B Reactor at Hanford as seen from the tour bus April 3, 2008. The highlight of the five hour tour according to those fortunate enough to get tickets, was the one hour inside B Reactor. The 586 square mile Hanford site was perhaps the most classified ground of WW II. It's the site of B Reactor, the world's first large-scale nuclear reactor of any kind. The site produced plutonium for the Trinity device, the Nagasaki weapon and Cold War weapons. This year 48 tours with 2000 seats are being offered to the site. Within 15 minutes of online registration, 500 seats were claimed.