The Molten-Salt Reactor Experiment ran on liquid fuel — a lithium-beryllium-zirconium-uranium fluoride salt melting at 434 °C, pumped through Hastelloy-N at 635–663 °C, held in the core by a freeze valve that is exactly what it sounds like: a plug of salt frozen solid on purpose, thawed to drain the reactor.

The look comes from the cell itself. Cool near-black steel grey, dull red where the heat exchanger is hot, and above it the only two saturated colors a nuclear facility is allowed to sign itself with — caution yellow and the magenta trefoil. Everything else is instrument panel and label.