Method of and apparatus for welding an end plug onto a nuclear fuel element

Claim 3

The method of claim 1 wherein the step of deflecting the plasma into the joint includes the steps of providing an elongated plasma deflector having an opening sized to receive the fuel tube with a spacing which functions as a maximum outside diameter gauge on the fuel rod in the vicinity of the joint following the termination of the electric arc, inserting the fuel tube through the opening in the plasma deflector, positioning the plasma deflector on the fuel tube adjacent to but spaced from the joint by a predetermined dimension, and rotating the plasma deflector with the fuel tube during the step of establishing the electric arc between the welding electrode and fuel tube and end plug.

Claim 4

The method of claim 2 wherein the step of providing the plasma deflector includes the step of forming at least the end thereof which is adjacent to but spaced from the joint, of the same metal as the fuel tube.

Claim 5

The method claim 1 wherein the step of deflecting the plasma into the joint includes the steps of providing an elongated, cylindrical plasma deflector having an opening which extends between its axial ends sized to receive the fuel tube, and an outside diameter sized to snugly enter the access opening of the welding chamber with a spacing between the plasma deflector and access opening selected to permit free rotation of the fuel tube and plasma deflector relative to the welding chamber only when the longitudinal axis of the fuel tube is in the desired location for the step of establishing the electric arc, inserting the fuel tube through the opening in the plasma deflector with one end of the plasma deflector being within the welding chamber adjacent to but spaced from the joint by a predetermined dimension, and with the other end extending outside the welding chamber through the access opening, and rotating the plasma deflector with the fuel tube.

Claim 6

The method of claim 4 wherein the step of providing the plasma deflector includes the step of forming at least the end thereof which is adjacent to but spaced from the joint, of the same metal as the fuel tube.

Claim 7

The method of claim 1 including the steps of providing a rotatable stop within the welding chamber, and a rotatable chuck outside of the welding chamber, wherein the step of inserting the fuel tube and end plug into the welding chamber, includes the step of inserting the fuel rod through the chuck, and into the welding chamber, with the end plug resting against the rotatable stop.

Claim 8

The method of claim 6 wherein the step of deflecting the plasma into the joint includes the steps of providing an elongated, cylindrical plasma deflector having an opening which extends between its axial ends sized to receive the fuel tube with a predetermined clearance therebetween, and an outside diameter sized to snugly enter the access opening of the welding chamber, with the spacing between the plasma deflector and access opening being selected to permit free rotation of the fuel tube and plasma deflector only when the axes of the rotatable chuck, rotatable stop, and access opening of the welding chamber are substantially aligned, inserting the fuel tube through the opening in the plasma deflector, with one end of the plasma deflector being within the welding chamber adjacent to but spaced from the joint by a predetermined dimension, and with the other end extending outside the welding chamber through the access opening, and rotating the plasma deflector with the fuel tube.

Claim 9

The method of claim 7 wherein the step of providing the plasma deflector includes the step of selecting the diameter of its opening which receives the fuel tube such that it provides a spacing between the plasma deflector and fuel tube which functions as a maximum outside diameter gauge for the fuel tube in the vicinity of the joint, following the termination of the electric arc.

Claim 10

The method of claim 7 wherein the step of providing the plasma deflector includes the step of forming at least the end thereof which is disposed adjacent to the joint, of the same metal as the fuel tube.

Claim 11

Welding apparatus for welding a metallic end plug into an elongated fuel tube, wherein the joint to be welded is a butt joint between the end of the fuel tube and a shoulder on the end plug, comprising: a welding chamber having an access opening, a welding electrode positioned within said welding chamber in welding relation to the joint to be welded when the fuel tube is inserted into the chamber, an end stop positioned within said welding chamber, means for providing said welding chamber with an inert gas atmosphere, a driven chuck positioned outside the welding chamber adjacent to the access opening, with the axes of the chuck, access opening and end stop being in substantial alignment, said chuck being adapted to receive, grip and rotate the fuel tube, and an elongated, cylindrical plasma deflector having a predetermined outside diameter, first and second ends, and an opening sized to receive a fuel tube with a predetermined clearance between the outside diameter of the fuel tube and inside diameter of the opening in the plasma deflector, said plasma deflector being positioned in the access opening such that one end is inside the welding chamber, adjacent to but spaced from the joint between the fuel tube and end plug, when the fuel tube and end plug are inserted through the chuck and plasma deflector and against the end stop.

Claim 12

Welding apparatus for welding a metallic end plug into an elongated fuel tube, wherein the joint to be welded is a butt joint between the end of the fuel tube and a shoulder on the end plug, comprising: a welding chamber having an access opening, a welding electrode positioned within said welding chamber in welding relation to the joint to be welded when the fuel tube is inserted into the chamber, an end stop positioned within said welding chamber, means for providing said welding chamber with an inert gas atmosphere, a driven chuck positioned outside the welding chamber adjacent to the access opening, with the axes of the chuck, access opening and end stop being in substantial alignment, said chuck being adapted to receive, grip and rotate the fuel tube, and an elongated, cylindrical plasma deflector having a predetermined outside diameter, first and second ends, and an opening sized to receive a fuel tube with a predetermined clearance between the outside diameter of the fuel tube and inside diameter of the opening in the plasma deflector, said plasma deflector being positioned in the access opening such that one end is inside the welding chamber, adjacent to but spaced from the joint between the fuel tube and end plug, when the fuel tube and end plug are inserted through the chuck and plasma deflector and against the end stop.

Claim 13

The welding apparatus of claim 10 wherein the outside diameter of the plasma deflector is selected to allow free rotation of the plasma deflector relative to the welding chamber only when the axes of the chuck, plasma deflector, access opening, and end stop are substantially aligned.

Claim 14

The welding apparatus of claim 10 including means for rotating the plasma deflector when the chuck and fuel rod are rotated.

Claim 15

The welding apparatus of claim 10 wherein the predetermined clearance between the outside diameter of the fuel tube and the inside diameter of the opening in the plasma deflector is selected to function as a maximum diameter gauge for the joint area following welding of the fuel tube to the end plug at the butt joint.

Claim 16

The welding apparatus of claim 10 wherein at least the end of the plasma deflector which is adjacent to but spaced from the joint is formed of the same metal as the fuel tube.

Claim 17

The welding apparatus of claim 10 wherein at least the end of the plasma deflector which is adjacent to but spaced from the joint, is formed of an alloy of zirconium.

Claim 18

The welding apparatus of claim 10 including means for fixing the plasma deflector to the fuel tube after the fuel tube has been disposed through the plasma deflector, to permit the plasma deflector to rotate with the fuel tube when it is rotated by the chuck.

Claim 19

The welding apparatus of claim 10 including means interconnecting the chuck and plasma deflector, for directly rotating the plasma deflector when the chuck is rotated.