Part 21 Report - 1998-261

ACCESSION #: 9803240135


1400 Opus Place Downers Grove, IL 60515 ComEd March 16, 1998 Document Control Desk United States Nuclear Regulatory Commission Washington, D.C. 20555-001 Subject: Dresden Nuclear Generating Station Units 2&3; NRC Dockets: 50-237 and 50-249 LaSalle County Nuclear Generating Station Units 1 & 2 NRC Dockets: 50-373 and 50-374 Quad Cities Nuclear Generating Station Units 1 & 2 NRC Dockets: 50-254 and 50-265 10CFRPart 21 Notification SBM Control Switch Binding Reference: GE Nuclear Energy January 23, 1998 Transfer of Information Pursuant to 10CFR Part 21.21(b) re: "Spring Return Binding in GE Type SBM Control Switches" Applicability This notification is submitted in accordance with the requirements of 10CFR Part 21. Identification of Facilities and Components Dresden Nuclear Generating Station Units 2 and 3 LaSalle County Nuclear Generating Station Units 1 and 2 Quad Cities Nuclear Generating Station Units 1 and 2 GE Type SBM Control Switches with the spring return function manufactured since March 1996. Applicable date codes: PL, RL, SL, TL, UL, VL, WL, XL, YL, ZL, NM, OM, PM, RM, SM, UM, VM, WM, XM, YM, ZM, NN. Identification of Component Manufacturer/Supplier Manufactured by: GE Electrical Distribution and Control Power Management Malvern, Pennsylvania as commercial grade items g:\sbmp21.doc A Unicom Company Document Control Desk - 2- March 16, 1998 Dedicated by: GE-Nuclear Energy 175 Curtner Ave, San Jose, California 95125 Nature of Defect As described more fully in the referenced GE transfer of information submittal in accordance with 10CFR Part 21.21(b), SBM switches identified above are susceptible to binding which may prevent spring return to reset (return to normal position). The cause of binding is attributed to failure to account for "post mold cure" shrinkage in the design tolerance of the clearance between the phenolic rear bearing support hole and the bearing. This design error did not become apparent until the molds experienced wear to the extent that resulting parts were at the extremes of dimensional tolerances. The post mold cure is normal for the phenolic material and has been shown to take place over a period up to two years after molding is completed. Consequently switches which are constructed from components that are within specification and function fully during acceptance testing may exhibit sluggish return or binding up to two years after assembly. This root cause is supported through GE examination of failed switches which, in each instance, has found the bearing support hole to be undersized (less than minimum inside diameter) and the bearing at or near its maximum allowable diameter. GE testing has also confirmed that switches with bearings that are at their nominal diameter will function properly, even when the support hole is undersized, consequently the failure is not seen in every switch. Time of Discovery Commonwealth Edison determined that the failure was a potential defect subject to the provisions of 10CFR Part 21 on January 27, 1998, Final determination that the defect was reportable per 10 CFR Part 21 was made on March 16, 1998. Number and Location of All Defective Components Commonwealth Edison has determined that suspect SBM switches are not installed at its Braidwood, Byron or Zion Nuclear Generating Stations. Commonwealth Edison Nuclear Generating Stations which have the suspect safety related spring return switches include Dresden, LaSalle County and Quad Cities with two (2), two hundred forty six (246), and three (3) switches installed respectively. LaSalle County Station is currently experiencing binding in 21 of these switches. Corrective Actions Commonwealth Edison facilities having the suspect safety related SBM switches have established Operability Determinations which demonstrate affected systems remain operable while prompt corrective action is pursued. Measures have been taken at Dresden and Quad Cities Stations, which have only 2 and 3 switches susceptible to binding respectively, to heighten operator awareness of the condition through placement of caution cards on the affected switches, Additionally, these facilities have initiated Action Requests to replace the switches with switches not subject to the identified condition at the first available opportunity. Both of the LaSalle County Station units are currently in extended maintenance outages. g:\sbmp21.doc Document Control Desk - 3- March 16, 1998 LaSalle County Station has established operability by heightening operator awareness through communication and is currently establishing the scope of additional compensatory and corrective action plans to demonstrate operability as applied to future plant operating conditions. 10CFR Part 21 Evaluation In The course of evaluating the condition reported by GE in the referenced transfer of information notice, Commonwealth Edison has concluded that, in the absence of compensatory action, the reported deviation substantially increases the likelihood of switch failure when compared to a nominal base case switch failure rate without the reported condition. Since the switches control the operation of various equipment important to plant safety, this increase in failure rate without compensatory action has been determined to constitute a defect representing a substantial safety hazard per the requirements of 10CFR Part 21 and is reportable to the NRC. Contacts Questions pertaining to this notification should be addressed to this office or by contacting: Robert N. Cascarano Jeffrey Nagel Nuclear Engineering Services Technical Support & Parts Engineering Design Basis Programs Central Testing & Materials Engineering Facility 1400 Opus Place, Suite 300 555 Joliet Road Downers Grove, Ill 60515 Bolingbrook, Ill 60446 (630) 663-7489 (630) 783-3150 Sincerely, John B. Hosmer Engineering Vice President Nuclear Generation Group Commonwealth Edison Company cc: A. Bill Beach, Regional Administrator - Region III Senior Resident Inspector, Dresden Station Senior Resident Inspector, LaSalle County Station Senior Resident Inspector, Quad Cities Station NRR Project Manager, Dresden Station NRR Project Manager, LaSalle County Station NRR Project Manager, Quad Cities Station Office of Nuclear Facility Safety - IDNS Irene Johnson DCD Licensing g:\sbmp21.doc Commonwealth Edison Company EXHIBIT A Nuclear Operations Division NEP-10-02 Revision 1 Page 2 of 2 10CFR PART 21 EVALUATION CHECKLIST 1. Engineering Part 21 File Number 98-01 2. Document Generated By General Electric 3. Date of Document 1/23/98 4. Document Identification Number(s) if any GE Notification Number SC98-01 5. Deviation Identified Spring Return Binding in GE Type SBM Control Switches 6. Vendor notified: N/A Date: N/A Person Contacted: N/A 7. Has vendor assume responsibility for evaluating for Part 21 applicability, and has the vendor reported the defect to NRC? YES [] NO [X] Completion date N/A If YES, the evaluation is closed. N/A N/A Evaluating Engineer Date N/A N/A Evaluating Engineer Supervisor Date If NO, then proceed by completing the remainder of the checklist. 8. Is there a Deviation as defined in Section 4.4? Yes [X] No [ ] Provide basis for above conclusion. Notification of possible failure of certain GE Type SBM Control Switches with spring return function was issued by GE as a transfer of information pursuant to 10 CFR 21.21(b). The possible failure was determined to meet the threshold for a substantial safety hazard based on failure analysis indicating a substantial increase in likelihood of switch failure where switches control the operation of various equipment important to plant safety. g:\nep-p21.doc Commonwealth Edison Company EXHIBIT A Nuclear Operations Division NEP-10-02 Revision 1 Page 2 of 2 10CFR PART 21 EVALUATION CHECKLIST 9. Does the Deviation have the potential for impacting system, structure, or component Operability as defined in the Technical Specification? YES [X] NO [ ] If NO, provide reason N/A. If YES, Notify the appropriate Supervisor to determine if an Operability Evaluation must be completed. Operability Assessments have been established for all affected ComEd facilities. 10. Is 10CFR21 notification to NRC required. YES [X] NO [ ] If YES, explain why, and which item of paragraph 5.1.1 occurred/could occur. A major deficiency involving parts which could adversely the capability to shutdown the reactor and maintain it in a safe shutdown condition. (Paragraph 5.1.1.A.3.) If NO, provide basis for conclusion. N/A. Corrective Action which has been, is being, or will be taken. Dresden & Quad Cities will be, replacing switches at first available opportunity. LaSalle will be replacing binding switches at first available opportunity and is currently evaluating scope of additional corrective action. This information is applicable to the following Station(s): [ ] Braidwood [X] Dresden [X] Quad Cities [ ] Byron [X] LaSalle [ ] Zion This evaluation was not performed for the following Stations: [X] Braidwood [ ] Dresden [ ] Quad Cities [X] Byron [ ] LaSalle [X] Zion Provide explanation for each station not evaluated. Braidwood, Byron & Zion evaluated the concern and determined the have no SBM switches of the subject population Evaluation conducted by Date Evaluating Engineer Concur with evaluation and evaluation is closed, Date Evaluating Engineer Supervisor g:\nep-p21.doc March 16, 1998 NEP 10-02 Attachment I Item 98-01 PART 21 EVALUATION SUMMARY GE Type SBM Control Switch Binding - On January 23, 1998, GE issued a 10CFR Part 21.21 (b) Transfer of information concerning the possible failure of certain GE Type SBM Control Switches with the spring return function to reset properly after operation. GE determined it was not possible for them to evaluate the safety functions of the switches which are supplied to several nuclear power plants for unspecified safety related applications. As such, GE concluded it was not possible for them to evaluate the safety significance of possible failures to determine if a defect exists in the context of 10CFR Part 21. - Commonwealth Edison determined the scope of applicability of the reported issue to affect Dresden, LaSalle County, and Quad Cities Stations which have two (2), two hundred forty six (246), and three (3) of the suspect switches installed in the plant. None of the suspect switches have been installed at Braidwood, Byron or Zion stations. - Dresden and Quad Cities Stations have evaluated the condition in accordance with their site Operability Determination procedures, have placed caution cards on the subject switches and initiated action to replace the switches at the first available opportunity. - LaSalle County Station evaluated the condition in light of current plant status, with both units shutdown for extended maintenance outages, and established operability by heightening operator awareness through communication and is currently establishing the scope of additional compensatory and corrective action plans to demonstrate operability as applied to future plant operating conditions. - In the course of evaluating the condition reported by GE, Commonwealth Edison concluded, in the absence of compensatory action, the reported deviation may substantially increase the likelihood of switch failure when compared to a nominal base case switch failure rate without the reported condition. Since the switches control the operation of various equipment important to plant safety, this increase in failure probability without compensatory action has been determined to constitute a defect representing a substantial safety hazard per the requirements of 10CFR Part 21 and is reportable to the NRC. Approval of this summary and the attached notification letter to the NRC signifies appropriate notification to a Commonwealth Edison Officer as require by 10CFR Part 21. NEP 10-02 Attachment 1 Item 98-01 (cont'd) R.N. Cascarano P.C. LeBlond NES - Design Basis Programs NES - Chief, Design Basis Programs Approved Date: J.B. Hosmer Engineering Vice President Attachments 1) GE Transfer of Information Letter SC98-01 dated January 23, 1998 2) March 16,1998 Commonwealth Edison Part 21 Notification to NRC with NEP 10-01, Exhibit A. "Part 21 Evaluation Checklist" dated March 16, 1998 GE Nuclear Energy General Electric Company 175 "illegible print", San Jose, CA 95123 January 23, 1998 98-01NRC.DOC MFN 011-98 Document Control Desk United States Nuclear Regulatory Commission Washington, DC 20555 Subject: Spring Return Binding in GE Type SBM Control Switches This letter provides information concerning the possible failure of certain GE Type SBM Control Switches with the spring return function to reset properly after operation. While the failure mode has been identified as an interference between the rear bearing and its support, the root cause has not yet been determined and the total extent of the problem is not fully known. Until more definitive information is available, GE Nuclear Energy (GE-NE) is conservatively assuming that SBM Control Switches with the spring return function manufactured since March 1996 may be subject to this failure mode. GE-NE is undertaking a test program to determine the root cause failure mechanism and appropriate remedial action (s), but the results of the investigation may not be complete for several weeks. Additional information will be provided when it is available. GE Type SBM Control Switches are manufactured by GE Electrical Distribution and Control (GE-ED&C;) Power Management, Malvern, PA as commercial grade items. GE-NE has dedicated these switches and supplied them to several licensees as basic components for unspecified, safety related applications. Since the specific applications and associated safety functions of the switches are not known to GE-NE, we have transferred information pursuant to 10 CFR Part 21.21 (b) to those licensees known to be affected. However, since additional licensees may have obtained these devices through other dedicating entities, we cannot assure ourselves that all end-users have been notified. We are therefore providing this information to the NRC for appropriate action. On January 6, 1998, GE-NE was advised by a licensee that a safety related SRM Control Switch with the spring return function had failed to reset (return to normal position) properly. The switch (model 16SBMB3A02S152P1) was returned to GE-NE for evaluation with the support of GE-ED&C; Relay Product Engineering. The most probable failure mode was determined to be binding caused by interference between the rear brass bearing and the phenolic rear bearing support. Subsequently, a second failed switch was returned, and examination confirmed the same failure mode. In addition, there have been at least nine more switches identified by the licensee as failing to reset properly after operating correctly for approximately one year. Based on the preliminary investigation, the root cause is suspected to be "post mold cure" shrinkage of the phenolic material used to construct some of the switch components. The failed devices have been examined and, in each instance, the bearing support hole was found to be undersized and the bearing was at, or near, its maximum allowable diameter. Devices with bearing that are at their nominal diameter function properly, even when the support hole is undersized. Consequently, the failure is not seen in every switch. The failure is most likely preceded by a gradual increase in the force required to operate the device and a sluggish return. Although the interference can exist in any SBM Control Switch, binding is primarily an issue in those devices that have the spring return function. In spring return switches, the reset spring does not generate enough torque on the operating shaft to overcome the friction resulting from the interference. Thus, the operating handle, and consequently the contacts, will not reset when the handle is released. The switch contacts will function when the switch is operated failed, if the switch is manually returned to the reset (normal) position, the contacts will also return to their normal configuration. "Maintain position" SBM Control switches may also have the interference, but the force required to overcome the friction resulting from the interference is not great enough to prevent proper function. Nonetheless, it is considered good practice to assure that these switches are in the proper position, as indicated by the match pointer, before releasing the handle. A loss of torque in the tie bolts that secure the switch components has been observed in conjunction with the spring return binding. The loss of bolt torque is also postulated to be the result of the post mold cure shrinkage and, although it has been noted in those devices that have failed, it is not the cause of the binding and does not indicate impending failure. All of the failed switches identified to date were manufactured in the period November 1996 through February 1997. There have been no reports of spring return binding in earlier SBM Control Switches, despite the fact that these switches have been widely used in a variety of application for many years. Until more definitive information is available concerning the root cause, GE-NE is conservatively assuming that SBM Control Switches with the spring return function manufactured since March 1996 may be subject to this failure mode. The affected 2 date codes are PL, RL, SL, TL, UL, VL, WL, XL, YL, ZL, NM, OM, PM, RM, SM, UM, VM, WM, XM, YM, ZM, and NN. There are two safety concerns with regard to spring return binding: (1) possible damage to control circuitry caused by the circuit being maintained in the energized state for a prolonged period; and (2) the possibility that control circuit will be prevented from performing their paper function by the failure of the switch contacts to return to their reset (normal) configuration. The consequences of the loss of torque in the tie bolts that secure the switch components, and the resulting effect on the switch qualification, have been evaluated. The evaluation determined that the loss of torque will not prevent proper operation or degrade the device qualification. If SBM Control Switches with the spring return function, and manufactured since March 1998, have been installed in safety related applications, it is suggested that station personnel who operate these switches be advised to return the operating handle to the normal position after Operation. This will preclude any control circuit difficulties. It should be noted that all of the switches identified to date as failing to reset properly had previously operated correctly for approximately one year. Additional information will be made available when GE-NE has completed the test program to determine the root cause failure mechanism and appropriate remedial [illegible print]. If you have any questions, please call me at (408) 925-1010. Sincerely, Michael A. Smith, Program Manager Safety Evaluations cc: S. D. Alexander (NRC-NRR/DISP/PSIB) G. C. Cwalina (NRC-NRR/DISP/PSIB) J. F. Quirk (GE-NE) H. J. Neems (GE-NE) G. W. Sanders (GE-NE) J. A. Steininger (GE-NE) J. Teague (GE ED&C;/Malvern) GE-NE PRC File 3 10 CER Part 21 Notification GE Nuclear Energy SC98-01 January 23, 1998 To: BWR and PWR Utilities (per Attachment 1) Subject: Spring Return Binding in GE Type SBM Control Switches [ ] 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 the possible failure of certain GE Type SBM Control Switches with the spring return function to reset properly after operation. While the failure made has been identified as an interference between the rear bearing and its support, the root cause has not yet been determined and the total extent of the problem is not fully known. Until more definitive information is available, GE Nuclear Energy is conservatively assuming that SBM Control Switches with the spring return function manufactured since March 1996 may be subject to this failure mode. GE Type SBM Control Switches are manufactured by GE Electrical Distribution and Control (GE-ED&C;) Power Management, Malvern, PA as commercial grade items. GE Nuclear Energy (GE-NE) has dedicated these switches and supplied them to several nuclear power plants for, unspecified, safety related applications. Since the specific application and associated safety functions of the switches are not known, it is not possible for GE-NE to evaluate the safety sign of possible failures to determine if a defect exists in the context of 10CFR Part 21. We are therefore transferring the available information to the known affected utilities for evaluation. GE-NE is undertaking a test program to determine the root cause failure mechanism and appropriate remedial action (s), but the results of the investigation may not be complete for several weeks. A supplement or revision to this 10CFR Part 21 Notification will be issued when additional information is available. Issued by: M. A. Smith, Program Manager Safety Evaluations GE Nuclear Energy, M/C 187 175 Curtner Avenue, San Jose, CA 95115 (408) 925-1019 [Illegible print] SC98-01 Background GE Type SBM Control Switches are manufactured by GE-ED&C; Power Management. Malvern, PA as commercial grade items. GE-NE dedicates these switches and supplies them to nuclear power plants as basic components for safety related applications. On January 6, 1998, GE-NE was advised by a licensee that a safety related SBM Control Switch with the spring return function had failed to reset (return to normal position) properly. The switch (model 16SBMB3A02S1S2P1) was returned to GE-NE for evaluation with the support of GE-ED&C; Relay Product Engineering. The most probable failure mode was determined to be binding caused by interference between the rear brass bearing and the phenolic rear bearing support. Subsequently, a second failed switch was returned, and examination confirmed the same failure mode. In addition, there have been at least nine more switches identified by the licensee as failing to reset properly after operating correctly for approximately one year. Based an the preliminary investigation, the root cause is suspected to be "past mold cure" shrinkage of the phenolic material used to construct some of the switch components. The failed devices have been examined and, in each instance, the bearing support hole was found to be undersized and the bearing was at, or near, its maximum allowable diameter. Devices with bearings that are at their nominal diameter function properly, even when the support hole is undersized. Consequently, the failure is not seen in every switch. The failure is most likely preceded by a gradual increase in the force required to operate the device and a sluggish return. Although the interference can exist in any SBM Control Switch, binding is primarily an issue in those devices that have the spring return function. In spring return switches, the reset spring does not generate enough torque an the operating shaft to overcome the friction resulting from the interference. Thus, the operating handle, and consequently the contacts will not reset when the handle is released. The switch contacts will function when the switch is operated and, if the switch is manually returned to the reset (normal) position, the contacts will also return to their normal configuration. "Maintain position" SBM Control Switches may also have the interference, but the force required to overcome the friction resulting from the interference is not great enough to present proper function. Nonetheless, it is considered good practice to assure that these switches are in the proper position, as indicated by the switch pointer, before releasing the handle. A loss of torque in the tie bolts that secure the switch components has been observed in conjunction with the spring return binding. The loss of bolt torque is also postulated to be the result of the post mold cure shrinkage and, although it has been noted in those devices that have failed, it is not the cause of the binding and does not indicate impending failure. 2 SC98-01 All of the failed switches identified to date were manufactured in the period November 1996 through February 1997. There have been no reports of spring return binding in earlier SBM Control Switches, despite the fact that these switches have been widely used in a variety of applications for many years. Until more definitive information is available concerning the root cause, GE-NE is conservatively assuming that SBM Control Switches with the spring return function manufactured since March 1996 may be subject to this failure mode. The affected date codes am PL, RL, SL, TL, UL, VL, WL XL, YL, ZL, NM, OM, PM, RM, SM, TM, UM, VM, WM, XM, YM, ZM, and NN. Safety Basis There are two safety concerns with regard to spring return binding: (1) possible damage to control circuitry caused by the circuit being maintained in the energized state for a prolonged period; and (2) the possibility that control circuits will be prevented from performing their proper function by the failure of the switch contacts to return to their reset (normal) configuration. The consequences of the loss of torque in the tic bolts that secure the switch components, and the resulting effect on the switch qualification, have been evaluated. The evaluation determined that the loss of torque will not prevent proper operation or degrade the device qualification. Corrective Actions and Preventive Measure If SRM Control Switches with the spring return function, and manufactured since March 1996, have been installed in safety related applications, it is suggested that station personnel who operate these switches be advised to return the operating handle to the normal position after operation. This will preclude any control circuit difficulties. It should be noted that all of the switches identified to date as failing to reset properly had previously operated correctly for approximately one year. Additional information will be made available when GE-NE has completed the test program to determine the root cause failure mechanism and appropriate remedial action(s). 3 SC98-01 Attachment 1 - Affected Plants Utility Plan x Boston Edison Co Pilgrim Carolina Power & Light Co. Brunswick 1 Carolina Power & Light Co. Brunswick 2 Centerior Energy Perry 1 x ComEd CRIT Facility x ComEd Dresden 2 x ComEd Dresden 3 x ComEd LaSalle 1 x ComEd LaSalle 2 x ComEd Quad Cities 1 x ComEd Quad Cities 2 Consumers Power Co. Big Rock Point DTE Energy Fermi 2 Entergy Operations, Inc. Grand Golf x Entergy Operations, Inc. River Bend x GPU Nuclear Corp. Oyster Creek IES Utilities, Inc. Duane Arnold Illinois Power Co. Clinton x Nebraska Public Power District Cooper x New York Power Authority FitzPatrick Niagara Mohawk Power Corp. Nine Mile Point 1 Niagara Mohawk Power Corp. Nine Mile Point 2 x Northern Utilities Millstone 1 Northern States Power Co. Monticello PECO Energy Co. Limerick 1 PECO Energy Co. Limerick 2 PECO Energy Co. Peach Bottom 2 PECO Energy Co. Peach Bottom 3 Pennsylvania Power & Light Co. Susquehanna 1 Pennsylvania Power & Light Co. Susquehanna 2 Pooled Equipment Inventory Co. FIM Public Service Electric & Gas Co. Hope Creek x Southern Nuclear Operating Co. Hatch 1 x Southern Nuclear Operating Co. Hatch 2 x Tennessee Valley Authority Browns Ferry 1 x Tennessee Valley Authority Browns Ferry 2 x Tennessee Valley Authority Browns Ferry 3 x Vermont Yankee Nuclear Power Corp. Vermont Yankee Washington Public Power Supply WNP-2 System 4 SC-98-01 Attachment 1 - Affected Plants Utility Plan x Consumers Power Co. Palisades x Entergy Operations, Inc. Arkansas Nuclear One 1 x Entergy Operations, In. Arkansas Nuclear One 2 x Florida Power & Light Co. Turkey Point 3 x Florida Power & Light Co. Turkey Point 4 x Florida Power & Light Co. Crystal River 3 x Maine Yankee Atomic Power Co. Maine Yankee x New York Power Authority Indian Point 5 x North Atlantic Energy Service Corp. Seabrook x Omaha Public Power District Fort Calhoun x Public Service Electric & Gas Co. Salem 1 x Public Service Electric & Gas Co. Salem 2 x Southern Nuclear Operating Co. Vogtle 1 x Southern Nuclear Operating Co. Vogtle 2 5 SC98-01 Attachment 2 - 10 CFR Part 21 Notification for 1997/98 The following is a list of 10 CFR Part 21 Notifications that GE Nuclear Energy has provided to affected licensees in 1997 and 1999 as Reportable Conditions (RC), Transfers of Information (TI), Safety Information Communications (SC) or 60 Day Interim Reports (60 Day).


6 ComEd 1400 OPUS Place Downers Grove, IL 60515 TRANSMITTAL SHEET DATE: TO: Organization Station Departments FROM: Department: NUCLEAR LICENSING Telephone Number: (630) 663- Transmittal Sheet Plus ___________ Page(s) Telecopy Number: If you have any problems receiving your telecopy, please call (630) 663- 7332 _________________________________________________________________________ NOTES Faxed by Time: Confirmed k:lic faxcov.doc GENERAL INFORMATION or OTHER EVENT NUMBER: 33917 LICENSEE: COMMONWEALTH EDISON NOTIFICATION DATE: 03/18/98 CITY: DOWNERS GROVE REGION: 3 NOTIFICATION TIME: 16:37 [ET] COUNTY: STATE: IL EVENT DATE: 03/16/98 LICENSE#: AGREEMENT: Y EVENT TIME: 00:00[CST] DOCKET: LAST UPDATE DATE: 03/18/98 NOTIFICATIONS MELVYN LEACH, REG 3 RDO NRC NOTIFIED BY: GINA DISON VERN HODGE NRR HQ OPS OFFICER: LEIGH TROCINE RICHARD BARKLEY R1DO THOMAS JOHNSON R2DO EMERGENCY CLASS: NOT APPLICABLE LAWRENCE YANDELL R4DO 10 CFR SECTION: CCCC 21.21 UNSPECIFIED PARAGRAPH EVENT TEXT 10CFR PART 21 NOTIFICATION REGARDING SPRING RETURN BINDING IN GENERAL ELECTRIC (GE) TYPE SBM CONTROL SWITCHES AT DRESDEN, LASALLE, AND QUAD CITIES. THIS NOTIFICATION REFERENCED A GE NUCLEAR ENERGY TRANSFER OF INFORMATION DATED JANUARY 23, 1998, AND IT INVOLVES GE TYPE SBM CONTROL SWITCHES WITH THE SPRING RETURN FUNCTION MANUFACTURED SINCE MARCH 1996. THESE SWITCHES ARE SUSCEPTIBLE TO BINDING WHICH MAY PREVENT SPRING RETURN TO RESET (RETURN TO NORMAL POSITION). THE CAUSE OF THE BINDING WAS ATTRIBUTED TO FAILURE TO ACCOUNT FOR 'POST-MOLD CURE' SHRINKAGE IN THE DESIGN TOLERANCE OF THE CLEARANCE BETWEEN THE PHENOLIC REAR BEARING SUPPORT HOLE AND THE BEARING. THIS DESIGN ERROR DID NOT BECOME APPARENT UNTIL THE MOLDS EXPERIENCED WEAR TO THE EXTENT THAT RESULTING PARTS WERE AT THE EXTREMES OF DIMENSIONAL TOLERANCES. THE POST-MOLD CURE IS NORMAL FOR PHENOLIC MATERIAL AND HAS BEEN SHOWN TO TAKE PLACE OVER A PERIOD OF UP TO TWO YEARS AFTER MOLDING IS COMPLETED. CONSEQUENTLY, SWITCHES WHICH ARE CONSTRUCTED FROM COMPONENTS THAT ARE WITHIN SPECIFICATION AND FUNCTION FULLY DURING ACCEPTANCE TESTING MAY EXHIBIT SLUGGISH RETURN OR BINDING UP TO TWO YEARS AFTER ASSEMBLY. THIS ROOT CAUSE IS SUPPORTED THROUGH GE EXAMINATION OF FAILED SWITCHES WHICH, IN EACH INSTANCE, HAS FOUND THE BEARING SUPPORT HOLE TO BE UNDERSIZED (LESS THAN MINIMUM INSIDE DIAMETER) AND THE BEARING AT OR NEAR ITS MAXIMUM ALLOWABLE DIAMETER. GE TESTING HAS ALSO CONFIRMED THAT SWITCHES WITH BEARINGS THAT ARE AT THEIR NOMINAL DIAMETER WILL FUNCTION PROPERLY EVEN WHEN THE SUPPORT HOLE IS UNDERSIZED. CONSEQUENTLY, THE FAILURE IS NOT SEEN IN EVERY SWITCH. COMMONWEALTH EDISON HAS DETERMINED THAT THE SUSPECT SBM SWITCHES ARE NOT INSTALLED AT ITS BRAIDWOOD, BYRON, OR ZION NUCLEAR GENERATING STATIONS. (Continued on next page) LICENSEE: COMMONWEALTH EDISON PAGE # 2 OF EVENT NUMBER: 33917 HOWEVER, COMMONWEALTH EDISON NUCLEAR GENERATING STATIONS WHICH HAVE THE SUSPECT SAFETY-RELATED SPRING RETURN SWITCHES INCLUDE DRESDEN, LASALLE, AND QUAD CITIES WITH 2, 246, AND 3 SWITCHES INSTALLED, RESPECTIVELY. LASALLE IS CURRENTLY EXPERIENCING BINDING IN 21 OF THESE SWITCHES. THE FOLLOWING FACILITIES WERE ALSO REPORTED TO BE AFFECTED: PILGRIM; RIVER BEND; OYSTER CREEK; COOPER; FITZPATRICK; MILLSTONE UNIT 1; HATCH UNITS 1 AND 2; BROWNS FERRY UNITS 1, 2, AND 3; VERMONT YANKEE; PALISADES; ARKANSAS NUCLEAR ONE UNITS 1 AND 2; TURKEY POINT UNITS 3 AND 4; CRYSTAL RIVER UNIT 3; MAIN YANKEE; INDIAN POINT 3; SEABROOK; FORT CALHOUN; SALEM UNITS 1 AND 2; AND VOGTLE UNITS 1 AND 2.


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