Resolution of Generic Safety Issues: Issue 168: Environmental Qualification of Electrical Equipment (Rev. 3) ( NUREG-0933, Main Report with Supplements 1–35 )

DESCRIPTION

As discussed in SECY-93-049,³⁸⁰ the staff reviewed significant license renewal issues and found that several related to environmental qualification (EQ). A key aspect of these issues was whether the licensing bases, particularly for older plants whose licensing bases differ from newer plants, should be reassessed or enhanced in connection with license renewal or whether they should be reassessed for the current license term. The staff concluded that differences in EQ requirements constituted a potential generic issue which should be evaluated for backfit independent of license renewal.¹⁵¹⁸

In the staff's development of an interoffice action plan to address upgrading EQ requirements for older plants during the current licensing term, the staff evaluated the technical adequacy of EQ requirements. As part of this evaluation, the staff reviewed tests of qualified cables performed by SNL, under contract with the NRC. The purpose of these tests was to determine the effects of aging on cable products used in nuclear power plants. After accelerated aging, some of the environmentally-qualified cables either failed or exhibited marginal insulation resistance during accident testing, indicating that qualification of some electric cables may have been non-conservative. Although the SNL tests may have been more severe than required by NRC regulations, the test results raised questions with respect to the EQ and accident performance capability of certain artificially-aged cables. Depending on the application, failure of these cables during or following design basis events could affect the performance of safety functions in nuclear power plants.

CONCLUSION

Based on the existence of an ongoing action plan to address the safety concern and the NRR decision¹⁵¹⁷ to pursue its resolution, the issue was considered nearly-resolved in April 1993. It was later given a HIGH priority ranking in SECY-98-166.¹⁷¹⁸ In accordance with an RES evaluation,¹⁵⁶⁴ the impact of a license renewal period of 20 years was to be considered in the resolution of the issue.

Accelerated aging tests on electrical equipment showed that some environmentally qualified cables either failed or exhibited marginal insulation resistance. Failure of these cables during or following a design-basis event could affect the performance of safety functions. After review and analysis of six LOCA tests, condition-monitoring tests on I&C cables, and information provided by the nuclear industry, the staff concluded that the existing equipment qualification process was adequate to ensure that I&C cables would perform their intended function. Regulatory Issue Summary 2003-09¹⁸⁵² was issued in May 2003, and the issue was RESOLVED with no new requirements for licensees.¹⁸⁵³

REFERENCES

0380. SECY-93-049, "Implementation of 10 CFR Part 54, `Requirements for Renewal of Operating Licenses for Nuclear Power Plants,'" U.S. Nuclear Regulatory Commission, March 1, 1993. [9303030337, 9303100375]. 1517. Memorandum for J. Sniezek from T. Murley and E. Beckjord, "Resolution of Fatigue and Environmental Qualification Issues Related to License Renewal," April 1, 1993. [9304270324] 1518. Memorandum for the Chairman et al. from J. Taylor, "Environmental Qualification of Electric Equipment," May 27, 1993. [9308180153] 1564. Memorandum for W. Russell from E. Beckjord, "License Renewal Implications of Generic Safety Issues (GSIs) Prioritized and/or Resolved Between October 1990 and March 1994," May 5, 1994. [9406170365] 1718. SECY-98-166, "Summary of Activities Related to Generic Safety Issues," U.S. Nuclear Regulatory Commission, July 6, 1998. [9807220129, 9807170226] 1852. Regulatory Issue Summary 2003-09, "Environmental Qualification of Low-Voltage Instrumentation and Control Cables," U.S. Nuclear Regulatory Commission, May 2, 2003. [ML031220078] 1853. Memorandum for W. Travers from R. Borchardt, "Closeout of Generic Safety Issue (GSI) 168, 'Environmental Qualification of Low-Voltage Instrumentation and Control Cables,'" August 14, 2003. [ML032060326]