In this 3rd in a series of 6 news items looking at the unique contribution NNL makes to the ongoing operation of the HALES plant at Sellafield. This article examines the coil inspection device which provided a view inside the coils for the first time.
National Nuclear Laboratory developed the first coil inspection device during 2006. Following extensive trials at the Workington Laboratory , the device was deployed on plant. The inspections successfully provided coil thickness information and the built-in camera provided useful images.
Access to the bottom coils of one of the evaporators meant negotiating a tighter bend than the coil inspection device was able to navigate. A modified, more flexible device was built based on the idea of articulation. Following trials, it was successfully deployed on plant. In total, some 13 coils across three evaporators were examined.
Base Jacket Inspection
Another modified inspection device was developed to enable inspection of the base jacket of the evaporators. This is a more challenging inspection and therefore a flexible camera was required to make an initial inspection prior to a full scale deployment.
Once again, NNL was able to take an innovative approach and has developed a camera which can be deployed into the inlet of the jacket to determine the exact structure insidethe jacket, providing valuable information for a more detailed inspection. This ‘annulus device’ has been tested and can be deployed on plant in future.
The final areas requiring inspection were the RT lines (metal pipes containing thermocouples which protrude into vessels). NNL was able to utilise its experience in examining RT lines across the Sellafield site to deploy existing equipment and techniques down several RT lines in the evaporators and measure the thickness of the lines. Our ability to utilise tried and tested techniques reduced potential time to deployment for Sellafield Ltd.
National Nuclear Laboratory developed an evaporator coil mock-up to allow non-radioactive testing and demonstration to customers and regulators.
Next time: Thermal and Structural Assessments