Abstract: A telescoping rod control cluster assembly change tool for moving control rod assemblies among fuel assemblies in a nuclear facility. The operation of the tool is completely mechanical and the telescoping feature enables the tool to have a relatively low profile when it is being moved and stored without housing a control rod assembly. Rigidly supported alignment cards guide a gripper that attaches to the control rod assembly as the control rod assembly is withdrawn into the tool with the alignment cards preventing any lateral or rotational movement of the gripper.

Abstract: A method for selecting a loading map for a nuclear reactor core including the following steps: a) providing production data relating to the nuclear fuel assemblies, b) providing neutron data which are representative of the operation of the core, c) calculating the three-dimensional distribution of the local power in the core, d) calculating the extreme value reached by at least one thermomechanical parameter within the nuclear fuel assemblies, and e) selecting, in accordance with the extreme values calculated, a loading map from the loading maps envisaged. A system, computer program and storage medium for selecting a loading map for a nuclear reactor.

Abstract: The present invention provides a method of operating a Boiling Water Reactor, having the steps of analyzing LPRM signals for oscilliatory behavior indicative of neutron-flux-coupled density wave oscillations, determining if oscilliatory behavior is present in the signals; initiating a reactor protective corrective action if the oscilliatory behavior is determined, and in addition, initiating corrective actions if neutron uncoupled oscillations are possible. Detecting the later is performed through analytically determined exclusion zone on the power flow map or by on-line stability calculations for several high power channels.

Abstract: A nuclear reactor core is disposed in a pressure vessel along with upper internals disposed in the pressure vessel above the reactor core. The upper internals include internal control rod drive mechanisms (CRDMs) mounted on a suspended support assembly. A hollow cylindrical central riser is disposed in the pressure vessel above the nuclear reactor core. A hollow cylindrical section is disposed in the pressure vessel below the hollow cylindrical central riser and surrounding the nuclear reactor core. A riser transition element connects with the hollow cylindrical central riser and the hollow cylindrical section to form a continuous hollow cylindrical flow separator. The suspended support assembly of the upper internals is suspended from the riser transition element. The pressure vessel may comprise upper and lower vessel sections connected by a mid-flange, with the riser transition element welded to the mid-flange by gussets extending outward and upward from the riser transition element to the mid-flange.

Abstract: A nuclear reactor comprises a pressure vessel, a nuclear reactor core comprising fissile material disposed in the pressure vessel, and a core basket disposed in the pressure vessel and containing the nuclear reactor core. An incore instrument is disposed in a guide tube of the nuclear reactor core. The incore instrument has a cable extending out of the bottom of the nuclear reactor core and making a 180° turn. A bottom support element is attached to the bottom of the core basket and defines or includes a routing tube that routes the cable of the incore instrument through the 180° turn. In some embodiments, the pressure vessel includes upper and lower vessel portions, the nuclear reactor core and core basket are disposed in the lower vessel portion, and the vessel penetration is through the lower vessel portion or through a mid-flange connecting the upper and lower vessel portions.

Abstract: A traveling reactor power monitoring system includes a traveling reactor power monitoring system including a drive control unit configured to move a traveling probe in a guide tube by rotating a motor, and a proximity switch that generates a 1st preventing retraction signal when the travelling probe is detected by the proximity switch to exist at a predefined stop range in a shielding vessel. The drive control unit stops retracting the travelling probe when the 1st preventing retraction signal is generated by the proximity switch, and wipes out the 1st preventing retraction signal by detecting that the probe exists outside the predefined stop range on the basis of a probe information as a substitute for the 1st preventing retracting signal output by the proximity switch.

Abstract: Illustrative embodiments provide systems, methods, apparatuses, and applications related to annealing nuclear fission reactor materials.

Abstract: Most modern integrated circuit transceivers, especially wireless LAN, utilize a direct conversion radio architecture, which is highly advantageous from the perspectives of cost and flexibility, there exist several performance impairments, including gain and phase imbalances between the in-phase (I) and quadrature (Q) of a transmitter or receiver. Disclosed herein is a signal processing methodology and system for compensation of I/Q imbalance for a direct conversion packet-switched OFDM communications system. The imbalance, which accounts for transmitter I/Q imbalance, RX I/Q imbalance, phase/frequency error, and dispersive multipath fading. Both frequency dependent I/Q imbalance and frequency independent cases are considered, covering both wideband and narrowband modulation. The proposed estimation algorithms operate within the fully compliant framework of existing multi-user OFDM radio standards (WLAN, LTE, WimAX).

Abstract: A fuel transfer system is used for transporting spent fuel from a first room to a second room. The system includes a carriage configured for travel between the first room and the second room, and a boom assembly that extends and retracts between the first room and the second room, wherein the boom assembly facilitates travel of the carriage. The system also includes a hoist system positioned in the first room. The hoist system includes at least one boom cable interconnected with the boom assembly to extend and retract the boom assembly. The hoist system also includes at least one carriage cable interconnected with the carriage to move the carriage.

Abstract: In a method and device for facilitating a uniform loading condition for a plurality of support members supporting a steam dryer in a nuclear reactor, the device may include at least one or more actuators. Each actuator may be provided between a corresponding support member and a lower bearing surface of a portion of the dryer for lifting its corresponding dryer portion lower bearing surface relative to the support member. The device may include at least one or more measurement units. Each measurement unit may correspond to a given support member for measuring a displacement value between the corresponding support member and the lower bearing surface of its corresponding dryer portion.

Abstract: Disclosed is a method for removing a thermal sleeve from a cold leg of a reactor coolant system, which enables removal of an unintentionally separated thermal sleeve without implementation of a pipe cutting operation, preventing invasion of impurities into pipes and securing reliability in repetitious welding of the pipes. In particular, the method enables a remote operation and an underwater operation using wire ropes, thus being capable of minimizing a negative effect on workers due to radiation exposure.

Abstract: A shroud support of a BWR includes a shroud support cylinder, shroud support legs welded to a bottom of a reactor pressure vessel (RPV) and a shroud support cylinder, and an annular shroud support plate disposed between the RPV and the shroud support cylinder and welded to the RPV and the shroud support cylinder. A support apparatus is set a CRD housings installed to the bottom of the RPV. A rail guide member horizontally set to the support apparatus reaches directly below the shroud support plate through an opening between the shroud support legs. A bent rail is set on the rail guide member. The bent rail setting a repair device is pushed out along the rail guide member toward the RPV through the opening portion by the rail push-out apparatus set on the support apparatus. The bent rail is spread at directly below the shroud support plate.

Abstract: A reactor installation tool and method for installing a reactor unit in a reactor tube. A reactor installation tool including a movable assembly and a fixed assembly linked together such that the movable assembly can be adjusted relative to the fixed assembly. The movable assembly including a reactor sleeve attachment means for releasably securing a reactor sleeve loaded with a reactor unit to the tool. The fixed assembly including an expandable clamping unit for releasably securing the tool to a reactor tube. A reactor unit can be installed in the reactor tube by adjusting the movable assembly to extract the reactor unit from the reactor sleeve as the fixed assembly is rigidly secured to the reactor tube. The fixed assembly can be released from the reactor tube and the reactor installation tool can be removed from the reactor tube.

Abstract: A preventive maintenance/repair device 10 of the present invention includes: a device body 11, and holding mechanisms 13a and 13b connected to the device body 11, the holding mechanisms 13a and 13b being configured to hold the device body 11 on an outer circumferential surface of a cylindrical structure 19. Further, the device body 11 is equipped with a traveling and driving part configured to be circumferentially movable along the outer circumferential surface of the cylindrical structure 19. Furthermore, each of the holding mechanisms 13a and 13b is equipped with a maintenance/repair mechanism 16 configured to maintain and repair the cylindrical structure 19.

Abstract: A robot for machining a part of structure under water, comprising a machine tool having a chamber receiving a machining element, a support and guiding structure of the machine tool fixable with respect to the part to be machined and having submersible mobile elements and corresponding submersible guiding elements defining axes along which the mobile elements are movable to position the machine tool with respect to the part to be machined, displacement units for displacement of the mobile elements along the axes, a gas supply connecting to the machine tool to inject gas in the chamber, and a programmable control unit for operating the displacement units and the machine tool based on a closed-loop control mode in order to achieve the machining of the part.

Abstract: Apparatus for longitudinally segmenting a cruciform shaped irradiated boiling water reactor control rod having four elongated blades radially extending from a central spline, into four flat panels. The apparatus employs a double bladed band saw with the band saw blades orthogonally oriented at two different elevations and having one side of each band saw blade crossing over the center of the spline of the control rod in between the control rod blades.

Abstract: A reusable up-ending device for loading or unloading nuclear fuel assembly shipping packages. The device has a translating base mounted to a fixed beam structure and two stabilizing arms affixed to a mounting fixture on the base that is secured to the operating floor. The stabilizing arms include a spring dampener and have a simple elbow joint that straightens after the package is up righted. Translation is achieved by means of a hand adjustable lead screw and enables the base to be most advantageously positioned. The shipping package is inserted into pivot mount blocks located at the front of the base and the package is secured at the pivot mount blocks by means of a trunnion and at the support arms by means of a locking pin. Once the package is up-righted the elbows on the support arms are locked in place.

Abstract: A liquid fluoride salt cooled, high temperature reactor having a reactor vessel with a pebble-bed reactor core. The reactor core comprises a pebble injection inlet located at a bottom end of the reactor core and a pebble defueling outlet located at a top end of the reactor core, an inner reflector, outer reflector, and an annular pebble-bed region disposed in between the inner reflector and outer reflector. The annular pebble-bed region comprises an annular channel configured for receiving pebble fuel at the pebble injection inlet, the pebble fuel comprising a combination of seed and blanket pebbles having a density lower than the coolant such that the pebbles have positive buoyancy and migrate upward in said annular pebble-bed region toward the defueling outlet. The annular pebble-bed region comprises alternating radial layers of seed pebbles and blanket pebbles.

Abstract: A dimensional reactivity management system that takes into account the axial burnup shape data of a nuclear fuel assembly to determine the acceptability of placement of the assembly relative to other assemblies in a storage container.

Abstract: An embodiment of the present invention provides an apparatus and system for repairing and/or maintaining a position of a first component in relation to a second component. The first and second components may be located within a reactor pressure vessel of a nuclear powerplant. The apparatus and system may attach at least one bearing plate to a horizontal surface of the first component. The apparatus and system includes structure to apply a pre-load to the first component. This may assist in maintaining the position of the first component relative to the second component.

Abstract: Method for packing nuclear fuel in a cooling pond in a canister (12) located inside a container (10), comprising the steps of the immersion of the canister (12) and the container (10), filling the canister (12), fitting a sealing device (D) comprising caps and means of attaching a cap onto said canister (12) and of checking this attachment.

Abstract: A method of repairing a nuclear fuel cell wall and tools useful for performing that repair are described. A repair tool may be used to align a jack near a region of a bent or distorted structural component of nuclear fuel cell and that jack may be used to apply a force to that structural component. Application of such a force may serve to bend the structural component of a nuclear fuel cell in a way to restore the structural component to its position before damage occurred. The repair tool includes a way of mounting that tool to a fuel cell, positioning elements to align the tool near a structural deformation or bent element and a jack that may be use to apply a force to at least one structural component in a fuel cell.

Abstract: A method for carrying out a reactor internal, comprising steps of: forming a first opening portion in a ceiling of a reactor building at a position directly above an equipment pool in said reactor building; cutting a cylindrical reactor internal surrounding a core in a reactor pressure vessel disposed in said reactor building, at one position in an axial direction; surrounding said cut cylindrical reactor internal with a radiation shield; and carrying out said cylindrical reactor internal surrounded by said radiation shield out of said reactor building through said first opening portion.

Abstract: A maintenance/repair device for reactor internal structure 6 of the present invention includes a device body 6a configured to be fixed on a reactor internal structure 49. Connected to the device body 6a is a welding-part repair mechanism 6b configured to repair a welding part 49a of the reactor internal structure 49. Thus, a welding part 2a of the reactor internal structure 49 can be repaired by the welding-part repair mechanism 6b, while the device body 6a is fixed on the reactor internal structure 49.

Abstract: A method to capture, retain and remove debris falling into a nuclear reactor fuel bundle assembly including a bundle of fuel rods mounted below an upper tie plate and housed in a hollow metal channel, the method includes: inserting a debris shield in the upper tie plate; maintaining the shield in the upper tie plate and above the fuel rods, and water rods, while the fuel bundle assembly is in an operating nuclear reactor core; capturing debris falling in the fuel assembly on the debris shield; after capturing the debris, removing the fuel bundle assembly with the inserted debris shield from the nuclear reactor core to a maintenance/fuel inspection pool and thereafter removing the debris shield from the upper tie plate, cleaning and then reinserting the cleaned debris shield back into the upper tie plate, and moving the fuel bundle assembly from the maintenance/fuel inspection pool back into the nuclear reactor core.

Abstract: A nut assembly for connecting adjoining poles in a nuclear reactor may include an upper nut and a lower nut. The upper nut may include threads on an inner surface of the upper nut. The lower nut may include threads on an inner surface of the lower nut. The lower nut may include threads on an outer surface of the lower nut. The upper nut may rotate over the lower nut in order to lock the lower nut.

Abstract: A method of manufacturing an optimized sheet metal (1) of a zirconium based alloy is described, which optimized sheet metal (1) defines a sheet plane (BA). The method comprises the steps of providing a sheet metal (2) of a zirconium based. alloy, subjecting the sheet metal (2) to at least a preparing cold rolling and a final cold rolling, wherein the preparing cold rolling and the final cold rolling are both performed in a common rolling direction, and heat treating the sheet metal (1) between the preparing cold rolling and the final cold rolling so that the zirconium based alloy is partially re-crystallized. A method of manufacturing a spacer grid using an optimized sheet metal (1) according to the invention is also described.

Abstract: An apparatus, system and method for handling and translating a spent nuclear fuel storage cask. The apparatus comprises a body for supporting the cask close to the ground so that the cask and the apparatus can pass underneath over head doors. The apparatus further comprises rollers for translating the cask, the rollers adapted to move between a retracted position and an extended position, wherein when the rollers are in the retracted position, the rollers do not contact a ground surface. The apparatus additionally supports the storage cask during spent nuclear fuel transfer procedures.

Abstract: A maintenance/repair device for reactor internal structure 6 of the present invention includes a device body 6a configured to be fixed on a reactor internal structure 49. Connected to the device body 6a is a welding-part repair mechanism 6b configured to repair a welding part 49a of the reactor internal structure 49. Thus, a welding part 2a of the reactor internal structure 49 can be repaired by the welding-part repair mechanism 6b, while the device body 6a is fixed on the reactor internal structure 49.

Abstract: A working apparatus has: a working equipment for doing works on a structure; a folding/unfolding mechanism for conveying the working equipment to the working position in a folded state; a conveyance mechanism (such as a horizontal thruster) for conveying the working equipment and the folding/unfolding mechanism to the working position; a pressing mechanism (such as a ballast tank) for pressing the working equipment against the lower surface of the structure; and a traveling mechanism including a wheel for traveling along the lower surface of the structure and positioning the apparatus.

Abstract: A pressurized water reactor (PWR) includes a vertical cylindrical pressure vessel having a lower portion containing a nuclear reactor core and a vessel head defining an internal pressurizer. A reactor coolant pump (RCP) mounted on the vessel head includes an impeller inside the pressure vessel, a pump motor outside the pressure vessel, and a vertical drive shaft connecting the motor and impeller. The drive shaft does not pass through the internal pressurizer. A central riser may be disposed concentrically inside the pressure vessel, and the RCP impels primary coolant downward into a downcomer annulus between the central ser and the pressure vessel. A steam generator may be disposed in the downcomer annulus and spaced apart from with the impeller by an outlet plenum, A manway may access the outlet plenum so tube plugging can be performed on the steam generator via access through the manway without removing the RCP.

Abstract: A device and method for stabilizing a dryer assembly in a reactor pressure vessel of a nuclear reactor including a spring assembly dimensioned and positioned within the reactor pressure vessel for applying a stabilizing force to the dryer assembly relative to the reactor pressure vessel.

Abstract: According to an embodiment, a horizontally moving stage is mounted on a cylindrical structure within a reactor pressure vessel, travels horizontally along the surface of the cylindrical structure by wheels, and is positioned above an in-reactor pipe by the operation of the horizontally moving stage. A hollow mast is carried by the horizontally moving stage, and is expandable and contractible in a vertical attitude. When the mast is in the vertical attitude, a probe is movable within the mast and performs work in the proximity to the inner surface of the in-reactor pipe. A cable passes through the mast to be connected to the probe.

Abstract: According to an embodiment, an in-reactor operation system which is provided with a crack detection vehicle that moves in a circumferential direction along an outer surface of a shroud disposed in a reactor pressure vessel with the axis vertical, an inspection/check sensor that is mounted on the crack detection vehicle and performs an operation with respect to the shroud, a vehicle positioning mast for setting an initial position of the crack detection vehicle on the shroud, a vehicle fixation mechanism for attaching and detaching the crack detection vehicle to and from the vehicle positioning mast, and a conveyance vehicle for conveying the vehicle positioning mast on which the crack detection vehicle is mounted into the reactor pressure vessel.

Abstract: An improved tool for delivery of a testing element to a limited access location within a nuclear containment includes a rotation apparatus having a connection element that is configured to have an aperture that is formed generally centrally therein. The aperture is structured to receive therein a cable that extends from a testing element, which that avoids the need to use slip rings or similar devices to permit the testing element to carried on a pivotable and rotatable structure. Moreover, an improved submersible machine is structured to carry the tool to a limited access location within a nuclear containment.

Abstract: A debris trap catches debris falling through a fuel bundle orifice in a nuclear reactor. The debris trap includes a shaft and a debris capture tray attached to an end of the shaft. The debris capture tray includes a tray cavity sized larger than the fuel bundle orifice.

Abstract: A nuclear steam generator support and alignment system that supports the entire weight of a nuclear steam generator on the walls of the shielding compartment in which the steam generator is designed to operate within. The support includes hydraulic positioners that can raise, lower, rotate and tilt the steam generator to align the steam generator with reactor coolant piping to which it is to be connected.

Abstract: An outer filter removal tool for a boiling water reactor control rod drive that uses a mechanical advantage obtained through the use of lead screw threads to pull the outer filter off of the control rod drive. Fingers on the tool are closed around the upper flange of the outer filter by sliding a collar over the outwardly biased fingers. A shaft extending through the tool is rotated which in turn extends a push plate against the control rod drive index tube causing the fingers to pull against the upper flange on the outer filter until the filter is freed from the control rod drive. The tool will hold the filter in place until affirmatively released for proper disposal.

Abstract: A method of cleaning sludge from the tube sheet (34) of a nuclear steam generator (10) includes introducing a moveable sludge lance (76) said moveable sludge lance having duel lance heads (77) through handholes (62) in the side of the generator and into a central tube lane (60) having a central stay rod (61) and sludge lancing with high pressure fluid through the row 1 tubes (85) in the tube lane, where the distance (200) between the dual lance heads (77) is wide enough to allow the dual lance heads to extend beyond the central stay rod (61).

Abstract: A pressurized water reactor nuclear containment radiation shield which surrounds the upper portion of a pressure vessel in an ice condenser containment. The vertical walls of the neutron shield are formed in vertical sections with the lower and upper sections operable during outages, to open to promote air flow cooling along the walls in the vicinity of the vessel head.

Abstract: An embodiment of the present invention may reduce the level of vibration experienced by a line, such as, but not limiting of, a pipe, a cable, tubing, or the like, that is connected to at least one separate structure. For example, but not limiting of, the structure includes: a reactor pressure vessel, a sparger pipe, steam generator, a pipe, a pressure vessel, a heat exchanger, a pump, a condenser, a tank, or the like. An embodiment of the present invention may provide support and a preload to the line at a new location or may replace an existing support, such as, but not limiting of, a weld; which may alter the natural frequencies to avoid resonance from occurring when the structure(s) is excited.

Abstract: The machinery system and its application herewith, intended to create an opening in the roof of a Reactor Primary Containment of Generation II and III Nuclear Power Electric Generating Station. This opening is necessary to replace an aging nuclear reactor with a new, safer and more efficient reactor. Generation II and III Nuclear Power Electric Generating Stations include General Electric (GE) Boiling Water Reactor BWR/2, 3, 4, 5 and BWR/6 located in Mark II, and Mark III wet containments and Pressurized Water Reactors manufactured by Westinghouse, Combustion Engineering and Babcock and Wilcox located in dry containments. Until this time, existing reactor replacement was not possible due to Reactor Primary Containment structural enclosure configuration. The Dual Head Vertical Milling Machine System will remove a Reactor Primary Containment Dome Segment thus providing an opening, allowing reactor replacement and the electric generating station to remain operational for an other 40 years and beyond.

Abstract: Disclosed is an unlatching tool that may be used to unlatch a control rod from a control drive. The unlatching tool may include a baseplate, a first guide member and a second guide member attached to the baseplate, a first frame and a second frame attached to the baseplate, a stepper motor attached to the first frame, a worm drive attached to the first frame, a cable reel shaft attached to the first and second frame, a hose wrapped around the cable reel shaft, and a hook attached to a first end of the hose. The hook may include a cylindrical sleeve having a at least one finger configured to fold and unfold. Disclosed also is a method of unlatching a control rod from a control drive.

Abstract: A tool for delivery of a testing element to a limited access location within a nuclear containment includes a rotation apparatus having a connection element that is configured to have an aperture that is formed generally centrally therein. A submersible machine is structured to carry the tool to a limited access location within a nuclear containment. The submersible machine includes a mount apparatus configured to be movably clamped onto a steam dam of a nuclear reactor apparatus and to drive the submersible machine circumferentially along the steam dam to inspect a plurality of jet pumps or other limited access locations of the nuclear reactor apparatus. The improved submersible machine advantageously further includes an adjustment table between the mount apparatus and a frame that carries the tool to enable rapid accurate positioning of the frame, and thus the tool, once the submersible machine has been mounted to the steam dam.

Abstract: A tool to slide a channel on a nuclear reactor fuel bundle assembly, the tool includes: a plate having a slot to receive a handle of the fuel bundle and a lower surface that engages an upper edge of the channel; at least one post extends up from the plate, and an arm is attached to a pivot on the post and includes a first end to receive a downward force and a second end adapted to engage the handle of the fuel bundle to apply an upward force to the handle and push down on the channel.

Abstract: A method of determining the R-factor for a bundle of nuclear fuel rods in a nuclear light water reactor of the boiling water reactor kind. The R-factor is a factor that accounts for the weighted local power influence on a fuel rod. A local R-factor (Ri(z)) is determined for each fuel rod (i) in said bundle and for each of a plurality of levels (z) in an axial direction. The individual axial heat generation profile for a certain fuel rod (i) is taken into account when determining the local R-factors (Ri(z)) for said fuel rod (i). A processor is configured for automatically determining the R-factor. A computer program product, a method of determining the critical power for a bundle of fuel rods, a nuclear energy plant, and a method of operating a nuclear energy plant are also described.

Abstract: A system for installing or removing a component of a nuclear reactor, such as a CRDM, includes a riser apparatus having a lift assembly structured to hold and support the component and a first drive assembly coupled to the lift assembly and structured to selectively move the lift assembly and the component along a length of the riser apparatus, and a transition cart movable along an under vessel area of the nuclear reactor and having a pivot mechanism, wherein the riser apparatus is selectively engageable with the pivot mechanism and the pivot mechanism is structured to selectively rotate the riser apparatus from a horizontal position to a vertical position. The riser apparatus may also include a second drive assembly structured to selectively move the riser apparatus relative to the transition cart in a direction parallel to a longitudinal axis of the riser apparatus.

Abstract: In a clamping jig and system for inspecting spacer grids for a nuclear fuel assembly, the jig firmly and precisely clamps a variety of grids on a measurement stage moving at high speed so that, among constituent parts of the nuclear fuel assembly, the spacer grids can be inspected using a non-contact measurer. The clamping jig includes a frame having a plurality of holding recesses into which the corresponding spacer grids are inserted, supporting means mounted in each holding recess of the frame to allow each spacer grid to be adjusted from below so it can be maintained in a horizontal state, clamping means installed around each holding recess to clamp two adjacent sides of each spacer grid to a corner of the respective holding recess, and resilient means installed on the sides opposite the clamping means and resiliently supporting the other two sides of each spacer grid.

Abstract: The invention relates to a nuclear power station comprising: at least one high temperature reactor; a storage installation (14) for fuel elements (5); means (32) for transferring the fuel elements (5) between the core (4) and the storage installation (14). According to the invention, the transfer means (32) comprise a tunnel (34) for transferring the fuel elements between the reactor core (4) and the storage installation (14).

Abstract: A data processing apparatus maps input symbols to be communicated onto a predetermined number of carrier signals of an Orthogonal Frequency Division Multiplexed (OFDM) symbol. The data processor includes an interleaver memory which reads-in the predetermined number of data symbols for mapping onto the OFDM carrier signals. The interleaver memory reads-out the data symbols on to the OFDM carriers to effect the mapping, the read-out being in a different order than the read-in, and the order being determined from a set of addresses. The set of addresses are generated from an address generator. The address generator includes a linear feedback shift register and a permutation circuit.