DCL-13-089, LER 13-005-00 for Diablo Canyon, Unit 2 Regarding Unit 2 Reactor Trip Due to Lightning Arrester Flashover
| ML13249A234 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 09/05/2013 |
| From: | Allen B S Pacific Gas & Electric Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| DCL-13-089 LER 13-005-00 | |
| Download: ML13249A234 (8) | |
Text
Pacific Gas and Electric Company September 05,2013 PG&E Letter DCL-13-089 Barry S. Allen Site Vice Pre s iden t Diablo Ca nyon P o wer P l ant Mail Code 104/6 P. O. Box 56 Avil a Beach , CA 93424 8 0 5.545.4888 In ternal: 6 91.4888 Fax: 80 5.5 45.6 445 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 10 CFR 50.73 Docket No. 50-323, OL-DPR-82 Diablo Canyon Unit 2 Licensee Event Report 2-2013-005-00, Reactor Trip due to Lightning Arrester Flashover Dear Commissioners and Staff; Pacific Gas and Electric Company (PG&E) is submitting the enclosed Licensee Event Report (LER) in accordance with 10 CFR 50.73(a)(2)(iv)(A) identifying the initiation of a reactor trip from the reactor protection system as a result of a lightning arrestor flashover of a 500 kV insulator.
This is the initial LER submittal.
PG&E will submit a supplemental LER describing event cause and corrective actions no later than January 23, 2014. PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this report. This event did not adversely affect the health and safety of the public. Sincerely,
!-Barry S. Allen J8L3/4486/50573100 Enclosure cc: Thomas R. Hipschman, NRC Senior Resident Inspector Jennivine K. Rankin, NRR Project Manager Steven A. Reynolds, Acting NRC Region IV INPO Diablo Distribution A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway. Comanche Peak. Diablo Canyon. Palo Verde. San Onofre. South Te x as Project. Wolf Creek NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIAIPrivacy Section (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to infocollects.resource@nrc.gov, and to the Desk Officer, Office of Information LICENSEE EVENT REPORT (LER) and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information (See reverse for required number of collection does not display a currently valid OMB control number, 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 2. DOCKET NUMBER 3. PAGE Diablo Canyon Power Plant, Unit 2 05000 323 1 OF 4 4. TITLE Unit 2 Reactor Trip due to Lightning Arrester Flashover
- 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED ISEQUENTIALI REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO. MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 07 10 2013 2013 0 09 05 2013 05000 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check aI/that apply) 1 o 20.2201(b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C)
D 50.73(a)(2)(vii) o 20.2201(d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4) o 50.73(a)(2)(ii)(8)
D 50.73(a)(2)(viii)(8) o 20.2203(a)(2)(i) o 50.36(c)(1)(i)(A) o 50.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL o 20.2203(a)(2)(ii) o 50.36(c)(1)(ii)(A)
[(] 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x) o 20.2203(a)(2)(iii) o 50.36(c)(2) o 50.73(a)(2)(v)(A) o 73.71(a)(4) 100 o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii) o 50.73(a)(2)(v)(8) o 73.71 (a)(5) o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C) o OTHER o 20.2203(a)(2)(vi) o 50.73(a)(2)(i)(8) o 50.73(a)(2)(v)(D)
Specify in Abstract below or in NRC Form 366A 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME I TELEPHONE NUMBER (Include Area Code) Joe Loya, Sr. Engineer, Regulatory Services (805) 545-4486 13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANU-REPORTABLE CAUSE SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR [{] YES (If yes, complete 15. EXPECTED SUBMISSION DATE) DNO SUBMISSION DATE 01 23 2014 ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On July 10,2013, at 09:50 PDT, while performing the periodic hot-washing of the 500 kV insulators, a flashover of the Phase A 500 kV to ground across the Phase A lightning arrestor occurred and actuated the 500 kV differential relay. The actuation of the 500 kV differential relay opened the Unit 2 generator output breakers to isolate the generator, which then actuated a turbine trip. Since Unit 2 was operating above the 50 percent power permissive, the reactor protection system initiated a Unit 2 reactor trip. All plant equipment responded as designed.
This is the initial Licensee Event Report (LER) for this event. Pacific Gas & Electric will submit a supplemental LER describing event cause and corrective actions no later than January 23, 2014. There were no personnel injuries, no offsite radiological releases, and no damage to safety-related equipment associated with this condition.
This condition did not have an adverse effect on the health and safety of the public. NRC FORM 366 (10-2010)
NRC FORM 366A (10-2010)
LICENSEE EVENT REPORT (LER)U.S.
NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET Diablo Canyon Power Plant, Unit 2 YEAR 05000 323 2013 NARRATIVE I. Plant Conditions
- 6. LER NUMBER I SEQUENTIAL I NUMBER 005 REV NO. 00 3. PAGE 2 OF At the time of the event, Diablo Canyon Power Plant (DCPP) Units 1 and 2 were in Mode 1 (Power Operation) at approximately 100 percent reactor [RCT] power with normal operating reactor coolant temperature and pressure.
II. Problem Description A. Background 4 DCPP is equipped with a Class IE alternating current (AC) electrical power distribution system [EB] that is divided into three load groups. The power sources for this system consist of two physically-independent offsite sources and multiple on site standby power sources (three diesel generators (DGs)[DG) for each unit). These systems have independent controls, independent protection, and separate switchyards, transmission lines, and tie-lines to the plant. In the normal alignment, the power produced at DCPP is transmitted offsite via the 500 kV system [EL) and also feeds normal onsite loads via the auxiliary transformer
[XFMR). Backup power is available immediately via the 230 kV system [EK] and startup transformer.
In the event of a loss of 230 kV power, backup power is available from onsite DGs. The AC electrical power sources provide sufficient capacity, capability, redundancy, and reliability to ensure the availability of necessary power to engineered safety systems so that the fuel, reactor coolant system [AB], and containment
[NH] design limits are not exceeded.
Each phase of the main bank transformers has an associated lightning arrester (LA) connected to the 500 kV line between the transformer high voltage bushing and the first transmission line tower out from the transformer yard. The LAs are designed to protect the high voltage winding of its associated transformer against impulse and switching surges on the transmission line. A hot-washing of the 500 kV dead-end insulators has been conducted every 6 weeks since about 1996. The purpose of hot-washing is to remove contaminants.
Contamination buildup degrades the insulating capability, and increases the possibility of a flashover.
B. Event Description On July 10,2013, while performing the periodic hot-washing of the 500 kV dead-end insulators, a flashover of Phase A 500 kV to ground across the Phase A LA occurred and actuated the 500 kV differential relay. The actuation of the 500 kV differential relay opened the Unit 2 generator output breakers to isolate the generator which then actuated a turbine trip. Since Unit 2 was operating above the 50 percent power permissive, the reactor protection system initiated a Unit 2 reactor trip. All plant equipment responded as designed.
All three Unit 2 auxiliary feedwater (AFW) pumps [P] started, the containment fan [FAN] cooling units started and ran in slow speed, and the standby auxiliary saltwater train started, all as expected.
NRC FORM 366A (10-2010)
NRC FORM 366A (10-2010)
LICENSEE EVENT REPORT (LER) u.s. NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET Diablo Canyon Power Plant, Unit 2 05000 323 NARRATIVE YEAR 2013 6. LER NUMBER I SEQUENTIAL I NUMBER 005 C. Status of Inoperable Structure, Systems, or Components That Contributed to the Event None. D. Other Systems or Secondary Functions Affected None. E. Method of Discovery REV NO. 00 Annunciators in the control room alerted licensed control room operators of the 500 kV system problem. F. Operator Actions 3. PAGE 3 OF 4 Plant operators verified appropriate plant trip response using Emergency Operating Procedure (EOP) E-O, "Reactor Trip or Safety Injection," and EOP E-O.l, "Reactor Trip Response." G. Safety System Responses Vital buses transferred from auxiliary power to startup power as designed.
III. Cause Pacific Gas and Electric (PG&E) is conducting a root cause evaluation (RCE) and will submit a supplemental Licensee Event Report (LER) documenting the results of this investigation once it is complete.
IV. Assessment of Safety Consequences There were no safety consequences as a result of this event. The transfer of plant loads to startup occurred as designed.
Equipment necessary for Unit 2 decay heat removal was available and operated as required by plant design. Unit 1 remained at full power and all of its vital buses remained powered by auxiliary power. Therefore, the event is not considered risk significant and did not adversely affect the health and safety of the public. V. Corrective Actions A. Immediate Corrective Action Suspended hot-wash activities pending results of the RCE and establishment of controls determined as necessary as a result of this event. B. Once the RCE is complete, PG&E will take corrective actions as prudent, and describe the corrective actions in a supplemental LER to the NRC. NRC FORM 366A (10-2010)
NRC FORM 366A (10-2010)
- 1. FACILITY NAME Diablo Canyon Power Plant, Unit 2 NARRATIVE VI. Additional Information A. Failed Components None. B. Previous Similar Events LICENSEE EVENT REPORT (LER) u.s. NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET 2. DOCKET YEAR 05000 323 2013 6. LER NUMBER I SEQUENTIAL I NUMBER REV NO. 005 .. 00 3. PAGE 4 OF 4 On October 11, 2012, at 12:08 PDT, the DCPP Unit 2500 kV line differential relay actuated, resulting in a unit trip. The 500 kV coupling capacitor voltage transformer (CCVT) bushing experienced a flashover to ground, resulting in a unit trip and turbine trip. With the turbine tripped and Unit 2 operating above the 50 percent power permissive, the reactor protection system initiated a reactor trip as designed.
All plant equipment, including the auto-start of the AFW system, responded as designed.
At the time of the event, the environmental conditions consisted of light rain. PG&E determined that the causes of the bushing failure were inadequate insulator material performance and inadequate engineering design practices.
Additionally, an unintended AFW pump restart occurred following this event as a result of a procedure deficiency that was created when the procedure was not revised following a plant modification.
PG&E revised the procedure and supporting documents and performed tailboards with the procedure writing staff on use of the supporting documents to identify all changes required by a plant modification.
CCVTs have now all been relocated to the switchyard and are no longer at the transformer location.
NRC FORM 366A (10-2010)