Fatigue issues for life extension and license renewal

Abstract

Fatigue has been identified as a technical issue potentially affecting the license renewal of nuclear power plants. The NEI License Renewal Industry Reports (IRs) maintained that the current fatigue licensing basis (CFLB) is adequate to manage the effects of fatigue for both the current and the license renewal term, provided that fatigue-sensitive locations are accounted for and managed appropriately. The Nuclear Regulatory Commission (NRC) has identified fatigue as a Generic Safety Issue 166, Adequacy of Fatigue Life of Metal Components. The concerns identified by the NRC in GSI-166 must be evaluated as part of the license renewal process. The concerns of the NRC staff regarding fatigue for license renewal fall into five categories: (1) adequacy of the fatigue design basis when environmental effects are considered; (2) adequacy of both the number and severity of design-basis transients; (3) adequacy of inservice inspection requirements and procedures to detect fatigue indications; (4) adequacy of the fatigue design basis for Class 1 piping components designed in accordance with ANSI B31.1; and (5) adequacy of actions to be taken when the fatigue design basis is potentially compromised. Results of recent investigations by EPRI (Electric Power Research Institute) and other organizations are being used to provide technical justification to support development of an industry approach regarding the management of fatigue during the license renewal term. This paper describes industry activities to develop a fatigue position for license renewal.