Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[etudiant]

TEPCO...what a bunch of techno spew..
Why ..oh...why I wonder does..it look like this?

The reactors are still generating close to a megawatt each of decay heat.
That heat has to go somewhere. Some of it boils water, probably because the cooling flow is pretty uneven inside the reactors. That gives steam, which still carries a noticeable amount of contamination.
However, compared to a year ago, the emissions now are minuscule. The damage is done, it just will be a very long cleanup.

 

[mloub]

I was wondering if anyone here had any thoughts/special insights on the water situation at the plant.

As I understand it, currently TEPCO is decontaminating the water they are using for cyclic cooling for Cesium only. There is apparently a multi-nuclide decontamination system in the works that will remove 40 or more nuclides, and potentially allow the decontaminated water to be even more safely discharged into the ocean. (Whether they get public understanding or approval to do this is another matter).

I also understand that about 300-500 tonnes of water leaks into the damaged reactor basements per week from groundwater run-off, and that TEPCO has stated the flow rates of groundwater into the basements depends on how quickly they pump water out of the basements, which is why they have decided to keep water levels in the basements at around 3,000 OP.

If you track TEPCO's stored water reports, you notice that the water levels in the basements have changed little, while the decontaminated water volumes continue to climb. Suggesting TEPCO is decontaminating just enough water to cool the plants and remove the groundwater run-off, but not actually trying to drain the basements.

But what is the ultimate end game? For starters, why decontaminate the water at all before using it cool the plant. Wouldn't it be simpler to pump the contaminated water in a shorter cycle into the reactors for cooling? Decontaminated water could then be stored separately for eventual discharge without pumping it back through the plant and contaminating again.

What am I failing to see here?

M.

 

[etudiant]

I was wondering if anyone here had any thoughts/special insights on the water situation at the plant.

But what is the ultimate end game? For starters, why decontaminate the water at all before using it cool the plant. Wouldn't it be simpler to pump the contaminated water in a shorter cycle into the reactors for cooling? Decontaminated water could then be stored separately for eventual discharge without pumping it back through the plant and contaminating again.

What am I failing to see here?

M.

Presumably TEPCO is trying to reduce the ambient radioactivity levels in anticipation of future clean up efforts.
I've seen some claims that the water in the plant now is at a millionth of the initial contamination level, but no official data, even though that would be very helpful.
Perhaps some of the more savvy members of this forum could give guidance.

 

[SteveElbows]

Regarding data on water before and after decontamination, you mean this sort of thing? http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120229_01-e.pdf

 

[etudiant]

Regarding data on water before and after decontamination, you mean this sort of thing? http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120229_01-e.pdf

Thank you, SteveElbows.
That is exactly the kind of info that would help, if it is available for prior dates as well, ideally at least monthly since the accident.

 

[rmattila]

There's one plot I've been trying to update whenever new information is provided:

https://www.physicsforums.com/showpost.php?p=3698440&postcount=12092

 

[tsutsuji]

But what is the ultimate end game? For starters, why decontaminate the water at all before using it cool the plant. Wouldn't it be simpler to pump the contaminated water in a shorter cycle into the reactors for cooling? Decontaminated water could then be stored separately for eventual discharge without pumping it back through the plant and contaminating again.

What am I failing to see here?

M.

Your question is pretty similar to the one I asked on 16 December :

Why do they need that big Areva/Kurion/Sarry water purification facility in the first place ? I understand that they need to remove salt because salt and steel do not get on very well with each other. But why remove cesium ?

What I was missing was that pouring radioactive water into the reactors would create other clouds of radioactive steam over the plant and over Japan. So it is better to pour clean water. See Astronuc and Rmattila's answers at https://www.physicsforums.com/showthread.php?p=3671515&highlight=line#post3671515

And about how to prevent ground water from flowing in :

Pretty much the only way to do that is to have wells outside of the containment that draw out the ground water.

I think this is what Tepco is trying to do, as reported in the last monthly mid-long term meeting :

http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/m120227_05-j.pdf
* Page 37/94 to 46/94 : subdrain decontamination tests

Ahead of the restart of the subdrain system, it is necessary do decontaminate the water inside the subdrain pits, so we are performing the "decontamination tests" and the "water drawing up tests".

http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/m120227_05-j.pdf page 39/94 (my translation)

 

[HowlerMonkey]

Why remove cesium?

It could have something to do with the plant being on the shore of a salt water body that could very well transport dissolved salts worldwide.

 

[tsutsuji]

http://www.yomiuri.co.jp/science/news/20120303-OYT1T00609.htm Another unit 2 thermometer is having abnormal values and is removed from the list of thermometers used for reactor surveillance.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120303_03-e.pdf Top of junction of skirt supporting RPV（270°） （TE-2-3-69F3）resistance rose to 1.76 times the September value.

 

[duccio]

The reactors are still generating close to a megawatt each of decay heat.

Are you sure about the 1MW? They're keeping the reactors cool with 6 or 9 t/hour of water, I don't believe that would be enough if the core was still emitting that much energy...

 

[etudiant]

The data comes from this TEPCO report:
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1330575712P.pdf

Reactor 1 still emits 0.6 megawatts, reactors 2 and 3 0.9 megawatts.
It is likely that the reactors are still boiling some water, steam is visible in the videos sometime and TEPCO indicates site emissions are still around 10 million bequerels.

 

[etudiant]

There's one plot I've been trying to update whenever new information is provided:

https://www.physicsforums.com/showpost.php?p=3698440&postcount=12092

Thank you rmattila for a most informative document.
The activity declines, less than a factor of 10 at best, are much more modest than I had believed. However, they are more consistent with the reality that TEPCO has treated about 200,000 tons of water to date, 3x the volume in the plant, on a trickle in/trickle out basis.

 

[wizwom]

Are you sure about the 1MW? They're keeping the reactors cool with 6 or 9 t/hour of water, I don't believe that would be enough if the core was still emitting that much energy...

Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

But even 0.6 MW is WAY too high for purely decay product radiation. Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown. The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.

 

[CaptD]

Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

But even 0.6 MW is WAY too high for purely decay product radiation. Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown. The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.

I agree with your reasoning; there is "much" more going on below reactors 1-3
... than anyone would describe as acceptable in a "cold shutdown"...

 

[zapperzero]

Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown.

We would? Care to share your calculation?

 

[etudiant]

Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

But even 0.6 MW is WAY too high for purely decay product radiation. Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown. The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.

Not sure that is correct.
According to Wikipedia here: https://en.wikipedia.org/wiki/Decay_heat
spent fuel has a decay heat of about 10 kW/ton after one year.
The indicated values would be about in line with the reactor fuel loadings.

 

[CaptD]

Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

But even 0.6 MW is WAY too high for purely decay product radiation. Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown. The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.

I agree with your reasoning; there is "much" more going on below reactors 1-3
... than anyone would describe as acceptable in a "cold shutdown"...

 

[Rive]

The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.

Nope. That almost MW scale heat production comes from decay, not fission. There is no sign of ongoing chain reaction in any of the damaged reactors and without chain reaction the heat from spontaneous fissions in nuclear fuel is practically negligible.

 

[rmattila]

My sketches from spring ( https://www.physicsforums.com/showpost.php?p=3283216&postcount=5788 ) give around 400 - 600 kW, so it seems we're on the same map.

 

[tsutsuji]

Continuation of the translation started on https://www.physicsforums.com/showpost.php?p=3795578&postcount=12465

1 March report http://www.tepco.co.jp/cc/press/betu12_j/images/120302a.pdf attachments 7-1 and 7-2 p. 40/91-41/91 :

Attachment 7-1 Jet pump instrumentation work: implementation plan and problems (work preparation)

1. Work flow

①decontamination⇒②bring machinery and materials, prepare the area (temporary lighting, etc.)⇒③remove obstacles ⇒④installation of working floor (temporary scaffolding)⇒⑤bring in and install shielding material (in the vicinity of the penetration)⇒⑥final clean up

2. Problems (constraints as regards application methods and feasibility) and solutions

①decontamination

Constraints as regards application methods and feasibility
* radiation decrease obtained from decontamination
* radiations in penetration parts are unknown
* decontamination domain/method are undecided
* If the PCV outer wall is to be decontaminated, the installation of a working floor is necessary

Solutions
* radiation measurements. perform assessment before starting the work.
* perform radiation measurements in penetration parts
* study decontamination domain/method. Develop equipments.
* before starting work, perform onsite inspection for the installation of working floor

②bring machinery and materials, prepare the area (temporary lighting, etc.)

Constraints as regards application methods and feasibility
* need of detailed estimate of quantities of each material and machinery needed for the work
* need to study methods to lift machinery and materials up to the penetration level.
* ensure that obstacles are absent on the transportation route

Solutions
* detailed listing and study of quantities of each material and machinery needed for the work
* perform onsite survey
* perform onsite survey as regards transportation route. Also, adjust interferences with the working spaces of other works

③remove obstacles
Constraints as regards application methods and feasibility
* the presence of obstacles, interfering objects is unknown

Solutions
* perform onsite survey

④installation of working floor (temporary scaffolding)

Constraints as regards application methods and feasibility
* need to study if we decide to use a scaffolding or a lifter
* the working floor must secure a 2 m x 2 m area

Solutions
* study after performing onsite survey
* perform onsite survey and check the presence of obstacles.

⑤bring in and install shielding material (in the vicinity of the penetration)

Constraints as regards application methods and feasibility
* in function of the radiation around the penetration, shield installation can be necessary
* we plan to perform the time consuming thermometer insertion work in a shielded area installed on the floor level

Solutions
* planning of shielding after onsite survey and radiation measurements
* onsite survey of the floor. Study of the shield's location and shape.

⑥final clean up

Constraints as regards application methods and feasibility
* the piping work and the insertion work's clean-up materials and machinery, and the final situation are unknown

Solutions
* list up the the piping work and the insertion work's clean-up materials and machinery and check the final situation

Attachment 7-2 Jet pump instrumentation work: implementation plan and problems (piping work)

1. Work flow

①check onsite working area (presence or absence of obstacles, etc.)⇒②preparation work (temporary electric power source, covering, etc.)⇒③fill water into the pipe (near the PCV penetration)(fill water from the instrumentation line, etc.)⇒④install the tool needed for pipe freezing and fill dry ice (or liquid nitrogen) into the tool⇒⑤check that the pipe is frozen⇒⑥install pipe cutting tool(omitted if cutting by hand is possible)⇒⑦pipe cutting⇒⑧globe valve body removal {case of alternative plan}⇒⑨machining of groove⇒⑩pipe welding (to attach stop valve)⇒⑪additional piping installation and pipe binding

2. Problems (constraints as regards application methods and feasibility) and solutions

Common problems and solutions for ③⇒④⇒⑤⇒⑥⇒⑦⇒⑧⇒⑨⇒⑩⇒⑪

[Problems of the pipe freezing and cutting method]

Method by filling water between the stop valve and the PCV penetration end plate, freezing the pipe to obstruct it, and cutting the pipe right before the valve.

1) Since the distance between the PCV penetration end plate and the stop valve is short (expected to be 300 mm or less), it is thought that stoppage by freezing the pipe is difficult.
2) As mentioned above, it is thought that creating enough space to cut the pipe between the PCV penetration end plate and the pipe [?] is difficult.
3) Even if stoppage by freezing is achieved, the frozen plug is formed in the short space of the straight part of the pipe, and there is a risk that the frozen plug gets removed. (in the normal pipe freezing method, the ice plug is formed in a discontinuous part such as an elbow, so that it does not get removed)
4) When freezing is performed, it is necessary to build a temporary box where dry ice, alcohol, etc. is injected, but as this interferes with other instrumentation lines, it is thought that such a construction is difficult.
5) It is necessary to secure a method to confirm freezing.
6) It is necessary to maintain freezing under high radiations.

[Solutions to the problems of the pipe freezing and cutting method]

1), 3), 5) The freezing method is confirmed by a mock-up test.
2) As mentioned below, an alternative plan is studied where the pipe is cut downstream the valve
4) Study of the pipe freezing tool where dry ice or alcohol is injected
6) Study of a method to maintain freezing and to survey freezing during the work. Study of freezing substance replenishment method.

[Problems of the alternative method]

Method: the frozen area is extended to the valve entrance, and the pipe is cut downstream the valve. After cutting downstream the valve, a tool is inserted through the cut opening. Then the valve body, etc. is removed as it would be an obstacle when the thermometer is inserted.

1) It is necessary to study and develop a valve body removal device.

[Solutions to the problems of the alternative method]

1) The valve body removal tool is checked with a mock-up test.

[Other problems]

1) The working location is in high elevation (about 5 m) and high radiation. If the radiation is not lowered, the workers can merely go to the working location and cannot work. Also, remote surveillance, remote controlled operations and shielding, etc. must be studied.
2) In order to measure the dimensions regarding the distance between the PCV penetration end plate and the stop valve, an onsite check must be done.
3) As the working location is a narrow space, it is possible that obstacles interfere.
4) As it is necessary to fill water into the pipe before freezing, it is necessary to study the water filling method and the way to confirm water seal.
5) As the working environment is with high radiations, as an access to an elevated place must be provided, and as the method is not certain, it is not possible to estimate how many workers are needed.

[Solutions to the other problems]

1) before the work in the high radiation area, workers perform training drills, and the work must be done after the working efficiency has been improved.
2) before the work, an onsite survey is performed to measure the dimensions.
3) before the work, an onsite survey is performed to check the presence of obstacles, and countermeasures are studied.
4) the water filling method is studied after inspecting the injection line for example on the side of the instrumentation rack
5) after performing mock-up tests and taking the final decision about the working method, an evaluation of which workers are needed is performed.

 

[duccio]

Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

Maybe I'm getting it completely wrong, but 500 Joules/gr should be around 120 calories... or +120 degrees C. At atmospheric pressure, water would evaporate well before taking away all the heat. Besides, if water would evaporate at such high rate, where does the water accumulating in the basement come from?

 

[etudiant]

Maybe I'm getting it completely wrong, but 500 Joules/gr should be around 120 calories... or +120 degrees C. At atmospheric pressure, water would evaporate well before taking away all the heat. Besides, if water would evaporate at such high rate, where does the water accumulating in the basement come from?

Apparently TEPCO estimates inflows from ground water through the cracked walls of the plant at around 500 tons/day. To stop that, TEPCO would need to build a barrier all around the plant, a non trivial task given continuing aftershocks in the area. Moreover, inflows are a lot less problematical than outflows which could contaminate the groundwater.

Re the decay heat absorption by the water injection, it seems plausible that the heat is boiling some of the water, as the fuel is probably concentrated in some piles that are getting sprinkled, rather than held in rods bathed in coolant.

 

[Rive]

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120302_05-e.pdf

My question is: will they continue to operate the radioactive filtering, or they will just switch to the desalinating facility?

As I understand, damaged spent fuel under water releases the fission products continuously: so if they cease filtering for radioactive materials then the radioactivity of the water in the pool will start increase again (if the pool contains damaged fuel: I think it likely does in case of U3 and U1).

For the SFP of U1 they had stopped the filtering for radioactive materials. Do we know anything about the concentrations afterward?

Ps.: about the decay heat of the cores: maybe we can put together a rough estimation about the 'power' already removed from the cores by the cooling water. How much is the heat production of an used, 'spent' filtering tower used for the decontamination of water from the basements? How many towers were used up till now? Any information, anybody?

 

[zapperzero]

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120302_05-e.pdf

Ps.: about the decay heat of the cores: maybe we can put together a rough estimation about the 'power' already removed from the cores by the cooling water. How much is the heat production of an used, 'spent' filtering tower used for the decontamination of water from the basements? How many towers were used up till now? Any information, anybody?

I wonder if it's worth it. I think it's bound to be only a couple of percent of the total and we have much larger sources of uncertainty still - such as exactly for how long the fuel had been used before scram.

 

[SteveElbows]

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120302_05-e.pdf

My question is: will they continue to operate the radioactive filtering, or they will just switch to the desalinating facility?

As I understand, damaged spent fuel under water releases the fission products continuously: so if they cease filtering for radioactive materials then the radioactivity of the water in the pool will start increase again (if the pool contains damaged fuel: I think it likely does in case of U3 and U1).

For the SFP of U1 they had stopped the filtering for radioactive materials. Do we know anything about the concentrations afterward?

It sounds like they just did it in order to get ready for desalination, although I suppose they could restart filtering again later if they needed to.

Did they even filter unit 1's pool? I don't remember, I know they did reactor 2's pool because here are the results:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111206_01-e.pdf

For reference, here are initial evaluations of fuel pool contamination:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110825_02-e.pdf

Also http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110906_03-e.pdf and http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110624_02-e.pdf and http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110708_02-e.pdf

 

[SteveElbows]

Thank you, SteveElbows.
That is exactly the kind of info that would help, if it is available for prior dates as well, ideally at least monthly since the accident.

November: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111118_01-e.pdf

December: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111212_01-e.pdf

Before then it looks like the published data was not in such a comprehensive format, e.g.:

October: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111021_02-e.pdf

September: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110909_02-e.pdf

Also a document from late October that contains a load of detail about the facilities, and some charts towards the end:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111029_03-e.pdf

 

[etudiant]

It sounds like they just did it in order to get ready for desalination, although I suppose they could restart filtering again later if they needed to.

Did they even filter unit 1's pool? I don't remember, I know they did reactor 2's pool because here are the results:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111206_01-e.pdf

For reference, here are initial evaluations of fuel pool contamination:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110825_02-e.pdf

Also http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110906_03-e.pdf and http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110624_02-e.pdf and http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110708_02-e.pdf

Thank you, SteveElbows, for this very helpful data.
Does not the relatively low radioactivity in SPF 4 invalidate the hypothesis that the explosions in reactor 4 arose out of a fuel cladding failure after the SPF ran dry?
Surely SPF4 would be much more contaminated if unclad, partially used fuel pellets were in the water.

Separately, I'm puzzled by the reference to Iodine 131 levels on P13 of your previous linked document here:
http://www.tepco.co.jp/en/nu/fukushi...11029_03-e.pdf

That shows I 131 levels at about 10**4 Bq/cc pretty steadily from June to late Oct. As this is about 20 half lives, something does not jibe.

 

[SteveElbows]

Thank you, SteveElbows, for this very helpful data.
Does not the relatively low radioactivity in SPF 4 invalidate the hypothesis that the explosions in reactor 4 arose out of a fuel cladding failure after the SPF ran dry?
Surely SPF4 would be much more contaminated if unclad, partially used fuel pellets were in the water.

Separately, I'm puzzled by the reference to Iodine 131 levels on P13 of your previous linked document here:
http://www.tepco.co.jp/en/nu/fukushi...11029_03-e.pdf

That shows I 131 levels at about 10**4 Bq/cc pretty steadily from June to late Oct. As this is about 20 half lives, something does not jibe.

I think much interest was lost in SFP 4 explosion hypothesis after such data came out, especially when combined with videos of the pool contents, and alternative explanation for building 4 exploding. Especially when combined with the info about the reactor well & d/s pit water flowing into the fuel pool due to gate losing its seal. Japan realized that reactor 3 pool was more of a concern than reactor 4 pool as early as the day they tried to drop water from the helicopter, but it took others much longer to accept that unit 4 fuel pool was not the nightmare that had been assumed. This was one of the most striking things about the transcripts of the US NRC that were released a little while ago, the guy they sent to Japan had trouble accepting that the pool still existed or had water in it, even after he had seen the first helicopter video. This is very understandable given the decay heat in that pool and the explosion, and we kept talking about unit 4 pool in a scary manner for a lot longer, but eventually it became clear that the reactor 3 pool was probably worthy of more attention than reactor 4's.

As for the I131 stuff in that chart, I spent a while staring at the underlying data and decided that its the same as is available in the other relevant press release handouts that I linked to (e.g. September and October links in my last post).

But what they have done is to plot on the graph the I131 levels even when the raw data shows that I131 was N.D (below detection limit). They have plotted the detection limit that is shown under the N.D, and failed to make any mention of this on that chart, so it causes confusion. Some of the very first entries from June were not below the detection limit.

e.g. this one (of quite a few others that I won't post now) from June:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110624_04-e.pdf

By August its gone N.D as we can see from these handout for August which I just located:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110812_01-e.pdf

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110820_02-e.pdf

As usual their detection limits fluctuate a bit, and that's what's ended up being plotted on that chart.

For comparison the last page of this document shows us JAEA analysis of water from turbine buildings of all 4 of the reactors, sampled in the latter part of march and analysed in mid april.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110522_04-e.pdf

As usual, reactor 2 gives us some rather large numbers as a starting point.

 

[etudiant]

I think much interest was lost in SFP 4 explosion hypothesis after such data came out, especially when combined with videos of the pool contents, and alternative explanation for building 4 exploding.

As for the I131 stuff in that chart, what they have done is to plot on the graph the I131 levels even when the raw data shows that I131 was N.D (below detection limit). They have plotted the detection limit that is shown under the N.D, and failed to make any mention of this on that chart, so it causes confusion. Some of the very first entries from June were not below the detection limit.

.

Thank you, very helpful again.
You have more dedication that I do, to pore over the TEPCO releases that carefully.

Am still a little surprised by SPF 4, as the sharp decline in emissions was pretty exactly coincident with the spraying of water onto it, around Mar 19 if memory serves. There must have been something else happening concurrently that was not adequately appreciated.

 

[tsutsuji]

Continuation of the 1 March report translation (part 3)
https://www.physicsforums.com/showpost.php?p=3795578&postcount=12465 part 1
https://www.physicsforums.com/showpost.php?p=3796935&postcount=12485 part 2

1 March report http://www.tepco.co.jp/cc/press/betu...es/120302a.pdf attachment 7-3 p. 42/91 :

Attachment 7-3 Jet pump instrumentation work: implementation plan and problems (insertion work)

1. Work flow

①transportation of machinery and materials⇒②installation of machinery and materials⇒③work preparation⇒④thermocouple insertion⇒⑤final check of work execution

2. Problems (constraints as regards application methods and feasibility) and solutions①transportation of machinery and materials

Constraints as regards application methods and feasability
* Tool and equipment design taking into consideration transportability by human force in narrow space and under high radiation, is needed.
* If the installation is on an elevated floor, there is a need to think of the method to lift machinery and materials up to the elevated place.

Solutions
* Study of most suitable design based on study of method

②installation of machinery and materials

Constraints as regards application methods and feasability
* Tool and equipment design taking into consideration workability in narrow space and under high radiation, is needed.
* If the installation is on an elevated floor, there is a need to think of the workability in such elevated place.

Solutions
* Study of most suitable design based on study of method

③work preparation

Constraints as regards application methods and feasability

[securing boundary after the pipe and the equipment have been connected]

* After the new stop valve on the pipe side, etc. is turned to "open", the following risks have to be thought :
⇒The injected water leaks (in case the water level is higher than the pipe)
⇒The reactor gasses leak (especially hydrogen, radioactive gasses)

* It is necessary to think of an equipment function that stops or lowers the leaks by purge gas supply
development of purge/seal function

* It is necessary to design a seal function using O-rings, etc.
(the perfect sealing of a cable devoid of rigidity is difficult ⇒ the design must probably be based on a leaking allowance)
* low resistance, high durability sealing function
* the sealing function must allow sealing diameter differences (sensor and cable)

Solutions
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If suitable materials and machinery don't exist, it is necessary to develop new ones

④thermocouple insertion

Constraints as regards application methods and feasability

(1) reactor gasses and injected water leaks during work execution : see work preparation

(2) materials and machinery such as the inserted thermocouple (whether universal products are suitable)
selection of a thermocouple that responds to the insertability, measured temperature range, radiation conditions.

constraints regarding cable thickness
* it must be both flexible enough to pass elbows and rigid enough to be insertable
* it must be able to pass the orifice (about Ø 6 mm)
* selection of material with concern for degradation (a periodical replacement is also an option)

protection of the extremity during insertion
* If the thermocouple is not protected, it will be hurt during insertion, so that a protection is necessary, which does not prevent temperature measurement.
* In function of the chosen protection method, the temperature sensing responsiveness can be reduced

study of accompanying material
* In order to confirm arrival at destination, etc. an accompanying camera is desirable.
(regarding size, passing the orifice is a problem)

Solutions to (1),(2)
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If suitable materials and machinery don't exist, it is necessary to develop new ones

(3) mechanism for the inserted thermocouple, etc. (features to be developped)
* As the stroke is long, insertion might not be possible by pushing force only

Study of insertion mechanism
* Reducing the candidates to a short list, the features are checked in mock-up tests (it is possible that universal products won't pass the tests)
* Insertion resistance control method when insertion is performed in accordance with the pipe (it is necessary to feel elbows, orifices)

Solutions to (3)
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If suitable materials and machinery don't exist, it is necessary to develop new ones as follows:
⇒self propusion of the extremity (a new development is necessary, but as the diameter is small, it is difficult)
⇒self adjustment of the extremity (development of a mechanism to change the direction of the extremity so that the insertion is performed in accordance with an elbow, etc.)
⇒auxiliary mechanisms (study of insertion auxiliary methods using compressed gas, compressed water, etc.)

(4) In relation with the insertion device (important elements to be developped)
As the necessary equipments related to insertion power, insertion mechanism are not available on the market, new specialized equipments have to be designed and developped.
If the sealing function is necessary, the insertion device itself will become a boundary, and the soundness as boundary is necessary.

Development ES uncertainties
Compared to the first entry equipments, the stroke is long and it is necessary to pass through narrow and complicated routes (it is necessary to meet the conditions mentioned in (3)), so that it is difficult to respond within a normal development duration.

Solutions to (4)
* With the shortest ES duration in mind, it is necessary to develop a new insertion equipment combining parts available on the market.
* Check suitability with mock-up

⑤final check of work execution

Constraints as regards application methods and feasability

(1) Arrival criteria : arrival at the tip of nozzle N8 "Jet pump instrumentation line penetration seal (reactor outside)" is a prerequisite (no insertion into reactor inside)
* In case the thermocouple is inserted alone, stroke management is a prerequisite.
* In order to check arrival with certainty, simultaneous insertion of camera, etc. is desirable (whether the size allows the passing of orifices is a problem)

Solutions to (1)
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If arrival cannot be confirmed, a new development is necessary

(2) Check of measurement object (check of contact / verification of measured temperature)
When it is judged that insertion and arrival have been completed, is the measured temperature that of the nozzle metal ? Or is it that of the nozzle atmosphere ? It is necessary to make that clear.

* With machinery and materials in mind : check of arrival and contact (if the tip of the thermocouple is protected by a protective part, there is no direct contact)
There is a risk that if the arrival is checked with the stroke alone, it will be difficult to reach a conclusion on the sensor position.

Solutions to (2)
* adopt clear criteria
* analysis-oriented study
⇒making assumptions on reactor interior status, execute heat transmission analyis, etc. of reactor lower part, nozzle, nozzle interior atmosphere, etc.
⇒study of responsiveness against temperature variations.

 

[SteveElbows]

Thank you, very helpful again.
You have more dedication that I do, to pore over the TEPCO releases that carefully.

Am still a little surprised by SPF 4, as the sharp decline in emissions was pretty exactly coincident with the spraying of water onto it, around Mar 19 if memory serves. There must have been something else happening concurrently that was not adequately appreciated.

Too many things occurred within short time periods, its hard to be certain. For instance the initial fire department spraying of pools started on the 19th but they started with reactor 3 pool, and if I remember correctly they didn't start on reactor 4 pool till the 20th. Somewhere around then they also pumped water into reactor 2 fuel pool using an existing piping system. It is also quite questionable as to how successful these spraying attempts were, we saw video of some parts of reactor 3 spraying at this point, and it was a bit of a struggle. Only with the arrival of the concrete pumping equipment did confidence increase that the pools were being replenished effectively.

The same is true for one of the other factors which caused unit 4 fuel pool concerns in the first place, the fact that the estimates for release to the environment were so high on that day, and detected levels on site rose considerably. But since something happened at reactor 2 on the same morning, its not possible to attribute this to reactor 4 pool with any certainty.

I don't like to draw solid conclusions due to the quality of the data and unanswered questions, the fuel in pool 4 may not be in completely perfect health. But if some of the really bad scenarios for this pool had readily happened, I would have expected to see more evidence of this by now, rather than workers busy operating in that area of reactor 4. The possibility of the pool collapsing seems to have been a real enough risk that they spent time constructing a support structure underneath, but once this was done my attention largely turned elsewhere. If some new piece of data or fact emerged I would take interest, but most of the big questions I dwell on these days relate to reactor 2. And at some point more detail of reactor 3's fuel pool will become clear, which may or may not be noteworthy.

 

[zapperzero]

Has anyone been trawling through the NRC FOIA releases?

I have just started but I find it rather hard going. Some things are just par for the course for the NRC - the text appears to be scanned off hardcopy and is not OCR'd properly. There are lengthy deletions too. Some of the contributions from people such as DOE reps and someone from "Pan Asia" -whatever that means- are entirely blacked out, there are entire telephone conferences which have been recorded and transcribed, but the entire transcript is blacked out and not even a list of participants is available.

Some bits and pieces, from here:
pbadupws.nrc.gov/docs/ML1205/ML12052A109.pdf

There's supposed to be a lot of GE folks over there doing refueling anyway

REDACTED: You know, we, we'll sort of stepped back, once the two,
Tepco and USFJ got together because obviously --

[about Unit 3 blowing, as far as I can tell]:

my worst fear has been that we, we finally got the steam explosion. breached the primary containment.

these are all conversations being had on the 14th I believe.

Also kindly look on page 258 - I am summarising here because I can't be bothered to transcribe it:

a certain Jack Grob is saying that
- unit 2 has just gone boom
- there is a wind towards the SW
- there is a US carrier in port 10 miles SW of Tokyo and it's measuring 10-20 mrem TEDE over 12 hours and roughly 10 times that thyroid dose.

Following pages are all about disbelief and checking these numbers and working back to what the dose rate may be on-site and a lot of oohing and aaahing.

Then even later (pp 278 and following) there is this Jim Trapp guy who's saying the data he got from a NISA engineer is that there is no water in SPF#4, there is a fire somewhere in there and the dose rate at the site boundary is 10 rem/hour (that would be 0.1 Sv/h).

 

[jim hardy]

109 ?? I read 107 and 108, will have to find yours.

What i got from those two is they were guessing as much as the rest of us.
All real information has been redacted.

Search on "pipermail fukushima" is more informative.

 

[tsutsuji]

Has anyone been trawling through the NRC FOIA releases?

I have read a part of http://pbadupws.nrc.gov/docs/ML1205/ML12052A105.pdf. I was surprised with their discussion of the 1.5 mrem/hour claim by a Yokosuka base admiral (page 245 - 247/296) without any comparison with any other Yokosuka measurements that might be available from civilian sources, such as http://www.bousai.ne.jp/vis/jichitai/kanagawa/ . Did they know that there is something called "the internet" where one can find data ?

 

[zapperzero]

I have read a large part of http://pbadupws.nrc.gov/docs/ML1205/ML12052A105.pdf. I was surprised with their discussion of the 1.5 mrem/hour claim by a Yokosuka base admiral (page 245 / 247/296) without any comparison with any other Yokosuka measurements that might be available from civilian sources, such as http://www.bousai.ne.jp/vis/jichitai/kanagawa/ . Did they know that there is something called "the internet" where one can find data ?

I read in the document I referenced something about NRC interacting with NISA via a translator. I doubt anyone at the decision-making level in NRC knows any Japanese and from personal experience I can attest it's pretty hard to get in-depth info about Fukushima when you don't have tsutsuji on your team.

 

[Thalic]

I read in the document I referenced something about NRC interacting with NISA via a translator. I doubt anyone at the decision-making level in NRC knows any Japanese and from personal experience I can attest it's pretty hard to get in-depth info about Fukushima when you don't have tsutsuji on your team.

Well put ZZ. I too really appreciate tsutsujisan.

 

[Shinjukusam]

Very big props for tsutsujisan. He's single-handedly keeping me from studying harder ;)

 

[Borek]

tsutsuji-san devotion is remarkable

 

[jim hardy]

Amen to that .

Thank you, Tsutsuji.

 

[Yamanote]

Yesterday they removed the big overhead crane of unit 4. Good job.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120306_01-e.pdf

 

[tsutsuji]

http://www.yomiuri.co.jp/science/news/20120303-OYT1T00456.htm A team led by Hidesada Tamai of JAEA will make a presentation about unit 1's meltdown at the Japan Atomic Energy Society meeting in Fukui on 20 March. Together, the two IC systems were supposed to supply cooling for 16 hours. If they had been turned on within 1 and a half hour, the meltdown could have been averted.

http://www.aesj.or.jp/meeting/2012s/e/12Spr_program18-44.pdf page 20 :
B12 : Hidesada Tamai (JAEA) Study of progression until core uncovering at Fukushima Daiichi unit 1, using TRAC-BF1 (1) shift of coolant distribution inside reactor
B13 : --------------- (2) Consequences on reactor cooling by Isolation Condenser

 

[SteveElbows]

Yesterday they removed the big overhead crane of unit 4. Good job.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120306_01-e.pdf

Yeah, visible progress at reactor 4 building has been notable and good to see. Quite the contrast to reactor 3 upper building where progress looks, from the very few images we have seen recently, to be painfully slow.

By the way since reactor 4 has come up again a few times in conversation recently, I thought I would mention the shroud. Back in the day some of us were interested as to what stage the core shroud replacement had reached at the time of the accident. I can't remember whether we ever found out, but I just noticed that one of the ICANPS interim report attachment documents has a diagram that shows the shroud located in the dryer separator pit ( http://icanps.go.jp/eng/120224Siryo04Eng.pdf page 165/attachment IV-40 ). May have seen a very similar diagram in the past but I thought Id mention it just in case we hadn't. edit - I went back and checked and I was talking about a very similar diagram at the end of June so this isn't news.

 

[Yamanote]

Together, the two IC systems were supposed to supply cooling for 16 hours. If they had been turned on within 1 and a half hour, the meltdown could have been averted.

This fact still drives me nuts...

As there is less destruction and radiation at unit 4, it is easier to make progress there and it makes imho sense to secure the spent fuel pool asap. At least the crane can't fall into the pool during an earthquake anymore...
As for units 1 to 3, radiation and contamination still seems to be too high to extend works, so they have to wait until radiation has declined. I don't think it makes sense to send in more people at that point in time. For the reactor cores the damage is more or less done, I see more danger coming from the spent fuel ponds, where a meltdown is still possible.

By the way - I saw a picture of a nuclear power plant (I guess it is one in Canada) with eight reactors very close to each other. Such a plant layout appears to be quite dangerous with respect to the events in Fukushima.
What's your opinion on that?

 

[al2207]

it is Pickering in Ontario much less dangerous ( no big earthquake fault near )
even if they loss all exterior power Candu can still produce up to 40 % of power generation for internal use and dump the rest of steam in condensing unit

 

[jmelson]

Yesterday they removed the big overhead crane of unit 4. Good job.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120306_01-e.pdf

Ah ha! I expected that this was one of the big things they could start working with, unloading
the SFP of #4, and that was going to require removing a lot of damaged equipment that
would be in the way. Unloading the fuel from that pool will be a very tricky bit of work using a traditional crane which has no way to orient the hook like a FHM does. The unused fuel
can just be pulled out, the old fuel might be able to be removed under water deluge, but the
recently burned fuel will be quite a challenge to remove. Possibly they can still use transfer
casks to get it out of there, one element at a time.

The rest of the reactors are too hot to do a lot of work on at least for several years.
Maybe some of this endoscope work will at least allow them to figure out where the
fuel is, and maybe eventually some of the other fuel pools can be emptied, also.

Jon

 

[Joffan]

Unloading the fuel from that pool will be a very tricky bit of work using a traditional crane which has no way to orient the hook like a FHM does. The unused fuel
can just be pulled out, the old fuel might be able to be removed under water deluge, but the
recently burned fuel will be quite a challenge to remove. Possibly they can still use transfer
casks to get it out of there, one element at a time.

My thought was that they might construct a water channel and tower on one side of the spent fuel pool, then take fuel out into a (new) ground-level pool through a lock, in water the whole time. But there might be craned solutions that are simpler and indeed safer over the whole operation.

it is Pickering in Ontario

- or Bruce on Lake Huron. But the same considerations apply.

 

[thebluestligh]

http://pbadupws.nrc.gov/docs/ML1110/ML11102A041.pdf

MEMBER CORRADINI: The only reason I ask the question is, from the same public sources I think we are all looking at, Unit 1 is the only one that is showing pressurized.

MR. RULAND: That's correct.

-----

MEMBER ARMIJO: I've been there, (Japan) you know from a hazy recollection, they were very similar, if not identical, to the U.S. plants. But I have heard all sorts of stories that they were different, and I had wondered -- I would like to know if the NRC has drawings of the plants as they currently exist.

The other thing I know about the Japanese, they were very careful to follow the safety upgrades that the NRC required in the U.S. plants---CHAIRMAN ABDEL-KHALIK: Now, with regard to the spent fuel pools, it is my understanding that the emergency operating procedures used by the Japanese are similar to those used at U.S. plants.

And for both BWRs and PWRs, the emergency operating procedures focus on maintaining the critical safety functions of the reactor.

Nowhere in the EOPs are the operators asked to check the status of the spent fuel pools.

Given what happened at Fukushima with regard to the spent fuel pools, should the licensees be asked to evaluate the adequacies of their EOP?---

And with a hardened vent -- the vent, prior to the venting operation, still filled with oxygen, so the chance of a deflagration inside the vent is real, if you vent hydrogen through that.

 

[Rive]

Unloading the fuel from that pool will be a very tricky bit of work using a traditional crane which has no way to orient the hook like a FHM does.

As I understand this for unit 4 they will use external cranes only to move the transfer casks to- and from the pool, and they will repair and use the FHM to move the fuel within the pool to the transfer casks.

But first they will have to repair the FHM of the common pool and start to prepare it to receive the removed fuel from unit 4.

 

[triumph61]

It looks like that the Fuelhandlingmachine (upper Part) is also removed.

 

[Rive]

That's just the overhead crane trolley and the main beams. The FHM is still in place.