ML20054D861

Final Deficiency Rept Re Sigma Model 9270 Indicator Resistor Problem.All Resistors Will Be Replaced w/27 Kohm,3-watt, wire-wound Resistors Prior to Full Power Operation & Fuel Load

ML20054D861
Person / Time
Site:	San Onofre
Issue date:	04/05/1982
From:	Papay L SOUTHERN CALIFORNIA EDISON CO.
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8204230454
Download: ML20054D861 (3)

Text

{{#Wiki_filter:, Docket Nos. 50-361/362

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April 5, 1982 s Mr. R. d. Fage 1Ke n , Regional Administrator t ps Of fice o f Inspection and En forcement U. S . Iliclear t<egulato ry Commission , RECEfVED Region V V- " 1450 Ma ria Lane , Suite 210 2 ", Walnut Creen, Cali forn ia 94596-5368 g

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De a r Mr . En ge lken : s" Suoject: Docket Nos. 50-361 and 50-362 - Sa n Ono f r e Nuclear Generating Station, Uni t s 2 and .3 . In a letter to your o f fice dated March 9, 1982 we identified a condition wnten we conside r reportable in accordance witn 10C FR5 0. 5 5(e ) . Tne condition involves a potential deterioration o f carbon-type electrical resistors in Model 3270 Luun. graph in s trum en t indicators whicn could, over a period of time, cause tne indicators to malfunction. Enclosed in accordance with 10CFR50.55(e) are twenty-five (2 5) copie s o f a Final tlepor t entitle d, " FINAL REPORT Od S LGMA MODEL 9270 INDICATOR RESISTOR PROBLEM." If you nave any questions regarding this report, we would be pleased to discuss this matter with you at your convenience. Very truly yours , Fnclosure ec: Victor Stello (NRC, director I&E) A. E. Cnaffee (dRC, Sa n Ono f re Units 2 and 3) 09.04280 964 , - k

b i FINAL REPORT ON SIGMA MODEL 9270 i' INDICATOR RESISTOR PROBLEM - San Onofre Nuclear Generating Station Units 2 and 3 i INTRODUCTION [ This report is submitted pursuant to 10CFR50.55(e)(3) . It describes a condition identified by the equipment supplier, International Instruments , a division of Sigma Instruments , Inc., o f Orang e , Connecticut. This report includes a description of the deficiency, analysis of the safety implications, and a summary of the corrective actions to be taken. By letter dated , Ma rch 9, 1982, Edison confirmed notification to the NRC of this i potentially reportable condition for San Onofre Units 2 and 3. BACKGROUND International Instruments, a division of Sigma Instruments , Inc. , notified Bechtel Power Corporation by letter dated December 10, 1981, of a potential problem with the Model 9270 Lumigraph l indicators supplied to San Onofre Units 2 and 3. The potential i problem was described as incorrectly specified resistors within the indicator circuitry, wnich could result in indicator malfunction after one to many years of service. The indicators are installed in control panels located in the main control room, and on the remote shutdown panel. DISCUSSION The following discussion is responsive to 10CFR50.55(e)(3) . DESCRIPTION OF THE DEFICIENCY As described in the vendor's letter, specific resistors, due to their wattage rating and construction (27Kohm, one-watt, carbon composition), can overheat and change value. The result can be display malfunction. The vendor states that it will take one to many years of service before the possible malfunction can occur. I I t' ,e , , -. . .-_. .-~~.._--...,._.4 + - . . , . . . - . _ .-

N i FINAL REPORT ON SIGdA MODEL 9270 Page Two INDICATOR RESISTOR MALFUNCTION San Onofre Ibclear Generating Station, Ubits 2&3 t i ANALYSIS OF SAFETY IMPLICATIONS As identified in this report, the Sigma Model 9270 indicators are used in (pality Class 2, Seismic Category 1 applications. Included in this service is safety-related display instrumentation that is available to the operator to allow him to . adequately monitor conditions in the containment and safety-related process systems throughout all operating conditions of the plant so that he may perform all required manual actions important to plant safety. Also included are indicators used in post accident monitoring instrumentation. , Malfunction of the Sigma Model 9270 indicators as described herein, may prevent the. operator from receiving accurate display information required in order to assess the need for manual , actions important to plant safety. The vendor's statement that ' the potential problem will not appear before one to many years of service indicates that short term malfunctions should not be e xpecte d. CORRECTIVE ACTION b Resolution of the potential problem consists of replacing the presen t resistors with 27Kohm, 3-watt, wire-wound resistors. All work will be completed prior to full power operation for Unit 2 and prior to fuel load for Unit 3. 0807Q - t

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