Japan Earthquake: nuclear plants Fukushima part 2

[etudiant]

Thank you, gmax137, for the excellent link. It provides much more focused data than the NRC news releases.
Indeed, there was no mention of the EPG Revision 4 in the NRC news releases that russ_waters so helpfully linked to.
I'd not know it ever was formulated if hiddencamper had not discussed it and pointed out that it materially changes the priorities..

I'm an interested citizen, not an industry specialist, so I rely on the industry spokespeople to supply material information.
Their selection criteria may want improving.

 

[jim hardy]

I wonder if "Nuclear News" magazine would make a gift subscription to an interested engineering student ? Surely they'd make one available to his engineering department...
http://www.ans.org/pubs/magazines/nn/
If you're an ANS member it's probably free. Most professional societies have a student rate...

there are others, but that's the one most circulated at my plant.

http://www.world-nuclear-news.org/
http://www.neimagazine.com/
http://www.nuclearplantjournal.com/old jim

 

[Astronuc]

Thank you, gmax137, for the excellent link. It provides much more focused data than the NRC news releases.
Indeed, there was no mention of the EPG Revision 4 in the NRC news releases that russ_waters so helpfully linked to.
I'd not know it ever was formulated if hiddencamper had not discussed it and pointed out that it materially changes the priorities..

I'm an interested citizen, not an industry specialist, so I rely on the industry spokespeople to supply material information.
Their selection criteria may want improving.

jim hardy gave some good examples of the trade press. ANS Nuclear News requires a subscription, although one might be able to find some comment on the ANS website (www.ans.org) and they have something called ANS Nuclear Café (https://ansnuclearcafe.org/) on which one might find some discussion of current topics.

The NRC does not take out adds in newspapers or journal regarding rule-making. They do publicize meetings and requests for public comment. Otherwise, one has to search their website with keywords.

In 2010, NRC released - https://www.nrc.gov/docs/ML1025/ML102560007.pdf (a report from 1982) - Guidelines for the Preparation of Emergency Operating Procedures

In the wake of the Fukushima disaster, the Guidelines were revisited.

The Nuclear Energy Institute (NEI) issued a report, NEI 14-01 [Revision 1], Emergency Response Procedures and Guidelines for Beyond Design Basis Events and Severe Accidents, February 2016. It's basically a summary of the industry's response to the NRC requirements for utilities to review their emergency procedures and responses. NEI 14-01 [Revision 0] - https://www.nrc.gov/docs/ML1424/ML14247A092.pdf - if interested.

On the regulatory side, there is the Code of Federal Regulations (CFR).
§ 50.34 Contents of applications; technical information.
https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0034.html

See (f) Additional TMI-related requirements, and find (ii) Establish a program, to begin during construction and follow into operation, for integrating and expanding current efforts to improve plant procedures. The scope of the program shall include emergency procedures, reliability analyses, human factors engineering, crisis management, operator training, and coordination with INPO and other industry efforts. (Applicable to construction permit applicants only) (I.C.9)

§ 50.34a Design objectives for equipment to control releases of radioactive material in effluents—nuclear power reactors.
https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0034a.html

10 CFR 50.54(q), requirements for following and maintaining in effect emergency plans
§ 50.54 Conditions of licenses.
https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0054.html

Appendix E to Part 50—Emergency Planning and Preparedness for Production and Utilization Facilities
https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-appe.html

See more on CFR here - https://www.archives.gov/federal-register/cfr

EPGs and related discussion is a whole topic for a separate thread.

 

[nikkkom]

https://www.nrc.gov/reactors/operating/ops-experience/japan-dashboard.html
This looks like a good place to start.

For BWR containments Mark I and II:
Hardened vent from wetwell is mandated.
Hardened vent from drywell is optional.
Filtering on the vents: not required.

 

[Hiddencamper]

The nrc is not supposed to be promoting the industry. That’s why it was formed and separated from the atomic energy commission.

The industry heavily tried to advertise the SAFER/FLEX program throug the nuclear energy institute. Sadly they weren’t very effective as their YouTube videos barely break 100 hits most of the time.

Revision 3 of the EPGs was issued in tandem with SAFER/FLEX for immediate response actions. Revision 4 is the major roll up that was issued June 1st this year (a few weeks ago). So there hasn’t even been much time to do anything about it.

 

[gmax137]

WANO reports on post-Fukushima improvements
http://www.world-nuclear-news.org/RS-WANO-reports-on-post-Fukushima-improvements-27061803.html

 

[Sotan]

https://www3.nhk.or.jp/nhkworld/en/news/20180726_42/
"TEPCO to retrieve suspected fuel debris"

 

[nikkkom]

Is there research on the plant response to Cs/Sr contamination from Fukushima?

Japanese being culturally inclined to be obsessed with details, I bet their scientists are examining every plant species growing in that region. Something good may come out of this: we may find plants which are extremely good at pulling Caesium from the soil. I also wonder whether removal of Cs can be improved by adding various salts to the soil.

 

[Astronuc]

Is there research on the plant response to Cs/Sr contamination from Fukushima?

Japanese being culturally inclined to be obsessed with details, I bet their scientists are examining every plant species growing in that region. Something good may come out of this: we may find plants which are extremely good at pulling Caesium from the soil. I also wonder whether removal of Cs can be improved by adding various salts to the soil.

There are numerous open articles from Nature and PNAS on studies related to Fukushima contamination and particularly Cs.

https://www.nature.com/articles/s41598-017-08261-x
Temporal changes in the radiocesium distribution in forests over the five years after the Fukushima Daiichi Nuclear Power Plant accident

One can search Nature using "Fukushima, cesium" and find numerous articles.

https://www.tandfonline.com/doi/abs/10.1080/00380768.2014.954269
Distribution of radioactive cesium in soil and its uptake by herbaceous plants in temperate pastures with different management after the Fukushima Dai-Ichi Nuclear Power Station accident

https://www.tandfonline.com/doi/pdf/10.1080/00380768.2014.1003191
Effect of the Fukushima Daiichi nuclear power plant accident on radiocesium distribution in tea fields in Saitama Prefecture: Intercultivar differences

http://www.pnas.org/content/114/42/11092
Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan

 

[Kochia]

The major risk with seawater, is it will clog the bottom debris filters for the fuel and challenge core cooling. You need to raise level above the steam dryer skirt to allow for reverse circulation over the top of the core, bypassing the debris filters. If you are in a situation where you can’t raise level that high, you risk causing damage earlier and having molten salt now. So it’s not a simple “go put seawater in”, not to mention the increased potential to degrade and damage reactor internals and dry tubes, which leads to bottom head unisolable leakage.

Thank you very much on the comment on seawater injection! For the case of Fukushima Unit 3, would it make any difference to initiate seawater injection right after HPCI was manually shutdown (due to concerns for HPCI turbine damage)? Or was it actually too late because it could lead to even more serious situation that cause earlier core damage and molten salt?

 

[Hiddencamper]

Thank you very much on the comment on seawater injection! For the case of Fukushima Unit 3, would it make any difference to initiate seawater injection right after HPCI was manually shutdown (due to concerns for HPCI turbine damage)? Or was it actually too late because it could lead to even more serious situation that cause earlier core damage and molten salt?

We talked about this I’m the last emergency procedure committee meeting. At unit 3 they were trying to open safety relief valves to keep the reactor depressurized when HPCI finally stalled out and failed so they could inject seawater. They were trying! The srvs were not opening because battery voltage was too low. Later on, the HPCI auxiliary oil pump and booster pump tripped off, and after that happened, battery voltage rose up high enough to open the srvs, but the operators weren’t aware of that. After the core was uncovered, the automatic depressurization system opened srvs to blowdown the reactor, but the operators weren’t prepared to transition to low pressure feed for that as they weren’t expecting the blowdown.

In terms of the right thing to do today, and what we are doing with contingency 1 (alternate level control) in the emergency procedures, is we want the plants to prepare alternate / low pressure injection, even if it means sea water. Then you maintain pressure low, but not so low that rcic/HPCI can’t operate properly. When you you can no longer maintain level, you blowdown the reactor before level drops below the minimum pre depressurization reactor water level, which ensures the core is never uncovered so you don’t have to deal with quenching superheated fuel. Next You flood back up over the steam separator/dryer skirt for natural circulation and to ensure your raw water can get to the fuel if the lower inlet debris strainers block up.

The debris that goes into the vessel including the salt is a challenge only if you are on it for extended periods of time (corrodes the hell out of the fuel and core internals), or if you can’t get level high enough to bypass the debris strainers which may block cooling and natural circulation.

At the end of the day, you keep the core covered at all times, even if it means poor water quality. And you try to get clean water back ASAP. You’ll probably never restart the unit if you dump seawater in while it’s hot, but if you are in the situation where all you have is seawater, not putting it in will result in core damage and never restarting the unit. So the preference is to try and keep the core cooled or at least contained even if it’s seawater.

 

[Kochia]

So two important points: 1. maintain pressure level low enough for alternate water injection without disrupting RCIC/HPCI; 2. if depressurization had to be initiated, it should be ensured that core is not left uncovered. Again thanks very much for elaboration!

 

[Sotan]

Hi all, I trust everybody is doing well. A Happy New Year to you all!

It's been quite a while since I posted in here. I did continue to follow the Fukushima news, I wouldn't say with less interest, but it did seem like the amount of news on the subject has been decreasing. I didn't find anything that felt worth posting.

Now I found this in the 12/27/18 dated "Long- and mid-term roadmap update":
http://www.tepco.co.jp/decommission/information/committee/roadmap_progress/pdf/2018/d181227_08-j.pdf
(sorry, only Japanese for now)

Looks like a new investigation into the PCV of Unit 2 is being planned for end of February 2019. This time they want to actually "pinch" the sediment located in the previous investigations.

A few points from the PDF file linked:

Page numbered 1: Short recap regarding the results of previous investigation(s). Last time, a probe was lowered through the gaps in the grating (where grating panels are gone) and, while no great damage was observed on pre-existing metallic structures, a large amount of sand-like and gravel-like "sediment" was found piled up on the floor of the pedestal. At the surface of this sediment they found the tie-plate of a fuel bundle and other fallen objects.

Pages 2-4: The newly planned investigation aims to determine some of the properties of this sediment (hardness, brittleness) as they are important in view of the future extraction operations. They will use basically the same path and method as last time - modifying only the suspended unit, which will be brought in contact with the sediment in order to assess its properties. Of course images, film, and measurements will also be taken. The unit will be equipped with a set of "mechanical fingers" which will actually probe and "feel" the sediment. As before, an airtight boundary will be set so that no gas escapes from inside the PCV.

Page 5: The new investigation unit will be equipped with a thermometer and radiation meter, will be able to rotate to look around, will have lighting to facilitate viewing and, at the bottom, will feature two "fingers" which can be opened and closed while in contact with the sediment.

Page 6 shows the area intended to be studied (the blue-line pentagon). It's a very small alrea, 400x350mm or so.

Page 7 gives the schedule. The actual investigation is to start around mid-February.

 

[Sotan]

On the road so just a quick link:
https://www.japantimes.co.jp/news/2...ation-probe-melted-reactor-fuel/#.XGR_xGmxVdY

 

[Azby]

Thanks, Sotan. Here is TEPCO's report, with photos and diagrams. Odd there's no photo of the probe itself.

https://www7.tepco.co.jp/wp-content/uploads/handouts_190213_01_e-1.pdf

 

[Sotan]

Thank you Azby.

Short film with images from the control room during the inspection:
https://www4.tepco.co.jp/library/movie/detail-j.html?catid=107299&video_uuid=i8v6r4co

And a 6 minutes film with the probe pinching the deposits:
https://www4.tepco.co.jp/library/movie/detail-j.html?catid=107299&video_uuid=yq53a9f4

 

[Azby]

Here's a nice Toshiba PR video showing the Unit 2 device being tested prior to deployment. It shows the design and operation clearly. There's also a good illustration.

https://www.toshiba-energy.com/en/info/info2019_0128.htm

 

[turi]

A new video by Tepco; the year in review:
https://www4.tepco.co.jp/en/news/library/archive-e.html?video_uuid=xh57k85s&catid=61795

 

[LabratSR]

Removal of fuel at Fukushima's melted nuclear reactor begins

https://www.latimes.com/world/la-fg...VK8kD3SN09fTf6ghjb-YnC0YSHRAGBptWEGgZrHrQIOmY

 

[Astronuc]

Removal of fuel at Fukushima's melted nuclear reactor begins

Emphasis on the spent and fresh (Unused) fuel from the pool, not the damaged core.

"Tokyo Electric Power Co. said workers started removing the first of 566 used and unused fuel units stored in the pool at Unit 3. The fuel units in the pool located high up in reactor buildings are intact despite the disaster, but the pools are not enclosed, . . . "

 

[turi]

SFP3 progress page:
https://www7.tepco.co.jp/responsibility/decommissioning/action/spent_fuel/unit3-e.html

 

[etudiant]

Very impressive performance by TEPCO. They are eating the elephant, one spoonful at a time, as laid out in their longer term plans..
Presumably a similar approach will be implemented later on units 1 and 2. Once that is done, the actual site fuel removal and cleanup can begin.

 

[Astronuc]

I posted about some open-access reports in the thread on Fukushima discussions.
https://www.physicsforums.com/threa...ear-disaster-discussions.501974/#post-6165013
However, there are two important technical books on the accident progression and report by AESJ. They are not open-access, but must be purchased, but are probably worth the money for serious technical analysis.

A Study of the Fukushima Daiichi Nuclear Accident Process
https://www.springer.com/us/book/9784431555421 e-book $89.00

The Fukushima Daiichi Nuclear Accident
Final Report of the AESJ Investigation Committee
https://www.springer.com/us/book/9784431551591 e-book $129.00

 

[LabratSR]

NHK Documentry - Decommissioning Fukushima Daiichi: Tackling Nuclear Fuel Debris

 

[turi]

Mainichi reports that reactor fuel removal work should start at unit 2 as it seems to be the easiest target: https://mainichi.jp/english/articles/20190809/p2a/00m/0na/005000c
Demolition work on the exhaust stack between units 1 and 2 has started:
https://mainichi.jp/english/articles/20190802/p2a/00m/0na/009000c

 

[LabratSR]

2019.10.31 The method for removing fuel from the Fukushima Daiichi Nuclear Power Station Unit 2 spent fuel pool

https://www4.tepco.co.jp/en/news/li...7LGmvM_5l8fBovBFGpGwMdruH6nq8RIILFmeEbhlXDHjs

 

[LabratSR]

A trip to the Fukushima No. 1 nuclear plant: Full-body suits and three layers of socks

https://www.japantimes.co.jp/news/2...tyRt0hfnU5RiquN9PBm7Tg6f4e6Xv20c#.Xk9B9UBFxHX

 

[LabratSR]

" Exceedingly high radiation levels found inside crippled reactor buildings at the Fukushima No. 1 nuclear plant were labeled by nuclear regulators as an “extremely serious” challenge to the shutdown process and overall decommissioning of the site."

Radiation levels at Fukushima plant far worse than was thought : The Asahi Shimbun

 

[gmax137]

Fukushima Daiichi 3 fuel removal completed : Waste & Recycling - World Nuclear News

Fukushima Daiichi 3 fuel removal completed
01 March 2021The process of removing all 566 fuel assemblies from the storage pool of unit 3 at the damaged Fukushima Daiichi nuclear power plant in Japan was completed yesterday, Tokyo Electric Power Company (Tepco) has announced. Fuel assemblies have already been removed from the pool at unit 4, but such work has yet to start at units 1 and 2.

https://www.world-nuclear-news.org/Articles/Fuel-removal-completed-at-Fukushima-Daiichi-3

 

[Sotan]

Hello again everyone.
Approaching 10 years since the accident there seems to be an increased interest in the situation of Fukushima Daiichi.
I am posting below the link to an article, originally in Japanese, translated with google - I think google translation from Japanese to English has improved considerably in recent times (I wonder if you agree). The article gives some opinions of experts regarding the (im)possibility of removing the fuel debris.
https://translate.google.com/translate?sl=ja&tl=en&u=https://news.infoseek.co.jp/topics/toyokeizai_20210308_414695/?l-id%3DTopMainTopic_busi-econ_1

 

[Charles Smalls]

Hello again everyone.
Approaching 10 years since the accident there seems to be an increased interest in the situation of Fukushima Daiichi.
I am posting below the link to an article, originally in Japanese, translated with google - I think google translation from Japanese to English has improved considerably in recent times (I wonder if you agree). The article gives some opinions of experts regarding the (im)possibility of removing the fuel debris.
https://translate.google.com/translate?sl=ja&tl=en&u=https://news.infoseek.co.jp/topics/toyokeizai_20210308_414695/?l-id%3DTopMainTopic_busi-econ_1

Good article and translation
Hard to believe it’s been an entire decade. Tepco recently posted a 53 minute long slide presentation on their website. It’s all in Japanese but from the images seems to chart their evolving picture of the melt out progression from the 3 cores and where data suggests the bulk of the exited fuel now lies in each unit: https://www4.tepco.co.jp/library/movie/detail-j.html?catid=107299&video_uuid=m88yqm90

Right before the end at 52:45 is the clearest display of the developing estimates for fuel pile locations. Notably all three updates still fall short of modelling fuel melt exit beyond the pedestal area and progress from there i.e. to beneath the suppression pool etc.

A comment on reddit by someone apparently working on the fuel sample/retrieval robot arm linked this video which shows progress on the arms construction: Will be interesting to see the scope of its ambitions

Hope everyone’s safe, see you next big news day or next year

 

[Sotan]

Another year has passed, but I am still following this subject - and maybe others do too.

- A few days ago they sent another underwater robot in the pedestal area of Reactor 1. You can see a video below. Apart from the lumps of "deposit" which are believed to be nuclear fuel debris, this time the images also show barren steel bars which originally were used to reinforce the concrete. It is speculated that the high temperature molten fuel that fell to the bottom of the reactor caused some of the surrounding concrete to "melt". (Does concrete "melt" ? Does it melt in such a way that the reinforcing steel bars remain? Rather then melting perhaps it is some different sort of chemical reaction that erodes it?) Now they worry that some of the molten fuels might not be located in the limited area right under the reaction vessel, but also spread to a certain degree in the surrounding areas too.

Youtube video

*Also a longer video with images from more robot cameras

 

[Rive]

(Does concrete "melt" ? Does it melt in such a way that the reinforcing steel bars remain? Rather then melting perhaps it is some different sort of chemical reaction that erodes it?)

Concrete can melt, but not this way, and when it really melts, the rebars going with it.
This one looks more like some extreme spalling.
The 'concrete' part loses integrity at few hundred degrees and dislocates from the (still solid at that temperature) rebars.
ref
ref2

 

[Astronuc]

some of the surrounding concrete to "melt". (Does concrete "melt" ? Does it melt in such a way that the reinforcing steel bars remain? Rather then melting perhaps it is some different sort of chemical reaction that erodes it?)

Concrete could melt: "The melting point of quartz sand is about 1,650 degrees Celsius while the melting point of cement is approximately 1,550 degrees Celsius."
Ref: https://bagofconcrete.com/what-is-the-melting-point-of-concrete/

The ceramic part of the fuel, UO₂, has a melting temperature of ~2800°C, but some fission products will melt at lower temperatures, or chemically react with water and other materials. The Zircaloy-2 cladding would have a melting temperature about 1850°C, but it would oxidize at much lower temperatures, which would be the reaction that produced hydrogen (Zr + 2 H₂O +> ZrO₂ + 2 H₂). The 'molten' fuel would have also reacted with cooling water, to higher order oxides and chlorides/bromides if seawater.

Stainless steel, or steels in general, melt at about 1375 to 1450°C depending on various factors such as composition, so steel rebar would melting before concrete.

Both carbon steel and stainless steel, and concrete, which is porous, would react chemically with seawater. One can go to a seashore and find examples of corroded steel and degraded concrete, although there are now special concretes and steels that resist corrosion from seawater.

 

[artis]

The 'concrete' part loses integrity at few hundred degrees and dislocates from the (still solid at that temperature) rebars.

I did see your references and I'm not disputing them, but overall I find this to be bit weird. Ordinary house fires with modern plastic and wood furniture etc items easily reach "few hundred degrees" and more at ceiling level.
One of the most common types of residential building around where I live is the 9 story reinforced concrete panel block apartments as well as monolithic concrete pour 16 and higher story buildings.
There is a flat fire regularly in one of them that goes on for an hour or more where red hot flames gush outside the windows. Yet I haven't seen any of those buildings be rendered structurally unsafe after such fire.
The ceiling is typically a reinforced prefabricated concrete panel and after such fires they are just cleaned and their use continues.
The place where I saw something resembling concrete cracking and falling off of the precast slabs was at Grenfell tower in the few videos that are online, but that tower burned for half a day and very thoroughly and yet not even to compromise the structural integrity to the point of collapse, as the tower is still standing.

So I myself am not that certain about exactly how much integrity different concrete mixes and implementations lose within an average few hundred degree fire.
Sadly I cannot find any relevant studies at the moment of the integrity if precast panels under fire for example.