05000327/LER-1997-002-01, :on 970214,TS AOT Exceeded for DG 2A-A.Caused by Mechanical Failure of DG 2A-A Governor Actuator on Engine 2.DG 2A-A Governor Actuators on Both Engines Replaced, Functional Tested & PMT Performed
| ML20137A453 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/13/1997 |
| From: | Proffitt J TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20137A427 | List:
|
| References | |
| LER-97-002-01, LER-97-2-1, NUDOCS 9703200332 | |
| Download: ML20137A453 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 3271997002R01 - NRC Website | |
text
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 31504104 14 95)
EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 LICENSEE EVENT REPORT (LER)
Em"F I[CEEEMr* ROC $$ N" RED $![TO I Du"$YS FORWARD COMMENTS REGARDING BURDEN ESTIMATE To (See reverse fOr required number Of mE INFOFWlATION AND RECORDS MANAGEMENT BRANCH (T-digits / characters for each block) e F338, U.S. NUCLEAR REGULATORY COMMISSION, excluTV ftAME (4 DOCKET NUMBER (2)
PAGE (3) 1OF6 S quoyah Nuclear Plant (SON) Unit 1 05000327 TITLE (4)
Enforcement Discretion Granted When Problems With The 2A-A Diesel Generator Actuator was identified.
EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7l OTHER FACILITIES INVOLVED (8)
SEQU T AL R
N MONTH DAY YEAR YEAR MONTH DAY YEAR N
R
" "^"'
2 14 97 97 -- 002 --
00 3
13 97 000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or more) (111 g
MODE (9) 20.2201(b) 20.2203(a)(2)M X
50.73(aH2>0) 50.73(a)(2)(viii)
POWER 20.2203(amu 20.2203(aH3Hn 50.73(aH2Hu) 50.73(aH2Hx) 100 LEVEL (10) 20.2203(aH2HO 20.2203(aH3Hn) 50.73(aH2)hii) 73.71 20.2203(aH2Hii) 20.2203(aH4) 50.73(aH2 Hiv) oTHER 20.2203(aH2>0u) 50.35(c)(1) 50.73(aH2)(v)
Specify in Abstract below
^
20.2203(aH2)bvl 50.36(cH2) 50.73(a)(2)(vii)
LICENSEE CONTACT FOR THIS LER (12)
NAMl!
TELEPHOhi, NUMBER (include Area Code)
J. W. PrOffitt, Licensing Engineer (423) 843-6651 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
REPORTAB E R
^L
CAUSE
SYSTEM COMPONENT MANUFACTURER
CAUSE
SYSTEM COMPONENT MANUFACTURER O NPRDS X
EK 65 W290 Y
SUPPLEMENTAL REPORT EXPECTED (141 MONTH DAY YEAR EXPECTED YES SUBMISSION X
NO (if yes, complete EXPECTED SUBMISSION DATt:s.
DATE (15)
ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewntten lines) (16)
On February 14,1997, at 1725 eastern standard time (EST), the technical specification allowed outage time was exceeded for Diesel Generator 2A-A. On Febmary 11 and 12,1997, while performing planned testing on the 2A-A D/G, low megger readings and low polarization index readings were identified on the "C" Phase D/G stator winding. Cleamng of cables and connections could not achieve an acceptable polarization index value. The generator pigtail msulation was identified as the source of the dielectric breakdown. Replacement and testing of the generator pigtails was completed within the allowed outage time. At the end of the post maintenance testing for the generator pigtail repairs, a degraded performance of the 2A2 engine governor actuator was noted. The root cause was the mechanical failure of the D/G 2A-A governor actuator on engine
- 2. Before exceeding the technical s ecification allowed outage time, enforcement discretion of technical specification LCO 3.8.1.1 Action (b was received. The 2A-A D/G governor actuators on both engines were replaced. A functional test and PM were performed and the D/G was declared operable.
9703200332 970313 PDR ADOCK 05000327 S
PDR NRC FORM h6 (4-95)
jLICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER l REVISION NUMBER SQN Unit 1 05000327 97 --
002 00 IEXT Uf more space is required, use additional copies of NitC form 360A} (17)
I.
PLANT CONDITIONS
Units I and 2 were in power operation at approximately 100 percent.
II.
DESCRIPTION OF EVENT
A.
Es ent:
On February 14,1997, at 1725 eastern standard time (EST), the technical specification allowed outage time was exceeded for Diesel Generator 2A-A (Ells Code EK). On February 11 at 1725 EST Technical Specification Limiting Condition for Operation (LCO) 3.8.1.1 was entered for planned testing on the 2A-A D/G. Low megger readings and low polarization index readings were identified on the "C" Phase D/G stator winding. Cleaning of the cables and connections could not achieve an acceptable polarization index value. The 'C' phase lineside generator pigtail insulation was identified as the source of the dielectric breakdown. Replacement and testing of the generator pigtails was completed within the allowed outage time. At the end of the post maintenance testing for the generator pigtail repairs, a degraded performance of the 2A2 engine governor actuator was noted. The original maintenance activity was planned and scheduled for completion within the 72-hour technical specification LCO allowed outage time.
Before exceeding the technical specification allowed outage time, enforcement discretion of technical specification LCO 3.8.1.1 Action (b) was requested. The request was initiated when a problem was identified during performance of the PMT with the D/G governor actuator, which made meeting the LCO action statement time requirements unattainable. The request for an additional allowed outage time of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> was granted by NRC. The failed actuator and the actuator on the tandem engine were replaced. D/G 2A-A was subsequently l
declared operable at 1330 EST on February 15,1997.
l l
B.
Inonerable Structures. Components. or Systems that Contributed to the Event:
None.
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER l REVISION NUMBER j
SQN Unit 1 05000327 97 002 00 rEXT Ut more space is required, use additional copies of NRC Form 366A) (17)
C.
Dates and Aporosimate Times of Maior Occurrences:
February 11,1997 LCO 3.8.1.1 action (a) was entered for D/G 2A-A outage to at 1725 EST perform maintenance activities. These activities included testing of the "C" phase stator winding cables. Low megger readings and low polarization index readings were identified on the "C" Phase D/G stator winding. The generator pigtail insulation was identified as the source of the dielectric breakdown.
February 12,1997 Replacement and testing of the generator pigtails was completed.
1 at 1742 EST February 13,1997 The govemor actuator difference annunciator for the 2A-A D/G at 1912 EST was received in the main control room during performance of the PMT. The turbocharger inlet temperature for the two engines had a temperature differential of greater than 200 degrees Fahrenheit.
February 15,1997 Replacement of the 2A-A D/G governor actuators was completed at 0135 EST on both 2A-A D/G engines and the functional test was started.
February 15,1997 D/G 2A-A successfully passed the PMT and was declared at 1330 EST operable.
D.
Other Systems or Secondary Functions Affected
None.
E.
Method of Discoverv:
The condition was identified during performance of the PMT following maintenance activities on the 2A-A D/G.
F.
Operator Actions
Main Control room personnel entered the appropriate technical specification LCOs._._ - - -
i LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER l REVISION NUMBER SON Unit 1 05000327 97 --
002 00 rEXT tif more space is required, use additional copies of NRC Form 366A) (14 G.
Safety System Responses:
No safety system responses were required for the condition identified.
III.
CAUSE OF TIIE EVENT A.
Immediate Cause:
The immediate cause of the condition was that D/G 2A-A could not be returned to service within the technical specification allowed outage time because of the time to resolve the emergent problem with the governor.
H.
Root Cause:
The root cause was the failure of the D/G 2A-A governor actuator. The actuator pilot plunger cylinder had a blister or bubble near the bottom of the housing.
This blister caused the transducer magnet to stick during operation that in turn controls the electronic pilot valve. The electronic pilot valve moved slowly, this in turn caused the output terminal shaft position to respond slowly.
C.
Contributing Factors None.
IV.
ANALYSIS OF TIIE EVENT 1
The operability of the AC power sources during plant operation ensures power availability to safety-related equipment for the safe shutdown of the facility and the mitigation and control of accident conditions within the facility. Four separate and independent D/G sets are required to be operable. Electric power to SQN is supplied by two physically and electrically independent circuits from the SQN switchyard to the electrical distribution system. The switchyard is designed with two main bus sections and arranged so that the supply to the onsite power system is maintained to one bus l
section for a failure of the other section. In the unlikely event of a loss of oiTsite power, l
the redundant train capability was available for all functions.
--~~ -~.
~
E 4,
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER l REVISION NUMBER SON Unit 1 05000327 97.-
002 00 FEXT Ut more space is required, use additional copies of NRC Form 366As (17) 1 The increased risk for having the 2A-A D/G out of service for an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> is j
considered low based on the change in mean core damage probability. The change in i
mean core damage probability was determined to be at the lower range of non-risk significant category.
Therefore, the condition did not adversely affect the health or safety of plant personnel or the general public.
V.
CORRECTIVE ACTIONS
A.
Immediate Corrective Actions
Upon determination of the condition, appropriate LCOs were entered, and testing of the other D/Gs was performed in accordance with TS Action 3.8.1.1.b.
Compensatory measures to perform Surveillance Requirement 4.8.1.1.a every four hours (eight hour frequency is required by TSs) was taken. Actions were taken to protect the B-train components and engineered safety features equipment, other than that needed to support any testing of the 2A-A D/G, while the 2A-A D/G was out of service. Operators were provided training for contingency plans to cross connect electrical loads during a loss of offsite power emergency. Further, the switchyard was protected to ensure offsite power supply reliability.
B.
Corrective Actions to Prevent Recurrence:
The 2A-A D/G governor actuators were replaced on both engines. A functional test and PMT were performed and the D/G was declared operable.
VI.
ADDITIONAL INFORMATION
A.
Failed Comnonents:
The component that failed was a Woodward governor Type EGB 13P Part Number 9903-138 and Serial Number 1072051.
1
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- .LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER l REVISION NUMBER SQN Unit 1 05000327 97 --
002 00 IEXT (if more space la required, use additional copies of NRC Form 366A) (17) 1 H.
Previous LERs on Similar Events:
A review of previous reportable events identified one LER (50-327/94016) that included enforcement discretion on the D/G allowed outage time. The corrective actions described in that LER could not have prevented this event.
VII.
COMMITMENTS
None.
I