Something is going wrong. TEPCO has started to use fresh water taken from the river to cool the reactors, because the treated water that it has been using is running low.
From Yomiuri Shinbun (10:23PM JST 7/15/2011):
TEPCO announced on July 15 that the company started to use the fresh water from outside source to supplement the treated water it has been using to cool the reactors for two weeks. The contaminated water treatment system at Fukushima I Nuclear Power Plant is not functioning well.
If the outside water is used, that will increase the amount of contaminated water. TEPCO is trying to identify the cause of the problem.
The system can process 50 tonnes of water per hour. During the one week that ended on July 12, however, the rate was 37 tonnes per hour. TEPCO stopped the system at 5:14AM on July 15 to expel the air out of the pipes and restarted the system at 2:21PM, but the operating rate still remains at 39 tonnes per hour.
As the result, the amount of treated water in the storage tank has dropped to 35% of the full capacity, so TEPCO replenished the tank with 570 tonnes of river water to bring it to 63% capacity. If outside water is added, the contaminated water will increase.
63 minus 35 equals 28.
570 tonnes equal 28% of the capacity.
So the tank holds 2,035 tonnes.
Hmmm, the number doesn't match up with the information on TEPCO's drawing, which shows the storage tank to have the capacity of 5,000 tonnes and the buffer tank that can mix river water with contaminated water if needed has only 1,000 tonnes capacity. There is no tank with 2,000 tonnes capacity in the drawing...