What could justify four reactors in a surface warship?

If the US Navy put four reactors in a surface combatant, how should the ship use all that power?

It would need railguns, lasers, and very heavy defensive systems to justify the plant, but protecting four reactors in a surface fight would be a major design problem.

Railguns, lasers, and an extensive defensive system are suggested as loads that might justify four reactors. Even then, putting so much nuclear machinery into a ship intended for close combat is questioned. A speculative alternative would use submarine reactors in a section able to submerge after severe damage. The aim would be to keep the crew and plant alive until they could return home.