Tokyo Electric Power Co Inc said today it had found levels of radioactive material in groundwater had risen sharply at a damaged Japanese nuclear power plant.
A survey showed the levels of caesium-134 in groundwater at an observation well had jumped to 9,000 becquerels per litre on Monday, from 99 per litre on Friday, the operator of the Fukushima Daiichi plant said.
Tokyo Electric also said the levels of caesium-137 had also increased to 18,000 becquerels per litre on Monday, from 210 per litre on Friday.
The observation well was set up in December near the turbine building of reactor 2 in the complex 230 kilometres north-east of Tokyo.
The operator has yet to find that the groundwater at the well, located 27 metres from the Pacific Ocean, has flowed into the sea, said Hisashi Otsuka, a Tokyo Electric spokesman.
The plant suffered core meltdowns after an earthquake and tsunami in March 2011.