Tokyo Electric Power Co. detected signs of possible nuclear fission at its crippled Fukushima atomic power plant in northern Japan, raising the risk of more radiation leaks.

The company, known as Tepco, began spraying boric acid on the No. 2 reactor at 2:48 a.m. Japan time in an attempt to prevent accidental chain reactions. Tepco said it may have found xenon, which is associated with nuclear fission, while examining gases taken from the reactor, according to an e-mailed statement today.

The amount of detected xenon is “very small” and results of the utility’s analysis may be wrong, said Hiroyuki Usami, a spokesman for Tepco. No significant changes in temperatures and pressures of the reactor and radiation levels at the site have been detected, he said.

The discovery comes almost eight months after the March 11 earthquake and tsunami wrecked the Fukushima Dai-Ichi plant, causing a loss of cooling and the meltdowns of three reactors. The incident, the worst nuclear disaster since Chernobyl in 1986, was responsible for the biggest discharge of radioactive material into the ocean in history, according to a study from a French nuclear safety institute.

Nuclear fission, even if it has occurred, is unlikely to be sustained as Tepco started injecting boric acid into the reactor, said Tadashi Narabayashi, a former reactor safety researcher at Toshiba Corp. and now a nuclear engineering professor at Hokkaido University.

Tepco and the government have said they are on track to bring the damaged reactors into a safe state known as cold shutdown by the end of the year. The company has been mixing boron, an element that absorbs neutrons and hinders nuclear fission, with cooling water in the reactors to prevent accidental chain reactions.

(Source: Bloomberg)