Tokyo: A nuclear reactor in southern Japan was to begin producing electricity again on Wednesday, its operator company said, in the first restart of a stalled atomic power plant since the Fukushima disaster.

Operations at the reactor began late on Tuesday, Kyushu Electric Power said, less than a month after the facility automatically shut down following a safety alert.

An anti-nuclear rally in Fukushima city on 30 October2011. AFP

The reactor at the Genkai nuclear plant, in southern Saga prefecture, is the first to resume operations since the massive earthquake and tsunami of 11 March sparked an atomic emergency at the Fukushima Daiichi plant.

The restart will come as a boost to Japan’s beleaguered nuclear industry, which is battling a sceptical public largely unwilling to allow operations to restart at the dozens of stalled reactors nationwide.

Kyushu Electric officials, however, say the situation at Genkai is different from that of other suspended reactors, which are required to undergo government-mandated stress tests.

The reactor was halted after an “abnormality" in its steam condensing unit emerged on 4 October , Kyodo news reported, adding that industry minister Yukio Edano, who oversees the sector, had attributed the fault to “human error".

Kyushu Electric is to stop the reactor again in December for scheduled safety checks, the agency said.

Edano said on Tuesday the final decision on restarting the reactor rested with Kyushu Electric because the country’s nuclear regulator had found its procedures to be sound, but he urged the company to consult the local community.

Reactors halted for checks must pass stress tests before they are allowed to resume operation, but local authorities have the power to veto the restarts.

Public officials in Saga gave their assent to the restart there after the nuclear safety agency gave its stamp of approval.

Saga governor Yasushi Furukawa told reporters: “If the state made the judgment after a full examination, we’ll accept it," Kyodo reported.

On Wednesday Tokyo Electric Power said scientists at Fukushima had detected the possible presence of xenon 133 and xenon 135, byproducts of a nuclear reaction, indicating fission had re-started at the stricken plant.

Tepco said it had begun injecting water and boric acid into Reactor No. 2 in a bid to stem the resumed fission.

A company spokesman said there was no fresh danger at the plant, as the reactor’s temperature and pressure, as well as radiation levels at monitoring posts, showed no substantial changes.

Before the disaster at Fukushima, Japan relied on nuclear power for around a third of its electricity, and has since had to ramp up its imports of thermal fuels to plug the supply gap as the number of active reactors dwindles.

A nationwide campaign to save energy over the summer is to continue over the winter, amid warnings of a shortfall that could be particularly acute in western Japan, which is more heavily dependent on nuclear generation.