05000458/LER-2005-001, Re Unplanned Manual Scram Due to Indication of Ground Fault in Main Generator
| ML050740144 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 03/09/2005 |
| From: | Lorfing D Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| G9.25.1.3, G9.5, RBF1-05-0030, RBG-46408 LER 05-001-00 | |
| Download: ML050740144 (5) | |
| 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)(8) 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 |
| 4582005001R00 - NRC Website | |
text
'iEntergy Entergy Operations, Inc.
River Bend Station 5485 U. S. Highway 61N St. Francisville, LA 70775 Fax 225 635 5068 March 9, 2005 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Licensee Event Report 50-458 / 05-001-00 River Bend Station - Unit 1 Docket No. 50-458 License No. NPF-47 File Nos.
G9.5, G9.25.1.3 RBG-46408 RBF1 0030 Ladies and Gentlemen:
In accordance with 10CFR50.73, enclosed is the subject Licensee Event Report.
This document contains no commitments.
Sincerely, David N. Lorfing Manager - Licensing (acting)
DNL/dhw Enclosure 2-J
Licensee Event Report 50-458/ 05-001-00 March 9, 2005 RBG-46408 RBF1 0030 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. O. 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. Prosanta Chowdhury Louisiana Department of Environmental Quality Office of Environmental Compliance Surveillance Division Radiological Emergency Planning & Response Unit P.O. Box 4312 Baton Rouge, LA 70821-4312
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 0613012007
- 6-2004)
, the NRC may digitslcharacters 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 3
- 4. TITLE Unplanned Manual Scram Due to Indication of Ground Fault in Main Generator
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKETNUM0ER MONT DAY YEAR YEAR NUMBER NO.
00 FACILrTY NAME DOCKET NUMBER 01 15 2005 2005 - 001 -
00 03 09 2005 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
El 20.2201(b) 0 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C)
E 50.73(a)(2)(vii) 1 0
20.2201(d)
El 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) o 20.2203(a)(1) a 20.2203(a)(4) 0 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(8) 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 0 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x)
O 20.2203(a)(2)(iii)
D 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0 73.71(a)(4) o 20.2203(a)(2)(iv) a 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(B) a 73.71(a)(5) 100 r
20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C) 0 OTHER 0
20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B) a 50.73(a)(2)(v)(D)
Specify In Abstract below or In NRC Form 366A
- 12. UCENSEE CONTACT FOR THIS LER
=ACILITY NAME TELEPHONE NUMBER (Incude Area Code)
David N. Lorfing, Manager-Licensing (acting) 225-381-4157MANU-REPORTABLE CAS YTMCMOET MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX FACTURER TO EPIX
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 0 NO DATE 07 01 2005 ABSTRACT (Umit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On January 15, 2005, at 2:12 a.m. CST, while the plant was operating at 100 percent power, a manual reactor scram was initiated. This action was procedurally required in response to an alarm received at 2:10 a.m. which indicated a ground fault in the main generator. The plant shutdown proceeded normally, and safety systems responded as required. This event is being reported in accordance with 10CFR50.73(A)(2)(iv)(a) as a condition that required the manual actuation of the reactor protection system.
Reactor water level was adequately controlled by the main feedwater system. No actuations of emergency core cooling systems, reactor safety relief valves, or standby diesel generators were required. The causal analysis of this event is still in progress, and the results will be reported in a supplement to this report. There were no safety systems out of service at the time of the event. This event was of minimal safety significance.
NRC FORM 366(6-2004)
PRINTED ON RECYCLED PAPER 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 l SEQUENTIAL l REVISION I
NUMBER INUMBER River Bend Station Unit 1 05000-458 2005 001 00 2
OF 3
REPORTED CONDITION On January 15, 2005, at 2:12 a.m. CST, while the plant was operating at 100 percent power, a manual reactor scram was initiated. This action was procedurally required In response to an alarm (**ALM**) received at 2:10 a.m. which indicated a ground fault in the main generator (**TG**). The plant shutdown proceeded normally, and safety systems responded as required. Reactor water level was adequately controlled by the main feedwater system. No actuations of emergency core cooling systems, reactor safety relief valves, or standby diesel generators were required.
INVESTIGATION AND IMMEDIATE CORRECTIVE ACTIONS Troubleshooting activities were Initiated to determine the cause for the generator field ground alarm. An Inspection of the generator exciter system was performed, and no evidence of damage was found. Resistance checks performed on the rotor, rectifier banks, and transformers found that the readings were acceptable to confirm that no ground was present. The machine field ground detector relays were found in the tripped condition. These were reset and the alarm cleared. This indicated that the ground condition was no longer present. Portions of the field control circuitry were individually isolated in an attempt to assure that no real ground occurred.
Testing of the relay (**74**) which actuates the ground fault alarm found it to be out of calibration, such that It was much more sensitive to ground currents than specified.
Technicians recalibrated the relay and restored It to service. Additional testing was performed during plant startup with the turbine at rated speed. This testing did not find any grounds present on the system.
Following plant startup, monitoring of the main generator determined that a small ground existed in the system and that the ground current was slowly increasing. The results of the initial investigation were re-evaluated in light of this new indication.
Inspections of the affected equipment determined that one of the five rectifier
(**RECT**) banks in the generator excitation control system was the source of the ground, and It was removed from service. Contingency plans were developed for operation in this condition with conservative trigger points built In, including a decision step to remove the unit from service If necessary.
In the interim, there have been indications of a hydrogen leak into the generator stator cooling system. Such leaks affect stator cooling water chemistry as well as stator corrosion properties. Deposition of stator corrosion products in the rectifier cooling tubes is considered to be the most likely cause of the generator field ground. The unit was shut down on February 19 to perform a partial investigation of this hydrogen leak, and other work.U.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 NUMBER NUMBER River Bend Station Unit 1 05000-458 2005
- - 001
- - 00 3
OF 3
CAUSAL ANALYSIS and CORRECTIVE ACTIONS TO PREVENT RECURRENCE The results of the causal analysis for this event will be reported in a supplement to this LER.
SAFETY SIGNIFICANCE
The plant responded as designed to the manual scram, and no actuations of emergency core cooling systems, reactor safety relief valves, or standby diesel generators were required. This event was of minimal safety significance.
(NOTE: Energy Industry Component Identification codes are annotated as (**XX**).)