Flattop (critical assembly)

The flattop experiment, disassembled

Flattop is a benchmark critical assembly that is used to study the nuclear characteristics of uranium-233, uranium-235, and plutonium-239 in spherical geometries surrounded by a relatively thick natural uranium reflector.

Flattop assemblies are used to measure neutron activation and reactivity coefficients. Since the neutron energies gradually decrease in the reflector, experiments may be run in various energy spectra based on the location in which they are placed.[1]

The experiment was originally located at the Los Alamos National Laboratory Critical Experiments Facility (LACEF), but was moved to the National Criticality Experiments Research Center (NCERC) at the Nevada National Security Site, along with three other critical assemblies, Comet, Planet, and Godiva-IV. In 2012, these facilities were operational.[2]

The U-233 core is no longer usable because of its high gamma-ray activity.[1]

Controls

Flattop consists of a hemispherical fixed reflector and two movable quarter-spheres of reflector that can close down on the central core. One movable reflector is controlled by hydraulic pressure, while the other is actuated by a motor.[1]

See also

External links

References

  1. 1 2 3 Malenfant, R. E. (June 1981). "Los Alamos Critical Assemblies Facility". Los Alamos National Laboratory. LA-872-MS. doi:10.2172/6463833. Retrieved 28 November 2012.
  2. ↑ Hayes, David K.; Myers (16 July 2012). "National Criticality Experiments Research Center: Capability and Status". Institute of Nuclear Materials Management 53rd Annual Meeting (LA-UR-12-22906). Retrieved 28 November 2012.
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