Japan Earthquake: nuclear plants

MadderDoc

The brown-stained section of the pipe is the last final bit of pipe before entry into the stack, this last bit is shared by the exhausts from unit 1 and 2 EGTS (Emergency Gas Treatment Systems).

Right above the stained part you see the forking out of one pipe up and towards south, that pipe is connected via a 90 deg bend to the smaller pipe along the fat pipe, coming from unit 2. The other fork proceeds vertically for a bit, then makes an upwards bend towards the north, and then a 90 deg bend to become aligned and connected with the smaller pipe coming from unit 1. I think you can make out the arrangement from the attached photo that is shot from the south-west.

Cesium compounds are generally colorless, so taking the color brown as an indicator color for the presence of cesium appears like madness. Quite on the contrary. if a cesium mineral is found to be brownish a geologist will reasonably suspect the color is due to the presence of impurities, e.g. Fe³⁺ impurities aka 'rust'.

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Dmytry

The stain is indicative of some sort of leak, which evaporated, depositing the dissolved material. You can guess it would include radioactive isotopes. Also the pipe bends inside meaning some dust could have deposited there. The piping would be very radioactive even if only a small fraction of the vented material had deposited.

AtomicWombat

Exactly where does the pipe come from. It's hard to follow in the Cryptome pictures. It is not the large emergency relief duct from the airspace in the reactor building. It appears to be an emergency steam relief pipe from the reactor circulation, perhaps from the condensers.

It may have flooded as a result of too much water added to the RPV. It is possible that the bottom of the stack is filled with water. I notice the most severe corrosion is at the join between the pipe and the stack. There is thick brown layer of rust on the shield below it.

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joewein

It comes from a filter room on the second floor, where also extremely high values were measured.

Attached are cropped images from a Cryptome set.

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robinson

So after something goes very wrong you vent the reactor directly into the atmosphere? What the .. ?

jim hardy

better a controlled vent through filters than waiting for it to vent itself.
Think of the engine coolant reservoir in your automobile - keeps ethylene glycol off the pavement, within its design limits.

recall the operators were VERY hesitant to use it - the top brass had to directly order it.

old jim

robinson

Why not vent it into a giant reservoir of water? So the steam condenses, and it doesn't go wafting down wind?

Caniche

First point is easy ,the reactor vessels and secondary confinement are distinct and separate.

If hydrogen collects in the secondary containment and is ignited ,then the seat of the detonation is identifiable ,but the product is less predictable.

We have been exposed to full release of the core from the day these reactors went pop, but if you pour lots of water on the nuclear pile you can limit the geographical spread(however ,local concentration does increase)

Cryptome

Here are two high-res photos of the location dated August 4, 2011, captions by TEPCO:

Stack drain pipe of exhaust stack of Units 1 and 2, Fukushima Daiichi Nuclear Power Station(from east side) (pictured on August 4,2011)

http://www.tepco.co.jp/en/news/11031...s/110805_1.jpg

Stack drain pipe of exhaust stack of Units 1 and 2, Fukushima Daiichi Nuclear Power Station(from west side) (pictured on August 4,2011)

http://www.tepco.co.jp/en/news/11031...s/110805_2.jpg

These are from TEPCO's news site updated every day or so:

http://www.tepco.co.jp/en/news/110311/

etudiant

The stack, unless filtered, then ensures maximal dispersion of the vented materials.
That does seem a serious oversight, as a bad accident is thereby made worse.
Are there not any requirements for filtering the hardened stack emissions in case of accident?

Caniche

In the UK it is termed "Cockcrofts folly" , it did however probably save much of NW England from a lethal dose in 1957. Discuss

robinson

It seems impossible that the solution to a leaking reactor is to vent it directly into the atmosphere. Seriously?

Joe Neubarth

Torus.

AtomicWombat

The documents on Tepco's site:
http://www.tepco.co.jp/en/news/110311/
Refer to the the site of the high radiation as:
"Bottom of Main Exhaust Stuck of Unit 1/2 Connection of emergency gas treatment piping arrangement"
And the location of the high radiaion inside the No.1 turbine building as:
"Near the entrance of the train room for the emergency gas treatment system."
http://www.tepco.co.jp/en/nu/fukushi...10803_01-e.pdf

Does someone have a piping diagram?
It's clear to me how the pipe relates to the reactor #1 building (it skirts around the outside south & east walls), but I am still trying to work out how it relates to the reactor plumbing. Does it come from the wet well? From somewhere in the primary circulation, such as the condenser? I.e. Where does this "emergency gas treatment piping arrangement" fit into the safety systems for a BWR?
http://en.wikipedia.org/wiki/Boiling...safety_systems

And what is a "train room"?

Bandit127

My assumption was that the "emergency gas treatment system" was the nitrogen gas feed system. If so, it is new and a result of the accident.

joewein

Since the venting system is designed to protect the containment, it must release gas from the dry well and perhaps also the top of the torus. From there it would go to the filter "train", then outside the building along the fat pipe to the stack.

According to a NYT article the hardened venting system doesn't use filters, the regular venting system does.
They were also using "train" in the sense of several connected filtering systems (like wagons on a train) when talking about the Areva water treatment system. I think the train room holds several filters trough which gas would sequentially pass before being released into the stack.

joewein

Yes, the torus provides some filtering, but only until until it starts boiling, which it eventually will without a working RHR.

Basically, the reactors were not designed to cope with a station blackout and consequently outage of the RHR that went on for more than a couple of hours (unit 1) or a few days (other units).