Saturday, January 18, 2014

#Fukushima I NPP Reactor 3: Water Leak from MSIV Room Could Be a Huge Problem for Nuclear Reactor Safety

(UPDATE 1/19/2014) New post with nuclide analysis result.


This is a follow-up on yesterday's post.

TEPCO released the video which was being taken by the robot on the first floor of Reactor 3 and which was being monitored by a TEPCO employee who noticed the water.

The flow looks significant and fast.

From TEPCO's photos and video library, 1/18/2014:

Location of the MSIV Room:

Radiation levels on the 1st floor of Reactor 3, from yesterday's post:

The main steam isolation valve (MSIV) is one of the two most important safety systems in a nuclear reactor (the other one being the control rod drive mechanism). It seals off the water/steam from the Pressure Vessel in case of an emergency (like a big earthquake). This MSIV system is not supposed to fail.

If the MSIV of Reactor 3 was damaged during the March 11, 2011 earthquake/tsunami (either one) and the water has been leaking ever since, the safety standard for nuclear reactors around the world may be impacted, says one nuclear researcher that I follow on Twitter.

(Oh wait... Does it mean then that part of the reason why the water (coolant) inside the Reactor 3 Pressure Vessel dried up was because it was leaking through the damaged MSIV?)

To get a feel for the size of the MSIV, here's a photo and a video from one of the top manufacturers, Flowserve:

The 1st floor of Reactor 3 is where the human workers ventured in in June 2011 for the first time since the start of the accident on March 11, 2011 and took the smear samples from the floor. The result of the analysis of the smear samples, if it was ever done, hasn't been released.

The location of the floor drain funnel is near the equipment hatch shield plug that was found slightly open, through which highly radioactive steam/water had been leaking. (TEPCO finally admitted the shield plug had been open on April 19, 2012, more than one full year after the start of the accident.)

Packbot was sent on November 18/19, 2011 to clean the hatch rail with what looked like a white towel. The result of the analysis of what the towel caught, if it was ever done, hasn't been released.

(Now I think about it, the towel Packbot was using was soaking-wet, and even on the next day after the cleaning the guide rails were very wet. I have assumed the water on the guide rails was from inside the Containment Vessel, but is it possible that it has been coming from the MSIV Room?)

From @BB45_Colorado, one of the nuclear researchers that I follow:


If the leak from (or from near) the Main Steam Isolation Valve is from the start of the accident, that means the MSIV couldn't withstand the earthquake and/or internal abnormal pressurization. This is bad in the heart of the BWR safety design. It could affect the safety reviews worldwide.

Browsing the articles by the mainstream media in Japan (eg. Yomiuri, Mainichi/Kyodo) on this incident, it seems to me that they don't know what MSIV is or its importance.


Anonymous said...

Good post. This does look significant coming from the area of Main Steam Isolation Vlv, however if I remember correctly aren't there expansion bellows in the room as well? If TEPCO is working to find the source of the leak I would hold off on further comment and conjecture until that determination. Au_Canary

Anonymous said...


What is the presumed flow path in the TEPvid?

".. there is no leak from the reactor building to outside.
There is no statistically significant change observed at the monitoring posts and in the plant parameters (amount of water injected into the reactors, temperatures .."

arevamirpal::laprimavera said...

Anon at 11:40PM, see the image below the video.

Anonymous said...

Curious looking stainless steel tubes or rods laying there. Wonder where they came from. Pins?

Anonymous said...

From the schematic the piping comes in from the Containment Vessel, so the vessel must be flooded to at least that level. 1st floor so it's not groundwater.

Anonymous said...

In April 2012 they had a camera in the same area, and there was not much water that time

This might indicate that the water leak has started after April 2012. Corrosion caused by seawater?

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