ML20037B293
| ML20037B293 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, Zion  |
| Issue date: | 11/23/1977 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8009100965 | |
| Download: ML20037B293 (1) | |
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CENIRAL RLO
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I 2 3 1977 Docket Nos.
0-1 50-237, 50-2'9, 50-2 h 50-265, 5
50-304 W
Commenvaalth Edison Company ATTE: Mr. Byron Lee, Jr.
Vice President P.O. Box 767 i
Chicago, IL 60690 Centlement Ecclosed is IE Bulletin No. 77-06 which requires action by you with regard to your power reactor facilities with an operating licensa.
Should you have questions regarding this Bulletin or the actions required of you, please contact this office.
Sincerely, James C. Keppler Director j
Enclosurest i
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LE Bulletin No. 77-06 l
2.
List of IE hiletins i
Issued in 1977 ce v/encis:
Mr. B. B. Stephenson, Station Superintendent Mr. M. J. Kaliv4=n=1r4=,
Station Superintendent Mr. N. k'andke, Plant i
Superintendent Central Files Reproduction Unit NRC 20b PDR i
Local PDR NSIC rL ric fo Anthony Roisman, Esq.,
Attorney 4
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November 23, 1977 IE Bulletin No. 77-06 L
POTENTIAL PROBLEMS WITH CONTAIhMENT ELECTRICAL PENEIRATION ASSEMBLIES Description of Circu= stances:
On October 3, 1977. Northeast Nuclear Energy Company reported to the NRC Region I Office that two control valves installed inside containment at Millstone Unit No. 2 demonstrated abnormal operational characteristics.
The licensee reported that an unexpected closure of a letdown flow stop valve occurred. While investigating this problem, the normally closed safety injection recirculation return line drain valve was found to be in the open position.
Investigation of these events revealed the cause for failure to be electrical shorts between conductors within a contain-ment low voltage penetration assembly.
The licensee subsequently determined that the wiring for both of the valves shared the same low voltage module in an electrical penetration.
Electrical tests by the licensee revealed that 15 of the 85 conductors in the suspect connector module exhibited decreased insulation resistance between conductors. Based on this finding, it is believed that an elec-trical path between adjacent circuits in the connector module was established. This resulted in spurious operation of the valves.
Similar resistance checks perforced on the recaining low voltage modules within the affected penetration assembly revealed 17 additional conductors with reduced insulation resistances. All conductors with resistances less tha'n 20 megohes were disconnected and their circuits were reconnected through spare conductors.
Examination of the three remaining low voltage penetration assemblies, identified 7 additional conductors with resistances of less than 20 cegohms. Each of these circuits were also reconnected through a spare conductor.
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IE Bulletin No. 77-06 November 23, 1977 Investigation showed that the reduced insu3ation resistance was probably caused by moisture accumulation within the penetration assembly together with small fissures in the epoxy seals surrounding each conductor in the module. The licensee believes that moisture penetrating these cracks reduced the insulation resistance between adjacent conductors. To prevent further degradation from moisture buildup within the penetration assemblies, the licensee re-established a dry nitrogen pressure of 24 PSIG in the penetrations.
Subsequently the licensee reported that a second event of a similar nature occurred on October 14, 1977.
In this instance the saeple iso-lation valve for the pressurizer surge line failed to close on command.
Investigation into this event indicated that electrical shorts between conductors due to a moisture accumulation proble was the probable cause for valve risoperation. The shorted wires were disconnected and the valve was de-energized in the closed position.
In discussions on the issue with the licensee and the electrical penetration vendor, General Electric Cocpany, NRC staff determined that maintenance of nitrogen pressure is essential to the integrity of both high and low voltage penetration assemblies. The General Electric Cocpany specifies in its penetration assembly maintenance and oper,ation manual that a 15 PSIG dry nitrogen pressure sheuld be caintained on low voltage units while 30 PSIG should be maintained on high voltage units.
Action To Be Taken By Licensees Of All Fever Reactor Facilities With An Operating License:
Containment Electrical Penetrations - For safety related systems 1.0 Do you have containment electrical penetrations that are of the G. E. Series 100, or are otherwise sinilar in that they depend upon an epoxy sealant and a dry nitrogen pressure environment to ensure that the electrical and pressure characteristics are maintained so as to ensure the functional capability as required by the plant's safety analysis report; namely, (1) to ensure adequate functioning of electrical safety-related eq'ipcent and u
(2) to ensure containment leak tightness?
1.1 Have you experienced any electrical failures with this type of penetration?
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IE Bulletin No. 77-06 November 23, 1977 2.0 Por those penetrations ~. referenced in Ite I above, have you maintained the manufacturer's prescribed nitrogen pressure at all times?
f 2.1 If you have operated the penetrations without maintaining a nitrogen pressure was any degradation of insulation resistance or anomolous component operation detected?
2.2 If no ceasurecents were taken during periods when nitrogen pressure was not caintained, how were you assured that the insulation resistance was not degrading or degraded?
2.3 Eev do you determine that circuit insulation resistances values are satisfactorily maintained?
3.0 Is there a need, as determined by either the vendor or yourself, to maintain penetrations pressurized during a LOCA?
3.1 What ceasures have you taken to ensure that penetrations of this type will perform their design function under LOCA conditions?
(design reviews, analyses or tests) 3.2 Are the measures that provide this assurance adequate to satisfy the Com=ission's regulations (GDC 4, Appendix A to Part 50; QA Criteria, Appendix B to Part 50) 4.0 Provide your res within 10 days. ponse to Items 1.0 through 3.2 above in writingIn addition, provide (Local Time) November 25, 1977. Responses should be submitted to the Director of the appropriate NRC Regional Office. A copy of written responses should be forwarded to the U. S. Nuclear Regulatory Co==ission, Office of Inspection and Enforcecent, Division of Reactor Operations Inspection, Washington, D. C.
20555.
Approved by GAO, B180225 (R0072); clearance expires 7-31-80.
Approval was given under a blanket clearance specifically for identified generic problems.
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0 CONTAIhMENT ELECTRICAL PENETRATIONS (IE Bulletin 77-06)
Oral Response Format Plant Na:ne Docket f l
Regional Office
Contact:
1.0 1.1 2.0 2.1
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2.3 e
3.0 3.1 3.2
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IE Bulletin 77-06 November 23, 1977 LISTING OF IE BULLETINS ISSUED IN 1977 Bulletin Subj ect Date Issued Issued To No.77-05A Supplenent 77-05A to 11/15/77 All PWR Power IE Bulletin No. 77 Reactor Pacilities Electrical Connector with an Operating Assemblies License (OL) or Construction Permit (CP) 77-05 Electrical Connector 11/8/77 All Pk'R Power Assemblies Reactor Pacilities with an Operating License (OL) or Construction Permit (CP) 77-04 Calculational Error 11/4/77 All Pk'R Power Affecting the Design Reactor Pacilities Performance of a System with an Operating for Controlling pH of License (OL) or Containment Sump Water Construction Pollowing a LOCA Permit (CP) 77-03 on-Line Testing of 9/12/77 All W Power the W Solid State Reactor Pacilities Protection System with an Operating License (OL) or Construction Permit (CP) 77-02 Potential Pailure 9/12/77 All Holders of Mechanism in Certain Operating Licenses W AR Relays with (OL) or Construction Relays with Latch Permits (CP)
Attachments 77-01 Pneumatic Time 4/29/77 All Holders of Delay Set Point Operating Licenses Drift (OL) or Construction Fernits (CP) a