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B Reactor

The B Reactor was the first large scale nuclear reactor ever built in the world. In was constructed in 1943-44 as part of the Manhattan Project in order to produce plutonium for nuclear weapons. The B Reactor (along with D Reactor and F Reactor) provided the plutonium 239 used in the first atomic device ever exploded on July 16, 1945, known as the Trinity Test. It also produced the plutonium-239 used in the bomb dropped on Nagasaki on August 9, 1945. This was first and only plutonium weapon used in warfare. The B Reactor produced fissionable material from 1944 until its deactivation in 1968.

The B Reactor is an all water cooled, graphite-moderated reactor. It provided the basic design used in two Hanford reactors (D and F) built during the war and five Hanford reactors (DR, H, C, KW, and KE) built from 1947 to 1955. These reactors produced all the plutonium used in U.S. nuclear weapons, until 1952 when the Savannah River, S.C., plant came on line.

The B Reactor is located inside the 105-B reactor containment building in the 100-Area of Hanford. Adjacent to the building and connected by extensive above-ground exhaust ducts is a 200-foot-high reinforced concrete exhaust stack. Opposite the rear of the reactor is the fuel storage basin. This is a large below-grade concrete pool, 20 feet, 9 inches deep, which served as a collection, storage, and transfer system for the irradiated fuel elements discharged from the reactor. During operations, the basin was filled with water, but no longer contains water.

The main portion of the 105-B building consists of the reactor or pile. This is a cubical structure approximately 1,750 square feet which stands five stories tall. The reactor is penetrated through its entire length horizontally by 2,004 aluminum process tubes into which fuel elements were loaded. Uranium slugs the size of rolls of quarters and sealed in aluminum cans went into the tubes. The fuel elements for the piles were uranium slugs, measuring 1.5 inches by 8 inches, clad in aluminum jackets. The slugs were inserted into the tubes in the pile's graphite core. They would then be bombarded with neutrons, which would create a chain reaction. This chain reaction caused the uranium to convert some of its isotopes into plutonium. Reactor operators would then push the slugs now made of uranium and plutonium, out of the back of the pile where they would fall into tanks of water. This water was pumped in from the Columbia River. The time spent in the water gives the rods an opportunity to cool and allows some of the radioactivity to decay away. The fuel rods are then taken by train from the B Reactor to the processing facilities in the 200 Area where plutonium is removed from them.

The B Reactor has no moving parts. During operations the only sounds it would make would be the millions of gallons of water from the Columbia River being pumped in to cool it down. The amount of people needed to actually operate the B Reactor it was small. A typical crew was less than twenty people.

The design for the B Reactor came from the Metallurgical Laboratory in Chicago. Their design was based on the original pile built by Enrico Fermi at the University of Chicago. Fermi's pile was the first ever self-sustaining chain reaction which occurred in December 1942. To produce plutonium in sizable quantities, the B Reactor would be 500 million times more powerful than the reactor built by Fermi.

When the B Reactor came on line in 1944 it didn't operate as expected. The original design had called for the reactor to use 1500 process tubes filled with uranium fuel. It was almost immediately realized this would not be enough to sustain the nuclear reaction. With only 1500 tubes filled, there was another element called xenon that was capturing too many neutrons. Another 504 process tubes were added to the reactor. These extra fuel rods made up for the neutrons the xenon was capturing and a sustainable nuclear reaction was possible.

The B Reactor was operating at full power by December 28, 1944. By the beginning of 1945, all three of Hanford's plutonium reactors (B, D and F) were operating at an industrial scale of production. Early in 1945, officials at Hanford began to ship plutonium produced at the plant's reactors to Los Alamos, New Mexico, where the first atomic devices would be assembled. By the spring of 1945, Hanford was sending shipments of plutonium to Los Alamos every five days. When the war in Europe ended, senior government officials began to worry that the war in Japan would end before the bombs were ready. This intensified the emphasis on the quantity of plutonium produced at Hanford. To meet this demand, Hanford officials ran their reactors at levels higher than they were rated for. The amount of time that irradiated fuel was allowed to cool in the water was shortened and there was an increase of the amount of radioactive waste that was released into the atmosphere. This was done even when even when the wind would likely disperse the emissions over populated areas.

After World War II ended the United States found it essential to contain the power and influence of the Soviet Union. A key component in this strategy was to build up a large nuclear arsenal. The B Reactor at Hanford was a major producer of the plutonium used in these weapons. In the early 1950s, President Truman ordered the development of thermonuclear weapons. This changed the power, size, and type of weapons being built by the United States. The B Reactor was now also producing Tritium as well as plutonium. President Eisenhower wanted the United States capable of a massive retaliation in the event of nuclear war. This created a greater need for plutonium. To meet these demands, the operation levels at the B Reactor and the other reactors at Hanford were continually increased. The B Reactor eventually was operating at nearly ten times its original design level. This allowed for dramatic increases to the United States stock pile of weapons. In 1950 the United States had 369 nuclear warheads. This increased to 20,434 ten years later and reached a peak of 31,642 in 1965. The United sates had also built up an extensive stock pile of plutonium and the need for production went down.

After producing plutonium for twenty years, the B Reactor was shut down in February of 1968. Initially the reactor was slated for a process known as cocooning. This involves encasing the reactor core into a concrete shell for 75 years to allow the radioactivity to decay away. Instead, the United States Department of Interior designated the B reactor as a National Historic Landmark in 2008.


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