Studsvik Nuclear AB operates within the field of nuclear technology to improve reactor performance and reduce risks and costs related to nuclear and radioactive materials. One of Studsvik’s main areas of focus is fuel and material testing, in which they are world leading. DVel is one of Studsvik’s partners, delivering custom equipment needed for the material testing and inspection.
On the picture – Project team from Studsvik
Periscope measurement system
Studsvik needed to upgrade and replace parts of their periscope equipment, to speed up and make measurements more flexible. This measurement system is used for visual inspection of fuel rods which is done inside a hot cell with thick concrete and lead glass walls. The measurement process could take several hours for a single fuel rod, due to how the operator had to manually move and inspect the samples. The manual work also made the quality of the inspection very dependent on the skill and experience of the operator.
Meeting up to changing project requirements
The project started as an upgrade of the old inspection system, but since a mechanical mechanism in the old periscope started to malfunction, the project developed into a complete replacement. Later on it was also decided that the translation stage should be replaced, and that the new system should be able to perform automatic inspection of a fuel rod, to make the measurement system even more flexible. As the precise functionality evolved throughout the project, with several features added at a late stage, the close cooperation between Studsvik and DVel was of great importance.
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Hardware and software features
The software enables the user to measure distances and sizes of defects on the fuel rods. The bulk of the visual inspection can thus be performed outside the hot cell, greatly reducing the bottleneck effect of the in-cell inspection. To achieve this, the mechanical and optical systems are carefully designed.
A camera and a zoom lens are placed inside the wall of the hot cell and a mirror, placed at a 45-degree angle, enables a view of the rod from above. The fuel rod can be rotated and translated along three perpendicular axes, so that every part of the rod can be inspected and photographed. The operator can manually move and take pictures of the rod or choose to perform an automatic inspection. Camera and light settings can be adjusted for best image quality. The images are calibrated to provide the real-life position of each pixel. The images are also stored for later inspection.
Improvements with the new measurement system
The new inspection system not only made operation continue as before, but Studsvik’s measurement capacity is also significantly increased since many of the new system features are automated. One aspect is that the inspection of a fuel segment is much faster than before. For example, a one-meter fuel segment that previously took around four hours to inspect, now only takes 20 minutes. The inspection system can also be operated remotely which improved the ergonomics for the operator. Additionally, both the inspection system and the translation stage can now be serviced without entering the hot cell. Therefore, no shut down of the hot cells are needed during system maintenance.
The new system allows:
- Fast, automatic inspection of the whole rod.
- Automatic measurements of the thickness along the rod.
- Automatic stitching of images along a rod.
- Manual inspection of defects.
- Remote supervision and control.
- Data storage of image information, such as resolution, position and thickness profile.
- Offline inspection of stored images.
On the picture – The inspection system inside the hot cell at Studsvik
Staying ahead of competitors
As an important aspect in making sure that Studsvik is always one step ahead of their competitors, the close collaboration between Studsvik and DVel continues. This enables smart features to be added as new ideas come up. In this way Studsvik can carry on innovating and providing world leading service to their customers.