ML18038B259

LER 95-004-00:on 950330,reactor Scram Resulted from Personnel Error During Surveillance Testing Caused Actuation of ESF Sys.Operations Personnel Brought Plant to Shutdown Condition

ML18038B259
Person / Time
Site:	Browns Ferry
Issue date:	04/28/1995
From:	Jay Wallace TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18038B258	List: ML18038B257 ML18038B259
References
LER-95-004, LER-95-4, NUDOCS 9505020309
Download: ML18038B259 (14)

Text

NRC FORN 366 U.S. JRJCLEAR REGULATORY C(NNIISSION APPROVED BY IWB NO. 3150-0104 (5-92) EXP I RES 5/31/95 ESTIHATED BURDEN PER RESPONSE TO COHPLY lJITH THIS INFORHATION COLLECTION REQUEST: 50.0 HRS.

LZCENSEE EVENT REPORT (LER) FORNARD COHHENTS REGARDING BURDEN ESTIHATE TO THE INFORHATION AND RECORDS HANAGEHENT BRANCH (HNBB 7714), U.S. NUCLEAR REGULATORY COHHISSION, (See reverse for required nunber of digits/characters for each block) llASHIHGTON, DC 20555-0001 AND TO THE PAPERIJORK REDUCTION PROJECT (3110-0104), OFFICE OF NANAGENENT AND BUDGET llASHINGTON DC 20503.

FACILITY NAIL,(1) DOCKET NINBER (2) PAGE (3)

Browns Ferr Nuclear Plant BFN Unit 2 05000260 1 OF 7 TITLE (4) Reactor scram resulting from personnel error during surveillance testing caused the actuation of the ESF system.

EVENT DATE 5 LER NNBER 6 REPORT DATE 7 OTHER FACILITIES INVOLVED 8 SEQUENTIAL REVISIOH FACILITY NAHE NA DOCKET NUHBER NORTH DAY YEAR HONTH DAY YEAR NUHBER NUHBER FACILITY NAHE NA DOCKET NUHBER 03 30 95 95 004 00 04 28 95 OPERATING THIS REPORT IS SUBHITTED PURSUANT TO TNE REQJIREHENTS OF 10 CFR: Check one or more 11 NX)E (9) N 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)

PQKR 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c) 100 LEVEL (10) 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER 20.405(a)(1)(iii) 50.73(a)(2)(i)(B) 50.73(a)(2)(viii)(A) (Specify in 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) Abstract below and in Text, 20.405(a)(1)(v) 50.73(a)(2)(iii) 50 '3(a)(2)(x) , NRC Form 366A LICENSEE CONTACT FOR THIS LER 12 NAHE TELEPHONE NUHBER (Include Area Code)

James E. Wallace, Compliance Licensing Engineer (205)729-7874 GNPLETE ONE LINE'FOR EACH C(NPONENT FAILURE DESCRIBED IN THIS REP(NIT 13 REPORTABLE REPORTABLE CAUSE SYSTEH COHPONENT HANUFACTURER CAUSE SYSTEH COHPONENT HANUFACTURER TO NPRDS TO NPRDS SUPPLEHENTAL REPORT EXPECTED 14 EXPECTED HONTH DAY YEAR YES SUBHI SS ION (If yes, complete EXPECTED SUBHISSION DATE). DATE (15)

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

On March 30, 1995, at 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br />, the Unit 2 reactor scrammed during the performance of the Core and Containment Systems Analog Trip Unit Functional Test. During this test, alternate rod insertion solenoid valves opened (i.e., energized) and vented control air from the scram pilot air header, causing a low scram pilot air header pressure condition (less than 53 psig.), which initiated a reactor scram. The scram then resulted in the automatic actuation of the engineered safety feature (ESF) system due to a sensed low reactor water level condition. This event is, therefore, reportable in accordance with 10 CFR 50.73 (a)(2)(iv) as a condition which resulted in an automatic actuation of the ESF system. The root cause of the event was personnel error in that an Instrumentation and Controls technician prematurely repositioned the Anticipated Transient Without Scram mode switch from the 'TEST'o the 'NORMAL'osition with a test signal present. Corrective actions involve appropriate personnel corrective actions for the individual in this event.

9505020309 950428 PDR ADOCK 050002b0 S PDR NRC FORH ( - )

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NRC FORH 366A U.S. NJCLEAR REGULATORY COfBIISSIOH APPROVED BY (Ã8 HO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTINATED BURDEN PER RESPONSE TO COHPLY WITH THIS INFORNATIOH COLLECTIOH REQUEST: 50.0 HRS. FORWARD COHHENTS REGARDING BURDEN EST IHATE TO THE 'IHFORHATION AND RECORDS NANAGEHENT BRANCH (MNBB 7714), U.S. NUCLEAR 'REGULATORY COHHISSIOH ~

LICENSEE EVENT REPORT WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF HAHAGEHEHT AND BUDGET, WASHINGTON DC 20503 FACILITY HAHE (1) DOCKET HISSER (2) LER NWER (6) PAGE (3)

TEAR SEQUENTIAL REVI S I OH NUHBER Browns Ferry Unit 2 05000260 95 '04 HUNGER 00 2 of 7 TEXT If more s ce is r fred use additional co les of NRC Form 366A (17)

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~ PLANT CONDITIONS 100 the time this event occurred, Unit 2 was operating at approximately percent power. Units 1 and 3 were shutdown and defueled.

DESCRIPTION OF EVENT A. Event At 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> Central standard Time (CST) on March 30, 1995, Unit 2 experienced a reactor scram while the unit was at full power. Instrumentation and Controls (ZGC) technicians [utility, non-licensed] were performing Surveillance Instruction (SI) 2-SZ-4.2.B-ATU(C), "Core and Containment Systems Analog Trip Unit Functional Test." This SI tests certain logic circuits that generate the Anticipated Transient Without Scram (ATWS)

[JC]/Alternate Rod Insertion (ARI) [JD] signal for a reactor high pressure condition.

During performance of the SI, an IEC technician stationed at the analog trip unit (ATU) cabinet in Auxiliary Instrument Room,No.

2 increased the stable current amplitude which locked in the relay in the ARI initiation circuitry (Figure 1). Zn step 7.11.22 of the SI, the ZRC technician was in the process of decreasing the stable current amplitude when a second IEC technician at the ATWS panel in Electric Board. Room 2A prematurely repositioned the ATWS mode switch [HS) from the

'TEST'o the 'NORMAL'osition. The premature movement of the handswitch to 'NORMAL'efore the ATWS/ARI logic was reset quickly vented the air from the scram pilot air header which caused a low scram pilot air header pressure condition (less than 53 psig.) and resulted in a reactor scram from Reactor Protection System (RPS) actuation.

When the scram pilot air header pressure decreased below 53 psig, the reactor scrammed as expected due to a sensed low reactor water level condition. The reactor low level signal initiated the following primary containment isolation systems:

group 2 shutdown cooling mode of the residual heat removal system [BO); group 3 reactor water cleanup system [CE];

group 6 - primary containment purge and vent [JM), Unit '2 reactor zone ventilation [VB], refueling zone ventilation [VA],

standby gas,treatment system [BH), and control room emergency ventilation system [VI] initiationl and group 8 transverse in-core probes [ZG] withdrawal.

At 2316 hours0.0268 days <br />0.643 hours <br />0.00383 weeks <br />8.81238e-4 months <br />, the SI was re-performed in an attempt to duplicate the scram condition. However, the scram condition could not be repeated in the field. On March 31, 1995 at 0220

NRC FORN 366A U.S is)CLEAR REGULATORY C(NSIISSI(NI APPROVED BY (H(B NO. 3150-0104 (5-92) EXPIRES'/31/95 ESTIHATED BURDEN PER RESPONSE TO CONPLY WITH THIS INFORHATIOH COLLECT ION REQUEST: 50.0 HRS. FORWARD CWENTS REGARDING BURDEN EST IHATE TO THE INFORNATION AND RECORDS NANAGENENT BRANCH (NNBB 7714), U.S. NUCLEAR REGULATORY CONNISSIOH, LICENSEE EVENT REPORT WASHINGTON, DC 20555-0001, AHD TO THE PAPERWORK REDUCTION TEXT CONTINUATION PROJECT (3150.0104), OFFICE OF HAHAGENEHT AHD BUDGET, WASHIHGTON DC 20503 FACILITY NQK (1) DOCKET NIN(BER (2) LER NWBER (6) PAGE (3)

YEAR SEQUENTIAL REVISION HUNGER NUNBER Browne Ferry Unit 2 05000260 95 004 00 3 of 7 TEXT If more s ce is r ired use additional co ies of NRC Form 366A (17)

.hours, the SI was satisfactorily completed. On April 2, '1995 at 1506 hours0.0174 days <br />0.418 hours <br />0.00249 weeks <br />5.73033e-4 months <br />, the, reactor was restarted and synchronized to the TVA system grid.

This event is reportable in accordance with 10 CFR 50.73 (a)(2)(iv) as a condition that resulted in an automatic actuation of the ESF system.

Bo Ino erabla Structures Com onents or S stems that Contributed to the Events None.

Co Dates and A roximate Times of Ma'or Occurrences:.

March 30, 1995 at 1630 CST 2-SI-4.2.B-ATU(C) commenced March 30,- 1995 at 1800 CST Step 7.11.22 of the SI was in progress when the reactor scrammed March 30, 1995 at 2033 CST TVA provided a 10 CFR 50.72(b)(2)(ii) four-hour notification to NRC operations center that the reactor scrammed and the ESFs automatically actuated March 30, 1995 at 2316 CST The SI was re-performed in an attempt to duplicate the scram condition; the scram condition could not be repeated in the field March 31, 1995 at 0220 CST The SI was satisfactorily completed April 2, 1995 at 1506 CST The reactor was restarted and synchronized to the TVA system grid D. Other S stems or Seconda Functions Affected:

None.

E~ 'Method of Discove This condition was di.scovered when the control room Operations personnel [licensed, utility) received alarms and indicators that the reactor tripped due to a sensed low reactor water level condition.

0 r NRC FORH 366A U.S IRICLEAR REGULATORY C(MB(ISSION APPROVED BY (MHI NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIHATED BURDEN PER RESPONSE TO COHPLY'llITH THIS INFORHATION COLLECTION REQUEST: 50.0 HRS. FORNARD COHHENTS REGARD INC BURDEN EST IHATE TO THE INFORHATION AHD RECORDS HAHAGEHENT BRANCH (HNBB 7714), U.S. NUCLEAR REGULATORY COHHISSION, LICENSEE EVENT REPORT llASHIMGTON, DC 20555-0001, AMD TO THE PAPERHORK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF HAMAGEHENT AND BUDGET@

HASHINGTOM DC 20503 FACILITY NAIK (1) DOCKET NNBER (2) LER M(SIDER (6) PAGE (3)

YEAR SEQUENTIAL REVI SION NUMBER NUHBER Browns Ferry Unit 2 05000260 95 004 00 4 of 7 TEXT lf more s ce is r ired use additional co ies of MRC Form 366A (17)

F. 0 erator Actionst Once the reactor scrammed, Operations personnel responded to the scram in accordance with appropriate procedures, and the reactor was stabilized and safely brought to a shutdown condition.

G. Safet S stem Res onsest All safety systems responded as designed fcir this type of event.

ZIZ. CAUSE OF THE EVENT A. Immediate Cause:

The immediate cause of the event was that the Unit 2 ATWS mode switch was prematurely repositioned to the 'NORMAL'osition before the ATWS/ARI logic was reset. This switch movement quickly vented contiol air from the scram pilot air header causing a low scram pilot air header pressure condition (less than 53 psig.) and resulted in an RPS reactor scram.

B. Root Causel The root cause of the event was personnel error. An IGC technician prematurely repositioned the ATWS mode switch from the 'TEST'o the 'NORMAL'osition. The procedure requires that the switch remain in the 'TEST'osition with the logic signal present to prevent energizing the solenoid valves which vent the scram pilot air header.

ZVo ANALYSIS OF THE EVENT The ATWS/ARI system is designed as a redundant, independent and diverse reactor shutdown system. The ATWS/ARI system provides an alternate means of venting the scram pilot air header to generate a reactor scram in the event of an anticipated transient without the desired RPS response. As expected, the solenoid valves that vented the scram pilot air header remained energized until the initiation logic was reset. The ATWS instrumentation also affects parameters that initiate or .control primary containment isolation and initiation of plant ventilation systems. In this event, control air was vented from the scram pilot air header resulting in the initiation of the ATWS/ARI, which caused the control rods to insert to safely shut down the reactor. All plant equipment responded as designed. Therefore, this event did not affect the health and safety of plant personnel and the public.

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NRC FORII 366A U.S. IRICLEAR REGULATORY CQNIISSI ON APPROVED BY (NB NO. 3150-0104 (5-92) EXPIRES. 5/31/95 ESTIHATED BURDEN PER RESPOHSE TO COHPLY llITH THIS IHFORHATIOH COLLECTION REQUEST: 50.0 HRS ~ FORNARD COHNENTS REGARD IHG BURDEN EST IHATE TO THE IHFORNATIOH AND RECORDS HANAGEHENT BRANCH (NHBB 7714), U.S. NUCLEAR REGULATORY COHNISSION, LICENSEE EVENT REPORT iJASHIHGTON, DC 20555-0001, AND TO THE PAPERHORK REDUCTION TEXT 'CONTINUATION PROJECT (3150-0104), OFFICE OF'ANAGEHEHT AHD BUDGET,

'MASHINGTON DC 20503 FACILITY NAIL (1) DOCKET NWSER (2) LER HISSER (6) PAGE (3)

YEAR SEQUENTIAL REVISI OH NUNBER HUHBER

,Browns Ferry Unit 2 05000260 95 004 00 5 of 7 TEXT tf more s ce is r ired use additional co ies of NRC Form 366A '(17)

V CORRECTIVE ACTIONS A. Immediate Corrective Actionsl Operations personnel responded to the reactor scram and safely

.brought the plant to a shutdown condition. The SI was stopped.

The ATWS mode switch was investigated to ensure that the correct contacts were opened. The switch was replaced and was bench-tested/examined for any evidence of contact wiper failure/sticking. However, the switch internals did not reveal any adverse indications (e.g., contacts burned, cam or switch mechanism problems). The SI. was reviewed to determine errors existed and then re-preformed in an attempt to replicate if any the scram condition. However, the scram condition could not be repeated. The SI was then satisfactorily completed. An incident investigation was i'nitiated to determine the root cause of the event and appropriate corrective actions.

B. Corrective Actions to Prevent Recurrencel Corrective actions involve appropriate personnel corrective actions for the individual in this event.

VI ~ ADDITIONAL INFORMATION A. Failed Com onentsI None.

B. Previous Licensee Event Re orts LERs on Similar Events:

Although there have been previous LERs for personnel error where a control was inappropriately manipulated or operated out-of-sequence, none of the previous corrective actions would not have precluded this event.

LER 260/93004 addressed a high reactor pressure condition that resulted in an ATWS signal and initiated an ARI signal. The cause of the LER (260/93004) was inattention to detail in that an operator [utility, licensed) did not adequately evaluate the overall effects of ongoing SIs. Thi.s oversight subsequently caused a reactor scram. However, the corrective actions for LER (260/93004) would not have precluded this event (LER 260/95004) because the root cause of the previous LER was schedular in nature in that the unit Operator presumed that IEC personnel would notify him prior to each instrument being removed from service. In this LER (260/95004) Operations personnel were informed at appropriate times as required in the SI so that no schedular conflicts existed.

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NRC FORII 366A U.S IN)CLEAR REGUIATQtY CQBI I SSION APPROVED BY QIB NO. 3150-0104 (5-92) EXP I RES 5/31/95 ESTIHATED BURDEN PER RESPQISE TO COHPLY IJITH THIS INFORHATION COLLECTION REOUEST: 50.0 HRS ~ FORMARD COHHENTS REGARDING

, BURDEH 'EST IHATE. TO THE INFORHAT I OH AND RECORDS HANAGEHENT BRANCH (HNBB 7714), U.ST NUCLEAR REGULATORY COHHISSIOH, LICENSEE EVENT REPORT NASHIHGTOH, DC 20555-0001, AND TO THE PAPERIQRK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF HAHAGEHENT AND BUDGET, llASHINGTON DC 20503 FACILITY NAIL (1) DOCKET NINIBER"(2) LER. NWBER (6l PAGE (3l YEAR SEQUENTIAL REVI S I OH NUHBER NUHBER Browne Ferry Unit 2 05000260 95 004 00 6 of'7 TEXT If more s ce is r ired Use additionst co ies of NRC Form 366A (17)

VIE Commitments None..

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

P MRC FORM 366A U.S NUCLEAR REGULATORY C(MBIISSIOH ~ APPROVED BY (BIB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIHATED BURDEH PER RESPONSE TO COHPLY llITH THIS INFORMATION COLLECT IOM REQUESTs 50+0 HRSo FORl!ARD COHHENTS REGARDING BURDEH ESTIHATE TO THE INFORHATION AND RECORDS MANAGEMENT BRANCH (HNBB 7714), U.S. NUCLEAR REGULATORY COHHI SS ION g LICENSEE EVENT REPORT MASHIMGTON, DC 20555-0001, AND TO THE PAPERMORK REDUCTION TEXT CONTZNUATZON PROJECT (3150-0104) ~ OFFICE OF MANAGEMENT AND BUDGET, IIASHINGTOM DC 20503 FACILITY NQK (1) DOCKET NMSER (2) LER MIMKR (6) PAGE (3)

YEAR SEQUENTIAL REVISION NUMBER NUMBER Browne Ferry Unit 2 05000260 95 004 00 7 of 7 TEXT If more s ce is r ired use edditiossai co es of NRC orm 366A (17)

QIODE RELAY ATVS ATVS HS.TEST HS.NORM SOLENOID ZBO V.D.C.

ARI INITIATION SIGNAL

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