05000302/LER-2013-001, Regarding Valid Actuation of an Emergency Diesel Generator Due to a Spurious Fault on a Breaker Non-Segregated Bus Duct
| ML13221A579 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 07/25/2013 |
| From: | Elnitsky J Duke Energy Florida |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 3F0713-02 LER 13-001-00 | |
| Download: ML13221A579 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3022013001R00 - NRC Website | |
text
- ENERGY, Crystal River Nuclear Plant 15760 W. Power Line Street Crystal River, FL 34428 Docket 50-302 Operating License No. DPR-72 10 CFR 50.73 July 25, 2013 3F0713-02 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
Subject:
Crystal River Unit 3 - Licensee Event Report 50-302/2013-001-00
Dear Sir:
In accordance with 10 CFR 50.73(a)(2)(iv)(A), Duke Energy Florida, Inc., formerly known as Florida Power Corporation, hereby submits Licensee Event Report (LER) 50-302/2013-001-00 for Crystal River Unit 3.
This LER discusses the valid actuation of an Emergency Diesel Generator due to a spurious fault on a breaker non-segregated bus duct.
No new regulatory commitments are made in this letter.
If you have any questions regarding this submittal, please contact Mr. Dan Westcott, Licensing Supervisor, at (352) 563-4796.
Sincerely,
- - Project Management and Construction JE/dwh Attachment xc:
NRR Project Manager Regional Administrator, Region II
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38C FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-20 10)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE CRYSTAL RIVER UNIT 3 05000302 1 of 7
- 4. TITLE Valid Actuation of an Emergency Diesel Generator Due to a Spurious Fault on a Breaker Non-Segregated Bus Duct
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YRSEQUENTIAL REV FACILITY NAME DOCKET NUMBER YEAR NUMBER NO.
MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 06 01 2013 2013 - 001 -
00 07 25 2013 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 0l 20.2201(b)
El 20.2203(a)(3)(i) 0- 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
No Mode 0l 20.2201(d)
El 20.2203(a)(3)(ii)
[3 50.73(a)(2)(ii)(A)
C3 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
E] 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
C] 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL E] 20.2203(a)(2)(ii)
[1 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
C3 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A) 0l 73.71(a)(4)
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii) 0l 50.73(a)(2)(v)(B)
[1 73.71(a)(5) 0%
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
C3 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
[j 50.73(a)(2)(v)(D)
Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)
Dennis W. Herrin, Lead Licensing Engineer
ý 352-563-4633SYSTEM MANU-REPORTABLE CU SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
COMPONENT FACTURER TO EPIX
CAUSE
FACTURER TO EPIX D
EA NSBU C048 Y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION El YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 0 NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
At 21:29, on June 1, 2013, Crystal River Unit 3 (CR-3) was in NO MODE (core permanently off loaded for decommissioning) at 0 percent RATED THERMAL POWER when a spurious fault above Breaker 3104 (Startup Transformer (SUT) feed to the "B" Unit 6.9 kilovolt (kV) non-segregated bus) occurred. Protective relaying de-energized the SUT and the Backup Engineered Safeguards Transformer, which de-energized the "B" Engineered Safeguards (ES) 4160 volt (V) bus. All relays operated as designed. The "B" Emergency Diesel Generator automatically started and re-energized the "B" ES 4160V bus, as designed. The only credible accidents for CR-3 are a Fuel Handling Accident and a Waste Gas Decay Tank (WGDT)
Rupture Accident. At the time of the spurious fault, the Spent Fuel Pools (SFPs) were being cooled by the "A" SFP pump. The SFPs and WGDTs were unaffected. This condition does not represent a reduction in the public health and safety. Valid actuation of an Emergency Diesel Generator is reportable under 10 CFR 50.73(a)(2)(iv)(A). The cause for the fault was lack of a bus duct internal seal inspection Preventive Maintenance (PM) task which led to undetected condensate accumulation and formation of a conductive bridge to ground causing the bus fault.
An internal seal inspection criterion is being developed. Similar occurrences have not been previously reported to the NRC.
NRC FORM 366 (10-2010)
PRINTED ON RECYCLED PAPERU.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
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- 2. DOCKET
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- 3. PAGE SEQUENTIAL I REVISION YEAR NUMBER NUMBER CRYSTAL RIVER UNIT 3 105000-302 2013 001 00 2
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EVENT DESCRIPTION
At 21:29, on June 1, 2013, Duke Energy Florida, Inc., (DEF) Crystal River Unit 3 (CR-3) was in NO MODE (core permanently off loaded for decommissioning) at 0 percent RATED THERMAL POWER when a spurious fault above (on the line side of) Breaker 3104 (Startup Transformer (SUT) [EB, XFMR] feed to the "B" Unit 6.9 kilovolt (kV) non-segregated bus (MTBD-1 3A [EA, NSBU])) [EA, BKR] occurred. At the time of the fault, Breaker 3104 was open; therefore, no overcurrent condition occurred on the load side of the breaker. Protective relaying de-energized the SUT and the Backup Engineered Safeguards Transformer (BEST) [EB, XFMR], which de-energized the "B" Engineered Safeguards (ES) 4160 volt (V) bus [EB, BU]. The "B" Emergency Diesel Generator (EGDG-1 B) [EK, DG] started and re-energized the "B" ES 4160V bus. (Figure 1 is a simplified distribution diagram that shows the breaker alignment immediately prior to the event.)
MTBD-13A is fed from the SUT which is supplied by the 230kV offsite power switchyard bus [EA, BU]. All three SUT differential relays [EA, 87] actuated. This caused the SUT lockout relays (LORs) [EA, 86] to operate, which in turn, operated the BEST master relay LORs. The appropriate breakers were opened by the LORs, including 230kV Breakers 1691 and 1692 [EA, BKR]. All relays operated as designed. EGDG-1 B automatically started on a valid signal and loaded, as designed.
At 04:38, on June 2, 2013, an 8-hour notification was made to the Nuclear Regulatory Commission (NRC) Operations Center in accordance with 10 CFR 50.72(b)(3)(iv)(A) for valid actuation of an Emergency Diesel Generator. This condition is also reportable as a 60-day Licensee Event Report under 10 CFR 50.73(a)(2)(iv)(A).
CAUSE
The exact location of the fault was determined to be at the lowest seal plate in the non-.
segregated bus duct [EA, BDUC] above (on the line side of) Breaker 3104. The failure caused extensive damage to the switchgear cubicle, the bus duct surrounding the bus bars, and portions of the bus bars. The switchgear cubicle door was blown open during the event, shearing and bending the hinges on the door. The vertical bus duct connected to the upper portion of the switchgear cubicle was deformed outward breaking numerous riveted and bolted connections. The non-segregated bus duct was manufactured by the Calvert Company (AZZ Calvert).
The root cause for the fault is identified as the lack of a Calvert bus internal penetration seal Preventive Maintenance (PM) task which led to undetected condensate accumulation and formation of a conductive bridge to ground causing the bus fault. Failure of MTBD-1 3A occurred as a phase-to-ground fault. Inspections after the fault revealed signs that moisture had accumulated. A deficient internal penetration seal allowed moisture to accumulate inside the bus. Previous inspections of MTBD-13A did not reveal the deficient penetration seal due to lack of a PM task to inspect the internal penetration seal. The deficient penetration seal subsequently allowed warm, humid air to enter the Calvert bus duct in a temperature controlled environment. Warm, humid air then cooled, causing condensation to accumulate within the bus duct and creating a conductive bridge to ground.PRINTED ON RECYCLED PAPER
¢-U.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL I REVISION YEA NUMBER NUMBER CRYSTAL RIVER UNIT 3 05000-302 2013 001 00 3
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Prior to the bus fault, the environment in the switchgear room where the damage occurred was inadvertently primed for increased condensation formation when the Appendix R Chiller [VF, CHU] supplying cool air to the room was returned to service after being inoperable for several weeks. One of the cool air returns exhausts directly on/towards MTBD-1 3A. This was determined to have contributed to the fault, but was not the root cause of the event.
SAFETY CONSEQUENCES
CR-3 has been safely shutdown since September 26, 2009, when the plant entered the Cycle 16 refueling outage to replace the steam generators [AB, SG]. Since September 26, 2009, fuel was reloaded into the reactor vessel [AB, RPV] from the Spent Fuel Pools (SFPs) [DA] once in anticipation of unit restart. However, restart was subsequently deferred and the fuel was off loaded to the SFPs where it currently resides. The final removal of fuel from the reactor vessel was completed on May 28, 2011. No fuel has been used in the reactor vessel for power generation since the CR-3 shutdown began on September 26, 2009.
On February 20, 2013, DEF informed the NRC that CR-3 had permanently ceased operations and that the fuel had been permanently removed from the reactor vessel. On March 13, 2013, the NRC acknowledged the CR-3 certificate of permanent cessation of power operation and permanent removal of fuel from the reactor vessel. Therefore, pursuant to 10 CFR 50.82(a)(2),
the 10 CFR 50 license for CR-3 no longer authorizes operation of the reactor or emplacement or retention of fuel in the reactor vessel.
Final Safety Analysis Report Change Package 2013-0008 was approved on June 5, 2013.
Chapter 14, "Safety Analysis," was revised to remove core and coolant boundary protection analyses and standby safeguards analyses for transients and accidents that are no longer credible for a plant that has permanently ceased operation and removed all fuel from the reactor. The only remaining credible accidents analyzed are a Fuel Handling Accident and a Waste Gas Decay Tank (WGDT) [WE, TK] Rupture Accident.
At the time of the spurious fault, the SFPs were being cooled by the "A" SFP pump [DA, P].
Although failure of MTBD-13A caused extensive damage to the switchgear cubicle, the bus duct surrounding the bus bars, and portions of the bus bars, the SFPs and WGDTs were unaffected.
DEF concludes that the failure of MTBD-13A did not represent a reduction in the public health and safety.
CORRECTIVE ACTIONS
- 1. The faulted portion of MTBD-13A, the SUT and the BEST were isolated on 06/01/2013 through protective relaying.
- 2. Both ES 4160V buses were aligned to the Offsite Power transformer on 06/02/2013.
- 3. EGDG-1 B was secured and restored to a standby condition on 06/02/2013.PRINTED ON RECYCLED PAPERU.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
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- 4. Additional corrective actions developed as part of the root cause evaluation are being tracked in the CR-3 Corrective Action Program under Condition Report (CR) 609671 and include, but are not limited to:
a. Determine whether or not the faulted portion of MTBD-1 3A will be repaired based on the long term electrical alignment of CR-3 not requiring the equipment.
b. Perform the inspections/testing for the other Calvert bus installations with similar configurations as MTBD-1 3A. Repair any identified damage as necessary.
c. Revise the model PM task for the Calvert bus detailed internal inspection of sections (MTBD-12A/B/C/D/E/F/G/H and MTBD-13A/B) to include specific inspection criteria for internal penetration seals.
ADDITIONAL INFORMATION
The 7.2kV, 2,000 amp, non-segregated bus duct is manufactured by the Calvert Company.
PREVIOUS SIMILAR EVENTS
Licensee Event Report (LER) 50-302/1985-028-00 documents the failure of a 6.9kV Unit Auxiliary Bus that caused the loss of two Reactor Coolant Pumps (RCPs) [AB, P], a Reactor Trip and actuation of the Emergency Feedwater Initiation and Control System [BA]. However, the cause for the failure was identified as a loose connection that was found on the "A" phase upper and lower lead assembly on the bus side of the "D" RCP motor breaker [EA, BKR] in the "B" 6.9kV Unit Auxiliary Bus switchgear [EA, SWGR].
No other previous similar occurrences have been reported by CR-3 to the NRC in a LER.
ATTACHMENTS - Abbreviations, Definitions, and Acronyms - List of CommitmentsPRINTED ON RECYCLED PAPERPRINTED ON RECYCLED PAPERU.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
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Figure 1 PROTECTIVE RELAYING ON STARTUP XFMR OPENED 230KV SUPPLY BREAKERS 1691 & 1692 TO 'B' ES 4160 V BUS LOSS OF VOLTAGE RELAYS ACTUATED UPON LOSS OF 230KV SUPPLY WHICH STARTED EGDG-1B AND CLOSED BREAKER 3210 TO SUPPLY THE
'B' ES 4160V BUS AND ASSOCIATED EQUIPMENT Figure 1: Breaker Alignment Shown Immediately Prior to EventPRINTED ON RECYCLED PAPERU.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YER SEQUENTIAL I REVISION YEAR NUMBER NUMBER CRYSTAL RIVER UNIT 3 05000-302 2013 001 00 6
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ATTACHMENT 1 ABBREVIATIONS, DEFINITIONS AND ACRONYMS BEST CFR CR CR-3 DEF EGDG ES kV LER LOR MTBD NRC PM RCP SFP SUT V
WGDT NOTES:
Backup Engineered Safeguards Transformer Code of Federal Regulations Condition Report Crystal River Unit 3 Duke Energy Florida, Inc.
Emergency Diesel Generator Engineered Safeguards Kilovolt Licensee Event Report Lockout Relay MT System Bus Duct Nuclear Regulatory Commission Preventive Maintenance Reactor Coolant Pump Spent Fuel Pool/Spent Fuel Pump Startup Transformer Volt Waste Gas Decay Tank Breaker Open (Figure 1)
Breaker Closed (Figure 1)
Improved Technical Specification defined terms appear capitalized in LER text
{e.g., MODE 1}.
Defined terms/acronyms/abbreviations appear in parenthesis when first used
{e.g., Reactor Building (RB)}.
Energy Industry Identification System (EIIS) codes appear in square brackets
{e.g., reactor building penetration [NH, PEN]}PRINTED ON RECYCLED PAPERPRINTED ON RECYCLED PAPERU.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION YEAR NUMBER NUMBER CRYSTAL RIVER UNIT 3 05000-302 2013 001 00 1
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ATTACHMENT 2 LIST OF COMMITMENTS The following table identifies those actions committed by DEF in this document. Any other actions discussed in the submittal represent intended or planned actions by DEF. They are described to the NRC for the NRC's information and are not regulatory commitments. Please notify the Licensing Supervisor of any questions regarding this document or any associated regulatory commitments.PRINTED ON RECYCLED PAPERPRINTED ON RECYCLED PAPER