Radiation levels hit post-meltdown high

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.

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 reactors that experienced a meltdown when the plant was crippled by a huge tsunami that struck the northeast coast of Japan in March 2011.

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, described by some experts as ‘‘unimaginable’’, 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. Five sieverts would kill half those exposed to it within a month, and a single dose of 10 sieverts would prove fatal within weeks.

Tepco also said image analysis had revealed a one-metre-wide hole in metal grating beneath the same reactor’s pressure vessel, probably created by nuclear fuel that had melted.