Argonaut class reactor

Argonaut class reactor. The Argonaut class reactor was a series of low-power, thermal neutron research reactors designed by Argonne National Laboratory for training, education, and basic nuclear research. First constructed in the late 1950s, these reactors were deployed at various institutions globally, including universities and national laboratories, under initiatives like the Atoms for Peace program. Their simple, flexible design made them instrumental for teaching reactor physics, conducting neutron activation analysis, and producing short-lived radioisotopes.

Design and development

The design originated at Argonne National Laboratory in Illinois, with the first unit, ARGONAUT (Argonne Nuclear Assembly for University Training), becoming operational in 1957. The core was a heterogeneous, light-water moderated and reflected assembly, often using fuel elements of uranium oxide or uranium metal clad in aluminum. Key figures in its development included scientists from the United States Atomic Energy Commission who sought to create a safe, inexpensive tool for academic institutions. The design philosophy emphasized inherent safety through low power, negative temperature coefficients, and passive cooling, making it suitable for installation in populated areas like university campuses. Several variants were built, including the Janus reactor at the Argonne Cancer Research Hospital and units exported to countries such as Japan, Italy, and Switzerland.

Operational history

The first Argonaut reactor at Argonne National Laboratory achieved criticality in February 1957, serving as a prototype for subsequent units. Under the Atoms for Peace initiative, similar reactors were constructed at the Georgia Institute of Technology, the University of Michigan, and the University of Florida. Internationally, units were installed at the Japan Atomic Energy Research Institute in Tokai, the University of Palermo in Italy, and the Swiss Federal Institute of Technology in Zürich. These reactors were primarily used for training nuclear engineers, conducting experiments in neutron scattering, and performing neutron activation analysis for fields like archaeology and environmental science. Operational power levels were typically very low, ranging from 10 kilowatts thermal to a maximum of 100 kW, allowing for continuous, hands-on student operation.

Technical specifications

The core configuration was typically an annular or slab arrangement of fuel assemblies, moderated and cooled by light water. Fuel was often uranium enriched to about 20% ²³⁵U, in the form of plates or rods. The reactor vessel was generally a stainless steel tank, with graphite or water serving as the neutron reflector. Control was maintained through boron-stainless steel or cadmium control rods, with a typical excess reactivity margin for experimental flexibility. Thermal neutron flux levels were on the order of 10¹² neutrons per cm² per second. The simple design allowed for easy modification, with some facilities adding beam ports for neutron physics experiments or pneumatic transfer systems for radioisotope production.

Safety features and design philosophy

Safety was paramount in the Argonaut design, leveraging inherent nuclear characteristics rather than complex engineered systems. The reactor possessed a strong negative temperature coefficient of reactivity, meaning power would automatically decrease as temperature rose. The low power density and large water inventory provided substantial passive heat removal capacity. The core was designed for subcritical storage of fuel elements, requiring deliberate assembly to achieve criticality. Administrative controls and extensive training for operators, often graduate students, were integral to the safety culture. The design complied with the stringent regulations of the United States Atomic Energy Commission and later the Nuclear Regulatory Commission, setting a benchmark for the safe siting of research reactors in academic environments.

Decommissioning and legacy

Most Argonaut class reactors were shut down by the 1990s due to aging infrastructure, high operational costs, and the declining availability of suitable low-enriched fuel. Decommissioning projects, such as those at the University of Michigan and Georgia Institute of Technology, involved defueling, dismantling, and remediating the sites under oversight by the Department of Energy and relevant national authorities. The legacy of the Argonaut class is profound; it trained a generation of nuclear scientists and engineers who contributed to programs like the Naval Reactors program and advanced research at Oak Ridge National Laboratory. The design directly influenced later, more powerful research reactors, and its educational model persists in facilities like the MIT Nuclear Reactor Laboratory. Several reactor vessels are preserved as historical artifacts, commemorating the early era of peaceful nuclear technology dissemination.

Category:Research reactors Category:Nuclear technology in the United States Category:Argonne National Laboratory