Analysis of the long-term safety of radioactive waste repositories, using performance assessment and other tools, is required prior to implementation. The initial stage in developing a repository safety assessment is the identification of all factors that may be relevant to the long-term safety of the repository and their combination to form scenarios. This must be done in a systematic and transparent way in order to assure the regulatory authorities that nothing important has been forgotten. This report is a review of developments in scenario methodologies based on a large body of practical experience in safety assessments. It will be of interest to radioactive waste management experts as well as to other specialists involved in the development of scenario methodologies.

Executive Summary
1. Introduction
2. Scenario Development - An Overview
3. Key Issues in Scenario Development
4. Concluding Discussion and Remarks
5. References
Appendix 1. List of Workshop Participants
Appendix 2. The Workshop Questionnaire
Appendix 3. Summary of Responses to the Questionnaire
Appendix 4. Papers Submitted to the Workshop
-The Belgian Experience with Scenario Development in Performance Assessments by Jan Marivoet and Peter De Preter
-Development of Scenarios for Radioactive Waste Repositories from an Regulatory Point of View: Status of Discussion in Germany by B. Baltes, K. J. Rohlig and A. Nies
-Scenario Development and Analysis for a Repository in Salt for Highly Radioactive Waste - Proposal for a Screening Process by Siegfried Keller
-The PROSA-Methodology for Scenario Development by J. B. Grupa
-ENRESA's Methodology for Scenario Development and Experience of Application in Performance Assessment by Jesus Alonso, Emiliano Gonzalez and Celsa Ruiz
-Scenario Selection and Demonstrating Compliance Based on Risk, Dose, and Complementary Criteria by Stig Wingefors, Bjorn Dverstorp, Chirstina Kilja and Magnus Westerlind
-Development of a Comprehensive Performance Assessment Systems Analysis Methodology and Supporting Tools, and Their Application in Scneario Evaluation by Neil A. Chapman, Peter Robinson, Jonathan Jack, Mike Stenhouse, Bill Miller, Bjorn Dverstorp, Christina Lilja and Benny Sundstrom
Development of Scenarios within a Systematic Assessment Framework for the Drigg Post-Closure Safety Case by Len Watts, Linda Clements, Mike Egan, Meil Chapman, Paul Kane and Mike Thorne
-Systematic Approach to Scenario Development Using FEP Analysis by L.E. F. Bailey and D. A. Lever
-Scenario Development for the Waste Isolation Pilot Plant Compliance Certification Application by D. A. Galson, P. N. Swift, D. R. Anderson, D. G. Bennett, M. B.Crawford, T. W. Hicks, R. D. Wilmot, and George Basabilvazo
-Feature, Event, and Process Screening and Scenario Development for the Hucca Mountain Total System Performance Assessment by P. Swift, G. Barr, R. Barnard, R. Rechard, A. Schenker, G.Freeze, and P. Burck
-Scenario Development for Safety Assessment of Radioactive Waste Repositories in Switzerland by Trevor Sumerling and Frits von Dorp
-Scenario Development and Analysis in JNC's Second Progress Report by H. Umeki, H. Makino, K. Miyahara and M. Naito