ML18153C737

Special Rept:On 910815 & 24,quadrant-to-average Power Tilt Exceeded 2% for More than 24 H.Caused by Blown Fuse & Dropped Rod Runback.Cable W/Insulation Damage & Rod Control Cabinet Repaired

ML18153C737
Person / Time
Site:	Surry
Issue date:	09/13/1991
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
91-532, NUDOCS 9109190223
Download: ML18153C737 (4)

Text

ACCpLERATED iSTRIBUTION DEMOTTIQN,Ji¥STEM .

REGULATORY INFORMATION ~ISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9109190223 DOC.DATE: 91/09/13 NOTARIZED: NO DOCKET#

FACIL:50-281 Surry Power Station, Unit 2, Vi:rg.inia Electric.& Powe 05000281 AUTH.NAME AUTHOR AFFILIATION .

STEWART,W.L. Virginia Power (Virginia Elect~ic & Power Co.)

• . RECIP. NAME RECIPIENT AFFILIATION Document Control_Branch (Document Control.Desk)

SUBJECT:

Special*rept:on 910815 & 24,quadrant-to-a:verage power tilt exceeded 2% for more than 24 h.Caused by blown fuse & .

dropped rod runback.Cable w/insulation damage & rod control cabinet repaired. *

• DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR / ENCL_, SIZE:_._3'-----

TITLE: 5 o. 7 3/ 5 o . 9 Licensee Event Report ( LER) , Incident Rpt, . etc. .

NOTES:lcy NMSS/IMSB/PM. 05000281 RECIPIENT COPIES RECIPIENT COPIES

• ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD. 1 1 BUCKLEY,B 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 .AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 *2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 . NRR/DLPQ/LHFBlO 1 1 NRR/DLPQ/LPEBlO 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPBll 2 2 NRR/DST/SELB SD 1 1 NRR/DST/SICB8H3 . 1 1 NRR:~~~B:8:llb 1 1 NRR/DST/SRXB .BE 1 1 REG,dr* , 02 1 1 RES/DSIR/EIB 1 1 RGif-* *---~-*~FJ:-1:iE~*'o*i- 1 1 EXTERNAL: EG&G BRYCE,J.H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 NOTES: 1 1 NOTE TO ALL "RIDS" RECIPIET'\TS:

PLEASE HELP us T9 REDUCE \\"ASTE! CONTACT THE DOCUMP<T cm,ffROL DESK, R00'.\1 PJ-3, (EXT. 20079) TO ELI'.\11'.'i:\TE YOUR NAME FROJ\1 DISTRIBUTION LISTS FOR DOCUi\1ENTS YOU DQ"-:'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 34

• ENCL 34 .

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e e VIRGINIA ELECTRIC AND POWER COMPANY b,

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RICHMOND, VIRGINIA 23261 September 13, 1991 United States Nuclear Regulatory Commission Serial No.91-532 Attention: Document Control Desk NO/RJS R1 Washington, D. C. 20555 Docket No. 50-281 License No. DPR.:37 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 2

• SPECIAL REPORT -

QUADRANT TO AVERAGE POWER TILT EXCEEDS 2.0% FOR GREATER THAN 24 HOURS Surry Technical Specification 3.12.8.7.a requires an evaluation be performed and a special report be issued to the Nuclear Regulatory Commission under certain conditions when the quadrant to average power tilt exceeds 2% for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. On August 15, 1991 and August 24, 1991, the Surry Unit 2 quadrant to average power tilt exceeded 2% for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. A description of the circumstances surrounding these events are provided in the att.achment to this letter.

This report has been reviewed and approved by the Station Nuclear Safety and

• Operating Committee.

Should you have any questions or require additional information, please contact us.

W. L. St art Senior Vice President - Nuclear Attachment - Special Report for Quandrant to Average Power Tilt Exceeding 2% for Greater than 24 Hours cc: U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station ifY\

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ATTACHMENT SPECIAL -REPORT FOR QUADRANT TO* AVERAGE POWER TILT EXCEEDING 2%

FOR GREATER THAN 24 HOURS

II.II' on August 14, 1991 at 1753 hours0.0203 days <br />0.487 hours <br />0.0029 weeks <br />6.670165e-4 months <br /> with Unit 2 at 100% reactor power (795 MW),

control rod D-4 in control bank C dropped into the core with blown fuse indications. An

• individual Rod Position Indication (IRPI) dropped rod runback occurred and the unit was stabilized at 54% power (420 MW). Applicable Abnormal Operating Procedures were implemented and technical specification requirements were reviewed. Reactor power was verified to be less than 75% and initial Quadrant Power Tilt (OPT) from the excore detectors was determined to be 11.6% at 1825 hours0.0211 days <br />0.507 hours <br />0.00302 weeks <br />6.944125e-4 months <br />. A shutdown margin calculation was also completed and verified to be satisfactory at 1828 hours0.0212 days <br />0.508 hours <br />0.00302 weeks <br />6.95554e-4 months <br />.

Following the determination that OPT was greater than 2.%, at 2059 hours0.0238 days <br />0.572 hours <br />0.0034 weeks <br />7.834495e-4 months <br /> the High Flux Trip Setpoints were reduced to 72% and rod stop setpoints were reduced to 68%

to allow power operation with control rod D-4 inoperable and fully inserted and with OPT greater than 2%. This action was taken to comply with Technical Specification 3.12.8.6.b which requires the High Flux Trip Setpoint to be reduced at least 2% for every 1% of OPT when hot channel factors are not determined within two hours.

Following discussions held with the nuclear steam supply system vendor, Westinghouse, the rod control cabinet was inspected and tested and the rod drive cables were meggered satisfactorily. A cable (with suspected insulation damage) in the rod control cabinet was repaired. The fuses were replaced and control rod D-4 retrieval was performed in accordance with AP-1.01. The rod was fully withdrawn and rE3actor power was raised to 100% at a ramp rate limited to 3% per hour for reactor power levels greater than 68%. This limitation oh ramp rate was implemented in accordance_ with Westinghouse fuel conditioning guidelines.

on August ~3. 1991 at 0435 hours0.00503 days <br />0.121 hours <br />7.19246e-4 weeks <br />1.655175e-4 months <br /> with Unit 2 at 80% reactor power (625 MW), control rod D-4 in control bank C again dropped into the core. A second IRPI dropped rod runback occurred and the unit was stabilized at 50% power (370 MW). Applicable Abnormal Operating Procedures were implemented and actions similar to the first event were taken. Reactor power was verified to be less than 75% and a shutdown margin calculation was completed and verified to be satisfactory at 0503 hours0.00582 days <br />0.14 hours <br />8.316799e-4 weeks <br />1.913915e-4 months <br />. The High Flux Trip Setpoints were reduced to 72% and the rod stop setpoints were reduced to 68% at 0817 hours0.00946 days <br />0.227 hours <br />0.00135 weeks <br />3.108685e-4 months <br />. Initial Quadrant Power Tilt (OPT) from the excore detectors was determined to be-14.5% at 1124 hours0.013 days <br />0.312 hours <br />0.00186 weeks <br />4.27682e-4 months <br />. Reactor operation continued at reduced power, in accordance with analyses performed, until September 7 when Unit 2 was shutdown to troubleshoot and make repairs to control rod D-4.

The core asymmetry due to operation with control rod D-4 inserted, coupled with the xenon transients and changes in Tave associated with the dropped rod events, resulted in the observed excore tilts. For ea*ch of these events, manual OPT calculations were performed at least every two hours to monitor and trend the tilts.

Following each event, preparations were also initiated to reduce Overpower ~T and Overtemperature ~T trip setpoints. These preparations were made to ensure the Technical Specification requirement to reduce these setpoints, if the excore tilt exceeded 2% for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and either the hot channel factors had not been determined or had been exceeded, could be expeditiously implemented. Prior to OPT exceeding 2% (but less than 10%) for greater than a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period, the nuclear engineering staff concluded from full core flux maps taken at 1124 on August 15 (D-4 inserted), 0248 on August 16 (D-4 withdrawn), at 1123 on August 17 (D-4 withdrawn), and at 1405 on August 23 (D-4 inserted) that the limits placed on core peal*dng factors by TS 3.12.B.1 were not exceeded during these events. Since the core peaking factors remained within limits, it was not necessary to reduce the Overpower ~T and Overtemperature ~T trip setpoints during either event.