Patent Number: 054815762
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ice condensers for pressurized water nuclear reactors and to methods of maintaining the ice in such ice condensers. More specifically, the invention relates to a vibrating assembly for vibrating the ice baskets of an ice condenser of a pressurized water reactor, and to a method of maintaining the ice in the ice baskets using such a vibrating assembly. 2. Related Art There are two types of nuclear reactors generally used in the United States, the boiling water reactor and the pressurized water reactor. In commercial nuclear plants, the reactor is housed in a building called a containment structure. In a catastrophic accident in which one of the pipes attached to the reactor breaks, the contents of the pipe are released into the containment structure. In boiling water reactors, steam released in the event of a catastrophic accident fills the containment structure and then is forced into a pool of water, so as to suppress the steam and reduce the pressure in the containment structure. In pressurized water reactors, the reactor is housed in a large "dry" containment structure. The size and strength of the containment holds the steam in the event of an accident. However, in one version of a pressurized water reactor, a suppression system is included to condense steam released during an accident. This suppression system is known as an ice condenser, and was developed by Westinghouse Electric Corporation. An early example of such a suppression system is the subject of U.S. Pat. No. 3,580,806 to Weems et al and assigned to Westinghouse. In the ice condenser suppression system, fragmented ice is maintained in baskets located in the containment structure. In the event of an accident, the steam released from a broken pipe is channeled into the ice baskets to reduce the pressure in the containment and prevent the release of radioactive steam outside the containment. Due to melting and sublimation, voids tend to form in the body of fragmented ice, and pieces of fragmented ice may become fused together. In order to minimize these problems, Weems et al propose a system for reducing the thermal gradients, and in turn the convection currents to which the ice fragments are exposed. However, even with such a system, melting and sublimation cannot be eliminated. Consequently, the prior art has developed a number of systems for maintaining the bodies of fragmented ice. U.S. Pat. Nos. 3,850,002; 4,659,068; 4,671,920; 4,711,755; and 4,723,611 are illustrative of such systems. These systems tend to be mechanically complicated, and to be directed to recharging or replenishing the supply of ice, rather that maintaining the ice in optimum condition so as to delay the need for recharging. It is to the solution of these and other problems to which the present invention is directed. SUMMARY OF THE INVENTION It is therefore a primary object of the invention to provide a system for freeing the ice in the ice baskets of an ice condenser suppression system, thereby maintaining the ice in optimum condition and making it more effective. It is another object of the invention to provide a method for maintaining the ice in the ice baskets of an ice condenser suppression system which employs vibration to free the ice in the ice baskets. These and other objects of the invention are achieved by providing a vibrating assembly for vibrating an ice basket of a pressurized water reactor which comprises first and second vibrators and a bracket operatively connected to the vibrators. The bracket includes a horizontally extending first armature portion and a horizontally extending second armature portion pivotably attached at its center to the bottom center of the second armature portion. The first armature portion has first and second clamps extending downwardly from its first and second ends, respectively, while the second armature portion has third and fourth clamps extending downwardly from its first and second ends, respectively. Each of the clamps includes a groove extending vertically upwardly from its bottom surface. The bracket further includes an attachment portion extending vertically upwardly from the first armature portion, the vibrators being attached to the sides of the attachment portion. In one aspect of the invention, the attachment portion is unitarily formed in a single, generally T-shaped piece with the first armature portion. Further, the bracket is smoothly rounded where the attachment portion joins the first armature portion, thereby distributing concentrated forces due to vibrations where the bracket and the first armature portion join. In another aspect of the invention, the third and fourth clamps are pivotably connected to the first and second ends, respectively, of the second armature portion; and are also laterally adjustable with respect to the first and second ends of the second armature portion towards and away from the middle of the second armature portion. In still another aspect of the invention, the grooves formed in the clamps are arcuate, having a radius matching the curvature of the rim or top ring of the ice basket. In the method in accordance with the invention, the vibrator assembly is attached to the rim or top ring of the ice basket by adjusting the positions of the third and fourth clamps to fit the rim and then securing the rim in the first, second, third, and fourth clamps. The vibrators are then activated to free the ice in the ice basket. While the vibrators are activated, the ice basket is pulled from above by exerting an upward force on the bracket and is pushed from below to exert a combination of tension and compression on the ice basket.