Method of removing retainer of jet pump and jet pump

Abstract

A retainer provided at lower portion of a pump beam of a jet pump for circulating cooling water to a reactor core or a bolt for fastening the retainer is cut through an underwater-remote control to remove the bolt and the retainer is removed through the underwater-remote control.

1 . A method of removing a jet pump retainer comprising the steps of: 
 cutting the retainer or a bolt for fastening the retainer through an underwater-remote control to remove the bolt and removing the retainer, through an underwater-remote control, disposed to a lower portion of a pump beam of a jet pump provided in a reactor pressure vessel of a boiling water reactor to circulate a cooling water to a reactor core.    
   
   
       2 . The method of removing a jet pump retainer according to  claim 1 , wherein the retainer is removed through the underwater-remote control after cutting the whole or a part of the bolt to remove the bolt through the underwater-remote control.  
   
   
       3 . The method of removing a jet pump retainer according to  claim 2 , wherein the bolt is removed by cutting a welded portion by a remote operation in water and the retainer is then removed through the underwater-remote control.  
   
   
       4 . The method of removing a jet pump retainer according to  claim 1 , wherein the retainer is removed in the reactor pressure vessel.  
   
   
       5 . The method of removing a jet pump retainer according to  claim 1 , wherein an inlet mixer of the jet pump is taken out of the reactor pressure vessel and the retainer is removed in a pool.  
   
   
       6 . The method of removing a jet pump retainer according to  claim 1 , wherein the retainer is removed together with the jet pump beam and a head bolt above the retainer.  
   
   
       7 . A jet pump comprising: 
 a riser;    a diffuser; and    an inlet mixer positioned between the riser and the diffuser and provided in a reactor pressure vessel of a boiling water reactor having a retainer disposed for handling a jet pump beam and a head bolt for connecting the inlet mixer and the riser by fastening as an integral body, the jet pump circulating cooling water to a reactor core,    wherein the retainer provided at a lower portion of the pump beam of the jet pump or a bolt for fastening the retainer is cut through an underwater-remote control to remove the bolt and the retainer is removed through the underwater-remote control.