A system for producing electricity having a primary coolant loop having, in operable and fluid coupling, a vertical nuclear reactor, a vertical once-through steam generator, at least one external hot leg conduit, and at least one external hot leg conduit. The at least one external hot leg conduit fluidly is coupled with the vertical nuclear reactor and to the vertical once-through steam generator to deliver a primary coolant from the vertical nuclear reactor to the vertical once-through steam generator. The at least one external cold leg conduit is fluidly coupled with the vertical nuclear reactor to the vertical once-through steam generator to return the primary coolant from the vertical once-through steam generator back to the vertical nuclear reactor. At least one booster pump is operably coupled to the primary coolant loop to force flow of the primary coolant through the primary coolant loop during normal operation of the system.