ML18101A285

LER 93-014-02:on 930722,determine 4 Kv Vital Bus Second Level Undervoltage Protection Dropout Setpoint Would Not Protect Motors.Detailed Study Showed Motors Would Have Performed Intended Safety functions.W/941005 Ltr

ML18101A285
Person / Time
Site:	Salem
Issue date:	10/05/1994
From:	Hagan J, Pastva M Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-014, LER-93-14, NUDOCS 9410200158
Download: ML18101A285 (6)

Text

e OPS~G Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station October 5, 1994 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 UNIT NO. 1 SUPPLEMENTAL LICENSEE EVENT REPORT 93-014-02 This submittal is made to reclassify an occurrence as a Voluntary Report for informational purposes. This occurrence had been previously identified as reportable pursuant to Code of Federal Regulations 10CFR 50.73.

Sincerely yours, MJPJ:pc Distribution

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v l11e power is in your hands.

9410200158 941005 PDR ADOCK 05000272 95-2189 REV 7-92 s

N~C FORM 366 .S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COME'LY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001 AND TO THE. PAPERWORK REDUCTION PROJECT (31S0-0104), OFFICE OF (See reverse for required number of digits/characters for each block) MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) 05000 272 II PAGE (3)

Salem Generating Station - Unit 1 1 OF 04 TITLE (4) Voluntary Reporting of 4 Kilo-Volt Vital Bus Second Level Undervoltage (UV)

Protection DroJout Setvoint.

EVENT DATE (5) LER NUMBER f6 REPORT NUMBER f7) OTHER FACILITl!':S INVOLVED (8)

I FACILITY NAME DOCKET NUMBER SEQUENTIAL REVISION MONTH DAY YEAR YEAR MONTH DAY' YEAR NUMBER NUMBER Salem Unit 2 05000 311 FACILITY NAME DOCKET. NUMBER

-- -- 05000 07 22 93 93 014 02 .10 05 94 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more (11)

• MODE (9) 1 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73:71(b)

I L:~E~~~O) I 80 I 20.405(a)(1) 0)

• 50.36(c)(1) 50. 73 (a)(2)(v) 73.71 (c) 20.405 (a)(1 )(ii) 50.36(c)(2) 50.73(a)(2)(vii) x OTHER 20A05(a)(1)(iii) 50. 73 (a)(2)(i)

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50.73(a) (2) (viii) (A) (Specify in Abstract I

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below and in Text, NRC 20.405(a) (1) (iv) 50.73(a)(2)(ii) 50. 73 (a)(2)(viii)(B) Form 366A) 20.405 (a)(1 )(v) 50.73(a)(2)(iii) 50.73(a)(2)(x) Voluntarv J LICENSEE:CONTACT FOR THIS LER (12).

NAME .. TELEPHONE NUMBER (Include Area Code)

M. J. Pastva, Jr. - LER Coordinator (609) 339-5165 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

REPORTABLE REPORTABLE CAUSE SYSTEM. COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER TONPRDS TO NPRDS

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SUPPLEMENTAL REPORT EXPECTED 14 EXPECTED MONTH DAY YEAR I YES (If yes, complete EXPECTED SUBMISSION DATE) x NO SUBMISSION DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On 7/22/93, it was determined that the 91. 6% dropout setpoint for second level undervoltage protection of both Salem Units' 4* kilovolt (KV) vital buses would not fully protect the 230 and 460 volt (V) motors should the 4KV bus voltage degrade to less than 93.2%, but greater than 91. 6%. At that time it was concluded the intent of the Updated Final Safety Analysis Report and guidance provided in "Safety Evaluation And Statement Of Staff Positions Relative To The Emergency Power Systems For Operating Reactors" NRC letter, dated 6/2/77, were not fully met. Continued operation of both Sa_lem Uni ts was based upon self-imposed administrative controls on 4KV bus p.lignment until implementation of design changes to change the dropout setpoint. A subsequent detailed study shows the motors would have performed their intended safety functions with the 91. 6% setpoint. As such, this report is made voluntarily for informational purposes.

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NRG FORM 366 (5-92)

REQUIRED NUMBER OF DIGITS/CHARACTERS FOR EACH13LOCK BLOCK NUMBER OF TITLE NUMBER DIGITS/CHARACTERS 1 UP TO 46 FACILITY NAME 8 TOTAL 2 DOCKET NUMBER 3 IN ADDITION TO 05000 3 VARIES 'PAGE NUMBER * .

4 UP T076 TITLE 6TOTAL 5 EVENT DATE 2 PER BLOCK 7 TOTAL 2 FOR YEAR 6 LER NUMBER 3 FOR SEQUENTIAL NUMBER 2 FOR REVISION NUMBER 6 TOTAL 7 REPORT DATE 2 PER BLOCK UP TO 18 FACILITY NAME 8 OTHER FACILITIES INVOLVED 8 TOTAL - DOCKET NUMBER 3 IN ADDITION TO 05000 9 1 OPERATING MODE

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10 3 POWER LEVEL 1

11 REQUIREMENTS OF 10 CFR CHECK BOX THAT APPLIES UP TO 50 FOR NAME 12 LICENSEE CONTACT 14 FOR TELEPHONE CAUSE VARIES 2 FOR SYSTEM 13 4 FOR COMPONENT EACH COMPONENT FAILURE

' 4 FOR MANUFACTURER NPRDS VARIES 1

14 SUPPLEMENTAL REPORT EXPECTED CHECK BOX THAT APPLIES 6 TOTAL 15 EXPECTED SUBMISSION DATE 2 PER BLOCK

VOLUNTARY LICENSEE EVENT REPORT (LER) TEXT CONTINUATION 1 Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-014-02 2 of 4 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xx}

REPORT IDENTIFICATION:

Voluntary Reporting Of 4 Kilo-Volt Vital Bus Second Level Undervoltage (UV) Protection Dropout Setpoint Date of Discovery: 7/22/93 Report Date: 10/5/94 This report was initiated by Incident Report No.93-320.

INITIAL"CONDITIONS:

Unit 1: Mode 1 Reactor Power 80% - Unit Load 815 MWe Unit 2: Mode 1 Reactor Power 100% Unit Load 1140 MWe DISCUSSION:

On July 22, 1993, an initial determination was made that the 91.6%

dropout setpoint for second level undervoltage protection of both Salem Units' 4 kilovolt (KVJ vital buses* {VJ}, would not fully protect the 230 and 460 volt (V) motors should the 4KV bus voltage degrade to less than 93.2%, but greater than 91.6%. At that time it was concluded the intent of the Updated Final Safety Analysis Report

{UFSAR) and guidance provided in "Safety Evaluation And Statement Of Staff Positions Relative To The Emergency Power Systems For Operating Reactors" NRC letter, dated June 2, 1977, were not fully met. This was identified during a self-initiated adequacy review to ensure the intent of the 1977 NRC letter was being met. Continued operation of both sa.lem Units was based upon ensuring that the 4KV bus voltage would be maintained at or above 93.2% by imposition of additional administrative controls on 4KV bus alignment until implementation of design changes to change the dropout setpoint. The NRC was notified of this determination pursuant to 10CFR50.72(b) {l) (ii) (B). In addition, on August 20, 1993, this issue was reported pursuant to the requirements of 10CFR50.73(a) (2) (ii) (B) and 10CFR50.73(a) (2) (v) (D)

A subsequent detailed study shows the motors would have performed their intended safety functions with the 91.6% setpoint. Therefore, a reportable occurrence with the setpoint, as described, does not

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VOLUNTARY LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-014-02 3 of 4 DISCUSSION: (cont'd) exist pursuant to 10CFR50.72 or 10CFR50.73.

ANALYSIS:

In July 1993, a self-initiated adequacy review concluded the 91.6% .

dropout setpoint for second level undervoltage protection of both Salem Units' 4 KV vital buses, would not fully protect 230 and 460V motors. Continued operation of both Salem Units was based upon the following self-imposed administrative controls regarding 4KV bus alignment:

1. Hourly logging of 4KV vital bus voltages, maintained between 4.3KV and 4.5KV.

2. Maintaining only two vital buses energized from their operating transformer, if both the corresponding group buses are on their respective Auxiliary Power Transformer (APT) .

3a. Maintaining three vital buses energized from the operating transformer, if one of the corresponding group buses is transferred to the operating Station Power Transformer (SPT) or 3b. Maintaining three vital buses energized from the operating transformer, if the load which can be transferred from the APTs is reduced by 5 mega volt amps.

However, revision 01 to calculation ES-15.00S(Q), "Salem Units 1 and 2 Degraded Grid Study", shows worst case recovery vital bus voltage is 93.2% of 4KV following transfer of the APTs to the SPTs.

A subsequent detailed study shows that the 230 and 460V motors will perform their safety functions with the 91.6% setpoint. As such, the self-imposed administrative controls serve to add greater enhancement to the performance of these motors, from a reliability standpoint.

The initial determination that the 91.6% dropout setpoint did not meet the intent of the UFSAR and the BTP resulted from overly restrictive conservatism in reviewing/assessing the ES-15.00S(Q), revision 01 calculations, without benefit of the results of the subsequent detailed study. Dropout setpoint selection at 91.6%*was based on the lowest voltage the 4.16KV motors could be allowed to operate (i.e.

90%) due to voltage drops in the motors' cables and relay inaccuracy considerations.

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VOLUNTARY LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit l 5000272 93-014-02 4 of 4 SIGNIFICANCE:

This report is made for informational purposes, since the dropout setpoint provides adequate protection for the worst case design basis event. As such, this issue is not reportable pursuant the requirements of 10CFR50.73.

ACTIONS TAKEN/PLANNED:

Related design changes, including changing the dropout setpoint, were implemented on Unit 1 during its last refueling outage and are scheduled for Unit 2 during its next refueling outage.

The self-imposed administrative controls will be maintained for Unit 2 until implementation of the aforementioned design changes.

License Change Requests have been submitted to revise Technical Specifications regarding the second level undervoltage relay setpoint.

The importance of adequately considering lower voltage levels whenever evaluating 4KV setpoints for changes has been discussed with the Electrical Engineering Group.

Appropriate changes to the UFSAR will be implemented.

Appropriate documents will be revised to incorporate the results of the subsequent study involving the 91.6% dropout setpoint.

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tions MJPJ:pc SORC Mtg.94-077