05000368/LER-2006-001, Completion of a Plant Shutdown Required by Technical Specifications Due to Loss of Motive Power to Certain Containment Isolation Valves as a Result of a Phase to Ground Short Circuit
| ML070030511 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 12/21/2006 |
| From: | James D Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2CAN120601 LER 06-001-00 | |
| Download: ML070030511 (9) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 3682006001R00 - NRC Website | |
text
- Entegy
.,Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR 72802 Tel 479-858-4619 Dale E. James Manager, Licensing - ANO 2CAN120601 December 21, 2006 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
Subject:
Licensee Event Report 50-368/2006-001-00 Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NFP-6
Dear Sir or Madam:
In accordance with 10CFR50.73(a)(2)(i)(A), enclosed is the subject report concerning completion of a plant shutdown required by Technical Specifications.
Commitments made in this submittal are identified in the attachment to the enclosure.
fSi S.
- rely, Manag, Licensing DEJ/re Enclosure
2CAN120601 Page 2 of 2 cc:
Dr. Bruce S. Mallett Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339-5957 LEREvents@inpo.org
1 NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007
, the NRC may not conduct or sponsor, and a person is not required to respond to, the diaits/characters for each block)
Information collection.
- 3. PAGE Arkansas Nuclear One - Unit 2 050003681 1 OF 5
- 4. TITLE Completion of a Plant Shutdown Required by Technical Specifications Due to Loss of Motive Power to Certain Containment Isolation Valves as a Result of a Phase to Ground Short Circuit in a Motor Control Cubicle
- 5. EVENT DATE
- 6. LER NUMBER__
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENUMLB REV MONTH DAY YEAR I
05000 NUMBER NO.05 0
FALITY NAME DOCKET NUMBER 10 30 2006 2006 001 00 12 21 2006 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
[O 20.2201(b)
[3 20.2203(aX3)(i)
[I 50.73(a)(2)(iXC)
[3 50.73(a)(2)(vii)
[1 20.2201(d)
[I 20.2203(aX3)(ii)
[I 50.73(aX2)(ii)(A)
[I 50.73(aX2XviiiXA)
[o 20.2203(a)(1)
[I 20.2203(aX4)
[3 50.73(aX2)(ji)(B) 0 50.73(a)(2XviiiXB) 0 20.2203(a)(2Xi)
[3 50.36(cX1)(i)(A)
[I 50.73(aX2)(iii)
[0 50.73(a)(2)ix)(A)
- 10. POWER LEVEL 0 20.2203(aX2Xii)
[0 50.36(c)(1)(iiXA)
[0 50.73(aX2)(ivXA) 0 50.73(a)(2Xx) o 20.2203(aX2)Ciii)
[0 50.36(c)(2) 0 50.73(aX2)(v)(A) 0 73.71(a)(4) 67 0 20.2203(aX2)(iv)
[3 50.46(a)(3)(ii) 0 50.73(aX2)(v)(B) 0 73.71(a)(5)
[o 20.2203(aX2)(v)
I@ 50.73(aX2)(iXA) 0 50.73(aX2)(v)(C)
[0 OTHER [3 20.2203(a)(2Xvi) 0 50.73(aX2)(i)(B) 0 50.73(aX2)(v)(D)
Specify In Abstract below
- 12. LICENSEE CONTACT FOR THIS LIER NAME ITELEPHONE NUMBER (Indude Area Code)
R.H. Scheide, Nuclear Safety and Licensing Specialist
. 479-858-4618
- 13. COMPLETE ONE MNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT
CAUSE
SYSTEM COMPONENT FMANU REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX B
ED 52 1005 Y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 0 NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
At 1925 CST, on October 30, 2006, Arkansas Nuclear One, Unit 2 (ANO-2), initiated a plant shutdown as required by Technical Specifications because certain containment isolation valves were inoperable as a result of loss of their motive power. The reactor was manually tripped at 2134 CST, in accordance with the plant shutdown procedure. Power was lost to the valves at 1238 when the supply circuit breaker for 480 VAC motor control cubicle (MCC) 2B-53 tripped as a result of a bus to ground electrical fault. At 1244, operators dispatched to investigate the breaker trip discovered a small fire in the MCC, which they immediately extinguished. ANO-2 declared an Alert at 1304 due to a fire which affected one train of safety related equipment. Plant conditions remained stable at 67 percent power while the extent of damage was evaluated until 1925, when plant shutdown was initiated to facilitate repairs. The alert was terminated at 2000 on October 30, 2006. Repairs were completed and the unit returned to power operation at 0609 CST, on November 1, 2006. The root cause of this event was determined to be an inadequate MCC design that resulted in improper placement of a circuit breaker in the MCC. One of the three phase stabs did not make up to its associated bus bar correctly, resulting in a high resistance connection that caused melting of the stab's spring clip. An acceptable method for verifying proper stab engagement during breaker installation will be developed and incorporated into appropriate procedures.
NRC FORM 366 (6-2004)
NR OM36A..NULA-EGLTR.CMISO (if more space is required, use additional copies of NRC Form 3664)
A.
Plant Status At the time of this event, Arkansas Nuclear One, Unit 2 (ANO-2) was operating in Mode 1 at approximately 67 percent power. Power ascension to full power was in progress after Refueling Outage 2R18.
B.
Event Description
At 1238 CST, on October 30, 2006, the ANO-2 Control Room received several alarms concurrent with the attempted start of Containment Cooling Fan 2VSF-1A [BK]. Investigation revealed that the supply circuit breaker for Motor Control Cubicle (MCC) 2B-53 [EC] had tripped. This MCC supplies power to 2VSF-1A and several additional Technical Specifications (TS) related components (Red Train).
Shortly after the alarms were received, a fire alarm associated with the 2B-53 switchgear room was also received. At 1244, ANO-2 entered abnormal operating procedure OP-2203.034 (Fire or Explosion) due to a report of smoke emanating from the 2B-53 switchgear room. At 1248, operators on the scene reported that the source of smoke was a small fire in MCC 2B-53 and that the fire had been extinguished.
At 1304, ANO-2 declared an Alert Emergency Class based on a fire that affected one train of safety related equipment. Appropriate notifications to offsite organizations, including the NRC, were made, as required.
The loss of the 2B-53 MCC resulted in entry into several TS action statements, the most limiting of which was TS 3.6.3.1, Action D, which requires that an inoperable containment isolation valve be retumed to operable status or the associated penetration be isolated within four hours or that the unit be placed in Hot shutdown in six hours and cold shutdown in the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Red train containment isolation valves affected by the loss of MCC 2B-53 were component cooling water supply and return to the reactor coolant pumps, main feedwater block valves, main steam [SJ] isolation valve bypass, and the main steam supply to emergency feedwater [BA] pump 2P-7A.
Other TS Action Statements entered included; TS 3.7.1.2 (red train of emergency feedwater inoperable), TS 3.6.2.3 (red train of containment coolers inoperable), TS 3.7.3.1 (red train of service water [BI] inoperable), and TS 3.8.1.1.b and TS 3.4.4 (#1 emergency diesel generator [EK] inoperable due to loss of its fuel oil transfer pump). As a result of declaring the red train of service water inoperable, the action statements of TS 3.5.2.b (ECCS), TS 3.6.2.1 (Containment Spray [BE]), and TS 3.7.6.1 (Control Room Emergency Ventilation) were also entered.
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A)
E.
Safety Significance (Continued)
ANO electrical systems are designed to provide protection from extended overload and fault current conditions that could result in significant damage to the plant. During this event, the supply circuit breaker for 2B-53 opened upon sensing the fault current condition, thereby removing the source of energy that was feeding the fire. The fire was completely contained within the MCC and was quickly extinguished.
Considering that redundant safety related systems remained operable and capable of mitigating any design basis event had the need arisen, and that the fire was contained within a single MCC and quickly extinguished, thereby minimizing damage to plant equipment, this event was of minimal safety significance.
F.
Basis for Reportability 10CFR50.72(a) requires immediate NRC notification of the declaration of an emergency class.
In addition, 10CFR50.72(b)(2)(i) requires an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> notification regarding the initiation of any nuclear plant shutdown required by the plant's Technical Specifications whereas 10CFR 50.73(a)(2)(i)(A) requires a 60 day report regarding the completion of any nuclear [plant shutdown required by the plant's Technical Specifications.
As this event involved the declaration of an emergency class and the initiation and completion of a plant shutdown required by the plant's Technical Specifications, it is reportable pursuant to the above referenced criteria.
All required reports were made, as required by regulation.
G.
Additional Information
A previous similar event was reported by ANO in Licensee Event Report 50-368/1991-007-00.
However, the corrective actions implemented in association with that event were not adequate in preventing the event discussed in this report.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
Attachment 2CAN120601 List of Regulatory Commitments
Attachment to 2CAN1 20601 Page 1 of 1 List of Regulatory Commitments The following table identifies those actions committed to by Entergy in this document. Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments.
TYPE SCHEDULED (Chek One)
COMPLETION ONE TIME CONTINUING DATE
COMMITMENT
ACTION COMPLIANCE (If Required)
Develop an acceptable method to verify proper bus stab engagement ANO-1: 3/15/2007 for motor control cubicles which X
cannot be accessed from the panel ANO-2: 6/15/2007 back and incorporate into appropriate procedures and work instructions.
Determine if installation of new style insulating barriers in all ANO-1 and 2 X
3/13/2007 ITE MCCs is appropriate.