Nuclear Applications

Nuclear Container Weld Joint

Low Plasticity Burnishing (LPB®) can be applied to welded seams in Alloy 22 nuclear repository containers in order to mitigate the surface residual stresses created during the welding process.

Stress corrosion cracking (SCC) is a significant problem in both boiling water and pressurized water reactor systems. Tensile residual stresses developed by manufacturing processes such as machining, fit-up, and welding, combined with a corrosive environment and susceptible material, lead to SCC. Significant cost and man-hours are required forContent monitor and repair of SCC.

Low plasticity burnishing can be used to introduce deep compression (>8 mm) with low levels of cold working providing stable compressive residual stresses in critical areas such as welded joints. In the absence of tensile residual stresses SCC is eliminated. In addition, LPB® also provides a near mirror surface finish that is highly desirable for detecting defects with the various non-destructive methods available.

LPB® tooling can be designed for integration with existing equipment. Systems that already exist for welding of structures or piping can be used to manipulate the LPB® tooling. LPB® tools can be designed to robotically treat remote, complex, and high radiation areas such as the inside diameter of tubing or pipes, eliminating the need for exposing personnel to dangerous radiation.

LPB® is the only surface enhancement system available with closed loop feedback control. Closed loop control allows for real-time monitoring and recording of the tool pressures at each location treated for superior quality control, ensuring that the desired depth of compression is attained. Other surface enhancement processes do not have a viable method of measurement and feedback of the key variables at the surface of the work-piece. LPB® tool pressures are saved to an electronic file that allow for the complete treatment history to be preserved.

LPB® Features

  • Capable of producing deep compression.
  • Produces low cold working and thermally stable compression.
  • Compatible with existing tooling and capable of treating complex geometries.
  • Closed loop treatment for precise control of tool pressure and real time monitoring of process.
 

Nuclear Applications - SCC Susceptibility Diagram
SCC in nuclear cask weld


Nuclear Joint Weld
FEA of INL nuclear cask


LPB of INL Nuclear Cask
LPB of INL nuclear cask