COVER STORY | ROBOTIC WELDING
Seal of approval for nuclear robotic welding
Final packaging of nuclear waste materials requires final welding to seal transport containers. Ensuring this process is safe, secure and of a consistently high quality prompted the development of a new automated mechanised approach
Richard Howells
Innovation Development Director, Jacobs
TO AVOID THE NEED FOR repackaging at the storage location, highly radioactive material must be transported in sealed stainless steel 316L containers, which are usually welded to provide a robust and predictable lifetime seal. For site-to-site transportation, containers are generally housed inside an outer package or flask which is licensed for transport. However, in some cases, these containers are required to be capable of providing an additional layer of containment due to the nature of the material being transported. The same containers are also used for handling on site and are required to resist impacts in case of collisions during transfer. It is therefore important that they can maintain structural integrity, criticality-safe geometry and, ultimately, containment during both normal operations as well as in accident conditions. These containers require a welded closure with sufficient structural capacity to maintain containment even if it is damaged. Producing welds of the required quality during the initial
container fabrication process is relatively straightforward when carried out by sub-contractors with the appropriate levels of quality required. However, the final closure weld – fixing the lid to the container body – must be performed remotely using a mechanised process. This is easier said than done – the problem is how containers packed with
nuclear material can be sealed remotely in a reliable and cost-effective manner that meets the requirements of both transport and long-term storage. It requires significant expertise which is not often readily available. Furthermore, the current range of equipment available for
remote or mechanised stainless-steel welding is generally aimed at fixed diameter welding using large bespoke static equipment that can only be deployed on site if the facility is a new build specifically designed to accommodate it. This limits the application of welding on nuclear sites within existing facilities, and it is also a challenge where there is the need to weld different container diameters and a variety of weld types. To address this challenge Jacobs, the international engineering services company, together with welding specialists Langfields Ltd, part of the Envoy Group, developed TANICS™ – The Automated Nuclear Irradiated Container Solution – an automated, robotic welding solution for the nuclear industry.
Developing TANICS™ Jacobs and Langfields, who have worked together on nuclear container welding for many years, made a joint decision to develop a site-deployable solution which had the flexibility to weld containers with a variety of diameters and weld configurations. Designed with safety and quality assurance as paramount considerations, TANICS™ is a complete package capable of delivering a high integrity butt weld and associated qualification for scalable containers. Automated industrial robots are commonplace, especially in the automotive industry, but they are not suitable for nuclear applications because they mostly perform stitch welds, not the closure welds required on stainless steel radioactive material containers. The welding of the containers will take place inside shielded cells to protect the operators. These cells are built ad-hoc to provide operations staff with shielding from fuel material with a potential dose uptake of up to 30 Sieverts per hour. Although the welding control system contains a substantial number of electronic components which are sensitive to radiation, the welding robot will be located within the cell. It must therefore be protected from excessive radiation dose. This will be achieved in three
Above: The inspection robot using an eddy current system to assess weld quality 26 | February 2023 |
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ways: ● The majority of the equipment, such as control panels, will be located outside the cells with the operations staff
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