Risk-Aware Tolerance Stack-up & Assembly Philosophies

Project summary

From aerospace philosophy to nuclear practice.

Large high-value assemblies in safety critical sectors such as aerospace or nuclear must be manufactured to a high quality, in adherence with extensive regulatory requirements, while remaining commercially viable. Automation and robotics are increasingly used, but require careful planning and understanding of the variabilities in component parts.

There is extensive research in "build philosophies" for aerospace, focused on building large structures in a way that prevents tolerance stack-up and results in an accurate, quality product. Can these lessons transfer to nuclear manufacturing, and what aspects of nuclear engineering need to be accommodated?

A key issue in nuclear is that not all features in an assembly are equally safety-significant. The IAEA has a three-level grading process for quality assurance, which this project explores integrating into the approach.

Aims and objectives

Aim: create a new approach for defining assembly philosophies for nuclear assemblies which accommodates feature safety significance, predicts the risk of features being out of tolerance, and produces a robotic process plan with integrated metrology.

Objectives:

• Feature risk grading: can IAEA-style risk grading be implemented at the level of assembly features in design?
• Assembly risk prediction: can we predict that functional requirements of high-risk features could be violated, using tolerance and uncertainty propagation analysis?
• Metrology strategy: what level of metrology and quality assurance is necessary for each level of risk?
• Robotic assembly philosophies and planning: can predicted tolerance and safety risk be integrated into a robotic assembly plan?
• Demonstration and validation: how do we test and validate the build philosophy on a real robotic assembly system with integrated metrology?

Alignment to STAND-UP impact targets