The system has the low throughput (37 tonnes/hour instead of 50) on top of the low operating rate (53% in the most recent week). So although not 100% sure, TEPCO thinks it's because of steel pipes clogged up with radioactive sludge. So the company is planning to bypass the particular section and see if the throughput increases.
From Jiji Tsushin via Yahoo Japan (7/23/2011):
福島第1原発事故で、東京電力は23日、高濃度の汚染水処理システムの流量が計画の毎時50トンを大幅に下回る37トン程度に減少している問題を解決する ため、内壁にのり状の汚泥が付着して流路が狭くなっている鋼鉄製配管100～200メートル分をルートから外し、ポリ塩化ビニール製ホースの「バイパス」 を設置することを明らかにした。
The contaminated water treatment system at Fukushima I Nuclear Power Plant has been suffering from the lower than designed throughput of 37 tonnes per hour instead of 50. On July 23, TEPCO disclosed a plan to create a 'bypass" using a PVC hose to divert the flow from going through 100 to 200 meters of steel pipes which are clogged with the sludge.
準備として同日、配管表面の放射線量を測定したところ、毎時50ミリシーベルトと高かったため、作業方法を検討している。
The company measured the radiation on the surface of the steel pipes in preparation of the work, and the radiation was high at 50 millisieverts/hour. TEPCO is considering how to proceed in the high radiation condition.
I think the PVC hose TEPCO is planning to use is an orange-colored hose that has been used throughout the plant, called "Kanaflex", which had an unfortunate rupture the other day.
Since TEPCO hasn't released the "survey map" (contamination map) of the plant since June 24, I don't know which pipe segment that TEPCO is talking about. The June 24 map shows the surface radiation of the pipes that transfer the contaminated water all exceeds 100 millisieverts/hour and as high as 210 millisieverts/hour.
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Unrelated:
Have you seen this video?
> Video of journalists at Futuba hospital March 13, extremely high radiation levels
http://www.youtube.com/watch?v=xuXhVTV4CD0
from http://www.simplyinfo.org
They should not use the plastic pipes. Instead, they ought to "pig" the steel pipes to remove the sludge. Doable, even in spite of the radiation. They need to develop the technology to "pig" these pipes, as this will happen over and over again. The pipes are too long and the speed of the liquid within the pipes is too slow to prevent precipitation. One wonders also, since they are not using a flocculator, whether coagulation and subsequent settling is taking place inside the piping instead of in a settling tank or a flocculation tank as it is supposed to and where it can be dealt with without causing clogging.
"The pipes are too long and the speed of the liquid within the pipes is too slow to prevent precipitation. One wonders also, since they are not using a flocculator, whether coagulation and subsequent settling is taking place inside the piping instead of in a settling tank or a flocculation tank as it is supposed to and where it can be dealt with without causing clogging."
cob job courtesy of TEPCO
"sludge"
water in fuel pools is quite clear, pictures of spraying water from leaks looks clear
Refresh my memory, where exactly is this water being drawn from? the storage barges/tanks? Wouldn't they already be serving as settling tanks, assuming they're not drawing it from the bottom?
My bad. They apparently are using a coagulation/sedimentation tank or similar settling device as shown on the last page here: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110627_01-e.pdf. However, coagulation/sedimentation should be followed by a filtration stage, which seems to be missing (it would become very radioactive and the filtration media would have to be disposed of). It isn't clear where the pipes appear to be plugging up, but I would expect it to be after the coagulation/sedimentation stage and before the reverse osmosis (RO) or desalination unit and treated water storage. Normally, there is extensive filtration done before RO to extend the life of the RO membranes as these eventually clog up and have to be replaced. On page 2 of TEPCO's document, it can be seen that there is a long pipe run from the cesium absorption towers and AREVA system near Reactor 4 and the desalination plant, which is closer to the hillside. When liquid speed is high within a pipe, the so-called Reynolds number is high and the flow inside the pipe is considered to be turbulent (like a swollen river). Turbulent flow inhibits precipitation. When the flow speed is lower, then the flow becomes laminar (like a lazy stream), which permits settling. Pigging a pipe involves sending a rubber (usually) plug through the pipe, which color makes it slightly resemble the animal, hence its name. The pig scrapes and cleans the inside of the pipe, which permits the removal of anything that may be inhibiting flow. See here: http://www.ppsa-online.com/about-pigs.php.
Remember the detection of Cobalt-60 at Daiini?
"In pressurized-water reactors, the most common reactor, hot water circulates at high pressure through the steel pipes, dissolving metal ions from the walls of the pipes. When the water is pumped through the reactor's core, these ions are bombarded by neutrons.
Because the pipes are steel pipes, most of the ions are common iron-isotopes (56 Fe), which don't become radioactive when bombarded by neutrons. But the steel in the pipes is usually alloyed with cobalt. And when this cobalt absorbs neutrons, an instable cobalt-isotope (60 Co) emerges which is radioactive .."
http://www.sciencedaily.com/releases/2009/11/091127123921.htm
Where is it that you go to learn more about water filtration systems in Seattle? I am hoping to find a place soon that can really help me out. Please let me know if you can.
Hello,
Good articles for those who are really in need of seeing and understanding the water treatment system. Would have been better if the plant layout explanation is done well in advance to do.
Nice article anyway did you know hdpe pipes
Nice Blog
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