11. It is not necessary for the core to melt to generate hydrogen. If the Zircaloy reached temperatures ~1000 - 1200°C (melting point = 1850°C), there could be a vigorous oxidation reaction production large quantities of hydrogen gas, i.e., the generation of hydrogen would occur before core melting. They had certainly lost cooling of the core.

 

[Astronuc]

You were believing what nuclear industry was telling us all these years after Chernobyl: all is well, we have many redundant safety systems, we absorbed lessons from TMI-2 and Chernobyl, we are prepared, meltdown can't realistically happen. I was believing them too, BTW. They were empirically proven to be lying.

I wasn't believing anything. I based my statement on the evidence I had at the time. My viewpoint changed when I learned more about the situation. Once they lost Unit 1, that indicated it was a very serious event, and I was suggesting it might reach a level 5 or worse if they couldn't get cooling water in the reactors. I knew it was seriously bad once they started pumping seawater into the cores.

The 15-m tsunami was a beyond design basis event. We learned later that their site characterization had ignored previous data of comparable tsunamis from history along the northeastern coast of Honshu. In 1964, the Great Alaska earthquake resulted in tsunami runups of up to 100 ft ( ~ 30 m), so nuclear plants along the Pacific coast should have had that in their design basis. However, we also saw where much of the coast line was not protected against the tsunami that occurred.

 

[turi]

Information about underwater ROV to be used for investigation of unit 3 pedestal area:
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2017/images/handouts_170525_01-e.pdf

 

[Hiddencamper]

I wasn't believing anything. I based my statement on the evidence I had at the time. My viewpoint changed when I learned more about the situation. Once they lost Unit 1, that indicated it was a very serious event, and I was suggesting it might reach a level 5 or worse if they couldn't get cooling water in the reactors. I knew it was seriously bad once they started pumping seawater into the cores.

The 15-m tsunami was a beyond design basis event. We learned later that their site characterization had ignored previous data of comparable tsunamis from history along the northeastern coast of Honshu. In 1964, the Great Alaska earthquake resulted in tsunami runups of up to 100 ft ( ~ 30 m), so nuclear plants along the Pacific coast should have had that in their design basis. However, we also saw where much of the coast line was not protected against the tsunami that occurred.

The information coming out was limited and it really seemed like TEPCO themselves didn't know what was going on. It was also confusing because the Daiichi and Daini sites both had events and the media was mixing them up, and I remember a bad report that Daiichi had cooling on all units verified when they really meant Daini.

What really made me understand the magnitude of the event was probably 2 or 3 days later when I saw a picture of their vital switchgear half submerged. I quickly realized that was probably not recoverable. I never had been to a plant with vital switchgear below ground level. Once that info got out it was evident significant core damage was likely going to occur.

 

[Hiddencamper]

So what are you saying? If/when any other nuclear plant in the world would have its electrical wiring permanently damaged by a disaster, we should expect some new Cs-137 plumes on our maps? That's it? We shouldn't expect [edited by mod] nuclear power can be safely kept from melting without electricity?

If both engines fail on a plane with hydraulic or electrical flight controls, which most commercial aircraft have, then the auxiliary power unit must start to get the hydraulics running to ensure the plane can land safely, even if it is a forced landing. In the event the APU fails there is still a ram air turbine that uses wind speed to drive hydraulics, but if that also fails a loss of plane and cabin is essentially guaranteed to happen.

Expecting everything to be 100% safe is unrealistic. The goal is to ensure risk is low enough that it is on par with other generally safe practices like air travel, which also happens to require active safety systems.

Loss of electrical distribution is even worse than loss of AC power because it precludes short term recovery or mitigating actions. From a risk perspective it is a pretty safe bet to say that core damage frequency is going to be very bad unless you have alternate ways to provide mitigation without using permanent plant equipment like b5b or FLEX. Japan didn't implement a program like b5b, and obviously FLEX didn't exist then. Today you have FLEX to provide motivation even following a loss of all on site systems. Personally I don't expect radiation release if the associated countries implemented a FLEX or similar extensive damage mitigation program.

Btw I don't appreciate your attitude.