(4/9/2013 The latest on the leak in the new post)
That's according to TEPCO as of April 6, 2013.
The latest is that there may be additional 47 tonnes of the water leaked (Kyodo News 4/6/2013), and that may be from the in-the-ground storage No.3 (TEPCO, latest email to the press (No.12) on 4/7/2013).
And there is a possibility that instead of 710 billion becquerels of all beta in the water there may be 35 trillion becquerels of all beta.
But first thing first, here's my best effort of summarizing the leak incident.
Yesterday, I watched part of the press conference, I read articles, I read tweets, togetters, and I still didn't clearly get what exactly happened and how - why the water was leaking, how much was leaking, when they found out about it, what was their plan, why the water was stored there in the first place.
At least I sort of figured out the last question. The in-the-ground storage, where the leakage occurred, was not supposed to be used for storing the waste water after the Reverse Osmosis (desalination) treatment with high salt content and high beta nuclides. But the multi-nuclide removal system ALPS couldn't start as planned (September last year; TEPCO is now doing the hot trial run), the water treated by SARRY or Kurion's system (cesium removal) had to be stored somewhere to wait for the treatment by ALPS. So, this water is stored in the tanks made for the post-RO waste water. So, for the post-RO waste water, they started to use in-the-ground storage (there are 7 of them) in early February this year, which was originally meant for post-ALPS treatment water.
For the leak of contaminated water, this is what I have gathered from Jiji, Asahi, NHK, and TEPCO:
TEPCO dug up 7 locations in the Fukushima I Nuke Plant compound to create in-the-ground water storage, and has started to use them on February 1, 2013. Total capacity of these 7 storage locations is 58,000 cubic meters (tonnes).
Construction was carried out by Maeda Construction. They dug up the ground, installed layers of liners, poured concrete to protect and secure the liners, and put in the plastic water storage devices (see the photos below).
The storage location 2 holds 13,000 tonnes of the waste water, with max capacity of 14,000 tonnes. This is where they noticed the leak.
They measured beta nuclides (35 Bq/cm3) during the routine sampling test of water on April 3 in the drain hole on the northeast corner, and on April 5, 5,838 Bq/cm3 of all beta from the leak detection hole on the northeast corner between the bentonite sheet and unwoven fabric sheet/HDPE sheet. That's when TEPCO determined that the water was leaking into the ground.
The storage location 2 is 60 x 52 x 6 meters. TEPCO had confirmed the strength of the protective sheets, but the company did not do a leak test prior to actual use.
TEPCO estimated the amount of leak using the data from the water gauge in the storage, and came up with the number of about 120 tonnes, or slightly under 1 percent of the waste water stored. Calculating from the all beta from the detection hole (5,838 Bq/cm3), TEPCO says 710 billion becquerels of radioactive materials may have leaked.
There is also confusing information as to how full these in-the-ground storage locations already are.
BUT WAIT, THAT MAY BE MUCH, MUCH MORE BECQUERELS.
Why? Because the number TEPCO used to calculate the amount of radioactive materials in the leaked water was from the water taken from the leak detection hole in the bottom protection layer, and NOT the waste water in the storage.
So, how many becquerels of all beta does the waste water in the storage have?
Asahi Shinbun article which I consulted did say "290,000 Bq/cm3 strontium" in the water in the storage, and that's the number reported by TEPCO on March 6, 2013 as the amount of all beta in the waste water after the Reverse Osmosis treatment. Again, that is the waste water being stored in the holes in the ground with several layers of sheets...
Using that number, 290,000 Bq/cm3, instead of 5,838 Bq/cm3, there could be nearly 35 trillion becquerels of all beta in 120 tonnes of the leaked waste water.
In the press conference on April 6, TEPCO didn't disclose the radioactivity of the stored waste water, and none of the reporters at the press conference seems to have asked about it.
The quality of information coming out of TEPCO's press conference has markedly gone downhill in the past few months.
In the first few weeks of the nuclear accident in 2011 when one of TEPCO's managers who gave press conference was Vice President Muto, very few reporters understood what Mr. Muto was saying. Not because Mr. Muto, who is a nuclear engineer, was obfuscating but because reporters didn't know much about nuclear reactors/plants at all. They didn't know what to ask, they didn't comprehend the answers they got. Mr. Muto himself didn't seem to understand that the (mostly) young reporters didn't have a clue of what he was talking about.
Then came Mr. Matsumoto, TEPCO's PR spokesman, sometime in late March-early April time frame. The reporters were getting up to speed, and Mr. Matsumoto, after initial bureaucratic awkwardness, turned out to be OK, giving out technical information in more or less straight-forward manner. I was impressed when he explained with a straight face, no pretense, in the press conference how his company was trying to stop the leak of highly contaminated water (probably from Reactor 2 turbine building) in early April of 2011 with baby diaper polymers and shredded newspaper, using onsen bath salts as tracer.
Then came Mr. Ono, new spokesman, starting this year. Suddenly, TEPCO's press conference has become muddled again. Mr. Ono, whose manner of speech is not clear to begin with, has a convoluted and confusing way of explaining things to the reporters who are by now quite knowledgeable about things nuclear and particularly about Fukushima I Nuke Plant. I've seen them often lose patience with Mr. Ono, who often becomes defensive. He does not seem to know well enough of the subject matter (nuclear, and this plant in particular) to be able to speak clearly. The reporters, in turn, reacting to this muddled-through way of communication, have reverted back to the initial state of not knowing what to ask.
People say "It's the company, TEPCO". I'm inclined to say it's this particular spokesman who is wiping out what credibility TEPCO had accumulated in the past 2 years by trying to be straight-forward in disclosing information.