Westinghouse Electric Corporation

Denis Yeo

David A Boatwright

Robert Duncan

Kenneth K Klapper

A method and apparatus of sensing obstructions in a tubular nuclear fuel rod or the like is disclosed. A nozzle is positioned to engage one end of the fuel rod in an air tight sealed relationship. A first gas flows through the nozzle and then into and through the fuel rod. The pressure is sensed and compared with a standardized pressure to determine any excess back pressure in the nozzle indicating an obstruction present therein.

Method and apparatus for sensing obstructions in a nuclear fuel rod

A method of controlling the gas atmosphere in a welding chamber includes detecting the absence of a fuel rod from the welding chamber and, in response thereto, initiating the supplying of a flow of argon gas to the chamber to purge air therefrom. Further, the method includes detecting the entry of a fuel rod in the welding chamber and, in response thereto, terminating the supplying of the flow of argon gas to the chamber and initiating the supplying of a flow of helium gas to the chamber to purge argon gas therefrom and displace the argon gas in the chamber. Also, the method includes detecting the withdrawal of the fuel rod from the welding chamber and, in response thereto, terminating the supplying of the flow of helium gas to the chamber and initiating the supplying of argon to the chamber to purge the air therefrom. The method also includes detecting the initiating of a weld cycle and, in response thereto, momentarily supplying a flow of argon gas to the welding electrode tip for initiating the welding arc.

Method of controlling weld chamber purge and cover gas atmosphere

A method of welding stainless steel, such as a stainless steel end plug into a stainless steel nuclear fuel rod is disclosed. The welding process has a reduced arc wander and deeper arc penetration. A treated welding electrode for practicing the method also is disclosed. A layer of stainless steel is placed on the working arc discharge end of a nonconsumable tungsten arc welding electrode before welding. The stainless steel coating on the electrode reduces arc wander and permits deeper arc penetration. Approximately 0.001 to 0.005 inches of stainless steel is placed on the working arc discharge end of the electrode. The electrode coating can be formed by positioning the working arc discharge end of the electrode into close proximity to a grounded piece of stainless steel and then electrically shorting the electrode to the stainless steel so that the working arc discharge end sticks to the stainless steel. The working arc discharge end of the electrode is broken from the stainless steel so that a layer of stainless steel remains thereon.

Nonconsumable electrode for stainless steel welding and method of welding

A method of forming a gripper cavity in a nuclear fuel rod end plug includes the basic steps of providing an end plug blank having an internal bore of substantially uniform diameter that opens at an annular outer rim on the end plug blank, cold forming the end plug blank to produce an intermediate end plug in which the annular outer rim is transformed into a conical outer rim having a rounded internal surface that defines an inlet opening to the internal bore of a diameter less than that of the internal bore, and removing an external layer of material from the intermediate end plug and an internal layer of material from the rounded internal surface of the conical outer rim to produce a finished end plug having an internal gripper cavity composed of the internal bore and a cylindrical internal surface defining the inlet opening to the internal bore and being of smaller diameter than the internal bore.

Method of forming a gripper cavity in a fuel rod end plug

An apparatus and method produces multi-level heat input for nuclear fuel rod weld formation using a single current level power supply. Different levels of electrical power are produced to achieve a low heat, high heat sequence by imposition of a sequence of inert atmospheric cover gases of different ionization energies at the welding site to regulate voltage drop and thereby electrical power level and heat input level for arc welding of the nuclear fuel rod to take place. A first cover gas, such as argon, is supplied to the weld chamber in a first welding pass for producing a high electrical current level and low heat input level, whereas a second cover gas, such as helium or a mixture of helium and argon, is supplied to the weld chamber in a second welding pass for producing low electrical current level and high heat input level. The first cover gas has a lower ionization energy than the second cover gas which results in a lower voltage drop and lower heat input during the first pass compared to the second pass so that the desired sequence of low heat first pass and high heat second pass is achieved.

Apparatus and method for producing multi-level heat input for weld

A novel weld chamber and process for using such weld chamber are disclosed. A flow of shielding gas through the weld chamber is regulated to provide a constant pressure in the weld chamber while the shielding gas flow sweeps away metal vapors.

Pressurized weld chamber

Apparatus for applying a vacuum to a nuclear fuel rod cladding tube's interior through its open end while girth welding an inserted end plug to its other end. An airtight housing has an orifice with a seal which can hermetically engage the tube's open end. A vacuum hose has one end connected to the housing and the other end connected to a vacuum pump. A mechanized device moves the housing to engage or disengage its seal with the tube's open end. Preferably the mechanized device includes an arm having one end attached to the housing and the other end pivotally attached to a movable table; an arm rotating device to coaxially align the housing's orifice with the welding-positioned tube; and a table moving device to engage the seal of the coaxially aligned orifice with the tube's open end.

Welding nuclear reactor fuel rod end plugs

Apparatus for precisely positioning the seam on an end of a nuclear reactor fuel rod opposite from a welding electrode in a weld chamber. The circumferential seam is formed by abutting surfaces at the end plug-fuel tube interface, and it is important that the seam be located in an exact position relative to the welding electrode tip. This is accomplished by providing a stop member against which the fuel plug rests during the time an end plug is welded. The distances are chosen such that when the end plug is fully seated in the stop member, the electrode tip and seam will be located in optimum positions to effect the making of high quality welds. Open communication is established between the inside of the fuel rod and vacuum equipment which is used for evacuating the fuel rod of air or other gases during the welding operation through an axial passageway in the stop member. When evacuation is complete and the pressure drops to a predetermined low value, a vacuum switch responding to fuel rod pressure acts to close an electrical circuit which energizes the welding electrode. If the end plug is not properly seated in the step member, the desired vacuum cannot be drawn, the vacuum switch will not close, thus precluding initiation of the welding process.

Apparatus for welding an end plug in a nuclear fuel tube

A method and apparatus are disclosed for removing nuclear fuel from a clad fuel element. The fuel element is power driven past laser beams which simultaneously cut the cladding lengthwise into at least two longitudinal pieces. The axially cut lengths of cladding are then separated, causing the nuclear fuel contained therein to drop into a receptacle for later disposition. The cut lengths of cladding comprise nuclear waste which is disposed of in a suitable manner.

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Columbia, SC, United States of America

Denis Yeo