United States Nuclear Regulatory Commission - Protecting People and the Environment

 

GE Nuclear Energy 10 CFR Part 21 Notification
SC00-02 December 18, 2000

To: BWR and PWR Utilities (per Attachment 1)

Reportable Condition [21.21(d)] 60 Day Interim Report [21.21(a)(2)
X Transfer of Information [21.21(b)] Safety Information Communication

Summary:

This notification provides information concerning a discrepancy in the seismic qualification of electrically operated AK-15 and AK-25 low voltage power circuit breakers supplied by GE Nuclear Energy (GE-NE) since 1989.

GE Type AK-15/25 circuit breakers were originally qualified by GE-NE in 1989, based on seismic testing in which an RMS-9 overcurrent trip device was mounted to a manually operated AK-25 breaker. Subsequently, these test results were applied to the seismic qualification of both manually and electrically operated AK-15/25 circuit breakers. However, as a result of recent testing of an electrically operated AK-25 breaker, a revised seismic qualification level has been determined for electrically operated AK-15/25 circuit breakers. The seismic qualification of manually operated AK-15/25 circuit breakers remains unchanged.

Electrically operated GE Type AK-15/25 circuit breakers are used in safety related applications at several nuclear power plants. However, since the plant-specific applications/safety functions and mounting locations/seismic requirements are not known, it is not possible for GE-NE to evaluate the safety significance of this condition to determine if a defect exists in the context of 10 CFR Part 21. We are therefore transferring the available information to the affected licensees for evaluation.

Issued by:____________________________

M. A. Smith, Manager

Safety Evaluations & Engineering Support

GE Nuclear Energy, M/C 772

175 Curtner Avenue, San Jose, CA 95125

(408) 925-1019

SC00-02

Background

GE Type AK-15/25 low voltage power circuit breakers were originally manufactured by the GE Switchgear Department, and are currently supported by GE Industrial Systems, Plainville, CT.

GE-NE dedicates AK-15/25 circuit breakers, and supplies them to nuclear power plants as basic components for safety related applications. Electrically operated AK-15/25 circuit breakers are supplied under the following part numbers:

DD265A1305P005-P007, P013, P016, P018, P022-P023, P026-P029, P032, P037, P038

DD213A6963P001, P002, P005, P008, P009, P010

DD213A9686P002, P006-P008, P010, P012, P013

AK-15/25 circuit breakers were seismically qualified by GE-NE in 1989, based on testing in which an RMS-9 overcurrent trip device was mounted to a manually operated AK-25 breaker. These test results were subsequently applied to the seismic qualification of both manually and electrically operated AK-15/25 circuit breakers.

Recent seismic testing of a replacement 'Y'-relay for use on electrically operated circuit breakers revealed that electrically operated breakers utilizing relay schemes in the closing circuits may not actually be seismically qualified to the same levels as manually operated breakers. This concern was subsequently confirmed by additional testing of an electrically operated AK-25 circuit breaker, which defined revised seismic qualification levels for electrically operated AK-15/25 circuit breakers.

The following table identifies electrically operated GE Type AK-15 and AK-25 low voltage power circuit breakers supplied to licensees since 1989 referencing seismic qualification based on the capability of manually operated breakers. In some cases, GE-NE provided Product Certification Reports containing the test response spectra (TRS) plots.

(see image file of this Part 21 report for this table)

Safety Basis

The seismic qualification for both manually and electrically operated AK-15/25 circuit breakers was originally stated in GE-NE design documents as an IEEE 344-1975 zero period acceleration (ZPA) value of 2.08g. However, recent IEEE C37.98 testing has demonstrated that electrically operated AK-15/25 breakers are seismically qualified to:

  • 1.4g ZPA (with the 125vdc nominal control voltage decreased to 90vdc and an undervoltage device (UVD) installed; or
  • 2.4g ZPA (with 125vdc nominal control voltage and no UVD installed).

SC00-02

Using the correct ZPA value, the IEEE C37.98 standard response spectrum (SRS) curve can be constructed to determine if an electrically operated AK-15/25 circuit breaker meets seismic requirements at each mounting location.

Failure of a circuit breaker to close, remain closed, or close when not signaled would prevent it from performing its safety function in the circuit in which it is installed.

Corrective/Preventive Actions

As discussed previously, seismic testing was performed to determine seismic qualification levels for electrically operated AK-15 and AK-25 low voltage power circuit breakers supplied by GE-NE. A test report has been issued, and affected GE design documents have been revised to reflect the seismic qualification levels defined by the test report.

SC00-02

Attachment 1 - Affected Plants

(see image file of this Part 21 report for this attachment)

Attachment 2 - 10 CFR Part 21 Notifications for 1999-2000

(see image file of this Part 21 report for this attachment)

Scans of this report:

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Page Last Reviewed/Updated Thursday, March 29, 2012