MXPA94008644A - Method and apparatus for supporting a cover in nucl unreactor - Google Patents

Abstract

To eliminate the need for welding, drilling or otherwise machining a cover structure which is used to surround a plurality of fuel assemblies in a nuclear reactor, a plurality of upper suspension rods interconnect a structure on the cover to a ring of support that is clamped in relation to the upper periphery of the cover. Lower suspension rods interconnect a lower edge or shoulder portion of the cover with the support ring. In this way, through the upper and lower suspension rods and the support ring, the cover can be supported within the RVP. The upper support ring is arranged to clamp the lower ends of the upper suspension rods against the upper outer peripheral portion of the cover, while the lower ends of the lower suspension rods are clamped against the wall portion peripheral bottom of the cover by an inferior support ring

Description

METHOD AND APPARATUS FOR SUPPORTING A COVER IN A NUCLEAR REACTOR INVENTOR: BENGT IVAN BAVERSTEN; Swedish citizen residing at: Pilspetsgatan 8, S-72353 Vasteras, Sweden.

CAUSAHABIENTE: COMBUSTIÓN ENGINEERING, INC., A North American Society, organized and existing in accordance with the Laws of the State; of: Delaware, E.U.A., residing at: 1000 Prospect Hill Road, Windsor, Connecticut 06095, E.U.A.

SUMMARY OF THE INVENTION To eliminate the need to weld, drill or otherwise machine a deck structure that is used to enclose a plurality of fuel assemblies in a nuclear reactor, a plurality of upper suspension rods interconnect a structure on the deck to a support ring that is clamped in relation to the upper periphery of the cover. Lower suspension rods interconnect a lower edge or shoulder portion of the cover with the support ring. In this way, through the upper and lower suspension rods and the support ring, the cover can be supported within the RVP. The upper support ring is arranged to clamp the lower ends of the upper suspension rods against the upper outer peripheral portion of the cover, while the lower ends of the lower suspension rods are clamped against the wall portion lower peripheral of the cover by a lower support ring. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to nuclear reactors. More specifically, the present invention relates to a support assembly by means of which a cover can be held within a reactor pressure vessel, without need for drilling or other machining of the cover structure. Description of Related Art As is well known, safety is a fundamental issue in devices such as nuclear reactors and strict measures must be taken to ensure that mechanical failures such as those that tend to be induced by the formation of cracks and the like in various and numerous structures that comprise a nuclear reactor, are eliminated. It has been found that various stresses that are induced in a cover structure used to circumscribe fuel assemblies tend to produce cracks in the support ring area and upper guide of the core cover assembly. For example, it can be envisaged that cracks may form in the cover at the horizontal solder joint between the upper guide support ring and the cover. This of course induces a safety concern since if the weld were to break, the cover can move and cause a problem with insertion of the control rod. SUMMARY OF THE INVENTION It is an object of the invention to provide a mounting by means of which a cover can be held within a reactor pressure vessel (RVP) in a manner that does not induce stresses that cause cracking and similar types of deterioration of the cover assembly. , which can be connected to the cover using only light clamping clamping and which does not require any welding, drilling or other machining of the cover assembly. A further object of the present invention is to provide a suspension rod assembly by means of which a cover or structure of similar type can be supported within an RVP or similar type vessel, without the need to weld, drill holes and the like. A still further object of the present invention is to provide a suspension rod assembly that employs a basic upper suspension rod and multi-segment ring combination and that is supplied with lower suspension rods that are hung on the multi ring. -segments and coupling a shoulder or similar of the structure that is supported, in the event that the vertical displacement of the suspended structure requires to be attenuated or avoided. In f, in accordance with the present invention, to eliminate the need for welding, drilling or otherwise machining a cover structure which is used to surround a plurality of fuel assemblies in a nuclear reactor, a plurality of upper suspension rods they interconnect a structure located on the cover to a support ring assembly that is clamped relative to the upper periphery of the cover below the upper guide support ring assembly. The lower suspension rods interconnect the lower edge of the cover with the support ring. In this way, through the upper and lower suspension rods and the support ring assembly, the cover can be supported within the RVP. The upper support ring is arranged to clamp the lower ends of the upper suspension rods against an upper outer peripheral portion of the cover, while the lower ends of the lower suspension rods are clamped against a portion of the wall. bottom peripheral of the cover by a lower support ring, in a shape which ensures a good connection between the lower end of the lower suspension rods and an edge, as defined by a stepped diameter portion or the like.

In a specific embodiment of the invention, the upper guide support ring, together with the upper part of the cover is held in place by a support ring assembly which is clamped around the cover po under the support ring top guide The support ring consists of four segments that are bolted together. The segments are formed to define a polygonal ring with 12 symmetrical sides. During the installation of the cover support ring d, the ring is suspended from the upper suspension rods that are spaced around the cover. When the cover support ring is clamped around the cover, the upper suspension rods are clamped between the support ring and the cover and become an integral part of the clamping assembly by clamping. The upper end of each suspension rod has a transverse bar that engages between and is supported by bolt clamps d separator. To avoid vertical separation between the cover and the upper guide support ring, the cover support ring is locked against vertical movement by a plurality (eg, twelve) of lower suspension rods that engage the cover support ring. The lower end of the lower suspension rods plunge into a recess defined by a stepped diameter of the cover located further down the deck. The lower suspension rods are kept engaged with this recess by a lower support ring surrounding the lower suspension rods and clamping the lower ends of these rods radially inward against the side of the cover. Before the cover support ring is finally tightened in a fixed condition, the sections of the upper suspension rods are adjusted using adjusting nuts that are provided at their upper ends, such that the vertical installation space between the rods of lower suspension and the horizontal surface of the recess or the like located at the lower end of the cover and against which the lower ends of the lower suspension rods are coupled, is closed. However, it should be noted that with the present invention, in case the risk of vertical separation between the upper guide ring and the cover is of little or no consideration, the lower suspension rods and the lower support ring can be omitted. , and the installation space is closed between the upper suspension rods and the lower side of the guide support ring. More specifically, a first aspect of the present invention resides in a nuclear reactor that characterizes: a cover placed inside a reactor vessel to encircle at least one fuel assembly; and a cover support assembly for holding the cover in the reactor vessel, comprising: a top support ring fixed with respect to the upper periphery of the cover; and an upper suspension rod having a lower end coupled with the upper support ring and an upper end adapted for connection to a predetermined structure that is located inside the reactor vessel on the cover. A second aspect of the present invention resides in a nuclear reactor which characterizes: a cover disposed within a reactor vessel to encircle at least one fuel assembly; and a cover support assembly, for supporting the cover in the reactor vessel, comprising: a first multi-segment ring member disposed with respect to the upper periphery of the cover, the first ring member having a plurality of gaskets that allow adjust the size of the ring and selectively fix against the cover, - a first adjustable length suspension rod having a lower end coupled with the first ring member and an upper end adapted for connection to a predetermined structure, which is located within the reactor vessel on the cover. A third aspect of the invention resides in a support assembly, for supporting a cover structure within a container, which characterizes: a ring assembly with multiple segments that can be selectively tightened with respect to the cover; a plurality of first suspension rods, the first suspension rods each have hook members at their lower ends, the hook members are arranged to engage with the ring assembly and to be secured against the outer surface of the cover, when the Ring assembly is selectively tightened. The upper ends of the first suspension rods are arranged to be engageable with a structure that is arranged in the container on the cover. A further aspect of the present invention resides in a method for supporting a cover in a pressure vessel of a nuclear reactor, comprising the steps of: suspending a plurality of upper suspension rods in a structure disposed in the pressure vessel, over the level at which the cover is suspended; connecting the plurality of upper suspension rods to a multi-segment ring member that is disposed with respect to the rod by providing hooks that are provided at the lower end of the upper suspension rods to engage with the ring member in such a manner that when the ring member is tightened, portions of the hooks are pressed into engagement with the cover; and the ring member is tightened to secure the portions of the hooks against the cover. BRIEF DESCRIPTION OF THE DRAWINGS The various objects, advantages and merits of the present invention will be more clearly appreciated as a detailed description of the preferred embodiments of the invention is given in conjunction with the accompanying drawings in which: Figure 1 is an exploded perspective view of a nuclear reactor of a type in which the present invention is applied; Figure 2 is a plan view showing a cover arranged inside a pressure vessel and also showing the arrangement of various elements, such as jet pump positions, separation lift rods and the like, which are located in the space annular defined between the cover and the RVP wall (reactor pressure vessel); Figure 3 is a plan view similar to that illustrated in Figure 2, showing the arrangement of a cover support ring, disposed with respect to the exterior of the cover structure and illustrating the placement of various upper suspension rods and lower that characterize one embodiment of the present invention; Figures 4, 5A, 5B, 6A, 6B and 7 illustrate characteristics of the upper and lower suspension rods that characterize the embodiment of the present invention; Figure 8 is a side view showing the assembly of a plurality of upper and lower suspension rods in the manner in which the upper ends of the upper suspension rods can be held in spacer clamps; and Figure 9 is a view similar to that illustrated in Figure 8, illustrating the cooperation between the upper guide support ring and a cover lifting lug. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Figure 1 is a partial sectional perspective view of a boiling water reactor, of the type in which the present invention is applied. This BWR (boiling water reactor) includes simply by way of example, a head 40 which is fastened to the upper part of the reactor vessel 41, a vent and head spray 42, a steam dryer lifting lug 43, a dryer assembly steam 44, a steam outlet 45, a steam separator assembly 46, a feed water inlet 47, a core dew inlet 48, a feed water sparger 49, an inlet for low pressure refrigerant injection 50, a core dew line 51, a core sprinkler sparger 52, an upper guide 53, jet pump assembly 54, a core cover 55, fuel assemblies 56, a recirculating water inlet / jet pump 57, a core plate 58, control rods 59 (circumscribed in elongated tubular guide nozzles or nozzles), a recirculation water outlet 60, a container support skirt 61, a shielding wall 62, guide mechanisms for control rod 63, control rod displacement hydraulic lines 64 and a core flow monitor 65.

Figure 2 is a plan view of the previous type of reactor showing the manner in which the cover 55 is disposed with respect to the inner periphery of the pressure vessel wall of the reactor 66 and the arrangement of elements such as the rods separator lifts 68, core dew pipes 70, a separator guide clamp 70 and the like. This view also shows the upper portions of the upper suspension rods 100 which forms a vital part of the present invention and which will be discussed later in connection with Figures 4 to 7. Figure 3 is a plan view showing a ring of cover support 200 disposed around the upper periphery of the cover 55. As will be appreciated from this figure, the cover support ring 200 comprises an assembly of four three-sided members 200 a which are interconnected to form a polygonal ring member of twelve sides. In this case, the four segments or members 200A of the assembly are bolted together in four gaskets or ring attachment sites 200B which allow the cover support ring 200 to be pressed against the outer peripheral surface of the cover 55 in one place. below the upper guide ring 56. To improve rigidity and resistance to joint 200B, a mounting plate assembly or reinforcement plate 200BG is arranged, as illustrated. It should be noted that these reinforcement plate assemblies 200BG are not illustrated in the plan view of Figure 3 for reasons of illustrative clarity. Figures 4 to 7 show details of the upper suspension rods 100 and associated lower suspension rods 300, and the manner in which they cooperate with the upper cover support ring 300 and the lower support ring 400. As illustrated, the upper suspension rods 100, each comprising an arrow 100A, having a clamp-like member G or portion 100B at the lower end and a U-shaped clamp or transverse rod member 100C at the upper end. The U-shaped transverse bars 100C are connected to the arrows 100A by means of adjusting nuts 100D. The U-shaped crossbars 100C, each are arranged to fit between two adjacent spacer bolt clamps 46A and are sized to cooperate with these clamps 46A in a manner that allows a rigid support connection to be established. The clamp-type members G 100B at the lower ends of the arrows 100B are arranged to receive the upper support ring 200 in the manner illustrated. As will be appreciated, in the event that an upper suspension rod 100 is disposed at a ring clamp site 200B, the clamp member G 100B projects out essentially at the same level as the end portions of the flanges 200F that are form at each end of the segments 200A.

This as will be appreciated from Figure 7, allows the bolt 200D interconnecting the two flanges 200F to pass through the opening in essentially rectangular shape. The vertical wall portion lOOBw of each of the clamp member G 100B is arranged to have its trailing edge surface trapped against the outer peripheral surface of the cover 55 by the upper support ring 200 and fixed in this position at tightening the bolts 200D interconnecting each of the segments 200A of the upper support ring 200. The upper ends of the lower suspension rods 100 are formed with a double hook assembly 330A (see Figures 6A and 6B) that hangs over the edge of the upper support ring 200. In the event that an upper and a lower suspension rod are arranged in vertical alignment with each other, the double-hook assemblies 300A are arranged to seat on both sides of the clamp-type member G 100B of the upper suspension rod corresponding to 100. In cases where the lower suspension rods are arranged in a joint, the double hook portion or is arranged to be divided in the joint and retained by the bolt 200D of the joint passing after assembly in a shape that traps the double hook portion in position. The lower ends of each of the lower suspension rod arrows 300B each are formed with an enlarged head portion 300C, which fits in part under the stepped shoulder edge or portion 55A formed in the cover 55. The lower edge of the lower support ring 400 rests on the upper portion of the enhancement portion 300C in the manner illustrated in Figures 6A and 7. Furthermore, as will be apparent in Figure 7, the lower support ring 400 is disposed for fixing the lower end portion of the arrows 300B of each of the lower suspension rods 300 against the outer periphery of the cover 55 and prevents the enhancement 300C at the end of each of the arrows 300B from moving laterally and towards out away from the cover 55 and in this way ensures that the required support connection between the cover and the lower suspension rods is maintained. Figures 8 and 9 are side elevational views showing the manner in which the U-shaped cross bars 100C of the upper suspension rods 100 fit between and are supported by the spacer fastening clamps 46A. In these figures, the number 80 denotes a core spray pipe, number 82 denotes a cover lift pin and the number 84 denotes a spacer guide clamp. During installation of the above described cover support ring assembly, the upper support ring 200 is suspended by the upper suspension rods 100 which are spaced around the cover 55. When the cover support ring 200 is fixed around the cover 55, the upper suspension rods 100 are fixed between the support ring 200 and the cover 55 and becomes an integral part of the mounting assembly. Cross bar 100C at the upper end of the upper end of each suspension rod engages between and is supported by spacer bolt clamps 46A. The vertical separation of the cover and the upper guide support ring is avoided because the cover support ring 200 is locked against vertical movement by the lower suspension rods (twelve in this case), which hang on the ring cover bracket 200. Before the cover support ring 200 is finally tightened in a fastening condition, the lengths of the upper suspension rods 200 are adjusted using the adjustment nuts 100D provided at their upper ends. This allows the vertical installation space located between the enhancement portions 300C at the end of the lower suspension rods 300 and the stepped diameter edge portion 55A of the cover 55, close. It will be noted that in the case of the risk of vertical separation between the upper guide ring and the cover 55 is of little or no interest, the lower suspension rods 300 and the lower support ring 400 can be omitted, and the installation space can be closed between the upper suspension rods 100 and the lower side of the guide support ring

Claims (10)

1. Upper through adjustment of the upper suspension rod sections. Although the present invention has been described with reference to only one embodiment, it will be noted that various changes and modifications that may be made without departing from the scope of the invention will be essentially self-evident and as such are limited only by the appended claims. NOVELTY OF THE INVENTION Having described the invention as above, property is claimed as contained in the following: CLAIMS 1. A nuclear reactor characterized in that it comprises: a cover arranged inside a reactor vessel, to encircle at least one fuel assembly; and a cover support assembly, for supporting the cover in the reactor vessel, comprising: a top support ring fixed with respect to the upper periphery of the cover; and an upper suspension rod having a lower end coupled with the upper support ring and an upper end adapted for connection to a predetermined structure that is located inside the reactor vessel on the cover.
2. 2. A nuclear reactor as described in claim 1, characterized in that it further comprises: a lower support ring disposed with respect to the outer periphery of the cover; and a lower suspension rod having an upper end engaged on top of the upper support ring and a lower end engaging with an edge portion of the cover.
3. 3. A nuclear reactor, characterized in that it comprises a cover arranged inside a reactor vessel in order to surround at least one fuel assembly; and a cover support assembly for holding the cover in the reactor vessel, comprising: a first multi-segment ring member disposed with respect to the upper periphery of the cover, the first ring member having a plurality of gaskets that allow the size of the ring is adjusted and selectively fixed against the cover; a first adjustable length suspension rod, having a lower end coupled with the first ring member and an upper end adapted for connection to a predetermined structure which is located inside the reactor vessel on the cover.
4. A nuclear reactor as described in claim 3, characterized in that it further comprises: a second ring member arranged with respect to the outer periphery of the cover at a level below that of the first support ring; and a second suspension rod having a top end coupled with the upper part of the upper support ring; and a lower end that engages an edge portion of the cover.
5. 5. A support assembly for supporting a cover structure within a container, characterized in that it comprises: a ring assembly of multiple segments that can be selectively tightened with respect to the cover; a plurality of first suspension rods, the first suspension rods each have hook members at their lower ends, the hook members are arranged to engage with the ring assembly and fixed against the outer surface of the cover when the mounting The ring is selectively tightened, the upper ends of the first suspension rods are arranged to be engageable with a structure disposed in the container on the cover.
6. 6. A support assembly as described in claim 5, characterized in that it further comprises: a plurality of second suspension rods, each of the second suspension rods has a hook assembly, at its upper ends, arranged for coupling with the multi-segment ring assembly, each of the second suspension rods has a coupling member at its lower end, each of the coupling members are arranged to engage a shoulder portion defined in the cover at a lower level than one in which the multi-segment ring assembly is arranged; and a lower ring member that is disposed with respect to the plurality of second suspension rods and arranged to retain the coupling portions in engagement with the shoulder portion.
7. 7. A support assembly as described in claim 5, characterized in that the first suspension rods include means for adjusting their length. A method for supporting a cover in a pressure vessel of a nuclear reactor, characterized in that it comprises the steps of: suspending a plurality of upper suspension rods in a structure disposed in the pressure vessel above the level at which it is suspended the cover; connecting the plurality of upper suspension rods to a multi-segment ring member disposed relative to the cover, by providing hooks that are provided at the lower end of the upper suspension rods for coupling with the ring member, such that when the ring member is tightened, portions of the hooks are pressed in engagement with the cover; and tightening the ring member to hold the portions of the hooks against the cover. A method as described in claim 8, characterized in that it further comprises the steps of: connecting the lower suspension rods with the ring member, - attaching the lower ends of the lower suspension rods with a predetermined portion of the cover; and retaining the lower ends of the lower suspension rods against the outer surface of the cover in a form wherein the coupling between the lower ends of the suspension rods and the predetermined portion of the cover is maintained using a second ring member. A method as described in claim 9, characterized in that it further comprises the step of adjusting the length of the upper suspension rods before the pressing steps and after the hooking steps, in order to bring the lower ends of the lower suspension rods in engagement with the predetermined portion of the cover. In compliance with the provisions of Article 47 of the Inventions and Trademarks Law in force, I declare under oath that the invention described above is the best known method for putting this invention into practice. In testimony of which, I sign the present in Cuernava, Morelos on November 8, 1994. COMBUSTION ENGINEERING, INC.