Hanford’s 100 Area is the part of the Site located along the banks of the Columbia River. It is where the nine former plutonium production reactors are found. The nine reactors (B Reactor, C Reactor, D Reactor, DR Reactor, F Reactor, H Reactor, K-East Reactor, K-West Reactor, and N Reactor) were built from 1943 through 1965. They were constructed next to the river because of the abundance of hydro electric power and cooling water needed by the reactors during operation.
These reactors were needed to facilitate the process by which the element uranium was changed into the man-made element plutonium. Plutonium, known as an isotope, was the critical substance required in order for atomic weapons to be produced. However, in order to understand how the uranium was changed into plutonium, a basic understanding of chemistry is needed.
In the universe, atoms combine to form all solids, liquids, and gases. Within each atom, there are particles called neutrons, protons, and electrons. The number of each of those particles determines the material that you have. For example, if you are looking at a material where there are 92 protons and 146 neutrons, you are looking at a material called uranium 238 (adding together the protons and neutrons gives you the number 238).
Inside the nuclear reactors at Hanford, a process called a chain reaction changed the chemical composition of uranium by exposing the material to extra neutrons. During Hanford’s mission of plutonium production from 1943 through 1987, tons of plutonium were produced as a result of hundreds of thousands of tons of metal uranium fuel rods being subjected to the nuclear chain reactions in the reactors.
This process of producing plutonium is extremely inefficient. The years of plutonium production generated millions of tons of solid waste and contaminated soil, as well as billions of gallons of liquid waste. Cleaning up those wastes constitutes Hanford’s current mission for the Department of Energy.
None of Hanford’s nine reactors are in operation any more with the last reactor, the N Reactor, being shut down in 1988. Beginning in the 1990’s, workers began the process of “cocooning” the reactors. When a reactor is cocooned, about 80% of the buildings and auxiliary structures which were needed to support the reactor during its operating days are demolished and removed. The remaining 20% of the reactor complex, including the core of the reactor itself, is enclosed in a cement and steel, airtight and watertight structure called a cocoon. This cocoon prevents any radiation or contamination left over from the nuclear operations from escaping to the environment. Ultimately, eight of the nine reactors at Hanford will be cocooned. C, D, DR, F, and H Reactors are already cocooned, with N, K-East, and K-West Reactors next in line to be cocooned. B Reactor has been named a National Historic Landmark by the United States Department of the Interior and may be preserved as a museum.
Every five years, Hanford crews enter these cocoons to ensure that the structure remains airtight and watertight. These cocoons will be in place over the reactors for approximately 75 years allowing the radiation within the reactors to safely decay to levels where it doesn’t pose a threat to the environment or the workers performing final demolition. Hanford engineers and scientists are already working on plans which will result in these cocooned reactors being removed from the area along the river and safely demolished following the 75-year life span of the cocoon.