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In the United States, the Atomic Energy Act (AEA) and regulations of the U.S. Nuclear Regulatory Commission (NRC) limit commercial power reactor licenses to a 40-year period and allow these licenses to be renewed for an additional period of 20 years, with no limit to these renewals. The original 40-year term for reactor licenses was based on economic and antitrust considerations, not on technical limitations. Due to this selected period, however, some of the structures and components may have been engineered on the basis of an expected 40-year service life. In order to ensure safe operation of nuclear power plants (NPPs), it is essential that the effects of age-related degradation of plant structures, as well as systems and components, be assessed and managed during both the current operating license period as well as subsequent license renewal periods [1].


In December 1991, the NRC published 10 CFR Part 54 (License Renewal Rule) to establish the procedures, criteria, and standards governing NPP license renewal. In September 1994 the NRC proposed an amendment

FIG. 5.1

SCHEMATIC OF LICENSE RENEWAL PROCESS (Source: fs-reactor-license-renewal.html)

to the Rule, published in May 1995, that focuses on the effects of aging on long-lived passive structures and components and time-limited aging analyses (TLAAs) as defined in 10 CFR 54.21(a)1 and 54.3, respectively. The amendment also permitted greater reliance on the current licensing basis (CLB), the maintenance rule, and existing plant programs.

The License Renewal Rule process and application requirements for commercial power reactors are based on two key principles: (1) that the current regulatory process, continued into the extended period of operation, is adequate to ensure that the CLB of all currently operating plants provides an acceptable level of safety, with the possible exception of the detrimental effects of aging on certain systems, structures, and components (SSCs), and possibly a few other issues related to safety only during the period of extended operation; and (2) each plant’s CLB is required to be maintained. The license renewal process proceeds along two tracks — one for safety issues (10 CFR Part 54) and one for environmental issues (10 CFR Part 51). Figure 5.1 provides a schematic of the license renewal process. The time from submittal of the License Renewal Application (LRA) to issuance of a renewed license is intended to be completed within a 22-month period unless it involves a hearing in which the process may require 30 months.

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