Radioactivity worries at Japan nuke plant

TOKYO -- Radioactive particles associated with nuclear fission have been detected at the tsunami-damaged atomic power plant, Japanese officials said yesterday, suggesting one of its reactors could have a new problem.

The fresh concerns at the Fukushima Dai-ichi nuclear facility came as a reactor in southern Japan was restarted and brought back online, marking a first since the March 11 disaster created an outcry over the safety of Japan's nuclear power sites.

Utility officials said gas from inside the Fukushima plant's No. 2 reactor indicated the presence of radioactive xenon, which could be the byproduct of unexpected nuclear fission. Boric acid was injected through a cooling pipe as a precaution because it can counteract nuclear reactions.

Tokyo Electric Power Co. said there was no rise in the reactor's temperature or pressure. The company said the radioactive materials had not reached the point when nuclear reactions are self-sustaining and the detection of the xenon would have no major impact on workers' efforts to keep the reactor cool and stable.

Hiroyuki Imari, a spokesman with the Nuclear Industrial Safety Agency, said the detection of the gas was not believed to indicate a major problem, but its cause was being investigated.

In a first since the Fukushima disaster, a nuclear reactor in southern Japan has resumed operation after a monthlong shutdown for a technical problem.

The Kyushu Electric Power Co. said No. 4 reactor at the Genkai nuclear power plant restarted late Tuesday and was generating electricity yesterday. It automatically shut down Oct. 4 following an abnormality in a steam condenser. -- AP