The power outage that shut down spent nuclear fuel cooling systems and other facilities for 29 hours last week at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant underlines the fact that conditions there remain precarious two years after the massive quake and tsunami on March 11, 2011, triggered triple meltdowns.

It also shows that Tepco failed to learn important lessons from the catastrophe at the plant — that all-out efforts must be made to prevent power outages that disrupt cooling functions at the plant. This incident will deepen people's distrust of Tepco.

If the power supply had not been restored in time, a meltdown of spent nuclear fuel could have occurred, resulting in a release of a massive amount of radioactive substances into the environment. Tepco and the government should not play down the gravity of this accident.