A five-member panel of the Nuclear Regulation Authority last Wednesday issued a report saying that the D-1 fracture zone of pebbles and sediment running beneath the No. 2 reactor of Japan Atomic Power Co.’s Tsuruga nuclear power plant in Fukui Prefecture is an active fault.

Because constructing important nuclear-related facilities above an active fault is banned, the company will very likely have no other choice than to decommission the reactor.

On the basis of the report, the NRA is expected to decide soon not to allow the restart of the reactor. The NRA should not bow to the pressure that is expected to come from the company and the Liberal Democratic Party. It should make a decision solely relying on convincing scientific findings

The report said that the D-1 fracture zone should be considered an active fault because it cannot be proven that the zone has not moved in the past 130,000 years. It also said there is the possibility that the D-1 zone will move together with the Urazoko fault, lying 200 to 300 meters from the Nos. 1 and 2 reactors, thus affecting facilities constructed above them.

As for two other faults known as G and K, it said that G, K and D-1 are part of the same structure and that it is possible that K has moved in the past 130,000 years. It turned down Japan Atomic Power’s contention that only G is linked with D-1.

The panel held its first meeting in October 2012. Japan Atomic Power was allowed to submit its own data. In March 2013 the panel held a peer review to listen to opinions from experts who did not take part in the on-the-spot geological study of the nuclear power plant site.

It took a fairly long time to issue the report because of the strong resistance put up by Japan Atomic Power.

But it must be remembered that experts expressed a view by the early 1990s that the Urazoko fault is active. Even the now-defunct, infamous Nuclear and Industrial Safety Agency in 2011 expressed suspicions that the D-1 fracture zone is an active fault.

NISA also expressed a suspicion that active faults existed in the compounds of five more nuclear power stations. The NRA should stick to the principle that if the power companies concerned cannot convincingly prove that the faults in question are not active, it will not allow the operation of the nuclear power plants.

Japan Atomic Power owns only the Nos. 1 and 2 reactors at its Tsuruga plant and the No. 2 reactor at its Tokai plant in Ibaraki Prefecture. The NRA decision will likely deliver a great blow to the company, because the Tsuruga No. 2 reactor is more than 40 years old and may not be allowed to be restarted. Local residents strongly oppose the restart of the Tokai No. 2 reactor.

The government should consider ways to economically diversify communities hosting nuclear power plants that are facing closure to make the transition easier for residents.

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