ML18022A525

LER 87-020-00:on 870413,reactor Trip Setpoints on All Three Overtemp Delta Temp (Odt) Bistables Incorrectly Set.Caused by Apparent Design Oversight in Odt Circuit Design & Vendor Testing Methodology.Test Procedures revised.W/870513 Ltr

ML18022A525
Person / Time
Site:	Harris
Issue date:	05/13/1987
From:	Howe A, Watson R CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
HO-870429-(O), LER-87-020, NUDOCS 8705190612
Download: ML18022A525 (6)

Text

REQUL>" RY INFORMATION DISTR IBUTI 'YSTEM (R IDS)

- I ACCESSIQN NBR: 8705190612 DOC. DATE: 87/05/13 NOTARIZED: NO DOCKET FACIL: 50-400 Sheal on Harl is Nuclear Paver Plant> Unit 1. Carolina 05000400 AUTH. NAME AUTHOR AFFILIATION HOWE> A.

Carolina Power Zc Light Co.

WATSON> R. A. Carolina Power 5 Light Co.

REC IP. NAME RECIPIENT AFFILIATION SUB JECT: LER 87-020-00: on 870413> reactol tl'ip setpoints on all three overtemperatul e delta temp bistab les incorrectly set. Caused bg appal ent design ovel'sight in OTAT circuit design 8c vendol

'esting methodology. Test procedures revised. M/870513 ltr.

DISTRIBUTION CODE: IE22D COPIES RECEiVED: LTR 1 ENCL J SIZE: 5 TITLE: 50. 73 Licensee Event Repol t (LER)> Incident Rpt> etc.

NOTES: Application +or permit reneu:al filed. 05000400 REC IP I ENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR EN" L PD2-1 LA 1 1 PD2-1 PD 1 1 BUCKLEY. B 1 1 INTERNAL: ACRS MICHELSON 1 ACRS MOELLER 2 2 AEOD/DOA 1 1 AEOD/DSP/RQAB 2 2 AEOD/DSP/TPAB 1 DEORO NRR/DEST/ADE 0 NRR/DEST/*DS 0 NRR/DEST/CEB 1 NRR/DEST/Et B 1 NRR/DEST/ICSB 1 NRR/DEST/MEB 1 NRR/DEST/MTB 1 1 NRR/DEST/PSB 1 NRR/DEST/RSB 1 NRR/DEST/SGB 1 NRR/DLPG/HFB 1 NRR/DLPG/GAB 1 NRR/DOEA/EAB 1 1 NRR/DREP/EPB 1 NRR/DREP/RAB 1 1 NRR/DREP/RPB 2 2 S/ILRB 1 NRR/PMAS/PTSB 1 REG FIL 02 RES DEPY GI N~ L'E 01 1 1 EXTERNAL: EG8cG GROH> M 5 5 H ST LOBBY NARD '1 LPDR 1 NRC PDR 1 NSIC HARRIS. J 1. 1 NSIC MAYS> G 1 TOTAL NUMBER OF COPIES REQUIRED: LTlR 43 ENCL 41

NilC Form U.S. NUCLEAR REOULATORY COMMISSION 388'()43)

'I APPROVED OMB NO. 3160410C EXPIRES: 8/31/88 LICENSEE EVENT REPORT (LER)

PA E 3 FACILITY NAME (I)

SHEARON HARRIS TITLE (el UNIT 1 0500040010F4 DOCKET NUMBER (2)

OVERTEMPERATURE DELTA TEMPERATURE REACTOR TRIP DESIGN DEFICIENCY EVENT DATE (5) LER NUMBER (8) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR ~

FCi SEOUENTIAL lyric REVISION MONTH NUMBER NS NUMBER OAY YEAR FACILITYNAMES DOCKET NUMBE R(S) 0 5 0 0 0 0 1 3 8 7 8 7 0 2 0 0 0 05 13 8 7 0 5 0 0 0 OPERATINO THIS REPORT IS SUBMITTED PURSUANT T0 THE REOUIREMENTS OF 10 CFR (): (Crrecir one or more of tne follovffnP) ill)

MODE (0) 20A02(b) 20AOS(c) 60.73(e) (2) IN) 73.71(lr)

POWER 20AOS(e) (I ) (I) 50.38(c) (I) 50 73(e) (2)(v) 73.71(c)

LEVEL 20AOS(e) ll) (ii) 50.38 (c) (2 I 60.73(e)(2)(vii) OTHER (Speelfy In AOrc'eet Oerow end fn Terr t. HRC Form c Bo 'Q g'oyrgp~ 20.405 (v) (I ) (i(i) S0.73( ~ ) (2) (I) 60.73( ~ )(2)(vill)(A) 366A) 20A06(e)(1)liv) 50.73( ~ ) (2) lii) 50.73 ( ~ ) (2) ( vl8) (8) 20AOS (e)(1) Iv) 60.73(e) (2) Bii) 60.73( ~ )(2)(e)

LICENSEE CONTACT FOR THIS LER l12)

NAME TELEPHONE NUMBER AREA CODE ~

ANDREW HOWE REGULATORY COMPLIANCE 9 19 362 -27 18 MANUFAC. REPORTABLE

'vi) i

@'I(

'v COMPLETE ONE LINE FOR EACH COMPONENT FAILURE OESCRIBEO IN THIS REPORT (13)

MANUFAC EPORTABLE XP

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CAUSE SYSTEM COMPONENT TURER TO NPRDS CAUSE SYSTEM COMPONENT TURER N

TO NPRDS

'1p A .,A V V SUPPLEMENTAL REPORT EXPECTED (IC) MONTH DAY YEAR EXPECTED SUBMISSION DATE (16)

YES Iffyn, complete EXPECTED SUBMISSION DATE) NO ABSTRACT fLimir to tcOO rpecn, Je., epproefmetery fifteen rrnorecpece typewritten finn) (18)

Abstract:

At 0930 on April 13, 1987, it was discovered that the reactor trip setpoints on all three Overtemperature Delta Temperature bistables were incorrectly set. This situation was caused by a design deficiency affecting the calibration of the differential neutron flux input to the channel, such that the setpoint for reactor trip would not begin to decrease when the dq signal reached -34X as required, but instead would be delayed until approximately

-37.5X.

The channels were declared inoperable, Technical Specification 3.0.3 was applied, and preparations for plant shutdown were begun. By 1040, two of the three channels were adjusted using actual NI signals so that the OTAT setpoint would be reduced properly. Reactor operation was continued as allowed by Technical Specifications. All three channels were restored to operable status at 1541 on April 14, 1987.

8705190612 870513 PDR *DOCK 05000400 S PDR NRC Form 388 (9.83)

NRC Form 368A U.S. NUCLEAR REGULATORY COMMISSION (84)3) r r LICEN EVENT REPORT (LER) TEXT CONT JATION APPROVED OM8 NO. 3150-0104 FACILITY NAME (1) r.

'OCKET NUMBER (2) LER NUMBER (6)

YEAR Nk'EOUENTIAL NUMBER EXPIRES:

Mo 8/3(/88 REVISION NUMBER PAGE (3)

SHEARON HARRIS UNIT 1 o s o o o 4 0 0 8 7 0 2 0 0 0 0 2 OF 0 4 TEXT //moro Spoco /4 BEO)IIBIL INB //I/ooo/ HRC %%drm 386ASI (I7)

'During a review of surveillance test procedures against the requirements of the Westinghouse Startup Manual procedures, it was noted that the differential neutron flux (dq) input to the Overtemperature Delta Temperature (OTAT) reactor trip channel was not adjusted using inputs directly from the Nuclear Instrumentation (NIS) cabinets. Instead, a simulated NI signal was used to calibrate the OTAT channel.

Test data was obtained on April 8, and a review of this data revealed a conservative shift of the dq input required to cause a penalty decrease in the OTAT setpoint for a positive differential. With an input of +9X differential flux, a setpoint shift was observed although no shift is required by Technical Specifications until +10X. No data was available for the negative dq input to the OTAT channel since the surveillance test used a -30X dq test signal for calibration, and the setpoint shift is not required until -34X.

Additional data collected on April 10 (confirmed April 11), showed that when an OT/LT channel received a signal from the actual NI isolation amplifier a gain of 0.8 existed for the upper neutron flux potentiometer, while the lower neutron flux potentiometer had a gain of 0.773. This was observed on all three channels. CP&L and Westinghouse personnel continued to investigate this discrepancy. On April 13, the data was independently reviewed by the scaling group and it was determined that a nonconservative setpoint existed 'in the OTdT reactor trip setpoints for the differential neutron flux input for negative differential. At 0930 on April 13, with the plant in Mode 1 at 63X thermal power level, the Shift Foreman declared all three OTAT protection channels inoperable.

Technical Specification 3.3.1 requires two of the three OTAT channels to be operable in Modes 1 and 2. With all three channels declared inoperable, Specification 3.0.3 is applicable. Immediate action was initiated to prepare for a plant shutdown to hot standby by 1630 that day. In addition, action was begun to conservatively calibrate the OTAT channels. At 1040, two of the three channels potentiometers were readj usted using the actual NI signal to obtain the correct gain of 0.8 and were declared operable. Plant operation was continued as permitted by Specification 3.3.1. The third channel was kept out of service to support troubleshooting performed to identify the problem.

All three OTAT channels were returned to service at 1541 on April 14.

NRC FORM SBBA *U.S.GPO:1888.0.624 538/455 (84)3)

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION (94)3)

LICE EVENT REPORT HLER) TEXT CON ATION APPROVED OMB NO, 3150-0 I 04 EXPIRES: 8/31/88 FACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SEOUENTIAL REVISION YEAR g$ NUMBER NUMSEA SHEARON HARRIS UNIT 1 o s 0 0 o 400 8 7 0 2 0 00 03 OF 0 4 TEXT /P IINss 4pocs k rsqoiaf, Uro sdaWon/I //RC %%drrn 35649/ (ITl Cause'.

An apparent design oversight existed in the OTAT circuit design and the vendor testing methodology, which provides for the use of a test switch and simulated test signals to permit calibration of the instrument loop during shutdown conditions. The NIS test signal applied during calibration to simulate lower flux to the OTAT channel did not duplicate the actual signal input by the NIS cabinet. Troubleshooting of the C loop channel (T-432) revealed that the negative input signals for upper and lower neutron flux were grounded at the NIS cabinet. When the PIC loop was placed in test to inject a calibration signal, the negative lead was no longer grounded. Calibration with the ungrounded negative input changed the lower flux potentiometer gain from 0.8 during calibration to 0.773 when the system was returned to normal with a grounded negative lead. This situation existed only on the lower neutron flux channel due to,the physical arrangement of the circuit. The result was that the negative dq penalty to the OTAT reactor trip setpoint would begin at approximately "37.5X instead of -34X as required by Table 2.2-1, Reactor Trip System Instrumentation Trip Setpoints, of the Technical Specifications.

~Anal aia:

The OTAT reactor trip provides core protection to prevent a departure from nucleate boiling (DNB) for all combinations of pressure, power, coolant temperature, and axial power distribution, provided the transient is slow with respect to Reactor Coolant System piping transit delays from the core to the temperature detectors. If axial power peaks are greater than design, as indicated by the difference between top and bottom power range nuclear detectors, the reactor trip setpoint is automatically reduced.

This event could have resulted in the reactor power level being higher than permitted by Technical Specifications, had an axial power imbalance occurred, reducing the allowed margin to DNB. At no time, however, did such an axial power imbalance occur. The plant was being operated only up to 75X thermal power level as part of power ascension testing, which provided a further margin to the OTAT trip setpoint of 109Z (nominal without penalties).

Operation of the plant with large negative axial power imbalances is prohibited by Technical Specification 3.2.1.

This situation was investigated for potential reportability under 10CFR21 and was determined by CPGL to be not reportable.

This event was initially reported under 10CFR50.72(b)(1)(ii) as a serious degradation of the nuclear plant principal safety barrier. Based on further evaluations, no substantial safety hazard existed and the event is reportable under 10CFR50.73(a)(2)(i)(B) as a violation of the Technical Specifications.

NRC FORM SSSA *U.B.GPO:1986-0.624 638/455 (983)

NRC Form 366A VS. NUCLEAR RFGVLATORY COMMISSION (983)

LICE EVENT REPORT (LER) TEXT CON ATION APPROVED OMS NO. 3(50&(04 EXPIRES, 8/31/88 FACILITY NAME (ll DOCKET NUMBER 121 LER NUMBER (6) PAGE (3)

YEAR g'j SEGVENTIAL ~Mj REVISION NVM ER 484 NVMSER SHEARON HARRIS UNIT 1 s o o o4 00 8 7 0 2 0 0 0 0 4 oF 0 4 TEXT /N'rr>>ro <<>>c>> /4 to/O/ror/ Irro //I/oo>>/ NRC Form 3684 9/ (IT)

Corrective Action.'

1. Surveillance test procedures which calibrate the OTDT channels have been revised to account for the grounded negative input for the neutron flux potentiometers.

2. Other PIC cards have been bench tested with grounded and ungrounded inputs and no further cases of this problem were observed.

3. Westinghouse has been advised of the situation and plans to issue a technical bulletin.

NRC FORM SddA *U.S.GPD:1986.0 624 538/455 (94)3)

g~L Carolina Power 8 Light Company HARRIS NUCLEAR PROJECT P.O. Box 165 New Hill, NC 27562 MAV I 8 mS7 File Number.'HF/10-13510C Letter Number: HO-870429 (0)

U.S. Nuclear Regulatory Commission ATTN: NRC Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 DOCKET NO. 50-400 LICENSE NO. NPF-63 LICENSEE EVENT REPORT 87-020-00 Gentlemen'.

In accordance with Title 10 to the Code of Federal Regulations, the enclosed Licensee Event Report is submitted. This report fulfills the requirement for a written report within thirty (30) days of a reportable occurrence and is in accordance with the format set forth in NUREG-1022, September, 1983.

Very truly yours, R. A. Watson Vice President Harris Nuclear Project RAW:sdg Enclosure cc.'Dr. J. Nelson Grace (NRC RII)

Mr. B. Buckley (NRR)

Mr. G. Maxwell (NRC SHNPP)

MEM/HO-8704290/PAGE 1/OS1