Japan's nuclear watchdog finalized a decision 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.

After soliciting comments from the public, the Nuclear Regulation Authority approved at a regular meeting the revision of safety regulations to make mandatory the installation of systems to circulate water inside reactor containment vessels in the event of serious accidents.

Such systems are designed to prevent temperatures reaching levels that could damage the containment vessels of house boiling water reactors. Such vessels are smaller than those for pressurized water reactors, making it easier for internal temperatures and pressure to rise when conventional cooling systems are damaged.