The video was taken by two TEPCO employees on April 18, 2012. TEPCO admitted that the shield plug had been open, through which contaminated water (after cooling the Reactor Pressure Vessel) has been leaking into the reactor building.
The workers received 8 millisievert radiation for their 4-minute work. For more on their mission, see my blogpost: http://bit.ly/JHeuK3
For more Fukushima I Nuke Plant accident and radiation contamination in Japan, please visit my blogs:
www.exskf.com (English)
www.exskf-jp.com (Japanese)
