Japan Earthquake: nuclear plants

thebluestligh

Hear Hear, thank you Tsutsuji!

Azby

Yes, Tsutsuji has made a tremendous and effective effort to keep us informed. I absolutely appreciate it.

clancy688

The burden of the Chernobyl clean-up was no small part in the collapse of the Soviet Union either...

tsutsuji

Thanks everybody for the encouraging comments. I have started translating http://www.meti.go.jp/earthquake/nuc...120827_02c.pdf "Progress status of development of machinery and equipments to prepare fuel debris removal" which will give a glimpse of the research & development planned by Toshiba/Hitachi/Mitsubishi over the longer term. But this will take me quite some time as these are 34 pages, some of which are rather dense.

The first diagram:

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mscharisma

No takers or too dumb or complicated a question? Thanks.

MadderDoc

What _can_ they do, except do trial adjustment of injection while monitoring temperature trends. I'd expect them to be pretty 'familiar' by now with what can be expected by the beasts they are handling, although as you point out they are beasts pretty much inside black boxes.

turi

I assume that the reported injection rates are those measured before and/or after the pumps and that they don't know how much water actually reaches the damaged cores. But as MadderDoc says: It's not that important whether those numbers reflect the exact amount of water reaching the reactor insides but whether adjusting those rates changes other measurable parameters (temperature, pressure) at various measuring points.

jim hardy

mach i think a simple heat balance suffices

they know the boundaries and how much they're pumping in and about how much heat the core is making, so they also know what should be conditions exiting those boundaries;
successful control of temperature coming out confirms those expectations.

SteveElbows

They also used crude but informative observations during the period last year where they were still trying to find the right balance. For example at reactor 2 they had seen steam from containment entering the upper building levels. When they looked again later (perhaps September) after making various changes to water flow rates & location , they saw no steam and the paint had flaked off of the overhead crane, suggesting the atmosphere was now much less humid.

They shouldnt have used the term cold shutdown, since that implies a routine state and this situation is anything but, and the term 'relatively stable' is fairer in my book. Relative to how unstable the reactors were earlier on, newsworthy events in the reactors that can be detected by humans have been few since the early months.

Knowledge about the state of the cores is obviously far more limited than we'd like, but its not surprising that it will take years to learn more. In the meantime I dont think many would claim that the available monitoring data is perfect, especially at reactor 2 where there are far too few correctly functioning temperature monitoring devices working in many important parts of the reactor. Indeed when many of these sensors started to go wrong, resulting concerns about reactor 2 temperature rises were the biggest safety scare we've had for a long time, until they decided it was faulty sensors rather than actual temperature rises. I think they just lost another temperature sensor at reactor 2 the other day, although it may not yet have officially been declared as broken quite yet. So they better hope the mission to try fitting replacement sensors works, though its certainly not an easy mission and the state of the reactor core may well be responsible for the problems they have already faced with an 'obstruction' at the end of the pipe they originally wanted to use. In the meantime they will just have to rely on temperature indications in other parts of the reactor, and observations such as the steam one I mentioned earlier.

SteveElbows

Some bits and bobs:

Over at Fukushima Daini reactor 4 they are going to open the top of containment and remove the RPV lid, steam dryer & separator on September 10th.

http://www.tepco.co.jp/en/press/corp...20903e0403.pdf

The latest building integrity study of Daiichi reactor 4 found a few more cracks but nothing they think is significant. One of the photos that was originally part of this release caused a small internet stink because they had crudely photoshopped out the area of the west wall where the truck bay used to be before they demolished it. In response to the complaints they simply reissued the photo with the section cropped out instead of painted over, and mention security of nuclear material as the justification. Personally I do not suspect they were hiding anything too interesting, so its another one of those stories which is more about crude censorship backfiring, suspicion and lack of trust in official information than anything else. Anyway, here is the report:

http://www.tepco.co.jp/en/nu/fukushi...20830_02-e.pdf

More recent attempts to discover the cause of the reactor water injection flow rate decreases are discussed in the September 7th plant status press release. The temperature sensor that has become suspect at reactor 2 is also mentioned:

http://www.tepco.co.jp/en/press/corp...8114_1870.html

SteveElbows

At this stage I sometimes wonder if I have missed any technical reports, so I was going through some older stuff and found an english document from June 15th that I dont think I have talked about before:

Technical knowledge of the Accident at Fukushima Dai-ici Nuclear Power Station:

http://www.nisa.meti.go.jp/english/p...120615-1-1.pdf

It does not cover everything, or contain new information not seen elsewhere, but the areas it does look at are covered in pretty clear english.

Those interested in the containment equipment hatch at reactor 3 may be interested to check pages 33-37, where it discusses possible containment leak points at the reactors. They look at radiation levels detected at different points in the different reactors, and also analysis of hydrogen behaviour. They are quite clear to mention the possibility of leakage from the 'machine hatch' at reactor 3. Plenty else is discussed too, I just thought Id mention that one since on this thread we had quite a lengthy discussion about the equipment hatch at reactor 3, back when TEPCO sent a camera into that area. But as usual TEPCO were not talking usefully about leaks, leaving us to come up with our own narrative to go with the images.

SteveElbows

I forgot to mention there is also a large set of diagrams for that report:

http://www.nisa.meti.go.jp/english/p...120615-1-2.pdf

For example diagrams relating to hydrogen leak point modelling are on pages 101-106 and pages 118-122 deal with the effect that an open blowout panel can have on hydrogen buildup.

tsutsuji

http://www3.nhk.or.jp/news/genpatsu-...907/index.html The US National Academy of Sciences heard Tepco employees about the Fukushima Daiichi accident. Some tough remarks were made such as "Why wasn't there specialists on the site, able to give guidance about the condenser [the IC, I guess] ?", "there are problems with Japan's basic safety philosophy" (compared with the measures taken in the USA in consequence of the 9-11 terrorist attacks, like preparing manuals for worse case situations, and for the loss of offsite power with back-up power sources).

See also http://www.rttnews.com/1961281/tepco...ype=gn&Node=B1 (English)

tsutsuji

1) Previous related topics:

http://www.tepco.co.jp/en/press/corp.../111221e14.pdf (English) p. 54/94-94/94: "Research and Development Road Map for Decommissioning Units 1~4 at TEPCO's Fukushima Daiichi Nuclear Power Plant" (1st meeting of the Government-TEPCO Mid-and-long Term Response Council, 21 December 2011)

2) Translation: [installment 1: abstract]

01/34 (1/4)

01/34 (2/4)

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tsutsuji

2) Translation: [installment 1: abstract]

01/34 (3/4)

01/34 (4/4)

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tsutsuji

2) Translation: [installment 1: abstract]

02/34 (1/3)

02/34 (2/3)

02/34 (3/3)

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mscharisma

Okay, so we have had slightly rising temperatures in June/July, subsequently a chiller installed, and then deliberately reduced water injection rates at stable temperatures. At the end of August, we have injections rates that inexplicably dropped below the required amounts and, one has to assume, again rising temperatures as at least one of the indicators for or results of that. (By the way, thanks to everyone who responded to my question how injection rates and what gets to the core is measured.)
Bottom line seems to be, temperatures are rising. No?
And we (or TEPCO) assume(s) its because its summer and/or because something is clogging up the pipes or valves or whatever.
And so here's my new question: with so many unknowns and variables, is the real message/news here not that temperatures are rising for uncertain reasons and we're all guessing why, likely including TEPCO?