An inspection and cleaning robot developed by Finnish Jyväskylä University of Applied Sciences (JAMK) and Fortum is facilitating work at Fortum’s Loviisa NPP, Fortum said on 25 May. The inspection and cleaning of the Loviisa nuclear plant’s steam generators is carried out every four years manually by workers. The work is performed in a challenging environment and involves occupational safety risks. The relatively high radiation levels inside the steam generators add to the challenge of the work.
In a pressurised water reactor, steam generators transfer thermal energy from the reactor to the turbines. The undisrupted operation of the steam generators is a prerequisite for the power plant to produce the required amount of energy. The steam generator’s pipelines and structures must remain clean and intact to ensure that it functions as designed and that radioactive water does not leak into other systems.
The solution developed by JAMK and Fortum can significantly improve work safety and reduce the amount of work done inside the steam generators and minimise radiation doses received by workers.
“We started the project by mapping the possible alternatives for cleaning and inspecting steam generators. However, none of the existing alternatives were completely suitable for this purpose, so we decided to start collaborating with JAMK on the development of a robot that would be suitable for these tasks,” said Fortum Development Manager Ville Lestinen.
The design, development, and factory tests related to the equipment were performed by JAMK in Jyväskylä. Fortum employees headed the project contributing their expertise on the steam generator cleaning and inspection process. The design work started in 2019, and the equipment was piloted in September 2020 during the annual outage of Loviisa unit 1.
“After many ideas, we ended up developing a robotic raft that carries the equipment needed in the maintenance. The complex structure of the inspection site and the very high safety requirements significantly increased the challenge level of the project,” said Senior Lecturer Jaakko Oksanen, a Project Manager working at JAMK.
During the project, modifications to the structures were made based on the tests performed at the Jyväskylä swimming pool. The goals and requirements set by Fortum were ultimately achieved through numerous material and equipment optimisations. After the tests performed in the swimming pool environment, the raft was piloted at the Loviisa plant.
“Taking images of the upper parts of the steam generator was very successful, and inspecting the condition of the structures also went fine. The raft’s control systems operated as expected, and it was easy to manoeuvre the raft to the desired locations. In the further development phase, the focus will be on optimising the equipment’s shape and improving the ability to bypass the complex structures inside the steam generator,” Lestinen noted.
Overall, the raft pilot was more successful than expected and further development of the robot is already under way to get an improved raft ready for deployment in the next inspections of the power plant’s steam generators in 2022.