The chances of Japan Atomic Power Co. resuming operations at its Tsuruga nuclear plant in Fukui Prefecture are virtually nil now that an active fault is suspected to run directly beneath one of its reactors, the head of the Nuclear Safety Commission said Thursday.

If the fault is confirmed to be active, Japan Atomic Power would be prevented from restarting the plant's two reactors unless it can prove their safety, Haruki Madarame told reporters.

"But such proof is almost impossible," he added.

On Tuesday, the Nuclear and Industrial Safety Agency and members of its team of experts said a survey indicated that fault fracture zones or soft earth layers lying right under one the plant's reactors, as well as other facilities, may have moved together in the past.

"Needless to say," a reactor built on the outcrop of an active fault tilts when the fault moves, Madarame said.

Both reactors at the Tsuruga power station had already been idled for regular inspections in light of the Fukushima nuclear crisis.

According to the commission, guidelines on earthquake resistance for nuclear plants prohibit the construction of reactors and other key facilities directly above an active fault. Auxiliary faults that move in unison with an active fault are also off-limits.