This publication, which draws upon the outcome of an IAEA coordinated research project, presents methodologies for assessing pipe failure rates in advanced water cooled reactors (WCRs), including a comprehensive review of good practices for the assessment of piping reliability parameters for advanced WCRs. Good practices are those processes and analytical tasks that would be expected in piping reliability analysis in order for the results to be realistic representations of piping structural integrity. This publication builds on technical insights that have been obtained using different methodologies when applied in multiple analytical contexts and responding to the requirements of different national codes and standards. It provides Member States with a strong technical basis for establishing design and plant centric piping reliability parameters for input into probabilistic safety assessment studies, in-service inspection programme development, and operational support. Additionally, an objective evaluation and inter-comparison of methods used in participating Member States is outlined leading to a harmonization of the practices relevant to newly deployable advanced WCRs.

• 1. INTRODUCTION
  • 1.1. Background
  • 1.2. Objective
  • 1.3. Scope
  • 1.4. Structure
• 2. LESSONS LEARNED FROM WCR OPERATING EXPERIENCE
  • 2.1. Piping reliability primer
  • 2.2. Piping material degradation
  • 2.3. Pipe failure manifestations
  • 2.4. Corrosion mechanisms
  • 2.5. Design and construction defects
    • 2.5.1. Design and construction defects event sequence diagram
    • 2.5.2. Effect of welding processes on the material degradation susceptibility
  • 2.6. Fatigue of piping components
    • 2.6.1. Contributing factors to high cycle fatigue
    • 2.6.2. Fatigue induced electro-hydraulic control piping failures
    • 2.6.3. Socket weld integrity management
  • 2.7. Corrosion fatigue
  • 2.8. Flow assisted degradation
    • 2.8.1. Erosion-cavitation
    • 2.8.2. Erosion-corrosion and liquid droplet impingement erosion
    • 2.8.3. Flow accelerated corrosion
  • 2.9. Flow induced vibration and fretting wear
  • 2.10. Stress corrosion cracking
    • 2.10.1. Intergranular stress corrosion cracking
    • 2.10.2. Primary water stress corrosion cracking
    • 2.10.3. Transgranular stress corrosion cracking
    • 2.10.4. Strain induced corrosion cracking
  • 2.11. Hydraulic pressure transients
  • 2.12. Hydrogen combustion in piping
  • 2.13. Hydrogen embrittlement
  • 2.14. Thermal ageing embrittlement
• 3. PIPING RELIABILITY ANALYSIS FRAMEWORK
  • 3.1. Overview
  • 3.2. Nomenclature
    • 3.2.1. Pipe failure mode definitions
    • 3.2.2. Treatment of uncertainties
    • 3.2.3. Structural integrity management
  • 3.3. Meaning of leak and failure
  • 3.4. Practical analysis insights
• 4. EVALUATION BOUNDARY
  • 4.1. Definitions
  • 4.2. Information sources
  • 4.3. In-service inspection programmes
  • 4.4. Flow accelerated corrosion programme plans
  • 4.5. Organization of piping system design information
  • 4.6. Advanced piping design and analysis
• 5. DEGRADATION MECHANISMS AND FAILURE MODES
  • 5.1. Material degradation assessment
  • 5.2. Failure modes of piping
  • 5.3. Degradation mechanisms applicable to advanced WCRs
• 6. EXTRACT AND SCREEN OPERATING EXPERIENCE DATA
  • 6.1. Objectives
  • 6.2. Data quality
  • 6.3. Sources of pipe failure data
  • 6.4. Database accessibility
• 7. METHOD SELECTION
  • 7.1. The contexts and domains of piping reliability analysis
  • 7.2. Piping reliability methodologies
  • 7.3. Applicability of the different methodologies
  • 7.4. Methodology selection criteria
• 8. VALIDATING PROBABILISTIC OUTPUTS
  • 8.1. Basic considerations
  • 8.2. Probabilistic acceptance criteria
    • 8.2.1. Defence in depth considerations
    • 8.2.2 Definition of failure limit state
    • 8.2.3 Selecting an appropriate reliability parameter
    • 8.2.4. Summary
  • 8.3. Sensitivity analysis and influence parameter rankings
  • 8.4. Experimental work and model validation
    • 8.4.1. Alloy 690 research programmes (years 1985−2020)
    • 8.4.2. Estimates of Alloy 690 versus Alloy 600 factor of improvement
• 9. INTERPRETING RESULTS
  • 9.1. Results presentation
  • 9.2. Risk characterization of pipe failures
    • 9.2.1. Risk significance of pipe failures
    • 9.2.2 Acceptability of risk characterization results
  • 9.3. Sensitivity analysis
  • 9.4. Uncertainty analysis
    • 9.4.1. Aleatory vs. epistemic uncertainty
    • 9.4.2. Material degradation and uncertainty analysis
• 10. DOCUMENTATION
  • 10.1. Objectives
  • 10.2. Documentation guidelines
  • 10.3. End user expectations on documentation
    • 10.3.1. US NRC Regulatory Guide 1.178 Revision 2
    • 10.3.2. Structured method for preparing PFM analysis documentation
    • 10.3.3. EPRI-FRANX software for internal flooding PSA
    • 10.3.4. R-Book by Nordic PSA Group
• 11. ADVANCED WCR PIPE FAILURE RATES
  • 11.1. Basic considerations
  • 11.2. Applicability of WCR piping OPEX to advanced WCRs
  • 11.3. Applicability of the analysis framework
  • 11.4. Strategies for updating pipe failure rates
  • 11.5. Ageing factor assessment principles
    • 11.5.1. Research into ageing factor assessment
    • 11.5.2. Temporal trends
    • 11.5.3. Coarse pipe failure rate adjustment factors
• 12. CONCLUSIONS
  • 12.1. Strategies for advanced WCR pipe failure rates estimation
  • 12.2. Insights from the application of different methods
  • 12.3. Main conclusions
  • 12.4. Continued research
• REFERENCES
• CONTENTS OF THE ANNEXES
• GLOSSARY
• ABBREVIATIONS
• CONTRIBUTORS TO DRAFTING AND REVIEW
• STRUCTURE OF THE IAEA NUCLEAR ENERGY SERIES