Tokyo Electric Power Co. said Monday it has seen a rise in the level of radioactive tritium in seawater within the port at the crippled Fukushima Daiichi nuclear power plant.
A sample collected Friday contained around 1,100 becquerels of tritium per liter, the highest level detected in seawater since the nuclear crisis at the plant commenced in March 2011.
An official of the Nuclear Regulation Authority said groundwater containing radioactive substances may be seeping into the port from the plant site and there is a need to carefully study the matter as the amount of data collected is limited.
According to TEPCO, the sample with the highest tritium concentration was collected near a water intake on the east side of the No. 1 reactor turbine building. The level was more than double that of a sample taken on June 10 in the same area.
The latest announcement was made after TEPCO detected high levels of radioactive tritium and strontium in groundwater from an observation well at the plant.