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Japan's Nuclear Regulation Authority to require new cooling system for boiling water reactors

Kyodo

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.

Due to the rule change, emergency cooling systems will need to be installed for a number of boiling water reactors across the country that have been undergoing checks required to resume operations.

Tohoku Electric Power Co.’s Higashidori nuclear power plant in Aomori Prefecture, the Onagawa complex in Miyagi Prefecture and Chubu Electric Power Co.’s Hamaoka plant in Shizuoka Prefecture are among those that will be affected.

The new cooling systems will be activated if severe accidents occur at nuclear plants, with water accumulated inside reactor containment vessels to be circulated outside for cooling before being returned.

If the reactor still cannot be brought under control, the operator will be allowed to release steam through a filtered venting system. Under safety requirements implemented following the 2011 Fukushima nuclear crisis, reactors must be equipped with such systems.

While several pressurized water reactors have cleared these stricter safety standards, two boiling water reactors at Tokyo Electric Power Company Holdings Inc.’s Kashiwazaki-Kariwa power station in Niigata Prefecture became the first such reactors to be approved, in October.

Tokyo Electric, which runs the Fukushima complex, had already planned to install the new emergency cooling system for the reactors 6 and 7 at the Kashiwazaki-Kariwa plant.