Fukushima updates - slow build up of hydrogen gas matches grim sense of being in the eye of the storm - with the sense you're soon to see the effects of the other eye wall of the storm.....

http://ex-skf.blogspot.com/2012/05/how-fukushimas-spent-fuel-pool-cooling.html

FRIDAY, MAY 4, 2012

How #Fukushima's Spent Fuel Pool Cooling Works

(or is supposed to work, considering numerous leaks...)

Spent Fuel Pools of Fukushima I Nuclear Power Plant, particularly that of Reactor 4, continue to be in the news inside and outside Japan.

Dr. Hiroaki Koide of Kyoto University spoke in New York on May 3 and held a press conference on the status of Fukushima I Nuclear Power Plant and radiation contamination in Japan as he sees it.

He said about the Reactor 4 Spent Fuel Pool (I'm reading off from the Japanese transcript), 

補強工事というものを施した、ということになっています。

So-called reinforcement work was done [on Reactor 4 SFP]. (My translation, not the translation at the press conference)

Then, one of my blog readers sent me a link to the post that has an audio clip of a radio program, in which nuclear expert Arnie Gundersen seems to be saying that TEPCO has been pumping water into the Reactor 4 Spent Fuel Pool from the top, the water drains to the basement, and TEPCO is pumping the water from the basement back into the SFP.

That's news to me, but then I haven't carefully checked how the cooling of the Spent Fuel Pools at Fukushima I Nuclear Power Plant has been done after TEPCO installed the temporary heat exchangers. So I decided to look for info, and here's what I've found.Asahi Shinbun had an article on the temporary cooling systems for the SFPs back in June last year, and here's their simplified diagram of the system (missing the Skimmer Surge Tank):

Here's what TEPCO released on July 9, 2011 after they tested the pipes after installing the heat exchanger and the air cooling system (secondary cooling) for Reactor 4 SFP:

Here's TEPCO's diagram of the same system, released on April 16 this year after the Reactor 4 SFP cooling system stopped due to a leak (the information was released only in Japanese; I labeled "Heat Exchanger"):

As far as I can tell, it is basically a closed system though leaks have happened. The excess water from the Spent Fuel Pool goes to the Skimmer Surge Tank, which then is then goes through the heat exchanger to remove heat (0.9MW in the Reactor 4 SFP, as per TEPCO's press release above). The water is then pumped back into the SFP.

Back in February when the water level of the Reactor 4's Skimmer Surge Tank was dropping more than usual, TEPCO injected the water from the bottom of the Reactor Pressure Vessel (which is filled with water). That water went from the RPV to the Reactor Well to the SFP to the Skimmer Surge Tank.

Contaminated water in the turbine building basements in Reactors 1, 2, 3 and 4 gets treated through cesium absorption towers (Kurion or SARRY) and desalination systems, then pumped back into the Pressure Vessels but not to any of the Spent Fuel Pools.

and....

http://fukushima-diary.com/2012/05/hydrogen-concentration-increasing/

Hydrogen concentration increasing

Posted by Mochizuki on May 4th, 2012 · No Comments

Following up this article..Air pressure is increasing in container vessel of reactor 2

Since Tepco increased air exhausting amount from 17 m3/h to 38 m3/h on 4/24/2012, hydrogen concentration of reactor2 has been increasing.

and....

http://www.psr.org/news-events/events/press-conference-on-fukushima.html

http://enenews.com/japan-nuclear-professor-press-conference-im-worried-very-about-reinforcement-4-fuel-pool-praying-wont-be-large-aftershocks-video

Press Conference on Fukushima Daiichi Disaster
May 4, 2012 10:00 am ET

Speaker: Hiroaki Koide, Nuclear Reactor Specialist and Assistant Professor at Kyoto University Research Reactor Institute.

Rush Transcript Excerpt

Koide: The story is that Tepco is carrying out reinforcement project to prevent spent fuel pool from falling apart.

However, the status of the work site is so contaminated that it is not a place where workers can work at ease.

I’m worried very much about how far they’ve been able to properly complete that construction.

I’m also praying that there wont be a number of large aftershocks.

and.....

http://enenews.com/nuclear-expert-on-no-4-fuel-pool-theyre-pumping-water-in-and-its-draining-out-into-basement-they-suck-it-out-of-basement-and-put-it-back-in-at-top-there-is-no-containment-video

Interview with Fairewinds Chief Nuclear Engineer Arnie Gundersen
WIBC’s Denny Smith (Indianapolis)
April 24, 2012

At ~1:00:30 in

Gundersen: There is no containment, the containment is destroyed… they’re pumping [water] in and it’s draining out into the basement and they suck it out of the basement and they put it back in at the top.