COVER STORY | FUEL & FUEL CYCLE
Fuel inspection in hot cell
Studsvik has replaced a 40-year-old periscope for visual inspection of spent nuclear fuel with a fast and flexible camera-based inspection system
STUDSVIK NUCLEAR AIMS TO IMPROVE nuclear reactor performance and reduce risks and costs related to nuclear and radioactive materials. One of Studsvik’s main areas of focus is fuel and materials testing. DVel is one of Studsvik’s partners, delivering custom equipment for the material testing and inspection. Niklas Snis, head of fuel testing at Studsvik Nuclear,
says that his experience in the nuclear industry is that new equipment is often developed within the company to meet its highly specific needs. However, this is changing, and he sees new value in going outside the company or even the industry, to get access to new knowledge and technologies. Companies like DVel, with experience from many different industries, can bring a valuable outside perspective to technical challenges within the nuclear industry. They can suggest innovative ideas and contribute to on- going discussions at Studsvik with a distinctive business perspective.
Importance of continuous improvement Being the only fully commercial lab performing analysis of highly radioactive materials, Studsvik Nuclear has to increase the quality of its services continuously to remain at a highly rated international position. It must develop new measurement methods and analysis techniques and strive to become more efficient. There is also a strategic importance to continuously update older equipment to reduce the risk of down time due to malfunctioning systems. In 2020, Studsvik decided to upgrade and replace parts of the periscope equipment used for visual inspection of nuclear fuel rods and other highly radioactive materials. The equipment is one of its most utilised and is a central piece of equipment in its laboratory. Results from the inspections are vital in documenting the investigated component’s status and they are used to identify what features need to
be studied in more detail, using other techniques. The aim of the upgrade was to increase the capacity and flexibility of the visual inspection system.
Dealing with changing project requirements The inspections are done inside a so-called hot cell, a highly shielded area with thick concrete and lead glass walls. Objects inside the cell are manoeuvred from the outside, using manipulators. With the previous periscope equipment, the inspection of a single fuel rod could take several hours, since the operator had to manually move and inspect the samples. The manual operation also made the inspection results operator-dependent, whereas a modern system could support a highly automated image collection — including improved colour and contrast calibration. The project was initially intended as an upgrade of the old inspection system, but when a mechanical mechanism in the old periscope started to malfunction the project developed to become a complete replacement. To make the measurement system even more flexible, it was also decided that the translation stage should be replaced, enabling a fully automatic inspection of fuel rods. As the precise functionality evolved throughout the
project, with several advanced features added at a late stage, the close cooperation between Studsvik and DVel was of great importance.
Hardware and software features The periscope equipment was replaced by a less complicated optical setup. A camera and a zoom objective are placed inside the wall of the hot cell. A mirror, 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 either
Right (from left to right):
Operator using the old periscope for visual inspection of fuel
The old system, which was used from 1978 to 2021 Disassembly of the old periscope
Final assembly of the periscope with improved optical systems
Installation of upgraded fuel inspection system All photos: Studsvik
18 | January 2022 |
www.neimagazine.com
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