Significant portions of major geological faults running under Tohoku Electric Power Co.'s one-reactor Higashidori nuclear power plant in Aomori Prefecture are probably active, a Nuclear Regulation Authority panel said in a draft report Monday.

The faults apparently do not run directly beneath the complex's reactor but the assessment indicates the unit may have to remain offline for quite some time because the utility will need to reassess the plant's quake resistance and take measures to reinforce the facilities.

The draft report, which was a summary of discussions among panel members, also touched on the need to further study other smaller faults that run underneath an area close to the reactor building.