Monday, May 28, 2012

TEPCO to Do Endoscopy of Reactor 1 Containment Vessel at #Fukushima, in Late August

After the Japan Nuclear Energy Safety Organization (JNES) published its analysis that the water level inside the Containment Vessel of Reactor 1 at Fukushima I Nuclear Power Plant may be only 40 centimeters deep, TEPCO announced the plan to probe inside the Containment Vessel with the endoscope, just as they did for Reactor 2.

According to Jiji Tsushin, TEPCO plans to visually inspect the inside (by two endoscopic cameras), take temperature and radiation measurements, and collect the water samples near where the fuel debris (corium) is supposed to be on the floor of the Containment Vessel.

The fuel debris (corium) in the Reactor 1 is considered to have dropped to the concrete floor of the Containment Vessel and eaten into the concrete, as having been disclosed during the workshop organized by the NISA in November last year. TEPCO's estimate is about 65 centimeters into the concrete, and the Institute of Applied Energy's estimate is about 2 meters.

From Jiji Tsushin (part; 5/28/2012):


Toward decommissioning Fukushima I Nuclear Power Plant, the plan has been agreed upon to probe the interior of the Reactor 1 Containment Vessel using the industrial endoscope and collect the sample of highly contaminated water near the fuel debris for analysis. The work will be carried out sometime between late August and mid September.



The probe of the Containment Vessel interior was done on Reactor 2 in January and March this year, which revealed the water level to be only 60 centimeters from the floor of the Containment Vessel.


In Reactor 1, TEPCO will insert the camera and radiation survey meter through one of the spare penetrations for the pipes, and collect the contaminated water and analyze in order to estimate the condition of the melted fuel. After the probe, a thermocouple will be left inside the Containment Vessel [in the water] to continuously measure the temperature of the water.

The details of the Reactor 1 CV probe are in one of the reference materials (Japanese-only; pages 18 to 25) for the May 28, 2012 meeting of the Working Group for Medium to Long Term Planning. TEPCO will have to build a mock-up first to train the workers. (I'll post some of the pages here later.)


Atomfritz said...

There is also a new handout with radiation maps in unit 1 (dated 5/25).

And, I am really getting confused.
Is this spill (610 cubic meters) at the sludge waste storage a new one or an old one?

Anonymous said...

Can someone remind me how thick the concrete layer underneath the containment vessel is? Any risk the fuel can/will eat through the entire concrete layer?

arevamirpal::laprimavera said...

mscharisma, look at the pic at the end of this post:

Concrete floor inside the CV: 2.6 meters max
Concrete below that: 7.6 meters.

Corium-concrete interactions (from wiki)

The fast erosion phase of the concrete basemat lasts for about an hour and progresses into about one meter depth, then slows to several centimeters per hour, and stops completely when the melt cools below the decomposition temperature of concrete (about 1100 °C). Complete melt-through can occur in several days even through several meters of concrete; the corium then penetrates several meters into the underlying soil, spreads around, cools and solidifies.

Atomfritz, that water leak I think is a newly found one. It must have been there for some time.

That radiation map conveniently misses the highest radiation area, which is the southeast corner where radiation can be measured in sievert/hour.

Anonymous said...

@laprimavera: Many thanks for the info and explanation. And my apologies. Am on a slow broadband connection these days with pictures turned off on web sites, so I completely missed the obvious details. Sorry about that.

Atomfritz said...

@ mscharisma:

Don't worry about melting through in Fukushima, this is practically impossible.

Better let's hope that French Hollande will keep his promise to turn off Fessenheim power plant at the Rhine, located directly at the German border. Remember, Fessenheim reactor's concrete thickness is 1.5 meters compared with the about 10 meters at Fukushima. If an accident occurs there, the Netherlands would be in a very bad situation, as they rely mainly on the Rhine for their water supply.

@ LaPrimavera

Thank you, I actually missed this interesting fact that these radiation maps just blank out the lesser "inviting" areas making #1 look way cleaner than it is. One really has to look very careful at what Tepco presents.

Anonymous said...

Thanks, Atomfritz.

madhavi said...

I am having gallbladder issues and need an Endoscopy surgery, what is entailed in this?

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