Puddles of water with extremely high radiation levels have been found near water storage tanks on the premises of the crippled Fukushima No. 1 nuclear power plant, nuclear regulators and plant operator Tokyo Electric Power Co. said Monday.
The radiation level, measured around 50 cm above the toxic water, stood at about 100 millisieverts per hour, Tepco said, while acknowledging that the water likely came from the tanks. It is possible that around 120 liters of water has so far leaked out.
Tepco denied that toxic water had flowed into the Pacific Ocean, but the Nuclear Regulation Authority ordered the utility to study the possibility that the toxic water had escaped into the sea through nearby drains.
The NRA released a preliminary assessment of a level 1 incident on an eight-point international scale, defined as an “anomaly.”
A low barrier around the tanks is meant to block water from escaping when a leak occurs, but drain valves attached to the barrier may have been left open, allowing water to flow outside the barrier.
A Tepco employee found water leaking from a valve at about 10 a.m. Monday while patrolling the site. One of the puddles outside the barrier was around 3 square meters in size and about 1 cm deep.
A massive amount of radioactive water is accumulating at the plant as a result of continuing water injections into the Nos. 1, 2 and 3 reactors that suffered meltdowns in the midst of the March 11, 2011, nuclear crisis, which was triggered by a huge earthquake and tsunami.
Tepco also said the same day that it had found two workers contaminated with up to 13 becquerels per 1 sq. cm of radioactive material when they were waiting for a bus to leave the site. The contamination was detected on their heads.
Airborne radioactive substances where the workers were waiting were around eight times the alert level. The two workers did not suffer internal exposure.
A similar incident, involving 10 people waiting for a bus, occurred a week earlier. Their contamination was up to 19 becquerels per square cm, lower than the state limit of 40 becquerels.