Patent Number: 053295633
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 11 to 28 show details of a first embodiment of the present invention. FIGS. 11 and 12 are side views showing the control rod latch tool 100 according to a first embodiment of the invention disposed in an operative position on a control rod 59. This arrangement comprises a pole adapter 101 which is arranged operatively engages a rigid pole (not shown) which extends down through the reactor vessel. The pole adapter 101 is rotatably supported on a stationary shaft 102 by way of a bearing 104. An actuator disc 106 is threadedly received on a threaded portion 108 of the pole adapter 101. The pole adapter is formed with a radially extending flange 101a at the bottom thereof to limit the downward movement of the actuator disc 106. The actuator disc 106 is formed with two diametrically opposed elongate slots 110 (shown in FIGS. 17, 18 and 19 for example) which are arranged to receive cranks 112 formed at the upper ends of two elongate actuator rods 114. The upper end portions of the cranks 112 are provided with enlarged portions 112a which are larger in diameter than the width of the slots 110. The actuator rods 114 are disposed through tubes 116 which are incorporated into reinforced V-shaped cross-section support structures or arms 118 which are associated with each of the actuator rods 114 and which extend down below the level of the unlatching handle 71. The upper ends of the support structures 118 are rigidly connected to an upper support structure and guide member 120 which is arranged to seat on the upper edge of the lifting handle 66. Sector-shaped actuator members or "cams" 122 are fixed to actuator rods 114 near the bottom thereof. These so called cams 122 are adapted to swing synchronously with the rotation of the actuator rods 114 from the positions shown in FIG. 13 to those shown in FIG. 14 and vice versa. When the actuator cams 122 are rotated inwardly they enter the spaced defined below the unlatching handle 71 to positions wherein they are engageable with the lower edge of the handle. Additionally, in the "engaged" positions, a side edge of each of the cams 122 comes into contact with an inner edge 70a of a control rod blade 70 in a manner which limits further rotation of the cams in the engaging direction. This engagement produces a reaction which prevents the actuator rods from undergoing further rotation and thus also holds the actuator disc 106 against further rotation. Under these conditions, further rotation of the pole adapter causes the actuator disc 106, which is threaded to the outer periphery of the pole adapter 101, to thread its way up along the pole adapter 101 without undergoing any further rotation. Since the tops of the cranks 112 are provided with the enlarged portions 112a, the upward displacement of the actuator disc 106 is such as to draw the actuator rods 114 upwardly. In the present embodiment, the upward displacement which is possible with this arrangement, is selected to be about one inch (1") which is sufficient to lift the unlatching handle 71 sufficiently as to induce the release of the control rod 59 from the control rod drive. In operation, the tool 100 according to the first embodiment of the invention is adapted to be lowered down through the reactor vessel 41 at the end of a rigid pole. The rigid pole is as mentioned above, connected to the tool 100 by way of the pole connector 101. The tool 100 is lowered through an opening 124 in a fuel support piece 126 until it rests on top of a control rod 59. In this position, the tool 100 straddles the control rod 59 diagonally with one actuator rod 114 and associated support arms 118, extending down along each side of the control rod 59. The upper end of the tool 100 is guided into position on top of the control rod 59 by the oppositely arranged support structures 118. When the tool 100 is in position, the operator rotates a rigid pole adapter 101 by way of the non-illustrated rigid pole. This rotation induces the actuator disc 106 to rotate in synchronism therewith. As the actuator disc 106 rotates with the pole adapter 101, the cranks 112 are displaced in a manner shown in FIGS. 16 to 19 and thus crank the actuator rods 114 to rotate through an angle of approximately 180.degree. . The actuator cams 122 which are fixedly secured to the actuator rods 114 near the lower ends of the same, rotate from the positions shown in FIG. 13 to those shown in FIG. 14 wherein they extend into the space defined by the unlatching handle 71. Continued rotation of the rigid pole causes the actuator disc 106, which is held against further rotation in the same direction, to thread its way up along the threaded portion 108 pole adapter 101 and thus draw the actuator rods 116 and cams 122 upwards. This pulls the unlatching handle 71 upwards through the required distance of approximately 1 inch and thus releases the control rod 59 from the associated control rod drive. To release the handle, the tool operator turns the rigid pole in the other rotational direction so that the actuator disc 106 threads its way down along the pole adapter 101 thus lowering the actuator rods 114 and cams 122. When the unlatching handle 71 is lowered to its normal position, the actuator cams 122 become free to swing out from the control rod 59 in the manner depicted in FIGS. 23 to 28. More specifically, the unlatching handle 71 is provided with a return spring which is compressed by the lifting of the handle. This spring produces a bias which forces the lower edge of the unlatching handle 71 down against the tops of the actuator cams 122. This holds the cams 122 stationary while the pole adapter 101 is rotated in the release rotational direction, and thus enables the actuator disc 106 to thread its way down along the pole adapter 101 until the handle 71 is lowered to its normal locking position and before the cams swing out to the position illustrated in FIG. 28. It is important in accordance with the present invention that the engagement and disengagement be performed in a controlled manner. The design of the tool ensures that the cranks move the cams to a disengaged position before the tool is moved away from the control rod 59, and also that the actuator cams are engaged before the lifting movement of the actuator rods begins. The upper ends of the cranks are designed so the operator can easily verify the engage/disengage movements from the refuel floor. SECOND EMBODIMENT A second embodiment of the invention is shown in FIGS. 29 to 32. This embodiment differs from the first in that the tool 200 is modified to function as both a lifting tool as well as an unlatching tool. As will be appreciated from the figures, additional lifting "cams" 228 have been added to the actuator rods 114. These lifting cams 228 are arranged to swing synchronously with the unlatching actuating cams 122 and to enter the space defined by the lifting handle 66. In this embodiment compression springs 230 are additionally provided below the actuating cams 122. The reason for this provision that, after the actuating cams 122 engage the unlatching handle 71, and the upward lift of the handle 71 is completed, it is necessary for the actuating cams 122 to be able slide through a short distance until the load of the control rod 59 is taken by the engagement between the lifting handle 66 and the upper set of lifting cams 228. The compression springs 230 ensures that the unlatching handle 71 is not overloaded as the control rod 59 is lifted by the upper pair of lifting cams 228 rather than the actuating cams 122. In this embodiment the unlatching cams 122 are prevented from rotating about the actuator rods 114 by means of keys or splines 230, which allow the cams 122 to undergo a limited amount of vertical displacement along the actuator rods 114. As will be appreciated from FIG. 32, the lifting cams 228 are arranged to engage one another below the lifting handle 66 at the same time as the unlatching actuating cams 122 reach their appropriate unlatching position below the lower edge of the unlatching handle 71. It will be appreciated that even though only two embodiments have been disclosed and illustrated, various changes and modifications can be made without departing from the scope of the present invention. For example, it is within the scope of the present invention to provide the unlatching actuator cams with a sloped upper surface so that after a predetermined amount of rotation toward the engaged position, the upper surfaces of the cams begin to drive (viz., cam) the unlatching handle upward and thus obviate the need for threaded engagement between the actuator disc and the pole adapter to lifting the unlatching handle. It is further within the scope of the invention to provide a step down gearing between pole adapter and the actuator disc in order to increases the ease with which the pole adapter can be rotated. Further alternatives involve using reverse angled surfaces which would allow the cams to be positively retained under the unlatching handle for lifting. The cams, particularly the upper ones which are used for lifting of the control rod per se, could benefit from such reverse sloped surfaces as this would induce the same to interlock with each other so ensure a higher degree of safety when lifting the control rods out of the reactor vessel. A further alternative which could be envisaged would be to form elongate narrow notches or recesses in the upper surface of the cams, in which the handles could be received to prevent any possible slippage. The various other changes which can be implemented are believed to be self-evident to those skilled in the art to which the present invention pertains, in view of the preceding disclosure.