Control rod for boiling water reactor and method for manufacturing the same

Abstract

A tie rod having a cruciform cross section is provided with steps for fixing sheaths at tips of cruciform arms of the tie rod; the tips of each of sheaths are fitted onto the steps of the tie rod, each of the sheaths having a U-shaped cross section; and each of the sheaths is fixed to the tie rod by performing a laser welding using a YAG laser beam or a CO 2 laser beam with the sheath being fitted onto the tie rod to achieve a continuous weld of at least a part of the tie rod in a longitudinal direction thereof. An axial center position of the beam is shifted from an end face position of the step of the tie rod at least toward an axis center of the tie rod.

1 - 12 . (canceled)  
   
   
       13 . A control rod for boiling water reactor, comprising: 
 a tie rod having a cruciform cross section;    a handle attached to an axially upper part of the tie rod;    a lower part support member or a velocity limiter attached to an axially lower part of the tie rod; and    sheaths attached to tips of cruciform arms of the tie rod, each of the sheaths having a U-shaped cross section;    wherein    the tie rod is provided with steps for welding the sheaths at the tips of the cruciform arms; and    the tip of each of the sheaths is welded to the tie rod by irradiating a surface of the tie rod with an axial center position of a YAG laser beam or a CO 2  laser beam in position shifted from an end face position of the step of the tie rod toward an axis center of the tie rod.    
   
   
       14 . A control rod for boiling water reactor, comprising: 
 a tie rod having a cruciform cross section;    a handle attached to an axially upper part of the tie rod;    a lower part support member or a velocity limiter attached to an axially lower part of the tie rod; and    sheaths attached to a lower end of the handle;    wherein    the handle is provided with a step for welding the sheaths at the lower end thereof; and    an upper edge of each of the sheaths is welded to the handle by irradiating a surface of the handle with an axial center position of a YAG laser beam or a CO 2  laser beam in position shifted from an end face position of the step of the handle to a side opposite to the sheath.    
   
   
       15 . A control rod for boiling water reactor, comprising: 
 a tie rod having a cruciform cross section;    a handle attached to an axially upper part of the tie rod;    a lower part support member or a velocity limiter attached to an axially lower part of the tie rod; and    sheaths attached to an upper end of the lower part support member or the velocity limiter, each of sheaths having a U-shaped cross section;    wherein    the lower part support member or the velocity limiter is provided with a step for welding the sheaths at the upper end thereof; and    a lower edge of each of the sheaths is welded to the lower part support member or the velocity limiter by irradiating a surface of the lower part support member or the velocity limiter with an axial center position of a YAG laser beam or a CO 2  laser beam in position shifted from an end face position of the step of the lower part support member or the velocity limiter to a side opposite to the sheath.