TOKYO -- The operator of the tsunami-damaged nuclear plant is installing rooftop vents and taking other safety measures at two more nuclear plants to prevent a crisis in case of another severe accident.

Tokyo Electric Power Co. said Tuesday it will add a rooftop vent for seven reactors at Kashiwazaki-Kariwa plant in north-central Japan to prevent hydrogen explosions like what occurred at the Fukushima Dai-ichi plant in mid-March.

While those measures are taken, TEPCO will tentatively store equipment to cut a hole in roofs at Kashiwazaki and the Fukushima Dai-ni plant and take other safety steps at both sites.

The Fukushima Dai-ichi plant had several hydrogen explosions after the March 11 earthquake and tsunami. The explosions had not been anticipated and spewed radiation into the environment.