Fukushima Japan Earthquake: nuclear plants Fukushima part 2

Click For Summary
A magnitude-5.3 earthquake struck Fukushima, Japan, prompting concerns due to its proximity to the damaged nuclear power plant from the 2011 disaster. The U.S. Geological Survey reported the quake occurred at a depth of about 13 miles, but no tsunami warning was issued. Discussions in the forum highlighted ongoing issues with tank leaks at the plant, with TEPCO discovering loosened bolts and corrosion, complicating monitoring efforts. There are plans for fuel removal from Unit 4, but similar structures will be needed for Units 1 and 3 to ensure safe decontamination. The forum also addressed the need for improved groundwater management and the establishment of a specialist team to tackle contamination risks.
Engineering news on Phys.org
  • #122
rmattila said:
This argument is very difficult for me to follow, as the very idea behind the design in the 80's was to eliminate the need for unreliable decision-making in the case of a severe accident by enabling a completely passive initiation of venting. If your vent lines don't have filters, you probably want to keep the valves in the lines closed, and must count on the personnel to be able to open them at the right time.

I agree that installing filters is the right approach, and the NEI efforts against the filters are misguided. But I still don't agree with characterizing this as a cheap or easy modification. And the filters aren't a silver bullet that solves all of the issues. Just my 2-cents.
 
  • #124
gmax137 said:
I agree that installing filters is the right approach, and the NEI efforts against the filters are misguided. But I still don't agree with characterizing this as a cheap or easy modification. And the filters aren't a silver bullet that solves all of the issues. Just my 2-cents.

Again, no argument that filters are no silver bullet and are not just a slap on fix.
Nevertheless, they do seem a sensible addition to the 'defense in depth' concept, without substantial downsides. Even the cost is moderate, especially considering the potential damage avoided. Frankly, they seem to me to be an obviously needed element for any hardened venting.

Separately, thank you again, hiddencamper, for the clarification on the difference between depressurization and containment venting. It helps clarify why it took three days for the Fukushima reactors to get to explode, which actually is even more depressing, that no cooling could be reestablished for so long.
Is there any good reason, other than cost and regulatory uncertainty, why filters should not be added to the hardened vents?
 
  • #126
etudiant said:
... Is there any good reason, other than cost and regulatory uncertainty, why filters should not be added to the hardened vents?

I think [strike]Exelon[/strike] NEI is standing on the principle that the regulator should establish requirements in measurable terms (such as, offsite dose or dose rate limits) and the licensee should do the engineering to design the features that result in those requirements being met. This is the essence of what "performance-based" means in nuke-speak. This principle has always been a source of tension within the regulating body (AEC or NRC), going back into the early 1960s. Also, the utility engineers still remember the costs associated with a number of the NRC-mandated post-TMI modifications that turned out to be pointless engineering and operational quagmires (e.g., H2 monitors in the large dry PWR containments, post-accident sampling systems, etc.). Whether the filters are a good place to take this stand is debatable in my mind, because (like you said) they seem to be such an obvious application of defense-in-depth (another long-standing principle which is sometimes forgotten).
 
  • #127
gmax137 said:
I think [strike]Exelon[/strike] NEI is standing on the principle that the regulator should establish requirements in measurable terms (such as, offsite dose or dose rate limits) and the licensee should do the engineering to design the features that result in those requirements being met. This is the essence of what "performance-based" means in nuke-speak. This principle has always been a source of tension within the regulating body (AEC or NRC), going back into the early 1960s. Also, the utility engineers still remember the costs associated with a number of the NRC-mandated post-TMI modifications that turned out to be pointless engineering and operational quagmires (e.g., H2 monitors in the large dry PWR containments, post-accident sampling systems, etc.). Whether the filters are a good place to take this stand is debatable in my mind, because (like you said) they seem to be such an obvious application of defense-in-depth (another long-standing principle which is sometimes forgotten).

Since we are talking here about 'beyond design basis' accidents, is the NEI stance sensible?
If the Ramapo fault causes a serious failure at Indian Point and NYC gets the vented plume, it might impair nuclear industry shareholder value more substantially than any filter retrofit.
 
  • #129
a.ua. said:
There are leaks in the containment of the reactor 1.

Hm. Can you get more specific? Where in the containment? Looking at the PDF it appears there's a penetration at the elbow of the steam downcomer, as it exits the PCV. But maybe I'm misreading the schematic?
 
  • #130
It depends on what is considered the boundary containment.
In fact, this handset is in a sand layer between the steel and concrete primary containment.?
Look at the photo.
 
  • #131
According to this article, they will be using the boat mounted camera a second day.

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201311140046
 
Last edited by a moderator:
  • #132
there is already an "photo.tepco.co.jp/en/date/2013/201311-e/130313-04e.html"
and the second day of the Japanese
 
Last edited by a moderator:
  • #133
a.ua. said:
There are leaks in the containment of the reactor 1.


Isn't that jumping to a conclusion?

Yes, Tepco say there is water coming out of one of the sandbed drain\s but the source of the water is unknown isn't it?

It could be a leak in the containment steel liner but it could be water finding its way down there on the outside of the liner between the liner and the concrete or it could be from some other source. There is a reason why the sand bed has drains in the first place.

It's interesting though.
 
  • #134
etudiant said:
Since we are talking here about 'beyond design basis' accidents, is the NEI stance sensible?
If the Ramapo fault causes a serious failure at Indian Point and NYC gets the vented plume, it might impair nuclear industry shareholder value more substantially than any filter retrofit.

Since it's beyond design basis it really depends on the philosophy. If you are beyond design basis, it means something unpredictable or extremely unlikely disabled all the safety systems which were in place. So on one hand its challenging to say another filter will survive the same accident to help, but if the filter does survive it will no doubt be a help for extreme damaging events.
NEI's position (and it was actually EPRI that studied this, NEI took the stance after the EPRI report), is that the portable equipment from FLEX can meet filtration goals after an extreme event. But really...at this point its more of, do we feel that a containment ventilation filter is necessary to minimize release to the public, or can we minimize those releases using existing methods without challenging the ability to cope with an extreme event.

Personally I think it depends on the plant design. Take my current plant for example, (Mark III containment, very different from Mark I/II in a LOT of ways) has so many cross connects that we can realign systems to vent to water tanks already on site, meaning we can do wet scrubbing without needing an additional filter and get those >1000 decontamination factors. We also have had training and portable equipment in place since 9/11 to flood the basement of our fuel storage building and vent through there. Also note that our Mark III design has 5 existing filter trains (which can be repowered by a portable generator) and 3 separate containment venting systems (regulations changed so much during the Mark III construction that all Mark IIIs ended up with multiple vents for containment. This is also a reason why Mark IIIs are currently exempt from venting requirements). So in my plant's case, I think an external filter doesn't add much value, we already have equipment staged, know what to do, and can implement solutions with limited actions (no need to do massive repiping).

For Mark I/II plants, its kind of a different story. Limited vent paths, few if any system cross connects, no good floodable volume. Maybe depending on the specific design filters are a sensible solution. I don't know...
 
  • #135
The talk about re-aligning systems is over-optimistic for sure. Power might be out, places where valves are might be inaccessible for a reason or another. You need water and pumps and time, one or more of which might be lacking.

Generally speaking, you are telling us that active measures are as good as passive ones, which is simply not true.
With a pre-emplaced filter at the end of a hardened vent line, all the operators have to do, to vent safely, is exactly nothing - as compared to running around the plant in the dark, in unknown radiation field, to open valves and start-up pumps under time pressure, while lugging around gensets.

There's the matter of expertise too. To realign cooling systems and whatnot, you need to know the plant. To hook up a fire engine, you need to know exactly nothing, just find the right connector (big red pipe, conspicuously marked, by the side of the access road). All the operators could be dead (or evacuated, as was almost the case with Fukushima), and you'd still successfully flood the containment while the passive vent+filter keeps emissions down.
 
Last edited:
  • #136
zapperzero said:
The talk about re-aligning systems is over-optimistic for sure. Power might be out, places where valves are might be inaccessible for a reason or another. You need water and pumps and time, one or more of which might be lacking.

Generally speaking, you are telling us that active measures are as good as passive ones, which is simply not true.
With a pre-emplaced filter at the end of a hardened vent line, all the operators have to do, to vent safely, is exactly nothing - as compared to running around the plant in the dark, in unknown radiation field, to open valves and start-up pumps under time pressure, while lugging around gensets.

There's the matter of expertise too. To realign cooling systems and whatnot, you need to know the plant. To hook up a fire engine, you need to know exactly nothing, just find the right connector (big red pipe, conspicuously marked, by the side of the access road). All the operators could be dead (or evacuated, as was almost the case with Fukushima), and you'd still successfully flood the containment while the passive vent+filter keeps emissions down.

If you think during a severe accident that there's going to be some easy way to do ANYTHING you're going to have a bad time.

All nuclear plants have containment isolation systems that automatically close the valves on the pipes passing through containment. Almost all of these systems consist of valves just inside and just outside of containment, meaning if the isolation occurred (like at Fukushima), that you cannot use most of these lines without going inside containment, which really isn't an option during a severe accident. You would need a deep knowledge of the plant, or existing pre-staged procedures and equipment (like the ones the US has had since 9/11) to know which lines likely did not isolate, or know which lines only have isolation valves outside of containment. Example, the third LPCI (Low pressure coolant injection) system at my plant only has an outboard containment isolation valve, (the inboard valve is a check valves), and this is readily accessible and could be a good place to hook a fire truck up to.

The point I'm trying to make, is in all causes you will need to take manual actions. That is the definition of how a severe accident works. If you didn't need manual actions, then you wouldn't be in the severe accident in the first place. There is nothing passive that's going to help you. "Passive" filter? Only if you can get the first outboard valve open (and approval to have a pipe penetrating containment without double isolation). Or are we saying that these valves are going to be pre-aligned to start venting automatically (which means during DBAs like a LB-LOCA where my ECCS is working, I'm going to allow unacceptable and unnecessary radioactive releases because my passive filter is going to take care of it?, when my safety systems on site could readily handle it)

You can all pontificate all you want about how you think it should work, but you need to understand the design of these plants, along with the regulatory design requirements, to understand where the challenges are in just saying that some passive thing can be installed that will magically solve all your problems post accident. No matter what, it will take significant efforts by those at the plant to cope with a beyond design basis accident, with or without a filter.
 
  • #137
westfield said:
Isn't that jumping to a conclusion?

Yes, Tepco say there is water coming out of one of the sandbed drain\s but the source of the water is unknown isn't it?

It could be a leak in the containment steel liner but it could be water finding its way down there on the outside of the liner between the liner and the concrete or it could be from some other source. There is a reason why the sand bed has drains in the first place.

It's interesting though.

It is true that speculative errors could be made. However when reading the pdf and watching the video, I am under the impression that the clearly visible gushing water is not coming from the detached sandbed drain pipe, it is coming from the S/C side of the vent pipe, and flowing down the side of the S/C torus. They clearly mention in the PDF not just leakage from the drain pipe, but from the vent pipe in this location, and this is also shown in the photos taken from the video.

Going further into the realms of speculation, I am very interested in this discovery. There are obviously multiple reasons why a vent pipe failure could have occurred in this area, and I should not leap to inclusions. But I will keep in mind that some core melt studies do have the area around the vent pipe as being a strong potential pathway for corium flow. And although I do not believe we have a definitive answer as to the location of the pedestrian pedestal opening for reactor one, the south east direction is a strong contender, and that happens to be the location of the vent pipe where this leak has been found. None of this is enough to form strong conclusions, but given that reactor 1 had in theory the strongest melt potential for several reasons, and that the radiation levels in its torus room are far more interesting than those of the other reactors, I am both fascinated and unsurprised by what the boat has found.
 
  • #138
The second day of reactor 1 torus room boat investigation is available in English. Some damage to other sandbed pipes was detected, but no other vent pipe damage other than the one at location 4 was detected as far as I can tell.

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_131114_05-e.pdf

Regarding reactor 4 pool fuel removal, various certificates have now been obtained and one of the transportation casks is now inside the reactor 4 building.

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_131113_12-e.pdf
 
  • #139
Such high doses that there are measured
(and in the torus is 2.2 Sv) can only nuclear fuel.

It's a pity, they did not use the gamma camera, then it would all be seen.

many high-quality photos from the mission boat

http://www.fukuleaks.org/web/?p=11733
 
Last edited:
  • #140
Hiddencamper said:
If you think during a severe accident that there's going to be some easy way to do ANYTHING you're going to have a bad time.

No matter what, it will take significant efforts by those at the plant to cope with a beyond design basis accident, with or without a filter.

Agree entirely, severe accidents are like wars, even the simplest thing becomes very difficult.
The concern is that the regulators are missing the good in their effort to achieve perfection.

That said, it is just incomprehensible to me that a nuclear vent stack should be unfiltered. It may never be needed, hopefully, but it sure is much more useable with a filter than without.
Venting relatively safely should be another option for the operator, not a desperation necessity.
 
  • #141
Hiddencamper said:
If you think during a severe accident that there's going to be some easy way to do ANYTHING you're going to have a bad time.
I don't, so I think it is all the more important to ensure that there will be as few things to do as possible.

You would need a deep knowledge of the plant, or existing pre-staged procedures and equipment (like the ones the US has had since 9/11) to know which lines likely did not isolate, or know which lines only have isolation valves outside of containment. Example, the third LPCI (Low pressure coolant injection) system at my plant only has an outboard containment isolation valve, (the inboard valve is a check valves), and this is readily accessible and could be a good place to hook a fire truck up to.
This is exactly the kind of thing I am talking about. This need for in-depth knowledge is a vulnerability in and of itself.

The point I'm trying to make, is in all causes you will need to take manual actions. That is the definition of how a severe accident works. If you didn't need manual actions, then you wouldn't be in the severe accident in the first place.
So we could include future Fukushima-type scenarios in the set of non-severe accidents, if only we had the means to obviate the need for manual actions when they happen. Cool!

There is nothing passive that's going to help you. "Passive" filter? Only if you can get the first outboard valve open (and approval to have a pipe penetrating containment without double isolation). Or are we saying that these valves are going to be pre-aligned to start venting automatically (which means during DBAs like a LB-LOCA where my ECCS is working, I'm going to allow unacceptable and unnecessary radioactive releases because my passive filter is going to take care of it?, when my safety systems on site could readily handle it)

I was thinking more along the lines of a vent line with a rupture disk set at some level where you can be reasonably sure that some break will soon develop somewhere else anyway and another line which is controlled with valves in the usual manner. Of course, since this kind of stuff is already in production (rmatilla has posted lots of details a while ago iirc?), I don't need to think much :).
Also, who said anything about unacceptable releases? If your filter is big enough, and it gets used, you won't ever release anything unacceptable, no?
 
  • #142
a.ua. said:
Such high doses that there are measured
(and in the torus is 2.2 Sv) can only nuclear fuel.
I would not jump to that conclusion so fast. There was that vent tower bottom, with around 10Sv/h as I recall, far away from the containment...
 
  • #143
a.ua. said:
Such high doses that there are measured
(and in the torus is 2.2 Sv) can only nuclear fuel.

2.2 Sv/h is not really high enough for nuclear fuel. IIRC the bottom of Fukushima vent stack is 10 Sv/h - and that clearly can't be fuel, it's too far from the reactor building, so it must be fission products.

In Chernobyl, corium typical levels (e.g. "elephant foot") were in 10-100 Sv/h range.
 
  • #144
This news article seems to indicate uncertainty about what the TEPCO pdf reports call a vent pipe leak.

http://www.japantimes.co.jp/news/20...er-reactor-1-containment-vessel/#.UofgPJHXVhw

Another leak was confirmed just above the suppression chamber, which is a huge donut-shaped chamber connected to the containment vessel, and one of eight vent pipes.

The suppression chamber contains water and is used to reduce pressure inside the containment vessel through vent pipes.

Akira Ono, chief of the Fukushima No. 1 plant, said of the second leak that there is another pipe above the suppression chamber and the vent pipe, and it appears that the water is leaking from around that pipe.

But Ono said it is still unknown where exactly the leak is located, and that it is conceivable the water is coming from the containment vessel.

Still, “these are significant findings to help” find the precise locations of the leaks, he said.
 
  • #145
Rive said:
I would not jump to that conclusion so fast. There was that vent tower bottom, with around 10Sv/h as I recall, far away from the containment...

the most realistic option

8504373979_5c88526823_o.jpg


It looks like near the edge

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120627_02-e.pdf
-------------------------------------------------------------------

the change in the exposure rate indicates the source of a torus.
At 3 meters (10 feet) from the edge of the bubbler. (Tor)

http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130220_03-j.pdf

https://www.physicsforums.com/showpost.php?p=3978192&postcount=13510



http://ru.fotoalbum.eu/images1/200905/95064/273731/00000058.JPG
http://www-pub.iaea.org/iaeameetings/IEM4/30Jan/Suzuki_d.pdf
 
Last edited:
  • #146
nikkkom said:
2.2 Sv/h is not really high enough for nuclear fuel. IIRC the bottom of Fukushima vent stack is 10 Sv/h - and that clearly can't be fuel, it's too far from the reactor building, so it must be fission products.

In Chernobyl, corium typical levels (e.g. "elephant foot") were in 10-100 Sv/h range.

It all depends on the time and distances,
at the moment: 2.6 years decay,
2-3 kg of nuclear fuel will give 2 Sv, at the distance of 1 meter, without shielding metal or concrete.
 
  • #147
a.ua. said:
the most realistic option
url]http://www-pub.iaea.org/iaeameetings/IEM4/30Jan/Suzuki_d.pdf[/url]

Thank you, a.ua., for an excellent set of very informative links.
I am honestly impressed by the Japanese effort, which is a far cry from the public media presentation of bumbling incompetence.

Two elements that jump out from the presentation:
1 The plan is to shorten the cooling loop, by sealing the reactor buildings and recycling their cooling water internally. Needs compact decontamination/heat exchange system to be developed and retrofitted, a tall order.
2 The SFP 3 is the next target, after the SFP 4 is cleared. That will require work in a much more messy environment. It seems a very bold step to me.

I can't help but think that the SFP4 cleanup and the work on the ground water are the low hanging fruit here. Anything beyond that will take real developments and come after the Tokyo Olympics, not before.
 
  • #148
etudiant said:
Agree entirely, severe accidents are like wars, even the simplest thing becomes very difficult.
The concern is that the regulators are missing the good in their effort to achieve perfection.

That said, it is just incomprehensible to me that a nuclear vent stack should be unfiltered. It may never be needed, hopefully, but it sure is much more useable with a filter than without.
Venting relatively safely should be another option for the operator, not a desperation necessity.


The stacks have filters on them though. They just aren't very effective without electricity...which gets us back to the original problem lol
 
  • #149
a.ua. said:
the most realistic option

Still don't think so. Mind the assumed position of the core debris, and the strong shielding effect of the water during the measurements you linked!

I think it's simply from the contaminated water from the torus. That water is still from the first days of the accident, with Cs levels at the 10^6 range (or even higher).

To clarify this: I don't saying that there are *no* core debris in the torus. I'm just saying that the radiation levels are not sufficient to imply that there are.

etudiant said:
1 The plan is to shorten the cooling loop, by sealing the reactor buildings and recycling their cooling water internally. Needs compact decontamination/heat exchange system to be developed and retrofitted, a tall order.
2 The SFP 3 is the next target, after the SFP 4 is cleared. That will require work in a much more messy environment. It seems a very bold step to me.

Neither of those goals are really difficult. They will get some experience soon with freezing, as they trying to seal the trenches, and actually they are working on decontaminating the top of U3. They should be able to 'cut down' the turbine buildings and set up an acceptable working conditions on top of U3 on planned order.
 
  • #150
Hiddencamper said:
The stacks have filters on them though. They just aren't very effective without electricity...which gets us back to the original problem lol

Thank you for this input!
Learn something surprising every day.
I clearly don't understand how these filters work, that they need to be powered.
Do they require blowers or electrostatic precipitators to perform properly?
Do you know if this requirement is also true for the Nordic installations that were discussed earlier?
 

Similar threads

M7.5 Earthquake, near Anamizu, W Japan
  • · Replies 5 ·
Replies
5
Views
4K
Japan Earthquake: Nuclear Plants at Fukushima Daiichi
  • · Replies 14K ·
473
Replies
14K
Views
4M
Fukushima Fukushima Daiichi nuclear disaster discussions
  • · Replies 12 ·
Replies
12
Views
49K
Fukushima Are US Nuclear Power Plants Prepared for Earthquakes?
  • · Replies 5 ·
Replies
5
Views
6K
Japan Earthquake: nuclear plants - Daini (Plant 2)
  • · Replies 6 ·
Replies
6
Views
16K
Two Mag 6.0 earthquakes off NE coast, Iwate, Japan
  • · Replies 5 ·
Replies
5
Views
3K
Mag 6.7 earthquake near Tomakomai, Hokkaido, Japan
  • · Replies 3 ·
Replies
3
Views
4K
Magnitude-6.5 earthquake - Southern Japan
  • · Replies 16 ·
Replies
16
Views
4K
Japan Earthquake: Political Aspects
  • · Replies 763 ·
26
Replies
763
Views
274K
6.7 Mag Earthquake near Makurazaki, Japan (E. China Sea)
  • · Replies 1 ·
Replies
1
Views
3K