Patent Number: 
Section: claims

1. A method for cooling component cooling water in a nuclear power plant, the method comprising:providing a containment vessel defining containment space housing a nuclear reactor, a containment enclosure structure surrounding the containment vessel, and an annular water reservoir formed between the containment vessel and containment enclosure structure containing water to provide a heat sink for dissipating thermal energy;immersing a shell-less heat exchanger including heat transfer tube bundle in the water within the annular water reservoir; andcirculating heated component cooling water from the plant through the tube bundle; andcooling the heated component cooling water by transferring heat to the annular water reservoir. 2. The method of claim 1, wherein the tube bundle is comprised of a plurality of heat transfer tubes exposed directly to the water in the annular water reservoir. 3. The method of claim 2, wherein the tube bundle is U-shaped. 4. The method of claim 3, wherein a bottom end of the tube bundle is spaced vertically apart from a bottom of the annular water reservoir. 5. The method of claim 3, wherein the tube bundle is vertically oriented. 6. The method of claim 3, wherein the tube bundle is connected to a tube sheet supported by a channel defining an inlet flow chamber and an outlet flow chamber each fluidly coupled to the tube bundle. 7. The method of claim 6, wherein:the channel is structurally supported and restrained inside the annular water reservoir, andthe tube bundle is hung from the channel and unrestrained to grow and contract in length under thermal expansion. 8. The method of claim 6, further comprising in sequence flowing heated component cooling water into the inlet flow chamber, flowing the heated component cooling water through each tube of the tube bundle which cools the heated component cooling water producing cooled component cooling water, and flowing the cooled component cooling water into the outlet flow chamber. 9. The method of claim 8, further comprising a partition plate disposed in the channel which divides the channel into the inlet and outlet flow chambers. 10. The method of claim 2, further comprising positioning a discharge sparger below the tube bundle in the annular water reservoir, extracting water from the annular water reservoir with a pump in a recirculation piping loop fluidly coupled to the annular water reservoir, pumping the extracted water through the recirculation piping loop, and discharging the extracted water through the sparger and the tube bundle in the annular water reservoir for cooling the heated component cooling water. 11. The method of claim 10, wherein the sparger forms part of a pumped recirculation system fluidly coupled to the annular water reservoir. 12. The method of claim 1, further comprising flowing the component cooling water through a cooling water piping loop in the plant which is fluidly coupled to the heat exchanger for conveying the component cooling water to and from the heat exchanger. 13. The method of claim 12, further comprising recirculating component cooling water through the cooling water piping loop between the annular water reservoir and equipment in the plant. 14. The method of claim 13, further comprising pumping the component cooling water through the cooling water piping loop via at least one pump fluidly coupled to the cooling water piping loop. 15. The method of claim 1, further comprising a plurality of substantially radial fins protruding outwards from the containment vessel and located in the annular water reservoir, and further comprising a step of locating the heat exchanger in one of a plurality of bays formed in the annular water reservoir between spaced apart adjacent fins. 16. The method of claim 15, wherein the fins are obliquely oriented to the containment vessel. 17. The system of claim 15, wherein the heat exchanger is positioned in a location within the annular water reservoir which is in proximity to an inlet from a reservoir makeup water supply system that discharges water into the annular water reservoir thereby replacing water lost by evaporation. 18. The method of claim 17, wherein the inlet from the reservoir makeup water supply system and the heat exchanger are located in the same bay. 19. A method for cooling component cooling water in a nuclear power plant, the method comprising:providing a containment vessel defining containment space housing a nuclear reactor, a containment enclosure structure surrounding the containment vessel, and an annular water reservoir formed between the containment vessel and containment enclosure structure containing water to provide a heat sink for dissipating thermal energy;immersing a shell-less heat exchanger including heat transfer tube bundle in the water within the annular water reservoir, the tube bundle being exposed and wetted directly by the water;providing a recirculation piping loop fluidly coupled to the annular water reservoir at an inlet and an outlet;extracting water from the annular water reservoir with a pump in the recirculation piping loop;discharging the extracted water through the a sparger located below the tube bundle in the annular water reservoir, the sparger configured to discharged the extracted water upwards through the tube bundle;circulating heated component cooling water from the plant through the tube bundle; andcooling the heated component cooling water by transferring heat to the annular water reservoir. 20. A method for cooling component cooling water in a nuclear power plant, the method comprising:providing a containment vessel defining containment space housing a nuclear reactor, a containment enclosure structure surrounding the containment vessel, an annular water reservoir formed between the containment vessel and containment enclosure structure containing water to provide a heat sink for dissipating thermal energy, and a plurality of substantially radial fins protruding outwards from the containment vessel into the annular water reservoir to define a plurality of bays;immersing a shell-less heat exchanger in the water of a first bay within the annular water reservoir, the heat exchanger including heat transfer tube bundle having a plurality of bare tubes exposed directly by the water;providing a recirculation piping loop fluidly coupled to the annular water reservoir, the recirculation piping loop including an inlet fluidly coupled to a second bay of the annular water reservoir and an outlet including a sparger fluidly coupled to the annular reservoir and immersed in the water in the first bay;pumping water from the annular water reservoir in the recirculation piping loop between the first and second bays;circulating heated component cooling water from the plant through the tube bundle; andcooling the heated component cooling water by transferring heat to the annular water reservoir.