A license renewal applicant of a U.S. nuclear power plant is required to demonstrate that all the time-limited aging analyses (TLAAs) applicable to the facility are valid for the period of extended operation, or have been projected through the expiration of the period of extended operation, or that the effects of aging associated with the TLAAs will be adequately managed during the period of extended operation. Common to license renewal applications are four TLAAs: (1) reactor vessel (RV) neutron embrittlement analyses, (2) fatigue analyses of ASME Section III metal components, (3) environmental qualification analyses of safety-related electrical equipment, and (4) low-cycle fatigue analyses of reactor coolant pump flywheels. The RV neutron embrittlement analyses include the determination of neutron fluence for the RV at the end of the period of extended operation (end-of-extended-license fluence), and evaluation of the following analyses that are based on the end-of-extended-license fluence: drop in Charpy upper-shelf energy, reference temperature for nil-ductility transition, pressure-temperature limits, and BWR vessel circumferential weld examination relief and axial weld failure probability. This paper discusses these four common TLAAs and focuses on the regulatory basis for accepting them as part of the license renewal application; it also discusses the lessons learned from reviewing the license renewal applications.

This content is only available via PDF.
You do not currently have access to this content.