Patent Number: 
Section: claims

1. A power module assembly comprising:a reactor vessel containing a reactor core surrounded by a primary coolant;a containment vessel submerged in a containment cooling pool, wherein the containment vessel is configured to prohibit a release of the primary coolant outside of the containment vessel;one or more inlets submerged in the containment cooling pool, wherein the one or more inlets are configured to draw a secondary coolant from the containment cooling pool during an emergency operation, wherein the emergency operation comprises a loss of secondary coolant flow;a heat exchanger in contact with the primary coolant, wherein the heat exchanger is configured to remove heat generated by the reactor core, and wherein the heat is removed by circulating the secondary coolant from the containment cooling pool through the heat exchanger via natural circulation; andone or more outlets submerged in the containment cooling pool, wherein the one or more outlets are configured to vent the secondary coolant into the containment cooling pool, and wherein the primary coolant remains completely retained within the containment vessel during the emergency operation. 2. The power module assembly according to claim 1, wherein the natural circulation comprises a circulation path of the secondary coolant entering the one or more inlets, passing through the heat exchanger, exiting the one or more outlets, and re-entering the one or more inlets. 3. The power module assembly according to claim 1, wherein the secondary coolant is vented into the containment cooling pool by the one or more outlets after passing through the heat exchanger. 4. The power module assembly according to claim 1, wherein the secondary coolant circulates through the heat exchanger by the natural circulation due to both a temperature difference between the secondary coolant and the primary coolant and a difference in elevation between the one or more inlets and the one or more outlets. 5. The power module assembly according to claim 1, wherein the one or more outlets are positioned at an elevation of the containment cooling pool that is above an elevation of the one or more inlets, and wherein the secondary coolant circulates through the primary coolant by the natural circulation due to an elevation difference between the one or more inlets and the one or more outlets. 6. The power module assembly according to claim 1, further comprising:an inlet line configured to deliver the secondary coolant from the one or more inlets to the heat exchanger; andan outlet line connecting the heat exchanger to the one or more outlets. 7. The power module assembly according to claim 5, wherein the natural circulation occurs as a result of a temperature change of the secondary coolant that is drawn and vented into the containment cooling pool, and wherein the natural circulation further occurs as a result of the elevation difference. 8. The power module assembly according to claim 6, wherein the secondary coolant is circulated from the containment cooling pool through the heat exchanger without any pump. 9. The power module assembly according to claim 6, further comprising an accumulator tank configured to inject auxiliary coolant into the inlet line when a loss of secondary coolant flow is detected, wherein the accumulator tank provides the auxiliary coolant to the heat exchanger until the natural circulation of the secondary coolant is established. 10. A power module assembly comprising:a reactor vessel containing a reactor core surrounded by a primary coolant;containment means configured to prohibit a release of the primary coolant into a surrounding containment cooling pool;means for removing heat from the reactor vessel, wherein the means for removing heat is at least partially surrounded by the primary coolant;means for drawing emergency feedwater from the containment cooling pool when a loss of feedwater condition is detected;means for venting the emergency feedwater into the containment cooling pool while the containment means continues to prohibit the release of the primary coolant into the containment cooling pool, wherein the means for venting is submerged in the containment cooling pool; andmeans for circulating the emergency feedwater from the containment cooling pool through the means for removing heat and back to the containment cooling pool, wherein the emergency feedwater is circulated through natural circulation. 11. The power module assembly according to claim 10, wherein the means for drawing is submerged in the containment cooling pool, and wherein the means for drawing is positioned at an elevation in the containment cooling pool that is lower than an elevation of the means for venting. 12. The power module assembly according to claim 11, wherein the natural circulation is due to an elevation difference between the means for drawing and the means for venting, and wherein the natural circulation is further due to a difference in density of the emergency feedwater that is vented from the means for venting and the emergency feedwater that is drawn from the containment cooling pool. 13. The power module assembly according to claim 10, wherein the means for circulating does not comprise a pump. 14. The power module assembly according to claim 10, wherein the means for drawing does not comprise a pump. 15. The power module assembly according to claim 1, wherein the containment vessel is internally dry before the emergency operation. 16. The power module assembly according to claim 10, wherein the containment means is internally dry before the loss of feedwater condition. 17. The power module assembly according to claim 10, wherein the emergency feedwater circulates through the means for removing heat by the natural circulation due to both a temperature difference between the emergency feedwater and the primary coolant and a difference in elevation between the means for drawing and the means for venting. 18. The power module assembly according to claim 10, wherein the means for venting are positioned at an elevation of the containment cooling pool that is above an elevation of the means for drawing, and wherein the emergency feedwater circulates through the primary coolant by the natural circulation due to an elevation difference between the means for drawing and the means for venting.