ML18096B362

LER 93-007-00:on 930225,initial Investigation Indicated High Resistance Readings at Coil Stacks Resulting to TS 3.0.3 Entry.Caused by Sys Design.Review of Event in Progress & C/A Will Be Implemented Based on results.W/930325 Ltr

ML18096B362
Person / Time
Site:	Salem
Issue date:	03/25/1993
From:	POLLACK M J, VONDRA C A Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-007, LER-93-7, NUDOCS 9303310325
Download: ML18096B362 (5)

Text

e Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station 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 LICENSEE EVENT REPORT 93-007-00 March 25, 1993 This Licensee Event requirements of the 50. 73 (a) (2) (i) (B). thirty (30) days of Report is being submitted pursuant to the Code of Federal Regulations lOCFR MJPJ:pc Distribution 9303310325 PDR ADOCK s 010034 930325 05000272 PDR Thr. power is in \h'.)Uf

.. This report is required to be issued within event discovery.

Sincerely yours, c. A Vondra General Manager -Salem Operations 95*2189 REV 7-92 NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150*0104 16-89) EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LERI INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH IP-530). U.S. NUCLEAR REGULATORY COMMISSION.

WASHINGTON.

DC 20555. AND TO THE PAPERWORK REDUCTION PROJECT 13150-0104).

OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503. FACILITY NAME 11) I DOCKET NUMBER (2) I PAGE 13) . Salem Generating Station -Unit 1 015101010121712 1!0F0!4 TITLE 141 2 Tech Spec 3.0.3 Entries; More*Than 1 Analog Rod Position Indicator Per Bank Inop. EVENT DATE (5) LEA NUMBER (6) REPORT DATE 171 OTHER FACILITIES INVOLVED (Bl MONTH DAY YEAR YEAR }{ SEOUENT!l..L

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,.,. I I I I SUPPLEMENTAL REPORT EXPECTED 1141 MONTH DAY YEAR EXPECTED SUBMISSION J YES (If yes. comp/ere EXPECTED SUBMISSION DA TEI DATE 1151 I I I ABSTRACT (Limit to 1400 SP8C6S, i.e., approximately fifteen single-space rvpewrirren lines) (161 On 2/24/93, at 2024 hours, Control Rod 1D4 Analog Rod Position Indication (ARPI) was discovered indicating greater than a+/- 12 step deviation from its group demand counter. Technical Specification (TS) 3.1.3.2.la Action II a II was entered. Initial investigation indicated high resistance readings at the coil stacks. On 2/25/93, at 1514 hours and on 2/26/93, at 2126 hours, the ARPI for Control Rod 2Dl (both times) was found indicating greater than a+/- 12 step deviation from its group demand counter. Since ARPI indication for Control Rod 1D4 had not been corrected from 2/24/93, TS 3.0.3 was entered each time. Flux traces verified that Control Rods 2Dl and 1D4 were correctly positioned. When more than one ARPI per bank is inoperable, TS 3.1.3.2.la is exceeded; therefore, TS 3.0.3 applies. On 2/25/93, at 1522 hours, TS 3.0.3 was exited after the 2Dl control rod position indication was corrected. On 2/26/93, at 2212 hours, TS 3.0.3 was exited after the 2Dl control rod position indication returned to within + 12 steps of the group demand position. The root cause of these events is system design. The ARPI system electronics settings, associated with the coil stack, will have some drift due to the stacks' susceptibility to temperature change. Investigation of the Control Rod 1D4 coil stack concern revealed that the high resistance reading was not correct. The high reading was due to AC induced noise from other coil stacks in the vicinity. On 2/27/93, after adjustment of the 1D4 control rod position indication, TS 3.1.3.2.la Action II a II was exited. NRC Form 366 16-89) ' I *

• LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 1 DOCKET NUMBER 5000272 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse -Pressurized Water Reactor LER NUMBER 93-007-00 PAGE 2 of 4 Energy Industry Identification System (EIIS) codes are identified in the text as {xx} IDENTIFICATION OF OCCURRENCE: 2 Technical Specification 3.0.3 entries; more than one analog rod position indicator per bank inoperable Event Dates: 2/25/93 and 2/26/93 Report Date: 3/25/93 This report was initiated by Incident Report No. 93-162, 93-164 and 93-169. CONDITIONS PRIOR TO OCCURRENCE: 2/25/93: 2/26/93: Mode 1 Mode 1 Reactor Power 93% -Unit Load 1037 MWe Re.actor Power 95% -Unit Load 1067 MWe On 2/23/93 a unit restart commenced. As of 2/25/93, at 0000 hours, reactor power was at 85% with control rods in manual. DESCRIPTION OF OCCURRENCE: On February 24, 1993, at 2024 hours, the Control Room Operator identified that Analog Rod Position Indication (ARPI) for Control Rod 1D4 was indicating greater than a +/- 12 step deviation from its group demand counter. Technical Specification 3.1.3.2.la Action "a" was entered. Initial investigation by Maintenance-I&C indicated high resistance readings at both the primary and secondary coil stacks. A lead was thought to have failed. Therefore, the rod was not recalibrated. On February 25, 1993, at 1514 hours and on February 26, 1993, at 2126 hours, the Control Room Operator identified that ARPI for Control Rod 2Dl (both times) was indicating greater than a +/- 12 step deviation from its group demand counter. Since ARPI indication for Control Rod 1D4 had not been returned to service, from February 24, 1993, Technical Specification 3.0.3 was entered each time. Reactor Engineering conducted flux traces after each false indication verifying that Control Rod 2Dl was correctly positioned Control Rod 1D4 position was being verified every 8 hours per Technical Specification 3.1.3.2.la Action "a". Technical Specification 3.1.3.2.1 addresses the operability requirement of the "Reactivity Control System's" {AA} position LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 1 DESCRIPTION OF OCCURRENCE: DOCKET NUMBER 5000272 (cont'd) LER NUMBER 93-007-00 PAGE 3 of 4 indicating systems. The indicators are determined operable by* verifying that the rod position indication system agrees within twelve {12) steps of the group demand counters. When more than one ARPI per bank is inoperable, Technical Specification 3.1.3.2.1 Limiting Condition For Operation is exceeded. Therefore, actions associated with Technical Specification

3.0.3 apply

(and was entered on February 25, 1993 and February 26, 1993, respectively). Technical Specification

3.0.3 states

"When a Limiting Condition for Operation is not met except as provided in associated ACTION requirements, within one hour action shall be initiated to place the unit in a MODE in which the specification does not apply by placing it, as applicable, in: 1. At least HOT STANDBY within the next 6 hours, 2. At least HOT SHUTDOWN within the following 6 hours, and 3. At least COLD SHUTDOWN within the subsequent 24 hours. Where corrective measures are completed that permit operation under the ACTION requirements, the ACTION may be taken in accordance with the* specified time limits as measured from the time of failure to meet the Limiting Condition of Operation. Exceptions to these requirements are stated in the individual specifications." On February 25, 1993, at 1522 hours, Technical Specification 3.0.3 was exited after the 2Dl control rod position indication was corrected by adjustment of the signal conditioning module. On February 26, 1993, at 2212 hours, Technical Specification 3.0.3 was exited after the 2Dl control rod position indication returned to within +/- 12 steps of the group demand position and Reactor Engineering conducted flux traces to verify the position of the rod. During both events, Technical Specification Action 3.1.3.2.la.a remained in affect due to the 1D4 control rod position indication concern. APPARENT CAUSE OF OCCURRENCE: The root cause of the ARPis having greater than +/- 12 step deviation from their group demand counter, for the two (2) control rods, is attributed to system design. The ARPI system electronics settings, associated with the Westinghouse Signal Condition Module and Control Rod coil stack, will have some drift. This is due to the analog coil stacks' susceptibility to temperature changes. The reactor had been in the process of power ascension to full power operation during the course of these two (2) events. A contributing factor to this event was inadequate understanding of induced AC noise from coil stacks and the effect on a Digital '

• LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 1 APPARENT CAUSE OF OCCURRENCE:

DOCKET NUMBER 5000272 (cont'd) LER NUMBER 93-007-00 PAGE 4 of 4 Multimeter (DMM). Subsequent investigation of the February 24, 1993 indication of the 1D4 Control Rod high resistance reading at both the primary and secondary coils was conducted. It was determined that the high resistance readings were not correct. A DMM was used to obtain the readings. With the DMM in the automatic mode, the initial meter reading indicated resistance in the Kohm range. However, it has since been determined that this reading was high due to AC induced noise from other coil stacks in the vicinity. Subsequently, the readings were retaken after allowing time for the resistance reading to stabilize (approximately one minute) . High resistance was not observed. On February 27, 1993, after adjustment of the control rod position indication, Technical Specification 3.1.3.2.la Action "a" was exited. ANALYSIS OF OCCURRENCE: Operability of the ARPis is required to determine control rod position. This ensures compliance with control rod alignment and insertion limits assumed in the accident analyses. Investigation of this event showed that actual rod positions (per group demand) were correct, with only the indication being wrong. However, had a control rod actually been misaligned, the appropriate Technical Specification Action Statement requirements would have been met. The false rod positioning indication did not affect the health or safety of the public. However, since Technical Specification 3.0.3 was entered, this event is reportable to the Nuclear Regulatory Commission in accordance with Code of Federal Regulations lOCFR 50. 73 (a) (2) (i) (B). CORRECTIVE ACTION: System Engineering is continuing its review of this event and similar prior events. Additional corrective action will be implemented based on results of this review. The concerns associated with induced AC noise from coil stacks on DMMs has been reviewed with applicable Maintenance Department personnel. It will be reviewed by the Nuclear Training Center for inclusion in applicable training programs. MJP:pc SORC Mtg. 93-026}}