Patent Publication Number: US-10760603-B2

Title: Apparatuses and methods for structurally replacing cracked welds in nuclear power plants

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of, and claims priority under 35 U.S.C. § 120 to, U.S. application Ser. No. 15/481,788, filed Apr. 7, 2017, which is a divisional of, and claims priority under 35 U.S.C. § 120 to, U.S. application Ser. No. 14/184,884, filed Feb. 20, 2014. The entire contents of each of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     Example embodiments generally relate to apparatuses and methods for structurally replacing cracked welds. Example embodiments also relate to nuclear power plants and to apparatuses and methods for structurally replacing cracked welds of the nuclear power plants. 
     2. Description of Related Art 
     In many applications, such as nuclear reactors, steam driven turbines, or water deaerators, high-temperature water may adversely affect the associated structures by contributing to stress corrosion cracks, corrosion, erosion, and so forth. For example, high temperature waters may contribute to stress corrosion cracking (“SCC”) in materials, such as carbon steels, alloy steels, stainless steels, nickel-based alloys, cobalt-based alloys, and zirconium-based alloys. SCC may preferentially occur with certain combinations of alloys, environment, and stress. 
     As would be understood by a person having ordinary skill in the art (“PHOSITA”), SCC may include cracks propagated by static or dynamic tensile stresses acting in combination with corrosion at crack tips. These stresses may result or originate from differences in thermal expansion or contraction between components, relatively high or varying operating pressures, or various processes performed during the manufacture and assembly of the components or system. For example, residual stresses often result from cold working, grinding, machining, and other thermo-mechanical metal treatments. Water chemistry, welding, heat treatment, and radiation may also increase the susceptibility of metal or alloy component to SCC. SCC may be transgranular or intergranular in nature. 
     SCC may occur at greater rates under various conditions, such as the presence of oxygen, high radiation flux, and so forth. In nuclear reactors such as a pressurized water reactor (“PWR”) or a boiling water reactor (“BWR”), high radiation flux may cause radiolytic decomposition of the reactor coolant (water); this decomposition may produce oxygen, hydrogen peroxide, short-lived radicals, and various oxidizing species. These products of radiolytic decomposition may promote SCC in the various system components, such as pipes, pumps, valves, turbines, and so forth. Operating temperature and pressure for a BWR may be about 300° C. and about 10 MPa, and those for a PWR may be about 325° C. and about 15 MPa. Thus, the operating environment for BWRs and PWRs may increase the risk of having SCC issues in nuclear reactor components. 
     The microstructure of metals and alloys may include grains separated by grain boundaries. Intergranular stress corrosion cracking (“IGSCC”) may be a more localized SCC attack along or adjacent to grain boundaries, with the bulk of the grains themselves remaining largely unaffected. IGSCC may be associated with chemical segregation effects (e.g., impurity enrichment at grain boundaries) or with specific phases precipitated at grain boundaries. 
     Irradiation assisted stress corrosion cracking (“IASCC”) may refer to acceleration of SCC by irradiation (e.g., irradiation-induced changes that may involve microstructure changes, microchemical changes, and compositional changes by transmutation). IASCC may result from the effects of beta radiation, gamma radiation, neutron radiation, or other particle radiation (e.g., ions). However, for BWRs and PWRs, IASCC may be primarily due to neutron radiation. 
     Due to the serious nature of IASCC, the Nuclear Regulatory Commission (“NRC”) commissioned a series of studies over about a ten-year period. Some of the reports coming out of these studies included NUREG/CR 5608, “Irradiation-Assisted Stress Corrosion Cracking of Model Austenitic Stainless Steels Irradiated in the Halden Reactor”; NUREG/CR-6892, “Fracture Toughness and Crack Growth Rates of Irradiated Austenitic Stainless Steels”; NUREG/CR-6687, “Irradiation-Assisted Stress Corrosion Cracking of Model Austenitic Stainless Steel Alloys”; NUREG/CR-6915, “Irradiation-Assisted Stress Corrosion Cracking of Austenitic Stainless Steels and Alloy 690 from Halden Phase-II Irradiations”; NUREG/CR-6960, “Crack Growth Rates and Fracture Toughness of Irradiated Austenitic Stainless Steels in BWR Environments”; and NUREG/CR-7018, “Irradiation-Assisted Stress Corrosion Cracking of Austenitic Stainless Steels in BWR Environments”. 
       FIG. 1  is a sectional view, with parts cut away, of reactor pressure vessel (“RPV”)  100  in a related art BWR. 
     During operation of the BWR, coolant water circulating inside RPV  100  may be heated by nuclear fission produced in core  102 . Feedwater may be admitted into RPV  100  via feedwater inlet  104  and feedwater sparger  106  (a ring-shaped pipe that may include apertures for circumferentially distributing the feedwater inside RPV  100 ). The feedwater from feedwater sparger  106  may flow down through downcomer annulus  108  (an annular region between RPV  100  and core shroud  110 ). 
     Core shroud  110  may be a stainless steel cylinder that surrounds core  102 . Core  102  may include a multiplicity of fuel bundle assemblies  112  (two 2×2 arrays, for example, are shown in  FIG. 1 ). Each array of fuel bundle assemblies  112  may be supported at or near its top by top guide  114  and/or at or near its bottom by core plate  116 . Top guide  114  may provide lateral support for the top of fuel bundle assemblies  112  and/or may maintain correct fuel-channel spacing to permit control rod insertion. 
     The feedwater/coolant water may flow downward through downcomer annulus  108  and/or into core lower plenum  118 . The coolant water in core lower plenum  118  may in turn flow up through core  102 . The coolant water may enter fuel assemblies  112 , wherein a boiling boundary layer may be established. A mixture of water and steam may exit core  102  and/or may enter core upper plenum  120  under shroud head  122 . Core upper plenum  120  may provide standoff between the steam-water mixture exiting core  102  and entering standpipes  124 . Standpipes  124  may be disposed atop shroud head  122  and/or in fluid communication with core upper plenum  120 . 
     The steam-water mixture may flow through standpipes  124  and/or may enter steam separators  126  (which may be, for example, of the axial-flow, centrifugal type). Steam separators  126  may substantially separate the steam-water mixture into liquid water and steam. The separated liquid water may mix with feedwater in mixing plenum  128 . This mixture then may return to core  102  via downcomer annulus  108 . The separated steam may pass through steam dryers  130  and/or may enter steam dome  132 . The dried steam may be withdrawn from RPV  100  via steam outlet  134  for use in turbines and other equipment (not shown). 
     The BWR also may include a coolant recirculation system that provides the forced convection flow through core  102  necessary to attain the required power density. A portion of the water may be sucked from the lower end of downcomer annulus  108  via recirculation water outlet  136  and/or may be forced by a centrifugal recirculation pump (not shown) into a plurality of jet pump assemblies  138  (only one of which is shown) via recirculation water inlets  140 . Jet pump assemblies  138  may be circumferentially distributed around core shroud  110  and/or may provide the required reactor core flow. 
     As shown in  FIG. 1 , a related art jet pump assembly  138  may include a pair of inlet mixers  142 . A related art BWR may include  16  to  24  inlet mixers  142 . Each inlet mixer  142  may have an elbow  144  welded to it that receives water from a recirculation pump (not shown) via inlet riser  146 . An example inlet mixer  142  may include a set of five nozzles circumferentially distributed at equal angles about the axis of inlet mixer  142 . Each nozzle may be tapered radially inwardly at its outlet. Jet pump assembly  138  may be energized by these convergent nozzles. Five secondary inlet openings may be radially outside of the nozzle exits. Therefore, as jets of water exit the nozzles, water from downcomer annulus  108  may be drawn into inlet mixer  142  via the secondary inlet openings, where it may be mixed with coolant water from the recirculation pump. The coolant water then may flow into diffuser  148 . 
       FIG. 2  is a schematic diagram showing a developed azimuthal view of the interior of a related BWR core shroud that comprises a plurality of shell sections, having vertical seam welds, that are welded together, one upon the next, by horizontal seam welds. 
     As shown in  FIG. 2 , core shroud  200  may comprise first shell sections  202   a  and  202   b , second shell sections  204   a  and  204   b , third shell sections  206   a  and  206   b , fourth shell sections  208   a  and  208   b , and fifth shell sections  210   a ,  210   b , and  210   c . Core shroud  200  may be supported by shroud supports  212   a ,  212   b , and  212   c , as well as shroud support plate  214 . 
     Shroud supports  212   a ,  212   b , and  212   c  may be joined together using vertical seam welds V 12 , V 13 , and V 14 , and also may be joined using horizontal seam weld H 8  to shroud support plate  214 . 
     Fifth shell sections  210   a ,  210   b , and  210   c  may be joined together using vertical seam welds V 9 , V 10 , and V 11  to form a lower shell section of core shroud  200 , and also may be joined using horizontal seam weld H 7  to shroud supports  212   a ,  212   b , and  212   c.    
     Fourth shell sections  208   a  and  208   b  may be joined together using vertical seam welds V 7  and V 8  to form a bottom mid-core shell section of core shroud  200 , and also may be joined using horizontal seam welds H 6 A and H 6 B to fifth shell sections  210   a ,  210   b , and  210   c . Horizontal seam weld H 6 A may represent the joining of fourth shell sections  208   a  and  208   b  to core plate support ring  216 ; horizontal seam weld H 6 B may represent the joining of core plate support ring  216  to fifth shell sections  210   a ,  210   b , and  210   c.    
     Third shell sections  206   a  and  206   b  may be joined together using vertical seam welds V 5  and V 6  to form a middle mid-core shell section of core shroud  200 , and also may be joined using horizontal seam weld H 5  to fourth shell sections  208   a  and  208   b.    
     Second shell sections  204   a  and  204   b  may be joined together using vertical seam welds V 3  and V 4  to form a top mid-core shell section of core shroud  200 , and also may be joined using horizontal seam weld H 4  to third shell sections  206   a  and  206   b.    
     First shell sections  202   a  and  202   b  may be joined together using vertical seam welds V 1  and V 2  to form an upper shell section of core shroud  200 , and also may be joined using horizontal seam welds H 2  and H 3  to second shell sections  204   a  and  204   b . Horizontal seam weld H 2  may represent the joining of first shell sections  202   a  and  202   b  to top guide support ring  218 ; horizontal seam weld H 3  may represent the joining of top guide support ring  218  to second shell sections  204   a  and  204   b.    
     Horizontal seam weld H 1  may represent the joining of shroud flange  220  to first shell sections  202   a  and  202   b.    
     As known to a PHOSITA, the relative offsets in vertical seam welds V 1 -V 14  attempt to ensure that a crack in a single vertical seam weld cannot propagate over a significant distance (e.g., all the way from horizontal seam weld H 1  to horizontal seam weld H 8 ). However, horizontal seam weld H 1 -H 8  do not have such an offset arrangement. 
     Although SCC, IGSCC, and IASCC have been studied, no “cure” has been found. As a result, cracks continue to initiate and propagate in components of nuclear reactors. Core shrouds may be particularly susceptible due to their extremely high neutron fluence as the nuclear reactor ages. For example, in core shroud  200 , the active fuel in an associated core  102  may extend vertically from between horizontal seam welds H 5  and H 6 A to about horizontal seam weld H 2  or H 3 . Thus, horizontal seam welds H 2 , H 3 , H 4 , and H 5 , and vertical seam welds V 3 , V 4 , V 5 , V 6 , V 7 , and V 8 , all may be described as being subject to extremely high neutron fluence. In the event of SCC, IGSCC, or IASCC of the seam welds, core shroud  200  could be replaced. However, a more economically feasible approach might be to conduct weld repair or to structurally replace the horizontal seam welds, vertical seams welds, or both. 
     Such a weld repair may be done with the seam welds submerged, but this approach may be difficult from a technical point of view. Such a weld repair also may be done with the seam welds not submerged, but this approach may present other issues, such as significant radiation exposure and extension of the critical path during an outage. 
     As known to a PHOSITA, tie-rods have been proposed to structurally replace the horizontal seam welds as a group. Although tie-rods may provide significant support for the horizontal seam welds as a group, such tie-rods may not be as effective in structurally replace individual horizontal seam welds. 
     As also known to a PHOSITA, various devices have been proposed to structurally replace the vertical seam welds. Most of these devices involved full penetration of the structure that includes the vertical seam welds. Although such devices may be employed, full penetration of the structure that includes the vertical seam welds may introduce other problems, such as creating potential leakage paths, complicating installation procedures and reactor safety calculations, and establishing new periodic inspection requirements. 
     Thus, a need exists for apparatuses and methods that may provide the ability to structurally replace individual welds in nuclear reactor components subject to SCC, IGSCC, or IASCC. In the case of core shroud  200 , this may include structurally replacing individual horizontal seam welds, individual vertical seams welds, or both. In particular, a need exists for apparatuses and methods that may provide the ability to structurally replace individual welds in nuclear reactor components subject to SCC, IGSCC, or IASCC without fully penetrating a structure that includes the individual welds. 
     Related art systems, methods, and/or filters for apparatuses and methods for structurally replacing cracked welds are discussed, for example, in U.S. Pat. No. 5,392,322 to Whitling et al. (“the &#39;322 patent”); U.S. Pat. No. 5,521,951 to Charnley et al. (“the &#39;951 patent”); U.S. Pat. No. 5,530,219 to Offer et al. (“the &#39;219 patent”); U.S. Pat. No. 5,538,381 to Erbes (“the &#39;381 patent”); U.S. Pat. No. 5,621,778 to Erbes (“the &#39;778 patent”); U.S. Pat. No. 5,675,619 to Erbes et al. (“the &#39;619 patent”); U.S. Pat. No. 5,712,887 to Thompson et al. (“the &#39;887 patent”); U.S. Pat. No. 5,729,581 to Loock et al. (“Loock”); U.S. Pat. No. 5,737,379 to Erbes (“the &#39;379 patent”); U.S. Pat. No. 5,742,653 to Erbes et al. (“the &#39;653 patent”); U.S. Pat. No. 5,802,129 to Deaver et al. (“the &#39;129 patent”); U.S. Pat. No. 5,803,686 to Erbes et al. (“the &#39;686 patent”); U.S. Pat. No. 5,803,688 to Gleason et al. (“the &#39;688 patent”); U.S. Pat. No. 6,067,338 to Erbes (“the &#39;338 patent”); U.S. Pat. No. 6,138,353 to Weems et al. (“Weems I”); U.S. Pat. No. 6,343,107 B1 to Erbes et al. (“the &#39;107 patent”); U.S. Pat. No. 6,345,927 B1 to Pao et al. (“the &#39;927 patent”); U.S. Pat. No. 6,371,685 B1 to Weems et al. (“Weems II”); U.S. Pat. No. 6,464,424 B1 to Weems et al. (“Weems III”); and U.S. Pat. No. 7,649,970 B2 to Erbes (“the &#39;970 patent”); and in U.S. Patent Publication No. 2003/0234541 A1 to Thompson et al. (“the &#39;541 publication”); U.S. Patent Publication No. 2011/0101177 A1 to Suganuma et al. (“Suganuma I”); and U.S. Patent Publication No. 2012/0087456 A1 to Suganuma et al. (“Suganuma II”). 
     The disclosures of the &#39;107 patent, the &#39;129 patent, the &#39;219 patent, the &#39;322 patent, the &#39;338 patent, the &#39;379 patent, the &#39;381 patent, the &#39;619 patent, the &#39;653 patent, the &#39;686 patent, the &#39;688 patent, the &#39;778 patent, the &#39;887 patent, the &#39;927 patent, the &#39;951 patent, and the &#39;970 patent are incorporated in this application by reference in their entirety. Similarly, the disclosures of the &#39;541 publication are incorporated in this application by reference in its entirety. 
     SUMMARY 
     Example embodiments may provide apparatuses and methods for structurally replacing cracked welds. Example embodiments may provide apparatuses and methods for structurally replacing cracked welds of nuclear plants. 
     In some example embodiments, an apparatus configured to structurally replace a cracked weld in a nuclear plant may comprise: a first body portion that comprises a first gripping portion; a second body portion that comprises a second gripping portion; a wedge portion between the first and second body portions; and/or an adjustment portion. The first body portion may be configured to slidably engage the second body portion. The wedge portion may be configured to exert force on the slidably engaged first and second body portions. The adjustment portion may be configured to increase or decrease the force exerted by the wedge portion on the slidably engaged first and second body portions. When the adjustment portion increases the force exerted by the wedge portion on the slidably engaged first and second body portions, a distance between the first and second gripping portions may decrease. 
     In some example embodiments, the adjustment portion may be further configured to prevent the distance between the first and second gripping portions from increasing. 
     In some example embodiments, the apparatus may further comprise a retaining portion. The retaining portion may be configured to interact with the adjustment portion so as to prevent the distance between the first and second gripping portions from increasing. 
     In some example embodiments, an apparatus configured to structurally replace a cracked weld in a nuclear plant may comprise: a body that comprises a first end, a second end, and a portion between the first and second ends. The first end may comprise a first gripping portion. The second end may comprise a second gripping portion. When the body is in an unflexed state, the first gripping portion and the second gripping portion may be a first distance apart. When the body is in a flexed state, the first gripping portion and the second gripping portion may be a second distance apart. The second distance may be greater than the first distance. 
     In some example embodiments, when the body is in the unflexed state, the body may have a first shape. When the body is in the flexed state, the body has a second shape. The first shape may be more curved than the second shape. 
     In some example embodiments, when the body is in the flexed state, the first gripping portion may be configured to enter a first slot on a first side of the cracked weld in a structure that includes the cracked weld and the second gripping portion may be configured to enter a second slot on a second side of the cracked weld in the structure that includes the cracked weld. When the body is in the unflexed state, the first gripping portion may be configured to grip the first slot on the first side of the cracked weld in the structure that includes the cracked weld and the second gripping portion may be configured to grip the second slot on the second side of the cracked weld in the structure that includes the cracked weld. 
     In some example embodiments, an apparatus configured to structurally replace a cracked weld in a nuclear plant may comprise: a first body portion that comprises a first gripping portion; a second body portion that comprises a second gripping portion; and/or an adjustment portion. The first body portion may be configured to slidably engage the second body portion. The adjustment portion may be configured to exert force on the slidably engaged first and second body portions. The adjustment portion may be further configured to increase or decrease the force exerted on the slidably engaged first and second body portions. When the adjustment portion increases the force exerted on the slidably engaged first and second body portions, a distance between the first and second gripping portions may decrease. 
     In some example embodiments, the adjustment portion may be further configured to prevent the distance between the first and second gripping portions from increasing. 
     In some example embodiments, the apparatus may further comprise a retaining portion. The retaining portion may be configured to interact with the adjustment portion so as to prevent the distance between the first and second gripping portions from increasing. 
     In some example embodiments, a method for structurally replacing a cracked weld in a nuclear plant may comprise: obtaining an apparatus that comprises a first body portion comprising a first gripping portion, a second body portion comprising a second gripping portion, a wedge portion between the first and second body portions, and an adjustment portion, wherein the first body portion is configured to slidably engage the second body portion, wherein the wedge portion is configured to exert a first force on the slidably engaged first and second body portions, wherein the adjustment portion is configured to increase or decrease the first force exerted by the wedge portion on the slidably engaged first and second body portions, and wherein when the adjustment portion increases the first force exerted by the wedge portion on the slidably engaged first and second body portions, a distance between the first and second gripping portions decreases; forming slots on both sides of the cracked weld in a structure that includes the cracked weld, wherein the slots do not fully penetrate the structure; disposing the apparatus near a surface of the structure so that the first gripping portion is in a first slot on a first side of the cracked weld and the second gripping portion is in a second slot on a second side of the cracked weld; and/or using the adjustment portion to increase the first force exerted by the wedge portion on the slidably engaged first and second body portions so as to decrease the distance between the first and second gripping portions until the first gripping portion grips the first slot and the second gripping portion grips the second slot with a second force that structurally replaces the cracked weld. 
     In some example embodiments, the method may not comprise removing material from the cracked weld. 
     In some example embodiments, the method may not comprise removing material from a weld heat-affected zone around the cracked weld. 
     In some example embodiments, the slots may be formed outside of a weld heat-affected zone around the cracked weld. 
     In some example embodiments, a method for structurally replacing a cracked weld in a nuclear plant may comprise: forming slots on both sides of the cracked weld in a structure that includes the cracked weld, wherein the slots do not fully penetrate the structure; disposing a body near a surface of the structure, the body comprising a first end, a second end, and a portion between the first and second ends, wherein the first end comprises a first gripping portion, and wherein the second end comprises a second gripping portion; changing the body from an unflexed state in which the first gripping portion and the second gripping portion are a first distance apart to a flexed state in which the first gripping portion and the second gripping portion are a second distance apart, wherein the second distance is greater than the first distance; moving the body in the flexed state so that the first gripping portion is in a first slot on a first side of the cracked weld and the second gripping portion is in a second slot on a second side of the cracked weld; and/or changing the body from the flexed state to the unflexed state so that the first gripping portion grips the first slot and the second gripping portion grips the second slot with a force that structurally replaces the cracked weld. 
     In some example embodiments, the method may not comprise removing material from the cracked weld. 
     In some example embodiments, the method may not comprise removing material from a weld heat-affected zone around the cracked weld. 
     In some example embodiments, the slots may be formed outside of a weld heat-affected zone around the cracked weld. 
     In some example embodiments, a method for structurally replacing a cracked weld in a nuclear plant may comprise: obtaining an apparatus that comprises a first body portion comprising a first gripping portion, a second body portion comprising a second gripping portion, and an adjustment portion, wherein the first body portion is configured to slidably engage the second body portion, wherein the adjustment portion is configured to exert a first force on the slidably engaged first and second body portions, wherein the adjustment portion is further configured to increase or decrease the first force exerted on the slidably engaged first and second body portions, and wherein when the adjustment portion increases the first force exerted on the slidably engaged first and second body portions, a distance between the first and second gripping portions decreases; forming slots on both sides of the cracked weld in a structure that includes the cracked weld, wherein the slots do not fully penetrate the structure; disposing the apparatus near a surface of the structure so that the first gripping portion is in a first slot on a first side of the cracked weld and the second gripping portion is in a second slot on a second side of the cracked weld; and/or using the adjustment portion to increase the first force exerted on the slidably engaged first and second body portions so as to decrease the distance between the first and second gripping portions until the first gripping portion grips the first slot and the second gripping portion grips the second slot with a second force that structurally replaces the cracked weld. 
     In some example embodiments, the method may not comprise removing material from the cracked weld. 
     In some example embodiments, the method may not comprise removing material from a weld heat-affected zone around the cracked weld. 
     In some example embodiments, the slots may be formed outside of a weld heat-affected zone around the cracked weld. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects and advantages will become more apparent and more readily appreciated from the following detailed description of example embodiments, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a sectional view, with parts cut away, of an RPV in a related art BWR; 
         FIG. 2  is a schematic diagram showing a developed azimuthal view of the interior of a related BWR core shroud that comprises a plurality of shell sections, having vertical seam welds, that are welded together, one upon the next, by horizontal seam welds; 
         FIG. 3A  is a diagram of a core shroud prior to preparation of outer surfaces of the core shroud near a weld according to some example embodiments; 
         FIG. 3B  is a diagram of a core shroud after preparation of outer surfaces of the core shroud near a weld according to some example embodiments; 
         FIG. 3C  is a perspective view of a core shroud, outer surfaces, a weld, and slots according to some example embodiments; 
         FIG. 3D  is a top view of a core shroud, outer surfaces, a weld, and slots according to some example embodiments; 
         FIG. 4A  is a front-side perspective view of an apparatus configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 4B  is a back-side perspective view of an apparatus configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 4C  is a top view of a body in an unflexed state and in a flexed state according to some example embodiments; 
         FIG. 4D  is a front-side perspective view of a tool configured to assist an operator in changing a body from an unflexed state to a flexed state or from the flexed state to the unflexed state according to some example embodiments; 
         FIG. 4E  is a front-side perspective view of a tool mated with an apparatus configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 4F  is a back-side perspective view of a tool mated with an apparatus configured to structurally replace a cracked weld in a nuclear plant, a first gripping portion in a first slot, and a second gripping portion in a second slot according to some example embodiments; 
         FIG. 4G  is a back-side perspective view of an apparatus configured to structurally replace a cracked weld in a nuclear plant, after withdrawal a tool configured to assist an operator in changing a body from an unflexed state to a flexed state or from the flexed state to the unflexed state, according to some example embodiments; 
         FIG. 4H  is a front view of two apparatuses configured to structurally replace a cracked weld in a nuclear plant, at vertical seam weld V 3  or V 4  according to some example embodiments; 
         FIG. 4I  is a front view of three apparatuses configured to structurally replace a cracked weld in a nuclear plant, at vertical seam weld V 5  or V 6  according to some example embodiments; 
         FIG. 5A  is a front-side, exploded, perspective view of an apparatus configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 5B  is an outline view of the apparatus of  FIG. 5A ; 
         FIG. 5C  is a front perspective view of an assembled apparatus configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 5D  is another front perspective view of the assembled apparatus of  FIG. 5C ; 
         FIG. 5E  is a top view of the assembled apparatus of  FIG. 5C ; 
         FIG. 5F  is a back perspective view of the assembled apparatus of  FIG. 5C ; 
         FIG. 5G  is a front perspective outline view of an assembled apparatus configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 5H  is a top view of the assembled apparatus of  FIG. 5G , with a first gripping portion in a first slot and a second gripping portion in a second slot; 
         FIG. 5I  is a cross-sectional view of an assembled apparatus configured to structurally replace a cracked weld in a nuclear plant, taken along a centerline of the apparatus, with a first gripping portion in a first slot and a second gripping portion in a second slot, according to some example embodiments; 
         FIG. 5J  is another cross-sectional view of the assembled apparatus  FIG. 5I  taken along a centerline of the apparatus; 
         FIG. 5K  is a front view of three apparatuses, configured to structurally replace a cracked weld in a nuclear plant, at a vertical seam weld according to some example embodiments; 
         FIG. 5L  is an outline view of the three apparatuses of  FIG. 5K ; 
         FIG. 5M  is a front view of two apparatuses, configured to structurally replace a cracked weld in a nuclear plant, at a vertical seam weld according to some example embodiments; 
         FIG. 5N  is a view looking up at the two apparatuses of  FIG. 5M ; 
         FIG. 5O  is a view looking up at the three apparatuses of  FIG. 5K ; 
         FIG. 6A  is a front-side, exploded, perspective view of an apparatus configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 6B  is an enlarged perspective view of a wedge portion of  FIG. 6A ; 
         FIG. 6C  is an enlarged perspective view of an adjustment portion of  FIG. 6A ; 
         FIG. 6D  is an enlarged perspective view of a retaining portion of  FIG. 6A ; 
         FIG. 6E  is an enlarged perspective view of a second body portion of  FIG. 6A ; 
         FIG. 6F  is an enlarged perspective view of a first body portion of  FIG. 6A ; 
         FIG. 6G  is a front perspective view of an assembled apparatus configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 6H  is a back perspective view of the assembled apparatus of  FIG. 6G ; 
         FIG. 6I  is a front perspective view of the assembled apparatus of  FIG. 6G , with a first gripping portion in a first slot and a second gripping portion in a second slot; 
         FIG. 6J  is a front perspective outline view of the assembled apparatus of  FIG. 6I ; 
         FIG. 6K  is a top view of the assembled apparatus of  FIG. 6I ; 
         FIG. 6L  is a bottom outline view of the assembled apparatus of  FIG. 6I ; 
         FIG. 7  is a flow chart illustrating a first method for structurally replacing a cracked weld in a nuclear plant according to some example embodiments; 
         FIG. 8  is a flow chart illustrating a second method for structurally replacing a cracked weld in a nuclear plant according to some example embodiments; and 
         FIG. 9  is a flow chart illustrating a third method for structurally replacing a cracked weld in a nuclear plant according to some example embodiments. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Example embodiments will now be described more fully with reference to the accompanying drawings. Embodiments, however, may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. 
     It will be understood that when an element is referred to as being “on,” “connected to,” “electrically connected to,” or “coupled to” to another component, it may be directly on, connected to, electrically connected to, or coupled to the other component or intervening components may be present. In contrast, when a component is referred to as being “directly on,” “directly connected to,” “directly electrically connected to,” or “directly coupled to” another component, there are no intervening components present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, and/or section from another element, component, region, layer, and/or section. For example, a first element, component, region, layer, and/or section could be termed a second element, component, region, layer, and/or section without departing from the teachings of example embodiments. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like may be used herein for ease of description to describe the relationship of one component and/or feature to another component and/or feature, or other component(s) and/or feature(s), as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     The term “irradiation relaxation” means stress relaxation of corresponding metals due to exposure to ionizing radiation, particularly neutron fluence in a nuclear plant. 
     The term “structurally replace” means to assume all mechanical loads for which the original load-bearing member was responsible. 
     The term “thermal tightening” means that a first body with a first coefficient of thermal expansion is outside of a second body with a second coefficient of thermal expansion, where the second coefficient of thermal expansion is higher. When the first and second bodies are heated, the second body expands more than the first body, causing the first body to constrain its movement, but from the frame of reference of the second body, the first body has tightened on the second body. 
     The term “weld heat-affected zone” means an area of metal that has had its microstructure and properties altered by welding. 
     Reference will now be made to example embodiments, which are illustrated in the accompanying drawings, wherein like reference numerals may refer to like components throughout. 
       FIG. 3A  is a diagram of core shroud  300  prior to preparation of outer surfaces  302   a  and  302   b  of core shroud  300  near weld  302   c  according to some example embodiments.  FIG. 3B  is a diagram of core shroud  300  after preparation of outer surfaces  302   a  and  302   b  of core shroud  300  near weld  302   c  according to some example embodiments. 
       FIG. 3A  shows jet pump assembly  304 , including inlet riser  306 , riser brace  308 , left-hand transition piece  310 , left-hand secondary inlet openings  312 , and left-hand inlet mixer  314 . The corresponding right-hand transition piece, right-hand secondary inlet openings, and right-hand inlet mixer of jet pump assembly  304  may be removed to facilitate access to outer surfaces  302   a  and  302   b  of core shroud  300  near weld  302   c . Although tie-rods associated with core shroud  300  may be removed to facilitate access to outer surface  302   a  of core shroud  300  near weld  302   c , the apparatuses and methods of the present application may allow the tie-rods to remain in place.  FIG. 3A  also shows jet pump assembly  316 , including inlet riser  318 , riser brace  320 , right-hand transition piece  322 , right-hand secondary inlet openings  324 , and right-hand inlet mixer  326 . The corresponding left-hand transition piece, left-hand secondary inlet openings, and left-hand inlet mixer of jet pump assembly  304  may be removed to facilitate access to outer surfaces  302   a  and  302   b  of core shroud  300  near weld  302   c . Although tie-rods associated with core shroud  300  may be removed to facilitate access to outer surface  302   b  of core shroud  300  near weld  302   c , the apparatuses and methods of the present application may allow the tie-rods to remain in place. 
     Similar to  FIG. 3A ,  FIG. 3B  shows jet pump assembly  304 , including inlet riser  306 , riser brace  308 , left-hand transition piece  310 , left-hand secondary inlet openings  312 , and left-hand inlet mixer  314 . The corresponding right-hand transition piece, right-hand secondary inlet openings, and right-hand inlet mixer of jet pump assembly  304  may be removed to facilitate access to outer surfaces  302   a  and  302   b  of core shroud  300  near weld  302   c . Although tie-rods associated with core shroud  300  may be removed to facilitate access to outer surface  302   a  of core shroud  300  near weld  302   c , the apparatuses and methods of the present application may allow the tie-rods to remain in place. Similar to  FIG. 3A ,  FIG. 3B  also shows jet pump assembly  316 , including inlet riser  318 , riser brace  320 , right-hand transition piece  322 , right-hand secondary inlet openings  324 , and right-hand inlet mixer  326 . The corresponding left-hand transition piece, left-hand secondary inlet openings, and left-hand inlet mixer of jet pump assembly  304  may be removed to facilitate access to outer surfaces  302   a  and  302   b  of core shroud  300  near weld  302   c . Although tie-rods associated with core shroud  300  may be removed to facilitate access to outer surface  302   b  of core shroud  300  near weld  302   c , the apparatuses and methods of the present application may allow the tie-rods to remain in place. 
     In addition,  FIG. 3B  shows an example of preparation work on outer surfaces  302   a  and  302   b  of core shroud  300  near weld  302   c . One or more slots  328  may be formed in outer surface  302   a  of core shroud  300  near weld  302   c . Similarly, one or more slots  330  may be formed in outer surface  302   b  of core shroud  300  near weld  302   c.    
       FIG. 3C  is a perspective view of core shroud  300 , outer surfaces  302   a  and  302   b , weld  302   c , a slot  328 , and a slot  330  according to some example embodiments.  FIG. 3D  is a top view of core shroud  300 , outer surfaces  302   a  and  302   b , weld  302   c , a slot  328 , and a slot  330  according to some example embodiments. 
     As shown in  FIGS. 3C and 3D , one or more slots  328  and one or more slots  330  may not fully penetrate the structure core shroud  300  in order to avoid the potentially negative effects associated with such full penetrations. A thickness of core shroud  300  may be, for example, between about 1.5 inches and about 2.0 inches. A depth of one or more slots  328  and one or more slots  330  may be, for example, up to 90% of the thickness of core shroud  300 . The depth of one or more slots  328  and one or more slots  330  may be, for example, greater than or equal to 50% of the thickness of core shroud  300  and less than or equal to 70% of the thickness of core shroud  300 . 
     One or more slots  328  and one or more slots  330  may be formed using techniques known to a PHOSITA, such as Electrical Discharge Machining (“EDM”). In some example embodiments, performance of the apparatuses and methods of the present application may be improved by improving the quality and precision (e.g., positional accuracy and proper orientation) of such forming techniques. 
     As shown in  FIGS. 3B-3D , each slot  328  may correspond to a slot  330 , and each slot  330  may correspond to a slot  328 . Although not limited to a specific shape, a volume associated with one or more slots  328  may approximate that of a rectangular solid. Similarly, although not confined to a specific shape, a volume associated with one or more slots  330  may approximate that of a rectangular solid. A size of the rectangular solid might be, for example, about 3 inches wide, about 7 inches tall, and about 1 inch deep. Because of scalability, however, one or more of these dimensions could be bigger or smaller than those values. Additionally, as discussed above, one or more slots  328  and one or more slots  330  are not limited to a specific shape. 
     An edge of one or more slots  328  closer to weld  302   c  may be substantially parallel to weld  302   c . Similarly, an edge of one or more slots  330  closer to weld  302   c  may be substantially parallel to weld  302   c.    
     An edge of one or more slots  328  closer to weld  302   c  may be substantially parallel to an edge of one or more slots  330  closer to weld  302   c . One or more slots  328  may be substantially parallel to one or more slots  330 . A distance from weld  302   c  to one or more slots  328  or one or more slots  330  may be, for example, greater than or equal to about 3 inches and less than or equal to about 5 inches. 
     An edge of one or more slots  328  closer to weld  302   c  may be substantially perpendicular to outer surface  302   a . An edge of one or more slots  328  closer to weld  302   c  may be undercut so that at least one portion of one or more slots  328  not at outer surface  302   a  is closer to weld  302   c  than the edge of one or more slots  328  at outer surface  302   a . In some example embodiments, performance of the apparatuses and methods of the present application may be improved by such undercuts. 
     One or more slots  328  may lie at an angle relative to one or more slots  330  (e.g., forming a dovetail relationship). The angle may be, for example, greater than or equal to about 5° and less than or equal to about 20°. The angle may be, for example, about 10°. This angular relationship may result from EDM techniques. This angular relationship also may result, for example, from curvature of outer surfaces  302   a  and  302   b  of core shroud  300  near weld  302   c . Additionally, this angular relationship may result, for example, from a radial orientation of EDM relative to a curved or cylindrical surface. In some example embodiments, performance of the apparatuses and methods of the present application may be improved this angular relationship. 
       FIG. 4A  is a front-side perspective view of apparatus  400  configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments;  FIG. 4B  is a back-side perspective view of apparatus  400  according to some example embodiments. 
     Apparatus  400  may comprise body  402 . Body  402  may be configured to act as a spring clamp. 
     Body  402  may comprise metal. The metal may have a coefficient of thermal expansion that is less than a coefficient of thermal expansion associated with the material of core shroud  300 . Thus, when the nuclear plant is heated up, for example, to normal operating temperature, this difference in coefficients of thermal expansion may result in thermal tightening of body  402  with respect to core shroud  300 . The metal may be, for example, XM-19 stainless steel, a 600-series Inconel (e.g., 600, 617, 625, or 690), a 700-series Inconel (e.g., 718 or X-750), or equivalent. 
     Body  402  may comprise first end  404 , second end  406 , and portion  408  between first end  404  and second end  406 . First end  404  may comprise first gripping portion  410 . Second end  406  may comprise second gripping portion  412 . Portion  408  may comprise section  414  configured to assist an operator in changing body  402  from an unflexed state to a flexed state or from a flexed state to an unflexed state. 
     Body  402  may further comprise access  416  configured to allow a tool (not shown) to engage body  402  in order to assist an operator in changing body  402  from an unflexed state to a flexed state or from a flexed state to an unflexed state. 
       FIG. 4C  is a top view of body  402  in unflexed state  418  and in flexed state  420  according to some example embodiments. When body  402  is in unflexed state  418 , first gripping portion  410  and second gripping portion  412  may be a first distance d 1  apart. When body  402  is in flexed state  420 , first gripping portion  410  and second gripping portion  412  may be a second distance d 2  apart. Second distance d 2  may be greater than first distance d 1 . 
     When body  402  is in unflexed state  418 , body  402  may have a first shape. When body  402  is in flexed state  420 , body  402  may have a second shape. The first shape may be more curved than the second shape. 
     When body  402  is in flexed state  420 , first gripping portion  410  may be configured to enter slot  328  formed in outer surface  302   a  of core shroud  300  near weld  302   c  (e.g., a cracked weld) and second gripping portion  412  may be configured to enter slot  330  formed in outer surface  302   b  of core shroud  300  near weld  302   c . When body  402  is in unflexed state  418 , first gripping portion  410  may be configured to grip slot  328  and second gripping portion  412  may be configured to grip slot  330 , compressing weld  302   c.    
       FIG. 4D  is a front-side perspective view of tool  422  configured to assist an operator in changing body  402  from unflexed state  418  to flexed state  420  or from flexed state  420  to an unflexed state  418  according to some example embodiments;  FIG. 4E  is a front-side perspective view of tool  422  mated with apparatus  400  according to some example embodiments;  FIG. 4F  is a back-side perspective view of tool  422  mated with apparatus  400 , first gripping portion  410  in slot  328 , and second gripping portion  412  in slot  330  according to some example embodiments (in  FIG. 4F , section  414  may or may not be in contact with weld  302   c ); and  FIG. 4G  is a back-side perspective view of apparatus  400 , first gripping portion  410  in slot  328 , and second gripping portion  412  in slot  330 , after withdrawal of tool  422 , according to some example embodiments (in  FIG. 4G , section  414  may or may not be in contact with weld  302   c ). 
     Tool  422  may include main body  424 , actuator  426 , first arm  428 , and second arm  430 . Tool  422  may be configured to mate with apparatus  400  using access  416 . Actuator  426  (e.g., a hydraulic actuator using, for example, demineralized water) may use first arm  428  to engage first end  404  and second arm  430  to engage second end  406 . Application of hydraulic power to actuator  426  may then cause first arm  428  and second arm  430  to change body  402  from unflexed state  418  to flexed state  420 . Pressing of section  414  against core shroud  300  may increase mechanical advantage available in changing body  402  from unflexed state  418  to flexed state  420 . 
     As would be understood by a PHOSITA, tool  422  may be remotely operated by industry-standard equipment (e.g., attached to a handling pole used by an operator from a servicing platform). As also would be understood by a PHOSITA, tool  422  may be hydraulically powered by industry-standard equipment. Additionally, as would be understood by a PHOSITA, tool  422  should not flex apparatus  400  beyond the yield strength of the material of apparatus  400 . 
       FIG. 4H  is a front view of two apparatuses  400 , configured to structurally replace a cracked weld in a nuclear plant, at vertical seam weld V 3  or V 4  according to some example embodiments;  FIG. 4I  is a front view of three apparatuses  400 , configured to structurally replace a cracked weld in a nuclear plant, at vertical seam weld V 5  or V 6  according to some example embodiments. 
     According to some example embodiments, apparatuses  400  may be scalable in size and the amount of force applied. Thus, there may be trade-offs between the size of the apparatuses  400  used and the number of apparatuses  400  used (e.g., fewer bigger apparatuses  400  versus more numerous smaller apparatuses  400 ). As would be understood by a PHOSITA, many factors may play into such a decision, such as length of outage, critical path considerations, physical limitations on access to weld  302   c , etc. 
     According to some example embodiments, apparatuses  400  may be easily installed, removed, replaced, or inspected. According to some example embodiments, apparatuses  400  may be of single-piece construction. 
     According to some example embodiments, apparatuses  400  may be pre-loaded so as to prevent damage due to vibration, taking into consideration factors such as irradiation relaxation and thermal tightening. According to some example embodiments, apparatuses  400  may be pre-loaded to account for hoop stresses, such as normal, upset, and loss of coolant accident (“LOCA”) hoop stresses. According to some example embodiments, apparatuses  400  may be pre-loaded to account for pressure differences across core shroud  300 , such as normal, upset, and LOCA differential pressures. 
       FIG. 5A  is a front-side, exploded, perspective view of apparatus  500  configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments;  FIG. 5B  is an outline view of apparatus  500  of  FIG. 5A . 
     Apparatus  500  may comprise first body portion  502 , second body portion  504 , and adjustment portion  506 . Apparatus  500  may be pre-assembled prior to installation (e.g., on the refueling floor), simplifying that process. Apparatus  500  may be configured to act as a self-aligning clamp. 
     First body portion  502  may comprise first gripping portion  508 . Second body portion  504  may comprise second gripping portion  510 . First body portion  502  may be configured to slidably engage second body portion  504 . 
     Adjustment portion  506  may be configured to exert force on the slidably engaged first body portion  502  and second body portion  504 . Adjustment portion  506  may be further configured to increase or decrease the force exerted on force on the slidably engaged first body portion  502  and second body portion  504 . When adjustment portion  506  increases the force exerted on force on the slidably engaged first body portion  502  and second body portion  504 , a distance between first gripping portion  508  and second gripping portion  510  may decrease, compressing weld  302   c  (assuming that apparatus  500  is in use to structurally replace a cracked weld). 
     First gripping portion  508  may be configured to enter slot  328  formed in outer surface  302   a  of core shroud  300  near weld  302   c  (e.g., a cracked weld) and second gripping portion  510  may be configured to enter slot  330  formed in outer surface  302   b  of core shroud  300  near weld  302   c . When adjustment portion  506  exerts force on the slidably engaged first body portion  502  and second body portion  504 , first gripping portion  508  may be configured to grip slot  328  and second gripping portion  510  may be configured to grip slot  330 , compressing weld  302   c.    
     Adjustment portion  506  may be further configured to prevent the distance between first body portion  502  and second body portion  504  from increasing. Such a retention feature may include, for example, a detent mechanism, locking tab, pin, or ratchet mechanism. 
     Adjustment portion  506  may comprise stud  512  and nut  514 . Stud  512  may comprise first end  516  and second end  518 . First end  516  of stud  512  may be configured to fit into access  520  in first body portion  502 . First end  516  of stud  512  may be further configured to interact with nut  514 . For example, stud  512  may be threaded near first end  516  so as to mate with nut  514 . Tightening nut  514  may draw first end  516  through nut  514 , moving first gripping portion  508  and second gripping portion  510  closer together or, if first gripping portion  508  is already gripping slot  328  and second gripping portion  510  is already gripping slot  330 , compressing weld  302   c.    
     Access  520  may be configured to interact with nut  514  so as to allow the slidable engagement of first body portion  502  and second body portion  504  when first body portion  502  and second body portion  504  are not directly in line with one another. This self-aligning feature may include, for example, a ball and seat arrangement in which access  520  may provide a substantially spherical seat and nut  514  may provide a corresponding substantially spherical ball. This self-aligning feature may reduce dependency on the quality and precision of the forming techniques for one or more slots  328  and one or more slots  330 . 
     Second end  518  of stud  512  may be configured to fit into access  522  in second body portion  504 . When first body portion  502  and second body portion  504  are slidably engaged, second end  518  of stud  512  may interact with access  522  so as to prevent rotation of stud  512  relative to second body portion  504 . 
     Apparatus  500  may further comprise retaining portion  516 . Retaining portion  516  may be configured to interact with nut  514  so as to prevent the distance between first body portion  502  and second body portion  504  from increasing. Such a retention feature may include, for example, a detent mechanism, locking tab, pin, or ratchet mechanism. 
       FIG. 5C  is a front perspective view of assembled apparatus  500  configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments;  FIG. 5D  is another front perspective view of assembled apparatus  500  of  FIG. 5C ;  FIG. 5E  is a top view of assembled apparatus  500  of  FIG. 5C ; and  FIG. 5F  is a back perspective view of assembled apparatus  500  of  FIG. 5C . 
       FIG. 5G  is a front perspective outline view of assembled apparatus  500  configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments; and  FIG. 5H  is a top view of assembled apparatus  500  of  FIG. 5G , with first gripping portion  508  in slot  328  and second gripping portion  510  in slot  330 . 
       FIG. 5I  is a cross-sectional view of assembled apparatus  500  configured to structurally replace a cracked weld in a nuclear plant, taken along a centerline of apparatus  500 , with first gripping portion  508  in slot  328  and second gripping portion  510  in slot  330 , according to some example embodiments; and  FIG. 5J  is another cross-sectional view of assembled apparatus  500  of  FIG. 5I  taken along a centerline of apparatus  500 . 
       FIG. 5K  is a front view of three apparatuses  500 , configured to structurally replace a cracked weld in a nuclear plant, at vertical seam weld V 5  or V 6  according to some example embodiments; and  FIG. 5L  is an outline view of the three apparatuses  500  of  FIG. 5K . A tie-rod  524  is visible in both  FIGS. 5K and 5L . 
       FIG. 5M  is a front view of two apparatuses  500 , configured to structurally replace a cracked weld in a nuclear plant, at vertical seam weld V 3  or V 4  according to some example embodiments;  FIG. 5N  is a view looking up at the two apparatuses  500  of  FIG. 5M ; and  FIG. 5O  is a view looking up at the three apparatuses  500  of  FIG. 5K . 
     As would be understood by a PHOSITA, apparatus  500  may be remotely installed using industry-standard equipment (e.g., attached to a handling pole used by an operator from a servicing platform and tightened using a remotely operated tool). 
     According to some example embodiments, apparatuses  500  may be scalable in size and the amount of force applied. Thus, there may be trade-offs between the size of the apparatuses  500  used and the number of apparatuses  500  used (e.g., fewer bigger apparatuses  500  versus more numerous smaller apparatuses  500 ). As would be understood by a PHOSITA, many factors may play into such a decision, such as length of outage, critical path considerations, physical limitations on access to weld  302   c , etc. 
     According to some example embodiments, apparatuses  500  may be easily installed, removed, replaced, or inspected. According to some example embodiments, apparatuses  500  may have a low profile (e.g., when installed, not protruding from core shroud  300  by more than about 4 inches) so as to improve accessibility to weld  302   c  even if tie-rods associated with core shroud  300  are not removed. 
     According to some example embodiments, apparatuses  500  may be pre-loaded so as to prevent damage due to vibration, taking into consideration factors such as irradiation relaxation and thermal tightening. According to some example embodiments, apparatuses  500  may be pre-loaded to account for hoop stresses, such as normal, upset, and LOCA hoop stresses. According to some example embodiments, apparatuses  500  may be pre-loaded to account for pressure differences across core shroud  300 , such as normal, upset, and LOCA differential pressures. 
       FIG. 6A  is a front-side, exploded, perspective view of apparatus  600  configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments. 
     Apparatus  600  may comprise first body portion  602 , second body portion  604 , wedge portion  606  between first body portion  602  and second body portion  604 , and adjustment portion  608 . Apparatus  600  may be pre-assembled prior to installation (e.g., on the refueling floor), simplifying that process. Apparatus  600  may be configured to act as a wedge clamp. 
     First body portion  602  may comprise first gripping portion  610 . Second body portion  604  may comprise second gripping portion  612 . First body portion  602  may be configured to slidably engage second body portion  604 . 
     Wedge portion  606  may be configured to exert force on the slidably engaged first body portion  602  and second body portion  604 . Adjustment portion  608  may be configured to increase or decrease the force exerted by wedge portion  606  on the slidably engaged first body portion  602  and second body portion  604 . When adjustment portion  608  increases the force exerted by wedge portion  606  on the slidably engaged first body portion  602  and second body portion  604 , a distance between first gripping portion  610  and second gripping portion  612  may decrease, compressing weld  302   c  (assuming that apparatus  600  is in use to structurally replace a cracked weld). 
     Adjustment portion  608  may act near an end of wedge portion  606  (e.g., wedge portion  606  may have a threaded end and adjustment portion  608  may be a nut). Tightening the nut may draw wedge portion  606  through the slidably engaged first body portion  602  and second body portion  604 , moving first gripping portion  610  and second gripping portion  612  closer together or, if first gripping portion  610  is already gripping slot  328  and second gripping portion  612  is already gripping slot  330 , compressing weld  302   c.    
     Adjustment portion  608  may be further configured to prevent the distance between first gripping portion  610  and second gripping portion  612  from increasing. 
     Conveniently, adjustment portion  608  may be oriented vertically so as to simply the process of mating an operating tool to adjustment portion  608  (e.g., the operating tool may be attached to a handling pole used by an operator from a servicing platform above adjustment portion  608 ). 
     Apparatus  600  may further comprise retaining portion  614 . Retaining portion  614  may be configured to interact with adjustment portion  608  so as to prevent the distance between first gripping portion  610  and second gripping portion  612  from increasing. 
       FIG. 6B  is an enlarged perspective view of wedge portion  606  of  FIG. 6A ;  FIG. 6C  is an enlarged perspective view of adjustment portion  608  of  FIG. 6A ;  FIG. 6D  is an enlarged perspective view of retaining portion  614  of  FIG. 6A ;  FIG. 6E  is an enlarged perspective view of second body portion  604  of  FIG. 6A ; and  FIG. 6F  is an enlarged perspective view of first body portion  602  of  FIG. 6A . 
       FIG. 6G  is a front perspective view of assembled apparatus  600  configured to structurally replace a cracked weld in a nuclear plant according to some example embodiments;  FIG. 6H  is a back perspective view of assembled apparatus  600  of  FIG. 6G ;  FIG. 6I  is a front perspective view of assembled apparatus  600  of  FIG. 6G , with first gripping portion  610  in slot  328  and second gripping portion  612  in slot  330 ;  FIG. 6J  is a front perspective outline view of assembled apparatus  600  of  FIG. 6I ;  FIG. 6K  is a top view of assembled apparatus  600  of  FIG. 6I ; and  FIG. 6L  is a bottom outline view of assembled apparatus  600  of  FIG. 6I . 
     According to some example embodiments, apparatuses  600  may be scalable in size and the amount of force applied. Thus, there may be trade-offs between the size of the apparatuses  600  used and the number of apparatuses  600  used (e.g., fewer bigger apparatuses  600  versus more numerous smaller apparatuses  600 ). As would be understood by a PHOSITA, many factors may play into such a decision, such as length of outage, critical path considerations, physical limitations on access to weld  302   c , etc. 
     According to some example embodiments, apparatuses  600  may be easily installed, removed, replaced, or inspected. According to some example embodiments, apparatuses  600  may have a low profile (e.g., when installed, not protruding from core shroud  300  by more than about 4 inches or about 100 millimeters) so as to improve accessibility to weld  302   c  even if tie-rods associated with core shroud  300  are not removed. 
     According to some example embodiments, apparatuses  600  may be pre-loaded so as to prevent damage due to vibration, taking into consideration factors such as irradiation relaxation and thermal tightening. According to some example embodiments, apparatuses  600  may be pre-loaded to account for hoop stresses, such as normal, upset, and LOCA hoop stresses. According to some example embodiments, apparatuses  600  may be pre-loaded to account for pressure differences across core shroud  300 , such as normal, upset, and LOCA differential pressures. 
       FIG. 7  is a flow chart illustrating a method for structurally replacing a cracked weld in a nuclear plant according to some example embodiments. 
     As shown in  FIG. 7 , a method for structurally replacing a cracked weld in a nuclear plant may comprise: obtaining an apparatus that comprises a first body portion comprising a first gripping portion, a second body portion comprising a second gripping portion, a wedge portion between the first and second body portions, and an adjustment portion, wherein the first body portion is configured to slidably engage the second body portion, wherein the wedge portion is configured to exert a first force on the slidably engaged first and second body portions, wherein the adjustment portion is configured to increase or decrease the first force exerted by the wedge portion on the slidably engaged first and second body portions, and wherein when the adjustment portion increases the first force exerted by the wedge portion on the slidably engaged first and second body portions, a distance between the first and second gripping portions decreases (S 700 ); forming slots on both sides of the cracked weld in a structure that includes the cracked weld, wherein the slots do not fully penetrate the structure (S 702 ); disposing the apparatus near a surface of the structure so that the first gripping portion is in a first slot on a first side of the cracked weld and the second gripping portion is in a second slot on a second side of the cracked weld (S 704 ); and using the adjustment portion to increase the first force exerted by the wedge portion on the slidably engaged first and second body portions so as to decrease the distance between the first and second gripping portions until the first gripping portion grips the first slot and the second gripping portion grips the second slot with a second force that structurally replaces the cracked weld (S 706 ). 
       FIG. 8  is a flow chart illustrating a method for structurally replacing a cracked weld in a nuclear plant according to some example embodiments. 
     As shown in  FIG. 8 , a method for structurally replacing a cracked weld in a nuclear plant may comprise: forming slots on both sides of the cracked weld in a structure that includes the cracked weld, wherein the slots do not fully penetrate the structure (S 800 ); disposing a body near a surface of the structure, the body comprising a first end, a second end, and a portion between the first and second ends, wherein the first end comprises a first gripping portion, and wherein the second end comprises a second gripping portion (S 802 ); changing the body from an unflexed state in which the first gripping portion and the second gripping portion are a first distance apart to a flexed state in which the first gripping portion and the second gripping portion are a second distance apart, wherein the second distance is greater than the first distance (S 804 ); moving the body in the flexed state so that the first gripping portion is in a first slot on a first side of the cracked weld and the second gripping portion is in a second slot on a second side of the cracked weld (S 806 ); and changing the body from the flexed state to the unflexed state so that the first gripping portion grips the first slot and the second gripping portion grips the second slot with a force that structurally replaces the cracked weld (S 808 ). 
       FIG. 9  is a flow chart illustrating a method for structurally replacing a cracked weld in a nuclear plant according to some example embodiments. As shown in  FIG. 9 , obtaining an apparatus that comprises a first body portion comprising a first gripping portion, a second body portion comprising a second gripping portion, and an adjustment portion, wherein the first body portion is configured to slidably engage the second body portion, wherein the adjustment portion is configured to exert a first force on the slidably engaged first and second body portions, wherein the adjustment portion is further configured to increase or decrease the first force exerted on the slidably engaged first and second body portions, and wherein when the adjustment portion increases the first force exerted on the slidably engaged first and second body portions, a distance between the first and second gripping portions decreases ( 900 ); forming slots on both sides of the cracked weld in a structure that includes the cracked weld, wherein the slots do not fully penetrate the structure ( 902 ); disposing the apparatus near a surface of the structure so that the first gripping portion is in a first slot on a first side of the cracked weld and the second gripping portion is in a second slot on a second side of the cracked weld ( 904 ); and using the adjustment portion to increase the first force exerted on the slidably engaged first and second body portions so as to decrease the distance between the first and second gripping portions until the first gripping portion grips the first slot and the second gripping portion grips the second slot with a second force that structurally replaces the cracked weld ( 906 ). 
     As would be understood by a PHOSITA, although the apparatuses and methods for structurally replacing cracked welds of the present application have been generally described with reference to core shroud  300 , the apparatuses and methods for structurally replacing cracked welds of the present application are also applicable to other components in a nuclear plant, and to other components not in nuclear plants. 
     While example embodiments have been particularly shown and described, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.