Systems and methods for nuclear core assembly receptacle leakage diverter

Abstract

Flow channels are formed into a nuclear reactor core receptacle and provide a flow path for leaking primary coolant. The flow path redirects the leaking coolant from an upwardly vertical direction, in which the mass flow would impart a lift off force to a core assembly seated within the receptacle, to a horizontal flow path direction which maintains hydraulic balance of the core assembly. The flow channels in the nuclear reactor core receptacle provide a passive measure to allow hydraulic hold down of the core assemblies even in the absence of mechanical hold downs.

Description

SYSTEMS AND METHODS FOR NUCLEAR CORE ASSEMBLY RECEPTACLELEAKAGE DIVERTERGOVERNMENT LICENSE RIGHTS

[0001] This invention was made with government support under DOE Cooperative Agreement No. DE-NE0009054 awarded by the U.S. Department of Energy. The government has certain rights in the invention.CROSS REFERENCE

[0002] The present application claim benefit of priority to U.S. Provisional Patent Application No. 63 / 621,104, filed January 15, 2024, titled “SYSTEMS AND METHODS FOR NUCLEAR CORE ASSEMBLY RECEPTACLE LEAKAGE DIVERTER,” the entire contents of which is hereby incorporated by reference.BACKGROUND

[0003] In a sodium-cooled fast reactor (“SFR”), the main reactor components are a reactor vessel filled with a liquid sodium coolant and a reactor core. In some cases, an SFR is a once-through fast reactor that runs on subcritical reload fuel that is bred up and burned in situ. The reactor core is immersed in the sodium pool in the reactor vessel. In one design, in the center of the core are a few rods of enriched uranium (U-235), surrounded by rods of depleted uranium (U-238). The U-235 serves as an initiator, kick starting a traveling wave reaction - a slow-moving chain reaction of parallel waves of fission traveling through the uranium rods. These parallel waves initiate in the center of the core, slowly consuming the fuel and generating heat in the core. This mode of operation is sometimes visualized as a reactor in which waves that breed and then bum fissionable material would travel relative to the fuel. However, in many cases, fission plants also include so-called ‘standing wave’ designs in which consumed rods near the center of the reactor core are swapped with unconsumed uranium rods from the periphery of the reactor core as an alternative to propagating the reaction radially outward through static rods.

[0004] The sodium coolant is used to remove the heat from the core. The sodium coolant flows through the core assemblies, some of which may be fuel assemblies, by entering a nozzle of the core assembly and flowing about the fuel pins within the core assemblies to remove heat therefrom. A containment vessel surrounds the reactor vessel to prevent loss of sodium coolant in case of an unlikely leak from the reactor vessel. The pumps circulate primary sodium coolant between the reactor core and intermediate heat exchangers located in the pool. These heat exchangers have non-radioactive intermediate sodium coolant on the other side of the heat exchanger. Heated intermediate sodium coolant is circulated to steam generators that generate steam to drive turbines of electrical generators.

[0005] In theory, some SFR fission plants require no fuel reprocessing, use depleted or natural uranium as their primary fuel, require only a small amount of enriched uranium at start-up, and never need refueling. This core longevity depends on the size of the initial charge of the uranium and on the fuel burn-up achieved during reactor operation.

[0006] The reactor core may contain several types of core assemblies, including core assemblies containing fissile fuel, fertile fuel, reflectors, neutron absorbers, among others. The forces of the flowing sodium on the core assemblies typically imparts an upward force on the core assemblies that tends to lift the core assemblies from their mounting sockets. In some cases, the pressure differential on the core assemblies from the flowing sodium imparts sufficient lifting force on the core assemblies that one or more core assemblies may lift out of the mounting receptacle, a cascade of events is likely to happen, which may even include the loss of control of the nuclear reaction.

[0007] Some reactor designs include ring seals between the receptacle and the core assembly nozzle to prevent flowing sodium from flowing between the core assembly and the receptacle into which the core assembly is mounted. This sodium leakage between the core assembly and the receptacle imparts significant lifting forces on the core assembly.However, the ring seals may wear out and are typically made of the same material as the receptacle, and the frictional forces degrades both the ring seals and the receptacle, both of which are very difficult to repair or replace during the life of the nuclear reactor.Furthermore, should the ring seals fail catastrophically, this may cause the assembly to lose hydraulic balance and be lifted.

[0008] In some SFR nuclear reactor designs, an upper hold down is provided to constrain the core assemblies from lifting up.

[0009] It would be advantageous if the core assemblies could rely on hydraulic hold down to maintain balance across the core assemblies so the assemblies stay seated, which can be used to provide a redundant, passive, and efficient solution to mitigating core assembly liftoff. These, and other advantages, will become apparent to those of skill in the art by reference to following description, figures, and claims.SUMMARY

[0010] According to some implementations, the benefits described herein a provided by a receptacle within a nuclear reactor core configured to receive a nozzle of a core assembly, the receptacle including a cylindrical hollow body having an upper end and a lower end, and further having an inner diameter and an outer diameter; a mounting portion near the upper end, the mounting portion having an upper surface and a second diameter larger than the outside diameter of the cylindrical hollow body; and a plurality of flow channels formed into the upper surface of the mounting portion, the flow channels configured to allow primary coolant to flow therein.

[0011] The cylindrical hollow body may have an upper edge adjacent the inner diameter, and wherein the upper edge is beveled. In some cases, the bevel is provided at an angle that is inclined with respect to a longitudinal axis of the cylindrical hollow body.

[0012] In some instances, the plurality of flow channels are formed into the beveled upper edge. The plurality of flow channels may be formed in a radial directed with respect to the cylindrical hollow body. As such, in some cases, the plurality of flow channels direct a flowing liquid from having a substantially vertical flow direction to a substantially horizontal flow direction. In some examples, the plurality of flow channels form at least two sections, a first section having a vertical component of flow and a second section defining a horizontal flow.

[0013] The flow channels may have a semi-circular cross section, a V-shaped cross section, and / or a rectangular shaped cross section. The flow channels may be formed by a material removal process during manufacture, such as by a machining operation.

[0014] In some cases, a sleeve or liner is disposed within the hollow cylindrical body, the sleeve having a plurality of holes around a circumference of the sleeve that align with the plurality of flow channels. The plurality of holes in the sleeve may each have a first area that is smaller than a second cross-sectional area defined by each of the plurality of flow channels. In this way, the fluid is encouraged to flow through the holes and into the flow channels instead of directed vertically at the assembly.

[0015] The receptacle may further include an upper seal disposed above the plurality of holes in the sleeve, the upper seal configured to provide a seal between an inner surface of the sleeve and a nozzle inserted therein.

[0016] The receptacle may further include a lower seal disposed below the plurality of holes in the sleeve, the lower seal configured to provide a seal between an inner surface of the sleeve and a nozzle inserted therein. In some cases, the upper seal and / or the lower seal is one or more of a cylinder seal and a labyrinth seal. The upper seal may include multiple seals, such as 2, 3, 4, or more seals. The multiple seals may be the same type of seal or may be different types of seals. For example, the upper seal may include one or more cylinder seal and one or more labyrinth seals.

[0017] In some cases, the plurality of holes in the sleeve are circular, while the plurality of holes may alternatively be elliptical in shape.

[0018] In some examples, the sleeve is formed of a nickel-chromium alloy.

[0019] According to some embodiments, a method of reducing lift off forces on a core assembly in a nuclear core includes the steps of providing a receptacle configured to receive a core assembly therein; and forming, on a top surface of the receptacle, flow channels that redirect a flow of flowing liquid from a vertical direction to a horizontal direction. This flow redirection thus balances the hydraulic forces on the core assembly, and changes the hydraulic forces from a vertical force to a radial force.

[0020] The step of forming flow channels may include machining grooves into the top surface of the receptacle.

[0021] The method may further include providing a sleeve within the receptacle and forming, in a wall of the sleeve, a plurality of holes. The holes may be formed perpendicular to a longitudinal axis of the sleeve, or may be formed at an angle other than perpendicular with respect to the longitudinal axis.

[0022] The plurality of holes may be positioned to redirect flowing fluid from within the sleeve, through the holes, and into the flow channels. In some cases, this causes a fluid flow path to transition from vertical within the sleeve, to inclined as the fluid passes through the holes and into the flow channels, to horizontal within the flow channels.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are part of the disclosure and are incorporated into the present specification. The drawings illustrate examples of embodiments of the disclosure and, in conjunction with the description and claims, serve to explain, at least in part, various principles, features, or aspects of the disclosure. Certain embodiments of the disclosure are described more fully below with reference to the accompanying drawings. However, various aspects of the disclosure may be implemented in many different forms and should not be construed as being limited to the implementations set forth herein. Like numbers refer to like, but not necessarily the same or identical, elements throughout.

[0024] The following drawing figures, which form a part of this application, are illustrative of described technology and are not meant to limit the scope of the technology as claimed in any manner, which scope shall be based on the claims appended hereto.

[0025] FIG. 1 illustrates, in a block diagram form, some of the basic components of a sodium-cooled fast reactor, in accordance with some embodiments.

[0026] FIG. 2 is a schematic sectional view of a core of a sodium-cooled fast reactor, in accordance with some embodiments.

[0027] FIG. 3 is an exploded view of a core assembly, in accordance with some embodiments.

[0028] FIG. 4 is an enlarged sectional view of an inlet nozzle and core support structure interface, in accordance with some embodiments.

[0029] FIG. 5 is a partial cutaway view of an inlet nozzle and core support structure showing the receptacle, sleeve, and core component, in accordance with some embodiments.

[0030] FIG. 6A is a plan view of a receptacle with flow channels, in accordance with some embodiments.

[0031] FIG. 6B is a front view of a receptacle with flow channels, in accordance with some embodiments.

[0032] FIG. 7 is a schematic partial cutaway view of a receptacle and sleeve, in accordance with some embodiments.

[0033] FIG. 8 is a partial front cross-sectional view illustrating a flow path from within the sleeve to a location outside of the sleeve, in accordance with some embodiments.DETAILED DESCRIPTION

[0034] The disclosure sets forth example embodiments and, as such, is not intended to limit the scope of embodiments of the disclosure and the appended claims in any way. Embodiments have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined to the extent that the specified functions and relationships thereof are appropriately performed.

[0035] FIG. 1 illustrates, in a block diagram form, some of the basic components of a sodium-cooled fast reactor (SFR) fission plant 100. While an SFR may be used through the description as an example type of reactor technology, it should be appreciated that the concepts presented herein may be equally applicable to other types of reactors. In some cases, the concepts presented in the following description are directly appliable to other forms of sodium-cooled fast reactors (SFRs), such as, for example, traveling wave reactors, modular reactors, micro reactors, among others, and the disclosure and appended claims should not be limited to any specific nuclear reactor, fuel source, coolant type, or reactor architecture.

[0036] In general, the SFR fission plant 100 includes a reactor core 102 containing a plurality of fuel assemblies (not shown). The core 102 is disposed within a pool 104 holding a volume of liquid sodium coolant 106. The pool 104 is referred to as a hot pool and has a sodium temperature higher than that of a surrounding cold pool 108 (due to the energy generated by the fuel assemblies in the reactor core 102), which also contains liquid sodium coolant 106. The hot pool 104 is separated from the cold pool 108 by the redan 110. A headspace 112 above the level of the sodium coolant 106 is filled with an inert cover gas, such as argon. The reactor vessel 114 surrounds the reactor core 102, hot pool 104, and coldpool 108, and is sealed with a reactor head 116. The reactor head 116 provides various access points into the interior of the reactor vessel 114.

[0037] The size of the reactor core 102 is selected based on a number of factors, including the characteristics of the fuel, desired power generation, available reactor 100 space, and so on. Various examples of an SFR fission plant may be used in low power (around 300 MWe - around 500 MWe), medium power (around 500 MWe - around 1000 MWe), and high power (around 1000 MWe and above) applications, as required or desired. The performance of the reactor 100 may be improved by providing one or more reflectors, not shown, around the core 102 to reflect neutrons back into the core 102. Additionally, fertile and fissile nuclear assemblies may be moved (or “shuffled”) within and about the core 102 to control the nuclear reaction occurring therein.

[0038] The sodium coolant 106 is circulated within the vessel 114 via a primary sodium coolant pump 118. The primary coolant pump 118 draws sodium coolant 106 from the cold pool 108 and injects it into a plenum below the reactor core 102. The coolant 106 is forced upward through the core and is heated due to the fission reactions taking place within the reactor core 102. Heated coolant 106 exits the upper end of the core 102 and enters an intermediate heat exchanger(s) 120 from the hot pool 104, and exits the intermediate heat exchanger 120 and re-enters the cold pool 108. This primary coolant loop 122 thus circulates sodium coolant 106 entirely within the reactor vessel 114.

[0039] The intermediate heat exchanger 120 incorporates a segment of a closed liquid sodium loop that is physically separated from the primary sodium pools 106 and 108 at all times (i.e., intermediate and primary sodium are never co-mingled). The intermediate heat exchanger 120 transfers heat from the primary coolant loop 122 (fully contained within the vessel 114) to an intermediate coolant loop 124 (that is only partially located within the vessel 114). The intermediate heat exchanger 120 passes through the redan 110, thus bridging the hot pool 104 and the cold pool 108 (so as to allow flow of sodium 106 in the primary coolant loop 122 therebetween). In an example, four intermediate heat exchangers 120 are distributed within the vessel 114. Alternatively, two or six intermediate heat exchangers 120 are distributed within the vessel 114, or some other number of heat exchangers 120 may be distributed about the reactor vessel 114.

[0040] The intermediate coolant loop 124 circulates sodium coolant 126 that passes through pipes into and out of the vessel 114, via the reactor head 116. An intermediate sodium pump 128 located outside of the reactor vessel 114 circulates the sodium coolant 126 to a power generation system 123. Heat is transferred from the sodium coolant 106 of the primary coolant loop 122 to the sodium coolant 126 of the intermediate coolant loop 124 in the intermediate heat exchanger 120. The sodium coolant 126 of the intermediate coolant loop 124 passes through a plurality of tubes 130 within the intermediate heat exchanger 120. These tubes 130 keep the sodium coolant 106 of the primary coolant loop 122 separate from the sodium coolant 126 of the intermediate coolant loop 124, while transferring heat energy therebetween.

[0041] A direct heat exchanger 132 extends into the hot pool 104 and provides cooling to the sodium coolant 106 within the primary coolant loop 122, usually in case of emergency. The direct heat exchanger 132 is configured to allow sodium coolant 106 to enter and exit the heat exchanger 132 from the hot pool 104. The direct heat exchanger 132 may have a similar construction to the intermediate heat exchanger 120, where tubes 134 keep separate the NaK (Sodium -Potassium) of the primary coolant loop 122 from the direct heat exchanger coolant (NaK) 136 of the direct reactor coolant loop 138, while transferring heat energy therebetween.

[0042] Other ancillary reactor components (both within and outside of the reactor vessel 114) include, but are not limited to, pumps, check valves, shutoff valves, flanges, drain tanks, etc., that are not depicted but would be apparent to a person of skill in the art. Additional penetrations through the reactor head 116 (e.g., a port for the primary coolant pump 118, inert cover gas and inspection ports, sodium processing, and cover gas ports, etc.) are not depicted. A control system 140 is utilized to control and monitor the various components and systems which make up the reactor 100.

[0043] Broadly speaking, this disclosure describes configurations that improve the performance of the reactor 100 described in FIG. 1. Specifically, examples, configurations, and arrangements of flow control systems that are utilized to direct sodium in ways that minimize, or at least reduce, the liftoff force of the core assemblies. In particular, the systems, components, and methods described herein reduce the liftoff force caused by sodium that leaks into a space between the core assembly and the receptacle that holds thecore assembly. These features are shown and described in more detail below with reference to the following figures.

[0044] FIG. 2 is a schematic sectional view of a core 200 of an SFR. The core 200 is schematically shown and includes a central core region 202 having a plurality of core assemblies 204. The core assemblies 204 may include fissile nuclear fuel assemblies, fertile nuclear fuel assemblies, shield assemblies, reflector assemblies, control assemblies, and standby shutdown assemblies, or material testing assemblies. In general, the contents of the assemblies (e.g., fissile material, control material, etc.) identifies the particular assembly. The components of the assemblies that hold such material may be identical, such as to facilitate shuffling the core assemblies around the core to any location, as desired. A peripheral core region 206 includes in-vessel storage pots 208. Throughout the life of the core 200, the fissile nuclear fuel assemblies and fertile nuclear fuel assemblies (as well as certain other assemblies) are shuffled between the central core region 202 and the peripheral core region 206. This is performed at various stages of core life as required or desired to initiate, maintain, accelerate, or terminate nuclear reactions or power generation and / or for safety reasons.

[0045] The assemblies 204 are received by an upper plate 210 of a core support structure 212 at locations sized and configured to receive the core assemblies 204. Sodium coolant is pumped into a plenum 214 disposed below the upper plate 210 and flows upward into the core assemblies 204, where it is heated by the nuclear reactions taking place within the core 200. Structures that channel the flow of sodium through the core 202 and into the various assemblies are described below.

[0046] FIG. 3 is an exploded view of a core assembly 300. The assembly 300 includes an elongate duct 302 having an axis A. The duct 302 has a hexagonal cross section. A handling socket 304 with an internal flow passage is secured to a first end 306 of the duct 302 and has internal or external features that allow it to be grasped by mechanisms within the reactor vessel to lift, lower, and otherwise move the assembly 300 into, out of, or within the core.

[0047] An inlet nozzle 308 is secured to a second end 310 of the duct 302. A plurality of bearing rings 312 and retaining rings 314 are used to attach the handling socket 304 and inlet nozzle 308 to the duct 302. A plurality of lock plates 316 (two in this example) and a plurality of pin strip rails 318 may be included proximate an end of the inlet nozzle 308.Together, the lock plates 316 and pin strip rails 318 connect the pin bundle 320 to the inlet nozzle 308. Seal rings 322 and a flow restrictor 324 may also be incorporated. The nozzle 308 defines a plurality of coolant inlet windows 326 that are in flow communication with an interior flow chamber (not shown) that extends through the nozzle 308. Thus, the windows 326 provide a path for sodium to flow into the nozzle 308 and into the duct 302 to flow around the pin bundle 320 disposed therein. Sodium flow continues out of the handling socket 304.

[0048] FIG. 4 is a sectional view of an example flow control system 500 showing the interface between an inlet nozzle 308 and core support structure 400. The inlet nozzle 308 is seated in and engaged with a receptacle 402 of the core support structure 400. The nozzle 308 may have an oblique surface 408 that provides a funnel-shaped transition between a first diameter of the nozzle 308 and a second, larger diameter, of the duct 302. In some cases, the oblique surface 408 rests against the receptacle 402, while in other cases, the oblique surface 408 may be disposed above the receptacle 402. The interface between the oblique surface 408 and the receptacle 402 may be determined based upon the design of the receptacle and how far into the receptacle the core assemblies 300 are configured to be inserted. In some cases, there is a gap between the nozzle 308 and the receptacle 402 as will be described in further detail below.

[0049] A base 404 of the receptacle 402 defines a passage 406 that provides a flow path for sodium to pass through the core assembly 300 and exit to the reactor sodium hot pool. The receptacle 402 may extend above the core support structure 400, or may be even therewith. Below the core support structure 400 is a coolant flow control system 500 that includes a masking element 502 and a flow stack 504 disposed therein. In this example, the masking element 502 is in the form of a sleeve. The flow stack 504 may include an outer housing 506 and at least one flow control assembly 508 disposed therein. The flow control system 500 is described in more detail below.

[0050] Suitable flow systems may utilize a standardized flow stack along with different masking sleeves at various locations below the core support structure. The masking features may be secured to or integral with the core support structure while the flow stacks may be integral with a core assembly or discrete therefrom. By utilizing a standardized flow stack, manufacturing costs, inter-assembly differences, and risk of incorrect assembly are decreasedbecause of the standardized parts. A masking sleeve allows each flow stack to be used in any location, over a wide range of flow conditions such as those encountered in an SFR. The flow stack may be integral with a core assembly inlet nozzle or may be fixed within the masking sleeves. The flow stack may include multiple pressure stages and inlets for each stage. The masking sleeve may be disposed about the flow stack so as to create selective inlets to the flow stages. This arrangement allows for varying pressure drops according to the selective inlets exposed, which in turn dictates the number of pressure drop stages a flow will encounter. This allows for standardization of fuel assemblies while creating unique flow conditions for different core locations.

[0051] For an SFR, this may be advantageous as it allows a core assembly to be installed in, or relocated at any time to (e.g., shuffled to), a different core position while still receiving an appropriate metered flow rate (which can vary from location to location). In examples where the flow stacks are integral with the inlet nozzle, the flow stacks are connected to a removable component (e.g., the core assembly). As such, lifetime effects (such as erosion damage) can be examined and mitigated as needed. For a "re-core" operation, where all core assemblies are exchanged for those of a different design, the replacement assemblies do not have to conform to the flow zones of the original core, allowing more flexibility in the design of future cores, if required or desired.

[0052] FIG. 5 illustrates a partial cutaway view of an inlet nozzle 308 and core support structure 400 showing the receptacle 402, sleeve 502, and a core component 300, in accordance with some embodiments. In some embodiments, the receptacle 402 has a sleeve 502 inserted therein which is configured to receive the nozzle 308 of the core assembly 300. In some cases, the sleeve 502 is formed of a hard material, which in some embodiments may be a nickel-chromium alloy, such as one of the alloys sold by Huntington Alloys Corp, under the tradename Inconel. In some instances, the sleeve 502 is designed to last the entire lifetime of the nuclear reactor core and may not typically be designed to be replaced.

[0053] The nozzle 308, on the other hand, may be replaced from time to time as the reactor core is refueled and core assemblies are inserted or withdrawn from the reactor core. Thus, in some cases, the nozzle 308 is formed of a material that is softer than the sleeve 502 material to promote preferential wearing of the nozzle 308 in lieu of the sleeve 502.

[0054] The sleeve 502 may be held down within the receptacle 402. In some cases, the sleeve 502 is formed integrally with the receptacle 402 and is fastened in place, such as by an interfering structure 505 that prevents the sleeve 502 from withdrawing from the receptacle 402. The interfering structure may be any suitable type of cooperating components, and may include, for example, a shelf, a groove, a boss, a protrusion, a pocket, fasteners, welding, a key fit, or other structure. In the illustrated example, a cup 510 is securely held by the receptacle. A bypass tube 516 allows sodium to flow throughout the core assembly. A pin 514 may be provided to inhibit relative motion between the receptacle 402 and the cup 510. A portion of the sleeve 502 may be captured by the cup 510, and may inhibit the sleeve from withdrawing from the receptacle 402.

[0055] The nozzle 308 may have flow holes 512 formed therein, as described herein, to allow coolant to flow through the core assembly 300. As coolant enters the side of the receptacle 402 and into the core assembly 300, leakage of the coolant may cause coolant to flow in a space between the nozzle 308 and the sleeve 502. As this leakage flows upwardly under pressure, it may impinge against the core assembly, such as against sloped outer surface 518 of the core assembly 300 and generate vertical forces sufficient to lift the core assembly 300 from the receptacle 402 and the sleeve 502. This lifting force, if sufficient to displace the core assembly 300, may have consequences, such as reduced flow and a cascading effect on the reactivity of the nuclear reactor, among others.

[0056] FIG. 6A illustrates a plan view of a receptacle 402 with flow channels 602, while FIG. 6B is a front view of the receptacle 402 showing the flow channels 602. The receptacle 402 may include a generally hollow cylindrical body 604 having a hollow 606 therein, the hollow 606 sized and configured for receiving a nozzle of a core assembly. The receptacle 402 may additionally have a beveled inner top edge 608 that slopes inwardly to help guide a core assembly being inserted therein. The receptacle has a top surface 610 and a shoulder 612 that may engage with the core support structure (400 of FIG 5) to secure the receptacle to the core support structure.

[0057] A series of flow channels 602 may be formed into the top surface 610 of the receptacle. The flow channels 602 may be formed in a radial direction with respect to the cylindrical body 604, such that flow through the flow channels 602 is in a radial direction.

[0058] The flow channels 602 may be formed to have any suitable cross sectional shape, but in some cases is a rounded, curved, or rectangular cutout in the top surface of the receptacle 402. In some cases, the flow channels 602 are formed by a material removal process during manufacturing of the receptacle, and may be formed by machining. The material removal may be a low tolerance process in that a high degree of precision is not required in order to provide a flow channel to divert leaking coolant.

[0059] The flow channels 602 may be spaced a predetermined distance, or angular offset, with respect to adjacent flow channels 602, and in some cases, 16, 20, 24, 28, or 32 flow channels or more may be provided regularly spaced around the periphery of the receptacle. The flow channels 602 may additionally be formed into the beveled inner top edge 608 which provides a smooth flow path that diverts the leaking coolant from a vertical flow path, to an inclined flow path, and eventually, to a horizontal flow path.

[0060] FIG. 7 is a schematic partial cutaway view of a receptacle 402 and sleeve 502, in accordance with some embodiments. The sleeve 502 is configured with a series of through holes 702 around its circumference. The holes 702 allow fluid from within the sleeve to flow through the holes to a location exterior to the sleeve. At least some of the holes 702 in the sleeve may line up with flow channels 602 formed in the receptacle 402. The holes 702 in combination with the flow channels 602 thus provide a fluid flow path for fluid that has leaked to a location between the nozzle and the sleeve 502, and further, provides a flow path that diverts the flow of coolant in a direction that does not impart lift off forces to the core assembly.

[0061] The diversion flow path is shown by arrows 704, that show flow from within the sleeve 502 being directed through the holes 702 and into the flow channels 602. In some cases, the holes are significantly larger than the gap between the sleeve 502 and the nozzle to encourage a low resistance flow path for the coolant. Similarly, the flow channels 602 may be significantly larger than the gap between the sleeve 502 and the nozzle to encourage leaking coolant to flow through the flow channels 602. In addition, seals may be provided in the gap between the sleeve 502 and the nozzle to further encourage fluid flow through the holes 702 and the flow channels 602. In some cases, the holes 702 are uniform in size and may be formed as circles, ellipses, ovals, rectangles, rectangular with rounded corners, or other suitable shape. In some cases, the holes 702 have an area that is commensurate withthe area of the flow channel 602. In some cases, the holes 702 have a cross sectional area that is smaller than the cross-sectional area of the flow channel 602. This configuration may provide a pressure drop at the flow channel 602 which further encourages leaking coolant to flow along the flow channel 602. In some cases, the holes 702 are formed to be larger in diameter than the gap between the nozzle and the sleeve 502 in order to promote fluid flow through the holes 702. In some cases, the holes may be sized to be about 200%, or 300%, or 400%, or 500%, or 600%, or 700% or more of the size of the gap between the nozzle and the sleeve. For example, where the gap between the nozzle and sleeve is on the order of 2mm, the holes may be formed with a diameter of 4mm - 14mm. In those embodiments that may not have circular holes, the minor dimension (e.g., minor radius of an oval, or smaller side of a rectangular cutout) may be 4mm - 14mm.

[0062] The flow channels 602 may be formed to have a cross-sectional area that is larger than the holes in order to promote the bending flow while introducing a pressure drop. As shown, the flow channels are formed below the top surface of the receptacle 402. Initially, the flow channels 602 cause a vertical component of the flow which then transitions to a horizontal flow path. The holes 702 in the sleeve are below the top plate and the flow channels 602 are formed to be at a similar, or the same, vertical location with respect to the holes in the sleeve 502.

[0063] FIG. 8 is a partial front cross-sectional view illustrating a flow path from within the sleeve to a location outside of the sleeve, in accordance with some embodiments. The fluid flow 704 can be seen initially inside the sleeve 502, where it flows through the holes 702 formed in the sleeve and the flows through the flow channels 602 in the receptacle 402. While the illustrated example shows that the holes are formed radially, or in other words, are formed to be perpendicular to a longitudinal axis of the sleeve, the holes could be formed at and angle other than perpendicular. For instance, where the beveled edge of the receptacle is formed with a 45 degree bevel angle, the holes could be formed (e.g., drilled) at a 45 degree angle so that the flow path through the sleeve aligns with the flow channels formed in the beveled edge of the receptacle. Such a configuration may further reduce pressure differential to encourage the fluid to flow through the holes and into the flow channels, thereby redirecting the flowing fluid from a vertical direction to a horizontal direction.

[0064] In some examples, a first seal 802a or set of seals may be provided below the holes 702. This further encourages the leaking coolant to flow through the holes 702 and through the flow channels 602. A second seal 802b or set of seals may be provided above the holes 702. In some cases, seals are provided below the holes 702 and above the holes 702 to encourage the leaking coolant to flow through the holes 702 and along the flow channels 602.

[0065] The seals may be any suitable type of seal, but in some cases may be one or more of labyrinth seals, piston rings, cylinder seals, or other type of seal that inhibits fluid from flowing past the seal. In some cases, a labyrinth seal is made by forming grooves or channels in a surface of the sleeve, or in the nozzle, or both. The grooves or channels impart a turbulent fluid flow on the fluid flowing thereby, thus causing an increased pressure and a resistance to flow. A piston seal is a generally annular seal that contacts both the sleeve and the nozzle. The piston seal may be formed of a compliant material, or may be formed of a hard material, such as Inconel, steel, or some other suitable material. The piston seal may be carried by the sleeve, or by the nozzle.

[0066] The provision of a flow path that encourages leaking coolant to be diverted from a vertical direction to a horizontal direction to reduce liftoff forces on a core assembly provides an efficient, passive, and redundant safety feature. A pressure drop due to the seals in combination with the flow redirection reduces reliance on the seal alone to reduce liftoff forces and may aid in reducing metal shavings from building with the seals. In some cases, the preferential wearing of the nozzle may cause metal shavings to build up within the lower seal which can reduce its efficacy. Consequently, having a redundant and passive structure to redirect the leaking coolant flow increases reliability and reduces any risks of the core assemblies lifting out of the receptacle, even without any additional mechanical constraints. Accordingly, the weight of the core assembly in combination with hydrodynamic forces is sufficient to maintain a core assembly in its fully seated position with the receptacle. The foregoing description of embodiments results in hydraulic balance across core assemblies so they stay seated within their respective receptacles.

[0067] The foregoing description of specific embodiments will so fully reveal the general nature of embodiments of the disclosure that others can, by applying knowledge of those of ordinary skill in the art, readily modify and / or adapt for various applications such specificembodiments, without undue experimentation, without departing from the general concept of embodiments of the disclosure. Therefore, such adaptation and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. The phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the specification is to be interpreted by persons of ordinary skill in the relevant art in light of the teachings and guidance presented herein.

[0068] The breadth and scope of embodiments of the disclosure should not be limited by any of the above-described example embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0069] Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations could include, while other implementations do not include, certain features, elements, and / or operations. Thus, such conditional language generally is not intended to imply that features, elements, and / or operations are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and / or operations are included or are to be performed in any particular implementation.

[0070] Unless otherwise noted, the terms “connected to” and “coupled to” (and their derivatives), as used in the specification, are to be construed as permitting both direct and indirect (i.e., via other elements or components) connection. In addition, the terms “a” or “an,” as used in the specification, are to be construed as meaning “at least one of.” Finally, for ease of use, the terms “including” and “having” (and their derivatives), as used in the

[0071] The specification and annexed drawings disclose examples of systems, apparatus, devices, and techniques that may provide control and optimization of coolant flow through core assemblies. It is, of course, not possible to describe every conceivable combination of elements and / or methods for purposes of describing the various features of the disclosure, but those of ordinary skill in the art recognize that many further combinations and permutations of the disclosed features are possible. Accordingly, various modifications may be made to the disclosure without departing from the scope or spirit thereof. Further, other embodiments ofthe disclosure may be apparent from consideration of the specification and annexed drawings, and practice of disclosed embodiments as presented herein. Examples put forward in the specification and annexed drawings should be considered, in all respects, as illustrative and not restrictive. Although specific terms are employed herein, they are used in a generic and descriptive sense only, and not used for purposes of limitation.

[0072] From the foregoing, it will be appreciated that, although specific implementations have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the appended claims and the elements recited therein. In addition, while certain aspects are presented below in certain claim forms, the inventors contemplate the various aspects in any available claim form. For example, while only some aspects may currently be recited as being embodied in a particular configuration, other aspects may likewise be so embodied. Various modifications and changes may be made as would be obvious to a person skilled in the art having the benefit of this disclosure. It is intended to embrace all such modifications and changes and, accordingly, the above description is to be regarded in an illustrative rather than a restrictive sense.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A receptacle within a nuclear reactor core configured to receive a nozzle of a core assembly, the receptacle comprising: a cylindrical hollow body having an upper end and a lower end, and further having an inner diameter and an outer diameter; a mounting portion near the upper end, the mounting portion having an upper surface and a second diameter larger than the outside diameter of the cylindrical hollow body; and a plurality of flow channels formed into the upper surface of the mounting portion, the flow channels configured to allow primary coolant to flow therein.

2. The receptacle as in claim 1, wherein the cylindrical hollow body has an upper edge adjacent the inner diameter, and wherein the upper edge is beveled.

3. The receptacle as in claim 2, wherein the plurality of flow channels are formed into the beveled upper edge.

4. The receptacle as in claim 2, wherein the plurality of flow channels direct a flowing liquid from having a substantially vertical flow direction to a substantially horizontal flow direction.

5. The receptacle as in claim 1, wherein the plurality of flow channels form at least two sections, a first section having a vertical component of flow and a second section defining a horizontal flow.

6. The receptacle as in claim 1, wherein the flow channels have a semi-circular cross section.

7. The receptacle as in claim 1, wherein the flow channels are formed by a material removal process.

8. The receptacle as in claim 1, further comprising a sleeve disposed within the hollow cylindrical body, the sleeve having a plurality of holes around a circumference of the sleeve that align with the plurality of flow channels.

9. The receptacle as in claim 8, wherein the plurality of holes each having a first area that is smaller than a second cross-sectional area defined by each of the plurality of flow channels.

10. The receptacle as in claim 8, further comprising an upper seal disposed above the plurality of holes, the upper seal configured to provide a seal between an inner surface of the sleeve and a nozzle inserted therein.

11. The receptacle as in claim 8, further comprising a lower seal disposed below the plurality of holes, the lower seal configured to provide a seal between an inner surface of the sleeve and a nozzle inserted therein.

12. The receptacle as in claim 10, wherein the upper seal is one or more of a cylinder seal and a labyrinth seal.

13. The receptacle as in claim 8, wherein the plurality of holes are circular.

14. The receptacle as in claim 8, wherein the plurality of holes are elliptical.

15. The receptacle as in claim 8, wherein the sleeve is formed of a nickelchromium alloy.

16. A method of reducing lift off forces on a core assembly in a nuclear reactor core, comprising the steps of: providing a receptacle configured to receive a core assembly therein; and forming, on a top surface of the receptacle, flow channels configured to redirect a flow of flowing liquid within the receptacle from an upwardly vertical direction to a horizontal direction.

17. The method of claim 16, wherein forming flow channels comprises machining grooves into the top surface of the receptacle.

18. The method of claim 16, further comprising providing a sleeve within the receptacle and forming, in a wall of the sleeve, a plurality of holes.

19. The method of claim 18, wherein the plurality of holes are positioned to redirect flowing fluid from within the sleeve, through the holes, and into the flow channels.

20. The method of claim 18, wherein a fluid flow path transitions from vertical within the sleeve, to inclined as a fluid flows through the holes and into the flow channels, and to horizontal within the flow channels.

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