05000260/LER-1995-005-01, :on 950607,HPCI Steam Supply Valve Failed During Testing Due to Failure of HPCI Steam Supply Valve to Open During Initial Start of Flow Test.Issued Maint Work Order to Investigate & Determine Cause of Valve Failure
| ML18038B324 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/07/1995 |
| From: | Austin S TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML18038B323 | List: |
| References | |
| LER-95-005-01, LER-95-5-1, NUDOCS 9507110095 | |
| Download: ML18038B324 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(x) |
| 2601995005R01 - NRC Website | |
text
NRC FORH 366 (5-92)
U.S.
NUCLEAR REGULATORT CCHIISSION LICENSEE EVENT REPORT (LER)
APPROVED BY CWB NO. 3150-0104 EXPIRES 5/31/95 ESTIMA'IED BURDEN PER
RESPONSE
TO COMPLY lIITN THIS INFORMATION COLLECTION REOUEST:
50.0 HRS.
FORNARD COMHENTS REGARDING BURDEN ESTIHATE TO THE INFORMATION AND RECORDS MANAGEHENT BRANCH (MNBB 7714), U.S.
NUCLEAR REGULATORY COMMISSION, HASHINGTON, DC 20555-0001 AND TO THE PAPERNORK REDUCTION PROJECT (31'104),
OFFICE OF MANAGEHENT AND BUDGET MASHINGTON DC 20503.
FACILITY NAME (1)
Browns Ferry Nuclear Plant (BFN) Unit 2 DOCKET NINBER (2) 05000260 PAGE (3) 1OF5 TITLE (4) Failure Of The High Pressure Coolant Injection Steam Supply Valve During Testing EVENT DATE 5
MONTH DAY YEAR YEAR LER NMBER 6
SEOUENTIAL NUMBER REVISION NUMBER MONTH DAY YEAR REPORT DATE 7
FACILITY NAHE NA DOCKET NUMBER OTHER FACILITIES INVOLVED 8
06 07 95 95 005 00 07 07 95 FAC ILI 'IY NAME NA DOCKET NUMBER OPERATING M(6E (9)
PONER LEVEL (10)
N 100 THIS REPORT IS SUBMITTED PURSUANT 20.402(b) 20.405(a)(1)(i) 20.405(a)(1)(ii) 20.405(c) 50.36(c)(1) 50.36(c)(2)
X 50.73(a)(2)(iv) 50.73(a)(2)(v) 50.73(a)(2)(vii) 73.71(b) 73.71(c)
OTHER e
11 TO THE REQUIREMENTS OF
'10 CFR
=
Check one or mor 20.405(a)(1)(iii) 20.405(a)(1)(iv) 20.405(a)(1)(v) 50.73(a)(2)(i) 50.73(a)(2)(ii) 50.73(a)(2)(iii)
LICENSEE CONTACT FOR THIS'LER 12 50.73(a)(2)(viii)(A) 50.73(a)(2)(viff)(B) 50.73(a)(2)(x)
NAME Steven W. Austin, Compliance Licensing Engineer TELEPHONE NUHBER (Include Area Code)
(205)729-2070 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBE D IN THIS REPORT 13
CAUSE
SYS TEH COMPONENT MANUFACTURER REPORTABLE TO NPRDS
CAUSE
SYSTEM COMPOHENT HANUFACTURER REPORTABLE TO NPRDS SUPPLEMENTAL REPORT EXPECTED 14 YES (If yes, complete EXPECTED SUBHISSION DATE).
X NO EXPECTED SUSHI SS ION DATE (15)
MONTH DAY YEAR ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typeHritten lines)
(16)
On June 7,
1995, at approximately 2050 hours0.0237 days <br />0.569 hours <br />0.00339 weeks <br />7.80025e-4 months <br />, retroactive to 1836 hours0.0213 days <br />0.51 hours <br />0.00304 weeks <br />6.98598e-4 months <br />, TVA declared the High Pressure Coolant Injection (HPCI) system inoperable following hesitation of the turbine steam supply valve to open during performance of a Surveillance Instruction (SI).
At approximately 1836 hours0.0213 days <br />0.51 hours <br />0.00304 weeks <br />6.98598e-4 months <br />, TVA attempted to start the HPCI turbine from the main control room per the SZ.
On the initial attempt to run the HPCI turbine, the operator had indication that the steam supply valve was in an intermediate position with no increase in turbine speed or pump output.
Approximately 50 seconds later, the operator gave the steam supply valve a second open signal and the turbine accelerated to the overspeed setpoint and tripped.
TVA determined that the overspeed was caused by the steam supply valve hesitating to open.
Subsequently, TVA declared the HPCI system inoperable.
The root
cause of the event
was a random failure of the 250V DC valve motor open seal-in contacts on the steam supply valve.
TVA found that the contacts were pitted and indicated signs of arc deposits.
The contacts were cleaned and the valve was stroked several times.
TVA plans to inspect these contactors within the next two months for signs of degradation.
TVA is reporting this event in accordance with 10 CFR 50.73(a)(2)(v) as an event or condition that alone could have prevented the fulfillment of the safety function of a structure or system needed to mitigate the consequences of an accident.
950711005'5 950707 PDR ADOCK 05000260 PDR NRC FORM 366 (5-92)
0
NRC FORM 3QjA (5-92)
U.S ~
NUCLEAR REGULATORY COWIISSION LICENSEE EVENT REPORT TEXT CONTINUATION APPROVED BY (RIB NO. 3150-0104 EXPIRES 5/31/95 ESTIMATED BURDEN PER
RESPONSE
TO COMPLY WITH THIS INFORMATION'OLLECTIOH REQUESI':
50.0 MRS'ORWARD COMHEHTS REGARDING BURDEN ESTIMATE TO'HE INFORMATION AND RECORDS MANAGEMEHT BRANCH (MNBB 7714),
U.S.
NUCLEAR REGULATOR'Y COMMISSION, WASHIHGTOH, DC 20555.0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150.0104),
OFFICE OF MANAGEMENT AND
- BUDGET, WASHINGTON DC 20503 FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
YEAR SEQUENTIAL REVISION NUMBER NUMBER PAGE (3)
Browns Ferry Unit 2 05000260 95 005 00 2 of 5 TEXT tf more s ace is r uired use additional co ies of(17).
PLANT CONDITIONS
Unit 2 was in the run mode at 100 percent power or 3291 megawatts thermal.
Units 1 and 3 were shutdown and defueled.
On June 7,
1995, at approximately 1836 hours0.0213 days <br />0.51 hours <br />0.00304 weeks <br />6.98598e-4 months <br />, operations commenced performance of a Surveillance Znstructi.'on (SI) to verify the operability of the High Pressure Coolant Injection (HPCI) [BJ] system.
II'ESCRIPTION OF EVENT A
Event:
On June 7,
1995, at 2050 hours0.0237 days <br />0.569 hours <br />0.00339 weeks <br />7.80025e-4 months <br />, retroactive to 1836 hours0.0213 days <br />0.51 hours <br />0.00304 weeks <br />6.98598e-4 months <br />, the HPCI system was declared inoperable.
TVA entered a Limiting Condition for Operation (LCO) for an inoperable HPCI system.
The details that led to this event are provided below.
On June 7,
1995, at approximately 1836 hours0.0213 days <br />0.51 hours <br />0.00304 weeks <br />6.98598e-4 months <br />, the HPCZ turbine was started from the Unit 2 Main Control Room for the HPCZ Flow Rate Test At Normal RPV Pressure SZ.
During the initial turbine start attempt, the operator had indication that the steam supply valve was in an intermediate position with no increase in turbine
- speed, pump discharge pressure or flow.
Approximately 50 seconds later, the operator gave the steam supply valve a second open signal.
Subsequently, the valve opened, the HPCZ turbine accelerated to the overspeed setpoint and tripped when the turbine speed exceeded 5000 RPM.
At apprcximately 1917 hours0.0222 days <br />0.533 hours <br />0.00317 weeks <br />7.294185e-4 months <br />, after in situ trouble shooting indicated no governor control system problems, the system steam valves were realigned and a
second attempt to perform the flow rate SI was made.
On this attempt the HPCZ turbine performed as designed.
At 2050 hours0.0237 days <br />0.569 hours <br />0.00339 weeks <br />7.80025e-4 months <br />, after reviewing the data from the first attempt to start the HPCI turbine, TVA determined that the HPCI steam supply valve hesitated to stroke open.
As required by system design, when the start signal was given, the HPCI.turbine auxiliary oil pump automatically started and the turbine stop and turbine control valves opened.
Subsequently, because these valves were in the full open position when steam flow to the HPCI turbine was established, the turbine experienced an overspeed condition.
Due to the aforementioned hesitation of the steam. supply valve, TVA declared the HPCZ system inoperable from the time of the initial attempted start (1836 hours0.0213 days <br />0.51 hours <br />0.00304 weeks <br />6.98598e-4 months <br />).
On June 8,
1995, at 1140 hours0.0132 days <br />0.317 hours <br />0.00188 weeks <br />4.3377e-4 months <br /> TVA declared HPCZ operable,
lh 4k
NRC FORH 36()A (5.92)
U.S.
NUCLEAR REGULATORY CQHIISS ION LICENSEE EVENT REPORT TEXT CONTINUATION APPROVED BY MS NO. 3150-0104 EXPIRES 5/31/95 ESTIMATED BURDEN PER
RESPONSE
TO COHPLY lllTH THIS INFORHATION COLLECTION REQUEST:
50.0 HRS.
FORUARD CONHENTS REGARDING BURDEN ESTIHATE TO THE INFORNATION AND RECORDS HANAGEHEHT BRANCH (HNBB 7714),
U.S.
NUCLEAR REGULA'TORY CONHISSIOH, llASHINGTON, DC 20555-0001, AND TO THE PAPERIN)RK REDUCTION PROJECT (3150-0104),
OFFICE OF HANAGENENT AND
- BUDGET, NASHINGTON DC 20503 FACILITY NINE (1)
DOCKET NINBER (2)
YEAR LER HlllBER (6)
SEOUEHTIAL NUHBER REVISION NUMBER PAGE '(3)
Browns Ferry Unit 2 05000260 95 005 00 3 of 5
TEXT If more s ce is r uired use additional co ies of(17) following the completion of corrective maintenance and post-maintenance testing.
TVA exited the 7-day LCO.
TVA is reporting this event in accordance with 10 CFR 50.73(a)(2)(v) as an event or condition that alone could have prevented'he fulfillment of the safety function of a structure or system that is needed to mitigate the consequences of an accident.
B ~
Ino erable Structures Com onents or S stems that Contributed to the Event:
C ~
None.
Dates and A
roximate Times of Ma'or Occurrences:
June 7,
1995, at 1836 CDT HPCI steam supply valve hesitates to open and HPCI turbine trips on overspeed June 7,
1995, at 2050 CDT HPCI declared inoperable retroactive to 1836 hours0.0213 days <br />0.51 hours <br />0.00304 weeks <br />6.98598e-4 months <br />; TVA enters a
7 day LCO June 7,
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)(iii)
D ~
E ~
June 8,
1995, at 1140 CDT HPCI operable, exit 7-day LCO Other S stems or Secondar Functions Affected:
None.
Method of Discover Personnel futility, nonlicensed) in the vicinity of the HPCI turbine observed the turbine stop and turbine control valves cycle open with no turbine start.
When steam was admitted, personnel heard the turbine overspeed.
Additionally, when the turbine tripped on overspeed, the Unit 2 operator (utility, licensed) received control room alarms and indications that an overspeed event had occurred.
F ~
0 erator Actions:
None.
II
NRC FOHN 366A (5-92)
U.S.
NUCLEAR REGULATORY CCHHISSIOH LICENSEE EVENT REPORT TEXT CONTINUATION APPROVED BY W 40. 3150-0104 EXPIRES '/31/95 ESTIHATED BURDEN PER
RESPONSE
TO COHPLY WITH THIS INFORHATIOH COLLECTIOH REQUEST:
50.0 HRS.
FORWARD COHHENtS REGARDIHG BURDEN ESTIHATE TO
'tHE INFORHATION AND RECORDS HANAGEHEH'I BRANCH (HNBB 77'l4),
U.S.
NUCLEAR REGULATORY CONNISSIOH, WASHINGTON'C 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104),
OFFICE OF HANAGEHENT AHD BUDGEl',
WASHINGTON DC 20503 FACILITY NAHE (1)
Browns Ferry Unit 2 DOCKET HWBER (2) 05000260 YEAR 95 LER NIHIBER (6)
SEQUENT IAI.
NUHBER 005 REVISION NUHBER 00 PAGE (3) 4 of 5
TEXT If more s ce is r ired use sdditionsI co ies of(17)
G.
Safet S stem Res onses:
None.
III'AUSE OF THE EVENT A.
Immediate
Causes
The immediate
cause of the event
was the failure of the HPCI steam supply valve to open during the initial start of the flow test.
B.
Root Cause:
This event resulted from a failure of the valve operator 250V DC open contact [RLY) to seal-in.
The root cause of the event was a
random failure of the contacts.
TVA's investigation has determined both the open and close seal-in contacts were pitted and indicated signs of arc deposits.
The steam supply valve was successfully opened and closed without incident just prior to the event and again during the second attempt to run the flow SI.
C.
Contributin Factors:
None.
IV.
ANALYSIS OF THE EVENT
The HPCI system is provided to ensure that the reactor is adequately cooled to limit fuel cladding temperature in the event of a small line break in the nuclear system and loss of coolant which does not result in rapid depressurization of the reactor vessel.
The HPCI system permits the plant to be shut down while maintaining inventory until the reactor vessel is depressurized.
Technical Specifications allow continued operation for up to seven, days if HPCI is inoperable provided the Automatic Depressurization [SB), Core Spray [SM), Residual Heat Removal [BO) in the low pressure injection mode, and Reactor Core Isolation Cooling [BN) systems are operable.
During the event, these systems were operable and would have performed their required function if called upon.
It should also be noted that the HPCI system's safety function was not degraded during the event.
HPCI design is such that during an automatic initiation from an accident signal the initiation logic bypasses the open seal-in circuit on the steam supply valve.
Therefore, TVA expects the valve would have opened since it would not
Ik
,t
NRC FORN 366A (5-92)
U.S NUCLEAR. REGULATORY. CQNIISSION LICENSEE EVENT'EPORT TEXT CONTINUATION APPROVED BY (WB NO. 3150-0104 EXPIRES 5/31/95 ESTINATED BURDEN PER RESPOHSE TO CONPLY WITH THIS IHFORHATION COLLECTION REQUEST:
50.0 HRS.
FORWARD COHNENTS REGARDIHG BURDEN ESTINATE TO THE INFORHATIOH AND RECORDS HAHAGEHENT BRANCH (HHBB 7714),
U.S.
NUCLEAR REGULATORY CONHISSION, WASHINGTON, DC 20555.0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150.0104),
OFFICE OF NAHAGEHENT AHD
- BUDGET, WASHINGTON DC 20503 FACILITY MANE (1)
Browns Ferry Unit 2 DOCKET NNIBER (2) 05000260
'YEAR 95 LER NUHBER (6)
SEOUENTIAL NUMBER 005 REVISION HUNGER 00 PAGE (3) 5 of 5 TEXT tf more s ce is r ired use sdditionsi co ies of NRC Form 366A (17)
V.
have relied on the open seal-in circuit.
Accordingly, the safety of the plant, its personnel, and the public was not compromised.
CORRECTIVE ACTIONS
A.
Immediate Corrective Actions
TVA issued a maintenance work order to investigate and determine the cause of the steam supply valve failing to open on the initial attempt.
TVA identified pitted contacts with indications of arc deposits on the seal-in contacts.
The contacts were cleaned and the steam supply valve was stroked several times with no problems identified.
TVA also reviewed the preventive maintenance requirements for the seal-in contacts and found the requirements adequate.
B.
Corrective Actions to Prevent Recurrence:
Since Unit 2 restart in May of 1991, TVA has not experienced any problems with these contactors.
Nevertheless, TVA plans to inspect these contactors within the next two months for signs of degradation.
VI ~
ADDITIONAL INFORMATION
A.
Failed Com onents:
None.
B.
Previous LERs on Similar Events:
VII.
TVA has previously issued LERs for inoperable HPCI due to various design and equipment concerns.
However, there have been no previous LERs identified in which the steam supply valve failed to open due to the random failure of a seal-in contactor.
COMMITMENTS
The action described in Section V of this report is not a regulatory
commitment
That is, it is not an action required to restore compliance with an obligation.
Obligations are actions that are legally binding requirements imposed through applicable rules, regulations,
- orders, and licensees.
Energy Industry Identification System (EIIS) system and component codes are identified in the text with brackets (e.g.,
(XX)).
0