Patent Number: 
Section: description

Referring now to the drawings, particularly to FIG. 1, there is illustrated a core spray nozzle, generally designated 10, for a nuclear reactor, the vessel wall of which is shown at 12. The core spray nozzle 10 of FIG. 1 illustrates the nozzle after replacement of the thermal sleeve portion previously employed to convey cooling water from the core spray piping external of the vessel through the nozzle safe end 14 and the vessel wall 12 to the core spray piping within the vessel wall. More particularly, the T-box 54 and thermal sleeve 56 as described below with reference to FIG. 2, are replaced by a T-box/thermal sleeve assembly 16 as illustrated in FIG. 1 from within the vessel wall. The replacement assembly is mechanically connected with the nozzle safe end 14 within the nozzle bore 15. As illustrated, the vessel wall 12 includes as part of the core spray nozzle 10 a laterally projecting pipe 18 to which the safe end 14 is welded. The safe end 14 includes a cylindrical pipe or thermal sleeve remnant 20 of the previously extant thermal sleeve in the nozzle 10. Particularly, the T-box/thermal sleeve includes a T-junction or T-connection 22 which, in final assembly, lies adjacent the interior of the vessel wall 12. The T-box includes a pair of lateral passages 24 for connection with piping which extends about the interior of the vessel wall approximately 90xc2x0 in opposite directions from the T-box. The piping, of course, connects the cooling water supplied through the core spray nozzle 10 to interior piping of the core spray system. The T-box 22 necks down to a smaller diameter replacement thermal sleeve 26 terminating at an outer end within the nozzle bore in a counterbore 28. The thermal sleeve 26 includes stepped diameter axially spaced threaded portions 30 and 32 along its interior wall surfaces. The thermal sleeve 26 is sized to receive the end portion of the thermal sleeve remnant 20 in the couterbore 28. A seal 34, preferably a Belleville washer, is disposed between the opposed ends of the replacement thermal sleeve 26 and the thermal sleeve remnant 20 such that the Belleville washer 34 is compressed, rendering portions of the thermal sleeve remnant 20 and the replacement thermal sleeve 26 in compression. To retain the thermal sleeve 26 mechanically coupled to the thermal sleeve remnant 20, a groove 36 (FIGS. 3 and 4) is provided along the interior wall surface of the thermal sleeve remnant 20 spaced back from its end. A collet 38 comprising a cylindrical sleeve having a plurality of fingers 40 adjacent one end and an externally threaded portion 42 adjacent an opposite end is threaded along threads 30 within the replacement thermal sleeve 26. It will be appreciated that with radially directed flanges 44 on the ends of the fingers 40 engaged in groove 36, the T-box/thermal sleeve assembly 16 is maintained mechanically assembled to the thermal sleeve remnant 20. To retain the fingers 40 with the flanges 44 engaged in the groove 36, a retention sleeve 46 externally threaded at one end is received within the collet 38. It will be appreciated by threading the retention sleeve 46 along the interior threads 32 of the replacement thermal sleeve 26, the opposite end of the retention sleeve 46 overlies the fingers 40, preventing the finger flanges 44 from removal within the groove 36. A cover 50 is also secured to the open end of the T-box 22 and a seal washer, preferably a Belleville spring washer 52, is disposed between the cover and the T-box end. The collet 38 is preferably formed of Inconel. Inconel has a linear coefficient of expansion less than that of steel. The thermal sleeve remnant 20 and replacement thermal sleeve 26 are formed of steel. Accordingly, when the system heats up, the collet will not expand as much as the thermal sleeve remnant 20 and the replacement thermal sleeve 26. The Belleville washer 34 is also formed of Inconel. Therefore, at temperature, the Belleville washer 34 is placed under further compression desirably enhancing its sealing capability and providing thermal compliance at temperature by accommodating differences in thermal expansion between component materials. Referring now to FIGS. 2-5, the manner of replacing the extant T-box/thermal sleeve with the T-box/thermal sleeve assembly 16 will now be described. The existing T-box 54 and a portion of the thermal sleeve 56 are first removed as illustrated in FIGS. 2 and 3 from the core spray nozzle by employing conventional underwater electric discharge machining, leaving a remnant end 58 (FIG. 3) of the thermal sleeve. This is accomplished underwater and from within the reactor vessel. The newly cut end portion 58 of the thermal sleeve remnant is then prepared for mating with the replacement T-box/thermal sleeve forging. First, the end of the thermal sleeve remnant 20 is machined flat and perpendicular to the thermal sleeve bore. Additionally, the annular groove 36 is formed by machining along the inside diameter of the thermal sleeve remnant 20 at a specified distance from its end portion 58. As evident, the groove 36 provides the mating connection with the finger flanges 44 of the collet to form the mechanical joint between the thermal sleeve remnant 20 and the replacement T-box/thermal sleeve assembly 16 and which joint is sufficient to withstand axial loading therebetween. Next, the collet 38 is screwthreaded onto the replacement T-box/thermal sleeve assembly. It will be appreciated that the threading action between the collet 38 and the thermal sleeve 26 along threads 30 provides a length adjustability between the collet fingers 40 and the seal interface of the T-box/thermal sleeve end and the thermal sleeve remnant end portion 58. A seal washer, preferably a Belleville spring seal 60, is provided on the end of the replacement thermal sleeve 26 and the entire assembly is inserted from the interior of the vessel wall 12 into the nozzle bore 15 such that the counterbore 28 of the replacement thermal sleeve 26 receives the thermal sleeve remnant end portion 58. The Belleville spring washer 60 lies between the opposing end faces of the thermal sleeve remnant 20 and replacement thermal sleeve 26. Also, as the replacement thermal sleeve 26 is inserted to receive the end portion 58 of the thermal sleeve remnant 20, the flanges 44 of the fingers 40 engage in the groove 36 to mechanically retain the parts in assembly. The Belleville spring washer 60 provides compression loading on portions of each of the thermal sleeve remnant 20 and replacement thermal sleeve 26. To retain the replacement thermal sleeve 26 and thermal sleeve remnant 20 mechanically engaged one with the other, the retention sleeve 46 is inserted through the open end of the T-box and threaded along the threads 32 of the replacement thermal sleeve 26. It will be appreciated that the opposite end of the retention sleeve advances and radially overlies the internal surfaces of the fingers 40 whereby the flanges 44 of the fingers are maintained in the groove 36. The ends of the fingers 40 are tapered to facilitate their axial insertion through the end of the thermal sleeve remnant 20. Thus, the fingers 40 are initially biased radially inwardly for passage along the interior surface of the thermal sleeve remnant 20 and are then resiliently flexed radially outwardly to engage the flanges 44 in the groove 36. The retention sleeve is rotated into position by using a spanner wrench or other suitable tool and is then locked against rotation, for example, by staking to the replacement thermal sleeve 26, to prevent inadvertent rotation and possible removal. The T-box/thermal sleeve replacement assembly 16 is supported within the nozzle bore by three or four equally spaced adjustable wedge blocks 62. Each wedge block 62 comprises a keeper 64, a wedge 66 and a jack screw 68. By suitably adjusting the jack screws driving the wedges, the inserted assembly can be centered vis-a-vis the thermal sleeve remnant 20. Thus, the wedge blocks maintain axial alignment of the assembly with the thermal sleeve and minimize bending stresses of the collet fingers. Also, by using the wedge blocks 62, field measuring or machining is not necessary to ensure proper fit-up in the core spray nozzle 10. Finally, the end cap 50 is threaded onto the open end of the T-box. Another Belleville seal ring 52 is preferably disposed between the cap and the T-box. An anti-rotation feature may be incorporated between the closure end cap 50 and the T-box 22 to prevent loosening of the closure cap 50. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.