Is this number, 1 billion becquerels per hour emission, good? TEPCO's Matsumoto, in the press conference on July 19, avoided the judgment, and said he didn't know, but it was one-2 millionth of what it had been on March 15.
On closer reading of the document, though, I noticed one strange thing about this emission number. TEPCO is talking about the radiation emission measured in cesium (cesium-134 and -137), not in iodine equivalence.
To come up with the iodine-131 equivalence, you have to multiply cesium-134 by 3, and cesium-137 by 40 (according to INES handbook). TEPCO doesn't even give the breakdown of cesium 134 and -137 in its calculation of 1 billion becquerels/hour number. Other nuclides have even higher multiplier: americium-241 is 8,000, plutonium-239 is 10,000.
If half of 1 billion becquerels is cesium-134 and the other half is cesium-137, then in iodine-131 equivalence like in the previous calculations, the emission would be:
(0.5*3)+(0.5*40)=1.5+20=21.5 billion becquerels/hour
Instead of 1 billion becquerels/hour, it would be 21.4 billion becquerels/hour in iodine equivalence, or 516 billion becquerels in one day. In less than 2 days, we would be talking about over 1 terabecquerels.
Why TEPCO would do the calculation in cesium instead of iodine equivalent? To make a ready comparison with the previous emission calculations difficult and to give the impression that the number is low?
And what about iodine? They may not be detecting radioactive iodine at Fukushima I Nuke Plant, but iodine-131 is still being detected in sewage sludge in Tokyo and other parts of Kanto.