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News Extra: Fukushima internal radiation levels at highest level since 2011 meltdown

01 March 2017

Radiation levels inside a damaged reactor at the Fukushima Daiichi nuclear power station are at their highest since the plant suffered a triple meltdown almost six years ago. On February 3, the facility’s operator, Tokyo Electric Power (Tepco), said atmospheric readings as high as 530 sieverts an hour had been recorded inside the containment vessel of reactor No 2, one of three affected reactors.

Robot image of possible nuclear fuel debris under No 2 reactor – Image: Tepco
Robot image of possible nuclear fuel debris under No 2 reactor – Image: Tepco

The plant was crippled by an earthquake and tsunami that struck the north-east coast of Japan in March 2011. Tepco said radiation was not leaking outside the reactor.

The extraordinary radiation readings highlight the scale of the task confronting thousands of workers, as pressure builds on Tepco to begin decommissioning the plant – a process that is expected to take about four decades.

The recent reading is far higher than the previous record of 73 sieverts an hour in that part of the reactor. A single dose of one sievert is enough to cause radiation sickness and nausea and a single dose of 10 sieverts would prove fatal within weeks.

The presence of dangerously high radiation will complicate efforts to safely dismantle the plant.

A remote-controlled robot that Tepco intends to send into the No 2 reactor’s containment vessel is designed to withstand exposure to a total of 1,000 sieverts, meaning it would survive for less than two hours before malfunctioning.

Tepco has yet to identify the location and condition of melted fuel in the three most seriously damaged reactors. Removing it safely represents a challenge unprecedented in the history of the nuclear industry.

Quantities of melted fuel are believed to have accumulated at the bottom of the damaged reactors’ containment vessels, but dangerously high radiation has prevented engineers from accurately gauging the state of the fuel deposits.

At the end of January, Tepco released images of dark lumps found beneath reactor No 2 that it believes could be melted uranium fuel rods – the first such discovery since the disaster.

In December, the government said the estimated cost of decommissioning the plant and decontaminating the surrounding area, as well as paying compensation and storing radioactive waste, had risen to 21.5tn yen (£150bn), nearly double an estimate released in 2013.


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