Methodology for the selection of external hazards for probabilistic NPP operational safety assessment. Validated procedures for safety document development and assessment of within the PSA domain

The report is structured as follows: (1) External event categories; (2) Main steps in the selection of risk-relevant external events; (3) Step 1: Full list of external events; (4) Step 2: First qualitative external event selection (based on reasonableness; (5) Step 3: Annual frequency estimate for external event initiation; (6) Step 4: First quantitative selection (based on the frequency estimate); (7) Step 5: Qualitative selection based on the potential to initiate an event; (8) Step 6: Quantitative selection (based on the CDF value); and (9) Combinations of external events.