Mixed-spectrum molten salt reactor

Abstract

To provide a mixed-spectrum molten salt reactor with an improved atypical core geometry providing safer operational advantages.SOLUTION: A mixed-spectrum molten-salt reactor with an atypical core geometry has a primary containment vessel 20. A reactor core 12 is housed in the primary containment vessel, and the reactor core with an atypical geometry holds a fuel salt. A blanket region is formed within the primary containment vessel and surrounds the reactor core, and the blanket region includes a blanket salt 14.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] Related Applications This application claims priority to U.S. Provisional Application No. 63 / 537,932, entitled "FAST SPECTRUM MOLTEN-SALT REACTOR (MSR)," filed September 12, 2023, which is incorporated herein by reference in its entirety. This patent application claims the benefit under 35 U.S.C. § 119(e) of the aforementioned provisional application.

[0002] The present invention relates generally to nuclear reactors, and more particularly, the present invention relates to mixed spectrum molten salt reactors having atypical core geometries. [Background technology]

[0003] Molten Salt Reactors (MSRs) are a type of nuclear fission reactor in which the reactor fuel also serves as the primary reactor coolant. In an MSR, the reactor fuel is a mixture of molten salt and fissile material. Molten salt reactors operate by dissolving fissile material in molten ionic salts, typically chloride or fluoride salts. The fissile molten salt produced is then circulated, either passively or actively, through a vessel called the core where the nuclear reaction occurs, and the resulting heated salt is circulated through a heat exchanger. Structures within the core may be made of light elements, including beryllium, carbon, hydrogen-containing solids, hydrogen-containing liquids, etc., that can slow down or "moderate" neutrons from the fission reaction so that their kinetic energy is similar to the energy in the thermal motion of the particles that make up the fissile material. These reactors are called "thermal spectrum" MSRs. Structures within the core also form channels for the molten salt / molten salt to flow through. Alternatively, some molten salt reactors forego the use of light elements in the core and opt for a core vessel without interspersion structures. In these designs, the fission neutrons are not moderated and the designs are called "fast spectrum" molten salt reactors (FSMSRs).

[0004] The basic operating principle of a molten salt reactor is that the fuel mixture is kept in a molten state, thus eliminating potential thermal runaway or nuclear meltdown situations in the event of operational disturbances that are always present in water-cooled reactors. The fuel mixture is designed to be vented from the reactor core to the containment vessel in an emergency situation without pumping. Here, the lack of moderator material (in the case of the thermal spectrum) or a change in fuel shape (in the case of the fast spectrum) will stop the reaction. Furthermore, no hydrogen release occurs, eliminating the risk of a hydrogen explosion. MSRs operate at or near atmospheric pressure, rather than 75-150 times atmospheric pressure found in a typical light water reactor (LWR). The lower operating pressure reduces the need and cost of the reactor pressure vessel used in MSRs. Low pressure MSRs do not require expensive steel containment vessels, piping, and safety equipment. However, most MSR designs place the radioactive fluid in direct contact with pumps and heat exchangers. Gaseous fission products (Xe and Kr) are largely insoluble in the fuel salts and can be safely captured as they bubble out of the fuel rather than increasing pressure inside the fuel tubes as occurs in conventional reactors. Whereas conventional reactors are shut down and taken offline for refueling, MSRs can be refueled online while in operation, providing continuous uninterrupted operation. MSR operating temperatures are approximately 700 °C (1,292 °F), significantly higher than conventional LWRs at approximately 300 °C (572 °F). The ability to refuel while the MSR is in operation, as well as the higher operating temperatures, increase power generation efficiency / availability and process heating opportunities for the generation of steam to run generators.

[0005] Molten salt reactors offer many advantages, some of which are mentioned above, but MSRs also have challenges and drawbacks. Circulating fuel salt designs can require full remote maintenance, as radionuclides dissolved in the fuel come into contact with equipment such as pumps and heat exchangers. MSR designs often rely on expensive nickel alloys to contain the molten salt, and these alloys can be prone to embrittlement under high neutron fluxes. Molten salts used in MSRs can present corrosion hazards, and the oxidation state of these molten salts must be carefully controlled to manage the corrosion hazard. An example of a corrosion hazard is the dissolution of chromium by liquid fluoride thorium salts above 700 °C (1,292 °F), which can endanger stainless steel components. Neutron radiation can alter common alloying agents such as Co and Ni, shortening their life, and can cause damage to solid moderator materials, limiting core life. Lithium salts such as FLiBe can penetrate stainless steels, causing embrittlement, and may justify the use of Li-7 to reduce tritium generation, which can be lost into the environment. Summary of the Invention [Problem to be solved by the invention]

[0006] Although there have been many advances in reactor technology, there remains a need for improved molten salt reactors that offer safer operating advantages over existing water-cooled reactors. [Means for solving the problem]

[0007] According to an embodiment of the present disclosure, a mixed spectrum molten salt nuclear reactor is provided having a primary containment vessel, the primary containment vessel containing a reactor core and a fuel salt, and a blanket region within the primary containment vessel surrounding the reactor core, the blanket region including a blanket salt.

[0008] The present invention will now be described in further detail with reference to the following drawings, which are intended to illustrate certain aspects of the invention, but should not be construed as limiting the practice of the invention. [Brief description of the drawings]

[0009] [Figure 1A] 4 illustrates neutron flux distribution along different planes in a core according to an embodiment of the present invention. [Figure 1B] 4 illustrates neutron flux distribution along different planes in a reactor core according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram of an integrated configuration of a mixed spectrum molten salt reactor (MXMSR) in accordance with an embodiment of the present invention. [Diagram 3] FIG. 1 is a diagram of a loop configuration of a mixed spectrum molten salt reactor (MXMSR) in accordance with an embodiment of the present invention. [Figure 4A] FIG. 2 is a top cross-sectional view of a primary reactor vessel illustrating the shape of the primary core as an ellipsoid shape with an elliptical cross section, in accordance with an embodiment of the present invention. [Figure 4B] FIG. 2 is a top cross-sectional view of a primary reactor vessel illustrating the shape of the primary core as a biconcave shape of a hyperbolic cross section in accordance with an embodiment of the present invention. [Figure 4C] FIG. 2 is a top cross-sectional view of a primary reactor vessel illustrating the shape of the primary core as a parallelepiped shape of rectangular slab-like cross-section in accordance with an embodiment of the present invention. [Figure 5A] FIG. 13 is a side view of a control element in the form of a control plate for use in an embodiment of the present invention. [Figure 5B] FIG. 5B is an exploded view of FIG. 5A, in which the boron carbide plates are sandwiched between the stainless steel plates. [Figure 6] FIG. 5B is a front view of the control plate of FIG. 5A positioned within a stainless steel frame having a set of rails. [Figure 7] 1 illustrates a rack and pinion system with an electromagnetic actuator for raising and lowering the control plate in an embodiment of the present invention. [Figure 8]1 is a cross-sectional side view of a typical nuclear reactor having a removable cover and control plate in accordance with an embodiment of the present invention. [Figure 9] 9 is a graph of the nominal neutron spectrum in the typical reactor vessel of FIG. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] It should be understood that like reference numerals refer to like elements throughout the several views.

[0011] A mixed spectrum molten salt reactor (MXMSR) is provided. The MXMSR has a primary containment vessel and a core housed within the primary containment vessel. The core has an irregular shape containing a fuel salt. The irregular shape of the core has a parallelepiped shape with a rectangular slab-like cross section, a biconcave shape with a hyperbolic cross section, an hourglass shape with a hyperbolic cross section, or an ellipsoid shape with an elliptical cross section. A blanket region within the primary containment vessel surrounds the core, the blanket region containing a blanket salt. The fuel salt includes a mixture of actinides recovered from spent nuclear fuel recycling as a fissile material driver, and a carrier salt including a chloride or fluoride salt mixture having high actinide-halide solubility and a sufficiently low melting point. The fuel in the carrier salt is composed of halide compounds of uranium, plutonium, neptunium, americium, and curium of various compositions.

[0012] The blanket region has a chamber or compartment on the side of the core where neutron leakage is intentionally allowed. The chamber or compartment is adapted for insertion and removal of control elements including plates, rods, or drums. The control plates are formed of a compound of a neutron absorbing material such as boron, alloyed with or sandwiched between a set of stainless steel plates, and formed into a plate design that conforms to the shape of the surrounding region of the core shape including rectangular plates, parabolic cross section plates, hyperbolic cross section plates, and are free to move within the control plate compartment. The stainless steel control plates are held above the compartment using electromagnetic force from electromagnets. The control elements are passively inserted without operator intervention when the control signal is lost or a shutdown signal is received.

[0013] The inner surface of the primary containment vessel is coated with a neutron reflector material which is graphite or one of beryllium oxide, zirconium hydride, yttrium hydride, molten lead, or molten Pb-Bi eutectic encapsulated in a coating made of a material corresponding to the primary containment vessel.

[0014] The blanket region further includes a neutron moderating material including one of zirconium hydride or deuteride, yttrium hydride or deuteride, sodium hydroxide or deuterium oxide, lithium hydroxide or deuterium oxide, and silicon carbide encapsulated in a graphite block surface treated with pyrolytic carbon at high temperatures to reduce surface roughness and porosity, or in a cladding material made of a material corresponding to the primary containment vessel.

[0015] Transmutation ports are provided for either the production of desired isotopes or the removal of isotopes. These ports accept specially formed targets of the material of interest. If desired, the isotopes can also be dissolved in the blanket salts and uniformly distributed over time in the blanket region where transmutation can occur.

[0016] The reactor further includes a core heat exchanger in fluid communication with the core and a blanket heat exchanger in fluid communication with the blanket region, the core is connected to the core heat exchanger via ducts or channels, fuel salt is circulated through either natural or forced convection via a core pump, blanket salt is circulated through the blanket heat exchanger via a blanket pump, and coolant flows from both the core and blanket heat exchangers are combined and circulated through a secondary heat exchanger.

[0017] The reactor has a removable cover, and the removable cover and core provide a machined space to accommodate inlet and outlet ducts / piping, including a fuel inlet, a fuel outlet, a blanket inlet, a blanket outlet, and a drainage channel.

[0018] The mixed spectrum molten salt reactor embodiments of the present invention differ from existing core designs in that an atypical core geometry is utilized. Typical MSR designs use a core region having a single cylindrical shape with a circular axial cross section. While the invention disclosed herein can take the form of simple concentric cylinders, disclosed design embodiments for the atypical core region include, but are not limited to, a parallelepiped shape with a rectangular slab-like cross section, a biconcave shape with a hyperbolic cross section, an hourglass shape with a hyperbolic cross section, an ellipsoid shape with an elliptical cross section, and the like. In an embodiment, the primary containment vessel houses the core vessel, and the volume of space outside the core forms a "blanket" region.

[0019] Furthermore, while existing MSR designs have core geometries that minimize neutron leakage, embodiments of the disclosed design utilize core geometry to optimize neutron leakage so that the escaping neutrons can be used in the blanket region to convert fertile material to fissile material and perform transmutation to create or destroy specific isotope targets. This neutron balance is made possible by the atypical geometry of the core combined with the high neutron yield of transuranic fuel in the fast neutron spectrum. In the above mentioned geometries, the intensity of neutron radiation, characterized by the flow rate of neutrons, known as neutron flux, is uniquely distributed. For a given geometric shape, the dimensions are selected such that the neutron flux at the boundaries is reduced. The dimensions in the other axis are varied until a critical shape is achieved. An example of the nominal fast neutron flux distribution is shown in Figures 1A and 1B, which show the neutron flux distribution along different planes in an embodiment of the disclosed MXMSR.

[0020] In an embodiment, the core region is homogenous and has no structure within the volume enclosed by the vessel walls. The fuel in the carrier salt is composed of halide compounds of uranium, plutonium, neptunium, americium, and curium of various compositions. The salt in the blanket region may utilize halide compounds of natural or depleted uranium, or thorium as fertile material, or other halide compounds for transmutation.

[0021] Atoms in any material undergo interactions with neutrons, and most interactions are physical collisions in which kinetic energy and momentum are exchanged. This fact, combined with the knowledge that neutrons are lighter than any atomic nucleus except H-1 hydrogen, means that all atoms are neutron "reflectors". In an embodiment of the present invention, neutron leakage along one of the axes of the core region provides an opportunity to control the chain reaction by varying the number of neutrons that can be reflected back to the core from the blanket region. That is, suitable materials that can absorb neutrons can be used in the periphery adjacent to the surface where neutron leakage is intentionally promoted for the regulated neutron flux. Thus, an embodiment of the disclosed design includes chambers or compartments in the sides of the core vessel where neutron leakage is intentionally allowed. These compartments allow the insertion of control elements, for example by lifting plates, rods, drums, etc.

[0022] In an embodiment, the control element and the housing section are arranged such that the control element can move within the section without hindrance under all operating conditions. In a particular embodiment, the control element is a plate made of a compound of boron, such as boron carbide, or any other suitable neutron absorber, alloyed with or sandwiched between plates of stainless steel, and formed into a plate design that fits the shape of the peripheral region of the core shape, including, by way of example, rectangular plates, parabolic cross-section plates, hyperbolic cross-section plates, etc., and can move freely within the control plate section. In this embodiment, the plate may be housed within an overpack made of stainless steel or some other suitable material. In this embodiment, the plate may also be divided into two or more segments, each occupying a space within the section adjacent to the other segment and covering a corresponding segment of the surface around the core region. Each segment can move independently to control the rate of the chain reaction.

[0023] In embodiments, the control elements may be designed to be passively inserted without operator intervention when the control signal is lost or a shutdown signal is received. In a particular embodiment, a control plate having a stainless steel housing is held above the compartment using electromagnetic forces. Upon receiving a Safety Control Rod Axeman or Safety Cut Rope Axeman (SCRAM) signal or if the facility loses station power, the electromagnets disengage and the control plate immediately drops into the control compartment, stopping the chain reaction.

[0024] The disclosed design embodiments use primarily a fast spectrum in the reactor core region. However, the blanket region provides an opportunity to utilize the most suitable neutron spectrum to facilitate nuclear transmutation. Since for most atomic nuclei the probability of neutron interaction increases as the kinetic energy of the neutron decreases, it is desirable to take advantage of this property to increase nuclear transmutation. In the disclosed design embodiments, the blanket region provides a structure that contains a neutron moderating material.

[0025] In an embodiment, the core region provides a system of devices for circulating the molten salt. These circulation devices can take the form of one or more pumps and multiple ducts connected to an integral heat exchanger. Alternatively, the molten salt may be moved outside the core region using multiple nozzles and pumps forming a loop connected to the heat exchanger. The ducts and nozzles are incorporated into the vessel design to prevent the formation of eddies / vortexes in the molten salt flow for all normal operating conditions. Heat generated in the reactor is efficiently transferred from the salt in the core region to the secondary coolant fluid through one or more heat exchangers. The salt may be transported by either natural convection or forced flow. The heat exchangers are designed to optimize the heat transfer from the hot salt to the coolant fluid while also providing a barrier to the movement of fission products. In the disclosed designs, some embodiments of the heat exchanger configurations may include shell-and-tube, tube-in-tube, printed circuit, etc. The heat exchangers may also direct the hot salt and coolant liquid to have a desired flow configuration. Some embodiments of the flow configurations may be co-current, counter-current, cross-flow, cross / counter-flow, etc. In an embodiment, a similar heat exchanger may be used to cool the blanket salt, but only a small portion of the power is generated in the blanket region. The coolant fluid streams for both the core and blanket heat exchangers may pass through a single secondary heat exchanger whose working fluid may be any of air, water, helium, carbon dioxide, nitrogen, nitrogen tetroxide (N2O4), aluminum chloride (AlCl3), etc.

[0026] Where a range of values ​​is provided, it is to be understood that the range is intended to encompass not only the endpoints of the range, but also intermediate values ​​thereof as expressly included within the range and as varied by the last significant digit of the range. By way of example, the recited range of 1 to 4 is intended to include 1 to 2, 1 to 3, 2 to 4, 3 to 4, and 1 to 4.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description of the present invention in this specification are for the purpose of describing particular embodiments only and are not intended to be limiting of the present invention.

[0028] Unless otherwise indicated expressly or by context, the following terms are used herein as set forth below.

[0029] As used in the description of this invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0030] Also, as used herein, "and / or" refers to and includes any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative ("or").

[0031] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0032] FIG. 2 shows a diagram of a nuclear reactor 10 in a monolithic configuration. In this approach, the core 12, blanket / blanket salt 14, and associated core heat exchanger 16 and blanket heat exchanger 18 are enclosed within a single primary containment vessel 20. The core vessel 20 is connected to the heat exchangers (16, 18) via ducts 22, and the fuel salt 13 can be circulated by either natural or forced convection via a core pump 24 and / or a blanket pump 26. The core 12 includes an annular baffle structure 15 that forms a downcomer from the cold leg of the heat exchanger to allow for thermally-hydraulic efficient flow. The blanket salt 14 circulates through its own blanket heat exchanger 18 via a blanket pump 24, where the core vessel 20 itself forms a diverter to allow for thermally-efficient flow. The coolant flows from both the core heat exchanger 16 and the blanket heat exchanger 18 are combined and circulated through a secondary heat exchanger 28. The main advantages of the monolithic configuration from a reactor physics standpoint are: (1) lower overall fissile loading, (2) higher delayed neutron precursor retention in the neutron critical region of the core 12, and (3) a compact profile.

[0033] FIG. 3 shows a diagram of a reactor 40 in a loop configuration. The main feature that distinguishes the loop reactor approach from the integral reactor approach is that the heat exchangers (16, 18) are mounted outside the primary containment vessel 20′. This means that the fuel 13 and blanket salt 14 circulate through the respective heat exchangers via pipes, either by forced or natural convection. Such an arrangement requires a larger fissile material load, since at any given moment some of the salt resides in the piping away from the heat exchangers (16, 18) and the core 12′. As a natural consequence, most of the delayed neutron precursors undergo decay with the emission of their neutrons outside the core 12′. The advantages of this approach are: (1) better thermal-hydraulic performance over a wider range of reactor parameters; and (2) easier maintenance of the reactor.

[0034] 4A-4C are top cross-sectional views of embodiments (50, 70, 80) of the primary reactor vessel (20, 20') coated with a neutron reflector 52 on the inner surface of the wall of the primary reactor vessel (20, 20'), respectively showing the atypical shapes of the primary core 12 as an ellipsoid shape 12'' with an elliptical cross section, a biconcave shape 12''' with a hyperbolic cross section, and a parallelepiped shape 12'''' with a rectangular slab cross section. The primary vessel (20, 20') may be constructed from a variety of compatible metal alloys. Some iron-based alloys include, by way of example, Inconel-625, Hastelloy-N, and the like. Molybdenum-based alloys such as TZM, Haynes-214, Monel, MoNiCr, and the like, may also be used in the construction of the primary reactor vessel (20, 20'). The primary reactor vessel (20, 20') is protected from neutron embrittlement by the inclusion of the neutron reflector 52. The neutron reflector 52 must be compatible with the molten salt environment. Graphite can be used without cladding since it does not react with the molten salt. Alternatively, beryllium oxide, zirconium hydride, yttrium hydride, molten lead, molten Pb-Bi eutectic, etc. may be used in a coated enclosure made of the same material as the primary vessel. The choice of neutron reflector 52 depends on the neutron spectrum tuned for the as-built reactor and the choice of primary vessel material to prevent radiation induced expansion or activation products of concern.

[0035] The three atypical core vessels (12'', 12''', 12'''') may be made from the same alloys as described for the primary vessel (20, 20') above. It should be understood that the materials used to construct the primary vessel and the core vessel need not necessarily be the same. The core vessel is exposed to high levels of fast neutron flux, which limits its operational life. Therefore, the core vessel is designed to be replaceable if necessary.

[0036] The core vessel (12'', 12''', 12'''') holds the fuel salt 13. Various compositions of fuel salt 13 can be used, including, by way of example only, but not limited to: LiF-ThF4-PuF3 LiF-ThF4-UF4-PuF3 with U enriched to 20% by weight of U-235 NaCl-PuCl3 NaCl-MgCl2-PuCl3 NaCl-ThCl4-PuCl3 LiCl-KCl-PuCl3. These compositions are representative of examples in the literature and have been subjected to neutron calculations by the inventors. PuCl3 can be replaced by a mixture of transuranium elements. Exemplary compositions of transuranium elements include, but are not limited to, the following: 39.5% uranium (including up to 1% U-235 isotope by weight), 2% neptunium, 36.5% plutonium, 6.5% americium, and 0.2% curium by weight. The isotopic composition of the individual elements depends on the properties of the spent nuclear fuel from which the transuranium elements are sourced.

[0037] The volume outside the core vessel (12'', 12''', 12'''') but enclosed by the primary containment (20, 20') is filled with a blanket salt 14. The carrier salt for the blanket may or may not be the same as the fuel salt 13 composition. Some blanket salt 14 compositions include, by way of example only, but are not limited to: NaCl-ThCl4 NaCl-UCl3 LiF-ThCl4 LiF-ThCl4.

[0038] Certain "target" elements for transmutation, either for the production of a desired isotope or for the removal of an isotope, may be formed into a suitable "target" that may be dissolved in the blanket salt 14 or introduced into the neutron flux in the blanket region via transmutation port 58. One such example is the transmutation of I-129, which may be incorporated into the blanket salt 14 in the form of sodium iodide or lithium iodide. Similarly, the production of Co-60 may be accomplished by forming a target of cobalt-59 and introducing it into the flux in the blanket salt 14 via transmutation port 58.

[0039] The blanket region may or may not incorporate neutron moderation structures. Various different embodiments of neutron moderation structures (54, 82) are shown in Figures 4A-4C. The illustrated moderation structures (54, 82) are independent of the geometry of the core vessel (12", 12'", 12"") and are shown for illustrative purposes only; more than one type of geometry for the moderator blocks may be used in the same reactor.

[0040] The moderator structures or blocks are made from light elements. Graphite can be used without the need for cladding. In this case, the graphite blocks are subjected to a surface treatment with pyrolytic carbon at high temperatures to reduce surface roughness and porosity. Various other mitigation materials can be used with appropriate cladding, including, but not limited to, zirconium hydride or deuteride, yttrium hydride or deuteride, sodium hydroxide or deuteride, lithium hydroxide or deuteride, silicon carbide, and the like. The moderator structures or blocks are held in place using grid spacers 56, which are positioned and held in place via a hold-down plate that may or may not be a permanent part of the removable vessel cover. The fixation by the grid spacers 56 and hold-down plate ensures that the moderator structures or blocks cannot move during reactor operation, preventing changes in reactivity caused by changes in the relative position or distance of the moderator blocks from the core vessel.

[0041] The periphery of the core vessel (12'', 12''', 12'''') is provided with a control compartment 60 for inserting control elements. FIG. 5A shows one possible embodiment of a control element in the form of a control plate 90. In this case, plate 90 made of boron carbide 92 is sandwiched between plates of stainless steel 94, as best seen in the exploded view 5B of FIG. 5A.

[0042] The control plate 90 is formed as a single continuous unit. As shown in FIG. 6, the control plate 90 may then be placed into a stainless steel frame 96 with a set of rails 98. The control section is provided with tracks for the rails 98, which allow the control plate 90 to be smoothly inserted and removed. FIG. 7 shows a rack and pinion system 100 for raising and lowering the control plate 90, controlled by a drive mechanism that illustratively includes an electromagnetic (EM) drive 102. The EM drive 102 receives control signals from an operator. In the event of a loss of power to the station, the EM drive 102 disengages and the control plate 90 drops into the control section, with the rails providing a defined path of travel and the rack and pinion system 100 providing some inertia to control the rate of drop.

[0043] FIG. 8 is a side view of a general embodiment 110 of the disclosed inventive design. The containment vessel 112 has a removable cover 114 on top. The space above the vessel is made of shielding material and is part of the facility housing. The removable cover 114 incorporates a vessel reflector block 116, which may be made of graphite or stainless steel molded to be part of the cover 114. The removable cover 114 and the core 12 provide a machined space that can accommodate inlet and outlet ducts / piping, including a fuel inlet 118, a fuel outlet 120, a blanket inlet 122, a blanket outlet 124, and a drain 126. The inlet and outlet ducts / piping allow for the movement of fuel salt. As the reactor is fueled with liquid, a drain line 126 is provided at the bottom of the core vessel 12 so that fuel salt can be drained from the reactor during routine maintenance and in the event of an abnormal event. The cover 114 also incorporates a hold down plate 128 which connects to the grid spacers on top of the moderator blocks (54, 82). The control plate 90 drops into a control plate section 130. Lifting ports 132 are used to lift the core vessel 12 out of the containment vessel 112. The lifting ports 132 can be fitted with screw hooks for lifting the core vessel 12 during both installation and replacement. A blanket 14 surrounds the core 12.

[0044] FIG. 9 is a graph showing nominal neutron spectra for the disclosed reactor design. The neutron flux shown is for a typical design with a neutron interaction signature with peaks and valleys that change as the reactor composition changes. In the graph shown in FIG. 9, the flux is normalized to 1. In an embodiment of the reactor of the present invention, the core vessel, including the fuel salt, exhibits a fast (or hard) neutron spectrum. Meanwhile, the blanket region, including the blanket salt and neutron moderator, exhibits a thermalized (or softer) neutron spectrum. The fast neutron flux in the fuel salt is an order of magnitude greater than the blanket salt. Similarly, the thermal neutron flux in the blanket salt is more than two orders of magnitude greater than the fuel salt.

[0045] The present invention has utility as a mixed spectrum molten salt reactor (MXMSR) designed to utilize a mixture of actinides recovered from spent nuclear fuel recycling as a fissile material propellant. The disclosed reactor design may operate using chloride or fluoride salt mixtures as carrier salts with high actinide-halide solubility and sufficiently low melting points. Non-limiting examples of chlorides include NaCl, NaCl-KCl, LiCl-KCl, etc., and non-limiting examples of fluorides include LiF, LiF-NaF, etc. An embodiment of the MXMSR design may have two separate regions: a core region and a blanket region. The core region is where the fission reaction primarily occurs in the carrier salt containing the fissile material. The blanket region is the surrounding region where the carrier salt containing the material for neutron activation transmutation occurs.

[0046] It is seen that the present invention improves performance compared to fast spectrum molten salt reactors by using an atypical core geometry. Furthermore, while existing MSR designs have core geometries that minimize neutron leakage, embodiments of the disclosed design utilize core geometry to optimize neutron leakage so that the escaping neutrons can be used in the blanket region to convert fertile material to fissile material and perform transmutation to create or destroy specific isotope targets. This neutron balance is made possible by the atypical core geometry combined with the high neutron yield of the transuranium fuel in the fast spectrum design.

[0047] Although preferred embodiments of the present invention have been disclosed herein, it should be understood that modifications of these particular embodiments of the invention can be made without departing from the scope of the invention as found in the appended claims.

[0048] Various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims.

[0049] The foregoing description illustrates certain embodiments of the invention, but is not meant to be a limitation on its practice. It is intended that the following claims, including all equivalents thereof, define the scope of the invention.

Claims

1. 1. A mixed spectrum molten salt nuclear reactor, comprising: A primary containment vessel; a reactor core contained within the primary containment vessel, the reactor core containing a fuel salt; a blanket region within the primary containment vessel surrounding the reactor core, the blanket region including a blanket salt; 1. A mixed spectrum molten salt reactor comprising:

2. 10. The nuclear reactor of claim 1, wherein the core has an irregular shape, the irregular shape comprising one of a parallelepiped shape with a rectangular slab-like cross-section, a biconcave shape with a hyperbolic cross-section, an hourglass shape with a hyperbolic cross-section, or an ellipsoid shape with an elliptical cross-section.

3. 2. The nuclear reactor of claim 1, wherein the fuel salt comprises a mixture of actinides recovered from spent nuclear fuel recycling as a fissile material driver and a carrier salt comprising a chloride or fluoride salt mixture having high actinide-halide solubility and a sufficiently low melting point.

4. 4. The nuclear reactor of claim 3, wherein the fuel in a carrier salt is comprised of halide compounds of various compositions of uranium, plutonium, neptunium, americium, and curium.

5. 4. The nuclear reactor of claim 3, wherein the chloride mixture includes at least one of NaCl, NaCl--KCl, and LiCl--KCl.

6. The nuclear reactor of claim 3, wherein the fluoride mixture includes at least one of LiF and LiF-NaF.

7. 10. The nuclear reactor of claim 1, wherein the blanket salts include halogenated compounds of natural or depleted uranium, thorium as a fertile fuel material, or other halogenated compounds for nuclear transmutation.

8. The blanket salt is NaCl-ThCl ４ , NaCl-UCl ３ , LiF-ThCl ４ , or LiF-ThCl ４ The nuclear reactor of claim 7 further comprising:

9. 10. The nuclear reactor of claim 1, wherein the blanket region further comprises a chamber or compartment on a side of the core where neutron leakage is intentionally allowed.

10. 10. The nuclear reactor of claim 9, wherein the chamber or compartment is adapted for insertion and removal of control elements comprising plates, rods, or drums.

11. 11. The nuclear reactor of claim 10, wherein the control plate is formed from a neutron absorbing element that is alloyed with or sandwiched between a set of plates and formed into a plate design that conforms to the shape of a peripheral region of the core shape including rectangular plates, parabolic cross-section plates, and hyperbolic cross-section plates and is free to move within the control plate section.

12. 12. The nuclear reactor of claim 11, wherein the control plate is held above the compartment using electromagnetic force from an electromagnet.

13. 11. The nuclear reactor of claim 10, wherein the control element is passively inserted without operator intervention upon loss of a control signal or upon receiving a shutdown signal.

14. 10. The nuclear reactor of claim 1, wherein an inner surface of the primary containment vessel is coated with a neutron reflector material.

15. 15. The nuclear reactor of claim 14, wherein the neutron reflector material is graphite.

16. 15. The nuclear reactor of claim 14, wherein the neutron reflector material comprises one of beryllium oxide, zirconium hydride, yttrium hydride, molten lead, or molten Pb-Bi eutectic and is enclosed within a cladding made of a material corresponding to the primary containment vessel.

17. 10. The nuclear reactor of claim 1, wherein target elements for the production of desired isotopes or removal of isotopes are either dissolved in the blanket salts or formed into targets that are introduced into the neutron flux in the blanket region.

18. The nuclear reactor of claim 1 , wherein the blanket region further comprises a neutron moderating material.

19. 20. The nuclear reactor of claim 18, wherein the neutron moderating material comprises graphite blocks surface treated with pyrolytic carbon at high temperatures to reduce surface roughness and porosity, zirconium hydride or deuteride, yttrium hydride or deuteride, sodium hydroxide or deuteride, lithium hydroxide or deuteride, and silicon carbide.

20. a core heat exchanger in fluid communication with the core; and a blanket heat exchanger in fluid communication with the blanket region; 2. The nuclear reactor of claim 1, wherein the core connects to the core heat exchanger through ducts, the fuel salt circulates through either natural or forced convection via core pumps and / or blanket pumps, the blanket salt circulates through the blanket heat exchanger via the blanket pumps, and coolant flows from both the core heat exchanger and the blanket heat exchanger are combined and circulated through a secondary heat exchanger.

21. 21. The nuclear reactor of claim 20, wherein the core heat exchanger and the blanket heat exchanger are contained within the primary containment vessel.

22. 10. The nuclear reactor of claim 1 further comprising a removable cover, said removable cover and said core providing machined spaces to accommodate inlet and outlet ducts / plumbing including a fuel inlet, a fuel outlet, a blanket inlet, a blanket outlet, and a drainage channel.

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