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Radiation levels at some parts of the stricken Fukushima nuclear plant in Japan are 18 times higher than previously thought, it has emerged.
The news is another setback for the plant’s owners TEPCO, which was forced to increase the radiation alert level at the site on 22 August after 300 tonnes of contaminated water were discovered to have leaked from temporary storage tanks.
Previous tests on water leaking from the tanks holding some 300,000 tonnes of contaminated water showed radiation levels of 230 milliseiverts per hour.
But when the plants owners TEPCO used sensors capable of measuring higher levels of radiation, they found it: four patches contaminated with 1800 miliseiverts per hour.
This amount is high enough to kill a person receiving a full body dose in just a few hours.
The new hotspots are unlikely to pose a risk to workers now they have been identified, but they won’t make clean-up any easier.
“It makes the area a bit like a minefield because they will have to find and work around the hotspots,” said Professor Neil Hyatt, a nuclear materials chemist at the University of Sheffield.
The far greater problem facing TEPCO is how to prevent cooling water that has leaked from meeting groundwater beneath the site and heading out to sea.
The company has admitted cooling water from the reactors may be leaking into groundwater as well as some of the stored water at the surface.
Around 1,000 tanks are thought to be nearly at capacity and several hundred tonnes of partially treated water is being added each day.
The company has plans to build more treatment facilities on the site to remove radioactive elements from the water before it can be discharged into the sea.
However these are now behind schedule, prompting criticism inside Japan of the TEPCO’s ability to manage the crisis.