Japan's nuclear watchdog decided Wednesday to require operators of boiling water reactors — the same type as those at the crisis-hit Fukushima No. 1 nuclear complex — to install new emergency cooling systems that would activate in the event of a serious accident.

The Nuclear Regulation Authority approved at a regular meeting the revision of safety regulations to make mandatory the installation of cooling systems to circulate water inside reactor containers.

Such systems are designed to prevent temperature rises that could damage containers. Boiling water reactors are housed in containers that are smaller than those for pressurized water reactors, making it easier for internal temperatures and pressure to rise when conventional cooling systems are damaged.