The radioactive gas xenon, which is often the byproduct of unexpected nuclear fission, was detected at the Fukushima Daiichi plant during tests. Officials were today injecting boric acid as an emergency precautionary measure to stem any accidental chain reactions which could result in further radiation leakages. The discovery of such a gas is likely to be regarded as an unwelcome setback among operators who are keen to achieve cold shutdown by the end of the year. Officials both from Tokyo Electric Power Co, which operates the plant, and from Japan Atomic Energy Agency, were today (WED) reexamining the gases to double check their identity. The discovery of the gases coincided with the controversial reopening of a nuclear reactor in southern Japan - the first to be put back online since the March 11 Fukushima disaster. The Genkai plant in Kyushu was restarted despite strong public opposition, after officials confirmed it had passed safety tests following its closure over technical problems last month. Anti-nuclear public sentiment has been growing across Japan since the nation was caught up in the on-going atomic crisis, the world's worst nuclear disaster since Chernobyl in 1986. Around 40 of Japan's 54 reactors currently remain offline for testing, with the Genkai plant widely regarded as a symbolic first step in restarting dozens more across the country.