A method comprising: plugging an open end of a cladding tube of a nuclear fuel rod with an end plug having a main body and a cylindrical bond portion extending from the main body and terminating in a cladding seat with reduced diameter compared with the cylindrical bond portion, the plugging including: clamping the open end of the cladding tube against the cladding seat of the end plug; and while clamping, applying electrical current between the end plug and the open end of the cladding tube, the combination of the clamping and the applied electric current being effective to force the open end of the cladding tube over the cladding seat and to slide over the cylindrical bond portion of the end plug and to generate a resistance weld between a cylindrical bonding surface of the cylindrical bond portion of the end plug and the inside surface of the open end of the cladding tube wherein the plugging further includes: clamping the open end of the cladding tube in a clamshell clamp that prevents the outer diameter of the open end of the cladding tube from expanding during the slide of the open end of the cladding tube over the cylindrical bond portion of the end plug. plugging an open end of a cladding tube of a nuclear fuel rod with an end plug having a main body and a cylindrical bond portion extending from the main body and terminating in a cladding seat with reduced diameter compared with the cylindrical bond portion, the plugging including: clamping the open end of the cladding tube against the cladding seat of the end plug; and while clamping, applying electrical current between the end plug and the open end of the cladding tube, the combination of the clamping and the applied electric current being effective to force the open end of the cladding tube over the cladding seat and to slide over the cylindrical bond portion of the end plug and to generate a resistance weld between a cylindrical bonding surface of the cylindrical bond portion of the end plug and the inside surface of the open end of the cladding tube wherein the plugging further includes: clamping the open end of the cladding tube in a clamshell clamp that prevents the outer diameter of the open end of the cladding tube from expanding during the slide of the open end of the cladding tube over the cylindrical bond portion of the end plug. clamping the open end of the cladding tube against the cladding seat of the end plug; and while clamping, applying electrical current between the end plug and the open end of the cladding tube, the combination of the clamping and the applied electric current being effective to force the open end of the cladding tube over the cladding seat and to slide over the cylindrical bond portion of the end plug and to generate a resistance weld between a cylindrical bonding surface of the cylindrical bond portion of the end plug and the inside surface of the open end of the cladding tube wherein the plugging further includes: clamping the open end of the cladding tube in a clamshell clamp that prevents the outer diameter of the open end of the cladding tube from expanding during the slide of the open end of the cladding tube over the cylindrical bond portion of the end plug.