Wednesday, August 23, 2017

Fukushima Daiichi's Ice Wall Nears Completion and Webcam Update


Some hopeful news out of Fukushima Daiichi:

The (approximately) $300 million dollar ice wall has been reported to be near completion, significantly reducing the inflow of GROUND WATER at the Daiichi site:
Chikako Kawahara (2017, August 23). TEPCO starts to freeze final part of ‘ice wall’ at Fukushima plant. The Asahi Shimbun, http://www.asahi.com/ajw/articles/AJ201708230024.html

Tokyo Electric Power Co. on Aug. 22 began freezing the remaining section of the 1.5-kilometer underground “ice wall” to prevent radioactive water from accumulating at the embattled Fukushima No. 1 nuclear power plant.

The article states that 1,568 pipes were buried at 30 meters under ground level to circulate fluid measuring less than 30 degrees. The article also notes that the final 7-meter section is "expected to take months to freeze" because of fast-flowing groundwater in that location.

You can see a diagram of the ice wall at this Mainichi article:
TEPCO begins extending ice wall to reduce tainted water in Fukushima August 22, 2017 (Mainichi Japan) https://mainichi.jp/english/articles/20170822/p2g/00m/0dm/053000c
The intent is to freeze the surrounding soil.

This containment system is not entirely effective, but TEPCO says it has significantly reduced the inflow of groundwater (there is an underground river beneath the reactors).

A reduction of in-flowing groundwater is very important because the site risks soil liquefaction, which could result in the collapse of spent fuel pools. Fukushima Daiichi has 7 spent fuel pools, one at each of the six reactors and one common spent fuel pool. These pools would release catastrophic amounts of atmospheric radiation if a building collapse interrupted delivery of cooling water to spent fuel.

I imagine that TEPCO has also significantly reduced the amount of highly contaminated water migrating AWAY from the site. Daiichi's melted fuel has been contaminating aquifers and the ocean since the disaster began. Any significant reduction in that contamination is great news.

Still, TEPCO has also been INJECTING hundreds of tons of water everyday to cool melted fuel and that water must be captured and filtered.

TEPCO must continue to inject water into the reactors to reduce the risk of "re-criticality." You can view a video on TEPCO's efforts to prevent "re-criticality" in melted fuel believed to be at the bottom of the pressure vessels here: http://www.tepco.co.jp/en/news/library/archive-e.html?video_uuid=j2l2s3o2&catid=61795

Although re-criticality is not likely to occur, the melted fuel is capable of heating up and releasing radionuclides should cooling be interrupted. See nuclear engineer Arnie Gundersen's account of that process here: https://vimeo.com/22209827

So, although TEPCO's ice wall has improved conditions, TEPCO still faces the daunting task of capturing, storing, and filtering contaminated water. TEPCO cannot filter out tritium from the water it captures and plans on dumping tritiated water into the Pacific Ocean (see my discussion http://majiasblog.blogspot.com/2017/07/tepco-announces-will-dump-radioactive.html).

While the problem of contaminated water will not go away, I am pleased to report that the new cover installed over unit 3 seems to have reduced the visible atmospheric emissions from the plant, even during rainy weather:


The plume near the red-and-white crane has never gone away but it has looked better the last few days than it has for quite some time.



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PAST ANALYSES
Post I: Report Contains Numbers of Fuel Assemblies at Fukushima as of March 2010: http://majiasblog.blogspot.com/2012/05/report-contains-numbers-of-fuel.html

Post II: How Much Radiation Is At Issue: Cesium 137 in Spent Fuel Pool 4: http://majiasblog.blogspot.com/2012/05/how-much-radiation-is-at-issue-cesium.html

Post III: Unanswered Questions http://majiasblog.blogspot.com/2012/05/post-3-unanswered-questions-and-some.html

Evidence of Fukushima Effects http://majiasblog.blogspot.com/2012/10/evidence-on-fukushima-effects.html

Time to Wake Up Overview of Fukushima disaster: Majia's Blog: TIME TO WAKE UP

Assembling information about reactors in Japan Majia's Blog: ASSEMBLING INFORMATION ABOUT JAPAN ...

Summary of info about US fallout SUMMARY OF US BASED RESEARCH ON FUKUSHIMA FALLOUT