ML18037A897

LER 94-004-00:on 940415,Unit 2 Received a Full Scram from Full Power Due to RPS Trip Signal Generated by Low Scram Pilot Air Header Pressure Signal.Failed Module in Temp Detection loop.W/940513 Ltr

ML18037A897
Person / Time
Site:	Browns Ferry
Issue date:	05/13/1994
From:	Austin S, Machon R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-94-004-02, LER-94-4-2, NUDOCS 9405240094
Download: ML18037A897 (22)

Text

ACCELERATED DISTRIBUTION DEMONSTRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9405240094 DOC.DATE: 94/05/13 NOTARIZED: NO DOCKET FACIL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 AUTH. NAME AUTHOR AFFILIATION AUSTIN,S. Tennessee Valley Authority MACHON,R.D. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 94-004-00:on 940415,Unit 2 received a full scram from full pilotpower due to RPS trip signal generated by low scram air header pressure signal. Failed module in temp D detection loop.W/940513 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-4-PD 1 1 TRIMBLE,D 1 1 D INTERNAL: ACRS 1 1 AEOD/DOA 1 1 AEOD/DS P/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/ DE/EE LB 1 1 N RR/ DE/EME B 1 1 NRR/DORS/OEAB 1 1 NRR/DRCH/HHFB 1 1 NRR/ DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRI L/RPEB 1 1 NRR/DRSS/PRPB 2 2 NRR/DSSA/S PLB 1 1 NRR/DSSA/SRXB 1 1 1 1 RES/DSIR/EIB 1 1 1 1 EXTERNAL: EG&G BRYCE,J.H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POOREiW 1 1 NUDOCS FULL TXT 1 1 D

D D

NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOiVI P 1-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROiMi DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

'FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 28 ENCL 28

1 r

Tertrtessee Vatey Authority, post Offic Box 2000. Decatur. Aaoama 35609 2000 R. D..(Rick) Machon Vce Prestdertt, Browrts Ferry Huctear Ptartt NY 13 199<

U.S. Nuclear Regulatory Commission 10 CFR 50.73 ATTN: Document Control Desk Washington, D.C 20555

Dear Sir:

BROWNS FERRY NUCLEAR PLANT (BFN) UNITS 1 p 2 g AND 3 DOCKET NOS ~ , 50-259I 50-260~ AND 296 - FACILITY OPERATING LICENSE DPR-33~ 52~ AND 68 LICENSEE EVENT REPORT 50-260/94004 The enclosed report provides details concerning a Unit 2 scram from 100 percent power during a planned maintenance activity on one of the Scram Pilot Air Header pressure regulators. The cause of the event was attributed to inappropriate personnel action when those involved deviated from the work instruction during isolation of the pressure regulator.

As part of the Scram Frequency Reduction Program, TVA has proposed that the Scram Pilot Air Header low pressure scram function be eliminated. To date, a proposed technical specification (TS) change that will remove the scram discharge volume air header scram function has been submitted to NRC. Accordingly, implementation of this TS change will eliminate the risk .of a unit scram*during this maintenance activity.

Additionally, the report provides details on a manual isolation of the High Pressure Coolant. Injection (HPCI) during the unit scram.

This report is submitted in accordance with 10 CFR 50.73(a)(2)(iv), as any event or condition that resulted in manual or automatic actuation of any engineered safety feature including the reactor, protection system.

Additionally, due to the isolation of HPCI, which is a single train safety system, this event is reportable in accordance with 10 CFR 50.73(a)(2)(v)(A). As any event or condition lob

'tt405240094 9405l3 PDR ADOCK 05000260 S PDR

II U. S.- Nuclear Regulatory Commission 14AV 13 1994 that alone could have prevented the fulfillment of the safety function of structures of systems that are needed to shutdown the reactor and maintain it in a safe shutdown condition.

If you have any question Salas at (205) 729-2636.

or comments please telephone Pedro Sincerely, R. D. M hon Site Vice President cc (Enclosure):

INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 Paul Krippner American Nuclear Insurers Town Center, Suite 300S 29 South Main Street West Hartford, Connecticut 06107 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12., Box 637 Athens, Alabama 35611 Regional Administrator U.S. Nuclear Regulatory Commission Region II Marietta Street, NW, .Suite 2900 101 Atlanta, Georgia 30323 Mr. J. F. Williams, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. D. C. Trimble, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852

NRC FORM 366 U.S. NUCLEAR REGULATORY COHHISSION APPROVED BY (NB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIHATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORHATION COLLECTION REOUEST: 50 ' HRS ~

LICENSEE EVENT REPORT (LER) FORWARD COHMENTS REGARDING BURDEN ESTIHATE TO THE INFORMATION AND RECORDS MANAGEHEHT BRANCH (HNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION/

for required of digits/characters for each block) WASHINGTON, DC 20555-0001 AND TO THE PAPERWORK (See reverse number REDUCTION PROJECT (3140-0104), OFFICE OF MANAGEMENT AND BUDGET WASHINGTON DC 20503.

FACILITY NAHE (1) DOCKET NINBER (2) PAGE (3)

Browns Ferry Nuclear Plant (BFN) Unit 2 05000260 1 OF 8 TITI.E (4)Unit 2 Scram From Full Power During Planned Maintenance Activity Due to Inappropriate Personnel Action EVENT DATE 5 LER NNIBER 6 REPORT DATE 7 OTHER FACILITIES INVOLVED 8 SEOUENTIAL REVISION FACILITY NAHE DOCKET NUHBER MONTH DAY YEAR YEAR HONTH DAY YEAR NA NUHBER NUHBER FACILITY NAHE DOCKET NUHBER 04 15 94 94 004 00 05 13 94 NA OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REOUIREHENTS OF 10 CFR  : 'heck one or more 11 MODE (9) N 20.402(b) 20.405(c) X'0.73(a)(2)(iv) 73.71(b) 20.405(a)(1)(i) 50.36(c)(1) X 50.73(a)(2)(v) 73.71(c)

POWER LEVEL (10) 100 20.405(s)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER 20.405(a)('l)(iii) 50.73(a)(2)(i) 50.73(s)(2)(viii)(A) (Specify in 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(s)(2)(viii)(B) Abstract below and in Text, 20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x) NRC Form 366A LICENSEE CONTACT FOR THIS LER 12 NAHE TELEPHONE NUHBER (Include Ares Code)

Steve Austin, Compliance Licensing Engineer- (205)729-2070 COHPLETE ONE LINE FOR EACH C(NPONENT FAILURE DESCRIBED IN THIS REPORT 13 REPORTABLE REPORTABLE CAUSE SYSTEH COHPONEHT HANUFACTURER CAUSE SYSTEH COHPONEHI'ANUFACTURER TO NPRDS TO NPRDS BJ TM N SUPPLEHENTAL REPORT EXPECTED 14 MONTH DAY YEAR EXPECTED YES SUBMISSION X NO DATE (15)

(If yes, complete EXPECTED SUBMISSION DATE).

(Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16) from full power due to a ABSTRACT On April 15, 1994, at 0219 hours0.00253 days <br />0.0608 hours <br />3.621032e-4 weeks <br />8.33295e-5 months <br /> , Unit 2 received a full scram RPS trip signal generated by a low Scram Pilot Air Header pressure signal. This resulted in a low reactor water level which caused isolation of various ESF that and RPS system actuation. Plant systems responded as expected with the exception high temperature alarms were received for the High Pressure Coolant Injection (HPCI) system. Affected ESF and RPS systems were returned to operable status by 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> on April 15, 1994.

Operators returned HPCI to service at 0535 hours0.00619 days <br />0.149 hours <br />8.845899e-4 weeks <br />2.035675e-4 months <br /> after no abnormal conditions could be found.

The root cause of this event was inappropriate personnel action during maintenance activity on the Scram Pilot Air Header. The personnel involved deviated from the work order, but did not take the proper actions to ensure that their actions would not adversely affect plant operation. If the work order had been performed as written the scram would not,have occurred.

During the unit scram a false high temperature alarm in the HPCI led to isolation of HPCI.

This was attributed to a failed module in the temperature detection loop.

This event is reportable per 10 CFR 50.73(a)(2)(iv') due to the ESF and RPS train actuation, and 50.73(a)(2)(v) due to the isolation of the HPCI system, which this is a single system.

Corrective actions to prevent recurrence include a review of event by appropriate personnel and tighter controls for those activities which have the potential for ESF actuation.

NRC FORM 366 (5-92)

0 NRC FORM 366A U.S. NUCLEAR REGULATORY CQOIISSIOH APPROVED BY (H(B NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY NITH THIS INFORMATION COLLECTION REQUEST: 50.0 MRS'ORllARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT LICENSEE EVENT REPORT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, TEXT CONTINUATION NASHINGTON, DC 20555-0001, AND TO THE PAPERNORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, NASHINGTON, DC 20503 FACILITY NAME (1) DOCKET NlMBER (2) LER NIHIBER (6) PAGE (3)

'YEAR SEQUENTIAL REVISION NUMBER NUMBER Browns Ferry Unit 2 05000260 94 04 00 2 of 8 TEXT If more s ce s r vired use edd t onsl co les of HRC Form 366A (17)

I ~ PLANT CONDZTZONS Unit 2 was at 3288 megawatts thermal or 100 percent power. Units 1 and 3 were defueled.

DESCRIPTION OF EVENT Ao Event On April 15, 1994, at .0219 hours0.00253 days <br />0.0608 hours <br />3.621032e-4 weeks <br />8.33295e-5 months <br />, Unit 2 received a full scram from 100 percent power. At the time of this event, valve [ZSV) manipulations were being performed on the Scram Pilot Air Header

[LE]. The scram was generated by a Reactor Protection System (RPS) [JC] actuation due to a RPS trip signal generated by a low Scram Pilot Air Header pressure signal. The full power scram resulted in a low reactor water level which caused isolation or actuation signals to the following Primary Containment Isolation System [JE](PCIS) systems/components:

~ PCIS group 2, Shutdown cooling mode of Residual Heat Removal

[BO] system; Drywell floor drain isolation valve, Drywell equipment drain sump isolat'ion valve [WP]

~ PCIS group 3, Reactor Water Cleanup [CE)

~ PCIS group 6, Primary Containment Purge and Ventilation [JM];

Unit 2 Reactor Zone Ventilation [VB]; Refuel Zone Ventilation

[VA]; Standby Gas Treatment [BH)I Control Room Emergency Ventilation [VI)

~ PCIS group 8, Transverse Incore Probe [IG) withdrawal On April 15, at approximately 0200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br />, maintenance activities were in progress for the Standby Pressure Regulator (2-PIC-085-0067) on the Scram Pilot Air Header (See Figure). The work order for this activity specified that only the header isolation valve (2-085-261) on the inlet side of the pressure regulator needed to be closed to perform this activity. However, as an additional precaution, the operations and maintenance personnel involved in this activity also decided to close the outlet valve (2-085-243). However, the assigned ASOS did not realize that the cross-tie valve (2-085-244) was closed. While closing the outlet valve the ASOS observed a pressure spike on the lead pressure regulator pressure indication (2-PIC-85-0066). The closing of the outlet side valve isolated both the lead primary and standby pressure regulators.

Ol NRC FORM 366A U.S. NJCLEAR REGULATORY CQOIISSIOH APPROVED BY OMB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 MRS ~ FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT LICENSEE EVENT REPORT BRANCH (MHBB 7714), U.S. NUCLEAR REGULATORY COMMISSIONS TEXT CONTINUATION WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 FACILITY NAME (1) DOCKET NIIBER (2) LER NUMBER (6) PAGE (3)

YEAR SEQUEH'IIAL REVISIOH NUMBER NUMBER Browns Ferry Unit 2 05000260 94 04 00 3 of 8 TEXT If more s ce is r Wired use additional co ies of NRC Form 366A (17)

O 331 PI%7A PI-67B 261 243 246 BAJ~RAM.ARJ 0 PI-7 0 0 262 P!46A PI-66B 263 260 O 244 0 PIC-66 SCRAM DISC AR PRESS LOW As a result, at 0218 hours0.00252 days <br />0.0606 hours <br />3.604497e-4 weeks <br />8.2949e-5 months <br />, the Unit 2 Reactor Operator received a low scram air header pressure alarm and a half scram on Reactor Protection System "A". The reactor operator then attempted to reset the alarm and contact the ASOS at the pressure regulator. At 0219 hours0.00253 days <br />0.0608 hours <br />3.621032e-4 weeks <br />8.33295e-5 months <br />, the Unit 2 Reactor received a full scram from a Scram Pilot Air Header Low Pressure set point trip. This was followed by a insertion of the control rods, and PCIS group 2, 3, 6, and 8 isolations. At 0220 hours0.00255 days <br />0.0611 hours <br />3.637566e-4 weeks <br />8.371e-5 months <br />, the main turbine generator [TA] tripped.

All systems responded as expected with the exception that operators received a Unit 2 High Pressure Coolant Injection (HPCI) System (BJ]

area temperature alarm indicating a possible steam leak. Affected systems were returned*to operable status by 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br />. HPCI was returned to service at 0535 hours0.00619 days <br />0.149 hours <br />8.845899e-4 weeks <br />2.035675e-4 months <br /> after no abnormal conditions or alarms could be found.

f NRC FORH 366A U.S. NUCLEAR REGULATORY CAB(ISSI ON. APPROVED BY (WB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COKPLY IJITH THIS INFORMATION COLLECT ION REOUEST: 50.0 HRS. FORIIARD COKKEHTS REGARDING BURDEH EST IHATE 'TO THE INFORMATION AMD RECORDS KAMAGEKENT LICENSEE EVENT REPORT BRANCH (HNBB 7714), UPS. NUCLEAR REGULATORY COKKISSION, TEXT CONTINUATION NASHINGTOM, DC 20555-0001, AND TO THE PAPERNORK REDUCTION PROJECT (3150-0104), OFFICE OF KAMAGEHENT AND BUDGET, NASHINGTOM, DC 20503 FACILITY NAKE (1) DOCKET NUKBER (2) LER NQ(BER (6) PAGE (3)

YEAR SEOUEM'IIAL REVISION NUMBER NUMBER Browns Ferry Unit 2 05000260 94 04 00 4 of 8 TEXT tf more s sce is r ired use additional co ies of NRC Form 366A (1/)

This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv), as

'any event of condition that resulted in manual or automatic actuation of any engineered safety feature including the reactor protection system. Additionally, due to the isolation of HPCI which is a single train safety system, this event is reportable in accordance with 10 CFR 50.73(a)(2)(v)(A), as any event or condition that alone could have prevented the fulfillment of the safety function of structures of systems that are needed to shutdown the reactor and maintain it in a safe shutdown condition.

B. Ino erable Structures Cpm onents or S stems that Contributed to the Eventt None.

C~ Dates and A roximate Times of Ma'or Occurrences:

April 15, 1994 at 0205 CST ASOS began isolation of the Standby Pressure Regulator.

April 15, 1994 at 0219 CST The Unit 2 reactor received a full scram from a Scram Pilot Air Header Low Pressure set point trip.

April 15, 1994 at 0227 CST The Unit 2 Reactor Operator received the Unit 2 HPCI area temperature alarm indicating a possible steam leak. HPCI was manually isolated due to suspected steam leak.

April 15, 1994 at 0300 CST The PCIS actuation are reset, SBGT trains are returned to standby readiness.

April 15, 1994 at 0510 CST TVA'akes a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> nonemergency notification to NRC in accordance with 10 CFR 50.72(b)(2)(ii) and 10 CFR 50.72 (b)(2)(iii) ~

April 15, 1994 at 0535 CST HPCI was realigned to standby readiness.

~I NRC FORM 366A U.S. NUCLEAR REGULATORY CQIIISS ION APPROVED BY QNI NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION 'REQUEST: 50.0 HRS. FORIIARD COMMENTS REGARDING BURDEN EST IHATE TO THE INFORMATION AND RECORDS MANAGEMENT LICENSEE EVENT REPORT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, TEXT CONTINUATION WASHINGTON, DC 20555 0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON< DC 20503 FACILITY NAME (1) DOCKET NQIBER (2) LER NUMBER (6) PAGE (3)

'YEAR SEQUENTIAL REVI SION NUMBER NUMBER Browne Ferry Unit 2 05000260 04 00 5 of 8 TEXT If more s ce is r uired use additional co ies of NRC Form 366A (17)

D. Other S stems or Secondar Function Affected)

None.

E. Method of Discover The Unit 2 Operator received a Scram Pilot Air Header Low Pressure Alarm and a Half Scram In the Unit 2 Main Control Room.

These alarms were followed by alarms indicating a full reactor scram had occurred.

F< 0 erator Actions:

At the onset of the event the Unit 2 Reactor Operator attempted to reset the half scram that occurred when both pressure regulators were isolated. Upon receiving the full reactor scram on low scram pilot header pxessure the reactor operator performed the actions described by Abnormal Operating Znstruction "Reactor Scram," bringing the reactor to hot standby condition. The plant responded as expected with the exception of the HPCZ high temperature alarm wh'ich required HPCI to be manually isolated.

G. Safet S stem Res onsesf The safety systems listed in Section IIA of this report responded to the reactor scram as designed.

CAUSE OF THE EVENT A. Immediate Cause:

The immediate cause of the reactor scram was the isolation of both the primary and secondary Scram Pilot Header Air Pressure regulators. This isolation resulted in a low pressure condition which actuated the Scram Pilot Header Low Pressure Switches, completing the logic for a full scram of the reactor.

B~ Root Cause:

The root cause of this event is inappropriate personnel action.

The personnel involved in this event deviated from an approved work order without taking appropriate action to ensure that the resultant valve lineup would not adversely affect plant operation. The work order required only closure of the inlet valve to the pressure xegulator. However, as a further precautionary measure, the ASOS decided to isolate the downstream side of the regulator, but failed to communicate this action to the on-shift SOS.

HRC FORM 366A U.S. NUCLEAR REGULATORY CQHIISSION APPROVED BY (H(B HO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPL'Y llITH THIS INFORMATION COLLECTIOH REQUEST: 50 ' HRS FORHARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MAHAGEHENT LICENSEE EVENT REPORT BRANCH (MNBB 7714), U.S. HUCLEAR REGULATORY COMMISSION, TEXT CONTZNUATZON llASHINGTON, DC 20555 0001, AND TO THE PAPERlIORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON DC 20503 FACILITY NAME (1) DOCKET NIHIBER (2) LER NIBBLER (6) PAGE (3)

'YEAR SEQUENI'IAL REVISIOH NUMBER NUMBER Browns Ferry Unit 2 05000260 94 04 00 6 of 8 TEXT If more s ce is r uired use additional co ies of NRC Form 366A (17)

The personnel involved recognized that the cross tie valve (2-085-244) must be open to provide flow to the lead pressure regulator (2-PZC-085-0066), but did not physically verify that the cross tie valve was open prior to closing the outlet isolation valve on the discharge side of the secondary pressure regulator. This action isolated both the primary and secondary pressure regulators on the Scram Pilot Air Header. This action also reduced the pressure to the Scram Pilot Header Low Pressure Switches to below the set point, causing the subsequent reactor scram.

Regarding the high temperature alarm for HPCI, TVA's investigation into this event determined that the actual temperature in the area was lower than that indicated by the alarm. Further investigation has revealed that an unexpected failure of a module in the temperature detection loop was the cause of the false high reading.

C. Contributin Factors:

Contributing to this event was a discrepancy between the plant Mechanical Control Diagram and the Flow Diagram utilized by the affected personnel during this event. The Mechanical Control Diagram indicated the normal position of the cross tie valve (2-085-244) to be open. The Flow Diagram depicts the normal position of the cross tie valve as closed. Contrary to Standard Operations Methods, the ASOS, performing the valve manipulations utilized the Mechanical Control Diagram when establishing isolation boundaries.

IV. ANALYSIS OF THE EVENT The design of the scram pilot air header piping requires that the Control Rod Dr'ive [AA) (CRD) system fail safe on loss of control air pressure. A low air pressure condition is a condition in which the control rods may randomly drift and the scram discharge volume may fill with water. This random drift could occur when the air pressure on the scram valve actuators is not sufficient to keep the valves seated. When the valves unseat, hydraulic pressure is applied to the hydraulic-control unit's piston and the control rod will drift in.

The set point of the air header pressure is selected to be low enough to prevent spurious trips, but high enough to prevent unseating of the scram valves. In the event, the RPS'ctuation occurred as designed and all systems functioned as expected. Therefore, this event had no safety significance.

0 NRC FORH 366A U.S. NUCLEAR REGULATORY CCHHI SSION APPROVED BZ MB 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 ESTIHATE TO THE INFORHATION AND RECORDS MANAGEMEHT LICENSEE EVENT REPORT BRANCH (MNBB 7714), 'U.ST NUCLEAR REGULATORY COMMISSION, TEXT CONTINUATION WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTIOH PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 FACILITY NAME (1) DOCKET NINBER (2) LER HWBER (6) PAGE (3)

YEAR SEQUENTIAL REVI SI OH NUHBER NUMBER Browns Ferry Unit 2 05000260 94 04 00 7 of 8 TEXT If more s ee is r uired use additional co ies of NRC Form 366A (17)

V CORRECTIVE ACTIONS A. Immediate Corrective Actions:

The affected systems were restored to operable status.

Concerning the root cause of the event, appropriate personnel corrective actions were taken regarding the individuals involved in this event.

Concerning the contributing factors in the event, TVA issued Night Orders stating that the Flow Diagrams not the Mechanical Control Diagrams are be utilized for valve alignments.

Additionally, the drawing discrepancy that contributed to this event was revised.

The failed HPCI area temperature detection loop module was replaced prior to returning Unit 2 to power operation.

Bo Corrective Actions to Prevent Recurrence:

TVA will develop controls which provide additional reviews for maintenance activities which have the potential to cause a reactor scram on the operating unit.

This event will be reviewed by the appropriate Operations, Maintenance, and Technical Support Personnel.

TVA will evaluate the methods and controls for approval and documentation of the manipulation of components outside the prescribed steps of a Work Order.

Though not essential to prevent recurrence of this event, TVA reviewed the Mechanical Control Prints for the CRD and Control Air systems. Other minor discrepancies identified by the review were also corrected. Additionally, TVA selected four other systems and reviewed them for valve position, component sequence/process configuration. The review provided a high degree of confidence that other major discrepancies that could cause a reactor scram are unlikely.

0 0 NRC FORH 366A U.S. NUCLEAR REGULATORY COHIISSION APPROVED BY (NIB NO. 3150-0104 (5-92) EXPIRES 5/3'I/95 ESTIHATED BURDEN PER RESPONSE TO COHPLY WITH THIS INFORHATION COLLECTION REQUEST: 50.0 HRS. FORWARD COHHENTS REGARDING BURDEN ESTIHATE TO THE INFORHATION AND RECORDS HANAGEHENT LICENSEE EVENT REPORT BRANCH (HNBB 7714), U.S. NUCLEAR REGULATORY COHHISSION, TEXT CONTINUATION WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0'l04), OFFICE OF 'HANAGEHENT AND BUDGET, WASHINGTON, DC 20503 FACILITY NAHE (1) DOCKET NIRIBER (2) LER NLNBER (6) PAGE (3)

YEAR SEQUEHTIAL REVISION NUHBER NUHBER Browns Ferry Unit 2 05000260 94 04 00 8 of 8 TEXT If more s ce is r uired use edditionsi co ies of NRC Form 3 66A (17)

VZ ~ ADDITIONAL INFORMATION A. Failed Cpm onentsi An unexpected failure -of a module, Model PllG-1 manufactured by Panagard, in the. temperature detection loop for the HPCI area high temperature alarm. This resulted in a higher than actual area temperature indication, requiring that HPCI be isolated during the unit scram.

B. Previous LERs on Similar Events:

LER 260/89028 was issued for an event involving the Scram Pilot Air Header. In this event personnel were installing 2-PI-085-0067A when a solder joint in the same section of the Scram Pilot Air Header failed. This reduced the header pressure to the RPS actuation set point.

TVA reviewed the circumstances surrounding the declaring HPCI inoperable during the unit scram, and found no record of having to declare HPCI inoperable because of a false high area temperature.

VII+ Commitments This event will be reviewed by the appropriate Operations, Maintenance and Technical Support Personnel. This review will be completed by July 15, 1994.

2. TVA will develop controls which provide additional reviews for activities which have the potential to cause a reactor scram on the operating unit. This will be completed by July 15, 1994.

3 ~ TVA will evaluate the methods and controls for approval documentation of the manipulation of components outside the prescribed steps of a Work Order. This evaluation will be completed by July 15, 1994.

Energy Industry Identification System (EIZS) system and component codes are identified in the text with brackets (e.g., [XX)).

0 li