Description:These proceedings present the main findings from, and the papers delivered at, the fourth NEA-EC workshop on Engineered Barrier Systems (EBS), which took place in Tokyo, Japan, in September 2006. This final workshop of the series focused on strategies and methods to demonstrate that EBS designs will fulfill he relevant requirements for long-term safety, engineering feasibility and quality assurance. The workshop highlighted that large-scale experiments have confirmed the feasibility of techniques for manufacturing and installing engineered components in disposal systems and have also provided valuable lessons to improve designs and refine practical aspects to construct and implement EBS.Table of Content : Executive Summary Introduction -The NEA EBS Project -Background to the Workshop on Design Confirmation and Demonstration -Report Structure Workshop Objectives and Structure -National and International Achievements and Ongoing Work on Design Confirmation and Demonstration for Engineered Barrier Systems: Summary of Presentations and Technical Discussions --Approaches and Methods for Demonstration and Confirmation of the Geological Repository Design Concept in the Japanese Programme --Planning, Assessment and Construction of a Drift Seal in a Salt Repository: Overview of Investigations in the German Programme --Performance Assessments for Design Reviews Lessons from the US Programme --Practical Lessons Learnt on the Role of the Engineered Barrier System in a Total System Performance Assessment --Design Confirmation and Demonstration for EBS: Current Developments in Several European National Programmes as Part of the FP6 Euratom ESDRED Project --The KBS-3 EBS Workshops: An Example of Regulator-implementer Pre-licensing Interaction in the Swedish Programme --The EBS Demonstration Programme at SKB: Some Examples --The French Methodology for EBS Confirmation and Demonstration Working Group Findings -Working Group A: Decision Making and Design Factors in the EBS Design Process -Working Group B: Confirmation and Demonstration of the EBS in the Context of Confidence Building -Workshop Conclusions and Recommendations -Conclusions -Recommendations for Future Work References Appendix A Workshop Age Appendix B Papers Presented to the Workshop Appendix C Membership of Working Groups Appendix D List of Participants