Uranium-235 is around 24 GWh/kg [1] (24,000,000,000 Wh).

[1] https://www.euronuclear.org/glossary/fuel-comparison/

Whoa so… 100kwh is 40mg! 3grains of sand to run a Tesla

https://www.wolframalpha.com/input?i=100kwh%2F%282.5+gwh%2Fk...

Except a lot more is released at once so it will accelerate like a jet engine on every stop sign

Haha yes I did not think about that. There’s no throttling there

You need to account for all the weight required to turn the radiation into electricity.

That'll make the numbers ... a bit different.

Not necessarily:

https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...

The GPHS RTG contains 7.8 kilograms of plutonium 238 but masses 57 kg in total. It also generates only 300 watts from that 57 kg package:

https://en.wikipedia.org/wiki/GPHS-RTG

You'd need about 3 metric tons of them to power one Model 3 cruising at highway speed (assuming ~16 kilowatts continuous power draw).

Not to mention that you have to mine and refine a couple of tonnes of ore for every kilogram of refined uranium.