Probabilistic methods are increasingly being used to complement deterministic methods in assessing the safety and ensuring the reliability of research reactors. Addressing features specific to research reactors, this publication suggests a practical approach for the development and implementation of a project using probabilistic methods in terms of objective, scope, data and modelling, as well as the application of results to enhance safety and reliability. This publication is intended to be used by operating organizations, regulatory bodies and technical support organizations when performing or reviewing research reactor assessments in which probabilistic methods are applied. It will ideally be read in conjunction with relevant IAEA Safety Standards Series publications and technical guidelines for safety analysis, operation and maintenance, and component reliability data for research reactors.

• 1. INTRODUCTION
  • 1.1. Background
  • 1.2. Objective
  • 1.3. Scope
  • 1.4. Structure
• 2. GENERAL CONSIDERATIONS REGARDING PROBABILISTIC methodS FOR RESEARCH REACTORS
  • 2.1. Introduction
  • 2.2. Objective and scope of a project using probabilistic methods
  • 2.3. Management of a project using probabilistic methods
    • 2.3.1. Project proposal
    • 2.3.2. Structure of a project team
    • 2.3.3. Selection of working methods and procedures
    • 2.3.4. Time schedules
    • 2.3.5. Documentation
    • 2.3.6. Review
  • 2.4. Benefits and limitations of probabilistic methods
    • 2.4.1. Benefits
    • 2.4.2. Limitations
  • 2.5. Establishing quality attributes for probabilistic methods
  • 2.6. Application of probabilistic methods for the safety assessment and the ram analysis
• 3. PROBABILISTIC SAFETY ASSESSMENT
  • 3.1. Introduction
    • 3.1.1. Objectives
    • 3.1.2. Methodology
    • 3.1.3. Levels
  • 3.2. Scope of probabilistic safety assessment
    • 3.2.1. Analysis level
    • 3.2.2. Stages of facility lifetime
    • 3.2.3. Potential sources of radioactive release
    • 3.2.4. Facility operational states
    • 3.2.5. Accident initiating events
    • 3.2.6. Information alignment
  • 3.3. Major tasks in level 1 probabilistic safety assessment
    • 3.3.1. Background
    • 3.3.2. Identification of potential sources of radioactive release
    • 3.3.3. Definition of damage states
    • 3.3.4. Selection, screening and grouping of initiating events
    • 3.3.5. Accident sequence modelling
    • 3.3.6. Data compilation and analysis
    • 3.3.7. System modelling
    • 3.3.8. Quantification of accident sequences
    • 3.3.9. Assessment of end state frequencies
    • 3.3.10. Uncertainty, sensitivity and importance analysis
    • 3.3.11. Documentation
  • 3.4. Major tasks in level 2 probabilistic safety assessment
    • 3.4.1. Background
    • 3.4.2. Identification of relevant facility design features
    • 3.4.3. Definition of facility damage states
    • 3.4.4. Facility damage states not initiated by bypass of the confinement or containment
    • 3.4.5. Facility damage states with bypass of the confinement or containment
    • 3.4.6. Final selection of facility damage states
    • 3.4.7. Data compilation and analysis
    • 3.4.8. Confinement or containment analysis
    • 3.4.9. Characterizing end states of confinement/containment event trees
    • 3.4.10. Grouping end states of confinement/containment event trees into release categories
    • 3.4.11. Source term analysis
    • 3.4.12. Uncertainties
    • 3.4.13. Human reliability analysis
    • 3.4.14. Documentation
  • 3.5. Major tasks in level 3 probabilistic safety assessment
    • 3.5.1. Background
    • 3.5.2. Description of the radionuclide release
    • 3.5.3. Environmental transport mechanisms
    • 3.5.4. Exposure pathways and dose calculation
    • 3.5.5. Economic consequences
  • 3.6. Low power and shutdown probabilistic safety assessment
    • 3.6.1. Background
    • 3.6.2. Major steps
• 4. RAM ANALYSIS
  • 4.1. Introduction
  • 4.2. Fundamentals of ram analysis
    • 4.2.1. Reliability
    • 4.2.2. Availability
    • 4.2.3. Maintainability
  • 4.3. Project framework for the application of ram analysis
  • 4.4. Major elements of ram analysis
    • 4.4.1. Objective and scope
    • 4.4.2. Project management for RAM analysis
    • 4.4.3. Facility familiarization
    • 4.4.4. Functional analysis
    • 4.4.5. Models for RAM analysis
    • 4.4.6. Data assessment and parameter estimation for RAM analysis
    • 4.4.7. Uncertainty, sensitivity and importance analysis
    • 4.4.8. Requirements of RAM analysis
  • 4.5. Root cause analysis
  • 4.6. Ram analysis results and recommendations
    • 4.6.1. Discussion, interpretation and presentation of results
    • 4.6.2. Documentation
• 5. TRAINING AND EDUCATION ON THE USE OF PROBABILISTIC MethodS
  • 5.1. Training of operating personnel and regulatory staff
  • 5.2. Training of probabilistic method practitioners
• Appendix ITYPICAL TABLE OF CONTENTS FOR A LEVEL 1 PROBABILISTIC SAFETY ASSESSMENT REPORT
• Appendix IIEXAMPLES OF FACILITY OPERATIONAL STATES FOR HIGH POWER RESEARCH REACTORS
• REFERENCES
• ANNEXES: SUPPLEMENTARY FILES
• ABBREVIATIONS
• CONTRIBUTORS TO DRAFTING AND REVIEW