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:

東京電力からのご連絡
Notice from TEPCO
────────────────────────────────────
報道関係各位
To the Press

・本メールは、事前に「深夜・早朝における連絡先」の登録のお申し込みをいただいた方にお知らせしています。
This mail is sent to those who have registered for "Notification in late night and early morning".

・本日(1月1日)午後5時30分頃、免震重要棟でプラントデータの確認を行っていた当社社員が4号機使用済燃料プールのスキマサージタンク(※)の水位が比較的早い速度で低下していることを確認しました。

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.

・スキマサージタンクの水位については、自然蒸発などにより低下しますが、これまでの運転実績において、3時間で50mm程度(1時間あたり約17mm)の低下であったものが、本日午後2時~午後5時までの3時間で約240mm程度(1時間あたり約80mm程度)の低下が確認されました。

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).

・現在、漏えいを想定した現場確認を行っているところでありますが、4号機の使用済燃料プール循環冷却システムが設置されている廃棄物処理建屋1階ならびに原子炉建屋外廻りにおいて漏えいは確認されておりません。原子炉建屋内の配管の接続部の健全性確認など、現場調査を引き続き行い、原因調査を行ってまいります。

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.

・本日午後5時現在の使用済燃料プール水の温度は23℃であり、現在も同プールの冷却を継続しており、使用済燃料プール自体の水位に変動はありません。今後、準備が整い次第、スキマサージタンクの水張りを実施し、水位を監視してまいります。

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.

・本メールには返信できませんのでご了承ください。
Do not reply to this mail.

                                  以 上


(※)使用済燃料プールからオーバーフローした水を受けるため設置されているタンク。使用済燃料プールの水は、通常、燃料集合体の冷却および水の不純物を取り除くため、スキマサージタンクへオーバーフローさせ、熱交換器およびフィルタを通した後、再び使用済燃料プールへ戻している。

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.

3 comments:

Atomfritz said...

Look at this picture to see the location of the skimmer surge tank: http://i281.photobucket.com/albums/kk204/j_t_frimenko/SkimmerSurgeTank.png

Facts:
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...

Post a Comment