I wanted to update a previous post, New criticality, from Aug. 24. Some sludge data has come in, and there has been a severe spike in Chiba prefecture. Gunma did not have the spike… Chiba is located to the south of the Fukushima Daiichi plant, while Gunma is located to the west of it.
These readings were actually take on August 20. The previous reading at Chiba was on August 6… so the iodine could have been deposited anytime from this date until August 20. This youtube video shows activity at unit 3 on Aug. 7. More activity on Aug. 15, possibly originating from the common spent fuel pool. This picture from August 20 shows more steam, perhaps originating from the sea itself. And the viral picture of the boiling sea, I think was taken on August 27.
On September 2 it was reported that the tanks with the treated water emit 1.0 sieverts/hr of beta radiation due to strontium-90, which causes bone cancer, leukemia, and immune system damage. The graphic of ocean currents indicates that Hawaii is in the path of these radionuclides, which have already arrived. It has not made it to the west coast yet (still a few months), but the contaminated water will make a right turn from there. It will then turn back and contaminate the tropical Pacific, polluting the waters off the Philippines and Taiwan.
UPDATE: Tokyo sludge from the period August 14-30 contained up to 57 Bq/kg of iodine-131.