Japan Earthquake: nuclear plants Fukushima part 2

[nikkkom]

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.

 

[jadair1]

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.

 

[LabratSR]

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."

 

[LabratSR]

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."

 

[nikkkom]

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.

 

[a.ua.]

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.

 

[etudiant]

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.

 

[LabratSR]

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

 

[LabratSR]

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

 

[LabratSR]

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

 

[HowlerMonkey]

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

 

[nikkkom]

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?!

 

[LabratSR]

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

 

[nikkkom]

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.

 

[SteveElbows]

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.

 

[nikkkom]

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.

 

[LabratSR]

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

 

[etudiant]

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.

 

[LabratSR]

Rummaging around tonight I stumbled upon a couple of docs that deal with venting.


CONSIDERATION OF ADDITIONAL REQUIREMENTS FOR CONTAINMENT VENTING SYSTEMS FOR BOILING WATER REACTORS WITH MARK I AND MARK II CONTAINMENTS

http://www.nrc.gov/reading-rm/doc-collections/commission/secys/2012/2012-0157scy.pdf



Investigation of Strategies for Mitigating Radiological Releases in Severe Accidents

http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001026539

 

[nikkkom]

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?

 

[LabratSR]

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.

 

[etudiant]

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?

 

[zapperzero]

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?

 

[LabratSR]

I found this on the TEPCO site. The second page shows the vent system.

http://www.tepco.co.jp/en/nu/kk-np/safety/images/130804_01.pdf

 

[rmattila]

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).

 

[etudiant]

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?

 

[rmattila]

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.

 

[Bandit127]

BBC Video Inside Unit 4

On the page there is a video from above the SFP in Unit 4. Posted yesterday.
(I hope they haven't put restrictions on viewing it internationally).

http://www.bbc.co.uk/news/world-asia-24847381

 

[nikkkom]

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.

 

[Hiddencamper]

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.

 

[nikkkom]

All this paperwork was added because practice showed that without it, nuclear industry does not execute due diligence and does not make their plants safe enough.

As to this particular filter, I don't see why it is not installed on the existing vent line, why a new vent line needs to be added (as opposed to "existing vent line is cut, and a detour through the filter is inserted into the cut"). This way, all changes are way outside containment.

 

[gmax137]

All this paperwork was added because practice showed that without it, nuclear industry does not execute due diligence and does not make their plants safe enough...

well that's debatable; but I think hiddencamper's exposition was really responding to etudiant's "fairly inexpensive" comment. The point is, even simple mods are hugely expensive in ways that are hard to imagine if you haven't worked in that world.

 

[Hiddencamper]

All this paperwork was added because practice showed that without it, nuclear industry does not execute due diligence and does not make their plants safe enough.

As to this particular filter, I don't see why it is not installed on the existing vent line, why a new vent line needs to be added (as opposed to "existing vent line is cut, and a detour through the filter is inserted into the cut"). This way, all changes are way outside containment.

There are many plants that don't do due diligence even with the paperwork. (Browns ferry...)

The idea for all the paperwork is due to configuration management. For every plant that is "built", there are 3 plants. The regulatory required plant, the designed plant (also known as the "paper plant"), and the physical plant itself.

When a plant is licensed, the regulator is actually saying that the paper plant is good enough to meet or exceed the regulatory required plant. The plant is then built per the paper plant, and QA/QC/testing performed to ensure the physical plant was built in conformance with the paper plant.

As far as the regulator is concerned, the paper plant is what you are licensed to, so anytime you want to make a change to the plant, you first have to update your paper plant. Then you go and do the licensing side to either demonstrate that you are still bounded by the approved regulatory plant design model, OR you get permission to deviate from that (license amendment). Then, finally, when all that is done, you are allowed to update the physical plant to bring it into conformance with the paper plant.

It really has nothing to do with diligence. The reason for all the paper work, is that is how you prove that your plant design can actually meet regulatory objectives.

As for the filter, remember that for design basis accidents the filter is not required at all. It only helps with beyond design basis accidents. For beyond design basis accidents, remember that in order to get into a beyond design basis accident, something extraordinary had to occur to make your ECCS fail. Putting a filter inside the plant just makes it vulnerable to the same common event which caused you to lose your ECCS in the first place (not to mention that Mark I/II plants have no place to put something inside their secondary containment, they are space limited and seismic/structural limited).

So just throwing a filter into the plant may look good to the public, but in reality it doesn't mean the filter will work for those beyond design basis events which you really need it for. Having the valves and equipment inside the plant means that you now have to send people into very high rad (lethal?) fields to open and close those valves (remember no guarantee of electricity). So really, you want this equipment to be outside the plant, in an enclosure that is hardened far beyond that of the plant itself, such that the events which would cause you to lose your plant ECCS (plane crashes, large tornados, extermely heat/frost, extremely flooding, tsunamis) don't cause you to lose the filter as well, and give you the ability to control the release rate from outside the high rad field. You would also need to make sure that the system doesn't breach containment during design basis accidents like LOCA, where you DO have your ECCS and you absolutely want to keep ALL the material inside containment.

 

[etudiant]

Is this not fiddling while Rome burns?
We have an illustration that the emissions from an uncontained failure post shutdown can be dramatically exacerbated by unfiltered venting. Instead of a local accident, we have hundreds of square kilometers made uninhabitable, at a cost in the multiple billions, possibly hundreds of billions.
Yet we are haggling over 10s or at most 100s of millions. Is there no International Atomic Energy Agency that can draw rational conclusions and set minimal world wide standards for nuclear installations?

 

[nikkkom]

It really has nothing to do with diligence. The reason for all the paper work, is that is how you prove that your plant design can actually meet regulatory objectives.

And you need to prove that because it is a *nuclear* plant, not a gas-fired one. Gas-fired plants have quite more relaxed rules.
Nuclear plants are more strictly regulated because accidents can be much worse than on a natural gas plant, and general public (via elected government, parliament and laws enacted by them) does not trust private owners to be careful enough without oversight.
That was my point.

So just throwing a filter into the plant may look good to the public, but in reality it doesn't mean the filter will work for those beyond design basis events which you really need it for.

Yes, it does not mean that it will work. It means that it MAY work. Say, 90% chance that it will. I bet Fukushima operators would *much* appreciate that instead of what they had!

So really, you want this equipment to be outside the plant, in an enclosure that is hardened far beyond that of the plant itself, such that the events which would cause you to lose your plant ECCS (plane crashes, large tornados, extermely heat/frost, extremely flooding, tsunamis) don't cause you to lose the filter as well

This filter is a passive device. In Fukushima, to survive tsunami it would need to only be secured to the ground strongly enough to not float away.