Operating experience has demonstrated that periodic inspection, maintenance, and repair are the essential elements of an overall program to maintain an acceptable level of reliability for structures over their service life. Assessment and management of aging in NPP concrete structures requires a more systematic approach than simple reliance on existing code margins of safety.82 What is required is the integration of structural component function, poten­tial degradation mechanisms, and appropriate control programs into a quantitative evaluation procedure. A methodology for demonstrating the continued reli­able and safe performance of these structures should include (1) identification of structures important to public health and safety; (2) identification of environ­mental stressors, aging mechanisms and their signifi­cance, and likely sites for occurrence; (3) a monitoring — or in-service-inspection-based methodol­ogy that includes criteria for resolution of existing conditions; and (4) a remedial measures program.