1. A nuclear drive in a submarine delivers 25,000 shaft horse power at a cruising speed of 20 knots (1 knot = 1.15 miles/h). If the power plant has an efficiency of 25%, how much (in kg) of the 235U fuel is consumed on a 40,000 mile trip around the world?
2. Reactors for naval vessels are designed to have very long lifetimes without the need to refuel. Discuss possible techniques that can be used to maintain criticality over the core lifetime as 235U is consumed.