05000260/LER-2014-003, Regarding Both Trains of Standby Liquid Control Inoperable
| ML14205A439 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/21/2014 |
| From: | Polson K Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 14-003-00 | |
| Download: ML14205A439 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2602014003R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 July 21, 2014 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 2 Renewed Facility Operating License No. DPR-52 NRC Docket No. 50-260
Subject:
Licensee Event Report 50-26012014-003-00 The enclosed Licensee Event Report provides details of the inoperability of Browns Ferry Nuclear Plant's, Unit 2, Standby Liquid Control System. The Tennessee Valley Authority (TVA) is submitting this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73(a)(2)(v)(A), (C) and (D), as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to shut down the reactor and maintain it in a safe shutdown condition, control the release of radioactive material, or mitigate the consequences of an accident.
There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact J. L. Paul, Nuclear Site Licensing Manager, at (256) 729-2636.
Respectfully, Site Vice President
Enclosure:
Licensee Event Report 50-260/2014-003 Both Trains of Standby Liquid Control Inoperable cc (w/ Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant
U.S. Nuclear Regulatory Commission Page 2 July 21, 2014 JLP:MBA:CSP Enclosure bcc (w/ Enclosure):
NRC Project Manager - Browns Ferry Nuclear Plant S. M. Bono, POB 2C-BFN T. J. Bradshaw, LP 4B-C S. M. Douglas, LP 3R-C J. P. Grimes, LP 3R-C R. G. Perez, LP 3R-C J. B. Nesbitt, NAB 1J K. J. Poison, NAB 2A-BFN A. L. Reagan, NAB 1J K. B. Selph, NAB 1J J. W. Shea, LP 4B-C P. B. Summers, NAB 1A S. A. Vance, WT 6A-K G. R. Williams, LP 4B-C P. R. Wilson, LP 4B-C EDMS, WT CA-K
ENCLOSURE Browns Ferry Nuclear Plant Unit 2 Licensee Event Report 50-26012014-003-00 Both Trains of Standby Liquid Control Inoperable See Enclosed
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 01/3112017 (02-2014)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Browns Ferry Nuclear Plant, Unit 2 05000260 1 of 7
- 4. TITLE: Both Trains of Standby Liquid Control Inoperable
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MON YEAR YEAR NUMBER NO.
N/A 05000 FACILITY NAME DOCKET NUMBER 05 21 2014 2014 -
003 -
00 07 21 20141 N/A 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[o 20.2201(b)
[I 20.2203(a)(3)(i) 0l 50.73(a)(2)(i)(C)
[] 50.73(a)(2)(vii)
[o 20.2201(d)
[I 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
[I 20.2203(a)(1)
[I 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
[: 50.73(a)(2)(viii)(B)
[__ 20.2203(a)(2)(i) 0l 50.36(c)(1)(i)(A)
-] 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL [I 20.2203(a)(2)(ii)
[I 50.36(c)(1)(ii)(A)
[I 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
[3 20.2203(a)(2)(iii)
[I 50.36(c)(2) 0 50.73(a)(2)(v)(A)
[1 73.71(a)(4) 0l 20.2203(a)(2)(iv)
[I 50.46(a)(3)(ii)
[I 50.73(a)(2)(v)(B)
[: 73.71(a)(5) 100 [E 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
C9 50.73(a)(2)(v)(C) 0l OTHER El 20.2203(a)(2)(vi) 0l 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify in Abstract below or in
B. Status of structures, components, or systems that were inoperable at the start of the event and that contributed to the event
There were no structures, components, or systems that were inoperable at the start of the event and that contributed to the event.
C. Dates and approximate times of occurrences
May 21, 2014, at 1550 CDT May 21, 2014, at 1720 CDT May 21, 2014, at 1721 CDT May 21, 2014, at 1746 CDT May 21, 2014, at 1808 CDT BFN, Unit 2, Operators received the SLC Tank Level Abnormal alarm.
Control Room and local indications showed the SLC tank level to be 95.5 percent and rising. Operations notified Chemistry and requested performance of the surveillance for measuring SLC solution level.
During the performance of the SLC solution level measurement surveillance, a Chemistry technician measured the tank level to be greater than 100 percent with the liquid level near the top of the tank and a continuous stream of dime sized bubbles in the solution.
Operations declared the BFN, Unit 2, SLC system inoperable and entered TS LCO 3.1.7.B.
Operations closed the SLC tank isolation valve common to both pumps to prevent additional in-leakage and the potential for overflowing the tank.
The condition was corrected, the SLC isolation valve was opened, and Operations declared the BFN, Unit 2, SLC system Operable.
D. Manufacturer and model number (or other identification) of each component that failed during the event:
No component failures were identified that occurred during the event.
E. Other systems or secondary functions affected
There were no other systems or secondary systems affected.
F. Method of discovery of each component or system failure or procedural error
On May 21, 2014, at 1550 CDT, BFN, Unit 2, Operators received the SLC Tank Level Abnormal alarm. Control Room and local indications showed the SLC tank level to be 95.5 percent and rising.
G. The failure mode, mechanism, and effect of each failed component, if known:
There were no failed components related to this event; however, the SLC level indication sensing line became clogged with sodium pentaborate crystals causing erroneous level indication.
H. Operator actions
Operations notified Chemistry of the SLC Tank Level Abnormal alarm in the Control Room and requested performance of the surveillance for measuring SLC solution level. After Chemistry reported that the SLC tank level was high, Operations declared the BFN, Unit 2, SLC system inoperable and closed the SLC tank isolation valve common to both pumps to prevent additional in-leakage and the potential for overflowing the tank. Operators cleared the SLC level indication sensing line and level indication returned to 89 percent. Operations opened the SLC isolation valve declared the BFN, Unit 2, SLC system Operable.
I. Automatically and manually initiated safety system responses
There were no automatic or manual safety system responses associated with this event.
Ill.
Cause of the event
A. The cause of each component or system failure or personnel error, if known:
This event is the result of the inadequate use of human performance tools by Chemistry personnel which led to the incorrect reporting of SLC tank level when an unexpected condition was encountered.
Human error prevention techniques, such as self and peer checking should have been used commensurate with the risk and scope of the assigned task. Personnel should not have proceeded in the face of uncertain or unexpected conditions.
Human error resulted in clogged SLC sensing line condition becoming consequential.
B. The cause(s) and circumstances for each human performance related root
cause
During the performance of the surveillance for measuring SLC solution level, human error prevention techniques, such as self and peer checking should have been used commensurate with the risk and scope of the assigned task; however, these human error prevention techniques are not prescribed in the surveillance and only one chemistry technician is required to perform the activity.
The observation of dime sized bubbles in the tank and appearance of a rising level was not a previously documented expected condition during task performance.
Personnel should not have proceeded in the face of uncertain or unexpected conditions.
IV.
Analysis of the event
The Tennessee Valley Authority (TVA) is submitting this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73(a)(2)(v)(A), (C) and (D), as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to shut down the reactor and maintain it in a safe shutdown condition, control the release of radioactive material, or mitigate the consequences of an accident.
On May 21, 2014, at 1721 CDT, BFN, Unit 2, declared both trains of SLC inoperable due to suspected in-leakage to the BFN, Unit 2, SLC tank. Personnel were dispatched to check the tank level locally after the Control Room received a high level alarm and reported that tank level was high and rising. Based on this report, the SLC system was declared inoperable and rendered unavailable by closing the SLC tank isolation valve common to both pumps to prevent overflowing the tank. It was subsequently determined that the sensing line had become clogged by sodium pentaborate crystals causing erroneous level indication and the local report of level was incorrect. Sensing lines for the tank level instrumentation were cleared and Operability was restored by returning the isolation valve to the open position and verifying tank level was normal.
The cause of this event was determined to be the result of the inadequate use of human performance tools which led to the incorrect reporting of SLC tank level when an unexpected condition was encountered. The failure to accurately determine the solution level in the SLC tank resulted in Operations isolating both trains of the BFN, Unit 2, SLC system.
During the performance of the surveillance for measuring SLC solution level, human error prevention techniques, such as self and peer checking should have been used commensurate with the risk and scope of the assigned task; however, these human error prevention techniques are not prescribed in the surveillance and only one chemistry technician is required to perform the activity.
The observation of dime sized bubbles in the tank and appearance of a rising level was not a previously documented expected condition during task performance. Personnel should not have proceeded in the face of uncertain or unexpected conditions.
V. Assessment of Safety Consequences
This event resulted in inoperability and unavailability of both trains of the BFN, Unit 2, SLC system resulting in the inability of the SLC system to perform its safety function to shut down the reactor and maintain it in a safe shutdown condition, control the release of radioactive material, and mitigate the consequences of an accident. However, a probabilistic risk assessment determined the cumulative risk for this event to be low.
Based on the discussion above, the safety significance of this event is minimal and the event did not pose a threat to the health and safety of the public or plant personnel.
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event:
During this event normal means of reactivity control were maintained.
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:
This event did not occur when the reactor was shut down.
C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from discovery of the failure until the train was returned to service:
This event resulted in inoperability of the BFN, Unit 2, SLC system for approximately 47 minutes.
VI.
Corrective Actions
Corrective Actions are being managed by TVA's corrective action program under Problem Evaluation Report (PER) 890649.
Immediate Corrective Actions
Operations declared the BFN, Unit 2, SLC system inoperable and closed the SLC tank isolation valve common to both pumps to prevent additional in-leakage and the potential for overflowing the tank. Operators cleared the SLC level indication sensing line and level indication returned to normal. Operations opened the SLC isolation valve declared the BFN, Unit 2, SLC system Operable.
Corrective Actions Reduce Probability of Similar Events Occurring in the Future The corrective actions to reduce recurrence are to revise the surveillance for checking SLC solution level to include a caution note that an accurate tank level stick reading cannot be obtained when excessive bubbling is observed in the tank and that a peer check is required in this case and to increase the frequency of mechanical cleaning of the SLC level indication sensing line. In addition, the responsible Chemistry technician was coached on the appropriate use of human performance tools.
VII.
Additional Information
A. Previous similar events at the same plant:
A search of BFN LERs for Units 1, 2, and 3, for approximately the past three years did not identify any similar events.
A search of the BFN Corrective Action Program over the past three years identified similar PER 515133. In this event the SLC tank level indication increased from 88 percent to 93 percent in four hours. The SLC tank level was measured locally and it was determined that the tank level had not increased. To correct the condition a work order was generated and executed to clear the sensing line.
B. Additional Information
There is no additional information.
C. Safety System Functional Failure Consideration:
This event resulted in the inability of the BFN, Unit 2, SLC system to perform its safety function to shut down the reactor and maintain it in a safe shutdown condition, control the release of radioactive material, and mitigate the consequences of an accident. In accordance with Nuclear Energy Institute (NEI) NEI 99-02, "Regulatory Assessment Performance Indicator Guideline," this event is considered a safety system functional failure.
D. Scram with Complications Consideration:
This event did not result in a reactor scram.
VIII. COMMITMENTS
There are no commitments.