Lead cooled thermal spectrum nuclear reactor & power plant

Abstract

A nuclear power reactor, the reactor comprising: a core having an array of fuel assemblies (FAs) each containing a bundle of fuel rods packed with a nuclear fuel and comprising a moderating material that thermalizes neutrons emitted by the fuel when the fuel in the core is burned in a chain reaction; and a cooling system that circulates a liquid metal coolant to remove heat from the core generated by fission.

Description

LEAD COOLED THERMAL SPECTRUM NUCLEAR REACTOR & POWER PLANTRELATED APPLICATION

[0001] This application claims benefit of U.S. Provisional Application 63 / 747,157 filed on January 20, 2025, and of Israeli Application 322093 filed July 14, 2025, the disclosures of which are incorporated herein by reference in their entirety.FIELD

[0002] Embodiments of the disclosure relate to liquid lead cooled nuclear reactors configured to generate power from fission caused by thermal neutrons.BACKGROUND

[0003] Nuclear power plants generate electricity by producing heat in a nuclear reactor that is used to convert water into steam. The steam drives a turbine connected to an electric generator, to produce electricity. The heat is generated by nuclear fission of a fissile material - typically enriched uranium -235 (235pj) . jn acontrolled chain reaction that takes place in a reactor core. The fissile material in the core is arranged in a tightly spaced array of fuel assemblies (FAs) that is contained in a “core barrel” which is housed in a reactor vessel together with a fluid coolant that removes heat from the core during reactor operation. Each fuel assembly comprises a closely packed bundle of fuel rods, and each fuel rod contains a large number of enriched fissile fuel pellets encased within a tube-shaped cladding. The array of FAs in the core barrel and / or of fuel rods within the FAs leaves channels or incorporates tubelike conduits to allow for the flow of the cooling fluid through the core barrel, the FA array, and / or the FAs for efficient heat removal from the core. The core barrel, FA array, and / or FAs in the array are also configured with spaces into which and from which control rods comprising a neutron-absorbing material may be inserted and withdrawn to regulate and sustain the chain reaction during normal operation and into which the control rods may be inserted to abruptly shut down the chain reaction in emergency situations.

[0004] There are currently many different types and sizes of nuclear power plants using different types of nuclear fuel, reactor cores, cooling systems and cooling fluids, FAs, and fuel designs. The power plants are generally high capital cost (Cap Cost) infrastructure installations, which are complex to design, construct, and run, and are characterized bylevelized costs of energy (LCOEs) that are substantially larger than that of natural gas power plants and coal powered power plants absent carbon capture and storage (CCS) equipment. And whereas nuclear power plants are historically statistically safe, nuclear power plant accidents, when they occur, have a very high disruptive impact on the environment and society. The large impact is attested to by the accidents in Chernobyl (1986) in Russia, and Fukushima Daiichi (2011) in Japan which are characterized by an impact rank of 7 on the INES scale (International Nuclear and Radiological Event Scale) which is the highest rank for disruptive damage on the scale. The safety challenge is compounded by current technopolitical developments that have made inexpensive, highly destructive weapons relatively easily available to a burgeoning population of terrorist actors that might determine that nuclear power plants are appropriate targets of the weapons.

[0005] However, whereas nuclear power plants are expensive and perceived as prone to high risk accidents they are particularly attractive for providing electricity because they have an extremely low environmental impact compared to any conventional power plants and can be leveraged to effectively combat the global warming crisis.SUMMARY

[0006] An aspect of an embodiment of the disclosure relates to providing a nuclear power plant characterized by a relatively low Cap Cost, LCOE and enhanced safety.

[0007] In an embodiment, the power plant comprises a liquid lead cooled nuclear reactor that provides between about 2.5 MWth to about 4,000 MWth (megawatts-thermal) and converts the thermal energy to between about 1 MWe to about 1,500 MWe (megawatts- electric) using high temperature steam to drive a conventional steam turbine of a type used in combined cycle natural gas power plants The reactor comprises a core that burns low- enrichment conventional nuclear fuel, UO2 enriched to between 2% and 5% with U-235. Fuel pellets with the U-235 fuel may be enclosed in Zircaloy cladding fuel rods, which are bundled into FAs having an outer wall formed from a moderating material. Thickness and composition of the moderating material is configured to thermalize fast neutrons emitted during reactor operation by fission of mostly U-235 atoms. Optionally, the outer wall is a layered wall comprising a layer of Zirconium hydride (ZrHx) as moderating agent sandwiched between layers of Zircaloy or other suitable material . Hereinafter the reactor maybe referred to as a lead cooled thermal reactor (LTR) and the power plant as an LTR power plant.

[0008] Because an LTR reactor in accordance with an embodiment uses a liquid lead coolant, the reactor may use as a low, optionally ambient pressure pool type cooling system that is, optionally, substantially pipeless. The core and coolant may therefore be housed in a relatively thin walled reactor vessel and during operation the reactor may safely generate high temperature steam for driving a conventional steam turbine to produce electricity. Furthermore, the relatively simple cooling system and integration of moderating material in the reactor FAs walls allow the LTR reactor to be configured with a relatively small spatial footprint. The above noted structural attributes and use of conventional fuel results in an LTR power plant in accordance with an embodiment of the disclosure having a relatively small Cap Cost and low LCOE.

[0009] The LTR power plant is not only characterized by low cost features and small footprint but particularly enhanced safety features. The small footprint makes the LTR reactor a smaller and therefore less vulnerable target for malicious damage. And in the event of a cooling system breach, whether by accident or targeted damage, the low pressure cooling system and lead coolant’s high melting point that causes it to solidify upon contact with cooler surroundings helps to contain the breach and limit release of radioactive materials into the environment.

[0010] The advantageous cost and safety features of LTR power plants in accordance with an embodiment of the disclosure make the power plants particularly attractive for providing cost efficient, safe nuclear power for relatively small, localized populations and industry, and also for establishing distributed nuclear power infrastructure systems for large populations and industrial concentrations.

[0011] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.BRIEF DESCRIPTION OF THE FIGURE

[0012] Non-limiting examples of embodiments of the invention are described below with reference to figures attached hereto that are listed following this paragraph. Identicalstructures, elements or parts that appear in more than one figure are generally labeled with a same numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are chosen for convenience and clarity of presentation and are not necessarily shown to scale

[0013] Fig. 1 schematically shows a nuclear power plant for providing electricity, in accordance with an embodiment of the disclosure;

[0014] Fig. 2 schematically shows a core barrel comprising FAs in accordance with an embodiment of the disclosure;

[0015] Fig. 3 schematically shows a detailed cross section of an FA in accordance with an embodiment of the disclosure; and

[0016] Fig. 4 shows a bar graph comparing the Cap Cost and LCOE for different nuclear power plants with the Cap Cost and LCOE for a power plant in accordance with an embodiment of the disclosure.DETAILED DESCRIPTION

[0017] In the discussion, unless otherwise stated, adjectives such as “substantially” and “about” modifying a condition or relationship characteristic of a feature or features of an embodiment of the disclosure, are understood to mean that the condition or characteristic is defined to within tolerances that are acceptable for operation of the embodiment for an application for which it is intended. Wherever a general term in the disclosure is illustrated by reference to an example instance or a list of example instances, the instance or instances referred to, are by way of non-limiting example instances of the general term, and the general term is not intended to be limited to the specific example instance or instances referred to. The phrase “in an embodiment”, whether or not associated with a permissive, such as “may”, “optionally”, or “by way of example”, is used to introduce for consideration an example, but not necessarily a required configuration of possible embodiments of the disclosure. Unless otherwise indicated, the word “or” in the description and claims is considered to be the inclusive “or” rather than the exclusive or, and indicates at least one of, or any combination of more than one of items it conjoins. Whereas features and actions of flow diagrams shown in the figures and discussed in the specification are presented and discussed substantially in an ordered sequence of flow diagram blocks, the features and actions in a given flow diagram may be undertaken in an order other than that presented in the flow diagram.

[0018] Fig. 1 schematically shows an LTR power plant 20 comprising an LTR reactor 30 which generates and supplies high temperature steam to a balance of plant (BOP) 70 that uses the steam to produce electricity, in accordance with an embodiment of the disclosure.

[0019] In an embodiment, LTR power plant 20 optionally comprises a reactor building 22 having an underground, concrete reinforced well 24 that houses LTR reactor 30. Building 22 provides reactor 30 with enhanced protection against targeted attack and containment of radioactive debris in the event of damage to the reactor vessel. BOP 70 optionally comprises a conventional high temperature steam turbine 71, generator 72, and cooling system 74 for using the high temperature steam that BOP 70 receives from LTR reactor 30 to generate electricity.

[0020] In an embodiment, LTR reactor 30 optionally comprises a pool-type reactor design 32 comprising a reactor vessel 33 that contains a liquid metal coolant 34, such as lead or a eutectic alloy of lead generically referred to as “lead” a core barrel 35, and heat exchangers 37 having piping 38. Because liquid lead and liquid lead alloys have very high boiling temperatures, coolant system 32 may operate at relatively low and / or ambient internal pressures. Reactor vessel 33 is therefore optionally a relatively inexpensive, thin walled vessel formed in parts that are welded together rather than cast as a single piece.

[0021] A reactor core 40 seats in core barrel 35 on a coolant inlet matrix 36 at a bottom of the core barrel and optionally comprises a core basket 42 that holds an array 44 of FAs 50. In accordance with an embodiment, each FA 50 contains a plurality of fuel rods 52 (shown in Fig. 2 and 3) in a lumen defined by an FA wall 54 (shown in Fig. 2 and 3) comprising a moderating material. In accordance with an embodiment each fuel rod 52 packs a plurality of relatively inexpensive low enriched uranium U-235 (LEU) fuel pellets (not shown). The moderating material in the FA walls operates to thermalize the energy spectrum of neutrons emitted by fission, which not only enables LTR reactor to operate effectively with LEU and contribute to low LCOE of LTR 20 but also to facilitate configuring the LTR with a relatively small spatial footprint. Reactor 30 comprises a plurality of control rods 62 that are operated by actuators 60 to control a chain reaction in core 40 that generates heat to produce high temperature steam. Details of core 40, FA array 44, and FAs 50 are shown in Figs. 2 and 3 and are discussed below with reference to the figures.

[0022] During operation of LTR power plant 20 control rods 62 are inserted and withdrawn from core 40 by actuators 60 to maintain a critical chain reaction that generatesthe heat for producing the high temperature steam that reactor 30 provides to BOP 70. Liquid metal coolant 34 is circulated by natural convection and / or by mechanical and / or electromagnetic pumps (not shown) through core 40 and heat exchangers 37. The circulation of liquid metal coolant 34 removes heat from core 40 and transfers the heat to piping 38 in the heat exchangers where the heat generates high-temperature steam from water carried by the piping. The high-temperature steam is routed through headers 80 and piping 82 to BOP 70 where it drives conventional turbine 71 to generate electricity. After passing through turbine 71 to generate electricity the spent steam is condensed in BOP condenser 74 and the condensate returned via piping 82 to be reheated in reactor 30 and again transferred to BOP 70 to drive turbine 71. Solid and dashed arrows 100 and 101 respectively indicate direction of flow of the liquid metal coolant 34 circulating in reactor vessel 33. Arrows 104 and 105 in piping 82 respectively indicate direction of flow of high-temperature steam from reactor 30 to BOP 70 and flow direction of spent steam condensate from BOP 70 to reactor 30.

[0023] Fig. 2 schematically shows a perspective view of core 40 cutaway to show a crosssection 41 of the core in accordance with an embodiment of the disclosure. As noted above, core 40 optionally comprises a core basket 42 that holds an array 44 of FAs 50. An inset 110 in Fig. 2 schematically shows an enlarged portion of cross section 41 that illustrates features of FAs 50. In accordance with an embodiment, as shown in the inset, each FA 50 comprises an external, optionally hexagonal wall 54 formed from a moderating material. FA wall 54 defines a lumen 55 which contains a plurality of fuel rods 52, and optionally, at least one hollow tube 53 for housing sensors . Coolant 34 flows through the FA 50 between fuel rods 52.

[0024] Details of an FA 50 and labels for dimensions of features in an FA in accordance with an embodiment of the disclosure are conveniently illustrated in an enlarged cross section of an FA 50 shown in Fig. 3. In an embodiment FA 50 comprise JVrfuel rods 52 having diameter Dr.The fuel rods are arrayed in an array 44 with horizontal and diagonal pitch Prin lumen 55 of FA 50. Wall 54 is optionally a layered wall comprising a layer 54-1 comprising a moderating material bounded by at least one bounding layer 54-2, or as shown in Fig. 3 sandwiched between two bounding layers 54-2. FA wall 54 has an external side length FASand a thickness WT. Moderating layer 54-1 has a thickness MTand bounding layers 54-2 have an optionally same thickness BT.

[0025] By way of a non-binding numerical example, FA 50 may comprise a number JFrof fuel rods 52 equal to about 37, each fuel rod having diameter Drequal to about 10 mm (millimeters). Fuel rods 52 in the FA may be arrayed in array 44 with rod pitch Prequal to about 13 mm. FA wall 54 has an external side length FASequal to about 40 mm and thickness WTequal to about 12 mm. In an embodiment moderating layer 54-1 comprises ZrHxand has thickness MTequal to about 10 mm. Bounding layers 54-2 are formed from Zircaloy and have thickness BTequal to about 1 mm. In an embodiment core basket 42 has a diameter equal to about 300 cm and supports a pluralityof FAs equal to about 600.

[0026] A power plant in accordance with an embodiment of the disclosure similar to power plant 20 configured to provide about 200 MWe and comprising a reactor 30 having FAs 50 and a core 40 characterized by dimensions and materials given in the previous paragraph may comprise a core barrel 35 having wall thickness 3 centimeters (cm) and outer diameter 3 meters (m). Reactor vessel 33 that houses core barrel 35 may have wall thickness equal to about 5 cm, outer diameter equal to about 4 m and hold about 40,000 liters of liquid lead coolant. Concrete reinforced well 24 of reactor building 22 that houses LTR reactor 30 may have a diameter equal to about 7 m and depth below ground equal to about 6 m. It is estimated that power plant may be characterized by a Cap Cost equal to about US $800,000,000 and LCOE equal to about US $60 / MWh (megawatt-hour).

[0027] Fig. 4 shows a stacked bar graph 200 that compares the Cap Cost, LCOE and components of LCOE (Cap Cost; Operating and Maintenance expense (Opex); and refueling costs) for a plurality of different prior art nuclear power plants and an LTR in accordance with an embodiment of the disclosure characterized by the numerical values given above. The prior art nuclear power plants include: a High Temperature Gas Cooled Reactor (HTGR) power plant; Sodium Cooled Fast Reactor (SFR) power plant; and a Lead Cooled Fast Reactor (LFR) power plant; and a Light Water Reactor (LWR) power plant. Costs for LCOE and LCOE components of the plants are given in US 2024 dollars per megawatt hour ($2024 / MWh) along an ordinate of the graph and Cap Costs for the power plants are given in US 2024 dollars per kilowatt ($ / kW) in a text box along an abscissa of the graph. As graph 200 shows an LTR power plant in accordance with an embodiment of the disclosure is characterized by substantial cost savings in LCOE and Cap Costs relative to the LCOE and Cap Costs of the prior art power plants shown in the graph.

[0028] As noted in the discussion above, substantial cost savings characterizing an LTR power plant in accordance with an embodiment are provided by the combination of using a liquid lead or lead eutectic alloy as a coolant in the power plant’s LTR reactor and FAs that incorporate a moderator to thermalize neutrons generated by fission of nuclear fuel that the reactor bums. The lead coolant is highly efficient at heat transfer, has a high melting and boiling temperature, which enables the LTR reactor to use a relatively simple pool type coolant system that circulates the coolant by convection and / or by pump action and facilities generating steam at high temperatures between by way of example 500-600 degrees centigrade. The high temperature steam in turn enables the LTR power plant to drive an inexpensive conventional steam turbine of a type used in combined cycle natural gas power plants to produce electricity. The FAs incorporating a moderator in accordance with an embodiment enables the LTR power plant to bum low cost “off-the-shelf’ low enriched LT- 235 to generate heat that produces the high temperature steam.

[0029] The features of the LTR power plant, individually or in any combination of more than two of the features that contribute to low Cap Cost and LCOE, also support small spatial footprint configurations of an LTR reactor conveniently and inexpensively housed in a relatively small structurally robust building characterized by enhanced resistance to seismic, accidental or targeted damage.

[0030] Descriptions of embodiments of the disclosure in the present application are provided by way of example and are not intended to limit the scope of the disclosure. The described embodiments comprise different features, not all of which are required in all embodiments. Some embodiments utilize only some of the features or possible combinations of the features. Variations of embodiments of the disclosure that are described, and embodiments comprising different combinations of features noted in the described embodiments, will occur to persons of the art. The scope of the invention is limited only by the claims.

Claims

CLAIMS1. A nuclear reactor, the reactor comprising:a core comprising a moderating material and an array of fuel assemblies (FAs), each FA containing a bundle of fuel rods packed with a nuclear fuel, wherein the moderating material thermalizes neutrons emitted by the fuel when the fuel in the core is burned in a chain reaction; anda cooling system that circulates a liquid metal coolant to remove heat from the core generated by the chain reaction.

2. The nuclear power reactor according to claim 1, wherein each FA in the array has a wall that defines a lumen in which the bundle of fuel rods are contained, and the wall comprises the moderating material.

3. The nuclear power reactor according to claim 2, wherein the FA wall is a layered wall comprising a layer of the moderating material sandwiched between bounding layers.

4. The nuclear power reactor according to claim 3, wherein the bounding layers consists essentially of a zirconium alloy (Zircaloy) having trace amounts of any one or any combination of two or more of tin, iron, chromium nickel and / or oxygen.

5. The nuclear power reactor according to claim 3, wherein the layer of moderating material has thickness between about 2 mm (millimeters) and about 40 mm.

6. The nuclear power reactor according to claim 1, wherein the moderating material comprises a Zirconium hydride (ZrHx).

7. The nuclear power reactor according to claim 1, wherein the moderating material comprises Yttrium hydride (YHX).

8. The nuclear power reactor according to claim 1, wherein the cooling system comprises a pool-type reactor design.

9. The nuclear power reactor according to claim 1, wherein the cooling system circulates the liquid metal coolant by convection.

10. The nuclear power reactor according to claim 1, wherein the cooling system circulates liquid metal coolant by forced circulation.

11. The nuclear power reactor according to claim 1, wherein the liquid metal coolant and the core are contained in a reactor vessel having a vessel wall thickness between 3 cm and 10 cm (centimeters).

12. The nuclear power reactor according to claim 11, wherein the reactor vessel has an outer diameter between 3.5 m (meters) and 6 m.

13. The nuclear power reactor according to claim 11, wherein the vessel is formed in pieces that are welded together.

14. The nuclear power reactor according to claim 1, wherein the liquid metal coolant comprises lead.

15. The nuclear power reactor according to claim 1, wherein the liquid metal coolant comprises Lead-Bismuth Eutectic.

16. The nuclear power reactor according to claim 1, wherein the nuclear fuel comprises uranium oxide (UO2 ) enriched with Uranium-235 (U-235).

17. The nuclear power reactor according to claim 16 wherein the UO2 is enriched to between 2% and 5% with U-23518. The nuclear power reactor according to claim 1, wherein the cooling system comprises a heat exchanger and circulates the liquid metal coolant to deliver heat removed from the core to the heat exchanger generate steam.

19. The nuclear power reactor according to claim 18 wherein the generated steam is high temperature steam having a temperature suitable to drive a conventional steam turbine of a type used in combined cycle natural gas or coal power plant.

20. A nuclear power plant comprising a reactor according to claim 18 and a balance of plant (BOP) having a turbine and a generator, wherein the BOP receives and uses the steam to drive the turbine and generator to produce electricity.

21. A nuclear power plant comprising a reactor according to claim 20 wherein the turbine is a conventional steam turbine of a type used in a combined cycle natural gas or coal power plant.

22. A nuclear power plant according to claim 20 or claim 21 wherein the nuclear power plant generates between 1 MWe to 1,500 MWe (megawatts-electric).

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