Vibration suppression device for jet pump and jet pump

Abstract

There is provided a vibration suppressing device for a jet pump which is located in a reactor pressure vessel of a boiling water reactor and provided with an inlet mixer pipe coupled to a riser pipe and a diffuser coupled to the inlet mixer pipe by means of a slip joint. The vibration suppressing device is provided with an extension sleeve disposed on an upper portion of the diffuser of the jet pump and constitutes an extension flow channel on a downstream side of a forward leak flow in a slip clearance formed between an inner peripheral surface of the diffuser and an outer peripheral surface of the inlet mixer pipe, and the extension sleeve has a shape such that the extension flow channel has a region in which a flow channel width thereof is constant over a predetermined or longer length.

What is claimed is: 
     
         1 . A vibration suppressing device for a jet pump which is located in a reactor pressure vessel of a boiling water reactor and provided with an inlet mixer pipe coupled to a riser pipe and a diffuser coupled to the inlet mixer pipe by means of a slip joint, wherein the vibration suppressing device is provided with an extension sleeve disposed on an upper portion of the diffuser of the jet pump and constitutes an extension flow channel on a downstream side of a forward leak flow in a slip clearance formed between an inner peripheral surface of the diffuser and an outer peripheral surface of the inlet mixer pipe, and the extension sleeve has a shape such that the extension flow channel has a region in which a flow channel width thereof is constant over a predetermined or longer length. 
     
     
         2 . The vibration suppressing device for a jet pump according to  claim 1 , wherein the flow channel width of the extension flow channel is more than zero and not more than 2.46 as large as a minimum flow channel width of the slip clearance. 
     
     
         3 . The vibration suppressing device for a jet pump according to  claim 1 , wherein the extension flow channel has a flow channel length of 0.1 or more than a flow channel length of the slip clearance, and an upper end of the extension flow channel is positioned in level below a lower surface of a riser bracket. 
     
     
         4 . The vibration suppressing device for a jet pump according to  claim 1 , wherein the inner peripheral surface of the extension sleeve has an imperfect circular cross sectional shape, and the flow channel width of the extension flow channel varies in a circumferential direction of the outer peripheral surface of the inlet mixer pipe. 
     
     
         5 . The vibration suppressing device for a jet pump according to  claim 4 , wherein the imperfectly circular shape of the inner peripheral surface is an elliptic shape. 
     
     
         6 . The vibration suppressing device for a jet pump according to  claim 1 , wherein the extension sleeve has at least one point of contact with the inlet mixer pipe. 
     
     
         7 . A jet pump that is provided in a reactor pressure vessel of a boiling water reactor, comprising:
 a riser pipe;   an inlet mixer pipe coupled to the riser pipe;   a diffuser coupled to the inlet mixer pipe by a slip joint; and   an extension sleeve that is provided on an upper portion of the diffuser and constitutes an extension flow channel on a downstream side of a forward leak flow in a slip clearance that is formed between an inner peripheral surface of the diffuser and an outer peripheral surface of the inlet mixer pipe, and the extension sleeve has a shape such that the extension flow channel has a region, in which a flow channel width thereof is constant, over a predetermined or longer length.