Method for reinforcing a weld in a pressurised water reactor vessel

Abstract

The invention relates to a method for reinforcing a weld between two internal parts of a pressurised water reactor vessel, comprising providing a reinforcement device comprising: - a reinforcement plate having a coefficient of thermal expansion lower than the coefficient of thermal expansion of each of the two internal parts, said reinforcement plate being connected to each of the internal parts on either side of the weld, and exerting a clamping force between the two internal parts, or - two reinforcing plates and at least one connecting rod, a first of the plates being connected to a first of the internal parts, the second plate being connected to the second part, the connecting rod being arranged between the two plates so as to exert a clamping force between the two plates and thus the two internal parts.

Description

[0001] METHOD FOR REINFORCING A WELD IN A PRESSURISED WATER REACTOR

[0002] VESSEL

[0003] The present invention concerns a method for reinforcing a weld between two internal parts of a pressurised water reactor vessel, such as core barrels, core shrouds, core support shields and plenum cylinders.

[0004] Girth or longitudinal welds in components, in particular cylindrical components, within the pressurised water reactor vessel internals, such as core barrels, core shrouds, core support shields and plenum cylinders, may crack, that can lead to a loss of structural integrity.

[0005] To prevent further crack growth, it is, for example, possible to machine holes at the crack tips. However, this does not provide any further structural reinforcement of the weld, such that it does not solve the loss of structural integrity.

[0006] Thus, this may be an acceptable solution for a cracked weld if it can be demonstrated that sufficient weld still exists to maintain the structural integrity of the joint, but may be unacceptable in other cases.

[0007] A solution could be to perform a weld repair, by removing the compromised weld and performing a new weld.

[0008] However, performing a weld repair is difficult, in particular because the components are highly irradiated and must remain underwater. For example, the Boiler and Pressure Vessel Code from the American Society of Mechanical Engineers 2023 Edition states that underwater welding may not be used on stainless steel material exposed to specific thermal neutron fluence range. Depending on where the welding would need to be performed relative to the fuel, this may be outside said specific range.

[0009] Another solution is to replace the components.

[0010] However, this is particularly expensive and requires an extended outage duration, beyond the typical refueling outage, to perform the replacement.

[0011] A purpose of the invention is thus to provide a solution to cracked welds in regard to the above disadvantages.

[0012] To achieve this, the object of the invention is a method for reinforcing a weld between two internal parts of a pressurised water reactor vessel, the method comprises providing a reinforcement device comprising: a single reinforcement plate having a coefficient of thermal expansion lower than the coefficient of thermal expansion of each of the two internal parts, said reinforcement plate being connected to each of the internal parts on either side of the weld, more particularly perpendicular to the weld, the reinforcement plate exerting a clamping force between the two internal parts, or two reinforcing plates and at least one connecting rod, a first of the plates being connected to a first of the internal parts, the second plate being connected to a second of the internal parts, the connecting rod being arranged between the two plates, so as to exert a clamping force between the two plates and thus the two internal parts.

[0013] The reinforcement device provides a reinforcement of the weld to compensate for the loss of structural integrity. With the single reinforcement plate having a coefficient of thermal expansion lower than the coefficient of thermal expansion of each of the two internal parts, during heat-up of the system, the reinforcement device will grow less than the components, thus imparting a compressive load contributing to the clamping force. With the two reinforcing plates, the at least one connecting rod exerts a clamping force between the two plates.

[0014] The method may further have one or more of the following features, considered individually or in any technically possible combination:

[0015] - the first plate and the second plate are arranged on either side of the weld, more particularly perpendicular to the weld,

[0016] - the reinforcement device comprises two reinforcing plates, wherein the first part has a first contact surface, the second part having a second contact surface, the first plate abutting against the first contact surface, such that the clamping force presses the first plate against the first contact surface, the second plate abutting against the second contact surface, such that the clamping force presses the second plate against the second contact surface;

[0017] - the weld defines a welding plane, the first contact surface and the second contact surface each extending between a top edge and a bottom edge, wherein the first contact surface is slanted such that the bottom edge is closer to the welding plane than the top edge is and / or the second contact surface is slanted such that the bottom edge is closer to the welding plane than the top edge is, the first plate having a first portion interfacing with the first contact surface, the first portion comprising a shape complementary to that of the first contact surface, the second plate having a second portion interfacing with the second contact surface, the second portion comprising a shape complementary to that of the second contact surface;

[0018] - the first part and the second part are machined to provide the first contact surface and the second contact surface, in particular using electrical discharge machining, before installation of the reinforcement device; - the first plate is screwed to the first part using at least one bolt or screw, and the second plate is screwed to the second part using at least one bolt or screw;

[0019] - the providing of the reinforcement device comprises the following steps in that order: loose screwing the first plate to the first part and the second plate to the second part, inserting the at least one connecting rod between the first plate and the second plate, torquing the at least one connecting rod to its full preload, and torquing the first plate to the first part and the second plate to the second part to its full preload;

[0020] - the first part and the second part are machined to provide holes for screwing the first plate and the second plate, in particular using electrical discharge machining, before installation of the reinforcement device;

[0021] - the first plate and the second plate are machined to provide a passage for the at least one connecting rod;

[0022] - the at least one connecting rod crosses one of the first plate and the second plate and is screwed into the other of the first plate and the second plate, wherein, preferably, after the screwing of the at least one connecting rod, a crimp ring is applied on each connecting rod;

[0023] - the reinforcement device comprises a single reinforcement plate, the first part having a first contact surface, the second part having a second contact surface, the reinforcement plate abutting against the first contact surface and the second contact surface, such that the clamping force presses the reinforcement plate against the first contact surface and the second contact surface;

[0024] - the weld defines a welding plane, the first contact surface and the second contact surface each extending between a top edge and a bottom edge, wherein the first contact surface is slanted such that the bottom edge is closer to the welding plane than the top edge is, and / or the second contact surface is slanted such that the bottom edge is closer to the welding plane than the top edge is, the reinforcement plate having a first portion interfacing with the first contact surface and a second portion interfacing with the second contact surface, the first portion comprising a shape complementary to that of the first contact surface, the second portion comprising a shape complementary to that of the second contact surface;

[0025] - the weld defines a welding plane, the first contact surface being slanted such that one lateral side is closer to the welding plane than the other lateral side is, the second contact surface being slanted such that one lateral side is closer to the welding plane than the other lateral side is, the reinforcement device being provided with jacking screws adapted to provide a force pushing the reinforcement plate away from the lateral sides of the first and second contact surfaces that are closer to the welding plane; and / or - the first part and the second part are machined to provide the first contact surface and the second contact surface, in particular using electrical discharge machining, before installation of the reinforcement device.

[0026] Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, given by way of example only and with reference to the drawings in which:

[0027] [Fig 1] figure 1 is a front view of a weld provided with a reinforcement device according to a first embodiment of the method of the invention,

[0028] [Fig 2] figure 2 is a sectional view along plane II of figure 1 ,

[0029] [Fig 3] figure 3 is a front view of a weld provided with a reinforcement device according to a second embodiment of the method of the invention,

[0030] [Fig 4] figure 4 is a sectional view of figure 3,

[0031] [Fig 5] figure 5 is a front view of a weld provided with a reinforcement device according to a second embodiment of the method of the invention, and

[0032] [Fig 6] figure 6 is a sectional view of figure 5.

[0033] The invention relates to a method for reinforcing a weld between two internal parts of a pressurised water reactor vessel, such as core barrels, core shrouds, core support shields and plenum cylinders.

[0034] A first embodiment of the method of the invention will be described in regard to figures 1 and 2.

[0035] A first part 10 and a second part 12 are previously welded together, such that a weld 14 is arranged between the first part 10 and a second part 12.

[0036] The first part 10 and the second part 12 are here cylindrical where they are welded together.

[0037] The first part 10 and the second part 12 are, for example, made of 18Cr-8Ni stainless steel.

[0038] The compromised (e.g. cracked) weld 14 defines a welding plane P.

[0039] Holes are, for example, machined at the crack tips, to prevent further crack growth.

[0040] The method comprises providing a reinforcement device 16, more particularly on an outer side of the two internal parts of the pressurised water reactor vessel.

[0041] Alternatively, the reinforcement device 16 is provided on an inner side of the two internal parts of the pressurised water reactor vessel.

[0042] Here, the first part 10 is for example, provided with a first contact surface 18, and the second part 12 is, for example, provided with a second contact surface 20. The first contact surface 18 and the second contact surface 20 represent, for example, a portion, in particular less than a sixth of the circumference of the parts, for a circumferential weld, or less than a third of their height, for a longitudinal weld.

[0043] The first part 10 is for example machined to provide the first contact surface 18, and the second part 12 is, for example, machined to provide the second contact surface 20, in particular using electrical discharge machining, before installation of the reinforcement device.

[0044] Thus, the method, for example, comprises a step of machining the first contact surface 18 in the first part 10 and the second contact surface 20 in the second part 12, before installation of the reinforcement device.

[0045] The first contact surface 18 provides a shoulder in the first part 10. The second contact surface 20 provides a shoulder in the second part 12.

[0046] The first contact surface 18 is defined by the first part 10, and the second contact surface 20 is defined by the second part 12.

[0047] The first contact surface 18 is provided by machining an outer surface of the first part 10.

[0048] The second contact surface 20 is provided by machining an outer surface of the second part 12.

[0049] The first contact surface 18 is accessible from a side opposite the weld 14 compared to the first contact surface 18.

[0050] The second contact surface 20 is accessible from a side opposite the weld 14 compared to the second contact surface 20.

[0051] The first contact surface 18 and the second contact surface 20 are, for example, planar.

[0052] The first contact surface 18 and the second contact surface 20 here extend parallel to the welding plane P.

[0053] More precisely, each of the first contact surface 18 and the second contact surface 20 have the shape of a portion of a ring, wherein said ring extends in a plane parallel to the welding plane P.

[0054] The first contact surface 18 and the second contact surface 20 are, for example, orthogonal to the outer surface of the first and second parts 10, 12.

[0055] The first part 10 and the second part 12 are, for example, each provided with holes 22.

[0056] The method, for example, comprises a step of machining the holes 22 in the first part 10 and the second part 12, in particular their outer surface, in particular using electrical discharge machining, before installation of the reinforcement device. The holes are, for example, orthogonal to the outer surface of the first and second parts 10, 12.

[0057] The holes are, here, tapped or threaded.

[0058] In this embodiment, the reinforcement device 16 comprises two reinforcing plates 24, 26 and at least one connecting rod 28.

[0059] A first 24 of the reinforcing plates is configured to be connected to the first part 10, and the second reinforcing plate 26 is configured to be connected to the second part 12.

[0060] The first plate 24 is, for example, made of a single piece.

[0061] The first plate 24 is, for example, a block of material.

[0062] The first plate 24 is, for example, made of material that is the same, similar, or compatible with, the material that part 10 is made of.

[0063] The first plate 24, for example, defines a first portion 30 configured and arranged to interface with the first contact surface 18.

[0064] The term “to interface” means that the two regions are adjacent and lie against each other at a common boundary.

[0065] The first portion 30 comprises a shape complementary to that of the first contact surface 18.

[0066] The first plate 24 for example comprises a circumferential surface 32. The circumferential surface 32 is, for example, adapted to rest against a circumference of the first part 10.

[0067] The first portion 30 is, for example, defined by a portion of the first plate 24 projecting from the circumferential surface 32.

[0068] The first portion 30, for example, defines a surface 34, for example here orthogonal to the circumferential surface 32.

[0069] The surface 34 is, for example, complementary with the first contact surface 18.

[0070] The first portion 30 is, for example, arranged on an edge of the first plate 24.

[0071] The first plate 24, for example, also comprises an abutting surface 36.

[0072] The abutting surface 36 is here parallel to the surface 34.

[0073] The abutting surface 36 and the surface 34 are oriented such that they are defined on opposite sides of the first plate 24.

[0074] The abutting surface 36 is accessible from another side of the first plate 24 compared to surface 34.

[0075] The abutting surface 36 is here arranged on an opposite edge of the first plate 24 compared to the surface 34.

[0076] The first plate 24 here further delimits at least one passage 38 for the at least one connecting rod 28. The at least one passage 38 runs through the first plate 24.

[0077] The at least one passage 38 here extends perpendicularly to the welding plane P.

[0078] The at least one passage 38 here extends perpendicularly to the surface 34.

[0079] The at least one passage 38 here extends perpendicularly to the abutting surface 36.

[0080] The at least one passage 38 opens into the abutting surface 36.

[0081] The at least one passage 38 opens into the face comprising the surface 34.

[0082] The at least one passage 38 is here defined by a cutout in the surface opposite the circumferential surface 32.

[0083] The cutout is, for example, U-shaped.

[0084] The cutout is dimensioned, such that one connecting rod fits into the cutout, on its entire circumference.

[0085] Alternatively, the at least one passage 38 is defined by a through-hole, for example a circular through-hole.

[0086] Here, the first plate is machined to provide said at least one passage 38.

[0087] The first plate 24 here further delimits at least one through-hole 40.

[0088] Each through-hole 40 runs through the first plate 24 perpendicularly to the circumferential surface 32.

[0089] Each through-hole 40 is adapted to receive a screw or bolt.

[0090] Each through-hole 40 comprises a shoulder for the abutment of the head of the screw or bolt.

[0091] The through-holes 40 are arranged, in the first plate, such that, when the first portion 30 interfaces with the first contact surface 18, each through-hole prolongs one of the holes 22, i.e extends in the continuity of said hole.

[0092] The second plate 26 is, for example, made of a single piece.

[0093] The second plate 26 is, for example, a block of material.

[0094] The second plate 26 is, for example, made of material that is the same, similar, or compatible with, the material that part 12 is made of.

[0095] The second plate 26, for example, defines a second portion 42 configured and arranged to interface with the second contact surface 20.

[0096] The second portion 42 comprises a shape complementary to that of the second contact surface 20.

[0097] The second plate 26 for example comprises a circumferential surface 44. The circumferential surface 44 is, for example, adapted to rest against a circumference of the second part 12.

[0098] The second portion 42 is, for example, defined by a portion of the second plate 26 projecting from the circumferential surface 44. The second portion 42, for example, defines a surface 46, for example here orthogonal to the circumferential surface 44.

[0099] The surface 46 is, for example, complementary with the second contact surface 20.

[0100] The second portion 42 is, for example, arranged on an edge of the second plate 26.

[0101] The second plate 26 here further delimits at least one tapped hole 48, more particularly as many tapped holes as the first plate has passages 38.

[0102] The at least one tapped hole 48 here extends perpendicularly to the welding plane P.

[0103] The at least one tapped hole 48 here extends perpendicularly to the surface 46.

[0104] The at least one tapped hole 48 opens into the face comprising the surface 46.

[0105] The at least one tapped hole 48 opens into an edge of the second plate 26, configured to extend facing the first plate 24.

[0106] The at least one tapped hole 48 is arranged in the second plate 26, such that when the first plate 24 and the second plate 26 are positioned, each tapped hole prolongs one of the passages 38, i.e extends in the continuity of said passage.

[0107] Here, the second plate is machined to provide said at least one tapped hole 48.

[0108] The second plate 26 here further delimits at least one through-hole 50.

[0109] Each through-hole 50 runs through the second plate 26 perpendicularly to the circumferential surface 44.

[0110] Each through-hole 50 is adapted to receive a screw or bolt.

[0111] Each through-hole 50 comprises a shoulder for the abutment of the head of the screw or bolt.

[0112] The through-holes 50 are arranged, in the first plate, such that, when the second portion 42 interfaces with the second contact surface 20, each through-hole 50 prolongs one of the holes 22, i.e extends in the continuity of said hole.

[0113] Each connecting rod 28 is, for example, made of a single piece.

[0114] Each connecting rod 28 is, for example, made of a material suitable for the loading required and the environment it will be installed in.

[0115] Each connecting rod 28 comprises a main body 52 extending along a main direction.

[0116] The main body 52 is here cylindrical.

[0117] The main body 52 extends between a free end and a head end along the main direction.

[0118] The main body 52 comprises an end portion comprising the free end, the end portion being threaded.

[0119] The threads of the end portion is configured to interface with the at least one tapped hole 48. Each connecting rod 28 comprises a head 54 extending from or fixed to the head end of the main body 52.

[0120] Here, the head 54 is, for example, a nut, and the main body 52 is a threaded rod or a bolt.

[0121] The head 54 forms a shoulder of the connecting rod 28.

[0122] The providing or installation of the reinforcement device 16, for example, comprises the following steps, here in said order:

[0123] Positioning each plate 24, 26 on the corresponding part 10, 12,

[0124] Inserting the at least one connecting rod 28 between the two plates 24, 26, Screwing the at least one connecting rod 28 to its full preload, and

[0125] Screwing the first plate 24 to the first part 10 and the second plate 26 to the second part 12 to its full preload.

[0126] During the positioning, the first plate 24 is arranged on the first part 10, and the second plate 26 is arranged on the second part 12.

[0127] The first portion 30, more particularly the surface 34, is arranged facing the first contact surface 18.

[0128] The second portion 42, more particularly the surface 46, is arranged facing the second contact surface 20.

[0129] The first plate 24 and the second plate 26 interface with the corresponding parts on either side of the weld 14, more particularly perpendicularly to the welding plane P.

[0130] The first plate 24 and the second plate 26 are arranged on either side of the weld 14, more particularly perpendicular to the weld 14.

[0131] The first plate 24 and the second plate 26 face each other along a direction perpendicular to the welding plane P.

[0132] More particularly, each plate 24, 26 is positioned, in particular such that the through- holes 40, 50 is in the continuity with one hole 22, and loosely screwed on the corresponding part, for example such that the screw head(s) sit on the part.

[0133] The first plate 24 is screwed to the first part 10 using at least one bolt or screw 58, here inserted through the through-holes 40 and screwed into the corresponding holes 22, and the second plate 26 is screwed to the second part 12 using at least one bolt or screw 60, here inserted through the through-holes 50 and screwed into the corresponding holes 22.

[0134] During the inserting of the at least one connecting rod 28, each connecting rod 28 is arranged between the two plates 24, 26. Each connecting rod 28 is inserted through the first plate 24, here through one passage 38, and into the second plate 26, more particularly inserted or screwed into the corresponding tapped-hole 48.

[0135] The at least one connecting rod 28 connects the first plate 24 and the second plate 26, more particularly secures the two plates together.

[0136] Each connecting rod 28 here goes over the weld 14.

[0137] Each connecting rod 28 extends perpendicularly to the welding plane P.

[0138] The at least one connecting rod 28 is then screwed, here into the tapped-hole(s) 48, to its full preload.

[0139] In particular, after said screwing, the head 54 of each connecting rod 28 rests on the abutting surface 36.

[0140] After said screwing, the first portion 30, more particularly the surface 34, abuts against the first contact surface 18, and the second portion 42, more particularly the surface 46, abuts against the second contact surface 20.

[0141] The first portion 30 interfaces with the first contact surface 18.

[0142] The second portion 42 interfaces with the second contact surface 20.

[0143] Advantageously, each connecting rod 28, here more particularly each head 54, is surrounded by a crimp ring 56, and after screwing the at least one connecting rod 28, a crimp is applied on the crimp ring 56 surrounding each connecting rod 28, here on each head 54, such as to prevent any rotation of the corresponding connecting rod precluding loosening of the joint.

[0144] Each connecting rod 28, here on each head 54, comprises at least one indexing surface, for example groove, that the crimp ring 56 deforms into when crimped.

[0145] After screwing the at least one connecting rod 28 to its full preload, the first plate 24 is screwed to the first part 10 to its full preload, and the second plate 26 is screwed to the second part 12 to its full preload. More particularly, the at least one bolt or screw previously loosely screwed are now screwed to their full preload.

[0146] In a particular embodiment, each head of the bolt or screw 58, 60 is surrounded by a crimp ring, and, after screwing to full preload, a crimp is applied on said crimp rings.

[0147] The at least one connecting rod 28 exerts a clamping force between the two plates 24, 26.

[0148] The first plate 24 abuts against the first contact surface 18, such that the clamping force presses the first plate 24 against the first contact surface 18.

[0149] The second plate 26 abuts against the second contact surface 20, such that the clamping force presses the second plate 26 against the second contact surface 20. Thus, the clamping force presses the first contact surface 18 and the second contact surface 20 together.

[0150] A second embodiment of a method of the invention will now be described in regard to figures 3 and 4.

[0151] Only the features by which the embodiments differ will be described.

[0152] Similar features are labeled with the same number incremented by 100.

[0153] Here, the first contact surface 118 and the second contact surface 120 do not extend parallel to the welding plane P.

[0154] The first contact surface 1 18 and the second contact surface 120 each extend between a top edge and a bottom edge.

[0155] Here, the first contact surface 118 is a flat plane, and the second contact surface 120 is a flat plane.

[0156] The first contact surface 1 18 is slanted such that the bottom edge is closer to the welding plane P than the top edge is.

[0157] The first contact surface 118 is slanted, in particularly radially, or here in the thickness of the first part 110.

[0158] The second contact surface 120 is slanted such that the bottom edge is closer to the welding plane P than the top edge is.

[0159] The second contact surface 120 is slanted, in particularly radially, or here in the thickness of the second part 1 12.

[0160] Here, the first part 110 is provided with a first recess 1 17.

[0161] The first contact surface 118 corresponds to the face of the first recess 1 17 closest to the welding plane P of the weld 114.

[0162] The first recess 117 further defines a back surface 119, here corresponding to the bottom of the first recess 117.

[0163] The back surface 1 19 extends from the bottom edge of the first contact surface 1 18 and away from the welding plane P, more particularly perpendicularly to the welding plane P.

[0164] The back surface 1 19 is, for example, a flat plane.

[0165] The first recess 1 17, including the first contact surface 118 is provided by machining an outer surface of the first part 110.

[0166] Thus, the method, for example, comprises a step of machining the first contact surface 1 18, here the first recess 117, in the first part 1 10, in particular using electrical discharge machining, before the providing of the reinforcement device.

[0167] Here, the second part 112 is provided with a second recess 121. The second contact surface 120 corresponds to the face of the second recess 121 closest to the welding plane P.

[0168] The second recess 121 further defines a back surface 123, here corresponding to the bottom of the second recess 121.

[0169] The back surface 123 extends from the bottom edge of the second contact surface 120 and away from the welding plane P, more particularly perpendicularly to the welding plane P.

[0170] The back surface 123 is, for example, a flat plane.

[0171] The second recess 121 , including the second contact surface 120 is provided by machining an outer surface of the second part 112.

[0172] Thus, the method, for example, comprises a step of machining the second contact surface 120, here the second recess 121 , in the second part 1 12, before the providing of the reinforcement device.

[0173] Alternatively, only one of the first contact surface 118 and the second contact surface 120 is slanted.

[0174] The first part 110 and the second part 1 12 are here devoid of the holes 22 as described in the first embodiment.

[0175] The first plate 124 is, for example, made of a single piece.

[0176] The first plate 124 is made of a material suitable for the loading required and adapted to the environment it will be installed in.

[0177] The first plate 124 is, for example, made of Inconel® Alloy 690.

[0178] The first portion 130 of the first plate 124 is configured and arranged to interface with the first contact surface 1 18, more particularly with the first contact surface 118 and the back surface 1 19.

[0179] The first portion 130 comprises a shape complementary to that of the first contact surface 1 18, and here the back surface 119.

[0180] The first portion 130 protrudes from the rest of the first plate 124.

[0181] More particularly, the rest of the first plate 124 is a block of material, the first portion 130 protruding from a side of the block.

[0182] The first portion 130, for example, defines a surface 134 adapted to interface with the first contact surface 1 18.

[0183] The abutting surface 136 is here parallel to the welding plane P.

[0184] The abutting surface 136 and the surface 134 are oriented such that there are defined on opposite sides of the first plate 124.

[0185] The abutting surface 136 is accessible from another side of the first plate 124 compared to surface 134. The at least one passage 138 here extends perpendicularly to the abutting surface

[0186] 136.

[0187] Similar to the first embodiment, the at least one passage 138 runs through the first plate 124.

[0188] The at least one passage 138 opens into the abutting surface 136.

[0189] Here, the at least one passage 138 is defined by a through-hole, for example a circular through-hole.

[0190] Alternatively, the at least one passage 138 is defined by a cutout, as described previously, in the surface opposite the back surface 1 19.

[0191] The first plate 124 is not provided with through-holes 40 as described in regard to the first embodiment.

[0192] The second plate 126 is, for example, made of a single piece.

[0193] The second plate 126 is made of a material suitable for the loading required and adapted to the environment it will be installed in.

[0194] The second plate 126 is, for example, made of Inconel® Alloy 690.

[0195] The second portion 142 of the second plate 126 is configured and arranged to interface with the second contact surface 120, more particularly with the second contact surface 120 and the back surface 123.

[0196] The second portion 142 comprises a shape complementary to that of the second contact surface 120, and here the back surface 123.

[0197] The second portion 142 protrudes from the rest of the second plate 126.

[0198] More particularly, here, the second plate is L-shaped, the second portion 142 being defined by a branch of the L

[0199] The second portion 142, for example, defines a surface 146, adapted to interface with the second contact surface 120.

[0200] The at least one tapped hole 148 here extends perpendicularly to the welding plane P.

[0201] The at least one tapped hole 148 opens into an edge of the second plate 126, configured to extend facing the first plate 124.

[0202] Similar to the first embodiment, the at least one tapped hole 148 is arranged in the second plate 126, such that when the first plate 124 and the second plate 126 are positioned, each tapped hole prolongs one of the passages 138, i.e extends in the continuity of said passage.

[0203] The second plate 126 is not provided with through-holes 50 as described in regard to the first embodiment.

[0204] The at least one connecting rod 128 is similar to that of the first embodiment. The or each connecting rod 128 is, for example, a screw.

[0205] The providing or installation of the reinforcement device 1 16, for example, comprises the following steps:

[0206] - Positioning each plate 124, 126 on the corresponding part 1 10, 1 12, Inserting the least one connecting rod 128 between the two plates 124, 126, and

[0207] - Torquing the at least one connecting rod 128 to its full preload.

[0208] During the installation, the first plate 124 is arranged on the first part 1 10, and the second plate 126 is arranged on the second part 112.

[0209] The first portion 130, more particularly the surface 134, is arranged in regard to the first contact surface 1 18.

[0210] Here, the first portion 130 is arranged in the recess 1 17, such that the surface 134 lies facing the first contact surface 1 18.

[0211] The second portion 142, more particularly the surface 146, is arranged in regard to the second contact surface 120.

[0212] Here, the second portion 142 is arranged in the recess 121 , such that the surface 146 lies facing the second contact surface 120.

[0213] The first plate 124 and the second plate 126 face each other along a direction perpendicular to the welding plane P.

[0214] The first plate 124 and the second plate 126 interface with the corresponding parts on either side of the weld 114, more particularly perpendicularly to the welding plane P.

[0215] During the inserting of the at least one connecting rod 128, each connecting rod 128 is arranged between the two plates 124, 126.

[0216] Each connecting rod 128 is inserted through the first plate 124 through a passage 138 and into the second plate 126, more particularly inserted or screwed into the corresponding tapped-hole 148.

[0217] The at least one connecting rod 128 connects the first plate 124 and the second plate 126, more particularly secures the two plates together.

[0218] Each connecting rod 128 extends perpendicularly to the welding plane P.

[0219] Here, the second plate 126 goes over the weld 114.

[0220] Alternatively, the shapes of the first plate 124 and the second plate 126 are reversed such that the first plate 124 extends above the weld 1 14.

[0221] Alternatively, the general shapes of the first plate and the second plate are similar to that of the first embodiment, so that the at least one connecting rod 128 extends above the weld. The at least one connecting rod 128 is then torqued, here into the tapped-hole(s) 148, to its full preload. For example, the application of preload starts by torquing a central connecting rod 128 and then torquing the other connecting rods 128.

[0222] In particular, after said torquing, the head 154 of each connecting rod 128 rests on the abutting surface 136.

[0223] After said torquing, the first portion 130, more particularly the surface 134, abuts against the first contact surface 1 18, and the second portion 142, more particularly the surface 146, abuts against the second contact surface 120.

[0224] The first portion 130 interfaces with the first contact surface 118, and here the back surface 1 19.

[0225] The second portion 142 interfaces with the second contact surface 120 and here the back surface 123.

[0226] Advantageously, after torquing the at least one connecting rod 128, a crimp ring 156 is applied on the or each connecting rod 128, here on each head 154, such as to prevent any rotation of the corresponding connecting rod, as described previously.

[0227] The at least one connecting rod 128 exerts a clamping force between the two plates 124, 126.

[0228] The first plate 124 abuts against the first contact surface 118, such that the clamping force presses the first plate 124 against the first contact surface 1 18.

[0229] The second plate 126 abuts against the second contact surface 120, such that the clamping force presses the second plate 126 against the second contact surface 120.

[0230] Thus, the clamping force presses the first contact surface 118 and the second contact surface 120 together.

[0231] In an alternative embodiment, the first plate and the second plate has the general shape as in the second embodiment but with through-holes 40, 50, and each plate is fastened to a corresponding part as in the first embodiment.

[0232] A third embodiment of a method of the invention will now be described in regard to figures 5 and 6.

[0233] A first part 210 and a second part 212 are previously welded together, such that a weld 214 is arranged between the first part 210 and a second part 212.

[0234] The first part 210 and the second part 212 are here cylindrical where they are welded together.

[0235] The first part 210 and the second part 212 are, for example, made of stainless steel, in particular of 18Cr-8Ni stainless steel.

[0236] The weld 214 defines a welding plane P.

[0237] The weld 214 is, for example, made of stainless steel. The material of the weld 214, for example, has the same thermal expansion as the material of the first part 210 and the second part 212.

[0238] The weld has defaults. For example, the weld is cracked.

[0239] Holes are, for example, machined at the crack tips, to prevent further crack growth.

[0240] The method comprises providing a reinforcement device 216, more particularly on an outer side of the two internal parts of the pressurised water reactor vessel.

[0241] Here, the first part 210 is for example, provided with a first contact surface 218, and the second part 212 is, for example, provided with a second contact surface 220.

[0242] Here, the first part 210 is provided with a first recess 217.

[0243] The first contact surface 218 corresponds to the face of the first recess 217 closest to the welding plane P of the weld 214.

[0244] The first contact surface 218 extends between a top edge and a bottom edge.

[0245] The first contact surface 218 is, for example, a flat plane.

[0246] The first contact surface 218 extends between two lateral sides, in the direction parallel to the weld 214, here in the circumferential direction.

[0247] The first recess 217 further defines a back surface 219, here corresponding to the bottom of the first recess 217.

[0248] The first recess 217, including the first contact surface 218, is, for example, provided by machining the first part 110, in particular its outer surface.

[0249] Thus, the method, for example, comprises a step of machining the first contact surface 218, here the first recess 217, in the first part 210, in particular using electrical discharge machining, before the installation of the reinforcement device.

[0250] The back surface 219 extends from the bottom edge of the first contact surface 218 and away from the welding plane P, more particularly perpendicularly to the welding plane P.

[0251] Here, the first contact surface 218 is slanted, more particularly in two directions, in particular radially, or here in the thickness of the first part 210, and in the direction of the weld 214, here in a direction tangent to the circumference of the outer surface of part 210.

[0252] The first contact surface 218 is slanted such that the bottom edge is closer to the welding plane P than the top edge is, in particular in each radial plane.

[0253] The first contact surface 218 is further slanted such that one lateral side is closer to the welding plane P than the other lateral side is, in particular for each depth measured perpendicularly to the back surface 219 considering the distances at said depth.

[0254] Here, the second part 212 is provided with a second recess 221.

[0255] The second contact surface 220 corresponds to the face of the second recess 221 closest to the welding plane P. The second contact surface 220 extends between a top edge and a bottom edge.

[0256] The second contact surface 220 is, for example, a flat plane.

[0257] The second contact surface 220 extends between two lateral sides, in the direction parallel to the weld 214, here in the circumferential direction.

[0258] The second recess 221 further defines a back surface 223, here corresponding to the bottom of the second recess 221 .

[0259] The second recess 221 , including the second contact surface 220, is, for example, provided by machining the second part 212, in particular its outer surface.

[0260] Thus, the method, for example, comprises a step of machining the second contact surface 220, here the second recess 221 , in the second part 212, in particular using electrical discharge machining, before installation of the reinforcement device.

[0261] The back surface 223 extends from the bottom edge of the second contact surface 220 and away from the welding plane P, more particularly perpendicularly to the welding plane P.

[0262] The back surface 223 is, for example, a flat plane.

[0263] Here, the second contact surface 220 is slanted, more particularly in two directions, in particular radially, or here the thickness of the second part 212, and in the direction of the weld 214, here in the direction tangent to the circumference of the outer surface of part 210.

[0264] The second contact surface 220 is slanted such that the bottom edge is closer to the welding plane P than the top edge is, in particular in each radial plane.

[0265] The second contact surface 220 is slanted such that one lateral side is closer to the welding plane P than the other lateral side is, in particular for each depth measured perpendicularly to the back surface 223 considering the distances at said depth.

[0266] Alternatively, only one of the first contact surface 218 and the second contact surface 220 is slanted.

[0267] In this embodiment, the reinforcing device 216 comprises a single reinforcement plate 224.

[0268] The reinforcement plate 224 is, for example, made of a single piece.

[0269] The reinforcement plate 224 has a coefficient of thermal expansion lower than the coefficient of thermal expansion of each of the two internal parts 212, 214, in particular lower of at least 1.1 times, in particular of at least 1.19 times.

[0270] Here, the mean coefficient of thermal expansion going from 70°F to 650°F for the first part and the second part is, here, in general equal to 9.9 x 106in. / in. / °F.

[0271] The mean coefficient of thermal expansion going from 70°F to 650°F for the reinforcement plate is, here, in general equal to 8.3 x 106in. / in. / °F.

[0272] Here, the reinforcement plate 224 is, for example, made oflnconel® Alloy 690. The reinforcement plate 224 comprises a first portion 230 adapted to interface with the first contact surface 218 and a second portion 242 adapted to interface with the second contact surface 220.

[0273] Here, the reinforcement plate 224 extends between a first end portion comprising the first portion 230 and a second end portion comprising the second portion 242, the first end portion and the second end portion being separated along a direction of extension of the reinforcement plate 224.

[0274] The first portion 230 and the second portion 242 are each defined by a respective protrusion of the reinforcement plate 224, the protrusions facing each other, in particular along the direction of extension of the reinforcement plate 224.

[0275] Here, the reinforcement plate 224 comprises a main portion, the main portion for example defining an interior surface 232.

[0276] The interior surface 232 is, for example, flat.

[0277] The interior surface 232 is, for example, adapted to be arranged facing the internal parts 210, 212, when the reinforcement device 216 is provided for reinforcing the weld 214.

[0278] The first portion 230 and the second portion 242 are delimited by protrusions extending from the main portion, the protrusions protruding from the interior surface 232, for example at opposite sides along the direction of extension of the reinforcement plate 224.

[0279] The first portion 230 comprises a shape complementary to that of the first contact surface 218, and here the back surface 219.

[0280] The first portion 230 is here narrower than the first contact surface 218, more precisely than the first recess 217, in particular such that when the first portion 230 interfaces with the first contact surface 218, there is a space next to a lateral side of the first portion 230 in the first recess 217.

[0281] The first portion 230, for example, defines a surface 234 adapted to interface with the first contact surface 218.

[0282] The second portion 242 comprises a shape complementary to that of the second contact surface 220, and here the back surface 223.

[0283] The second portion 242 is here narrower than the second contact surface 220, more precisely than the second recess 221 , in particular such that when the second portion 242 interfaces with the second contact surface 220, there is a space next to a lateral side of the second portion 242 in the second recess 221.

[0284] The second portion 242, for example, defines a surface 246 adapted to interface with the second contact surface 220. Each of the first portion 230 and the second portion 242 comprises a hole 248, 250, more particularly a blind hole 248, 250.

[0285] Each hole 248, 250 opens into a side of the corresponding portion 230, 242, said side being arranged such that it faces a lateral side of the corresponding contact surface 218, 220 when the corresponding portion 230, 242 interfaces with the corresponding contact surface 218, 220.

[0286] In particular, each hole 248, 250 opens into the side of the corresponding portion 230, 242, where the corresponding portion 230, 242 are closest to each other in regard to the direction of extension of the reinforcement plate 224.

[0287] Each hole 248, 250, for example, extends perpendicularly to the direction of extension of the reinforcement plate.

[0288] Each hole 248, 250 is, for example, cylindrical.

[0289] Each hole 248, 250 is, for example, at least partly tapped or threaded.

[0290] The providing or installation of the reinforcement device 216 comprises positioning the reinforcement plate 224 on the parts 210, 212.

[0291] Here, the installation of the reinforcement device 216 comprises the following steps, here in said order: positioning the reinforcement plate 224 on the parts 210, 212, and moving the reinforcement plate 224 away from the lateral sides 264, 266 of the first and second contact surfaces 218, 220 that are closer to the welding plane P.

[0292] Advantageously, the installation of the reinforcement device 216 further comprises the step of securing the position of the reinforcement plate 224 after the moving step.

[0293] More precisely, the installation of the reinforcement device 216 comprises the following steps, here in said order:

[0294] - providing jacking screws 252, 254 interfacing with the reinforcement plate 224, the jacking screws 252, 254 being displaceable between a retracted position and an extended position in the reinforcement plate 224, the jacking screws 252, 254 being placed in the retracted position,

[0295] - positioning the reinforcement plate 224 on the parts 210, 212, and

[0296] - moving the jacking screws 252, 254 into the extended position.

[0297] Advantageously, the installation of the reinforcement device 216 further comprises the step of securing the jacking screws 252, 254 in the extended position, after the moving of the jacking screws 252, 254 into the extended position.

[0298] The jacking screws 252, 254 are preinstalled on the reinforcement plate 224 before the positioning of the reinforcement part 224 on the parts 210, 212. Installing jacking screws 252, 254 comprises installing a first jacking screw 252 interfacing with the hole 248 delimited by the first portion 230 and a second jacking screw 254 interfacing with the hole 250 delimited by the second portion 242.

[0299] Each jacking screw 252, 254 is partially inserted, in particular here, screwed into a corresponding hole 248, 250, respectively.

[0300] Each jacking screw 252, 254 is displaceable between the retracted position and the extended position, by moving said jacking screw 252, 254 in the corresponding hole 248, 250.

[0301] In the retracted position, the length of the portions 230, 242 and the jacking screws 252, 254 are sufficiently less than that of the recesses 217, 221 , such that clearance exists between the surfaces 234, 246 of portions 230, 242, respectively, and surfaces 218, 220 of recesses 217, 221 , respectively when the reinforcement plate is positioned on the parts 210, 212.

[0302] The length is here measured parallel to the welding plane P when the portions 230, 242 interface with the contact surface 218, 220, respectively.

[0303] This allows an easy insertion of the portions 230, 242 with the jacking screw 252, 254 inside the recesses 217, 221 , respectively, during the positioning of the reinforcement plate 224.

[0304] In the extended position, the length of the portions 230, 242 and the jacking screws 252, 254 is sufficient to create zero clearance between surfaces 234, 246 of portions 230, 242, respectively, and surfaces 218, 220 of recesses 217, 221 , respectively.

[0305] The jacking screws 252, 254 are here placed in the retracted position before the positing of the reinforcement part 224 on the parts 210, 212.

[0306] The reinforcement plate 224 is positioned onto the parts 210, 212, such that the first portion 230 faces the first contact surface 218 and the second portion 242 faces the second contact surface 220.

[0307] The first portion 230 is inserted inside the first recess 217, such that the surface 234 lies facing the first contact surface 218, and the second portion 242 is inserted inside the second recess 221 , such that the surface 246 lies facing the second contact surface 220.

[0308] Each jacking screw 252, 254 is arranged in regard to a respective lateral surface 260, 262 of the corresponding recess 217, 221 .

[0309] The jacking screws 252, 254 are then moved to their respective extended position.

[0310] Thus, the jacking screws 252, 254 are extended until they apply a force against the lateral surfaces 260, 262.

[0311] Each jacking screw 252, 254 then rests against the respective lateral surface 260, 262 of the corresponding recess 217, 221. Thus, there is no clearance between the jacking screws 252, 254 and the respective lateral surface 260, 262.

[0312] In one embodiment, an external force may be applied to the reinforcement plate 224 in the direction away from the surfaces 260,262 to fully engage surfaces 234, 246 with surfaces 218, 220, respectively, prior to extending the jacking screws 252 and 254.

[0313] This pushes the reinforcement plate 224 away from the lateral sides 264, 266 of the first and second contact surfaces 218, 220 where they are closer to the welding plane P.

[0314] With the slant, this pushes the first portion 230, more precisely the surface 234, against the first contact surface 218, and the second portion 242, more precisely the surface 246, against the second contact surface 220, providing a clamping force.

[0315] The step of securing the jacking screws 252, 254 in the extended position comprises screwing each jacking screw in the extended position.

[0316] For example, radial holes, and respectively securing holes, are machined in each jacking screw 252, 254, respectively in the reinforcement plate 224 , for example using electrical discharge machining, after the moving of the jacking screws 252, 254 into the extended position, such that each securing hole prolongs one of the radial hole.

[0317] The radial holes are preferably threaded.

[0318] The machining of the holes after the extension of the jacking screws avoids the risk of the holes not being aligned, if the preliminary calculations for positioning the holes are not accurate.

[0319] During the securing, an indexing element, for example a screw or a pin, is inserted, for example screwed, in each radial hole and the corresponding securing hole.

[0320] The reinforcement plate 224 is here connected to each of the internal parts 210, 212, on either side of the weld 214, more particularly perpendicular to the weld 214, in particular the welding plate P.

[0321] The reinforcement plate 224 exerts a clamping force between the two parts 210, 212.

[0322] The reinforcement plate 224 abuts against the first contact surface 218 and the second contact surface 220, such that the clamping force presses the reinforcement plate 224 against the first contact surface 218 and the second contact surface 220, and the first contact surface 218 and the second contact surface 220 together.

[0323] Furthermore, when in use, the temperature surrounding the first part 210, the second part 212, and the reinforcement device 216 increases to a temperature of operation.

[0324] As the reinforcement plate has a coefficient of thermal expansion lower than the coefficient of thermal expansion of each of the two internal parts, the reinforcement device will grow less than the first part and the second part, thus imparting a compressive load contributing to the clamping force. Thus, the different embodiments of the method of the invention allows reinforcing the weld.

Claims

CLAIMS1.- Method for reinforcing a weld (14; 1 14; 214) between two internal parts (10, 12; 110, 112; 210, 212) of a pressurised water reactor vessel, the method comprises providing a reinforcement device (16; 116; 216) comprising: a single reinforcement plate (224) having a coefficient of thermal expansion lower than the coefficient of thermal expansion of each of the two internal parts (210, 212), said reinforcement plate (224) being connected to each of the internal parts (210, 212) on either side of the weld (214), more particularly perpendicular to the weld (214), the reinforcement plate (224) exerting a clamping force between the two internal parts (210, 212), or two reinforcing plates (24, 26; 124, 126) and at least one connecting rod (28; 128), a first of the reinforcing plates (24; 124) being connected to a first of the internal parts (10; 1 10), the second reinforcing plate (26, 126) being connected to a second of the internal parts (12; 112), the connecting rod (28; 128) being arranged between the two reinforcing plates (24, 26; 124, 126), so as to exert a clamping force between the two reinforcing plates (24, 26; 124, 126) and thus the two internal parts (10, 12; 1 10, 112).2.- Method according to claim 1 , wherein the reinforcement device (16; 1 16) comprises two reinforcing plates (24, 26; 124, 126), wherein the first part (10; 1 10) has a first contact surface (18; 1 18), the second part (12; 1 12) having a second contact surface (20; 120), the first plate (24; 124) abutting against the first contact surface (18; 118), such that the clamping force presses the first plate (24; 124) against the first contact surface (18; 118), the second plate (26; 126) abutting against the second contact surface (20; 120), such that the clamping force presses the second plate (26; 126) against the second contact surface (20; 120).3.- Method according to claim 2, wherein the weld (114) defines a welding plane (P), the first contact surface (118) and the second contact surface (120) each extending between a top edge and a bottom edge, wherein the first contact surface (118) is slanted such that the bottom edge is closer to the welding plane (P) than the top edge is and / or the second contact surface (120) is slanted such that the bottom edge is closer to the welding plane (P) than the top edge is, the first plate (124) having a first portion (130) interfacing with the first contact surface (118), the first portion (130) comprising a shape complementary to that of the first contact surface (1 18), the second plate (126) having a second portion (142)interfacing with the second contact surface (120), the second portion (142) comprising a shape complementary to that of the second contact surface (120).4.- Method according to claim 2 or 3, wherein the first part (10; 110) and the second part (12; 112) are machined to provide the first contact surface (18; 1 18) and the second contact surface (20; 120), in particular using electrical discharge machining, before installation of the reinforcement device (16; 116).5.- Method according to any of claims 1 to 4, wherein the first plate (24) is screwed to the first part (10) using at least one bolt or screw, and the second plate (26) is screwed to the second part (12) using at least one bolt or screw.6.- Method according to claim 5, wherein the providing of the reinforcement device (16) comprises the following steps in that order: loose screwing the first plate (24) to the first part (10) and the second plate (26) to the second part (12), inserting the at least one connecting rod (28) between the first plate (24) and the second plate (26), torquing the at least one connecting rod (28) to its full preload, and torquing the first plate (24) to the first part (10) and the second plate (26) to the second part (12) to its full preload.7.- Method according to claim 5 or 6, wherein the first part (10) and the second part (12) are machined to provide holes (22) for screwing the first plate (24) and the second plate (26), in particular using electrical discharge machining, before installation of the reinforcement device (16).8.- Method according to any one of claims 1 to 7, wherein the first plate (24; 124) and the second plate (26; 126) are machined to provide a passage (38; 138, 48; 148) for the at least one connecting rod (28; 128).9.- Method according to any one of claims 1 to 8, wherein the at least one connecting rod (28; 128) crosses one of the first plate (24; 124) and the second plate (26; 126) and is screwed into the other of the first plate (24; 124) and the second plate (26; 126), wherein, preferably, after the screwing of the at least one connecting rod (28; 128), a crimp ring (56; 156) is applied on each connecting rod (28; 128).10.- Method according to claim 1 , wherein the reinforcement device (216) comprises a single reinforcement plate (224), the first part (210) having a first contact surface (218),the second part (212) having a second contact surface (220), the reinforcement plate (224) abutting against the first contact surface (218) and the second contact surface (220), such that the clamping force presses the reinforcement plate (224) against the first contact surface (218) and the second contact surface (220).11.- Method according to claim 10, wherein the weld (214) defines a welding plane (P), the first contact surface (218) and the second contact surface (220) each extending between a top edge and a bottom edge, wherein the first contact surface (218) is slanted such that the bottom edge is closer to the welding plane (P) than the top edge is, and / or the second contact surface (220) is slanted such that the bottom edge is closer to the welding plane (P) than the top edge is, the reinforcement plate (224) having a first portion (230) interfacing with the first contact surface (218) and a second portion (242) interfacing with the second contact surface (220), the first portion (230) comprising a shape complementary to that of the first contact surface (218), the second portion (242) comprising a shape complementary to that of the second contact surface (220).12.- Method according to claim 10 or 1 1 , wherein the weld (214) defines a welding plane (P), the first contact surface (218) being slanted such that one lateral side is closer to the welding plane (P) than the other lateral side is, the second contact surface (220) being slanted such that one lateral side is closer to the welding plane (P) than the other lateral side is, the reinforcement device (216) being provided with jacking screws (252, 254) adapted to provide a force pushing the reinforcement plate (224) away from the lateral sides (264, 266) of the first and second contact surfaces (218, 220) that are closer to the welding plane (P).13.- Method according to any one of claims 10 to 12, wherein the first part (210) and the second part (212) are machined to provide the first contact surface (218) and the second contact surface (220), in particular using electrical discharge machining, before installation of the reinforcement device (216).

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