Highly radioactive material is transported in sealed stainless-steel containers which are usually welded to ensure a robust and predictable lifetime seal that maintains structural integrity, criticality-safe geometry and, ultimately, containment during normal operations and in accident conditions.
It’s relatively straightforward to weld and inspect to the required quality during the initial container fabrication process but it’s a different matter when the containers are filled with nuclear material. Because of the radiation hazard, the final closure weld – fixing the lid to the container body – must be performed remotely using a mechanised process.
Until recently, the range of equipment available to the nuclear industry for remote or mechanised stainless-steel welding was generally fixed diameter using large bespoke static equipment that can only be deployed on site in a new build facility specifically designed to accommodate it.
This places severe limitations on welding at nuclear sites generally and also where there is a need to weld different container diameters with a variety of weld types.
To address this challenge Amentum, the global leader in advanced engineering and innovative technology solutions and Langfields Ltd, UK-based welding and fabrication specialists, developed TANICS™, a high quality, repeatable and reliable automated welding and inspection solution service, which is also applicable to many industrial users in the UK and internationally.
Amentum and Langfields saw the need for a highly flexible, automated, site-deployable, robotic welding solution – a complete package which could handle a variety of diameters and weld configurations, delivering a high integrity butt weld and associated qualification for scalable containers.
On nuclear sites and in other challenging and hazardous environments, safety is a paramount consideration, so welding of the containers takes place inside specially created, shielded cells to protect the operators from fuel material with a potentially lethal dose uptake.
The welding robot, located within the cell, is protected from excessive radiation dose because:
§ Most of the equipment, such as control panels, is located outside the cells with the operations team;
§ Robots are kept behind shielding until they are required to weld;
§ The container is shielded as much as possible during welding operations, with only the areas to be welded left unshielded.
The weld inspection robot is fitted with cameras and an eddy current array system so operators can see footage and record inspection data of the entire weld from different angles to verify the weld remotely.
TANICS can weld a variety of container diameters and can perform full and partial penetration butt welds in addition to fillet welds in both vertical and horizontal orientations. This flexibility is an advantage over existing mechanised welding systems, which are fixed diameter machines capable of a single weld geometry
Currently there are no other systems capable of being deployed on client sites to do this work in a environments where human access is impossible or extremely hazardous.
“We took TANICS on tour to Sellafield and Dounreay and we were overwhelmed by the interest shown by site licence operators and suppliers. It’s a real game changer for a very technically demanding aspect of radioactive waste management,” said Amentum Engineering Development Director Duncan Steel.
“The welds produced using TANICS were independently qualified in the UK and Germany and have now been endorsed by specialists from Sellafield Ltd. This shows that the system has the potential to set a new benchmark for automated welding in the nuclear industry,” said Langfields Projects Director Wayne Griffiths.
The system has been endorsed by the welding subject matter expert at Sellafield Ltd and is capable of being deployed to any site to seal nuclear containers reliably to high acceptance criteria, both for transport and 100-year storage requirements.
As the nuclear industry increasingly needs to move and store nuclear fuel material using bespoke containers, TANICS™ offers a number of benefits over existing solutions, including its repeatability, flexibility and efficiency, and it is suitable for transport and long-term storage.
Equally importantly, it is a safe, effective and efficient means of achieving the required quality of weld and avoids putting operators in harm’s way.
David Campbell, Technical Manager for Sellafield Ltd, described TANICS as “an exciting development where a high integrity welding process can be deployed remotely and adapted to suit a variety of container sealing activities and could almost be classed as off-the-shelf”.
TANICS™ is qualified in accordance with the European harmonised codes (BS EN ISO 15614-1) and has been dual coded with American Society of Mechanical Engineers (ASME) IX, by an independent UK third-party body. The qualification process used the acceptance criteria PD5500 Cat 1 and Sellafield Build Level 1.
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