System for startup support of externally heated turbine engine

1. A power-generation system for a nuclear reactor, the power-generation system comprising

a power unit that includes a first generator for producing electric energy and a turbine engine coupled to and configured to drive the first generator, the turbine engine includes a compressor configured to receive and compress ambient air to produce compressed air and a turbine configured to extract work from the compressed air after the compressed air is heated to drive the first generator,

a reactor heat exchanger in fluid communication with and between the compressor and the turbine and configured to transfer heat from the nuclear reactor to the compressed air to heat the compressed air, and

a heat recuperating system configured to transfer heat to the compressed air to supplement the reactor heat exchanger during a startup mode of the power-generation system, the heat recuperating system comprising an auxiliary power unit and a recuperating heat exchanger that is fluidly connected with the auxiliary power unit, the auxiliary power unit configured to produce electric power and heated exhaust air, and the recuperating heat exchanger is further fluidly connected with the compressor and the turbine and configured to transfer heat from the heated exhaust air to the compressed air,

wherein the power-generation system further includes a controller programmed to turn off the auxiliary power unit in response to the reactor heat exchanger heating the compressed air to a threshold temperature.

2. The power-generation system of claim 1 , wherein the recuperating heat exchanger is fluidly connected to the turbine engine and the reactor heat exchanger downstream of the compressor and upstream of the reactor heat exchanger.

3. The power-generation system of claim 1 , wherein the recuperating heat exchanger is fluidly connected to the turbine engine and the reactor heat exchanger downstream of the reactor heat exchanger and upstream of the turbine.

4. The power-generation system of claim 1 , wherein the heat recuperating system further includes a second generator coupled with the auxiliary power unit and configured to be driven by the auxiliary power unit.

5. The power-generation system of claim 4 , wherein the auxiliary power unit comprises a gas turbine engine.

6. A power generation system comprising

a power unit that includes a first generator for producing electric energy and an externally-heated turbine engine having a compressor configured to produce compressed air and a turbine configured to drive the first generator,

a reactor heat exchanger in fluid communication with the compressor and the turbine and configured to transfer heat from a nuclear reactor to the compressed air, and

a heat recuperating system having an auxiliary power unit and a recuperating heat exchanger fluidly connected with the auxiliary power unit and fluidly connected to the externally-heated turbine engine,

wherein the power generation system further includes a controller programmed to activate the auxiliary power unit included in the heat recuperating system in response to the reactor heat exchanger heating the compressed air to a temperature below a threshold temperature and to turn off the auxiliary power unit included in the heat recuperating system in response to the reactor heat exchanger heating the compressed air to a temperature equal to or greater than the threshold temperature.

7. The power generation system of claim 6 , wherein the recuperating heat exchanger is fluidly connected to the externally-heated turbine engine and the reactor heat exchanger downstream of the compressor and upstream of the reactor heat exchanger.

8. The power generation system of claim 6 , wherein the recuperating heat exchanger is fluidly connected to the externally-heated turbine engine and the reactor heat exchanger downstream of the reactor heat exchanger and upstream of the turbine.

9. The power generation system of claim 6 , wherein the controller is programmed to idle the externally-heated turbine engine in response to the compressed air being heated to a temperature equal to or greater than the threshold temperature.

10. The power generation system of claim 6 , wherein the heat recuperating system further includes a second generator coupled with the auxiliary power unit and configured to be driven by the auxiliary power unit.

11. The power generation system of claim 10 , wherein the auxiliary power unit includes a turbine engine.

12. A method of operating a power-generation system for a nuclear reactor, the method comprising,

operating an auxiliary power unit to generate electric energy and a heated first fluid,

heating a second fluid with a reactor heat exchanger,

compressing air with a compressor to produce compressed air,

transferring heat from the first fluid to the compressed air,

transferring heat from the second fluid to the compressed air, and

conducting the compressed air through a turbine after transferring heat from the first fluid and the second fluid to the compressed air,

further comprising shutting off an engine included in the auxiliary power unit in response to a temperature of the compressed air being equal to a threshold temperature.

13. The method of claim 12 , wherein transferring heat from the first fluid to the compressed air is performed after transferring heat from the second fluid to the compressed air.

14. The method of claim 12 , wherein transferring heat from the first fluid to the compressed air is performed prior to transferring heat from the second fluid to the compressed air.

15. The method of claim 12 , further comprising driving a first generator with the turbine.

16. The method of claim 15 , further comprising driving a second generator with the auxiliary power unit.

17. The method of claim 12 , wherein the auxiliary power unit includes a turbine engine.