Maintaining nuclear competencies in the nuclear industry and nuclear regulatory authorities will be one of the most critical challenges in the near future. As many nuclear experts around the world are retiring, they are taking with them a substantial amount of knowledge and corporate memory. The loss of such employees who hold knowledge critical to both operations and safety poses a clear internal threat to the safe and reliable operation of nuclear facilities. This publication is intended for senior and middle level managers of nuclear industry operating organizations and provides practical information on knowledge loss risk management. The information provided in this publication is based upon actual experiences of Member State operating organizations and is intended to increase awareness of the need to develop a strategic approach and action plans to address the potential loss of critical knowledge and skills; to provide processes and, in conducting risk assessments, to determine the potential for loss of critical knowledge caused by the loss of experienced workers; and to enable nuclear organizations to utilize this knowledge to improve the skill and competence of new and existing workers.