ML20070S446

Responds to NRC Ltr Re Violations Noted in Insp Rept 50-293/93-80 on 931018-23.Corrective Actions:Station Maint Procedure Will Be Issued for Aac Sys Which Will Implement Comprehensive Maint Program for SBO DG

ML20070S446
Person / Time
Site:	Pilgrim
Issue date:	03/11/1994
From:	Boulette E BOSTON EDISON CO.
To:	Martin T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20070S442	List: ML20070S446
References
BECO-#94-027, BECO-#94-27, NUDOCS 9405240052
Download: ML20070S446 (4)

Text

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/k I BOSTON EDISON PJgnm Nucicar Power Station Rocky Hdt hoad Plymouth, Massachusntts o2360 E. T. Boulette, PhD March 11,1994 '

sensr Vee President -Nuclear BEco. Ltr. 94- 027 Mr. Thomas T. Martin Regional Administrator. Region I U.S. Nuclear Regultlery Commission 475 Allendale Rd.

King of Prussia, PA 19406 Docket No. 50-293 License No. OPR-35

Subject:

Response to NRC Pilot Station Blackout Team Inspection, NRC Inspection Report No. 50-293/93-80

Dear Sir:

This letter provides Pilgrim Station's schedule for the resolution of four unresolved L ms identified in Inspection Report 93-80 (SBO). This inspection was conducted October 18-23, 1993, at Pilgrim Station.

BACKGROUND Vsing temporary instruction TI 2515/120, " Inspection of Implementation of Station Blackout Rule," the inspection team reviewed station blackout coping systems, plant modifications, emergency diesel generator / alternate ac (AAC) source reliability programs, quality assurance / maintenance for station blackout (SBO) equipment, SB0 procedures, training and interface of the 23kV system with the AAC source.

SCHEDULE OF ACTIONS BEING TAKEN The following is a schedule for the resolution of the four unresolved items that were documented in Inspection Report 93-80 and referenced in this response letter.,

UNR 93-80-01, SB0 Diesel Generator Maintenance Program The emergency diesel generator (EDG) reliability program included. appropriate elements and activities to ensure the selected reliability level is maintained in accordance with the Reliability Prograt outlined in Regulatory Guide 1.155,

" Station Blackout". Pilgrim's AAC source generally met the. criteria of NUMARC 87-00, " Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors", Appendix B, and the guidance of RG 1.155. However, Pilgrim has not implemented a comprehensive maintenance program as specified in NUMARC 87-00, Appendix B, Criterion B.11, 9405240052 940517 PDR ADOCK 05000293 G PDR

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R_e_spon s e

, l A station maintenance procedure will be issued for the AAC system which will l

, implement a ccmprehensive maintenance program for the SB0 DG as specified in  !

NUMARC 87-00. Appendix B, Criteria B.ll. The station maintenance procedure is scheduled for issuance by June 30, 1994. gg UNR 93-80-02, SB0 Diesel Generator Reliability l The reliability test data of the SB0 diesel generator (DG) did not support the 95% reliability value as specified in NUMARC 87-00, Appendix B, Criterion  ;

B.13.

l fles_ pose  !

I The SB0 DG reliability data reviewed was collected from April 6, 1990 to l' September 27, 1993, and consisted of all surveillance tests performed (start.

and load runs). Beginning in 1990 the frequency of testing the SB0 DG was l once per year. A modification was implemented to allow testing on line and we subsequently increased test % to once every 6 months. Until May 1993, no failures of the SB0 DG existed. Since May 1993, five tests have been performed and three of the five tests have failed. On May 10, 1993, we l experienced our first start failure (overspeed relay trip) during the i performance of a temporary procedure for operability modifications. During'a scheduled surveillance test on September 13, 1993, we experienced a load run ,

failure (output breaker trip). In a subsequent test performed for trouble j shooting purposes, on the same day, we experienced a second load run failure -!

(fuel oil leak). In October 1993, the test frecuency was again increased to quarterly to gain increased confidence in reliability. Based on the 10

, surveillance tests performed from April 6, 1990, to September 27, 1993, it became apparent the SB0 DG reliability test data would not support the 95%

reliability value. Additionally, since the exit meeting on October 23, 1993, the SB0 DG was surveillance tested on January 5,1994, with satisfactory results.

The reliability objectives for the Station Blackout Diesel Generator are specified in NUMARC 87-00 Appendix B, Criterion B.13 or RG 1.155. Both of these guidelines specify that reliability of the AAC Power System (the SB0 DG) should meet or exceed 95% as determined in accordance with Nuclear Safety Analysis Center Report NSAC-108 or equivalent methodology, i Nuclear Safety Analysis Center Report NSAC-108, " Reliability of Emergency Diesel Generators at U.S, Nuclear Power Plants", is the accepted method for determining the SB0 DG reliability. This report documents a survey performed to develop EDG reliability values that accurately indicate the contribution of EDG unreliability to plant risk. The results of the survey were based on industry data collected over a three year period that consisted of 22,104 start demands and 13,808 load 'run demands from 52 nuclear power plants.

The reliability of the 580 DG cannot be determined reasonably with the 10 surveillance tests performed from April 6, 1990, to September 27, 1993. NSAC-108 methodology concludes plants having a small number of demands should not be judged unacceptable on the basis the SB0 DG has had a few failures within a year. This topic is discussed in Section 3 of NSAC-108, "Unreliability Values

. for EDG's with few Demands are Frequently Misleading".

Pilgrim Station has a Problem Report Program to identify failures and assign root cause analysis. This program ensures the corrective measures necessary to prevent recurrence of past failures are determined. Significantly, none of

, the 3 failures were repeat failures and are not due to a common cause or 4

failure mode.

Surveillance Testing and Reliability Monitoring Surveillance Testing are required to be performed at specified intervals and are tracked by the Master Surveillance Tracking Program (MSTP). Additionally, SB0 DG trending and

walkdowns are performed by the System Engineer. Almost all maintenance activities are determined or implemented based on information obtained from

, these programs.

The SB0 DG is being analyzed by the Reliability Centered Maintenance Program 1 (RCM). The purpose of this program is to evaluate the critical elements of 1 the system and components to develop a comprehensive preventive maintenance j procedure. The elements of the program consist of failure history, corrective maintenance history, industry opcrating experiences and vendor

, recommendations. The station maintenance procedure is scheduled for issuance

by June 30, 1994. Additionally, the safety enhancement program (SEP) requires that, if the SB0 DG becomes inoperable, the SB0 DG must be restored to operable status within 30 days or the plant should be placed in the hot shutdown condition. Our commitment is to maintain the SB0 DG at a high level of readiness. Our plan ensures long term reliability of the SB0 DG and meets the intent of NSAC-108.

UNR 93-80-03, Lack of Dearaded Voltage Protection when Emergency Buses are Powered by 23kV Source The interface of the 23kV transmission line and shutdown transformer was reviewed to determine its role in the electrical system of Pilgrim Station.

The team had a concern that vital motors connected to busses AS and A6 could be damaged before an SB0 condition is declared. Pilgrim provided preliminary assessment data before the exit meeting. The data indicated that historically, voltage on the 23kV line varied between 22.0 kV and 23.5kV, and .

based on the existing voltage drop calculation, the vital loads connected .to A5 or A6 had sufficient voltage for operation. The team agreed there was no immediate concern. However, the team indicated a degraded voltage condition can still occur at the 23kV source. l i

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.Re sR9B_se The 23kV source is configured into the power distribution system at Pilgrim via the shutdown transformer. When busses A5 or A6 are being powered by the 23kV source, degraded voltage relays are used to monitor AS and A6 bus voltage. These relays will alarm in the Control Room when voltage at the busses is approximately 3950 Volts. However, no automatic actions are provided to isolate the 23kV source during degraded voltage conditions. The existing preliminary evaluation provides adequate load distribution from the shutdown transformer. A final evaluation will be performed to demonstrate that both loadings and degraded voltage protection are within the design parameters. ThefinalevaluationisypectedtobecompletedbyJune6,1994_.

UNR 93-80-04. Lack of Quality Documentation for the 23kV Transmission line Pilgrim indicated that General Design Criteria (GDC) 17 was met utilizing the two 345kV transmission lines. The team noted Technical Specification Section 3.9. A.2.a allowed the reactor to be made critical and operate with only one 345kV transmission line and the 23kV line powering the shutdown transformer.

The team indicated it was not clear which two sources are used to meet GDC 17

, requirements. Analytical documents to substantiate the quality of the 23kV

line for GDC 17 requirements were not available prior to the exit meeting.

Response

! The 23kV source is credited in the Final Safety Analysis Report (FSAR) as being an additional source of offsite power available to power busses A5 and A6. We are currently reviewing and evaluating Pilgrim's FSAR/ Technical i Specifications and their associated amendments to define the design of j Pilgrim's offsite power source. Additionally, we are reviewing.the Technical Specifications to ensure they are consistent with the original design. A preliminary evaluation is currently being prepared with final resolution expected by June 6, 1994.

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-./f Q E. T. Boulette, PhD RAG /dmc/9419 cc: U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Mr. R. B. Eaton Division of Reactor Projects I/II Office of NRR - USNRC One White Flint North - Mail Stop 14D1 11555 Rockville Pike Rockville, MD 20852 Sr. NRC Resident Inspector - PNPS

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