Several estimates have been published, but seem to underestimate the figures significantly, by not counting all the isotopes, by not counting the fallout from the air, and by counting only the water leaks from the plant that TEPCO has acknowledged. Even if there have been no further leaks, it seems about 100,000 TBq of radioactive iodine and cesium entered the marine environment.
9400 Terabequerels: June 17 Japan Atomic Energy Agency estimate of June 17 This assumed that half the air release of Cs-137 (8,450 TBq) was deposited in the ocean, and added TEPCO’s estimate of 940 TBq of I-131 and two cesiums from only one water leak (assumed that no water leaked to the sea after April 1). Note that this estimate does not include any air deposition of I-131, Cs-134 or any other isotope.
4700 TBq: June 18: Japanese govt report to IAEA (section VI 2), repeating TEPCO’s estimate of water releases only, as air releases were mentioned elsewhere.
100,000 TBq: It seems to me that a case can be made that the figure is much higher. If accept JAEA’s assumption that half the air releases landed in the sea, and that NISA’s June 6 estimates of those releases are correct (see below), you get air deposition in the sea of
- 80,000 TBq I-131 air deposition
- 9,000 TBq Cs-134 air deposition
- 7,500 TBq Cs- 137 air deposition
- 4,700 TBq from known water leaks
- 101,000 TBq Total