Not only foreign researchers but also Japanese researchers have raised issues with TEPCO's estimate on the amount of radioactive materials that leaked (on its own, or intentionally) into the Pacific Ocean, TEPCO has said it will recalculate the number. The company hopes to announce the result of the recalculation by the end of this month.
So far, TEPCO's number is 4,700 terabequerels (iodine, cesium).
From Chunichi Shinbun (11/23/2011; don't expect the link to last long on this paper):
Researchers in Japan and abroad have been disputing the number that TEPCO had announced regarding the amount of radioactive materials in the highly contaminated water at Fukushima I Nuclear Power Plant that leaked into the ocean. The leak was discovered in April. TEPCO's number does not include the amount that leaked in March. If the March number were to be added, it could be the worst marine contamination ever. In response to the criticism, TEPCO has started the recalculation, and hopes to announce the result by the end of this month.
In May, TEPCO announced that the amount of radioactive materials that leaked from the water intake of Reactor 2 was 4,700 terabecquerels, total of 3 nuclides including iodine and cesium. It was claimed at that time that the amount was less than 5,200 terabequerels of cesium-137 that leaked from UK's Sellafield nuclear fuel reprocessing plant in 1975.
However, in September, researchers at the Japan Atomic Energy Agency and the Central Research Institute of Electric Power Industry (a TEPCO insider, in a way) published the results of their calculations in academic society meetings, showing the actual amount of the leak could be 3 times as much as what TEPCO had announced, creating a stir.
Then in October, IRSN of France announced their result of calculation which was 27,000 terabecquerels for cesium-137 alone, 28 times as much as what TEPCO had announced.
There are researchers in Japan who cast doubt over the IRSN number as not taking into consideration the dispersion of radioactive cesium in the ocean water.
TEPCO's calculation only counts radioactive materials from April 1 to April 6. The French IRSN thinks the leak started around March 21, when an elevated level of radioactive materials was first observed near the water drain, and lasted till the end of July, though they say the bulk of the leak happened before April 8 (see my post on October 27, 2011).
From my post on April 21, 2011, here are TEPCO's numbers for 6 days of leak:
Iodine-131: 2.8 x 10^15 becquerels (2,800 terabecquerels)
Cesium-134: 9.4 x 10^14 becquerels (940 terabecquerels)
Cesium-137: 9.4 x 10^14 becquerels (940 terabecquerels)
- Total: 4.7 x 10^15 becquerels (4,700 terabecquerels)
JAEA said the amount of cesium-137 was 4 times as much as what TEPCO had announced. (See JAEA's paper, here.)
Whatever criticism that the Japanese researchers may have, the IRSN was the first in the world (as far as I know) to quickly publish the marine contamination simulation. They published the paper that included this simulation in early April, even before the leak of highly contaminated water was taken into account:
I guess the French researchers weren't thinking much about peer-reviewed science magazines, unlike the Japanese counterparts.