05000391/LER-2016-006, Regarding Turbine Driven Auxiliary Feedwater Pump Auto Start on Lo-Lo Steam Generator Level Following Planned Unit Trip
| ML16281A423 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 10/07/2016 |
| From: | Simmons P Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 16-006-00 | |
| Download: ML16281A423 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| 3912016006R00 - NRC Website | |
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Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 October 7,2016 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001
Subject:
10 cFR 50 73 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391 Licensee Event Report 391/2016-006-00, Turbine Driven Auxiliary Feedwater Pump Auto Start on Lo-Lo Steam Generator Level Following Planned Unit Trip This submittal provides Licensee Event Report (LER) 391/2016-006-00. This LER provides details concerning a recent automatic start of the Turbine Driven Auxiliary Feedwater Pump after it had been manually secured by operations following a planned unit shutdown. This report is being submitted in accordance with 10 CFR 50.73(aX2)(ivXA).
Please direct any questions concerning this matter to Gordon Arent, WBN Licensing Director, at (423) 365-2004.
Respectfully, Paul Simmons Site Vice President Watts Bar Nuclear Plant Enclosure cc: See Pag e 2
U.S. Nuclear Regulatory Commission Page 2 October 7,2016 cc (Enclosure):
NRC Regional Administrator - Region ll NRC Senior Resident Inspector - Watts Bar Nuclear Plant
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (11-2015)
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APPROVED BY OMB: NO.3150.0104 EXPIRES: 10131/2018
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME Watts Bar Nuclear Plant, Unit 2
- 2. DOCKET NUMBER 0500039 1
- 3. PAGE 1
OF 5
- 4. TITLE Turbine Driven Auxiliary Feedwater Pump Auto Start on Lo-Lo Steam Generator Level Following Planned Unit Trip
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTHI DAY I YEAR YEAR I t=-t'r=JJS'-
REV NO.
MONTH !
DAY YEAR FACILITY NAME I
DOCKET NUMBER N/A lr*rn 08 13 I 2016 2016 -006
- - 00 10 7
2016 FACILITY NAME I
DOCKET NUMBER N/A
!r.rn
- 9. OPERATING MODE I 1. THIS REPORT lS SUBi/IITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR S: fCheck all that apply) 3 tr zo.22o1(b) tr zo.2zos(aX3Xi) tr 50 73(a)(2xii)(A) t] 50.73(a)(2XviiiXA) tr 20.2201(d) tr 2o.z2os(aX3Xi.)
tr 50.73(aX2XiiXB) t] 50.73(aX2XviiiXB) tr 2o.22os(aX1) tr 2o.z2o3(a)(4) tr 50.73(ax2xiii) tr 50.73(aX2)(ixXA) tr 20.2203(aX2)(D tr 50.36(cXlXiXA)
X s0.73(aX2)(ivXA) tr 50.73(aX2Xx)
- 10. POWER LEVEL tr zo.zzos(aX2XiD tr 50.36(c)(l XiiXA) tr 50.73(aX2XvXA) tr rs.t1(aX4) tr zo.22o3(aX2Xiii) tr 50.36(c)(2) tr 50.73(aX2XvXB) tr 13.11(aXs) n zo.zzo3(aX2Xiv) n 50.46(ax3xii) tr 50.73(aX2XvXc) n Ts.rr(a)(1) tr zo.z2o3(aX2Xv) tr 50.73(aX2Xi)(A) tr 50.73(aX2XvXD) tr ft.rt(ax2xi) tr zo.2zos(a)(2)(v.)
tr 50.73(aX2XiXB) tr 50.73(aX2Xvii) n B.7T(aX2Xii) tr 50.73(ax2)(ixc) tr OTHER Specify in Abstract below or in D. Manufacturer and Model Number of Components that Failed Not applicable.
E. Other Systems or Secondary Functions Affected
None.
F. Method of discovery of each Component or System Failure or Procedural Error
The error became apparent after the automatic start of the TDAFW pump.
G. Failure Mode and Effect of Each Failed Component Not applicable.
H. Operator Actions
Following automatic start of the TDAFW pump, SG levels were raised above the TTD setpoint of 17 percent. The TDAFW pump was then re-secured.
l. Automatically and Manually lnitiated Safety System Responses All automatic and manual safety systems responded as expected.
III. CAUSE OF THE EVENT
A. The cause of each component or system failure or personnel error, if known.
No component failures caused this event.
B. The cause(s) and circumstances for each human performance related root cause.
This event was the result of a human performance error. The cause of the event was a failure to brief the auto start feature of the TDAFW pump at Lo-Lo SG water level of 17 percent when briefing the control band for the SGs is between 6 to 50 percent.
IV. ANALYSIS OF THE EVENT
Wafts Bar Unit 2 lowered power for a pre-planned reactor trip. With the TDAFW pump already in operation, the MDAFW pumps were manually started and the unit was tripped from about 25 percent reactor power. After the plant had stabilized, the TDAFW pump was secured. Steam generator levels lowered to the Lo-Lo alarm setpoint of 17 percent. The trip time delay at 0 percent power is three minutes, so the TDAFW pump automatically started on Lo-Lo level, with the lowest level reached being 15 percent.
This event was a result of human error during the briefing for the event to insure that SG levels remained above the Lo-Lo start level.
V. ASSESSMENT OF SAFETY CONSEQUENCES
WBN Unit 2 experienced an automatic start of the TDAFW pump after the plant had been shutdown.
Steam generator levels were stable, but below the auto start level provided in the design. The safety significance of this event is considered to be low.
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event No equipment failures occurred 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 All equipment needed for this event was available.
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 Not applicable.
VI. CORRECTIVE ACTIONS
This event was entered into the Tennessee Valley Authority Corrective Action Program and is being tracked under condition report 1202562.
A. lmmediate Corrective Actions Steam Generator levels were increased above the Lo-Lo SG level alarm setpoint and the TDAFW pump was secured.
B. Corrective Actions to Prevent Recurrence Additionaltraining will be performed related to this event. ln addition the Auxiliary Feedwater System Operating lnstruction was revised to include the hip time delay setpoints associated with operation of the TDAFW and MDAFW pumps.
VII. ADDITIONAL INFORMATION
A. Previous similar events at the same plant On December 21,2015, TVA submitted LER 390-2015-006, "Source Range Level Trip Channels (N-31 and N-32) lnoperable During Plant Startup." This LER describes a condition prohibited by Technical Specifications where Watts Bar Unit 1 performed a reactor start-up with the source range (SR) reactor trip in the bypass position (SR trip inoperable). This bypass condition was not
recognized until after the reactor startup was completed. The cause of this event was that operators failed to identify a bypassed safety function during reactor start-up due to inadequate tracking of essential information. While the event described in LER 2015-006 relates to a condition prohibited by TS, and has a human performance cause, the corrective actions taken for that event do not overlap the issue presented in LER 391-2016-006.
B. Additional lnformation None.
C. Safety System Functional Failure Consideration This condition did not result in a safety system functionalfailure.
D. Scrams with Complications Consideration Not applicable.
VIII. COMMITMENTS
None.