Last week the plant's operator reported radioactive water had leaked from a storage tank into the ground. It now says readings taken near the leaking tank on Saturday showed radiation was high enough to prove lethal within four hours of exposure…. The Tokyo Electric Power Company (Tepco) had originally said the radiation emitted by the leaking water was around 100 millisieverts an hour. However, the company said the equipment used to make that recording could only read measurements of up to 100 millisieverts…. The new reading will have direct implications for radiation doses received by workers who spent several days trying to stop the leak last week, the BBC's Rupert Wingfield-Hayes reports from Tokyo.