Patent Number: 050770004
Section: description

DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like, are words of convenience and are not to be construed as limiting terms. PRIOR ART REACTOR COOLANT PUMP Referring now to the drawings, and particularly to FIG. 1, there is shown a schematic representation of one of a plurality of cooling loops 10 of a conventional nuclear reactor coolant system. The cooling loop 10 includes a steam generator 12 and a reactor coolant pump 14 serially connected in a closed coolant flow circuit with a nuclear reactor core 16. The steam generator 12 includes primary tubes 18 communicating with inlet and outlet plenums 20,22 of the generator. The inlet plenum 20 of the steam generator 12 is connected in flow communication with the outlet of the reactor core 16 for receiving hot coolant therefrom along flow path 24 of the closed flow circuit. The outlet plenum 22 of the steam generator 12 is connected in flow communication with an inlet suction side of the reactor coolant pump 14 along flow path 26 of the closed flow circuit. The outlet pressure side of the reactor coolant pump 14 is connected in flow communication with the inlet of the reactor core 16 for feeding cold coolant thereto along flow path 28 of the closed flow circuit. In brief, the coolant pump 14 pumps the coolant under high pressure about the closed flow circuit. Particularly, hot coolant emanating from the reactor core 16 is conducted to the inlet plenum 20 of the steam generator 12 and to the primary tubes 18 in communication therewith. While in the primary tubes 18, the hot coolant flows in heat exchange relationship with cool feedwater supplied to the steam generator 12 via conventional means (not shown). The feedwater is heated and portions thereof changed to steam for use in driving a turbine generator (not shown). The coolant, whose temperature has been reduced by the heat exchange, is then recirculated to the reactor core 16 via the coolant pump 14. The reactor coolant pump 14 must be capable of moving large volumes of reactor coolant at high temperatures and pressures about the closed flow circuit. Although, the temperature of the coolant flowing from the steam generator 12 to the pump 14 after heat exchange has been cooled substantially below the temperature of the coolant flowing to the steam generator 12 from the reactor core 16 before heat exchange, its temperature is still relatively high, being typically about 550 degrees F. The coolant pressure produced by the pump is typically about 2500 psi. As seen in FIGS. 2 and 3, the prior art reactor coolant pump 14 generally includes a pump housing 30 which terminates at one end in a seal housing 32. The pump 14 also includes a pump shaft 34 extending centrally of the housing 30 and being sealingly and rotatably mounted within the seal housing 32. Although not shown, the bottom portion of the pump shaft 34 is connected to an impeller, while a top portion thereof is connected to a high-horsepower, induction-type electric motor. When the motor rotates the shaft 34, the impeller within the interior 36 of the housing 30 circulates the coolant flowing through the pump housing 30 at pressures from ambient to approximately 2500 psi cover gas with minimum pressurized coolant applies an upwardly directed, hydrostatic load upon the shaft 34 since the outer portion of the seal housing 32 is surrounded by the ambient atmosphere. In order that the pump shaft 34 might rotate freely within the seal housing 32 while maintaining the 2500 psi pressure boundary between the housing interior 36 and the outside of the seal housing 32, tandemly-arranged lower primary, middle secondary and upper tertiary sealing assemblies 38,40,42 are provided in the positions illustrated in FIGS. 2 and 3 about the pump shaft 34 and within the pump housing 30 The lower primary sealing assembly 38 which performs most of the pressure sealing (approximately 2250 psi) is of the non-contacting hydrostatic type, whereas the middle secondary and upper tertiary sealing assemblies 40,42 are of the contacting or rubbing mechanical type. Each of the sealing assemblies 38,40,42 of the pump 14 generally includes a respective annular runner 44,46,48 which is mounted to the pump shaft 34 for rotation therewith and a respective annular seal ring 50,52,54 which is stationarily mounted within the seal housing 32. The respective runners 44,46,48 and seal rings 50,52,54 have top and bottom end surfaces 56,58,60 and 62,64,66 which face one another. The facing surfaces 56,62 of the runner 44 and seal ring 50 of the lower primary sealing assembly 38 normally do not contact one another but instead a film of fluid normally flows between them. On the other hand, the facing surfaces 58,64 and 60,66 of the runners and seal rings 46,52 and 48,54 of the middle secondary and upper tertiary sealing assemblies 40 and 42 normally contact or rub against one another. Because the primary sealing assembly 38 normally operates in a film-riding mode, some provision must be made for handling coolant fluid which "leaks off" in the annular space between the seal housing 32 and the shaft 34 rotatably mounted thereto. Accordingly, the seal housing 32 includes a primary leakoff port 68, whereas leakoff ports 70 accommodate coolant fluid leakoff from secondary and tertiary sealing assemblies 40,42. Also, the reactor coolant pump 14 has an annular fluid blocking splash guard 72 disposed adjacent to an annular collar 74 attached to the pump shaft 34. The splash guard 72 is seated within an annular recess 76 formed about an upper portion 78 of the seal housing 32. Screws 80 (only one of which is shown) threaded into holes 82 tapped in the seal housing portion 78 serve to attach the splash guard 72 to the seal housing 32 and retain it in the recess 76 such that an inner periphery 84 of the splash guard 72 is disposed close to the exterior cylindrical surface 86 of the shaft collar 74. RCP AUXILIARY FFLEXIBLE VACUUM BOOT SEAL OF THE PRESENT INVENTION In accordance with principles of the present invention, an auxiliary flexible vacuum seal 88 can be temporarily installed, without the necessity of removing any parts of the pump 14 other than for some piping (not shown), to prepare the reactor coolant pump 14 for reactor coolant system vacuum degasification. Referring now to FIGS. 4 to 15, the auxiliary flexible vacuum seal 88 basically includes a flexible boot member 90, clamping means 92, and upper and lower sealing portions, preferably in the form of ring elements 4,96 (FIG. 8) on the boot member 90. In the alternative, the sealing portions may be the interior surface of the boot member 90 itself at the opposite open end portions thereof since the boot member 90 is stretched when so installed. Also, preferably, the seal 88 includes a boot support member 98. for allowing flexing of the boot member between open and closed side configurations to permit its installation and removal on and from the pump. The flexible boot member 90 of the seal 88 includes a bowl-shaped body 100 (FIGS. 5, 7 and 8). The body 100 has a pair of longitudinally-displaced opposite end portions 100A,100B and defines a hollow cavity 102 (FIG. 10) open at the opposite end portions The body 100 also has a pair of side-by-side longitudinally-extending side portions in the form of flanges 104 defining a split 106 (FIG. 11) in the boot member body 100 along a side thereof. The split 106 extends between the open end portions 100A,100B rendering the body 100 openable at the split 106 for allowing flexing of the boot member 90 between open and closed side configurations to permit its installation and removal on and from the pump housing 30 and shaft 34. The flanges 104 of the boot member 90 project radially outward from and extend longitudinally along opposite sides of the longitudinal split 106 in the body 100. The flanges 104 are disposed in side-by-side contacting relation when the boot member 90 is in its closed configuration as seen in FIGS. 9 and 11 and displaced from one another when the boot member 90 is flexed to its open configuration. The clamping means 92 of the flexible vacuum seal 88 are operable for releasably and sealably clamping together the flanges 104 of the boot member body 100 at the split 106 to retain the boot member 90 in its closed configuration. As seen in FIGS. 8, 9 and 13-15, the clamping means 92 of the flexible seal 88 includes a pair of brackets 108,110 mountable along outer sides of said flanges 104 on the boot member body 100, and a plurality of fasteners 112 extendible through the brackets. The brackets 108,110 have a series of holes 114 therethrough which are alignable with holes 116 through the flanges 104. Also, nuts 118 are attached to the brackets 108,110 at alternating ones of the holes 114 therein. The fasteners 112 are insertable through the aligned holes 114,116 of the brackets 108,110 and flanges 104. Threading the fasteners 112 into the nuts 118 operates to draw the brackets 108,110 toward one another clamping the flanges 104 therebetween. Unthreading the fasteners 112 from the nuts 118 operates to withdraw the brackets 108,110 away from one another for releasing the flanges 104. Further, the upper and lower sealably engaging portions 94,96 (best seen in FIGS. 10 and 12) on the boot member body 100 at the opposite open end portions 100A,100B thereof are rings being semi-circular in cross-section and projecting radially inwardly, however, as mentioned above, these engaging portions 94,96 may be the interior surface of the boot member body 100. Preferably, the rings 94,96 are formed integrally on the interior surface of the body 100 of the boot member 90, extending circumferentially about the interior and projecting radially inwardly therefrom for sealably engaging the pump housing 30 and shaft 34 when the boot member 90 is installed and flexed to its closed configuration, as seen in FIGS. 4 and 5. The boot member 90 and the sealably engaging rings 94,96 on the opposite end portions 100A,100B thereof are composed of resilient stretchable material such as PVC. The body 90 is in a stretched condition when it is installed and clamped to its closed configuration. In such closed configuration, it permits generation of a vacuum seal condition between the boot member 90 and the pump housing 30 and shaft 34. The body 100 has a port 120 conformable to receive the leakoff 70. Finally, the boot support member 98 (best seen in FIGS. 5, 6 and 7) of the flexible seal 88 is disposable within the boot member 90 between it and the pump housing 30 for supporting the boot member 90 when in its closed configuration. As shown in FIGS. 4 and 5, the boot support member 98 is entirely enclosed and covered by the boot member 90 such that the boot support member 98 merely provides an internal supporting structure for the boot member 98 but does not need to provide a sealing type of engagement therewith. More particularly, the boot support member 98 is annular in shape and split at 122 such that the member 98 is composed of a pair of semi-circular parts 124. The support member 98 also has an upper surface 98A conformed in shape to the relatively smooth surface of an intermediate portion 100C (FIG. 11) of the boot member body 100 being located between its opposite end portions 100A,100B for engagably supporting the boot member 90 at its intermediate portion. Further, the boot support member 98 has a lower surface 98B conformed in shape to the relatively interrupted shape of the pump housing 30 for mounting the support member 98 thereon. It is thought that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.