Completed in September 1944, the B Reactor was the world's first large-scale plutonium production reactor. As at Oak Ridge, the need for labor turned Hanford into an atomic boomtown, with the population reaching 50,000 by summer 1944. Similar to the X-10 Graphite Reactor at Oak Ridge in terms of loading and unloading fuel, the B Reactor was built on a much larger scale and used water rather than air as a coolant. Whereas the X-10 had an initial design output of 1,000 kilowatts, the B Reactor was designed to operate at 250,000 kilowatts. Consisting of a 28- by 36-foot, 1,200-ton graphite cylinder lying on its side, the reactor was penetrated through its entire length horizontally by 2,004 aluminum tubes. Two hundred tons of uranium slugs the size of rolls of quarters and sealed in aluminum cans went into the tubes. Cooling water from the Columbia River, which first had to be treated, was pumped through the aluminum tubes around the uranium slugs at the rate of 75,000 gallons per minute. Water consumption approached that of a city of a third-of-a-million people. The B Reactor was one of three reactors--along with the D and F reactors--built about six miles apart on the south bank of the Columbia. Each reactor had its own auxiliary facilities that included a river pump house, large storage and settling basins, a filtration plant, huge motor-driven pumps for delivering water to the face of the pile, and facilities for emergency cooling in case of a power failure The three reactors produced plutonium for the Trinity device, the Nagasaki weapon, and Cold War weapons. The D and F reactor buildings have been severely cut back and essentially entombed. Most auxiliary buildings at all three reactors have been demolished. The interior of the B Reactor building and the face of the reactor are currently accessible via public tour.