4 ms·
Slightly hesitant to jump in since pfdietz definitely knows more about this than I do... but... Cooling typically means things like maximizing surface area, mi
by gpm 2y ago
Slightly hesitant to jump in since pfdietz definitely knows more about this than I do... but...
Cooling typically means things like maximizing surface area, minimizing the thickness of the object being cool, etc.
Maximum neutron density presumably happens in a sphere, which is coincidentally the shape that minimizes surface area.
The whole point of a nuclear reactor is that it heats up, and you can convert that heat into useful fuel. Presumably that means you need to carry quite a lot of heat away per volume. Presumably that means putting the fuel into a spherical shape really doesn't work that well.
- AnthonyMouse 2y agoTo cool something, you need a material which is a decent conductor of heat. The reaction materials are mostly uranium, plutonium and thorium, which are metals. They conduct heat pretty well all on their own.
- pfdietz 2y agoMetal fuels also melt at considerably lower temperature than oxide fuels. Uranium oxide melts at 2865 C; uranium metal at 1132 C, plutonium metal at just 639 C. In contact with iron, plutonium forms a eutectic with a melting point of just 410 C, below the melting point of zinc. There was a crazy reactor at Los Alamos, LAMPRE, that used molten eutectic Pu-Fe in tantalum tubes as the fuel.
- AnthonyMouse 2y ago1132 C shouldn't be an infeasibly low temperature when the reactor is only expected to heat the coolant to 300-350 C. Meanwhile thorium metal is 1750 C. Or use uranium carbide. High melting point with still decent thermal conductivity.