Japan Earthquake: nuclear plants Fukushima part 2

[jim hardy]

We shouldn't expect that this wonderfully safe nuclear power can be safely kept from melting without electricity?
insert :Or some other means to get water to the core?

That's so on the present fleet. Station blackout is the one in plant guys' nightmares.

Suggestion from a 1992 "What If" study of severe accident sequences:
Portable tanks and pumps . ("Polybor" is borated water, for reactivity control in case the control rods melted away. )

http://naygn.org/wp-content/uploads/2013/09/NUREG_CR-5869-ORNL_TM-12080.pdf pdf page 94, document page 71

The bandwagon now is toward passive decay heat removal.

 

[jim hardy]

I expected them to be safe even if their electrical systems fail catastrophically... that having station electricity wires and switchboards busted up will NOT result in Cs-137 plume on the map, that nuclear power people know what to do in that case to prevent it.

Total loss of all power was not considered a credible result of any single event. That indeed proved mistaken.
Unit 2's diesel driven fire pump was flooded too. Scratch another layer of redundant means to pump water.
Unit 3's fire pump was unable to handle the high reactor pressure. Another one bites the dust..
...https://www.ncbi.nlm.nih.gov/books/NBK253938/

 

[nikkkom]

That's so on the present fleet. Station blackout is the one in plant guys' nightmares.

The thing is, before 2011, if someone would tell me that Western (or specifically Japanese) NPPs don't have plans what to do if they lose power permanently, I would flat out not believe such "nonsense". Nuclear power is safe as long as that stuff does not melt. Ergo, you must be extremely paranoid about not letting it melt. You must have plans how to prevent that even if the plant is shot to hell. Everything else (as in: "how much will it cost to return the plant to operational status again?") is secondary.

And I would have thought as an engineer, "why would it be THAT difficult anyway? RPV is just a giant steel bucket with water, right? If worst came to worst, depressurize it to 1 atm through some filters, keep it depressurized, and pump in any water. Even firefighter trucks would do". Yes, this is probably bad for future reactor's operation, but this would allow fuel to not melt, right?

2011 came as a huge shock to me. Not only this was not done, nothing like this was even *planned*. No plans at all existed what to do in this situation. TEPCO literally wrote in their disaster manuals that total loss of power is so improbable that they won't plan for this scenario. Emergency vent lines did not have filters.

 

[jim hardy]

The thing is, before 2011, if someone would tell me that Western (or specifically Japanese) NPPs don't have plans what to do if they lose power permanently,

I can tell you that in 2002, the year i retired, we were in my plant practicing loss of all power on our simulator. We were formulating plans and procedures for it. We knew just where to connect portable pumps and generators that were discreetly on hand.
My friends who still work there tell me there's now a huge new warehouse stocked with portable pumps, generators, and i have no idea what else. That's because of Fukushima.

There's an old country saying for when one feels humiliated: "Yeah, I closed that barn door all right but after the horse got out. "
As one who spent a lifetime in a plant how do you think i feel that this came out of my industry ? Was i a party to it ? Not knowingly.

And I would have thought as an engineer, "why would it be THAT difficult anyway? RPV is just a giant steel bucket with water, right? If worst came to worst, depressurize it to 1 atm through some filters, keep it depressurized, and pump in any water. Even firefighter trucks would do". Yes, this is probably bad for future reactor's operation, but this would allow fuel to not melt, right?

Yes.
We had a saying in my control room "It's only water - keep it that way." Your synopsis is accurate.
At its simplest the plant is just a heat transport mechanism from the reactor to a heatsink. Mr.Turbine is of course preferred sink for fission power but for decay heat the ultimate heatsink is cooling water from the ocean, via heat exchangers. For that you need the ability to pump water.
Operating procedures prescribe slow heatup and cooldown so as to not thermally overstress the reactor vessel and piping . So I can't fault the operators for not cooling and depressurizing fast, even though it was advised in that 1992 Nureg above. Operators know their procedures and are trained that they are inviolate.
I can fault the bureaucracy that didn't prepare the operators for loss of ability to pump water. And for loss of instrumentation.
Those poor plant guys were flying blind in uncharted territory. All alone.
Add to that the trauma of the tidal wave - only those who've seen a natural disaster or war can appreciate the psychological effect.
They had to be in shock.

So i don't make light of Fukushima.
Nor will i condemn the technology because of it.

Mythology is full of lessons about hubris. May we incorporate them into management science; and indeed into popular culture..
May Nuclear Power not become a House of Atreus.

My two cents and overpriced at that. I'll be quiet now.

old jim

 

[Astronuc]

2011 came as a huge shock to me. Not only this was not done, nothing like this was even *planned*. No plans at all existed what to do in this situation. TEPCO literally wrote in their disaster manuals that total loss of power is so improbable that they won't plan for this scenario. Emergency vent lines did not have filters.

I'd have to dig around, but I believe Fukushima Daiichi station had a plan. It seemed to be working, until the tsunami took out the fuel storage for the emergency diesel generators (EDGs), then flooded the EDGs and switchgear in the basements.

What they didn't plan for was a 15 m tsunami. They should have.

Elsewhere in the world, utilities' NPPs plan for loss of off-site power (LOOP) and station blackout (SBO). For example, IAEA-TECDOC-332 (1985), SAFETY ASPECTS OF STATION BLACKOUT AT NUCLEAR POWER PLANTS, provides some discussion and examples from plants that experienced LOOP and/or SBO. From IAEA - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/16/075/16075332.pdf

NPPs are required to have emergency plans, but those plans are only as the design bases established for each plant. I believe most plants have reasonable safety cases for flooding in their respective environments.

Even Fukushima Daini, which experienced extensive flooding in the same event, was able to control their reactors. The main difference was in the containment design, Mark II at Daini vs Mark I at Daiichi.

 

[etudiant]

I can tell you that in 2002, the year i retired, we were in my plant practicing loss of all power on our simulator. We were formulating plans and procedures for it. We knew just where to connect portable pumps and generators that were discreetly on hand.
My friends who still work there tell me there's now a huge new warehouse stocked with portable pumps, generators, and i have no idea what else. That's because of Fukushima. ...old jim

Very interesting, your plant was clearly taking its responsibilities seriously.
Did any of the regulators take note of your work or try to institutionalize it? It seems like a very good example of 'best practices' for a plant.
If there had been some contingency planning for such 'beyond design basis' events, perhaps the market for nuclear power would be healthier today.

 

[jim hardy]

Did any of the regulators take note of your work or try to institutionalize it? It seems like a very good example of 'best practices' for a plant.

I'm sure they noticed. By that time we had resident inspectors, a result of TMI.

But there's a strict boundary at design basis - it's all you can be required to do.

Politics gets in the way of good judgement.
As astro points out,

NPPs are required to have emergency plans, but those plans are only as the design bases established for each plant.

Anti-nukes would love to impose beyond design basis requirements on utilities to financially break the industry.
Pro-nukes and the industry are understandably resentful of such efforts and circumspect to the extreme.
The poor regulators are caught in the middle of those two vociferous and well funded opposing forces .

I guess a wise diplomat would say of long term station blackout "That's beyond design basis" then quietly go to work on what to do about it. I don't know whether TEPCO was doing that. We were in the early stages when i retired.
It could be that regulators were quietly encouraging it from higher up the organization , i honestly don't know. But it would make sense.

oops - i said i'd be quiet. But that's the best answer i can give to your question.

.
old jim

 

[etudiant]

I'm sure they noticed. By that time we had resident inspectors, a result of TMI.

But there's a strict boundary at design basis - it's all you can be required to do.

Politics gets in the way of good judgement.
As astro points out,

Anti-nukes would love to impose beyond design basis requirements on utilities to financially break the industry.
Pro-nukes and the industry are understandably resentful of such efforts and circumspect to the extreme.
The poor regulators are caught in the middle of those two vociferous and well funded opposing forces .

I guess a wise diplomat would say of long term station blackout "That's beyond design basis" then quietly go to work on what to do about it. I don't know whether TEPCO was doing that. We were in the early stages when i retired.
It could be that regulators were quietly encouraging it from higher up the organization , i honestly don't know. But it would make sense.

oops - i said i'd be quiet. But that's the best answer i can give to your question.

.
old jim

It seems to me that represents willful blindness on part of both the regulators as well as the industry, which hurt everyone in the end.
Regulators can certainly highlight 'best practices' in their numerous reports and summaries, as well as reward them with more friendly treatment. Academia is likewise always eager to find real world examples for its studies and there are plenty of industry conclaves where the professionals can exchange ideas privately.
That could have allowed for efficiently improving the safety of the entire reactor fleet.
Afaik, the Japanese nuclear industry used the US as a role model. It is too bad that they were not introduced to that kind of 'beyond design basis' thinking.
The fear helping the 'anti nuke' forces arguably has done more to damage the industry than those 'anti nukes' ever could.

 

[jim hardy]

That's a very logical post , etudiant.

Compare academia to the tabloid culture where anti-nukes operate .
Can you imagine the headlines ? "Plant X is planning for failure of its safety systems and a meltdown, we're all going to die."
"China Syndrome" was a pretty darn good movie IMHO. Captured the personalities well. Contrast it with "Prometheus Crisis" which thankfully was never finished...

The S A Hodge study i linked, NUREG 5869 at http://naygn.org/wp-content/uploads/2013/09/NUREG_CR-5869-ORNL_TM-12080.pdf
and others eg http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/23/031/23031859.pdf

indicate to me there was for some years ongoing sober discussion at levels far above mine. Remember, Homer Simpson was several levels higher in the organization than me.

So yes, one could lay a lot of the blame at the feet of our hysterical segment of the media
This will sound like a digression but it's about playing to the psychology of mobs --- ever read Lincoln's Lyceum Address ?

Reason, cold, calculating, unimpassioned reason, must furnish all the materials for our future support and defence.

EDIT added link to Lincoln :
http://www.abrahamlincolnonline.org/lincoln/speeches/lyceum.htmold jim .

 

[Hiddencamper]

I'd have to dig around, but I believe Fukushima Daiichi station had a plan. It seemed to be working, until the tsunami took out the fuel storage for the emergency diesel generators (EDGs), then flooded the EDGs and switchgear in the basements.

What they didn't plan for was a 15 m tsunami. They should have.

Elsewhere in the world, utilities' NPPs plan for loss of off-site power (LOOP) and station blackout (SBO). For example, IAEA-TECDOC-332 (1985), SAFETY ASPECTS OF STATION BLACKOUT AT NUCLEAR POWER PLANTS, provides some discussion and examples from plants that experienced LOOP and/or SBO. From IAEA - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/16/075/16075332.pdf

NPPs are required to have emergency plans, but those plans are only as the design bases established for each plant. I believe most plants have reasonable safety cases for flooding in their respective environments.

Even Fukushima Daini, which experienced extensive flooding in the same event, was able to control their reactors. The main difference was in the containment design, Mark II at Daini vs Mark I at Daiichi.

Im not sure if the mark II was the whole reason for the difference. Daini didn't lose D.C. Power so they had indications and RCIC control power. Daiichi lost their IC at unit 1, was blind in unit 1 and 2, and after core damage at unit 1 it really cascaded.

 

[gmax137]

It seems to me that represents willful blindness on part of both the regulators as well as the industry...

I'm not sure what part of Jim's post you mean. Is it this:

But there's a strict boundary at design basis - it's all you can be required to do.

Or, do you mean not discussing best practices?

 

[etudiant]

I'm not sure what part of Jim's post you mean. Is it this:
Or, do you mean not discussing best practices?

I was referring to the overall mindset that Jim identified, not setting out and highlighting real system improvements for fear that going beyond design basis would open the floodgates for ever more extreme requirements. The US industry was the world leader, yet feared to lead. Fear is a bad guide tor the future, in business as well as in technology.

 

[etudiant]

That's a very logical post , etudiant.

So yes, one could lay a lot of the blame at the feet of our hysterical segment of the media
This will sound like a digression but it's about playing to the psychology of mobs --- ever read Lincoln's Lyceum Address ?

EDIT added link to Lincoln :
http://www.abrahamlincolnonline.org/lincoln/speeches/lyceum.htmold jim .

Thank you for the link to the Lincoln speech, I wish it were required reading for high school everywhere.

I agree that the fear of the media has often swayed sober judgment, but think that reflects leadership failure.
The reason management is paid more highly is precisely to first make sound decisions and then to defend them externally. It is not a good sign when both the management as well as the regulators prioritize lack of scrutiny over good policy.

 

[jim hardy]

I agree that the fear of the media has often swayed sober judgment, but think that reflects leadership failure.

You don't think there's an at least equal failure of leadership in today's media ?

 

[gmax137]

I was referring to the overall mindset that Jim identified, not setting out and highlighting real system improvements for fear that going beyond design basis would open the floodgates for ever more extreme requirements. The US industry was the world leader, yet feared to lead. Fear is a bad guide tor the future, in business as well as in technology.

OK. But, the "design basis" is not just an idea; taken in totality, the "design basis" is a well thought out and consistent approach to regulation. Take a look at General Design Criterion 2

Criterion 2—Design bases for protection against natural phenomena. Structures, systems, and components important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, floods, tsunami, and seiches without loss of capability to perform their safety functions. The design bases for these structures, systems, and components shall reflect: (1) Appropriate consideration of the most severe of the natural phenomena that have been historically reported for the site and surrounding area, with sufficient margin for the limited accuracy, quantity, and period of time in which the historical data have been accumulated, (2) appropriate combinations of the effects of normal and accident conditions with the effects of the natural phenomena and (3) the importance of the safety functions to be performed.

This says you must design equipment to survive and perform its function after the worst ... tsunami... that could occur at the site. If you comply with GDC 2, there's no reason to even look at a "beyond design basis" tsunami. Now, if you incorrectly identify the DB tsunami, you will be in trouble. But that doesn't mean we should be regulating to beyond DB; it means we should be enforcing the design basis requirements and the GDCs.

Flooding is tricky because once the DB flood level is established, it is very difficult/expensive to revise it upwards. You can't very well raise the plant 10 feet, and massive walls are expensive. Plus, if your flood protection is ever overtopped, you see a real "cliff edge" in the consequences. A flood that rises to one inch below the top of the wall is fine, but one inch over the wall and the story is completely different. All this means is, when establishing the design level (before plant construction) you better get it right.

 

[jim hardy]

Thanks gmax

that's the crux of what happened at Fukushima .
Design basis failed to include those thousand year ago records of tidal waves on Pacific side of the island.
It's my understanding they were unearthed only about 1990.

Now that's pretty grave news to a design organization, that you've missed a GDC . Flawed PRA's pale in comparison

As you said it's difficult to revise a design basis upward. It's agreed to at licensing time by engineers of both sides, utility and regulators. They could bicker for years before changing it.
Hence my position somebody needed to go around the bureaucracy.old jim

 

[etudiant]

You don't think there's an at least equal failure of leadership in today's media ?

Absolutely agree that the media are derelict in their performance, but we pay management to manage intelligently, even if that is not well received by the media.
The buck stops there, not in the studios.

Thinking carefully on an ongoing basis about options for when things go badly astray and implementing precautionary preparations such as you outlined, even if they are outside the Design Basis, seems to me normal good engineering practice. Not doing so and trusting to a Design Basis that may not reflect current knowledge clearly describes the Fukushima situation.

 

[jim hardy]

Thinking carefully on an ongoing basis about options for when things go badly astray and implementing precautionary preparations such as you outlined, even if they are outside the Design Basis, seems to me normal good engineering practice.

It does make a lot of sense, doesn't it? Especially when you live nearby.

Not doing so and trusting to a Design Basis that may not reflect current knowledge clearly describes the Fukushima situation.

It does look like that from afar.
I don't know what things they tried . I do remember thinking "They'll put down the procedures and find some way to get water in there ."
But with the basements flooded and lights going out, working in respirators by flashlight, i can see how they might have been just overwhelmed.

I was referring to the overall mindset that Jim identified, not setting out and highlighting real system improvements for fear that going beyond design basis would open the floodgates for ever more extreme requirements.

Fear of those 'floodgates' is an issue. (Look under hood of a modern automobile). That's a social matter not a scientific one.

Highlighting ? No, no, no - there's some things you just do without fanfare. Same spirit as checking the hoses and fluids in your kid's car.
You encourage your peers at "industry conclaves" to do the same thing, and exchange ideas with them.

Of course post Fukushima it's industry wide policy .

old jim

 

[HowlerMonkey]

I'm curious how they were able to measure the strength of an earthquake 900 years ago.

 

[Astronuc]

Thinking carefully on an ongoing basis about options for when things go badly astray and implementing precautionary preparations such as you outlined, even if they are outside the Design Basis, seems to me normal good engineering practice. Not doing so and trusting to a Design Basis that may not reflect current knowledge clearly describes the Fukushima situation.

The industry does periodic assessments of Design Bases, especially after major events such as happened at Fukushima Daiichi. After TMI, considerable research was done an safety analysis methods. After Chernobyl, considerable research was done on assuring containment. The EU sponsored the shutting down of RBMK and VVER-440 units in E. Europe.

Here is one perspective on nuclear safety - Safety of Nuclear Power Reactors
http://www.world-nuclear.org/inform...-plants/safety-of-nuclear-power-reactors.aspx

However, the modest rate does not offset the impact on those in the vicinity of these accidents.

Following Chernobyl, International Nuclear Safety Advisory Group at the IAEA produced various reports on nuclear safety including the following report.

INSAG-8, A COMMON BASIS FOR JUDGING THE SAFETY OF NUCLEAR POWER PLANTS BUILT TO EARLIER STANDARDS, INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1995

http://www-pub.iaea.org/MTCD/publications/PDF/Pub991e_web.pdf

1. INTRODUCTION

Safety requirements for nuclear power plants have not always been set consistently between plants and between countries. Although safety records and reliability data show that the majority of nuclear plants around the world are producing power safely and reliably, this claim cannot be made of all nuclear plants. For many reasons, including deficient design, inappropriate feedback of operating experience, ageing processes that have not been managed and absence of a programme of safety reassessment coupled with lack of appropriate safety assessment and verification by the regulatory authority, there are plants operating today with levels of safety that are inadequate in comparison with those of the majority of operating plants. This has led to a need for a common basis for judging whether the level of safety of a plant is acceptable.

2. HISTORICAL BACKGROUND

Concern about the need for a common basis for judging the safety of nuclear power plants came into sharp focus in die late 1980s and early 1990s as awareness grew of the inadequate levels of safety at some plants. In some cases the concerns focused on particular designs that safety experts were increasingly judging to be inadequate by current safety standards. In other cases, the concerns were focused less on a particular design and more on deficiencies in safety, such as poor operations, a weak safety culture or a weak national infrastructure for supporting safe operation of a plant. Also of concern was the recognition that some site related external events had not been adequately taken into consideration in plant design or in procedures at the plant.

These concerns were extensively discussed at the IAEA Conference on The Safety of Nuclear Power: Strategy for the Future, held in Vienna, 2-6 September 1991.

5. RESPONSIBILITIES:

The ultimate responsibility for the safety of a nuclear power plant rests with the operating organization. This responsibility is in no way diminished by the separate activities and responsibilities of designers, suppliers, constructors and regulators. The operating organization is responsible for all aspects of operation, maintenance, training, documentation and related activities. If deficiencies in design, construction or operation are identified, the operating organization should take appropriate corrective action.The current situation in the US after Fukushima can be found here.
https://www.nrc.gov/reactors/operating/ops-experience/japan-dashboard/emergency-procedures.html
https://www.nrc.gov/reactors/operating/ops-experience/japan-dashboard.html

http://www.world-nuclear.org/inform...ety-of-plants/three-mile-island-accident.aspx
The operators were unable to diagnose or respond properly to the unplanned automatic shutdown of the reactor. Deficient control room instrumentation and inadequate emergency response training proved to be root causes of the accident.

In addition to the US NRC, the federal regulator, the industry has INPO, Institute of Nuclear Power Operations, which was formed in 1979 in response to TMI.
http://www.inpo.info/AboutUs.htm

Evaluations
INPO evaluation teams travel to nuclear electric generating facilities to observe operations, analyze processes, observe plant activities, and ask a lot of questions.

With an intense focus on safety and reliability, our evaluation teams assess the following:

• knowledge and performance of plant personnel
• condition of systems and equipment
• quality of programs and procedures
• effectiveness of plant management

Additionally, INPO conducts corporate evaluations that are also focused on safety and reliability.

INPO can issue findings that can impact the corporate insurance rates, so utilities have a strong incentive to get it right.

 

[Astronuc]

I'm curious how they were able to measure the strength of an earthquake 900 years ago.

They couldn't do the kinds of measurements we do now or during the past several decades. All one could do is measure the damage to structures, or record changes to the landscape.

To estimate the strength or energy in previous earthquakes requires forensic science, and yet that only gets an estimate.

 

[jim hardy]

All one could do is measure the damage to structures, or record changes to the landscape.

And, the folks back then left high water markers.
http://www.nytimes.com/2011/04/21/world/asia/21stones.html

 

[turi]

The cover for the spent fuel removal at unit 3 has arrived:

 

[turi]

Mainichi says core fuel will be removed without filling the containments with water: http://mainichi.jp/english/articles/20170705/p2a/00m/0na/008000c

 

[turi]

A bit contrary to what Mainichi reported, IRID reports about full scale tests to stop leakages in the primary containment vessels and suppression chambers: http://irid.or.jp/en/topics/原子炉格納容器漏えい箇所の補修技術の実規模試-2/

EDIT: IRID also reports about simulations and simulation verification regarding the criticality state of molten and partially molten fuel: http://irid.or.jp/en/topics/燃料デブリ臨界管理技術の開発／京都大学臨界集/

 

[turi]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images2/handouts_170713_02-j.pdf
As far as I understand the new handout from TEPCO they will shut down SFP 1 cooling to test whether natural cooling would now be sufficient. They did that successfully in April but want to test it with summer temperatures as well.

 

[turi]

Tepco will soon start a new survey of the unit 3 PCV: http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images2/handouts_170713_09-j.pdf
I didn't get all the details from the Japanese version.
Edit: An English version is now available: http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2017/images/handouts_170713_02-e.pdf

 

[etudiant]

Reports indicate TEPCO will dump the roughly 800,000 tons of treated cooling water despite the much higher than allowed tritium content.
http://www.japantimes.co.jp/news/20...xic-tritium-sea-fishermen-irate/#.WWp52oTqKbg
This decision is unsurprisingly not well received by the local community.
I cannot understand why TEPCO, in this time of ultra cheap large tanker availability, does not simply buy a few old tankers and use them to store the tritium contaminated water in some quiet harbor for the next few decades. That would allow the tritium to decay and also ease the concerns of the local community, at minimal expense.

 

[turi]

Reports indicate TEPCO will dump the roughly 800,000 tons of treated cooling water despite the much higher than allowed tritium content.

I've read the same but wasn't able to dig up a good source on the activity of the water. I remember something along 100 Bq per cubic meter, but don't know where I that information came from.
Edit: This article puts the whole Tritium inventory in the Fukushima waste water tanks at 3.4 PBq:
https://www.theguardian.com/environment/2016/apr/13/is-it-safe-to-dump-fukushima-waste-into-the-sea

 

[etudiant]

Well, 100 Bq/cubic meter would only be 80 million Bq for the total 800,000 cubic meter inventory, so there is a considerable misunderstanding.
I'm very skeptical of the 100 Bq/cubic meter number, it may more plausibly be per cubic centimeter or per liter.
I do know parts of the Baltic Sea had cesium levels of well above 1000 Bq/cubic meter in consequence of Chernobyl .
My guess is that we have 3.4 PBq in 800,000 cubic meters of water, so about 4x10**6 Bq/cubic meter in the Fukushima waste cooling water.
That is material enough to understand the concerns of the local community.

Maybe TEPCO should contract for some large barges from China, as a gesture of international amity.
They would get them at a good price, then fill them with this water and leave them parked in the ample space available at low rates off the former USSR Kamchatka nuclear submarine base. Everybody would be pleased, the locals, the Japanese government bodies, the Chinese and the Russians. Why don't they do it?

 

[Rive]

Well, 100 Bq/cubic meter would only be 80 million Bq for the total 800,000 cubic meter inventory, so there is a considerable misunderstanding.
I'm very skeptical of the 100 Bq/cubic meter number, it may more plausibly be per cubic centimeter or per liter.
I do know parts of the Baltic Sea had cesium levels of well above 1000 Bq/cubic meter in consequence of Chernobyl .
My guess is that we have 3.4 PBq in 800,000 cubic meters of water, so about 4x10**6 Bq/cubic meter in the Fukushima waste cooling water.

According to Wiki the limit for tritium in drinking water is 740Bq/l in USA and above 70kBq/l in Australia.
There is enough water available locally that it could be diluted below any limit.
Given its short half-life I think it is exactly the case when any 'solutions' what would keep it in concentrated form are far more dangerous than to dump it to the ocean.

 

[Gary7]

According to this article, the activity of tritium in the Fukushima water is less than 60k becquerels per liter.
http://www.labornetjp.org/EventItem/1499136119185matuzawa

 

[etudiant]

Thank you, Gary7 and Rive, for this helpful added information.
I don't have any local sources, but just think that from an outside observer perspective, TEPCO is insane to peeve the locals.
This cleanup will cost between $100 billion and a trillion, so the hiring costs for some ships or hulls to make the problem go away is immaterial.
TEPCO seems not to understand that they reduce the prospects of ever getting their prized Kashiwazaki complex restarted if they dump on the local community.

 

[Sotan]

Investigation of PCV of Unit 3 - Quick report, photos and movie from Tepco/IRID/Toshiba
http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images2/handouts_170719_08-j.pdf
http://photo.tepco.co.jp/date/2017/201707-j/170719-01j.html

Some damage was found in structures inside the pedestal. A few pieces of material from CRD housings were seen fallen inside the pedestal. It was not possible to assess the state of the grating above. When the robot approached structures under water a certain murkiness appeared as deposits were stirred. The images taken today will be used to decide on the second phase of the investigation, scheduled for 7/21.

 

[Charles Smalls]

Very interesting findings with more to hopefully follow.

To quote the article:

" The robot discovered that a grate platform that is supposed to be below the reactor core was missing and apparently was knocked down by melted fuel and other materials that fell from above, and that parts of a safety system called a control rod drive were also missing [...]
Kimoto said the robot showed that the Unit 3 reactor chamber was "clearly more severely damaged" than Unit 2, which was explored by the scorpion probe."

This quote and these images further reinforce my original opinion that muon scanning the RV bottom head and above for the past few months was "pointless". Images from Unit 2's CRD/pedestal area and Unit 1's PCV floor already suggested gross bottom head failures and or fuel melt outs had occurred in each reactor. To operate on a belief that Unit 3 which suffered similar cooling issues combined with much more violent explosions would be in a better condition than its sister units was very silly.

I hope that either the Unit 3 muon scanners were installed without risk of exposure to the engineers or that the publicised diagrams are misleading in that the muon scanners have a larger fov than we see depicted. If it can capture images along the pedestal area and lower, it may detect something useful. Very interested to see what the probe will pick up over the next few days.