Not your standard reactor
“A traditional light water cooled reactor makes a gigawatt in electricity. It’s a million times bigger, it’s very complicated, and it’s designed so it utilizes the fuel very well,” McClure says. At the size of the little Martian reactor, things get a lot less fuel-efficient. “But we do have a reactor that is very easy to predict, easy to operate, and in fact can control itself,” he says, which cuts down on the likelihood of accidents that might loom over a bigger power source.
In other words, we’re not risking a nuclear meltdown on Mars.
“Melting fuel would be difficult if not impossible for the applications that we’re doing,” McClure says. “The way we’ve got the physics designed, the reactor will basically put out as much heat as is being asked of it. So if we lose cooling and are just radiating a little bit of heat energy away, the reactor will drop in power to match that.”
It’s also designed to operate in the odd environment of space. We think of space as cold, but keeping a reactor cool in a vacuum isn’t so easy. There’s no material like air or water flowing by that can transfer heat away from your generators. Instead, the system relies on eight heat pipes, each filled with about one tablespoon of sodium, which has a high boiling point.
The sodium boils at high heat, when it gets near the parts of the pipes closest to the fissioning uranium fuel. The vapor travels down the
Article source: https://www.popsci.com/nuclear-reactors-mars