05000458/LER-2006-006, Re Plant Mode Change with One Offsite Power Supply Inoperable Due to 4.16kv Breaker Alignment
| ML062130074 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 07/26/2006 |
| From: | Lorfing D Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| G9.25.1.3, G9.5, RBF-06-0120, RBG-46601 LER 06-006-00 | |
| Download: ML062130074 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(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 |
| 4582006006R00 - NRC Website | |
text
AE g
---="Enterg Entergy Operations, Inc.
River Bend Station 5485 U.S. Highway 61 N St. Francisville, LA 70775 Tel 225 381 4157 Fax 225 635 5068 dlorfin@entergy.com David N. Lorfing Manager-Licensing July 26, 2006 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Licensee Event Report 50-458 / 06-006-00 River Bend Station - Unit 1 Docket No. 50-458 License No. NPF-47 File Nos.
G9.5, G9.25.1.3 RBG-46601 RBF1-06-0120 Ladies and Gentlemen:
In accordance with IOCFR50.73, enclosed is the subject Licensee Event Report.
This document contains no commitments.
Sincerely, DNL/dhw Enclosure
_a--,
- - R,
Licensee Event Report 50-458 / 06-006-00 July 26, 2006 RBG-46601 RBF1-06-0120 Page 2 of 2 cc:
U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 NRC Sr. Resident Inspector P. 0. Box 1050 St. Francisville, LA 70775 INPO Records Center E-Mail Mr. Jim Calloway Public Utility Commission of Texas 1701 N. Congress Ave.
Austin, TX 78711-3326 Mr. Jeff Meyers Louisiana Department of Environmental Quality Office of Environmental Compliance P.O. Box 4312 Baton Rouge, LA 70821-4312
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)
, 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 River Bend Station - Unit 1 05000-458 1 of 5
- 4. TITLE Plant Mode Change with One Offsite Power Supply Inoperable Due to 4.16kv Breaker Alignment
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE 1
- 8. OTHER FACILITIES INVOLVED I
AILIYNM OKTNME MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR 05000 lFACILITY NAME DOCKET NUMBER 05!27 2006 2006 - 006 -
00 07 26 2006 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
[1 20.2201(b)
El 20.2203(a)(3)(i)
[I 50.73(a)(2)(i)(C)
[: 50.73(a)(2)(vii) 0E 20.2201(d)
El 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
[I 50.73(a)(2)(viii)(A)
[I 20.2203(a)(1)
[I 20.2203(a)(4)
[I 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
[I 20.2203(a)(2)(i)
[E 50.36(c)(1)(i)(A) 0l 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL C0 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)
Cl 20.2203(a)(2)(iii)
El 50.36(c)(2)
[I 50.73(a)(2)(v)(A)
[: 73.71(a)(4)
[I 20.2203(a)(2)(iv)
[I 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5) 100 [1 20.2203(a)(2)(v)
[I 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER [E 20.2203(a)(2)(vi) 9 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME David N. Lorfing, Manager-Licensing TELEPHONE NUMBER (Include Area Code) 225-381-4157
- 14. SUPPLEMENTAL REPORT EXPECTED [E YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On May 27, 2006, while the unit was operating at 100 percent power, the determination was made that one of the required offsite power supplies to the Division 3 standby switchgear had been inoperable during the recent plant startup on May 13, 2006. A 4160 volt circuit breaker in one of the power supplies to Division 3 was not functional at the time of the plant startup. This condition does not meet the requirements of Technical Specifications Limiting Condition for Operation 3.0.4. In addition, during the investigation, it was determined that the surveillance test procedure that implements Surveillance Requirement 3.8.1.1 did not include the verification of the alignment of the offsite power supplies to Division 3. A similar condition was also found to exist for Surveillance Requirement 3.8.1.8. These conditions are being reported in accordance with 10CFR50.73(a)(2)(i)(B) as operations prohibited by Technical Specifications. The circuit breaker was subsequently repaired and demonstrated to be functional. The Division 3 emergency diesel generator is the safety-related power source for the Division 3 switchgear, and it was operable at the time this condition was discovered. Therefore, this condition was of minimal safety significance.
NRC FORM 366 (6-2004)
PRINTED ON RECYCLED PAPERU.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
FAILURE CONTINUATION
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION YEAR NUMBER NUMBER River Bend Station - Unit 1 05000-458 2006 006 00 2
OF 5
REPORTED CONDITION On May 27, 2006, while the unit was operating at 100 percent power, the determination was made that one of the required offsite power supplies to the Division 3 standby switchgear (EB) had been inoperable during the recent plant startup on May 13. A 4160 volt circuit breaker (**52**) in this offsite power supply to Division 3 was not functional at the time of the plant startup. This condition does not meet the requirements of Technical Specifications Limiting Condition for Operation (LCO) 3.0.4. This LCO requires that this power supply be operable during a plant startup.
In addition, during the investigation, it was determined that the surveillance test procedure (STP) that implements Surveillance Requirement (SR) 3.8.1.1 did not include the verification of the alignment of the offsite power supplies to Division 3. A similar condition was also found to exist for SR 3.8.1.8. SR 3.8.1.8 requires verification of the capability to transfer from one offsite power supply to the alternate. These conditions are being reported in accordance with 10CFR50.73(a)(2)(i)(B) as operations prohibited by Technical Specifications.
INVESTIGATION River Bend Technical Specifications require that "two qualified circuits between the offsite transmission network and the onsite Class 1E AC electric power distribution system..."
shall be operable (Limiting Condition for Operations 3.8.1). The basis section for LCO 3.8.1 states that, in part, that "Each offsite circuit consists of incoming breakers and disconnects to the respective preferred station service transformers IC and 1D, the 1C and ID preferred station service transformers, and the respective circuit path including feeder breakers to the three 4.16 kV ESF buses." Surveillance Requirement (SR) 3.8.1.1 requires a weekly verification of the "...correct breaker alignment and indicated power availability for each required offsite circuit." Surveillance Requirement 3.8.1.8 has a specified frequency of 18 months, and verifies "manual transfer of unit power supply from the normal offsite circuit to required alternate offsite circuit."
The Division 3 switchgear is provided with two separate, independent sources of offsite power, in addition to its dedicated diesel generator (DG). When the plant is operating, the switchgear may be supplied from "station service" transformers that are energized by the main generator. Alternatively, the switchgear may be supplied at any time from offsite power via either of two dedicated 230kv lines running from the plant's switchyard into the "preferred transformers" in the plant. These two offsite power sources are required to be operable by the station's Technical Specifications, and are the sources to which the switchgear is normally aligned. In the case of the Division 3 switchgear, the power from the preferred transformers is routed through two non-safety related 4160 volt switchgears inside the plant. This is a different design than Divisions 1 and 2, which are powered directly from the preferred transformers.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
FAILURE CONTINUATION
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL I REVISION YEAR NUMBER NUMBER River Bend Station - Unit 1 05000-458 2006 006 00 3
OF 5
During the refueling outage that ended on May 13, circuit breaker NNS-ACB23 (hereafter referred to as "ACB23"), in one of the circuits supplying Division 3, was removed from service for maintenance. Following this activity, the breaker was racked back into the "connect" position in its cubicle on April 29, and left in the open position. On May 9, during an operator's control panel walkdown in the main control room, it was identified that the white "control power" light for ACB23 was not illuminated as was expected. A maintenance work order was initiated. The person performing the operability evaluation of that work order concluded that, since the breaker is not safety-related and not subject to surveillance testing, it was not necessary to resolve the deficiency prior to plant startup. Thus, the breaker was not listed on any tracking mechanism requiring that repairs be performed prior to startup. The generic Operations procedure on breaker racking did not specify a verification that the control power light illuminates when racking that breaker into the "connect" position on April 29, because not all breakers in the plant are configured such that control power is activated simply by racking the breaker in.
On May 22, during preparations for a scheduled surveillance test for the Division 3 DG, an attempt was made to close ACB23. The breaker did not appear to cycle, and the yellow "tripped" light illuminated at the breaker control switch. It was not recognized by the operators at the time, but one of the permissive signals necessary to close the breaker was not present. (The next breaker upstream was not closed.) The breaker was then racked out and back in to verify the integrity of the "connect" position. It was reported that the racking mechanism was unusually difficult to operate. Another attempt was then made to close the breaker. The breaker did appear to cycle, but again tripped. Further inspection by maintenance technicians found that the racking mechanism could be rotated approximately one more turn (at which point the control power light illuminated), leading to the conclusion that the breaker likely had not been fully racked in. The upstream breaker was subsequently closed, and ACB23 was successfully placed in service. A Condition Report was initiated to document that the breaker's racking mechanism was difficult to operate.
Since the breaker was not restored to service until after the plant startup on May 13, the requirements of LCO 3.0.4 were not met.
On June 26, a replacement breaker was installed in the ACB23 cubicle, and successfully tested. The breaker that was removed from service was inspected to determine the cause of the malfunction. No misadjustment of the internal mechanisms was found. Operations has since performed four complete racking and breaker closure cycles on the replacement breaker ACB 23 to verify reliable, repeatable performance.
IMMEDIATE CORRECTIVE ACTIONS
Pending the revision of surveillance test procedures to address SR 3.8.1.1, Operations began recording the status of the Division 3 offsite power supply circuits weekly in the Main Control Room logs.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
FAILURE CONTINUATION
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL I REVISION YEAR NUMBER INUMBER River Bend Station - Unit 1 05000-458 2006 006 00 4
OF 5
The breaker operations that occurred during the troubleshooting and repair of ACB23 adequately demonstrated the ability to transfer the Division 3 switchgear from one offsite power source to the other.
CAUSAL ANALYSIS A historical review of STPs implementing Surveillance Requirements 3.8.1.1 (STP-000-0102) and 3.8.1.8 (STP-302-0601) was conducted. At the initial implementation of the Technical Specification surveillance test program at River Bend, the offsite power supplies to Division 3 were omitted from these test procedures. It appears that the unique configuration of the offsite power supply to Division 3 contributed to a decision that these Surveillance Requirements should not apply to that switchgear.
In February 1998, a Condition Report was initiated concerning the omission of the offsite power supply breakers to Division 3 from the station surveillance program. A review of the Updated Safety Analysis Report, as well as applicable General Design Criteria and Regulatory Guides concluded that the scope of the surveillance program was adequate with regard to offsite power systems. No change was made to the surveillance test program at that time with regard to Division 3 power sources. In retrospect, the disposition of that Condition Report did not adequately address the Technical Specifications.
The lack of surveillance requirements on ACB23 (as well as its associated breakers) contributed to the conclusion on April 29 that the failure of the control power indication was not a constraint on plant startup.
CORRECTIVE ACTION TO PREVENT RECURRENCE The following actions are planned to prevent recurrence, and are being tracked in the station's corrective action program.
A detailed review of the implementation of SR 3.8.1.1 and 3.8.1.8 is being conducted to develop recommendations for changes to the affected STPs. This information will be used to revise the STPs for SR 3.8.1.1 and 3.8.1.8.
The operations procedure for breaker racking will be revised to include requirements to (1) verify indication of control power, and (2) perform a functional test of breakers that support a safety function.
- The Technical Specification Bases will be revised to clarify the applicability of Division 3 to SR 3.8.1.1 and 3.8.1.8.
- Training on this condition will be conducted for the Operations and Licensing staffs.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
FAILURE CONTINUATION
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL I REVISION YEAR NUMBER NUMBER River Bend Station - Unit 1 05000-458 2006 006 00 5
OF 5
PREVIOUS OCCURRENCE A review of recent reportable events found no other instances of historical omissions in the surveillance testing program.
SAFETY SIGNIFICANCE
During the period following plant startup in which ACB23 was inoperable, the other offsite power supply to Division 3 was functional and in service. At the time of the reported condition, the Division 3 DG was operable, and capable of restoring power to its switchgear in the event of a loss of offsite power.
Divisions 1 and 2 were operable at the time of plant startup, and were available for mitigation of postulated events described in the station's Updated Safety Analysis Report.
Therefore, the reported condition was of minimal safety significance.
(NOTE: Energy Industry Component Identification codes are annotated as (**XX**).)