05000260/LER-2017-001, Regarding High Pressure Coolant Injection Safety System Functional Failure Due to a Blown Fuse
| ML17104A238 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 04/14/2017 |
| From: | Bono S Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 17-001-00 | |
| Download: ML17104A238 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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)(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)(A), Loss of Safety Function - Shutdown the Reactor 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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) |
| 2602017001R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 April 14, 2017 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001
Subject:
Browns Ferry Nuclear Plant, Unit 2 Renewed Facility Operating License No. DPR-52 NRC Docket No. 50-260 Licensee Event Report 50-260/2017-001-00 10 CFR 50.73 The enclosed Licensee Event Report provides details a spurious High Pressure Coolant Injection Safety System Functional Failure due to a blown fuse. The Tennessee Valley Authority is submitting this report in accordance with Title 10 of the Code of Federal Regulations 50.73(a)(2)(v)(D), as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to 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 M. W. Oliver, Nuclear Site Licensing Manager, at (256) 729-2636.
Enclosure: Licensee Event Report 50-260/2017-001 High Pressure Coolant Injection Safety System Functional Failure Due to a Blown Fuse.
cc (w/ Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant
ENCLOSURE Browns Ferry Nuclear Plant Unit 2 Licensee Event Report 50-260/2017-001-00 High Pressure Coolant Injection Safety System Functional Failure Due to a Blown Fuse See Enclosed
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 0313112020 (04-2017) httQ ://www. n re.gov I reading-rm/doc-col lectio ns/n u regs/staff/sr1 022/ r30 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 05000-260 1 OF6
- 4. TITLE High Pressure Coolant Injection Safety System Functional Failure Due to a Blown Fuse
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR REV MONTH DAY YEAR N/A NUMBER NO.
N/A 02 16 2017 2017
- - 001
- - 00 04 14 2017 FACILITY NAME DOCKET NUMBER N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR &: Check all that aoolv!
D 20.2201(b)
D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) 1 D 20.2201 (d)
D 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B)
D 20.2203(a)(1 )
D 20.2203(a)(4)
D so.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
D 50.36(c)(1 )(i)(A) 0 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x)
- 10. POWER LEVEL D 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(v)(A)
D 73.71(a)(4)
D 202203(a)(2)(iii)
D so.36(c)(2) 0 50.73(a)(2)(v)(B)
D 73. 71 (a)(S) 076 0 20.2203(a)(2)(iv)
D so.46(a)(3)(ii) 0 50.73(a)(2)(v)(C)
D 73.77(a)(1) 0 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
~ 50.73(a)(2)(v)(D)
D 73.77(a)(2)(i) 0 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B) 0 50.73(a}(2)(vii)
D 73.77(a)(2)(ii) 0 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT r ELEPHONE NUMBER (Include Area Code)
Ryan Coons, Licensing Engineer 256-729-2070 CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TOEPIX FACTURER TO EPIX x
BJ FU S156 y
N/A N/A N/A N/A N/A
- 14. SUPPLEMENTAL REPORT EXPECTED
[gj NO SUBMISSION DATE N/A N/A N/A
!ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten fines)
On February 16, 2017, the spurious failure of a fuse protecting a High Pressure Coolant Injection (HPCI) system
!flow controller rendered the HPCI system inoperable. Operators replaced both the line and neutral fuses, and restored HPCI availability. Following a period of monitoring the current flow through the fuse and HPCI system operation tests, Operations declared the Unit 2 HPCI system to be Operable on February 17, 2017.
Since HPCI is a single-train safety system, any period of unplanned inoperability constitutes a safety-system
!functional failure affecting accident mitigation, and is reportable. However, in the event of an emergency, the Reactor Core Isolation Cooling (RCIC) system remained operable, and all other Emergency Core Cooling Systems and the Automatic Depressurization System were available throughout this event to facilitate core cooling.
Failure analysis indicates that the fuse failed when its internal resistor lead and its tension/retraction spring became uncoupled at their soldered junction, as a result of age-induced solder creep. Corrective Actions include he prompt replacement of the failed fuses, determining the population of fuses on the HPCI system and RCIC system that should be replaced on a one-time basis, and to initiate work orders to replace these fuses.
NRC FORM 366 (04-2017)
I.
Plant Operating Conditions Before the Event
At the time of discovery, Browns Ferry Nuclear Plant (BFN), Unit 2, was in Mode 1 at approximately 76 percent power.
II.
Description of Event
A. Event Summary On February 16, 2017, at 1052 Central Standard Time (CST), while the BFN Unit 2 High Pressure Coolant Injection (HPCI) system [BJ] was in standby readiness, Operations received the HPCI 120VAC POWER FAILURE alarm on Panel 2-9-3F. The crew responded per the Alarm Response Procedure and identified that fuse [FU] 2-FU2-073-0033C in the Auxiliary Instrument Room had cleared. This fuse protected the HPCI system flow controller (2-FIC-77-33), power supplies to the governor controls, and power supplies to various pressure transmitters from overcurrent events.
Since the HPCI system is a single-train safety system, any period of unplanned inoperability constitutes a safety-system functional failure affecting accident mitigation, and is a reportable event.
Operators replaced both the line and neutral fuses, and HPCI system availability was restored on February 16, 2017 at 1145 CST. Following a period of monitoring the current flow through the fuse and HPCI system operation tests, Operations declared the Unit 2 HPCI system Operable on February 17, 2017 at 1730 CST.
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, systems, or components whose inoperability contributed to this event. Page 2 of 6 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 (04-2017)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nu regs/staff/sr1022/r30
, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. LER NUMBER YEAR Browns Ferry Nuclear Plant, Unit 2 05000-260 SEQUENTIAL NUMBER 2017
- - 001
C. Dates and approximate times of occurrences
Dates & Approximate Times February 16, 2017, at 1052 CST February 16, 2017, at 1145 CST February 17, 201 7, at 1730 CST Occurrence Operations received a HPCI 120VAC POWER FAILURE alarm.
HPCI system is declared inoperable due to the loss of 120 VAC power to the HPCI Flow Controller, 2-FIC-73-33.
The Unit Supervisor immediately verified Reactor Core Isolation Cooling (RCIC) system [BN] operability by administrative means, in accordance with the Required Actions for Technical Specification (TS) Limiting Condition for Operation 3.5.1, Condition C.
Operations declared the Unit 2 HPCI system available following fuse replacement for the HPCI system flow controller power supply. The Unit 2 HPCI system still remained inoperable pending further investigation.
Operations declared the Unit 2 HPCI system Operable following fuse replacement and post-maintenance testing.
D. Manufacturer and model number of each component that failed during the event
The failed component was a Shawmut Company fuse, model number AJT-3.
E. Other systems or secondary functions affected
No other systems or secondary functions were affected by this event.
F. Method of discovery of each component or system failure or procedural error
REV NO.
- - 00 Failure was discovered on February 16, 2017, at 1052 CST when the 120 VAC power supply circuit for HPCI system flow controller fuse cleared, triggering the HPCI 120VAC POWER FAILURE alarm on Control Room Panel 2-9-3F.
G. The failure mode, mechanism, and effect of each failed component
The fuse failed when its internal resistor lead and its tension/retraction spring became uncoupled at their soldered junction. Analysis by the Tennessee Valley Authority (TVA) Central Laboratories Services determined that this was a spontaneous failure which was not due to an overcurrent event.
The presumed failure mechanism is solder creep, which is a time-dependent failure mechanism. Page 3 of 6 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 (04-2017)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1 022, R.3 for instruction and guidance for completing this form http ://www. n re. gov/reading-rm/doc-collections/nu regs/staff /sr1 022/r30
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
YEAR Browns Ferry Nuclear Plant, Unit 2 05000-260 2017
- 3. LER NUMBER SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 The exact age and installation date of the failed fuse was unable to be determined. Based on the history of the name brand, the failed fuse was manufactured sometime between 1976 and 1999.
H. Operator actions
There were no operator actions associated with this event.
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. Cause of each component or system failure or personnel error The fuse failed when its internal resistor lead and its tension/retraction spring became uncoupled at their soldered junction, which was presumably weakened by solder creep.
No human performance related root causes were identified.
IV.
Analysis of the event
TVA is submitting this report in accordance with Title 10 of the Code of Federal Regulations 50.73(a)(2)(v)(D), as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. The condition was discovered on February 16, 2017, when the spurious failure of the fuse protecting the HPCI system flow controller signaled an alarm [FA] in the Control Room [NA]. This loss of power rendered Unit 2 HPCI system inoperable. Since HPCI system is a single-train safety system, the unplanned inoperability caused by the fuse failure constitutes a reportable event, which is considered a safety system functional failure, and a reportable event.
V.
Assessment of Safety Consequences
This event resulted in inoperability and unavailability of the single train of the BFN Unit 2 HPCI system resulting in the inability of the HPCI system to perform its safety function. In the event of an emergency, the RCIC system remained operable, and all other Emergency Core Cooling Systems (ECCS) and Automatic Depressurization System (ADS) were available during this event to facilitate core cooling.
Based on the discussion above, during the time period that the HPCI system was inoperable, sufficient systems were available to provide the required safety functions to protect the health and safety of the public. Page 4 of 6 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 (04-2017)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nu regs/staff/sr1022/r30
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
YEAR Browns Ferry Nuclear Plant, Unit 2 05000-260 2017
- 3. L.ER NUMBER SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event The TS Required Actions and Completion Times for HPCI system inoperability is to immediately verify that RCIC system is operable by administrative means, and restore HPCI system operability within 14 days. If these actions do not meet their Completion Times, then TS requires Unit 2 to enter Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Operations personnel immediately verified that RCIC was operable by administrative means on February 16, 2017 at1052 CST. During this event, all other ECCS, including the ADS, were available to mitigate abnormal and accident conditions.
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 shutdown.
C. For failure that rendered a train of a safety system inoperable, estimate of the elapsed time from discovery of the failure until the train was returned to service The HPCI system was determined to be inoperable when a blown fuse resulted in a HPCI 120VAC POWER FAILURE alarm actuation on February 16, 2017 at 1052 CST. The HPCI system was declared operable on February 17, 2017 at 1730 CST following post-maintenance testing.
Approximately 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> elapsed between the time of discovery and restoring operability.
VI.
Corrective Actions
Corrective Actions are being managed by TV/\\s corrective action program under Condition Report (CR) 1263268.
A. Immediate Corrective Actions
The Operations crew responded in accordance with the Alarm Response Procedure, and identified that fuse 2-FU2-073-0033C in the Auxiliary Instrument Room had cleared. Operators promptly replaced both the line and neutral fuses to restore HPCI functionality. The Unit 2 HPCI system was declared available by Operations within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of fuse failure.
B. Corrective Actions to Prevent Recurrence or to reduce the probability of similar events occurring in the future Corrective Actions included the prompt replacement of the failed fuses, a determination of the population of HPCI system and RCIC system fuses that should be replaced on a one-time basis, and the replacement of those fuses. Page 5 of 6 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 (04-2017)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-col\\ections/nuregs/staff/sr1022/r3[J
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. LER NUMBER YEAR Browns Ferry Nuclear Plant, Unit 2 05000-260 2017
VII. Previous Similar Events at the Same Site
SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 In May 2002, the NRC published NUREG-1760, an aging assessment of safety-related fuses. This study found that fusible link degradation accounts for approximately 80% of fuse failure events occurring below the fuse's rated current.
A search of the BFN Corrective Action Program identified 12 fuses which spuriously opened since 2010.
The search did not identify a fuse failure at the location described in this LER.
A review of BFN LERs for the last five years identified one event where a blown fuse resulted in an actual safety system functional failure: LER 50-260/2016-001-01, High Pressure Coolant Injection Safety System Functional Failure due to a Blown Fuse and a Failed Relay. For this event, the fuse failure was due to test equipment, not aging effects. Therefore, the corrective actions for this previous event would not have prevented the current event.
VIII. Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments. Page 6 of 6