https://www3.nhk.or.jp/nhkworld/en/news/20230823_08/

TEPCO begins measuring tritium concentrations ahead of treated water release

On Tuesday, the Tokyo Electric Power Company began making preparations for the water's release. That was after the Japanese government announced that it would start discharging the water as early as Thursday. TEPCO finished filling a facility, which is called a discharge vertical shaft, with the treated and diluted water by 8 p.m. on Tuesday. Each ton of treated water has been mixed with about 1,200 tons of sea water. The operator is measuring the concentrations of tritium that the water contains. It plans to confirm on Thursday morning that the water has been diluted to the stated level. TEPCO also intends to check weather and sea conditions.

If there are no problems, it will start releasing the water later in the day. The operator will first dilute 7,800 tons of the treated water with sea water. In the initial stage of the discharge program, it plans to release the diluted water for 17 consecutive days. TEPCO said that it is making preparations to start discharging the water with the utmost vigilance. The plant suffered a triple meltdown following the March 2011 earthquake and tsunami. Water used to cool molten fuel at the plant mixes with rain and groundwater and the volume has been accumulating. The accumulated water is treated to remove most radioactive substances, but it still contains tritium. The government plans to dilute the treated water to reduce the tritium levels to less than one-40th of the nationally-regulated level, before the water is released. That is about one-seventh of the level noted in the World Health Organization's guidelines for drinking water quality.

Source: https://www3.nhk.or.jp/nhkworld/en/news/20230823_08/