On October 24, TEPCO quietly released the analysis of the water being sprayed in the plant compound, supposedly for fire and dust suppression.
The water comes from the basements of Reactors 5 and 6, and is treated, apparently, by the system that uses reverse osmosis. TEPCO assures us the water is safer than the seawater cleared for ocean bathing, though it does exceed the WHO standard.
One notable nuclide that does remain after the RO treatment is tritium (H3). From TEPCO's handout for the press (10/24/2011):
In fact, the treated water is so safe that a cabinet officer of the Noda administration has vowed to drink up the water (link in Japanese) to appeal safety. Seriously.
Apparently, TEPCO at Fuku-I plant is getting ready to shoot the video of water collection for the officer, according to the tweet from a plant worker. The worker is a bit cross with this performance by the politician and TEPCO's willingness to accommodate him.
I hope this officer knows that tritium is a beta emitter, and not really recommended for ingestion.