In this volume, the National Research Council examines problems arising throughout government-owned, contractor-operated facilities in the United States engaged in activities to build nuclear weapons. The book draws conclusions about and makes recommendations for the health and safety of the nuclear weapons complex and addresses pressing environmental concerns. In addition, the book examines the future of the complex and offers suggestions for its modernization. Several explanatory appendixes provide useful background information on the functioning of the complex, criticality safety, plutonium chemistry, and weapons physics.