Tokyo Electric Power Co. said Wednesday there may be signs of fresh nuclear fission in the No. 2 reactor at its quake-damaged Fukushima Daiichi power plant and that it has begun injecting boric acid to control a possible nuclear reaction, Japanese (Kyodo) News Agency reported. There has been no change in the temperature, pressure and radiation levels at the reactor, whose nuclear fuel is believed to have melted when the cooling system failed following the March 11 earthquake and tsunami, the utility known as TEPCO said. Gas samples taken Tuesday from inside the reactor’s containment vessel may contain radioactive xenon, a gas typically generated by nuclear fission, the company said. TEPCO began injecting boric acid early Wednesday into the reactor through a cooling water pipe. The No. 2 reactor had been considered close to achieving a stable condition called cold shutdown with the temperature at the bottom of its casing staying below 100 C.