Orbital pipe and tube welding has been used in the nuclear power generation industry since the very first commercial plants were built. Fabricators and contractors demand the consistent code-quality welds and the ability to ensure that welds are made precisely within the parameters defined by the WPS/PQR. With every weld undergoing testing, the disruption to schedules for repairs and cut-outs is unacceptable. Automated orbital welding eliminates the variability of manual welding. Heat input, an important parameter for many nuclear pipe welding applications, can be precisely controlled and monitored; which is difficult to accomplish with manual welding.
Magnatech has provided both standard and modified equipment equipped with video arc monitoring for nuclear maintenance applications
The higher duty cycle of automated orbital pipe welding reduces construction time, and allows contractors to meet the tight deadlines for work required during plant shutdowns. Our tube welding systems are used by nuclear welding contractors for small diameter instrumentation line installation.
Nuclear power remains a key element of electrical power supply, providing baseload capability and producing energy at a constant rate. Magnatech orbital welding systems are in routine use throughout the world by the specialized fabricators and contractors who service the nuclear power industry. We are known for our equipment reliability and ease of operation.
Two nuclear power plants, Atucha 1 and 2, were to be built near Buenos Aires, Argentina. Atucha 1 was completed and has long been producing electricity. Although construction began on Unit 2 in 1981, the Siemens design Pressurized Heavy Water Reactor (PHWR) was only 80% completed when construction was halted. In 2006, it was decided to complete construction. However, many of the skilled manual welders that had welded critical piping during initial construction were retired, and adequate skilled welders were unavailable.
Two of the main contractors, Techint and Electroingeneria Argentina, purchased a range of pipe welding systems to compensate for the lack of skilled welders, and achieved the requisite weld quality standards. They completed pipe welding and Unit 2 was put in service in 2012.
The Canadian design CANDU nuclear power plants require the welding of special fittings on 760 feeder pipes (2 - 3" pipe, Sch 80) which carry the primary coolant to the steam generators: each feeder tube is precisely formed to fit in a precise 3 dimensional location. These attach to each fuel channel with a Grayloc fitting. BWX Technologies, Canada manufactured the original and now replacement feeder pipes. It was found that the inconsistent heat input of manual welding of the fittings to the precisely bent pipes, caused distortion, resulting in out of tolerance geometries.
BWTX uses several Pipemaster and D-Head systems. The precise control of weld parameters allows heat input to be minimized. Distortion is controlled within acceptable limits necessary for the pipes to fit in the design locations. As many of the feeder pipes require bends immediately adjacent to the weld, it is necessary to mount the D weld Head on the fitting, with the torch reaching down to the weld OD.
When fuel rods in a nuclear reactor are “spent,” or no longer usable, they are removed from the reactor core and replaced with fresh fuel rods. The spent fuel rods are still highly radioactive and continue to generate significant heat for decades. The fuel assemblies are moved to water pools to cool. They are kept on racks in the pool, submerged in water which is continuously circulated to maintain a safe temperature. The internal surface of the concrete structure of the pool must be completely covered with a 6mm stainless steel liner. Stainless steel strips are fastened to the concrete, and large sheets of steel must be welded to the strips requiring three passes (GTAW). Both horizontal and vertical seam welding must be done.
Magnatech LLC supplied three T-Head systems with Fix-Track, which uses a vacuum track attachment. Multiple sections of track were aligned with the joint. An entire seam was welded, only stopping between passes. The work was performed by China Nuclear Industry Huaxing Construction Company Ltd. Complete radiographic inspection of all joints was specified.
The DOE Savannah River Site, Aiken, SC must create long-term storage solutions for liquid nuclear waste. The site, originally constructed in the 1950s, had produced the materials required to fabricate nuclear weapons. Presently 31 million US liquid gallons (117 million liters) of radioactive salt solutions are stored in large tanks. The Salt Waste Processing Facility (SWPF) is designed to initially process waste liquids for final permanent dry storage. After processing, waste is sent to the Saltstone Processing Facility, where it will be mixed with cement and poured into concrete vaults for safe storage. The SWPF requires thousands of welds on pipes that are 1 to 14 inches (25 to 356 millimeters) in diameter. There is a lack of adequate skilled welders in the local area to meet this requirement.
A significant contractor was awarded the construction project. Realizing the skill shortage, they looked to automation to allow lesser skilled welders to make critical welds requiring 100 percent radiographic inspection. They purchased multiple Pipemaster 515 Power Source units, with an array of different model heads. Each of these weld heads is suited to specific types of welds and different space constraints. D-Heads, Quickclamp Heads, and Redheads were used. The facility was completed eight months ahead of schedule and more than $65 million under the target cost of the contract.