According to the Japanese government rules, nuclear reactors cannot be installed on a fault line - a line where two or more plates that form the earth's crust meet - if it is classified as an “active fault”. An active fault is one which has shifted in the last 130,000 years.
"There is no way we can carry out safety assessments for a re-start," the chairman of Japan's Nuclear Regulation Authority (NRA), Shunichi Tanaka, said Monday, after receiving a report that stated the No.2 reactor of the plant sits on a active fault, Reuters has reported.
A panel of seismologists appointed by the NRA is reviewing the nuclear installations in the country after the Fukushima disaster last year, in which atomic rods meltdown triggered by an earthquake, resulted in radiation leaks.
Tsuruga plant, located on the Sea of Japan coast, is the second nuclear complex that NRA is studying as a part of its review. It had first surveyed Kansai Electric Power Co.'s Oi power station in the same prefecture, Japan Times has reported.
NRA findings reveal that a fault line extending from below the reactor was assessed to have moved in the past, in tandem with another fault located nearby, Reuters has stated. Previous studies, have also confirmed the presence of Urazoko fault – an active fault that lies 250 meters away from the reactor buildings that could trigger smaller faults, which may extend up to the reactors, if the Urazoko shifts. In 2008, Japan Atomic Power confirmed that the Urazoko fault was active.
Any such movement if it were to occur has the potential to trigger a major nuclear disaster.
Tsuruga plant's No.1 unit with 1,357-megawatt capacity - the oldest of Japan's 50 commercial reactors - started its operations in 1970 while the No.2 reactor with 1,160-megawatt capacity started its operations in 1987.
After the Fukushima disaster, all but two nuclear reactors in Japan are active, while other reactors have been idled pending safety checks.