ML20046B129

LER 93-012-00:on 930614,lost Spent Fuel Pool Cooling for Approx 13 Hours Due to Insufficient Control Board Awareness. Design Change to Install Annunciator in Control Room to Inform of Loss of Spent Fuel cooling.W/930729 Ltr

ML20046B129
Person / Time
Site:	South Texas
Issue date:	07/29/1993
From:	Groth J, Pinzon J HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-012-01, LER-93-12-1, ST-HL-AE-4524, NUDOCS 9308030143
Download: ML20046B129 (7)

Text

.

e The IJght cg,o mp a ny South Texas Project Electric Generating

g p, Station P. O. Box 289 Wadsworth, Texas 77483 July 29, 1993 ST-HL-AE-4524 File No.

G26 10CFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Unit 2 Docket No. STN 50-499 Voluntary Licensee Event Report 93-012 Loss of Spent Fuel Pool Cooling for Approximately 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> Pursuant to 10CFR50.73, Houston Lighting & Power (HL&P) submits the attached Unit 2 Voluntary Licensee Event Report 93-012 ,

regarding a loss of spent fuel pool cooling for approximately 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />. This event did not have an adverse effect on the health and safety of the public. 1 If you should have any questions on this matter, please contact Mr. J. M. Pinzon at (512) 972-8027 (

or me at (512) 972-8664.

(3 F bel ice President, Nuclear Generation jmw/pa

Attachment:

Voluntary LER 93-012 (South Texas, Unit 2)

/

020028 LER-93\t93012R0.u2 7 y( '

/

Project Manager on Behalf of the Participants in .he South Texas Project l

&B0301439307g9 m v g ADDCK 05000499 .

PDR h.I:

.I

4 ST-HL-AE-4524 liouston Lighting & Power Company File No.: G26 South Texas Project Electric Generating Station Page 2 c:

i Regional Administrator, Region IV Rufus S. Scott i

~

Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 400 Houston Lighting & Power Company Arlington, TX 76011 P. O. Box 61867 Houston, TX 77208 Lawrence E. Kokajko Project Manager Institute of Nuclear Power U.S. Nuclear Regulatory Commission Operations - Records Center Washington, DC 20555 13H15 700 Galleria Parkway Atlanta, GA i 30339-5957

_ David P. Loveless l Senior Resident Inspector Dr. Joseph M. Hendrie c/o U. S. Nuclear Regulatory 50 Bellport Lane  :

Commission Bellport, NY 11713  ;

P. O. Box 910 Bay City, TX 77414 D. K. Lacker .

Bureau of Radiation Control J. R. Newman, Esquire Texas Department of Health -

Newman & Holtzinger, P.C., STE 1000 1100 West 49th Street i 1615 L Street, N.W. Austin, TX 78756-3189 Washington, DC 20036 U.S. Nuclear Regulatory Comm. l D. E. Ward /T. M. Puckett Attn: Document Control Desk  !

Central Power and Light Company Washington, D.C. 20555 P. Os Box 2121  ;

Corpus Christi, TX 78403 J. C. Lanier/M. B. Lee City of Austin Electric Utility Department 721 Barten Springs Road Austin, TX 78704 K. J. Fiedler/M. T. Hardt City Public Service P. O. Box 1771 San Antonio, TX 78296 LER-93\t93012RO.U2

~NRC FORQ 366 U.S. C2iCLEAR RECUULTOY CIMMISSIO APPROVED BY OMB C3. 3150-0104 ,

(5-92) ' EXPIRES 5/31/95 j ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH LICENBEE EVENT REPORT (LER) $,,I" c"Ngy73 o

I b Cil gcYgolw R

sUR ENS1 TE b THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, (See reverse for required number of digits / characters for each block) WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MAkAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY EAME (1) DOCKET NUMBER (2) PAGE (3)

South Texas Unit 2 05000 499 1 OF 5 TITtE (4) Loss of Spent Fuel Cooling for Approximately 13 Hours EVE NT DATE (5) LER MlMBER (6) REPORT DATE (7) OTHER F ACILITIES INVOLVED (8)

MONTH DAY YEAR MONTH DAY YEAR YEAR NUMBER NUMBER 05000 AC IU MM NE B 06 14 93 93 -- 012 -- 00 07 29 93 g OPERATING MODE (9) gjg THIS RNT IS WIM NH TO THE NIRNNM W 10 CFR h (Check W or w e) OD 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)

POWER LEVEL (10) 0 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) X OTHER 20.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(viii)(A) (SPecify in I

20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) 20.405(n)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x) 3664) Voluntery t 1CENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (include Area Code)

Jairo Pinzon - Senior Engineer (512) 972 - 8027 COMPLETE ONE LINE FOR EACH CIMPONENT f Allure DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM C04?ONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER p g T S SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED YES SUEiMISSION No

(!? yes, complete EXPECTED SUBMIS$10N DATE). x DATE (15)

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

On June 13, 1993, Unit 2 was in a refueling outage with the core unloaded and stored in the spent fuel pool. At 1420 hours0.0164 days <br />0.394 hours <br />0.00235 weeks <br />5.4031e-4 months <br />, the 1E distribution panel DP001 was transferred from its main to alternate power supply to support maintenance activities. This transfer required DP001 to be momentarily de-energized. When DP001 was re-energized, the Component Cooling Water (CCW) common header isolation relay for low CCW surge tank level responded before the CCW surge tank level switch. This resulted in a signal that isolated CCW to the spent fuel pool heat exchangers. Due to insufficient control board awareness by operations and the failure of an operator to notice changes in CCW flow induced noise and vibration during local operator rounds, this condition was not discovered until 0315 hours0.00365 days <br />0.0875 hours <br />5.208333e-4 weeks <br />1.198575e-4 months <br /> on June 14, 1993. Fuel pool temperature increased from 99 degrees F to 118 degrees F. Once discovered, operators restored cooling to the spent fuel pool. Efforts are being initiated to enhance operator control board awareness and awareness during normal operator rounds. HL&P is evaluating a design change to install an annunciator for loss of fuel pool cooling.

Based on the fuel pool temperature remaining below the FSAR assumed maximum and other independent methods for fuel pool cooling being available, there were no adverse safety consequences from this event.

NRC FORM 366 (5-92)

LE R-93\t 93012RO.U2

E FORM 3664 U.S. CJCLEAR RE(XQ.ATORY COMISSION APPROVED BY OMB N3. 3150-0104 (5-92) EXP!RES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB m4), U.S. NUCLEAR REGULATORY COMMISSION, TEXT CONTINUATION WASHINGTON, DC 20555-0001 AND TO THE PAPERWORK REDUCTION PROJECT (31$0-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKFT EMBER (2) LER RMRER (6) PAGE (3)

SEQUENTIAL REVISION YEAR South Texas, Unit 2 05000 499 2 OF 5 93 -- 012 -- 00 TEXT (If more srece is reauired. use a&litional copies of Nec Form 366A) (17)

DESCRIPTION OF EVENT On June 13, 1993, Unit 2 was in a refueling outage with the core unloaded and stored in the spent fuel pool. Preventative maintenance was scheduled ,

to be performed on the normal power supply to 1E distribution panel DP001.  !

An equipment clearance order was prepared for the normal power supply and a ,

pre-job briefing was ccnducted in preparation for realigning DP001 to its alternate power supply. Aligning DP001 to its alternate supply required a dead bus transfer, momentarily de-energizing the panel. The dayshift operating crew discussed the expected conditions that would occur during this evolution. They reviewed the procedure for loss of this panel and the ,

various loads that would be affected during the transfer. The transfer was  :

coordinated between the transfer location and the control room. Control room personnel evaluated the alarms that occurred during the transfer and verified that they were not associated with any valid off-normal condition.

i During the transfer, at approximately 1420 hours0.0164 days <br />0.394 hours <br />0.00235 weeks <br />5.4031e-4 months <br />, Train A Component Cooling l' Water (CCW) common header inlet and outlet isolation valves MOV-0052 and MOV-0316 stroked closed. This isolated CCW flow to the spent fuel pool heat exchangers.

HL&P has determined that the common header isolation valves closed due to the CCW common header isolation relay for low CCW surge tank level ,

responding before the CCW surge tank level switch when DP001 was re-energized. DP001 supplies power to both the CCW surge tank level switch and the common header isolation relay. When the DP001 dead bus transfer occurred, the CCW surge tank level switch was de-energized and failed low.

Under normal conditions, this would produce a low level signal, initiating a common header isolation. However, during the dead bus transfer, the common header isolation relay was also de-energized and could not initiate the  ;

header isolation. When DP001 was re-energized, power was restored to both the level switch and the header isolation relay. The header isolation relay responded first and caused the common header inlet and outlet valves to 1 isolate. l While there were no control room annunciations for the isolation of CCW flow to the common header, there were both control room and non-control room indications that CCW flow had been isolated. The control room boards showed CCW flow isolation through the closed valves' position indication lights, the CCW flow meter, and the CCW 2A heat exchanger outlet pressure indicator.

When MOV-0052 and MOV-0312 stroked closed, their position indication lights changed color to indicate that the valves had closed. Prior to the CCW I

isolation, the CCW flow meter indicated a flow rate of approximately 12,000 gpm. After the isolation the CCW flow meter indicated an unusually low flow rate of approximately 5,500 gpm. During the event, the CCW 2A heat exchanger outlet pressure indicator was indicating 115 psi.

l LER 93\L93012RD.U2

l NRC F(DM 366A U.S. HUCLEAR REGJLATORY CDDilSSl(21 API M BY OMB No. 3150-0104 (5-92) D PIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. )

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) INroRMATIow AND RECORDS MANAGEMENT BRANCH (MNBB TEXT CONTINUATION 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001 AND 10 THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF ,

MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

]

FACILITY NAME (1) DOCKET MlMBER (?) LER NUMBER (61 PAE (3)

SEQUENTIAL REVISION YEAR South Texas, Unit 2 05000 499 3 OF 5 93 -- 012 -- 00 TEXT fif more space is reavired, use additional copies of WRC Form 3664) (17)

DESCRIPTION OF EVENT (Cont'd)

The normal operating pressure range indicated by the CCW heat exchanger outlet pressure indicator is 100 - 105 psi. In addition to the control room indications of isolated CCW flow, there was also a distinguishable change in the CCW flow induced noise and vibration levels in the area of the inservice l spent fuel pool heat exchanger.

During and following the transfer of DP001 the control room operators failed to detect that valves MOV-0052 and MOV-0312 had stroked closed.

At approximately 1710 hours0.0198 days <br />0.475 hours <br />0.00283 weeks <br />6.50655e-4 months <br />, a reactor plant operator traveled through the area of the spent fuel pool heat exchangers as part of normal operator rounds. The reactor plant operator failed to notice changes in flow induced noise and vibration due to the isolation of the CCW flow to the inservice spent fuel pool heat exchanger.

At approximately 1830 hours0.0212 days <br />0.508 hours <br />0.00303 weeks <br />6.96315e-4 months <br />, the dayshift crew was relieved by the nightshift crew. During turnover, the DP001 transfer evolution was discussed. Board walkdowns with the oncoming crew failed to identify that CCW flow to the common header had been isolated.

At 0315 hours0.00365 days <br />0.0875 hours <br />5.208333e-4 weeks <br />1.198575e-4 months <br /> on June 14, 1993, the reactor plant operator performing rounds in the Mechanical Auxiliary Building identified that the CCW pump discharge pressure was high. He notified the control room. Control room personnel reviewed the system alignment and discovered that MOV-0052 and MOV-0316 were closed. These valves were opened and cooling was restored to the spent fuel pool.

l The reactor plant operator was dispatched to the spent fuel pool to determine its temperature. At 0350 hours0.00405 days <br />0.0972 hours <br />5.787037e-4 weeks <br />1.33175e-4 months <br />, he reported the spent fuel pool temperature was 118 degrees F. The spent fuel pool temperature remained below the Updated Final Safety Analysis Report (UFSAR) assumed maximum of 145.7 degrees F throughout this event. Prior to this event, the spent fuel pool temperature had been 99 degrees F. By 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> the temperature had l l

decreased to 117 degrees F.

l l

i LER-93\L9301?RO.U2 ,

I

NRC FORM 366A U.S. NUCLEAR REGULATORY CO MISSION APPRO KD BY ODS No. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THis INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB TEXT CONTINUATION 771'), u.s. NUCLEAR REGULATORY COMMIS$10N, WASHlWGTON, DC 20555-0001 AND TO THE PAPERWORK REDUCTION PROJECT (31$0-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NLMBER (2) LER NLMBER (6) PAGE (3)

YEAR SEQUENTIAL REVISION South Texas, Unit 2 """ " ""

05000 499 4 OF 5 93 -- 012 -- 00 TDIT (If more spece is reouired, use additionet copies of NRC Form 366A) (17)

CAUSE OF THE EVENT Investigation determined that this event was due to the following causes:

1) The 13 hour1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> delay in identification of the loss of spent fuel pool cooling was a result of insufficient control board awareness.

Operators failed to notice the isolation valves' position indication lights had switched from open to closed, the CCW flow meter was indicating an unusually low CCW flow rate, and the CCW 2A heat exchanger outlet pressure indicator was displaying a higher than normal operating pressure. Additionally, the operators failed to identify this problem during the shift change control board walkdown, and during normal control board reviews.

2) The reactor plant operator's failure to notice the changes in flow induced noise and vibration during normal rounds in the afternoon was a contributing factor to the failure to identify the loss of spent fuel pool cooling for 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />.

3) The Train A CCW common header isolation valves closed due to the common header isolation relay responding before the level switch in the CCW surge tank level circuit when DP001 was re-energized.

ANALYSIS OF EVENT With the core offloaded, there are no Technical Specification requirements for operability of the CCW system. The only applicable limit in the Accident Analysis is that the spent fuel pool temperature be maintained at no greater than 145.7 degrees F. Fuel pool temperature was less than 145.7 degrees F at all times during this event. There were two trains of CCW available throughout the event and capable of supplying cooling to the spent fuel pool. Additionally, station procedures provide the operators with specific direction regarding alternate means of spent fuel cooling in the event that all three trains of CCW were to become unavailable. Based on the spent fuel pool temperature remaining within safety analysis limits and the several available means for providing cooling, it is concluded that there were no adverse safety consequences from this event.

LER-93\L9301?RD.U2 .

mam:=sr NRC FORM 366A U.S. NUCLEAR REGUULTORY CDMISSION APPROVED BY OMS No. 3150-0104 (5 92) EXPICES 5/31/95 ESilMATIO BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS RECARDING BURDEN ESTIMATE TO THE LICENBEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MWBB TEXT CONTINUATION 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001 AND TO THE PAPERWORK j REDUCTION PROJECT (3150-0104), OFFICE OF

, l MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY MAME (1) DOCKET NLMBER (2) % LER WlMBER (6) PAGE (3)

, ag SEQUENTIAL REVISION South Texas, Unit 2 05000 499 5 OF 5 93 -- 012 -- 00 TEXT (If more space is reautred. use additional ecoies of NRC Form 366A) (17)

CORRECTIVE ACTIONS

1) Emphasis is being placed on the need for enhanced control board awareness. This emphasis has been covered in meetings with all active shift supervisors. In addition, simulator scenarios that enhance operator auareness of mispositioned components during turnover and normal control board walkdowns were being implemented. These simulator scenarios will be incorporated in the operator training program by September 15, 1993.

2) Preparation of a design change to install an annunciator in the control room to alert the operators of a loss of spent fuel cooling due to loss of CCW or spent fuel pool cooling flow has been approved.

3) The proper performance of operator rounds, including awareness of plant conditions through sensory perception, is being emphasized. This includes being aware of such things as changes in noise or vibration levels that result from changes in the operating condition. This issue has been covered in meetings with all active RPOs.

4) HL&P procedures covering loss of applicable class 1-E AC distribution panels have been revised to alert operators to the potential for valve movement when these panels are re-energized.

5) Management has re-emphasized operational priorities and sensitivity to events to operations personnel.

Additional Information There have been no previous similar South Texas Project events reported to the NRC regarding a loss of cooling to the spent fuel pool.

LER-93\L93012RD.U2