Nuclear reactor refueling methods and apparatuses

Abstract

Refueling of a nuclear reactor ( 40 ) includes removing a fuel assembly ( 10 ). The removal method includes lowering a lifting tool ( 80 ) of a crane ( 44 ) onto a top of the fuel assembly. The lowered lifting tool including a plurality of downwardly extending elements ( 82 ) that surround and vertically overlap a portion ( 74 ) of a control rod assembly ( 70 ) extending above the top of the fuel assembly. The downwardly extending elements are locked with corresponding mating features ( 26 ) at the top of the fuel assembly to connect the lifting tool with the fuel assembly. The connected fuel assembly is moved into a spent fuel pool ( 42 ) using the crane, and the lifting tool is disconnected from the top of the fuel assembly by unlocking the downwardly extending elements from the corresponding mating features at the top of the fuel assembly.

1 . A method comprising:
 performing refueling of a nuclear reactor, the refueling including removing a fuel assembly from a reactor core of the nuclear reactor by a removal method including:
 connecting a lifting tool of a crane with a top of the fuel assembly, the lifting tool comprising an assembly of downwardly extending elements, the connecting including locking lower ends of the downwardly extending elements with respective mating features located at a top and periphery of the fuel assembly; 
 moving the fuel assembly connected with the lifting tool into a spent fuel pool using the crane; and 
 releasing the lifting tool from the top of the fuel assembly, the releasing including unlocking the lower ends of the downwardly extending elements from the respective peripherally located mating features at the top and periphery of the fuel assembly. 
   
     
     
         2 . The method of  claim 1 , wherein the removal method does not include removing a control rod assembly (CRA) that is inserted in the fuel assembly and wherein the CRA vertically overlaps the lifting tool when the fuel assembly is connected with the lifting tool. 
     
     
         3 . The method of  claim 2 , wherein the overlap between the CRA and the lifting tool is at least one-half of the vertical height of the lifting tool. 
     
     
         4 . The method of  claim 2 , wherein the overlap between the CRA and the lifting tool is at least one-half of the vertical height of the downwardly extending elements of the lifting tool. 
     
     
         5 . The method of  claim 4 , wherein the downwardly extending elements comprise downwardly extending vertical rods or bars. 
     
     
         6 . The method of  claim 1 , wherein the removal method does not include removing a control rod assembly (CRA) that is inserted in the fuel assembly and wherein the lower ends of the downwardly extending elements of the lifting tool surround an upper end of the inserted CRA when the fuel assembly is connected with the lifting tool. 
     
     
         7 . The method of  claim 1 , wherein the peripherally located mating features at the top and periphery of the fuel assembly are selected from a group consisting of protrusions, openings, and recesses. 
     
     
         8 . The method of  claim 1 , wherein the locking comprises:
 rotating at least the lower ends of the downwardly extending elements to lock the lower ends disposed over or inside the respective mating features with the respective mating features.   
     
     
         9 . The method of  claim 8 , wherein the lower ends of the downwardly extending elements and the respective mating features define lockable bayonet or J-lock couplings. 
     
     
         10 . A method comprising:
 performing refueling of a nuclear reactor, the refueling including removing a fuel assembly having a control rod assembly (CRA) inserted in the fuel assembly from a reactor core of the nuclear reactor by a removal method including:
 lowering a lifting tool of a crane onto a top of the fuel assembly, the lowered lifting tool including a plurality of downwardly extending elements that surround and vertically overlap a portion of the CRA extending above the top of the fuel assembly; 
 locking the downwardly extending elements of the lowered lifting tool with corresponding mating features at the top of the fuel assembly in order to connect the lifting tool with the fuel assembly; 
 moving the fuel assembly connected with the lifting tool into a spent fuel pool using the crane; and 
 disconnecting the lifting tool from the top of the fuel assembly in the spent fuel pool by unlocking the downwardly extending elements from the corresponding mating features at the top of the fuel assembly. 
   
     
     
         11 . The method of  claim 10 , wherein the downwardly extending elements of the lowered lifting tool vertically overlap the portion of the CRA extending above the top of the fuel assembly by at least one-half of a vertical height of the downwardly extending elements. 
     
     
         12 . The method of  claim 10 , wherein the corresponding mating features at the top of the fuel assembly are selected from a group consisting of protrusions, openings, and recesses. 
     
     
         13 . The method of  claim 10 , wherein the locking comprises:
 rotating at least lower ends of the downwardly extending elements to lock the downwardly extending elements with the corresponding mating features at the top of the fuel assembly.   
     
     
         14 . The method of  claim 10 , wherein the locking comprises engaging bayonet or J-lock couplings between the downwardly extending elements and the corresponding mating features at the top of the fuel assembly. 
     
     
         15 . The method of  claim 10 , wherein the downwardly extending elements do not pivot during the locking. 
     
     
         16 . The method of  claim 10 , wherein the plurality of downwardly extending elements consists of at least three downwardly extending elements. 
     
     
         17 . The method of  claim 10 , wherein the plurality of downwardly extending elements consists of N downwardly extending elements where N is at least four. 
     
     
         18 . An apparatus comprising:
 a lifting tool including:
 an upper end configured for attachment with a crane; and 
 a plurality of downwardly extending elements surrounding an open central region disposed below the upper end, lower ends of the downwardly extending elements being configured to mate with mating features at the top of a nuclear fuel assembly. 
   
     
     
         19 . The apparatus of  claim 18 , further comprising:
 the nuclear fuel assembly including the mating features at the top of the nuclear fuel assembly.   
     
     
         20 . The apparatus of  claim 19 , further comprising:
 a control rod assembly (CRA) inserted in the nuclear fuel assembly with an upper end of the CRA extending out of the top of the nuclear fuel assembly;   wherein the open central region of the lifting tool that is surrounded by the plurality of downwardly extending elements is configured to receive the upper end of the CRA when the lower ends of the downwardly extending elements mate with the mating features at the top of the nuclear fuel assembly.   
     
     
         21 . The apparatus of  claim 20 , wherein the downwardly extending elements of the lifting tool comprise downwardly extending rods or bars. 
     
     
         22 . The apparatus of  claim 21 , wherein the downwardly extending rods or bars are oriented vertically. 
     
     
         23 . The apparatus of  claim 21 , wherein the plurality of downwardly extending rods or bars consists of at least three downwardly extending rods or bars. 
     
     
         24 . The apparatus of  claim 21 , wherein the plurality of downwardly extending rods or bars consists of N downwardly extending rods or bars where N is at least four.