Control rod for boiling water reactor, unit for control rod and production method of control rod

Abstract

A control rod for a BWR according to the present invention comprises a first unit composed of a tie rod, a handle mounted on an axially upper portion of the tie rod and a lower support member or falling speed limiter mounted on a axially lower portion of the tie rod; and a second unit composed of a sheath containing therein reactivity control material, an upper end plate mounted on an axially upper portion of the sheath and a lower end plate mounted on an axially lower portion of the sheath, wherein an upper portion of the upper end plate is fixed to the handle, a lower portion of the lower end plate is fixed to the lower support member or falling speed limiter, whereby the control rod is constructed as a joined body of the first unit and the second unit.

What is claimed is:  
     
         1 . A control rod for a BWR comprising: 
 a first unit comprising a tie rod, a handle mounted on an axially upper portion of said tie rod and a lower support member or falling speed limiter mounted on a axially lower portion of said tie rod; and    a second unit comprising a sheath containing therein reactivity control material, an upper end plate mounted on an axially upper portion of said sheath and a lower end plate mounted on an axially lower portion of said sheath,    wherein an upper portion of said upper end plate is fixed to said handle, a lower portion of said lower end plate is fixed to said lower support member or falling speed limiter;    whereby said control rod is constructed as a joined body of said first unit and said second unit.    
     
     
         2 . A control rod for a BWR according to  claim 1 , wherein said sheath is made of an elliptic tube of approximately elliptic cross-section.  
     
     
         3 . A control rod for a BWR according to  claim 1  or  2 , wherein said reactivity control material is made of at least one of an elliptic hafnium tube of approximately elliptic cross-section, a hafnium rod and a neutron absorbing rod containing boron carbide.  
     
     
         4 . A unit for a control rod comprising: 
 a sheath made of an elliptic tube of approximately cruciform cross-section, and containing therein reactivity control material;    an upper end plate mounted on an axially upper portion of said sheath, and    a lower end plate mounted on an axially lower portion of said sheath.    
     
     
         5 . A production process of a control rod for BWR comprising the steps of: 
 mounting a handle on an axially upper portion of a tie rod, and a lower support member or falling speed limiter on an axially lower portion of the tie rod, thereby to form a first unit;    mounting an upper end plate on an axially upper portion of a sheath containing therein reactivity control material, and a lower end plate on an axially lower portion of the sheath, and then    fixing an upper portion of said upper end plate to said handle, and a lower portion of said lower end plate to said lower support member or falling speed limiter, thereby to join said first unit and said second unit.