A test nuclear reactor in northern Japan shut down automatically early on Wednesday morning after lightning struck a power line serving the facility, the country's atomic energy agency said.
There was no radiation leak or damage, it said.
The 140,000-kilowatt Joyo experimental fast reactor at the Japan Atomic Energy Agency's O-arai Research and Development Center in Ibaraki prefecture shut down shortly before 1:00 am on Wednesday after lightning hit a commercial power line serving the reactor, the agency said in a statement.
Power from the line was restored 1 1/2 hours later, the agency said. No other facilities at the site were affected.
The reactor was in the middle of a test operation that remains on track to run from December 11 to February 2, said O-arai spokesman Minoru Gunji.
The reactor needs to be cooled down before it can be restarted, which the agency hopes will take place as early as this evening, he said.