05000455/LER-2013-001, Regarding Manual Reactor Trip Due to Loss of Main Generator Stator Cooling Water
| ML13137A310 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 05/17/2013 |
| From: | Kearney F Exelon Generation Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| BYRON 2013-0062 LER 13-001-00 | |
| Download: ML13137A310 (4) | |
| 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 |
| 4552013001R00 - NRC Website | |
text
May 17, 2013 LTR:
BYRON 2013 -0062 File:
1.10.0101 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Licensee Event Report (LER) 455-2013-001-00, "Unit 2 Manual Reactor Trip Due to Loss of Main Generator Stator Cooling Water" Byron Station, Unit 2 Facility Operating License No. NPF-66 NRC Docket No. STN 50-455 Enclosed is an LER concerning the Byron Station Unit 2 manual reactor trip that occurred on March 20, 2013. This condition is reportable to the NRC in accordance with 10 CFR 50.73(a)(2)(iv)(A) - System Actuation.
Should you have any questions concerning this submittal, please contact Mr. Steven Gackstetter, Regulatory Assurance Manager, at (815) 406-2800.
Respectfully, ber A. Xbarney-Site Vice President Byron Station FAK/DS/cy
Enclosure:
LER 455-2013-001-00 cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - Byron Nuclear Power Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME
. DOCKET NUMBER
- 3. PAGE J
Byron Station, Unit 2 05000455 1
OF 3
- 4. TITLE Unit 2 Manual Reactor Trip Due to Loss of Main Generator Stator Cooling Water
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME N/A DOCKET NUMBER N/A N
MBER U
NO.
FACILITY NAME DOCKET NUMBER 03 20 2013 2013 001 00 05 20 2013 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §:
(Check all that apply) q 20.2201(b) q 20.2203(a)(3)(i) q 50.73(a)(2)(i)(C) q 50.73(a)(2)(vii) 1 q 20.2201(d) q 20.2203(a)(3)(ii) q 50.73(a)(2)(ii)(A) q 50.73(a)(2)(viii)(A) q 20.2203(a)(1) q 20.2203(a)(4) q 50.73(a)(2)(ii)(B) q 50.73(a)(2)(viii)(B) q 20.2203(a)(2)(i) q 50.36(c)(1)(i)(A) q 50.73(a)(2)(iii) q 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL q 20.2203(a)(2)(ii) q 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) q 50.73(a)(2)(x) q 20.2203(a)(2)(iii) q 50.36(c)(2) q 50.73(a)(2)(v)(A) q 73.71(a)(4) 100 q 20.2203(a)(2)(iv) q 50.46(a)(3)(ii) q 50.73(a)(2)(v)(B) q 73.71(a)(5) q 20.2203(a)(2)(v) q 50.73(a)(2)(i)(A) q 50.73(a)(2)(v)(C) q OTHER q 20.2203(a)(2)(vi) q 50.73(a)(2)(i)(B) q 50.73(a)(2)(v)(D)
Specify in Abstract below or in
C. Cause of Event
The root cause was determined to be the failure of the 2A GC motor with the 2B GC pump previously removed from service. The failure of the 2A GC motor was cause by a failure of the inboard motor bearing on the 2A GC pump motor due to insufficient lubrication as supplied by the vendor. This failure resulted in contact between the rotor and stator windings causing the electrical failure of the motor.
The root cause evaluation also determined that although there was grease from the coupling on the motor housing, no grease was found in the drive-end bearing or bearing housing. The bearing housing cover and the cage were inspected and neither had any grease or grease residue visibly coating them.
While the vendor refurbishment checklist documents that the bearings were re-packed, the post-failure inspection indicated that only the opposite drive-end bearing was packed with grease; the drive-end bearing was not.
Since the bearings and bearing housings are concealed by the endbells once the motor is reassembled, it was not readily apparent that the bearing was not greased.
The motor was shipped to the Vendor to further investigate and determine the underlying cause of the failure and lack of lubrication.
D. Safety Analysis
There were no safety consequences impacting plant or public safety as a result of this event. The GC system is a non-safety related design feature and is not credited in any Updated Final Safety Analysis Report chapter 15 accident or transient analyses. The reactor trip system functioned as designed and shutdown the reactor without incident. A risk analyses also indicates this event was not risk significant.
E. Corrective Actions
The 2A GC pump motor was replaced prior to start up on Unit 2. The 2B GC pump has also been repaired and returned to service to support plant operations as needed.
Inspection and review of the Unit 1 GC pump motors have been completed to ensure that all of the bearings contain the appropriate amount of grease.
The process used to review motor refurbishment and motor installation will be evaluated to determine if any additional actions are needed to verify proper grease in the bearing housings.
F.
Previous Occurrences
There have been no previous occurrences of this nature.