February 24, 2015
Tepco admits that it failed to disclose a leak since last year April 2014.
Unit 2′s roof and downspouts have been draining directly out to sea since the disaster. Water found on unit 2′s roofs was highly radioactive with 52,000 bq/liter on one roof
TEPCO did attempt to manage this by throwing down bags of zeolite at the downspout entrance and again at the drainage canal exits. Plans submitted to IRID for a drainage canal filter system called for a much more sophisticated system that would have forced any water leaving these drainage canals through a series of filters.
Zeolite bags were also placed around the entrance to the downspouts on the building roofs. Radiation readings in the downspout water was significantly lower than the water on the roof. A filter that forces all outgoing water through the filter media would have at least worked to more effectively filter water.
Source: Tepco
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2015/images/handouts_150224_01-e.pdf
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