(UPDATE) There's now a new leak with HIGH BETA, due to egregious worker error. See my latest post.
This self-explanatory pictorial by Mainichi Shinbun (10/4/2013) shows the kindergarten-level idiocracy (or kindergarteners-would-be-offended level) at TEPCO.
It shows how one of the recent (while I was gone) leaks from the storage tanks at Fukushima I Nuclear Power Plant happened.
5 linked tanks are placed on a slope (30cm x 55m);
Judging by the amount of beta-nuclides in the water stored as reported by Mainichi (580,000Bq/L, or 580Bq/cm3), the tanks contain water that has been treated by SARRY (cesium removed) and RO (desalination);
The tanks were already close to full;
The only water gauge installed was on the tank located at the top of the slope; the water gauge showed there was still some room to pour rainwater that accumulated inside the dam that surrounds the tanks;
Workers started pumping the rain water into the top tank;
There was a gap between the lid on top of the bottom tank and the side panel of the tank; thus
Out went the water slightly mixed with rainwater.
The beta-nuclide content, though much lower than that in the waste water after RO, is still way above the legal limit for discharge (30Bq/L). Part of the leaked water may have reached the ocean, TEPCO admits.
I sense an acute shortage of competent workers at the plant.