Highly radioactive water was found leaking into a cable pit near the Fukushima Daiichi unit 3 water intake.
Further investigation found that the water leaked into the water intake area in front of the nuclear power plant. Water in the pit was found to have I-131 concentrations of 5x10^3 Bq/cm3 and Cs-134 and Cs-137 concentrations of 5x10^4 Bq/cm3. These figures are respectively 125,000, 830,000 and 1.25 million times the legal limits. The radioactivity of samples taken inside and outside the protective silt fences decline by about 500 times, but are still well over legal limits. However, other samples taken on 11 May elsewhere in the intake area, which is blocked off from the breakwater by silt fences, are much lower, by a factor of between 100-200 times.
In any case, workers stuffed fabric wadding into the boreholes, and then filled the hole with concrete. It was confirmed that the leak was stopped eight hours after it was discovered.
Meanwhile, work continues inside the unit 1 reactor building. After installing lights and radiation shielding on 9 May, workers completed calibration of reactor water level gauges, investigation of piping and measured radioactivity levels on 10 May. They found that the reactor building heat exchanger area had the highest dose, of 900 mSv/hr, while the equipment receiving hatch area upper ground floor had a dose rate of between 600-700 mSv/hr. Maximum worker dose was 3 mSv on 9 May, and 9 mSv on 10 May. On 11 May, workers completed calibration of primary containment vessel pressure gauges.