All seats on Hanford nuclear reservation tours for 2017 had been claimed within about 2 hours of the start of registration at 9 a.m. Tuesday.
A limited number of walk-on seats also may be available.
The Department of Energy tours are offered on 20 weekdays from May 3 to Sept. 13.
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Seats remain available for two different historical tours of the Manhattan Project National Historical Park at Hanford, which are offered more frequently. Participants can choose from a tour of historic B Reactor or pre-World War II sites.