Patent Number: 
Section: claims

1. A system for separating and coupling a top nozzle having a flow channel plate with guide holes and a fixing hole formed thereto, from/to a nuclear fuel assembly with guide thimbles, the system comprising:a lock insert configured to couple the guide thimbles of the nuclear fuel assembly to the flow channel plate of the top nozzle by being inserted into the guide holes provided in the flow channel plate of the top nozzle; anda separation part configured to separate the lock insert from the flow channel plate of the top nozzle,wherein the lock insert comprises a body in a hollow shape, and an insertion part provided on a top of the body and configured to be inserted into the guide holes,the insertion part comprising:a first latching member having a step, being fixed by being brought into contact with a latching step; anda second latching member having a projection, being fixed by being brought into contact with a latching groove,the insertion part being provided with at least one slot at a predetermined interval along a circumference of the insertion part to make the size of the circumference variable,the guide holes comprising:the latching step provided at an upper portion of an inner circumferential surface of the guide holes and configured to fix the lock insert; andthe latching groove provided at a predetermined portion of the inner circumferential surface of the guide holes and configured to fix the lock insert,wherein engagement of the first and second latching members with the latching step and latching groove alone locks the nuclear fuel assembly to the top nozzle,wherein the separation part comprises a separation member configured to release the coupling of the lock insert and the flow channel plate, and a fixing member configured to be engaged with a bottom surface of the flow channel plate through the fixing hole of the flow channel plate, wherein as the separation part is lowered, the coupling of the lock insert and the flow channel plate is released by the separation member and the fixing member is engaged with the bottom surface of the flow channel plate at the same time; and then as the separation part is lifted, the lock insert remains released from the flow channel plate and the flow channel plate of the top nozzle is lifted in engagement with the fixing member at the same time,wherein the separation member has a predetermined accommodation space formed therein to accommodate one side of the insertion part of the lock insert, and when the one side of the insertion part of the lock insert is inserted into the predetermined accommodation space, a surface of the separation member defining the accommodation space applies a force to the one side of the insertion part, thereby the size of the circumference of the insertion part is reducibly variable by the force and then the coupling between the lock insert and the flow channel plate is released, andwherein one end of the fixing member is provided with a fixing latching member having a step to be engaged with the bottom surface of the flow channel plate, thereby the flow channel plate of the top nozzle is lifted as the separation part is lifted.