On: NASA Revives Plan to Put Nuclear Reactors on Mars

[xorfish]

Enriched uranium has a very high energy density. 20% enriched Uranium would contain 16TJ/kg.

So a 4MW u-battery would use around 8kg fuel per year.

[baybal2 → xorfish]

>Enriched uranium has a very high energy density. 20% enriched Uranium would countain 16TJ/kg.

I did not count in burnup ratio. A simple thermal neutron reactor can only use <1% of fission energy in its fuel.

[DennisP → baybal2]

NASA's Kilopower uses sodium coolant, so it's a fast reactor and gets much more energy out of its fuel. It needs enough U235 to kick off the reaction but after that it will fission the U238 as well.

Burnup could still be limited due to fission products poisoning the reaction.

[xorfish → baybal2]

I'm pretty sure that conventional reactor split around as much fuel as the U-235 content.

For conventional reactors it is around 3% and you are left with around 3% fission products.

Natural uranium has around 0.7% U-235. But I0m pretty sure that you would enrich the uranium befor you send it to mars. The 16TJ/kg is for enriched uranium with 20% U-235 content.

Anyway, energy density of nuclear fuel is extremly high. Even if you pay 10000 USD/kg for the transport of fuel to mars, you'd pay around 1 cent/kwh for the transport.

[baybal2 → xorfish]

Yes, it will be higher by few times for highly enriched uranium (90%+) or plutonium 239 (because of higher cross-section)