B Reactor can take a tour of the reactor by advance reservation. The reactor was designed and built by E. I. du Pont de Nemours and Company based on experimental designs tested by Enrico Fermi at the University of Chicago, and tests from the X-10 Graphite Reactor at Oak Ridge National Laboratory. It was designed to operate at 250 megawatts (thermal). The reactor occupies a footprint of (about and is tall, occupying a volume of . The reactor core itself consisted of a graphite box measuring occupying a volume of and weighing . It was penetrated horizontally through its entire length by
Aqueous homogeneous reactor hoped to design liquid-fuel reactors that would dispense with the costly destruction and processing of solid fuel elements. The formation of gas bubbles in liquid fuels and the corrosive attack on materials (in uranyl sulfate base solutions), however, presented daunting design and materials challenges. Enrico Fermi advocated construction at Los Alamos of what was to become the world’s third reactor, the first homogeneous liquid-fuel reactor, and the first reactor to be fueled by uranium enriched in uranium-235. Eventually three versions were built, all based on the same concept. For security purposes these reactors were given the code name "water boilers".