05000328/LER-1997-001, :on 970117,missed Surveillance on Auxiliary Contacts of Reactor Trip Breakers Discovered.Caused by Adequate PMT for Reactor Trip Breaker Was Not Performed. Multi-disciplinary Team Formed to Perform Investigation
| ML20211M879 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 10/06/1997 |
| From: | Gilley S TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20211M876 | List: |
| References | |
| LER-97-001, LER-97-1, NUDOCS 9710150170 | |
| Download: ML20211M879 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2) |
| 3281997001R00 - NRC Website | |
text
NRC F'ORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPRLVED BY OM8 No. 3150-0104
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S::quoyah Nuclear Plant (SON) Unit 2 05000328 1OF8 TITLE (?)
Missed surveillance on the auxiliary contacts Of the reactor trip breakers.
EVEllT DATF fE1 iER NUumen g gi ggpORT BATF 7l OTHER FAPiiITIFR INVOLVFD fR1 MONTH DAY YEAR YEAR SEQUENTIAL REV!SION MONTH DAY YEAR FAclWTY NAME DOCKET NUMBER NUMBER NUMBER Sequoyah. Unit 1 05000327 FACluTY NAME DOCKET NUMBER 01 17 97 97 001 01 10 06 97 NA OPERATING j
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IIrJNRFF PnNTAET FOR THIR LFR fi91 NAME TELEPHONE NUMBER Unclude Area Codel St:vo D. Gilley, Ucensing Engineer (423) 843-7427 COM9 TETE ONF t IMF F SR F APH MAJ DnNFMT FAI tlRF nF#cRIRFn IN THIR REPORT f1M1
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ABSTRACT (Limit to 1400 spaces, Le.. approximately 15 single-spaced typewntten lines) (16)
On January 17, 19s7, with Unit 2 in power operation at'approximately 100 percent, personnel discovered that the spare breaker installed on August 29, 1996, did not have the P-4 turbine trip contact tested as required by SR 4.3.1.1.1.C.22.G.
A second problem was also discovered where the post maintenance test (PMT) procedure used for the replacement of reactor trip breaker "A" (RTA) on August 29, 1996, was inadequate. The procedure only tested the solid state protection system (SSPS) functions of P-4 with the breaker in the as-left position, rather than testing in both the open and closed positions as required to satisfy the surveillance.
However, the surveillance was satisfied when the breaker was tested in the closed position during a forced outage on October 17, 1996.
In order to perform the necessary tests for the turbine trip contacts on RTA, Unit 2 entered TS LCO 4.0.3 at 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br /> Eastern Standard Time (EST) on January 17, 1997. The required testing for the turbine trip contacts was performed, RTA was declared operable, and LCO 4.0.3 was exited at 1249 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.752445e-4 months <br /> EST on January 18, 1997 Discovery of thic problem has resulted in the discovery of several other instances in the past where SQN was in noncompliance with SR 4.3.1.1.1.C.22.G.
The root cause was a lack of understanding of the design basis definition.of P-4 and of the surveillance requirements necessary to return reactor trip breakers to operable status.
9710150170 971006 PDR ADOCK 05000328 S
PDR NRC IORM 366 (4-95)
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j NRC FOfiM 366AU.S. NUCLEAR REGULATORY COMMISSION (4-95)
LICENSEE EVENT REPORT (LER)
- - TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL NUMBER REVI$loN NUMBER SQN Unit 2 05000328 2 of 8 g
97 001 01 1
1 TEXT Of more space is required, use additional copies of NRC Form 366Al (17) i I.
PLANT CONDITIONS
4 Unit 2 was in power operation at approximately 100 percent.
Unit 1 was also in power operation at approximately 100 percent.
II.
DESCRIPTION OF EVENT
A.
Event i
On January 17, 1997, Unit 2 was in power operation at approximately 100 percent.
Personnel discovered that a breaker [EIIS code BKR) installed on August 29, 1996, in the RTA cubicle did not have the i
P-4 turbine trip contact tested as required by Surveillance 1
Requirement (SR) 4.3.1.1.1.C.22.G.
Unit 2 entered Technical l
Specification (TS) Limiting condition for Operation (LCO) 4.0.3 at 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br /> EST, on January 17, 1997, and the required testing for the turbine trip contacts for RTA was performed.
RTA was declared
{
operable, and operators exited LCO 4.0.3 at 1249 EST on l
January 18, 1997.
In addition, the post maintenance test (PMT) used l
for the online replacement of RTA on August 29, 1996, was inadequate.
It did not test the Solid State Protection System j
(SSPS) functions of P-4 with the breaker in both the open and closed positions as required (note that P-4 performs a TS required function i
with the breaker in both the open and closed positions). As directed by the procedure, the P-4 functions of the breaker were only tested with the breaker in the as-left position, which in this J
event resulted in P-4 only being tested with the breaker closed.
However, the breaker was tested in the open position during a forced outage on October 17, 1996.
Therefore, from August 29, 1996, until Octaber 11, 1996, when the unit entered the forced outage, the SSPS functions of P-4 were inoperable because they had not received the necessary testing to meet the surveillance requirement.
. Additional investigation has revealed that the condition where the surveillance instructions did not satisfy the surveillance requirements for the entire P-4 interlock function for SSPS that was reported in Revision 0 of this LER has existed since 1980.
In June of 1980, procedures were revised resulting in the P-4 contacts for SSPS only being tested in the as-left position.
1 i
1 i
2 NQC FORM 3E6A (4 95) 7
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i' LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL NUMBER REVISloN NUMBER SQN Unit 2 05000328 3 of 8 97 --
001 01 TEXT tif more space is required, use odd tional copies of NRC Form 366A) (t h a
The root cause consisted of two elements:
(1) A lack of a
understanding of the design basis definition of the P-4 interlock and subsequent fallare to satisfy the surveillance requirements during initial development of the surveillance instruction program, and (2) A lack of understanding of the surveillance requirements for operability following reactor trip breaker maintenance.
1 A contributing factor was that procedures did not require the work package to differentiate between testing for maintenance and testing to satisfy surveillance requirements prior to equipment return to operability.
Unit I reactor trip breakers had not been replaced on-line and j
therefore were not affected by the issues described in this report.
B.
IJ}onerable Structures, Components, or Systews that Contributed to the Event The P-4 function from RTA to trip the turbine on reactor trip was inoperable from August 29, 1996, when the spare breaker was insta' led until January 17, 1997, when LCO 4.0.3 was entered and the l
required testing to satisfy the 18-month requirement was performed.
i The SSPS functions of P-4 on RTA were inoperable from August 29, 1996, until a forced outage began on October 11, 1996.
t The SSPS functions of P-4 were tested during the forced outage with the-breaker in the open position, which completed the necessary 4
j, testing to satisfy the surveillance requirement.
C.
Dates and Acoroximate Times of Maior Occurrences i
August 29, 1996 The breaker was removed from the. "A" l
location on Unit 2 and replaced with the l
spare breaker while the unit was online.
The PMT (SI-90.82) was inadequate because it only tested P-4 to SSPS contact with the breaker in the as-left (closed) position and it did not test the turbine trip function of P-4.
The P-4 function for the breaker installed in location "A" was inoperable.
l This condition was discovered on January 17, 1997, and was reported in LER 50-328/97001, Revision 0.
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l LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION
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FACILITY NAME-(1)
DOCKET LEA NUMBER.(6)
PAGE (3)
YiAR SEoUENTIAL NUk18ER REVIStoN NUMBER SQN Unit 2 05000328 4 of 8 97 --
001 01 1
TEXT of more space is requires. use auctional copies of NRC Form 366A) Oh i
i l
P October 11, 1996 Unit 2 shut down for forced outage.
14 ode 3 with breakers open, j
October 17, 1996 SI-90.82 performed on the breaker in the "A"
l location with the breaker in the open position.
l October 19, 1996 SI-93 (Reactor Trip Instrumentation e
Functional Test Conditional 31 Days Prior to i
Startup) completed for breakers in locations l
"A" and "B" ca Unit 2.
j January 17, 1997 investigation revealed that Section 6.0 of j
mI-10.9.1 (which included contact checks) had been performed for Unit 2 RTA in 1994 which was outside the required 18-month 4
frequency; therefore, the breaker was i._
Unit 2 entered TS LCO 4.0.3 at 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br /> EST.
January 18, 1997 The turbine trip P-4 contacts were checked, at 1249 EST and reactor trip breaker "A" was declared i
LCO 4.0.3 was exited for Unit 2.
t l
D.
Other Systems or Secondary Functions Affected
1 The following functions are performed by P-4 with the breaker opent actuates turbine trip, closes main feedwater valvos on Tavg below setpoint, prevents the opening of the main feedwater valves which were closed by a SI or high steam generator water level signal, and allows manual block of the automatic reactuation of SI.
Since P-4 i
was only tested with the breaker closed, the functions listed above l
were not' verified. When the breaker is in the_ closed position, P-4 l-defeats the manual block preventing automatic reactuation of safety injection.
However, on October 17, 1996, these functions, except turbine trip, were tested for RTA with the breaker open; and the turbine trip 1-function was tested on January 18, 1997.
In both cases, the tests showed that these contacts would have operated as designed if called upon to do so, i
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LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE - (3 )
YEAR 6EQUENTIAL NUMBER REVISION NUMBER SQN Unit 2 05000328
$ of 8 97 --
001 01 TEXT or more space is required. use soditiorsei copies et Nac Form 366At it71 E.
Method of DiscoygIy The problems described in the LER were discovered as a result of the ongoing investigation that was conducted in response to a previous problem with a linkage in the reactor trip breaker that was not installed properly and was not uiscovered by the PMT.
Refer to LER 50-328/96004.
F.
Ooorator Actions On January 17, 1997, at 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br /> EST, Unit 2 entered TS LCO 4.0.3 for RTA when it was discovered that the 18-month SR for P-4 to the turbine trip had not been met for this breaker.
The surveillance was performed and the breaker was returned to service on January 18, 1997.
G.
Safety System Resoonses No safety system response was required.
III. CAUSE OF THE EVENT
A.
Immediate Cau.33 The immediate cause of this condition was that an adequate PMT for the reactor trip breaker was not performed.
This invalidated the SR fer periodic verification of the P-4 function.
- - B.
Root Caggg The root cause consisted of two elements:
(1) A lack of understanding of the design basis definition of the P-4 interlock and subsequent failure to satisfy the' surveillance requirements during initial development of-the surveillance instruction program, and (2) A lack of understanding of the surveillance requirements for operability following reactor trip breaker maintenance.
C.
Contributina Factors Procedures did not require the work package to differentiate between testing for maintenance and testing to satisfy SRs prior to equipment return to operability.
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7 LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION 4
4 FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL NUMBER REVISloN NUMBCR l
SQN Unit 2 05000328 6 of 8 97 ---
001 01 1
TEXT tif more space is reewed, use additgmal copies of NRC Form 366A) (1M i-l IV.
ANALYSIS OF THE EVENT
y.
The inoperability of the P-4 contacts identified in this LER was due j.
strictly to a missed surveillance and not to contacts that were _
j incapable of performing their design function.
Since the contacts were i
later tested and found to function properly with normal contact 4
resistance, it is reasonable to assume the contacts were functional the day the breaker was changed. Also, since the P-4 channel is strictly a switch development, the extended surveillance intecval does not subject the P-4 function to drift or accuracy degradation.
The main liability l
of not testing the P-4 contacts when a new breaker is installed-is that a failure of the auxiliary switch would not be immediately identified i
(reference LER 50/328-96004). The successful completion of testing on reactor trip breaker "A" on Januaaj 17, 1997, demonstrated that the P-4 contacts would have functioned if called upon to do so.
Therefore, based on the above considerations, there were no adverse consequences to i,
plant personnel or to the public as a result of this event, i
V.
CORRECTIVE ACTIONS
1 j_
A. Immediate Corrective Actions
d j.
A multi-disciplinary team was for.ned to perform an investigation of the event.
That investigation is complete and was responsible for the identification of the events described by this report as well as development of corrective actions.
An evaluation was performed on the Unit 2 RTB that had been replaced on October 16, 1996.
The surveillance requirements for this breaker were satisfied through the performance of PMs that were completed within the 18-month surveillance interval.
Unit 2 entered TS LCO 4.0.3 on January 17, 1997, at 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br /> EST, when it was discovered that the 18-month SR for P-e to the turbine trip had not been m*c for this breaker. The instructions necessary to satisfy the surveillance were written and performed and-the unit exited LCO 4.0,3 at 1249 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.752445e-4 months <br /> EST, on January 18, 1997.
SI-90.8, " Reactor Trip Instrumentation Monthly Functional Test (SSPS)," for Unit 1 has been revised to test the P-4 to SSPS contact with the reactor trip breaker open and closed.._ _
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMERR (6)
PAGE (3)
YEAR SEQUENTIAL NUMBER REVISloN NUMBER SQN Unit 2 05000328 7 Of
- 97 --
001 01 TEXT ut more space to required. use ed4tsmal cop +a of NRC Form 366A) (1h B.
Corrective Actions to Prevent Recurreqqa SI-90.82, " Reactor Trip Instrumentation Monthly Functional Test (SSPS)," for Ur.it 2 has been revised to test tne P-4 to SSPS contact
)
with the reactor trip breaker open and closed.
SI-93, " Reactor Trip Instrumentatien Functional Test Conditional 31 Days Prior to Startup," has been revised to test the P-4 to SSPS contact with the reactor trip breakers open and closed.
A new procedure was developed to adequately test a reactor trip breaker or bypass breaker following breaker maintenance or replacement which satisfies all SR criteria.
The procedure was revised to require that work order PMTs are structured into two parts, 1) for maintenance tests and 2) for return to operability.
An Operations responsibility was established for return to operability planning.. Operations reviews work orders to specif. the sis required to be performed to ensure TS SRs are met.
The requirements for individuals performing this task include currently holding.or having held a Senior Reactor Operator (SRO) license at SQN.
TVA is conducting a training class to teach the functional definition of the reactor trip breaker P-4 interlock circuit including testing methodology, TS LCO applicability, and SR applicability, This training also includes the TS LCOs and SRs related to the reactor trip breakers.1 The effectiveness of this training will be reviewed using feedback from personnel that i
complete the training.
i In the reply to Notice of Violation 50-328/97-03-04 dated June 11, 1997, TVA also committed to revise procedures to require an evaluatic-n c' TS requirements when an outage activity is deferred to onl?ne maintenance, and to revise procedures to include a matrix of SRs that must be met for return to operability for specific maintenance tasks.
1 TVA does not consider this corrective action a regulatory commitmr t.
TVA's corrective action program will track completion-of the activ.a.l
...s*
LICENSEE EVENT REPORT (LER) l TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR SEQUENilAL NUMBER REVISloN NUMBER SQN Unit 2 05000328 8 of 8 97 001 01 TEXT ut more space es reawed, use edditional copies of hac f orm 36eA) o n VI.
ADDITIONAL INFORMATION
A.
Failed Componenta None.
B. Previous LERs on Similar Events A review of previous reportable events identified a Unit 2 LER (50/328-86039) that documented a condition where two of the five functions that P-4 accomplishes were not being checked to satisfy 50 4.3.1.1.2.
These two functions were turbine trip and main feedwater valve closure on low reactor coolant system average temperature with reactor trip.
The corrective action from that event included writing a new procedure to test the total interlock function.
The procedure that was written tested the turbine trap portion of P-4, but the procedure was written to be performed during refueling outages. When online maintenance of the breakers was performed, the specified PMT did not test the turbine trip feature.
VII.
COMMITMENTS
None.
T9