Patent Number: 048184705
Section: description

Referring to FIG. 1, a reactor R is illustrated adjacent a holding pool P. A steam separator S is shown removed from the reactor vessel R and placed within the holding pool. Man M manipulates a shoe S at the end of a long pole 14. Shoe S contains a flat bottom with an upwardly exposed piezoelectric device. As will hereinafter more fully appear, manipulation of pole 14 places the shoe S with the upwardly exposed piezoelectric device at the bottom and immersed end of shroud hold down bolt B. Consequently, an ultrasonic test may be conducted from the bottom immersed radioactive portion of the bolt to and toward the upper end of the bolt in the holding pool P. It will be appreciated that the testing apparatus is flexible; testing of the bolts while the steam separator is in the reactor vessel may as well occur. Referring to FIGS. 2A and 2B, the prior art shroud hold down bolt B can be understood. In pertinent part for the purposes of this application, shroud hold down bolt consists of two elongate members. First, there is an inner tension member 20. Inner tension member 20 is constructed of stainless steel and extends the full length of the bolt. Tension member 20 includes a rectangular lug at the bottom thereof which is roughly rectangular in bottom plan view. (See FIG. 2B.) Lug L at the ends of its rectangular section extends beyond the side edges of the inner tension member 20. The side edges 22, 24 of this rectangular lug engage brackets on the shroud 30 overlying the reactor core. The bolt also includes an outer compression tube or member 26 surrounding tension member 20. Compression member 26 compresses downwardly onto the lower portion of the steam separator at a collar 28. The interaction between the lug L and the collar 28 is easy to understand. Specifically, and when the bolt is tightened lug L moves upwardly to and toward collar 28. Lug L, however, is attached underneath a bracket on the reactor shroud. Collar 28 rides on the lower portion of the steam separator. When the bolt is tightened, the steam separator is pushed down onto the shroud bracket. Consequently, attachment of the steam separator to the shroud occurs. As pertinent to the disclosure herein, collar 28 has a sleeve 40 directly fastened to the collar and extending below the collar to and towards lug L. Sleeve 40 is apertured with a window W. Window W includes a lower notch N. Rod 20 is transpierced with a pin P. Pin P protrudes outwardly from the side of shaft 20 through the window W. It is the action of pin P in moving into and out of notch N which causes lug L to move to and from an unlocked position. Simply stated, a mechanism M effects loosening and tightening of the bolt B utilizing a prior art thread driven apparatus. When mechanism M loosens lug L with respect to collar 28, pin P falls downwardly in window W. This downwardly falling disposition occurs until such time as lug L clears the lower portion of the bracket 30 attached to the shroud of the reactor R. Once lug L has cleared the bracket, rectangular lug L rotates until radial alignment to the steam separator occurs. This rotation of the rectangular lug L into radial alignment also aligns pin P directly over notch N. Further loosening of the bolt continues. This loosening continues until the pin P moves downwardly into and within notch N. Once this occurs, lug L is held in the unlatched position. The importance of such a mechanism can be easily understood. Assuming there are 48 bolts securing a steam separator to a reactor shroud 30, all must be unlatched before any upward removal movement of the steam separator S can occur. If one or two bolts remain secured, the reader will understand the damage to the bolts, steam separator or reactor shroud could well occur in the lifting process. It has been emphasized that sleeve 40 contributes to a latent defect in the rod 20. Specifically. and due to welding and other construction of the rod 20, intergranular stress corrosion cracking has been known to occur underneath sleeve 40. When such cracking occurs, sleeve 40 obscures from view the resultant cracks. Moreover, the pin P co-acting with the window W and the notch N hold and maintain the lug L to the bolt B. Simply stated, even where the bolt B at tension member 20 is cracked through, the defect is latent. It will be understood that lug L is highly radioactive. Referring to FIG. 1, the reader can see that this lug is immediately adjacent the core C of the reactor. Having set forth the problem environment, the solution to the problem can now be set forth with respect to FIGS. 3, 4, and 5. Referring to the perspective view of FIG. 3, shoe S is illustrated. The shoe includes a rectangular block shaped member 50 configured with a rectangular sectioned concavity 52. Just as lug L is rectangular in section (see FIGS. 2A and 2B), cavity 52 within shoe 50 is also rectangular in complementary section. The cavity 52 includes a bottom surface 54. Configured centrally of the bottom surface 54 and upwardly exposed for contact at the bottom of the lug is a piezoelectric device 56. This piezoelectric device is placed within a defined aperture and is suitably connected by wires 58 to instrumentation (not shown). It will be remembered that shoe S is remotely manipulated some 20 feet from the users. Consequently, the shoe is provided on all surfaces adjacent cavity 52 with gathering surfaces G. These gathering surfaces enable the device to conveniently find, slide onto, and fit lug L. Once shoe S is in place over a lug L, a clamp member C at a defined grove 62 mate to tension member 20 immediately overlying rectangular lug L. Clamp member C moves downwardly onto and over shaft 20 at groove 20 until contact with the top of the rectangular lug L occurs. Such downward movement is actuated about shoe shaft 60 by a pneumatic cylinder 70. Such movement traps lug L within the cavity against the piezoelectric device 56. Thereafter, ultrasound testing of the shroud bolt can occur. Referring to FIG. 4, a shoe S is shown adjacent a lug L with a pole 14 manipulating the shoe onto the end of the lug L. Attachment of the pole to the shoe S can be easily understood. The pole 14 includes a shaft 64. Shaft 64 on the pole 14 threads into an L shaped notch on tube 66 filling over pole 14 and attached to shoe S. Consequently, shoe S can be remotely manipulated onto and off of rectangular lug L for the test herein described. Referring to FIG. 5, shoe S is shown clamping lug L onto the piezoeleotric device (hidden from view). Testing of the shroud bolt can occur.