Flattop (critical assembly)

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 neutron reflector.

[1] Flattop is a natural-uranium-reflected, benchmarked, fixed-geometry critical assembly machine that can accommodate plutonium or uranium cores.

Key missions for Flattop include fundamental reactor physics studies, sample irradiation for radiochemical research, actinide minimum critical mass studies, detector calibration, and training.

The core capabilities at NCERC include Flattop along with three other critical assemblies, Comet, Planet, and Godiva-IV and a significant inventory of nuclear material items available for experimental use.

A team from the NASA Glenn Research Center in partnership with the LANL reactor design team designed, built, and tested a heat pipe and power conversion system to couple to Flattop with the end goal of demonstrating electrical power production using technology applicable to space application.