In February of 2013, a panel assembled by the Nuclear Regulation Authority in Japan found two faults which run under the Higashidori nuclear power plant site in Aomori Prefecture to be highly likely active. Experts also concluded that all eight F-type faults on the site were systematically linked and that the F-3 fault and the F-9 fault produced repeated strike-slip thrusts in the past.
Although the Higashidori plant was not damaged by the March 11th earthquake and tsunami, Tohoku Electric was forced to delay its preparations for newly updated safety standards and completion of safety applications for restart. In response to the NRA findings, the licensee announced they would work to show that there were no active faults and would release the results of their investigation in December.
This week, the Tohoku Electric Power Company released the results of their findings and repeated their sentiment that the faults under the facility are not active. The report said that the distortion in the strata, which was used as evidence for the finding of active faults by NRA experts, still had not been confirmed and reiterated their opinion that it may have been caused by the soil absorbing water.
The findings by the NRA panel in February of 2012 threw a wrench into any plans by the licensee to restart the idled nuclear reactors.
Tohoku Electric operates a BWR reactor at the Higashidori site, where one other reactor is under construction and two more were planned. Two of the reactors which were planned were to be operated by the Tokyo Electric Power company, which began construction of the first unit on January 25th, 2011.
The utility has emphatically denied the presence of active faults on-site and insists that the faults will not trigger seismic activity in the future and pose no safety risks to the reactors, but experts remain unconvinced. Some of the fault lines lie only 200 meters from one of the reactor buildings on-site.
The licensee, Tohoku Electric, has asserted that the fault slips under the plant site are instead due to changes in groundwater levels and that the strata inflates after sucking in water, but these conclusions were not considered valid by Nuclear Regulation Authority Commissioner Kunihiko Shimazaki, a retired seismologist at the University of Tokyo.
Yasuo Awata, chief scientist for the National Institute of Advanced Industrial Science and Technology also did not consider the utilities explanation for the displacement to be credible, saying that the “description of the Tohoku Electric Power does not make sense.”
If the faults are determined to be active, Tohoku Electric would be forced to revise their analysis of the plant’s tolerance of ground movement caused by an earthquake, which is a very costly project.
On December 24th, 2013, a number of volcano experts found that the Higashidori nuclear power facility is also in the vicinity of calderas, enormous depressions in the earth formed by massive volcanic eruptions.