Sunday, January 1, 2012

#Fukushima Reactor 4 Skimmer Surge Tank Water Level Update

(UPDATE: Again, it is NOT about the water level of the Spent Fuel Pool. There are blogs and tweets that either deliberately or by ignorance blur the distinction between the SFP and the skimmer surge tank and create an impression that the SFP is leaking. As of now, that is simply not true, with what little information available.)

(UPDATE 2: By the way, TEPCO doesn't have a press conference until January 4. So much for "emergency" email notification.)

(Update 3: TEPCO says the earthquake sent the water from SFP to Reactor Well instead to the Skimmer Surge Tank. See my latest post.)


TEPCO's emergency email notification, as posted on Twitter by one of the freelance journalists:

Notice from TEPCO
To the Press

This mail is sent to those who have registered for "Notification in late night and early morning".


Today (January 1) 5:30PM, our employee monitoring the plant data found the water level of the skimmer surge tank was falling at a relatively rapid pace.


The water level of the skimmer surge tank goes down due to natural evaporation. In the past normal operation, the rate was 50 millimeters in 3 hours (or 17 millimeters per 1 hour). However, in 3 hours from 2 to 5PM today it dropped about 240 millimeters (or 80 millimeters per hour).


We are conducting the survey of the area with the expectation that there is a leak somewhere. So far, there is no leak on the 1st floor of the Waste Product Process Building where the cooling system for the Reactor 4 SFP is installed, and no leak outside the reactor building. We will investigate the pipe joints inside the reactor building for any leaks, and identify the cause.


As of 5PM today, the temperature of the SFP is 23 degrees Celsius. Cooling of the SFP continues, and there is no change in the water level of the SFP. As soon as ready, we will fill the skimmer surge tank with water and monitor the water level.

Do not reply to this mail.

                                  以 上


Skimmer surge tank is a tank set up to collect the overflow from the Spent Fuel Pool. In order to cool the spent fuel bundles and to remove impurities from the water, the water in the Spent Fuel Pool is overflowed into the skimmer surge tank, and goes through the heat exchanger and the filter before it goes back into the Spent Fuel Pool.


Atomfritz said...

Look at this picture to see the location of the skimmer surge tank:

1. It's below -5 degs C for quite some time now. Freezing has already helped spills open up.
2. The water in the skimmer surge tank is colder than the SFP water (23 C).
3. The whole thing is "open-air" (afaik), getting colder and colder.

My thoughts on this:
17 mm/h "normal evaporation" under these circumstances seem not very plausible to me.
Assuming water surface of about 4 sq.meters, 80 mm/h water loss is about 250 liters/h.

Another surprise opening up?

arevamirpal::laprimavera said...

250 liters? not 320?

Anyway I'm asking Kino (journalist) to ask about it in the press conference which, I think, will be on January 4.

Atomfritz said...

@ Laprimavera

Yes, it would be more 320 liters, of course.
I got used to reduce the naked estimate numbers ab bit always, because else I'd feel like exaggerating.

I assumed the diameter/side length of the skimmer surge tank of a bit more than 2 meters according to the proportions in the schematic. If the tank is round-shaped the water surface would be about 3-4 sq. meters, so I picked the lower number and rounded the result a bit to 250 liters/h.

Un-heated water in open air evaporates not very fast.
17 millimeters/h of water evaporation would mean roughly 40 centimeters a day.
This is waaay more than I ever observed to evaporate even on "optimal" conditions: black open water container in the open, heated up by the summer sun, and strong winds with hot air of very low relative humidity.

Under "normal circumstances" I'd suspect a leak even at a water loss of "only" 17mm/h.
So I am really curious what is going on...

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