5 ms·

While we're at it, are safety considerations the only problem that prevented nuclear powered automotive engines? I've always wondered why.

• brandmeyer 10y ago
  Mostly its about size. There is effectively a minimum viable size for a fission reactor. There are a pinch more than 2 neutrons born from each fission event. In order to operate at criticality, exactly one of them must go on to produce another fission. Leakage of neutron radiation from the effective surface of the core is a major way that neutrons don't make it to cause another fission event. As the ratio of surface area to volume goes up (because the core got smaller) it becomes harder and harder to design a core that doesn't lose neutrons to the other loss mechanisms to keep up with the increasing loss out the core's surface.