1.   Once the process is under way, empire-building adds fuel to the fire, and more fat to the bureaucracy.

2.   Also, Leventhal contends that using mixed-oxide fuel in power plants adds a risky step between dismantling weapons and isolating the plutonium at waste storage sites.

3.   A larger spacecraft equipped with braking rockets and more fuel would have added hundreds of millions of dollars to the price tag.

4.   Extra fuel adds weight, which translates into increased operating costs to the airlines.