The thinning ranks of men struggling to tame Japan’s nuclear emergency are invoking the spirit of the samurai as they ignore personal radiation limits in their battle to avert disaster.

Some are so determined to push on with a task they see as vital to saving Japan they are leaving their dosimetres at home so bosses do not know the true level of their exposure to radiation at the crippled plant.

As Japan declared the Fukushima Daiichi disaster a level seven emergency – the worst on an international scale – engineer Hiroyuki Kohno was heading back into the leaking plant, fully aware that one day it could make him very ill.

“My boss phoned me three days ago. He told me: ‘The situation over there is much worse than what the media are reporting. It is beyond our imagination. But, will you still come?’,” he said.

“It was just that. We didn’t need to say anything more because we both knew that the situation is really dreadful,” the soft-spoken Mr Kohno said, leaving lengthy pauses between his sentences.

The two did not discuss financial reward or compensation for the possible long-term health risks, which could include cancer.

“It’s not even about money anymore,” he said.

Fukushima Daiichi was swamped by the ferocious tsunami that hit Japan’s northeast coast after the 9.0-magnitude earthquake of March 11.

The tsunami left almost 13,500 dead and 15,000 missing. Tens of thousands more were made homeless.

Reactor cooling systems were knocked out, allowing their atomic cores to heat up uncontrollably and sparking a nuclear emergency now classified as on a par with the Chernobyl disaster a quarter-century ago.

Subcontractor Mr Kohno said he will be assigned to the plant’s headquarters located in a quake-resistant tower, where he will be exposed to the same amount of radiation every hour that ordinary people experience in a whole year.

Emergency work ranges from removing massive amounts of radioactive water to clearing contaminated rubble, measuring radiation levels and hooking up power cables to kick-start cooling.

Fukishima Daiichi could be the last posting for Mr Kohno in a professional life spent entirely in the nuclear industry.

The 44-year-old has already done one long stint at the plant and is going back to Japan’s nuclear ground zero even as a friend of his reaches the outer limits of lifetime radiation exposure.

His friend, an employee of operator Tokyo Electric Power Co (Tepco), says his dosimetre is showing “close to” 250 millisieverts – 250 times what an ordinary person is exposed to in a year.

Exceeding that level in the course of work is illegal in Japan and a plant worker who reaches the limit will be relieved of his duties for life.

The level is five times that allowed for plant workers in the US and 12 times that for France.

“My friend told me: ‘I can’t do this anymore. I’ve reached my limit. I’m so sorry you have to come, but I can’t do any more’,” Mr Kohno said.

His friend talks of colleagues who have taken off their dosimetres, the machines that measure exposure to radiation and which will alert officials when cumulative levels are breached.

“They’re doing it out of responsibility. And because there are fewer people who want to return after working at such a frightening place,” said Mr Kohno.

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