says the government corporation Japan Atomic Energy Agency, 5 months after the leak of highly contaminated water was first discovered (in April) at the water intake for Reactor 2 at Fukushima I Nuclear Power Plant.
So, instead of 4,700 terabecquerels of radioactive iodine and cesium as TEPCO announced back in May, JAEA says it was 15,000 terabecquerels that leaked into the Pacific Ocean, and that it could have been leaking since March 21, not from April 1.
From Yomiuri Shinbun (9/9/2011):
Researchers at Japan Atomic Energy Agency (JAEA) led by Takuya Kobayashi has come up with the estimate that puts the total amount of radioactive materials leaked into the ocean from Fukushima I Nuclear Power Plant at 15,000 terabecquerels. Their estimate includes the radioactive materials in the contaminated water and in the air that fell in the ocean.
The JAEA estimate is three times as much as the estimate by TEPCO. It will be announced during the Atomic Energy Society of Japan conference set to begin in Kitakyushu City from September 19.
TEPCO limited the time period of the contaminated water leak from April 1 to 6, and estimated the amount of iodine-131, cesium-134 and cesium-137 to be 4,700 terabequerels.
Kobayashi et al calculated the amount of the leaked water from March 21 to April 30, based on the density of radioactive materials at the water intake of the plant. March 21 was when radioactive materials were detected in seawater for the first time. They also did the simulation of how the radioactive materials spread in the ocean based on their estimate, and confirmed that it matched the observed data in the ocean near the plant. The estimate does not include cesium-134, so the total amount of radioactive materials would be higher.
So the researchers concluded the leak may have been ongoing since March 21, based on the density of radioactive materials at the water intake that TEPCO was announcing. Duh. And TEPCO insisted that the leak started on April 1 or not so long before a worker noticed for the first time, and no one in the media questioned at that time. No one is saying anything now either about this extremely contaminated water that may have been leaking for 10 days before TEPCO even noticed.
(Note to self: Think.)
Asahi Shinbun has different details:
The main factor that pushed the number up was the radioactive materials in the air that fell into the ocean;
Iodine-131 alone accounts for 11,400 terabecquerels, and cesium-137 for 3,600 terabecquerels.
Well I sure hope this number for cesium-137 is "iodine-131 equivalent". Otherwise the total amount of radioactive materials leaked would be approaching INES Level 7 on its own.
These government researchers are announcing their precious studies left and right, now that their papers have been peer-reviewed and set to be published.