Clementine reactor

Clementine reactor
E. T. Jurney · Public domain · source
Name	Clementine reactor
Country	United States
Operator	Los Alamos National Laboratory
Commission	1946
Decommission	1952
Type	Experimental fast reactor
Fuel	Liquid sodium cooled, enriched uranium
Power	5 MW thermal

Clementine reactor was an early experimental fast neutron reactor constructed in the United States shortly after World War II. It was built to test principles of fast-spectrum reactor physics, materials behavior, and reactor control using liquid metal coolant. The project involved collaboration among Los Alamos National Laboratory, Argonne National Laboratory, and contractors tied to the Manhattan Project legacy and early Atomic Energy Commission programs.

Background and development

The reactor originated from post-World War II initiatives at Los Alamos National Laboratory and Oak Ridge National Laboratory to convert weapon-era research into civilian and military reactor technologies. Key figures and organizations included scientists relocated from the Manhattan Project, managers from the Atomic Energy Commission, and engineers from firms linked to General Electric and Westinghouse Electric Company. Funding and oversight were coordinated through United States Department of Energy predecessors and committees that had responded to lessons learned during the Trinity test and operations at Hanford Site. Early conceptual studies drew on data from experiments at Argonne National Laboratory and theoretical work published in proceedings of the American Nuclear Society.

Design and specifications

Clementine employed a fast neutron spectrum moderated minimally, using enriched uranium fuel assemblies and a liquid sodium coolant system pioneered in designs at Argonne National Laboratory and informed by metallurgical research from Bell Labs. The reactor core was compact, with a central arrangement of fuel pins, reflectors of beryllium and depleted uranium, and remote handling provisions developed in response to experiences at Los Alamos National Laboratory and lessons from reactor projects at Hanford Site. Instrumentation was provided by teams associated with Brookhaven National Laboratory and detectors adapted from work at Lawrence Berkeley National Laboratory. Control systems incorporated analog electronics from General Electric and safety interlocks influenced by protocols from Oak Ridge National Laboratory.

Operation and mission history

Clementine reached initial criticality under the supervision of scientists from Los Alamos National Laboratory in 1946 and operated intermittently through coordinated test campaigns shared with researchers at Argonne National Laboratory and Brookhaven National Laboratory. Mission objectives included benchmarking fast-spectrum cross section data compared with measurements at National Bureau of Standards (now National Institute of Standards and Technology), validating liquid metal coolant technologies demonstrated at Oak Ridge National Laboratory, and providing irradiations for materials programs at Sandia National Laboratories. Collaborations extended to academic groups at Massachusetts Institute of Technology, University of California, Berkeley, and University of Chicago which used irradiation data in reactor physics curricula and theses. International scientific contacts later involved delegations from laboratories in the United Kingdom and France.

Scientific and technical achievements

Clementine produced influential experimental datasets on fast neutron cross sections, breeding ratios, and sodium coolant behavior that informed subsequent reactor concepts at Argonne National Laboratory and design work for power reactors influenced by Admiral Hyman G. Rickover's submarine reactor programs. The reactor enabled pioneering materials irradiations that advanced understanding of radiation embrittlement studied at Metallurgical Laboratory-era facilities and later at Oak Ridge National Laboratory materials programs. Instrumentation advances, including neutron flux mapping and delayed neutron detection methods, were adopted by teams at Brookhaven National Laboratory and academic reactor groups at Massachusetts Institute of Technology. Data from Clementine informed regulatory frameworks later codified by the Atomic Energy Commission and standards bodies such as the American Nuclear Society.

Safety incidents and decommissioning

Operational history included challenges with liquid sodium handling and unexpected corrosion phenomena similar to issues later documented at Fast Breeder Reactor projects in Europe and at Sodium Reactor Experiment. A notable sodium leak event prompted emergency responses coordinated with specialists from Argonne National Laboratory and Oak Ridge National Laboratory, and spurred procedural changes influenced by advisory input from the Atomic Energy Commission. Decommissioning followed after a combination of technological obsolescence and strategic shifts in national reactor priorities; dismantlement activities involved teams from Los Alamos National Laboratory, contract firms with experience from the Hanford Site, and regulatory oversight from Atomic Energy Commission predecessors. Some irradiated components were transferred to Idaho National Laboratory for study.

Legacy and influence on reactor research

Clementine's datasets and operational lessons shaped subsequent fast reactor programs at Argonne National Laboratory, design analyses used in Liquid Metal Fast Breeder Reactor proposals, and materials research at Oak Ridge National Laboratory. The project's influence extended to training generations of nuclear engineers who later worked at General Electric, Westinghouse Electric Company, Bechtel Corporation, and national laboratories including Brookhaven National Laboratory and Sandia National Laboratories. Insights from Clementine contributed to international collaborations involving the European Atomic Energy Community and informed safety practices referenced by agencies such as the International Atomic Energy Agency. Historical assessments and archival materials are preserved in collections at Los Alamos National Laboratory and university archives at University of California, Berkeley.

Category:Nuclear reactors in the United States Category:Los Alamos National Laboratory