Research Reactor FR 2

Research Reactor FR 2 was the first nuclear reactor designed in Germany to achieve an atomic chain reaction. It was constructed in a period of six years. The reactor first became “critical” in March 1961 — an operating state where the neutrons released by nuclear fission maintain a stable series of further nuclear fissions. Known within the Center as “FR 2,” this reactor consumed natural uranium as fuel. In this type of reactor, the fuel elements are located in a tank containing heavy water. Unlike ordinary hydrogen, the hydrogen atoms in heavy water contain not only a proton and an electron, but also a neutron. With these additional particles, heavy water can better reflect the neutrons emitted by the fuel elements during nuclear fission onto the uranium fuel to trigger renewed nuclear fission. Using expensive heavy water obviates the need to enrich the fissile portion of uranium, a process involving costly material and technology. The reactor was used for research purposes. Its energy output, initially 12 and later 44 megawatts, was not used to generate electricity. FR 2 was utilized for basic physical research, fuel element development, and materials science investigations. It also produced preparations used in radiation therapy. FR 2 was operated until 1981. The fuel elements were removed, the heavy water sold, and the reactor core sealed. The reactor building was transferred into the hands of Kerntechnische Entsorgung Karlsruhe GmbH. This company plans to completely dismantle it to return the site into a “green field” state, scheduled to begin in the 2030s. kn