Contaminated water leak at Fukushima Daiichi

Tepco said that at about 8.52am on 7 February a worker from a contracted company found that water was leaking from the vent opening of the second cesium adsorption device installed on the east wall of the high-temperature and high-pressure incinerator building. The vent is for discharging hydrogen generated within the adsorption device. The second cesium adsorption device was currently out of service and was undergoing flushing work with filtered water for valve inspections.

At around 9.10am, the main valve for filtered water was closed, and at around 9.16am, Tepco confirmed that the water had stopped leaking.

The water had leaked onto metal plates located below the leaking pipe.

Tepco estimates that about 5.5 tonnes of water leaked from the pipe, which may contain 22 billion becquerels of radioactive materials, such as caesium and strontium.

"There is a possibility that water leaked into the soil through the gaps between the metal plates under the leakage point," Tepco said, adding that as an emergency measure it will restrict access to the area and will collect the soil in the future.

Although the indicated value of the nearby continuous dust monitor on the premises temporarily rose slightly within the normal fluctuation range, it has now returned to its original value, Tepco noted. In addition, there were no significant changes in the indicated values ​​of the monitoring post, site boundary continuous dust monitor, and drainage channel monitor closest to the leak point.

"The cause of this incident is currently under investigation, but we will continue to appropriately investigate the cause and take measures to prevent recurrence," Tepco said.