Japan Earthquake: nuclear plants


by gmax137
Tags: earthquake, japan, nuclear
radio_guy
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#12457
Mar2-12, 06:56 AM
P: 24
From what I recall reading, the Quince robots can operate in up to 2Sv worth of radiation reliably, I don't think the 0.2Sv measurement could have caused any problems.

I will say I question their choice of the camera lens, it makes for some quite distorted images, maybe it has something to do with radiation resistance?
SteveElbows
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#12458
Mar2-12, 07:59 AM
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Quote Quote by Rive View Post
There was no explosion, true: however judged by the survey map of the level there was something coming up around the concrete plug of the reactor, and I think it's safe to assume that it wasn't cold nor careful.
The rather unsteady footage from last September, taken from the opening in the wall of reactor 2, does show stuff rising from that area.

http://tepco.webcdn.stream.ne.jp/www...110924_01j.zip

As for the boots, we don't know if they were trying to deal with something such as sloshing of water from the reactor 2 spent fuel pool immediately after the earthquake but before the situation got too serious for people to be inside the building.
tsutsuji
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#12459
Mar2-12, 08:24 AM
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http://www3.nhk.or.jp/news/genpatsu-...302/index.html The inside of the offsite center was shown to the press for the first time since the accident. They saw the large screen supposed to show each reactor's realtime data or predictions of the spreading of radiations, which did not function at all. The phone system supposed to reach each local government's person in charge by pushing a button also did not function because of the blackout. The offsite center had no air filtering system, and the radiation eventually rose to 200 μSv/hour so it had to be evacuated. The Nuclear Safety Commission has a plan to divide offsite centers into two parts. One part would be far enough from the plant, and the other part, in charge of evacuations would be close to the plant. But the final decision has not been taken yet.

http://www3.nhk.or.jp/news/genpatsu-...0_ondokei.html On 1 March in the night, Tepco submitted its report to NISA about unit 2's alternative temperature measurements. Thermometers will be inserted through the pipes that connect to the reactor inside. It will be necessary to lower the radiations in the working environment, and in order to solve many still unsolved problems, it might be necessary to design new tools and techniques suitable for working in narrow spaces. If all the conditions are met, the measurements won't start before the end of July. Tepco is also exploring indirect methods, such as analysing the temperature of the water flowing out of the reactor.

http://www.tepco.co.jp/cc/press/betu...es/120302a.pdf The report to NISA : "Correspondence for temperature increase in the lower part of the Reactor Pressure Vessel of Unit 2 at TEPCO Fukushima Daiichi Nuclear Power Station" (Japanese).
tsutsuji
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#12460
Mar2-12, 10:11 AM
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The 1 March report ( http://www.tepco.co.jp/cc/press/betu...es/120302a.pdf ) is divided into two parts. The first half, down to page 43 is about the plan to install alternative measurement tools. The second half from page 44 to the end is the assessment of existing thermometers.

On pages 88/91 - 89/91 we find a table with the resistance values of each thermometer in unit 2. For example here are the values for TE-2-3-69H2 (Vessel wall above bottom head) :

Regular inspection value : 300.47 Ω
2011.9.29 151.71Ω 0.50
2011.12.1 153.20Ω 0.51 1.01
2011.12.12 151.80Ω 0.51 1.00
2012.1.27 151.06Ω 0.50 1.00
2012.2.13 155.32Ω 0.52 1.03
2012.2.23 173.36Ω 0.58 1.15
2012.2.23 173.10Ω 0.58 1.15
2012.2.24 175.13Ω 0.58 1.16
2012.2.24 175.23Ω 0.58 1.16
2012.2.25 174.02Ω 0.58 1.15
2012.2.26 174.13Ω 0.58 1.15
2012.2.27 173.45Ω 0.58 1.15
2012.2.28 174.74Ω 0.58 1.16
2012.2.29 173.57Ω 0.58 1.15

The rates written after each Ω value (1) are : (2) measured value/regular inspection value ; (3) measured value/lowest measured value. "1.15" means that the resistance rose by 15% between 29 September and 29 February.

A plot with TE-2-3-69H2 resistance (pink) and temperature (blue) values is available page 63/91.

Here is the footnote with the meaning of each symbol in the first column of the table pages 88/91 - 89/91 :

〇 : not assessed as being broken
A1 : not connected to the central control room with a cable (backup sensor. the high radiation in reactor building basement prevents access)
A2 : assessed as being broken during the regular inspections [prior the accident]
B1 : already reported as being broken in the mid term safety report
B2 : newly assessed as being broken (wire cut)
When the measured value is unstable inside a range we wrote down the highest value.
jim hardy
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#12461
Mar2-12, 01:57 PM
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has unit 3 top floor been covered with something?
tsutsuji
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#12462
Mar2-12, 06:42 PM
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Quote Quote by tsutsuji View Post
The 1 March report ( http://www.tepco.co.jp/cc/press/betu...es/120302a.pdf ) is divided into two parts. The first half, down to page 43 is about the plan to install alternative measurement tools. The second half from page 44 to the end is the assessment of existing thermometers.
I translate the last part of the 1 March report's first part, on http://www.tepco.co.jp/cc/press/betu...es/120302a.pdf pages 8 and 9 (what follows is attachments) :

(3) working plan for alternative thermometer equipments

a. Selection of alternative thermometer equipments and sending devices


After making comparative studies of the thermometers that are to be inserted into the pipes connecting to the RPV, and of the devices to perform such insertion, from the perspective of resistance to radiations or maximum temperature, we selected two kinds of metal sheath thermocouples and two kinds of sending devices and industrial endoscopes.

metal sheath thermocouples

* A company's metal sheath thermocouple : φ1.0mm150m (maximum temperature 650C)
* B company's metal sheath thermocouple : φ0.5mm300m (maximum temperature 650C)

sending devices

* wiring equipment : φ4.5mm30m (inserted by hand)
* industrial endoscope : φ4.0mm30m (inserted by hand. The bending wire on the extremity can be [remote] controlled)

(attachments 5 [page 38/91], 6 [page 39/91])

b. The work's implementation plan and problems

At present, the alternative means having the highest probability of implementation is the one inserting a thermometer inside the jet pump instrumentation line. Based on this, we selected a detailed working procedure and extracted the relevant engineering and feasability problems. Many problems cannot be settled unless a field study is performed, but if at least the following problems are not solved, it will be difficult to perform the work:

Problems

* Being able to lower the radiation in the work area to 15 mSv/hour or below
* In order that the RPV gasses do not flow out from the instrumentation pipe that is being cut, we plan to use an engineering method where the pipe inside is frozen (filling it with water) while cutting, but as the distance between the PCV penetration end plate and the closing valve is short (300 mm or less), the working space is narrow. Working must be possible in such a narrow space.

A survey will be performed to find detailed radiation data in the working location. After this, we will plan decontamination and shielding, and the results will be checked on location. Also, we plan to diminish the work risks by testing the frozen cutting method on a mock-up and to develop tools to enable working in a narrow space. Please note that the problems encountered if we use the routes selected as priority level 2 (through the water level gauge line, liquid control system (SLC) differential pressure detector line, or the Traversing Incore Probe (TIP)), will be nearly the same as if we use the jet pump instrumentation line, so we wrote here the detailed plans for the jet pump instrumentation line work as a representative case.

(attachment 7 [page 40/91 - 42/91])

c. Working schedule

The earliest start of work is at the beginning of July, bringing the completion of work at the end of July. The following schedule is based on the prerequisite that the working environment's radiation is lowered to a level where working is possible, that new technologies do not need to be developped (application of existing technologies), and that the conclusions drawn from the mock-up test's results do not require more than simple modifications.

The completion of tasks that have major consequences on the schedule are noted below as "hold points" (HP). We shall pay attention to the completion of each hold point, and in case the conditions are changed, we shall quickly change the plan, and head toward the installation of alternative thermometers within the shortest time as possible. Please note that there is a high probability of performing the priority level 2 works (through SLC, or TIP), so that, if possible, the field studies about those will be performed at the same time as the one for the priority 1 work (through jet pump instrumentation line).

HP1 : field study 1 (checking the working area's radiation and space) : mid March
HP2 : study of engineering method (assess if it is possible using existing technology) : mid April
HP3 : confirm an effective decrease of radiations after decontamination and shiedling : end of May
HP4 : end of the mock-up : beginning of July

(attachment 8 [page 43/91])
etudiant
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#12463
Mar2-12, 07:21 PM
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Quote Quote by RoseHeart View Post
TEPCO...what a bunch of techno spew..
Why ..oh...why I wonder does..it look like this?
http://www.youtube.com/watch?v=IZvtEf_D3zg
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
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#12464
Mar2-12, 08:35 PM
P: 1
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
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#12465
Mar2-12, 10:02 PM
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Quote Quote by mloub View Post
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
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#12466
Mar2-12, 10:19 PM
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Regarding data on water before and after decontamination, you mean this sort of thing? http://www.tepco.co.jp/en/nu/fukushi...20229_01-e.pdf
etudiant
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#12467
Mar2-12, 11:06 PM
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Quote Quote by SteveElbows View Post
Regarding data on water before and after decontamination, you mean this sort of thing? http://www.tepco.co.jp/en/nu/fukushi...20229_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
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#12468
Mar3-12, 12:22 AM
P: 242
There's one plot I've been trying to update whenever new information is provided:

http://www.physicsforums.com/showpos...ostcount=12092
tsutsuji
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#12469
Mar3-12, 02:59 AM
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Quote Quote by mloub View Post
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 :

Quote Quote by tsutsuji View Post
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 http://www.physicsforums.com/showthr...ne#post3671515

And about how to prevent ground water from flowing in :

Quote Quote by Astronuc View Post
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 :

Quote Quote by tsutsuji View Post
http://www.tepco.co.jp/nu/fukushima-...20227_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-...20227_05-j.pdf page 39/94 (my translation)
HowlerMonkey
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#12470
Mar3-12, 06:15 AM
P: 275
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
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#12471
Mar3-12, 06:46 AM
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http://www.yomiuri.co.jp/science/new...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/fukushi...20303_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
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#12472
Mar3-12, 07:45 AM
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Quote Quote by etudiant View Post
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
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#12473
Mar3-12, 07:55 AM
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The data comes from this TEPCO report:
http://www.jaif.or.jp/english/news_i...330575712P.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
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#12474
Mar3-12, 08:04 AM
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Quote Quote by rmattila View Post
There's one plot I've been trying to update whenever new information is provided:

http://www.physicsforums.com/showpos...ostcount=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.


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