"The [statement] that the heat released by the complete fission of one pound of nuclear fuel is equivalent to that obtainable by 1400 tons of coal (or 300,000 gallons of fuel oil), has led to some erroneous conclusions. The fantastic possibility has been envisaged of including in an automobile enough fissionable material, about the size of a pea, to last the life of the vehicle. In order to realize why this is not within the bounds of reality, it is necessary to understand something about the fission process."
Glasstone -- Principles of Nuclear Reactor Engineering (1955) [1]
[1] https://babel.hathitrust.org/cgi/pt?id=mdp.39015003994194&vi...