05000391/LER-1917-002, Regarding Manual Reactor Trip as a Result of a Secondary Plant Transient
| ML17132A267 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 05/12/2017 |
| From: | Simmons P Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 17-002-00 | |
| Download: ML17132A267 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2) |
| 3911917002R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 May 12,2017 10 cFR 50 73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unat 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391
Subject:
Licensee Event Report 39112017-002-00, Manual Reactor Trip as a Result of a Secondary Plant Transient This submittal provides Licensee Event Report (LER) 39112017-002-00. This LER provides details concerning a manual reactor trip that was performed after the loss of several secondary plant pumps. This report is being submitted in accordance with 1 0 cFR 50.73(a)(2)(ivXA).
There are no regulatory commitments contained in this letter. Please direct any questions concerning this matter to Kim Hulvey, WBN Licensing Manager, at (423) 365-7720.
Respectfully, Paul Simmons Site Vice President Watts Bar Nuclear Plant Enclosure cc: See Pag e 2
U.S. Nuclear Regulatory Commission Page 2 May 12,2017 cc (Enclosure):
NRC Regional Administrator - Region ll NRC Senior Resident lnspector - Watts Bar Nuclear Plant
NRC FORM (06-2016)
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{a^Lffi 366 U.S, NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
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- 1. FACILITY NAME Watts Bar Nuclear Plant, Unit 2
- 2. DOCKET NUMBER 0500039 1
- 3. PAGE 1
of 5
- 4. TITLE Manual Reactor Trip as a Result of a Secondary Plant Transient
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTHI DAY I YEAR YEAR I ttir',f#Jf' REV NO MONTH I DAY YEAR FACILITY NAME I
oocxET NUMBER 03 20 I 2017 2017 - 002 00 05 12 2017 FACITITY NAME I oocxrr NUMaER
- 9. OPERATING MODE
- 11. THIS REPORT lS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR g: (Checkatt thatapply) 1 tr zo 2201 (b) tr zo zzo3(aX3Xi) tr 50 73(aX2XiiXA) tr 50 73(a)(2)(viiixA) tr zo 2zo1 (d) tr 20 zzo3(aXsXii) tr 50 73(aX2XiiXB) n 50 73(a)(2XviiixB) f 20 zzo3(a)(1) n 20 2zo3(aX4) n 50 73(ax2xiii) tr 50 73(a)(2)(ix)(A) tr zo zzo3(a)(2Xi) tr 50 36(cxl XIXA)
X 50 73(aX2XivXA) tr 50 73(aX2Xx)
- 10. POWER LEVEL 91 tr zo 2zo3(aX2Xii) tr 50 36(cX1)(iiXA) tl 50 73(a)(2xv)(A) tr n 71 (aX4)
X zo zzo3(aX2)(iii) tr 50 36(c)(2) tr 50 73(aX2)(v)(B)
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23 71 (aX5) tr 20.2za3(a)(2Xiv) tr 50 46(ax3xii) tr 50 73(aX2XvXC) tr nrr(a)(1) tr 2o.z2o3(aX2Xv) tr 50 73(a)(2XiXA) tr 50 73(aX2Xv)(D) tr fi 77(aX2Xi) tr zo zzo3(aX2Xvi) tr 50 73(aX2XiXB) tr 50 73(a)(2)(vii) tr ft TT(aX2Xii) tr 50 73(ax2xi)(c)
X OTHER Specify in Abstract betow or in
E. Other Systems or Secondary Functions Affected
The inadvertent trip of the 2A Hotwell pump led to multiple secondary system pump trips on loss of NPSH.
F. Method of discovery of each Component or System Failure or Procedural Error
The inadvertent trip of the 2A Hotwell pump was discovered after the trip based on interviews with plant personnel.
G. Failure Mode and Effect of Each Failed Component No components failed during this event.
H. OperatorActions With SG levels lowering as a result of lost secondary pumps, operations personnelcommenced a rapid load reduction and established a manualtrip criteria based on SG level. SG levels were recovering when the 28 Condensate Booster pump was lost. With lowering SG levels the reactor was manually tripped above the SG low levelalarm.
l. Automatically and Manually lnitiated Safety System Responses The reactor was manually tripped and the AFW system automatically actuated. All safety systems operated as expected.
III. CAUSE OF THE EVENT
A. The cause of each component or system failure or personnel error, if known.
The plant trip was a result of scaffold workers inadvertently depressing the local trip pushbutton for the 2A Hotwell pump.
B. The cause(s) and circumstiances for each human performance related root cause.
The plant trip was a result of scaffold workers inadvertently depressing the local trip pushbutton for the 2A Hotwell pump. These workers did not display appropriate situationalawareness around trip sensitive equipment. Operations personnel did not establish proper controls for work being performed on WBN Unit 2 while WBN Unit 1 was in an outage.
IV. ANALYSIS OF THE EVENT
The inadvertent trip of the 2A Hotwell pump resulted in reduced suction head to downstream pumps, resulting in additional pump trips on low suction pressure. This resulted in reduced feedwater flow and lowering SG levels. Operations commenced a rapid downpower to address lowering SG levels, but Page 3 of
multiple pump trips led to the decision to manually trip the plant rather than wait for an automatic plant trip.
All safety systems operated as expected. While main feedwater isolated by design, it was recoverable using normal plant procedures. This trip is considered to be uncomplicated.
V. ASSESSMENT OF SAFETY CONSEQUENCES
The event resulted from an inadvertent trip of the 2A Hotwell pump, which led to other secondary pumps tripping due to a loss of NPSH. The resultant secondary plant transient required a manual plant trip. The event that occurred is bounded by the Loss of Normal Feedwater event described in the Final Safety Analysis Report (FSAR), which is considered an anticipated operational occurrence.
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event All safety systems operated as designed during this event.
B. For events that occurred when the reactor was shut down, availability of systems or components needed to shutdown the reactor and maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident Not applicable.
C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from the discovery of the failure until the train was returned to service All safety systems operated as designed during this event.
VI. CORRECTIVE ACTIONS
This event was entered into the Tennessee Valley Authority (TVA) Corrective Action Program and is being tracked under Condition Reports (CRs) 1274558,1274800, and 1275064.
A. lmmediate Corrective Actions Upon determining the nature of the human performance error, coaching was provided to site construction personnel related to situational awareness around trip sensitive equipment.
Additional controls were specified for field personnel working on an operating unit while the adjacent unit was in an outage.
B. Corrective Actions to Prevent Recurrence or to Reduce Probability of Similar Events Occurring in the Future Operations personnel were coached on the need to control work activities near operating equipment. Bump guard covers were installed on local pushbuftons for a number of secondary pumps in the turbine building to prevent inadvertent actuation.
age 5
VII. PREVIOUS SIMILAR EVENTS AT THE SAME SITE
A plant trip due to loss of main feedwater was reported to the NRC in LER 391/2016-005 dated August 19, 2016. This event was attributed to operations personnel failing to precisely control the plant, resulting in a loss of vacuum to the main feedwater pump condenser. The event described in this LER is differentin that it involved an inadvertent equipment contact by non-operations personnel.
VIII. ADDITIONAL INFORMATION
None.
IX. COMMITMENTS None.