Technicians at the stricken Fukushima nuclear plant in Japan have begun injecting nitrogen gas into into one of its six reactors.
It is hoped the inert gas will prevent an explosive build up of hydrogen gas in the No 1 reactor.
The Fukushima Daiichi plant was badly damaged after a 9.0-magnitude earthquake triggered a tsunami that devastated much of the north-east coast of Japan on 11 March.
Workers are injecting nitrogen into the containment vessel of the No 1 reactor where levels of hydrogen have been rising.
Hydrogen when mixed with oxygen can become explosive, but nitrogen is an inert gas which should purge the reactor of a potentially dangerous combination, the BBC reports.
The procedure may be repeated in other reactors if deemed necessary.
Explosions rocked the Fukushima plant shortly after the quake and tsunami hit and workers have been struggling ever since to stabilise the plant's nuclear reactors.