05000272/LER-2014-004
On May 7, 2014 at 0456, Salem Unit 1 experienced an automatic reactor trip. The direct cause of the reactor trip was a generator lockout resulting from a main generator differential relay trip. All control rods fully inserted on the trip. All three Auxiliary Feedwater (AFW) pumps started as expected in response to low steam generator levels and decay heat was removed by the steam dumps to the main condenser. Operators entered the emergency procedures for the plant trip and stabilized the plant in Mode 3 (HOT STANDBY).
The Main Generator Differential Relay tripped due to a failed wiring termination on the A Phase Neutral Generator Current Transformer (CT). The failed wiring termination was repaired. This report is made in accordance with 10 CFR 50.73 (a)(2)(iv)(A), " ... any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B) ... " due to an automatic reactor trip and actuation of the AFW system. Contents
TO EPIXYes CAUSE8 DAY YEAR MONTH 15. EXPECTED SUBMISSIONDATE1. SUPPLEMENTAL REPORT EXPECTED0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE) ~NO SYSTEMELCOMPONENTXCTMANU- FACTURERW120 SYSTEM COMPONENT MANU- FACTURERREPORTABLETO EPIXReported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555·0001, or by internet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-1 0202, (3150-01 04), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currentl) valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. PAGE4. TITLE Reactor Trip Due to Actuation of Generator Protection 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEARMONTH DAY YEARFACILITY NAME DOCKET NUMBER05000 05 07 201 4 201 4 -004 -000 07 03 201 4 FACILITY NAME DOCKET NUMBER05000 9. OEPRATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 10 CFR : all that apply) 1 D 20.2201(b) D 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C) D 50.73(a)(2)(vii) D 2o.2201(d) D 20.2203(a)(3)(ii) D 50.73(a)(2)(ii)(A) D 50.73(a)(2)(viii)(A) D 20.2203(a)(1) D 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) D 50.73(a)(2)(viii)(B) 10. POWER LEVEL 97% D 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) D 50.73(a)(2)(iii) D 50.73(a)(2)(ix)(A) D 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A) ~ 50.73(a)(2)(iv)(A) D 50.73(a)(2)(x) D 20.2203(a)(2)(iii) D 50.36(c)(2) D 50.73(a)(2)(v)(A) D 73.71(a)(4) D 20.2203(a)(2)(iv) D 50.46(a)(3)(ii) D 50.73(a)(2)(v)(B) D 73.71(a)(5) D 20.2203(a)(2)(v) D 50.73(a)(2)(i)(A) D 50.73(a)(2)(v)(C) 0 OTHER D 20.2203(a)(2)(vi) D 50.73(a)(2)(i)(B) Specify in Abstract below or in NRC Form D 50.73(a)(2)(v)(D) 366A 12. LICENSEE CONTACT FOR THIS LER13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORTPLANT AND SYSTEM IDENTIFICATIONWestinghouse - Pressurized Water Reactor (PWR/4) Main Generator {EU-} IDENTIFICATION OF OCCURRENCEEvent Date: May 7, 2014 Discovery Date: May 7, 2014 CONDITIONS PRIOR TO OCCURRENCESalem Unit 1 was in operational Mode 1 , steady-state, operating at 97 percent rated thermal power. No additional structures, systems or components were inoperable at the time of discovery that contributed to this event. DESCRIPTION OF OCCURRENCEOn May 7, 2014 at 0456, Salem Unit 1 experienced a reactor trip due to a generator lockout resulting from a main generator differential relay trip. Generator protection lockout circuitry tripped the generator and turbine which tripped the reactor. All control rods fully inserted on the trip. All three AFW pumps started as expected in response to low SG levels and decay heat was removed by the steam dumps to the main condenser. Operators entered the emergency procedures for the plant trip and stabilized the plant in Mode 3 (HOT STANDBY). CAUSE OF OCCURRENCEA failed wiring termination on the Unit 1, A Phase Neutral Generator CT {EL/XCT} caused the Generator Differential Trip to occur. A root cause investigation was performed to address this and the previous generator CT connection failure event on April 13, 2014. The root cause was determined to be an improper termination of the CT lead wire to field wire connection. A contributing cause was that the extent of condition visual examination and testing to identify potential common mode failures was not adequately challenged by the station. Failure analysis determined that the CT connection insulating tape failed due to chronic thermal fatigue permitting moisture intrusion due to inadequate environmental controls. The Salem Unit 2 generator is a different, General Electric (GE) manufactured design which is exposed to lower operating temperatures and has a different CT termination design. PREVIOUS OCCURRENCESA review of Licensee Event Reports at Salem Station going back to 2001 identified two other similar events: Transformer Field Wiring" describes a degraded wire termination associated with the "A" Phase Main Generator Neutral CT as well as degradation of the CT itself, occurring on May 22, 2001. The affected field wiring was replaced and the CT was abandoned in place. lockout event on April 13, 2014, due to a failed wiring termination on the C Phase neutral generator current transformer. The wire termination was repaired. SAFETY CONSEQUENCES AND IMPLICATIONSThere were no safety consequences associated with this event. Operators appropriately responded to the reactor trip to stabilize the plant. All plant safety systems operated as required. A review of this event determined that a Safety System Functional Failure (SSFF) as defined in Nuclear Energy Institute (NEI) 99-02, Regulatory Assessment Performance Indicator Guideline, did not occur. CORRECTIVE ACTIONS1. All Unit 1 main generator CT field wires and terminations on all 18 CTs were replaced. 2. All Unit 1 main generator line and neutral CTs were tested. All testing results were satisfactory. 3. A preventative maintenance task will be implemented to periodically inspect and test all Unit 1 main generator CT connections. 4. The procedure governing cable termination methods will be changed to provide specific guidance for Unit 1 CT lead and field wire terminations. 5. Leadership training will be provided for improvement to equipment reliability technical conscience and proper review/challenge of equipment issues. COMMITMENTSNo commitments are made in this LER. |
| Salem Generating Station - Unit 1 | |
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| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2722014004R00 - NRC Website | |
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