05000323/LER-2013-005, Regarding Unit 2 Reactor Trip Due to Lightning Arrester Flashover

Regarding Unit 2 Reactor Trip Due to Lightning Arrester Flashover

ML13249A234
Person / Time
Site:	Diablo Canyon
Issue date:	09/05/2013
From:	Allen B Pacific Gas & Electric Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
DCL-13-089 LER 13-005-00
Download: ML13249A234 (8)

LER-2013-005, Regarding Unit 2 Reactor Trip Due to Lightning Arrester Flashover

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)(8) 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)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(8) 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)(8)
3232013005R00 - NRC Website

text

Pacific Gas and Electric Company September 05,2013 PG&E Letter DCL-13-089 Barry S. Allen Site Vice President Diablo Canyon Power Plant Mail Code 104/ 6 P. O. Box 56 Avila Beach, CA 93424 805.545.4888 Internal: 691. 4888 Fax: 805.545. 6445 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,

~I'I'-~J..J_ !-

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 Texas Project. Wolf Creek

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.

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 -

5 -

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 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.

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.