ML20087H263

Provides Response to Violations Noted in Insp Repts 50-361/95-10 & 50-362/95-10.Corrective Actions:New Calculations Recently Performed as Result of NRC Insp

ML20087H263
Person / Time
Site:	San Onofre
Issue date:	08/07/1995
From:	Rosenblum R SOUTHERN CALIFORNIA EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9508170385
Download: ML20087H263 (5)

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Southem Califomia Edison Company P O box i28 S AN C L E M E NTE, CALIFORNI A 976'r4-Ot28 R# CHARD M ROstNBLuM 1 stewone vets eme s+ce =, M asa seso U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Subject:

Docket Nos. 50-361 and 50-362 Reply to a Notice of Violation San Onofre Nuclear Generating Station, Units 2 and 3

References:

(A) Letter, Mr. Thomas P. Gwynn (USNRC) to Mr. Harold Ray (Edison), dated July 6, 1995 (B) Letter, Mr. Walter C. Marsh (Edison) to Document Control Desk (USNRC), " Diesel Generator Loading," dated May 5, 1995 (C) Letter, Mr. R. W. Krieger (Edison) to Document Contral Desk (USNRC), Licensee Event Report No.05-009, dated June 12, 1995 Reference A provided the results of NRC Inspection Report 50-361/95-10 and 50-362/95-10, conducted by Ms. Linda J. Smith on May 3-12, 1 D 45, at San Onofre Nuclear Generating Station, Units 2 and 3. The enclosure to Reference A transmitted a Notice of Violation for not assuring certain electrical power system design basis information was correctly translated into specifications, drawings, procedures, and instructions. This letter provides Edison's reply to each of the three examples in the Notice of Violation.

Example (1)

This example contained two parts involving: (a) the failure to translate the design basis of maintaining a minimum voltage, 75 percent of nominal, at the emergency diesel generator (EDG) terminals into drawings; and (b) the associated failure to translate this criteria into specifications.

Appendix 3A of the Updated Final Safety Analysis Report (UFSAR) commits SONGS 2 and 3 to Regulatory Guide (RG) 1. 9, " Selection of

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March 10, 1971, with certain exceptions described in UFSAR Section 8.1.4.3.2. Not listed among these exceptions is the RG position that EDG design margin should ce at least 75% of the nominal voltage (4.36 KV) at all times during sequencing of Engineered Safety Features (ESF) and emergency loads.

New calculations were recently performed as a result of this NRC inspection. These calculations show that the EDG design margin is momentarily under the 75% criterion during certain assumed accident conditions where multiple pumps may start simultaneously at time zero during diesel load sequencing. As noted in Reference B, these additional loads are classified as

" consequential loads" (not auto-sequenced or auto-connected loads) which may be energized at time zero by demand signals from '

certain automatic devices such as thermostats or pressure switches. Upon further review, Edison confirmed that the EDGs would have functioned satisfactorily although these

" consequential loads" might have caused voltage to momentarily dip below the 75% criterion. Therefore, there is minimal safety significance to this condition.

For part (a), the discovery of a more limiting initial EDG step load than is contained in the existing analysis, resulted in a deviation from the minimum voltage as specified in RG 1.9. This part is fully addressed in References B and C. Reference C provides the reasons for the violation (indeterminate because the error occurred in approximately the 1971-1975 time frame), the corrective steps which have been taken (appropriate Unit 2 Cycle 8 refueling load circuitry modifications), and the corrective steps that will be taken (appropriate Unit 3 Cycle 8 refueling .

load circuitry modifications). In addition, Edison will review I and revise other analyses, as required, to ensure that all effected analyses properly consider the impact of the worst case initial EDG step load.

As noted in Reference A, full compliance was achieved on April 14, 1995, when appropriate Unit 2 and 3 load circuitry modifications provided an interim plant configuration that complied with the minimum voltage requirements of RG 1.9.

For part (b), Reference B addressed not specifying the more limiting step load noted above in the specification for the initial EDG margin qualification (proto-type) test. As noted in  ;

Reference B, Edison determined that the actual proto-type test results were bounding from an inrush current perspective.

Therefore, Edison concluded that the EDG would have functioned as

nd r-[27 Document Control Desk required under the more limiting initial EDG step load. No corrective actions are required for this part and Edison believes it has remained in compliance.

Example (2)

This example dealt with the design basis specified in the SONGS UFSAR that would assure electrical system voltage and frequency restoration in less than 40 percent of each load sequence time interval, not being correctly translated into instructions. The NRC inspector had noted Design Calculation E4C-082, Revision 1,

" System Dynamic Voltages During Design Basis Accident," had incorporated a 60 percent criteria versus 40 percent.

RG 1.9 (Safety Guide 9, " Selection of Diesel Generator Set Capacity for Standby Power Supplies," dated March 1971) requires that during recovery from transients caused by step-load increases or resulting from the disconnection of the largest single load, voltage should be restored to within 10 percent of nominal and frequency should be restored to within 2 percent of nominal in less than 40 percent of each load sequence time interval. This was the RG version referenced in both the SONGS UFSAR and Technical Specification. However, both RG 1.9, Kevisions 2 and 3 (issued in 1979 and 1993, respectively), state in part, " Frequency should be restored to within 2 percent of nominal in less than 60 percent of each load-sequence interval for step-load increase...and voltage should be restored to within 10 percent of nominal within 60 percent of each load-sequence time interval."

Edison could not determine why the incorrect revision to RG 1.9 ,

was used in the 1992 calculation E4C-082 revision. However, Edison believes those personnel involved erroneously believed RG

1. 9, Revision 2 (the version in effect at the time the calculation was revised), was the acceptable UFSAR referenced document. This error may have been influenced by ambiguities and/or inconsistencies in both the UFSAR and Technical Specification references to RG 1.9. These inconsistencies are:

• UFSAR Appendix 3A, Section 3A.l.9, refers to " Regulatory Guide 1.9, ' SELECTION OF DIESEL GENERATOR SET CAPACITY FOR l STANDBY POWER SUPPLIES' (Revision 0, March 1971)." This i actually corresponds to the title and date of Safety Guide 9.  !

RG 1.9 Revision 0 never existed. Revision 1 was issued for  !

comment in November of 1978, but was never officially issued. )

The first of ficial issue of RG 1.9 i s Revision 2, dated l December 1979.

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• UFSAR Section 8.1.4.3.2 gives the title of RG 1.9 as

" SELECTION, DESIGN, AND QUALIFICATION OF DIESEL-GENERATOR UNITS USED AS STANDBY (ONSITE) ELECTRIC POWER SYSTEMS AT NUCLEAR POWER PLANTS," without a revision or issue date. This is the title of Revision 2 to RG 1.9, dated December 1979.

• Technical Specification Bases 3/4.8.1 refers to " Regulatory Guide 1.9, ' SELECTION OF DIESEL GENERATOR SET CAPACITY FOR STANDBY POWER SUPPLIES,' March 10, 1971." As noted above, this title and date refer to Safety Guide 9, dated March 10, 1971.

Edison has concluded there was no safety significance to this example. The results of past ESF tests, performed per surveillance procedure 5023-3-3.12, " Integrated ESF System Refueling Test,"

indicate, in all cases, that voltage recovered to within 10% of nominal and frequency to within 2% in less than 40% of each load sequence interval. In addition, the EDG voltage and frequency acceptance criteria specified in this surveillance procedure has remained consistent with the stipulations in the March 1971 issue of the RG. Accordingly, Edison views this example as a minor administrative error. -

The corrective action taken was to revise the affected calculation to reinstate the RG 1.9, March 1971, 40 percent acceptance criteria. Corrective actions planned are to update the UFSAR to resolve the ambiguities and/or inconsistencies noted above. In addition, Edison will publish required reading to all appropriate personnel to ensure they are aware of how to resolve possible inconsistencies / discrepancies that may arise when using referenced licensing documents.

Example (3)

This example dealt with the design features description in the SONGS UFSAR that would provide protective devices which function to limit the degradation of the Class 1E power systems not being correctly translated into instructions. The NRC inspector had noted that operating restrictions necessary to assure Class 1E 4160V switchgear circuit breakers on Buses 2A04, 2A06, 3A04, and 3A06 would function to interrupt short-circuit currents, were not included in Surveillance Operating Instruction SO23-3-3.23.1,

" Diesel Generator Refueling Interval Tests." These restrictions had been identified in Design Calculation E4C-092, "Short Circuit Studies," Revision 1. The operating restrictions included restricting diesel generator loading to 500 KVAR during testing in the specified configuration.

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I Document Control Desk' The reason for this violation was an isolated personnel error. The individual involved in translating the design requirements into operating procedures perceived a conflict between the design requirements and the TS requirements. The individual believed the off normal alignments, using the Unit Auxiliary Transformer powered from the Main Transformer to feed 1E buses normally powered from ,

the Reserve Auxiliary Transformer, would not occur during implementation of the Refueling Test Procedure (5023-3-3.23.1).

Contrary to management's expectations, the Operations procedure writer had failed to resolve this conflict by contacting the engineering organization for clarification of the requested procedure change.

As corrective actions, the procedure writer was counseled.  :

Procedure SO23-3-3.23.1 has also been revised to include the  ;

appr:priate operating restrictions. Full compliance was achieved on Mty 3, 1995, when procedure 5023-3-3.23.1 was changed.

If you have any further questions, please contact me.

Sincere ,  ;

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./ /l cc: L. J. Callan, Regional Administrator, NRC Region IV J. E. Dyer, Director, Division of Reactor Projects, NRC Region IV K. E. Perkins, Jr . , Director, Walnut Creek Field Office, NRC Region IV J. A. Sloan, NRC Senior Resident Inspector, San Onofre Units 2 & 3 M. B. Fields, NRC Project Manager, San Onofre Units 2 and 3 I

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