The Nuclear and Industrial Safety Agency is to set a new safety standard for nuclear plants by requiring operators to confirm the probability of aircraft crashing into plants to be less than one in 10 million, agency sources said.
The decision by the agency, which comes under the Ministry of Economy, Trade and Industry, to set safety standards based on probability is rare, the sources said.
The new standard will apply to new plants currently being evaluated for safety. The agency will also check existing plants to see if they meet the requirement.
Present standards say there is no need for crash likelihood provisions if there is no airport within 10 km of a plant.
Under the new regulations, if a plant is near an airport or beneath a flight route, the crash probability for large aircraft will be calculated based on past accident data for planes departing and landing at the airport or the probability of a crash during a flight.
The agency will calculate an average nationwide uniform probability for small aircraft as they could crash regardless of airport or flight path locations.
The likelihood of crashes involving planes from the U.S military or the Self-Defense Forces will also be calculated based on the location of training areas.
The agency does not intend to include possible terrorist attacks on nuclear plants in the safety standard, it said.