Nuclear watchdog's green light for aging reactors waters down 40-year rule

The Nuclear Regulation Authority (NRA) has given approval to operating two aging reactors at the Takahama Nuclear Power Plant in Fukui Prefecture beyond 40 years, defying the basic rule of limiting the service life of reactors to four decades.

The No. 1 and 2 reactors at the nuclear plant operated by Kansai Electric Power Co. passed the NRA's safety screenings on April 20, making them the first reactors aged over 40 years that have cleared the new regulatory standards introduced after the 2011 Fukushima nuclear disaster.

Both reactors went online back in the 1970s -- the No. 1 reactor in November 1974 and the No. 2 reactor in November 1975. The 40-year rule, which is mentioned in the revised nuclear reactor regulation law that came into force in 2013, was introduced with the understanding that the operational life of reactors 40 years of age could be extended by up to 20 years just once if the NRA granted permission, but only in exceptional cases.

Kansai Electric Power Co. needed to obtain approval by July 7 for its construction plan elaborating on designs. It also needed approval for extending the operational life of the aging reactors. The NRA, however, agreed to postpone some screening work until after that deadline.

Screenings on the quake resistance of primary cooling systems, including steam generators, are expected to take several years. The NRA's decision to push back those screenings has paved the way for the aging reactors to operate beyond their designated 40-year life.

The NRA says that even if valid data is not obtained during screenings after that deadline, the reactors will be allowed to operate beyond 40 years if the facilities are reinforced and re-examined.

After the NRA issued an initial approval in February for extending the operational life of the Takahama reactors beyond 40 years, it received such public comments as, "Anything could be allowed if screenings can come later." However, the NRA argues that there will be no legal problems with its green light to extend operation of the Takahama reactors.

Meanwhile, Kansai Electric Power Co. has replaced 60 percent of a total of 1,300 kilometers of cables at the No. 1 and 2 reactors with flameproof cables. For the parts where it is difficult to replace cables, the utility has presented measures to prevent the spread of fire, such as wrapping cables with fireproof material. The NRA has approved this alternative solution.

There are four other aging reactors in the country, where the same types of cables as those at the Takahama plant are in place. These old cables were said to be posing "the biggest obstacle in extending the service life of reactors," according to a senior power company official. However, the NRA's latest decision may likely set a precedent for watering down the 40-year rule, which was introduced by the former administration led by the Democratic Party of Japan.