The operator of the damaged Fukushima Daiichi nuclear power plant says the first round of the release into the sea of treated and diluted water has been completed. It says there were no problems with the equipment or procedures.
Tokyo Electric Power Company announced that the first-round operation ended shortly after noon on Monday. The discharge started on August 24.
The utility released about 460 tons of treated water into the ocean per day after diluting it with large quantities of seawater.
TEPCO says that in the first round, it released 7,800 tons of treated water as planned -- the equivalent of 10 full tanks in the plant compound.
Analyses of water samples taken from the sea within 3 kilometers of the plant showed a maximum tritium concentration of 10 becquerels per liter. This is far below 700 becquerels per liter, the level set by the utility for suspending the release.
TEPCO says it will spend about three weeks inspecting the discharge facilities and will start the second round when the preparations are completed.
The utility plans to carry out four rounds of the water discharge during the fiscal year that ends next March. A total of 31,200 tons of water will be released -- the equivalent of about 40 full tanks.
The Fukushima Daiichi plant suffered a triple meltdown in the 2011 earthquake and tsunami. Water used to cool molten fuel has been mixing with rain and groundwater.
The accumulated water is being treated to remove most radioactive substances, but still contains tritium. The treated water is stored in more than 1,000 tanks.
Before releasing the treated water into the sea, the plant's operator dilutes it to reduce tritium levels to about one-seventh of the World Health Organization's guidelines for drinking water.