General Electric Company

Hewlett-packard Company

Gary E Dix

Bruce Matzner

Robert B Elkins

Russell L Crowther

Mark J Colby

James Courtney Shaug

Eric B Johansson

Anthony P Reese

Richard A Wolters

Kenneth Wood Brayman

Jens G Andersen

Donald Keith George

James Charles Rawlings

Bharat S Shiralkar

Separation devices are disposed in the vent volume above part-length rods and above one or more of the spacers above the upper ends of the part-length rods. The separation devices preferably comprise swirlers located above the lattice openings which would otherwise receive the rods but for the underlying part-length rods. In this manner, flow is directed laterally outwardly onto the surfaces and into the interstices of the full-length fuel rods for improved power performance while simultaneously adverse pressure drops across the spacers are minimized.

Fluid separation device for vent volumes of nuclear fuel bundles

A fuel bundle assembly for a boiling water nuclear reactor comprising a plurality of fuel rods having respective fuel columns therein, and arranged in an ordered array, extending between upper and lower support structures, the plurality of fuel rods enclosed within a hollow, open-ended channel member at least partially enclosed by the open-ended channel member; at least one water rod supported on the lower tie plate and extending upwardly toward the upper tie plate, the at least one water rod having an upward flow path including at least one inlet at a lower end of the upward flow path, and a downward flow path including at least one outlet at a lower end of the downward flow path, the at least one outlet located about midway along the fuel columns within the fuel rods.

Siphon water rods

A steam/water separating device for a nuclear fuel bundle is located in a vent volume above part-length rods and includes a helical swirl vane. In one form, the swirl device lies below a vent tube and a transition element for flowing liquid laterally outwardly into the interstices of the fuel rods and steam upwardly within the vent tube. In another form, the vane depends from a cylindrical barrel open at its lower end. An annular pick-off tube extends into the open upper end of the barrel and lies in communication through a transition element with a superposed steam vent tube. An annular outlet is defined between the barrel and pick-off tube and the transition element deflects coolant water flowing through the annular outlet in a lateral outward direction for flow into the interstices of and onto the full-length fuel rods. Steam flows upwardly in the barrel through the pick-off tube into the steam vent tube.

Separation device for a vent volume in a nuclear reactor

The steam/water separator includes a lower standpipe for receiving a two-phase mixture of water and steam at its lower end. Internal threads or elements spaced about the interior wall of the standpipe impart a swirl to the incoming mixture, producing a thin film along the walls. Standard pick-off rings or a porous wall may be employed to separate the liquid from the vapor. A central swirl is imparted to the flow in the region dominated by vapor. This combination of peripheral swirl followed by a central swirl for steam/water separation affords minimum pressure losses along the separator with reduced sensitivity to inlet and submergence conditions.

Low pressure drop steam separators

A deflector is disposed in a steam vent region above the upper ends of part-length fuel rods to deflect upwardly flowing liquid laterally outwardly into the interstices of the full-length fuel rods adjacent the steam vent region. The deflector is supported by a spacer or from the upper tie plate and can be removed from the fuel bundle for access to the part-length fuel rods. The deflector may comprise a flat plate, an inverted pyramid, an inverted cone, a multi-sided pyramidal configuration or a swirl device wherein the horizontally projected area of the deflector is substantially coextensive with the horizontal cross-sectional area of the steam vent area. In this manner, a higher density liquid is provided in the interstices of the full-length rods while the lower density steam flows into the steam vent volume for flow upwardly out of the fuel bundle.

Removable deflectors for bwr fuel with steam vents and part-length rods

In a boiling water nuclear reactor fuel bundle, a debris catching arrangement is disclosed for incorporation within the flow plenum up stream or below the rod supporting grid of the lower tie plate assembly. The device is preferably placed within the lower tie plate flow plenum between the fuel bundle inlet and the rod supporting grid structure supporting the fuel rods; alternate placement can include any inlet channel upstream of the fuel rods including the fuel support casting. The disclosed debris catching designs include strainer structures defining spatially separated straining or obstructing layers imparting to the fluid in the plenum a circuitous flow path. This circuitous flow path causes the two phase separation of the heavier debris from the lighter transporting water by flow direction change with the debris directed and detoured to a trapping structure. Further, a strainer structure is provided in the plenum that does not constitute a continuum of fine structure across the strained plenum which might become clogged to the extend that overall flow is restricted. The strainer structure is positioned so that eventual trapping of the debris occurs upon cessation of flow so that with removal of the plenum from the reactor, such as removal of the fuel bundle, the debris is likewise removed. Embodiments are disclosed which include swirling deflection, cone deflection, and strainer structure deflection of debris.

Debris filters with flow bypass for boiling water reactors

Part length water regions are located above part length fuel rods in boiling water nuclear reactor fuel bundles. The part length water regions include discrete containers having entry ports at the top of the part length water regions for capturing water, and vent ports for permitting internally generated steam to escape. The advantages of improved neutron moderation in the upper portion of the fuel assembly are maintained while the uranium fuel removal requirements are minimized.

Top filled water regions overlying part length fuel rods

In a fuel bundle for use in the core of a boiling water nuclear reactor, part length rods having a tendency to reduce pressure drop are used in combination with spacers and spacer attached devices tending to restore pressure drop to improve critical power. The addition of the part length rods has the advantage of lowering the pressure drop. Attached devices substantially recapture the pressure drop. Exemplary spacer attached mechanisms for the recapture of pressure drop are set forth including vanes--preferably swirl vanes on the spacers, decreasing the spacer pitch to increase the total number of spacers in the upper two phase region of the fuel bundle, increasing the vertical height of the spacers, and increasing the thickness of the metal from which the spacers are constructed. Two classes of separation devices are disclosed for placement in the volume overlying the end of the partial length fuel rods. A first type of device fits to the end of the part length rods and is primarily intended for preventing water passing along the surface of the part length rod adjacent the end of the part length rod from entering the volume overlying the part length fuel rod. A second type of device resides in the volume overlying the part length rod. In either case, critical power is improved.

Optimized critical power in a fuel bundle with part length rods

In a boiling water reactor having discrete bundles of fuel rods confined within channel enclosed fuel assemblies, an improved fuel design of bundles of fuel rods interior of the channels is disclosed. Specifically, partial length rods are utilized which extend from the bottom of the channel only part way to the top of the channel. These partial length rods are symmetrically distributed throughout the fuel bundle with the preferred disposition being in the second row of the bundle of fuel rods from the channel wall. The symmetrical distribution of the partial length rods is at spaced apart locations one from another. During shutdown of the reactor, an improved cold shutdown margin is produced at the top of the fuel assembly due to the improved moderator-to-fuel ratio and reduction in plutonium formation at the upper portion of the bundle. Shutdown control rod worth is improved due to greater moderator-to-fuel ratio and a longer thermal neutron diffusion length. During power reactor operation, the partial length fuel rods improve flow distributions above the ends of the partial length rods by channeling steam in the open interstitial area between rods above the ends of the partial length rods.

Two-phase pressure drop reduction BWR assembly design

In a fuel bundle for a boiling water reactor having one or more part length rods in the two phase region, a steam vent tube is introduced overlying the part length rods. The fuel bundle includes a lower tie plate for admitting water moderator and supporting a plurality of fuel rods in upstanding side-by-side relation, an upper tie plate for permitting water and steam to be discharged from the top of the fuel bundle and maintaining the fuel rods in upstanding side-by-side relation, a surrounding fuel channel for confining moderator flow along a path over the fuel rods and between the tie plates, and dispersed vertically intermittent spacers for maintaining the fuel rods in their designed side by side relation. One or more fuel rods extends from the lower tie plate vertically less than the full length to the upper tie plate ending interior of the fuel bundle at a disposition where the upper end of the part length rods is braced in the vertical position by a spacer. At least one of these partial length rods is provided with an overlying steam vent tube. This steam vent tube has openings and devices distributed along its length to encourage steam flow interior of the tube and remove liquid flow from the interior of the tube. The steam flow within the vent tube eliminates the interface drag between the steam interior of the tube and the surrounding water steam mixture. The presence of the steam vent tube as a high velocity steam escape path enables remaining portions of the fuel bundle to contain a higher liquid moderator fraction with flatter axial voids and power distributions during the operating state of the fuel bundle. The presence of high velocity escaping steam combined with distributed apertures along the length of the steam vent tube promotes resistance to fluid oscillations within the fuel bundles. Variations of steam vent tubes are disclosed including steam vent tubes overlying multiple clustered part length rods. There results a fuel bundle design in which the entire upper cross section of the fuel bundle is devoted to steam generation and coolant outflow.

Steam vent tube for BWR fuel assembly

In a boiling water reactor having discrete bundles of fuel rods confined within channel enclosed fuel assemblies, an improved fuel design of bundles of fuel rods interior of the channels is disclosed. Specifically, partial length rods are utilized which extend from the bottom of the channel only part way to the top of the channel. These partial length rods are shortened with respect to the remaining rods and are symmetrically distributed throughout the fuel bundle with the preferred disposition being in the second row of the bundle of fuel rods from the channel wall. The symmetrical distribution of the partial length rods is at spaced apart locations one from another. The partial length rods extend from the bottom of the fuel bundle and terminate within the boiling region. during shutdown of the reactor, an improved cold shutdown margin is produced at the top of the fuel assembly due to the improved moderator-to-fuel ratio and reduction in plutonium formation at the upper portion of the bundle. Shutdown control rod worth is improved due to greater moderator-to-fuel ratio and a longer thermal neutron diffusion length. During power reator operation, the partial length fuel rods improve flow distribution above the ends of the partial length rods by channeling steam in the open interstitial area between rods above the ends of the partial length rods. This enables a high slip ratio of steam with respect to water and increases the density of the moderating water about the remaining rods in the upper region of the bundle at power operation. The total pressure drop is reduced, permitting more fuel rods in the design or a larger fuel rod diameter. The ratio of two-phase pressure drop to single phase pressure drop also is reduced, tending to increase the threshold for thermal hydraulic instability or coupled nucler-thermal-hydraulic instability. Rod spacers and bundle tie plates are provided with larger apertures overlying the partial length rods for further channeling of the steam and reduction of two-phase pressure drop. Most importantly and during full reactor power output, the pressure drop in the two-phase region of the bundle is reduced without substantial corresponding degradation of the fuel assemblies thermal limits. These features permit designs with larger fuel rod diameter than are possible without part length rods and results in a net increase in fuel assembly uranium weight with the larger fuel rod diameter more than compensating for the weight removed by shortening some of the fuel rods.

An apparatus and process utilizing a large water rod of a fuel bundle in a boiling water reactor fuel assembly as a radiation heat sink during a loss of coolant accident. Core cooling spray is collected at the top end of the bundle's large water rod by a collector and distributed by a distributor to coat the inside wall surfaces of the water rod. In the case of a water rod which is not bottom vented, the water rod body is modified so as to separate the downward flow of liquid water from the upward flow of steam. During normal plant operation, the large water rod serves as a water-filled moderator tube to provide a more uniform power distribution across the fuel bundle.

Cooled water rod (LOCA conditions)

A spacer for positioning at least the four corner fuel rods in a tubular flow channel of a nuclear reactor is disclosed. The spacer comprises a support member having four side bands interconnected by four corner bands to form a unitary structure. Each of the side bands has a L-shaped lobe adjacent each of its ends with one leg of each lobe extending to the adjacent end of its side band. Each of the corner bands is narrower than the side bands and is offset so as to be spaced from the lobe. One leg of each lobe is positioned to engage the tubular flow channel to maintain proper spacing between the flow channel and the adjacent corner fuel rod and to improve the thermal-hydraulic performance of the spacer.

Growing community of inventors

Saratoga, CA, United States of America

Gary E Dix