Fukushima Japan Earthquake: nuclear plants Fukushima part 2

AI Thread 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.
  • #51
tsutsuji said:
fukushima daiichi decommissioning countermeasure promoting conference, 8th secretariat meeting, 26 september 2013

5-6 preparations for fuel debris removal

http://www.meti.go.jp/earthquake/nuclear/pdf/130926/130926_01kk.pdf suppression chamber inner water level measurement robot generic technology development qualification test (prompt report)

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Engineering news on Phys.org
  • #52
http://www3.nhk.or.jp/news/genpatsu-fukushima/20131013/1145_kashou.html The United Nations' scientific comittee on the effects of atomic radiation (UNSCEAR) says Tepco could have underestimated the workers' exposure caused by the accident by 20% as a result of not taking account short lived elements such as Iodine 133.

http://www.un.org/Docs/journal/asp/ws.asp?m=A/68/46 UNSCEAR report (General Assembly Official Records Sixty-eighth session Supplement No. 46)
 
  • #53
Fukushima Daiichi decommissioning countermeasure promoting conference, 6th secretariat meeting, 25 July 2013 : http://www.meti.go.jp/earthquake/nuclear/20130725_01.html


Mid and long term roadmap progress presentation by Tepco:

http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01a.pdf Agenda
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01b.pdf Participants

1-1 Plant status
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01c.pdf Plant parameters
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01d.pdf Accumulated water storage and treatment status
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01e.pdf Unit 3 reactor building steam-like thing generation

2
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01f.pdf Mid and long term roadmap progress status (abstract)

3 Study and execution in each field

3-1 Cooling by closed loop water injection
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01g.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01h.pdf Unit 2 TIP guide tube soundness check results and future response
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01j.pdf Unit 1 nitrogen injection modification test results
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01k.pdf Unit 2 S/C nitrogen injection test for the purpose of hydrogen purge (second time) (abstract)

3-2 Treatment of accumulated water
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01m.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01n.pdf Future response to multinucide removal facility batch treatment tank leakage
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01p.pdf Ground water bypass progress status
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01q.pdf Underground water storage tank response status

3-3 Countermeasures to reduce environmental radiations
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01r.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01t.pdf Measurement results of groundwater east of turbine buildings
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01u.pdf Specialist study group on the reduction of radioactive substance concentrations in the port seawater
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01v.pdf Unit 2 water intake electric power cable trench sampling investigation results
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01w.pdf Assessment results of additional releases from reactor buildings (as of July 2013)
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01x.pdf Present status and countermeasures against seaside ground water and seawater radioactive substance concentration rise problem

3-4 Improvement of working conditions
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01y.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01z.pdf Revision of the domain of duties of female employees working in the nuclear activities at Fukushima Daiichi Nuclear Plant

3-5 Countermeasures for spent fuels pools
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01aa.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01bb.pdf Layout map of working areas of units 1, 3 and 4 top part debris removal work and covering work for the purpose of fuel removal
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01cc.pdf Unit 3 top part debris removal work
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01dd.pdf Unit 4 reactor building covering work
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01ee.pdf Spent fuel storage status (as of 20 July 2013)
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01ff.pdf End of exterior panels installation on the outer walls and roof of unit 4 cover for the purpose of fuel removal
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01gg.pdf End of grounding work for unit 4 fuel handling machine

3-6 Preparations for fuel debris removal
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01hh.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01jj.pdf Removal of obstacles cuh as the debris on the 1st floors of unit 1 and unit 3 reactor buildings
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01kk.pdf Results of inspection around the PCV penetrations on high locations in unit 2 reactor building first foor
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01mm.pdf Execution of unit 2 PCV internal reinvestigation

3-7 Treatment and disposal of radioactive waste
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01nn.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01pp.pdf Debris, cut down trees management status
http://www.meti.go.jp/earthquake/nuclear/pdf/130725/130725_01qq.pdf Cut down tree container temperature trends
 
  • #54
www.tepco.co.jp/cc/press/betu13_j/images/130830j0101.pdf Facilities for fuel removal from the spent fuel pool (447 pages, Japanese, released on 30 August 2013)

It contains new information about the fresh fuel removed from unit 4, and the removal facilities being installed in unit 4.
 
  • #55
Thank you again, Tsutsuji-san, for your sustained work keeping us posted on the progress of the cleanup effort.
Without your help, there would not be any reasonably non partisan information available to English language speakers about this work.
Meanwhile, it seems the 'nuclear village' is gradually starting to come to grips with the problem and developing new solutions to overcome the many difficulties involved.
I was struck by the intensity of the radiation inside Reactor 2, estimated to be 24-36 Sv/hr along the CRD replacement rail, rising as the probe approached the pedestal. That high a level more than 2 years after the accident means the site will be inaccessible to people for many years yet.
Working in that framework will require entirely new techniques. Hopefully the Japanese government will be able to rally the nation to make this cleanup a cause for all Japan, because it will take a national effort to achieve.
 
  • #56
etudiant
estimated to be 24-36 Sv/hr along the CRD replacement rail, rising as the probe approached the pedestal. That high a level more than 2 years after the accident means the site will be inaccessible to people for many years yet.

However there is nothing stopping just open the door to the containment and send the robot.

The Soviet Union used a toy, a toy tank, (the price 10 $ ).
2 years after ...
Then they saw "shining" to 100 Sv:smile:

however is meaningless walk there now.
you just need to stop the leak.
 
  • #57
a.ua. said:
etudiant


However there is nothing stopping just open the door to the containment and send the robot.

The Soviet Union used a toy, a toy tank, (the price 10 $ ).
2 years after ...
Then they saw "shining" to 100 Sv:smile:

No argument that ingenuity is also found outside of Japan.
Still, I'm impressed that they seem to have developed a device that will reliably measure water levels inside the torus from the outside, despite the radiation and contaminated water in the measurement space.
As for the leaks, they now seem to be a chronic rather than a critical issue.
Afaik, the contamination level of the leaking water is about 1% of what it was in the early days of the crisis, so even if it takes 20 years to plug the leaks, the additional pollution is maybe 20% of what has already been released.
If TEPCO can empty the reactor 4 spent fuel pool as planned, starting next month, it would be a clear signal to the world that the cleanup is making real progress.
 
  • #58
etudiant said:
Thank you again, Tsutsuji-san, for your sustained work keeping us posted on the progress of the cleanup effort.
Without your help, there would not be any reasonably non partisan information available to English language speakers about this work.
Meanwhile, it seems the 'nuclear village' is gradually starting to come to grips with the problem and developing new solutions to overcome the many difficulties involved.
I was struck by the intensity of the radiation inside Reactor 2, estimated to be 24-36 Sv/hr along the CRD replacement rail, rising as the probe approached the pedestal. That high a level more than 2 years after the accident means the site will be inaccessible to people for many years yet.
Working in that framework will require entirely new techniques. Hopefully the Japanese government will be able to rally the nation to make this cleanup a cause for all Japan, because it will take a national effort to achieve.

Just how dangerous is 24-36 Sv/hr, I'm a math and electronics guy and do not know much about radiations possible effect on people.

Could properly protected people work in a field like that?
 
  • #59
jadair1 said:
Just how dangerous is 24-36 Sv/hr, I'm a math and electronics guy and do not know much about radiations possible effect on people.

Could properly protected people work in a field like that?
lethal dose is 7-8 Sv/h, people can work when there is 0,5 Sv/h max during nuclear accident and 1 Sv/h when the are saving other people's live
 
  • #60
jadair1 said:
Just how dangerous is 24-36 Sv/hr, I'm a math and electronics guy and do not know much about radiations possible effect on people.

Could properly protected people work in a field like that?

Mind the "/h" part.
Allowed dose (for a year) for workers protecting life in emergency is 250mSv, protecting valuables in emergency is 100mSv, otherwise 50mSv (US standards, as far as I know).

First direct symptoms due radiation (absorbed in a short period) expected around 400mSv.

So in field 25 Sv/h a worker is permitted to work for ~ 0.05/25= 0.002h which is ~ 7.2 seconds if I did the math correctly.
Fatal dose is around 4Sv (in this case this limit would be 'earned' within 10-15minutes).The time limit can be extended with some special clothing (check some Chernobyl vids).
 
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  • #61
Rive said:
The time limit could be extended with some special clothing (check some Chernobyl vids).
For lead the half-value thickness for 2 MeV gamma radiation is 1.4 cm. That's one heavy suit... And it makes you probably working half as fast than working without it, eliminating its usefulness.
 
  • #62
more practical to use a protective shield of lead.
Given that the source of dot.
Similar protection (much lightly built) were seen in the photo of Fukushima Unit 4.
on the north side.
 
  • #66
a.ua. said:
etudiant


However there is nothing stopping just open the door to the containment and send the robot.

The Soviet Union used a toy, a toy tank, (the price 10 $ ).
2 years after ...
Then they saw "shining" to 100 Sv:smile:

however is meaningless walk there now.
you just need to stop the leak.

The issue is getting into containment requires using large gantry cranes to lift the massive shield plugs in front of the containment hatches, then breaching 2 airlocks, which, when breached, will contaminate the **** out of the reactor building and provide a pathway for a lot of shine. What also makes it challenging is the subpile room is not at the same elevation as the entry hatches, and requires some vertical maneuvering which would be challenging for a robot. I'm not positive if Mark Is have a separate hatch going into the subpile room undervessel, but I have seen hatches like that before.

At Chernobyl, they had no containment, so it was a matter of drilling through spots then running the toy tank in. But I'm sure you saw the video, those guys were less than stellar about limiting their exposure and would do what they could to hide it. Now a days, with digital dosimeters, you can't even do that unless you are doing something to blatently shield your dosimeter.

Without an understanding of the physical layout of the BWR containment system its hard to understand why you can't just send a robot on. As someone who was in a BWR drywell chamber within the last week, you pretty much need scaffold to get anywhere important. The only areas you can easily access are the reactor recirculation pumps, and usually there is a permanent ladder up to the SRV/MSIV mezz
 
  • #69
I was poking around the Oak Ridge website and stumbled across this interesting report that was released in April.

Fukushima Daiichi – A Case Study for BWR Instrumentation and Control Systems Performance during a Severe Accident

http://info.ornl.gov/sites/publications/Files/Pub42256.pdf
 
  • #71
LabratSR said:
I was poking around the Oak Ridge website and stumbled across this interesting report that was released in April.

Fukushima Daiichi – A Case Study for BWR Instrumentation and Control Systems Performance during a Severe Accident

http://info.ornl.gov/sites/publications/Files/Pub42256.pdf

Basically, most instrumentation was useless as soon as power went out. Nobody ever accounted for such a possibility.
 
  • #72
nikkkom said:
Basically, most instrumentation was useless as soon as power went out. Nobody ever accounted for such a possibility.

That is the problem, Tepco looked at the possibility of a major earthquake and resulting tsunami but did nothing to protect the plant from them.

They knew they were vulnerable but did nothing as it would have cost too much.
 
  • #73
nikkkom said:
Basically, most instrumentation was useless as soon as power went out. Nobody ever accounted for such a possibility.

As detailed in the report, Preface pages xi - xiii, Some data was certainly being recorded after the power loss.

"Operators were dispatched to hazardous areas of the plants’ reactor buildings to obtain
instrument readings and to control systems because of lack of power to main control rooms."
 
  • #74
jadair1 said:
That is the problem, Tepco looked at the possibility of a major earthquake and resulting tsunami but did nothing to protect the plant from them.

They knew they were vulnerable but did nothing as it would have cost too much.

You're being kind compared to these guys. I suggest the html, version 1 and 2 over the download versions

Executive Summary

http://warp.da.ndl.go.jp/info:ndljp/pid/3856371/naiic.go.jp/en/report/

"Our report catalogues a multitude of errors and willful negligence that left the Fukushima plant unprepared for the events of March 11. And it examines serious deficiencies in the response to the accident by TEPCO, regulators and the government.

For all the extensive detail it provides, what this report cannot fully convey – especially to a global audience – is the mindset that supported the negligence behind this disaster."
 
  • #75
jadair1 said:
That is the problem, Tepco looked at the possibility of a major earthquake and resulting tsunami but did nothing to protect the plant from them.

They knew they were vulnerable but did nothing as it would have cost too much.

The $64 billion question now is how to stop this sort of management failure from happening.
If we can't stop it, then nuclear power generation has no future.
 
  • #76
From the report WANO "Lessons learned from the accident at the Fukushima Daiichi nuclear power plant":

TEPCO conducted training on severe accidents for executives using computer learning tools . Although the teaching materials covered a wide range of problems , it lacked certain details that might contribute to the development of a critical approach to the assessment of critical parameters, including awareness of the limited control of the instrument in an emergency . For example, in teaching materials no information about the concept of a surge in the capillaries of instruments measuring the level in the reactor vessel , which leads to a false notion of a higher level in the reactor , as opposed to the lower - the real one. Relying on computer training programs, which are organized with a fairly low frequency , management contributes to the appearance of vulnerability in the preservation of knowledge and depth of understanding.
 
  • #77
nikkkom said:
The $64 billion question now is how to stop this sort of management failure from happening.
If we can't stop it, then nuclear power generation has no future.

As the astronomical cost of the Fukushima disaster becomes clearer, it should gradually dawn on everyone associated with the nuclear enterprise that belt and suspenders prevention is very economical indeed. Filtered venting, dry fuel storage and such are just more band aids.
The industry needs to embrace ultra safe designs, aiming at set and forget operations as the key parameter. Unfortunately, none of the current fleet of reactors come close to that ideal. That suggests a very large opportunity for innovation left unexploited.
 
  • #78
Preliminary Summary Report

The Follow-up IAEA International Mission on remediation of large contaminated areas off-site the Fukushima Daiichi

http://www.iaea.org/newscenter/focus/fukushima/remediation-report-211013.pdf
 
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  • #79
TEPCO plans a new ‘freeze’ mission in underground tunnels at Fukushima Daiichi

http://enformable.com/2013/10/tepco-plans-new-freeze-mission-underground-tunnels-fukushima-daiichi/NHK link with video

http://www3.nhk.or.jp/nhkworld/english/news/20131022_32.html
 
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  • #80
I've been trying to find this report for months.

S.R. Greene was one of the original members of the BWR Severe Accident study group at Oak Ridge and this is a post Fukushima report.

THE CANARY, THE OSTRICH, AND THE BLACK SWAN: AN HISTORICAL
PERSPECTIVE ON OUR UNDERSTANDING OF BWR SEVERE ACCIDENTS
AND THEIR MITIGATION

http://media.wix.com/ugd/903593_97ef117ecbca067e9d76cd699e3be5dc.pdf
 
  • #81
A lot of the recent posts belong not here but rather in the "political thread".

This thread is part two of a thread discussing the physics and science behind the continuing events there.

Please relegate the finger pointing to the proper thread that is linked below so we can keep this thread on topic.

https://www.physicsforums.com/showthread.php?t=486089
 
  • #82
etudiant said:
As the astronomical cost of the Fukushima disaster becomes clearer, it should gradually dawn on everyone associated with the nuclear enterprise that belt and suspenders prevention is very economical indeed. Filtered venting, dry fuel storage and such are just more band aids.

However, current design continue to operate, and while I do want to see new reactor designs to be better, I'm more concerned that even "band-aids" as you say aren't implemented fast enough.

For example. It's been 2.5 years since Fukushima. Still no filtered vents on US reactors?!
 
  • #83
nikkkom said:
However, current design continue to operate, and while I do want to see new reactor designs to be better, I'm more concerned that even "band-aids" as you say aren't implemented fast enough.

For example. It's been 2.5 years since Fukushima. Still no filtered vents on US reactors?!

That reminds me of a post by Sherrell Greene (see report above) on his blog about hardened vents. Note he doesn't take a position for or against.

http://www.sustainableenergytoday.blogspot.com/2013/03/post-79-to-vent-or-not-to-vent-that-is.html
 
  • #84
LabratSR said:
That reminds me of a post by Sherrell Greene (see report above) on his blog about hardened vents. Note he doesn't take a position for or against.

http://www.sustainableenergytoday.blogspot.com/2013/03/post-79-to-vent-or-not-to-vent-that-is.html

> Industry's position on the hardened vents can be summarized as, ..."We need to understand all the implications of the FLEX strategy before we require the plants to spend buckets of money installing hardened filtered vents."

Which is cow's excrements. "Buckets of money" in this case - adding a filter on the vent line - refers to 5-20 million dollars per reactor unit (NRC study).

Considering that filtered venting at Fukushima would drastically reduce off-site contamination (make it ~100 times less), and considering that most other countries already had filtered vents installed even BEFORE Fukushima, spending such a small sum is a complete no-brainer.
 
  • #85
nikkkom said:
Considering that filtered venting at Fukushima would drastically reduce off-site contamination (make it ~100 times less)

I have trouble believing that was the case at Fukushima, due to the large amount of contamination that came from containment failure rather than venting. Most obviously from reactor 2 where no venting appears to have taken place successfully, but also due to containment failures at the other reactors too.
 
  • #86
SteveElbows said:
I have trouble believing that was the case at Fukushima, due to the large amount of contamination that came from containment failure rather than venting. Most obviously from reactor 2 where no venting appears to have taken place successfully, but also due to containment failures at the other reactors too.

Imagine that: more than one thing went wrong at Fuku. *Including* the shocking lack of personnel training what to do in a SBO, vent or not to vent, and how to initiate venting.
 
  • #88
LabratSR said:
I'm seeing a tremendous amount of drama and outright hysteria on the internet about the upcoming removal of spent fuel from Unit 4. Here is TEPCO's release.


http://photo.tepco.co.jp/library/131030_02e/131030_01-e.pdf

This seems like a well laid out plan, with reasonable provisions for expected glitches.

Afaik, TEPCO has been categorical that there was no fire in the reactor 4 SFP, based on the absence of any alkaline signature in the SFP water as would have been inevitable if the zirconium cladding had burned. So the main challenges here are debris and rack deformation, which the clean up is prepared for.
Obviously it will be much more challenging to do the same unloading in the other 3 reactors, because of the much worse contamination. Still, if TEPCO executes well on the number 4 SFP, I think some of the Fukushima concerns will abate, simply because the frantic hype has been so overblown.
 
  • #89
  • #90
This is the filter which TEPCO installs right now at Kashiwazaki-Kariwa's vent lines.
Claimed to be capable of capturing 99,9% of contaminants.
Doesn't look too complicated or huge, right?
 

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  • #91
Some tidbits from the NRC venting doc. Enclosure 4

"[EPRI’s] findings demonstrate that substantial decontamination factors for radioactive releases can be achieved by a comprehensive strategy that includes installed equipment, operator actions and capabilities that are largely consistent with the diverse and flexible coping strategy (FLEX)."

"The EPRI report concluded that “no single strategy is optimal in retaining radioactive fission products in the containment system.” The NRC staff agrees with this conclusion. Uncertainties surrounding severe accidents resulting from accident progression, status of plant systems and components, and operator response make it highly unlikely that accidents can be modeled and procedures developed to account for all potential scenarios."

"Core debris cooling is an important element of a robust strategy for mitigating releases. If debris cooling is not provided through water injection or spray into the drywell, containment failure or bypass is likely. Without core debris cooling, the containment can be challenged in several ways. Molten debris can come into direct contact with the containment wall, melting the liner and providing a release path to the environment. Elevated drywell temperatures in the containment atmosphere can cause seals and other containment penetrations to fail, leading to containment bypass. Finally, core–concrete interactions can generate large quantities of noncondensable gases that increase containment pressure and also can accelerate concrete erosion that could challenge containment integrity over time."

"The analysis also confirmed that Mark I drywell wall breach would largely negate any additional benefit of a hardened vent and external filter, if installed, in reducing releases or in preserving secondary containment (reactor building) accessibility and subsequent usefulness of equipment installed there for stabilizing plant conditions and avoiding or minimizing additional releases."


None the less, the recommendation appears to be for Severe Accident Filtered vents.
 
  • #92
From Nikkom:
This is the filter which TEPCO intalls right now at Kashiwazaki-Kariwa's vent lines.
Claimed to be capable of capturing 99,9% of contaminants.
Doesn't look too complicated or huge, right? Seems very small indeed, especially compared to the huge venting gravel beds used by reactors in Sweden and presumably Finland.
Presumably this unit is not meant to filter the massive steam plume created by a vented reactor that has just been shut down. Does anyone have any background for this filter and how/when it is expected to be used?
Also, the Kashiwazaki site has six or seven reactors, is there just one vent line or are there several lines and filters?
 
  • #93
etudiant said:
Also, the Kashiwazaki site has six or seven reactors, is there just one vent line or are there several lines and filters?

Isn't this (part of) the so-called SGTS?
 
  • #95
etudiant said:
Seems very small indeed, especially compared to the huge venting gravel beds used by reactors in Sweden and presumably Finland.

The large gravel bed dry filter is only installed in the poorly situated and now shutdown Barsebäck NPP. Other Nordic BWRs use a compact wet scrubber filtered venting with jet nozzles injecting in NaOH water. The wet scrubber takes 99.9 % of Cs and around 99 % of elemental iodine, but unlike the large dry filter it's not very good at filtering organic iodine (perhaps 70 %) or noble gases (all pass through).
 
  • #96
rmattila said:
The large gravel bed dry filter is only installed in the poorly situated and now shutdown Barsebäck NPP. Other Nordic BWRs use a compact wet scrubber filtered venting with jet nozzles injecting in NaOH water. The wet scrubber takes 99.9 % of Cs and around 99 % of elemental iodine, but unlike the large dry filter it's not very good at filtering organic iodine (perhaps 70 %) or noble gases (all pass through).

Thank you for the additional clarification.
This makes the industry's reluctance to install or retrofit such scrubbers more puzzling to me.
It seems like a fairly inexpensive retrofit/upgrade well worth the hassle in regulatory grief avoided.
I still do not understand how this can be effective while venting a megawatt power steam plume.
Is the vent path changed to include this unit if/when the cooling water runs out?
 
  • #97
etudiant said:
Thank you for the additional clarification.
This makes the industry's reluctance to install or retrofit such scrubbers more puzzling to me.
It seems like a fairly inexpensive retrofit/upgrade well worth the hassle in regulatory grief avoided.
I still do not understand how this can be effective while venting a megawatt power steam plume.
Is the vent path changed to include this unit if/when the cooling water runs out?

See http://tvo.fi/uploads/julkaisut/tiedostot/ydinvoimalayks_ol1_OL2_ENG.pdf page 12 for a picture of the setup. The line connecting the scrubbers to the containment drywell (one of the two) has two manual valves that are kept open, and a rupture disk that will break automatically at certain containment pressure. Alternatively, for instance if the rupture disk fails to break, one of the two remaining lines can be used to bypass it by opening the manual valves in those lines. Usually the wet well line should be preferred, as it provides the additional scrubbing capacity of the condensation pool. Manual drywell path is needed if the containment is full of water and venting from wet well thus not possible.

EDIT: the picture on page 12 (page #10) is simplified and contains only one line from the drywell to the scrubber. Actually there are two as I tried to explain above.
 
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  • #98
  • #99
rmattila said:
but unlike the large dry filter it's not very good at filtering organic iodine (perhaps 70 %) or noble gases (all pass through).

I suspect no practical filter can trap noble gases.
 
  • #100
etudiant said:
Thank you for the additional clarification.
This makes the industry's reluctance to install or retrofit such scrubbers more puzzling to me.
It seems like a fairly inexpensive retrofit/upgrade well worth the hassle in regulatory grief avoided.
I still do not understand how this can be effective while venting a megawatt power steam plume.
Is the vent path changed to include this unit if/when the cooling water runs out?

As someone who works in a design department for a nuclear power plant, this type of modification is drastically more complex than it looks on the surface.

For one, you are extending containment to a location outside of the plant. You also have to add new penetrations to the containment which have a design to fail the containment in a controlled fashion. Fun fact, the primary containment is one of the only pressure vessels in all of the ASME code which is allowed to have no overpressure protection, due to the fact that it is contrary to nuclear safety for design basis accidents. There is no regulatory guidance or analysis which even supports doing something like this in the US, and if any plant did go out of their way to install it, it is very likely that it would cost easily 15-20 million dollars, and would require a rework if/when the NRC finally decides to put together regulatory guidance which explains what they think containment venting should look like.

Some design considerations that would have to be looked at (if I was preparing this engineering change authorization). Soil below where the vent unit is going to go will need geological reviews. A seismically capable pad needs to be built. The entire pipe route from containment to the vent unit and back to the elevated release point (which extends outside of secondary containment) needs seismic and weather/severe accident proof enclosures around it, and every piece of that needs calculations to determine the maximum theoretical force it can withstand to prove that it can exceed severe accident scenarios. All my leak rates for my primary and secondary containment need to be recalculated, and leak rate testing needs to be reperformed (which is challenging on the containment). The penetration work on the containment cannot be performed online, and would likely require an extended outage (not to mention that new containment penetrations have a potential risk of going bad...see crystal river 3). A lot of this work will have to go out to large external engineering firms who have the experience doing a lot of this analysis.

For me to replace a single section of pipe, or replace a single indicator in the control room, it takes about 70-80 pages of paperwork total (forms, drawing updates, authorizations, reviews, licensing analysis, testing requirements, parts list, programs impacts, procedure/training impact reviews, new vendor manuals, update forms for the master equipment list and the design basis database). For something like this, a new filter, it would likely be several thousand pages, cost over 10 million dollars in just engineering services, and take about 2 years to complete. At that point it doesn't matter if it is a "small" or "Simple" filter, the overhead cost in making changes to ASME pressure boundaries and extending containment outside of the plant is relatively astronomical. Plus when all is said and done, I need the NRC to agree to a license amendment and safety review, as this change absolutely is more than a minimal increase in the consequences of an accident (see 10CFR50.59). It takes about 1 year for the NRC to review these things, and they charge about 272 dollars per hour right now.

That's my view of it based on my experience as a design engineer at a nuclear power plant.
 

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