Saturday, May 31, 2014

#Fukushima I NPP Reactor 3 MSIV: Leak Is From Expansion Joint That Connects to Main Steam Pipe

Just like the survey above the grating on April 23, 2014, TEPCO's workers inserted the pan-tilt camera from the floor above to identify the location of the leak in the MSIV room in Reactor 3 on May 15, 2014. They used a hook to lift a portion of the grating so that the camera could go below the grating.

They found a leak, and it was from the expansion joint that connects to the Main Steam Pipe D, one of the four Main Steam Pipes.

From TEPCO's photos and videos library, 5/15/2014:

Leak was found from the expansion joint to the Main Steam Pipe D, which is in fact hidden from view. What you see in the foreground is the Main Steam Pipe C and the Expansion Joint C. Leak is marked by red circles in the photo (English labels are by me):

So, the MSIV (Main Steam Isolation Valve) itself may have worked exactly as it is designed for, which is to shut off the steam from the reactor in case of a severe accident that would necessitate the scram (we don't know for sure, unless someone enters the MSIV room and investigate), but the leak is from the joint right before the MSIV.

Here's the video, showing the leak (look very closely after 33 seconds):

Bad news, I think, for reactors around the world, but no one in the media has picked up on the significance of the news so far.

This is the typical reporting that I've seen in the Japanese media:

"A leak was found on the Containment Vessel of Reactor 3 for the first time."

Clearly, reporters don't bother to know what MSIV - Main Steam Isolation Valve - is. They don't seem curious either to ask questions like:

How did the expansion joint get damaged?
Was it by the earthquake?
Was it by pressure that exceeded the spec?
Was it by high heat that exceeded the spec?
If it was high pressure, what caused the high pressure?
If it was high heat, what caused the high heat? What are the implications for other nuclear power plants in Japan (and the world) that use this type of joints for many critical safety components in the plants?

Instead, they'd rather write about "nosebleed" in Fukushima Prefecture and how TEPCO's employees "disobeyed" the order and fled from Fukushima I NPP on March 15, 2011 (that's according to fanciful Asahi Shinbun). (More later, maybe.)

Below are the tweets from "Happy", who was hoping that the leak would be from one of the auxiliary pipes that comes through the Containment Vessel, such as the drain pipe: 3号機のMSIV室の漏洩は、やっぱりドレンじゃなくてベロー部からだったでし。PCV漏洩止水にスポットがあたってるけどオイラは、これが地震による配管破断だとしたらとても大きな事で、全国の原発再稼働に待ったをかけるべきなんだけど…。

The leak in the Reactor 3 MSIV Room was from the bellows [expansion joint], not from the drain pipe. A focus is on how to stop the leak from PCV (Primary Containment Vessel), but I think it's a serious stuff if this is a rupture of the pipe because of the earthquake, and the restart of nuclear power plants in Japan should be halted... 3号機MSIVのベロー部漏洩が地震による配管破断だとしたら、何故大きな問題になるかと言うと、この伸縮継手は重要な配管やPCVやRPVベッセル等々、至る所で使われているタイプで国内全ての原発が同じタイプを使ってると言っても過言じゃないんだ。

The reason why it is a big problem if the leak from the bellows in the Reactor 3 MSIV Room was from the rupture of the pipe caused by the earthquake is because this type of expansion joints are used everywhere on important pipes, PVCs, and RPVs (Reactor Pressure Vessels), etc. It's no exaggeration to say that every single nuclear power plant in Japan uses the same type of expansion joints. ベロー部(伸縮継手)の基本設計は、どちらかと言うと耐震性より熱による配管の伸縮吸収を考慮した設計だから今回、もし地震の影響だとしたら基本設計を見直さないとダメなはずなんだよね。原発ムラが一番怖れてるのが、この地震による配管破断なんだ。

The basic design of a bellows (expansion joint) takes into account the expansion and contraction of the pipe by the heat, rather than the seismic resistant capacity. If [the damage] is from the effect of the earthquake, the design would need to be revised. What the "nuclear village" is most afraid of is the rupture of pipes due to an earthquake. だから未だに現場検証も線量が高い理由で実施しないんだと思うんだけどね。これはオイラの予想だけど、たぶん国や東電が考えて出すMSIVの漏洩原因は、「地震じゃなくて設計圧力以上の圧力がかかった」とか、「異常に高い温度熱が原因だった」とかの発表を数値を出して説明すると思うでし。

That's why I think the on-site investigation hasn't been done, ostensibly due to high radiation. I expect the reason for the MSIV leak that the national government and TEPCO will come up with will be "due to the pressure that exceeded the design pressure, not the earthquake" or "due to extremely high temperature," citing some numbers.

Well, even if they say the damage was due to high pressure or high temperature, I would assume the critical component like this that connects to the super-critical component (MSIV) should not fail in a severe accident that would probably generate high pressure and high temperature that would exceed the design specs.


VyseLegendaire said...

Well, even if they say the damage was due to high pressure or high temperature, I would assume the critical component like this that connects to the super-critical component (MSIV) should not fail in a severe accident that would probably generate high pressure and high temperature that would exceed the design specs."

You assume wrong, then.

Anonymous said...

The leak may be caused by long-time contact with corroding seawater...

Anonymous said...

There are two MSIVs in series, one inside the containment and one outside, so that risk of MSIV failure would be very unlikely as both valves would have to fail. This leak appears to be outside the containment but in between the 2 MSIVs. It's weird. Has it been confirmed that this leak occurred at the time of the accident? Or has it developed since then?

Joffan said...

Good eye spotting the leak - a steady flow visible just left of the support column.

Although this leak is obviously undesirable, the typical design basis for reactors is that they can continue to cool safely with a full-bore pipe rupture - which I'm going to guess this is not.

Equally obviously this could be another lesson to learn in improving nuclear reactor equipment for robustness to extreme events - always being aware that changes to address one problem can sometimes create another vulnerability. The oft-requested shutdown of plants to reach ever-redefined "perfection" is a poor option that ignores the immediate continuing benefit of nuclear electricity in normal operation.

Anonymous said...

Help, I'm confused (nothing new, I know). The last thing I thought I understood was the confusion where the water was coming from in the first place. I.e., it couldn't be feed water because it was too warm and too contaminated, and it couldn't be water from the containment bottom because it was too high up and not enough contaminated. Or something like that. Tepco thought initially it was rain water, but that didn't make sense either.
Did we meanwhile get an understanding where the water is coming from?
Thanks for any clarification.

Anonymous said...

mscharisma, the expansion joint connects to the main steam pipe that comes directly from the pressure vessel. The water is from inside the pressure vessel.

Anonymous said...

@ Anonymous 3:34 PM

Quote: "The water is from inside the pressure vessel."

If so, then the water level would be covering the core, but the water level has been so low as to uncover the core since the accident. In fact, it is the low water level that caused the meltdown. Tepco I think is pretty certain that the pressure vessel no longer holds water as the melted core has almost certainly caused leaks in the bottom. How could the pressure vessel's water level be this high, after the leaks were caused in the bottom?

Second, there is another MSIV inside the containment. The pipe does not come "directly from the pressure vessel." For the water to come from the pressure vessel that second valve has to have a leak, but the valves themselves are built to very high standards. I don't think it will be known for some time where this leak is from.

Anonymous said...

Thanks for the info/discussion on the origin of the leak. Much appreciated.

Unknown said...

Expansion joints are widely used in pipeline systems. They are vital elements for these technologies. The main reason why these flexible expansion joints are used is because they compensate different variations that may appear in length. Thanks for your blog i learn more.

Unknown said...

Great discussion! Rubber expansion joints are the perfect solution for pipe systems to absorb movements, vibrations or noise, resulting in the significantly prolonged service life of the pipe work and connected equipment. It can compensate small inaccuracies in assembly and are used as pipe adapters for inspections.

Vallabh Engineers said...

Thanks!, for sharing such useful information with us. Vallabh Engineers known as one of the best Pipe Expansion Joints Manufacturers.

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