The operator of the Fukushima Daiichi nuclear plant says the groundwater level fell below the level of contaminated water inside the No.1 reactor building in May. This means that radioactive water may have leaked from the building.
Officials with the Tokyo Electric Power Company say there were errors in the settings of 6 indicators installed since April to monitor the groundwater levels around the No.1 to No.4 reactor buildings. They say the actual levels were about 70 centimeters lower than the readings taken with the equipment.
Contaminated water could leak out if groundwater levels are lower than the level of contaminated water inside a reactor building.
The officials say the groundwater level of a well outside the No.1 reactor building was up to 2 centimeters lower than the contaminated water level, and this occurred at least 8 times between May 17th and the 21st.
They say they cannot tell how long this situation lasted, and are continuing their investigation.
The utility says there are no reports of any irregularities in the density of radioactive substances in the groundwater around the reactor buildings.