Methodology for quantifying uncertainties in damage tolerance analysis

Background

Structural integrity analyses are central to ensuring the safe operation and lifetime of nuclear power components. These analyses are based on assumed cracks, loads, and material parameters, but the overall uncertainty is also influenced by non-destructive testing (NDT), where measurement uncertainties can propagate throughout the entire analysis chain. To obtain a comprehensive picture of all contributing uncertainties, a methodology is required that treats them consistently and enables comparisons between parameters of different nature.

Purpose

The project aims to develop a comprehensive methodology for quantifying uncertainties in structural integrity analyses. By incorporating all relevant parameters—from NDT results to material data and computational models—the methodology will provide a better understanding of how uncertainties interact and influence the overall safety margin. This enables more reliable and transparent assessments of the lifetime of nuclear power components.

Project description

The project develops an integrated methodology for analysing and quantifying uncertainties in structural integrity analyses of nuclear power components. By combining established models in fracture mechanics, load analysis, and material data with uncertainties arising from non-destructive testing (NDT), a coherent mathematical model is created to describe how different parameters influence the overall safety margin. The methodology, based on the statistical approach VMEA (Variation Mode and Effect Analysis) and complemented by numerical analyses, aims to improve the understanding of critical sources of uncertainty and to lay the foundation for a practical engineering tool for reliable lifetime assessments.

The project’s planned deliverables are listed below:

• A methodological description for quantifying uncertainties in structural integrity analyses, documented in an SSM report.
  A computational tool for quantifying uncertainties in structural integrity analyses, implemented in Excel.
  Three case studies illustrating the methodology.
   

The research project is funded by the Swedish Radiation Safety Authority (SSM) and is conducted by DEKRA Consulting (project lead) in collaboration with RISE.