05000220/LER-2013-002, Regarding Unanalyzed Condition Caused by Unfused Control Room DC Ammeters
| ML14008A099 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 12/20/2013 |
| From: | John Stanley Constellation Energy Nuclear Group, EDF Group, Nine Mile Point |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 13-002-00 | |
| Download: ML14008A099 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(ix)(A) 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)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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 |
| 2202013002R00 - NRC Website | |
text
James J. Stanley Plant General Manager Office 315.349.5205 Fax 315.349.1321 E-mail: James.Stanley@cenglIc.com CENG.
a joint venture of Constellation
- VeDF Energy' NINE MILE POINT NUCLEAR STATION December 20, 2013 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION:
SUBJECT:
Document Control Desk Nine Mile Point Nuclear Station Unit 1 Renewed Facility Operating License No. DPR-63 Docket No. 50-220 Licensee Event Report 2013-002, Unanalyzed Condition Caused by Unfused Control Room DC Ammeters In accordance with 10 CFR 50.73(a)(2)(ii)(B) and 10 CFR 50.73(a)(2)(ix)(A), please find attached Licensee Event Report 2013-002, Unanalyzed Condition Caused by Unfused Control Room DC Ammeters.
There are no regulatory commitments in this submittal.
Should you have questions regarding the information in this submittal, please contact Everett (Chip)
Perkins, Director Licensing, at (315) 349-5219.
Very truly yours, JJS/JBH
Attachment:
Licensee Event Report 2013-002, Unanalyzed Condition Caused by Unfused Control Room DC Ammeters cc:
NRC Project Manager NRC Resident Inspector NRC Regional Administrator Nine Mile Point Nuclear Station, LLC P.O. Box 63, Lycoming, NY 13093
ATTACHMENT LICENSEE EVENT REPORT 2013-002 UNANALYZED CONDITION CAUSED BY UNFUSED CONTROL ROOM DC AMMETERS Nine Mile Point Nuclear Station, LLC December 20, 2013
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
I3. PAGE Nine Mile Point Unit 1 05000220j 1 OF 5
- 4. TITLE Unanalyzed Condition Caused by Unfused Control Room DC Ammeters
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME
~DOCKET NUTMBER MONTH DAY YEAR Y
SEQUENTIAL REV MONTH DAY YEARNB NUMBER NO.NAA MONTHUMBEDAY.MYEARDAYYEAR NA NA FACILITY NAME DOCKET NUMBER 10 22 2013 2013 002 00 12 20 2013 1NA NA
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) ol 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
N [1 20.2201(d)
El 20.2203(a)(3)(ii)
[l 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
[I 20.2203(a)(1)
El 20.2203(a)(4) 0 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
- 10. POWER LEVEL
[] 20.2203(a)(2)(i)
[] 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4) 100 El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[I 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
Dl 50.73(a)(2)(i)(A)
[I 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in 2013 Davis Besse Operating Experience (OE) 305419 This OE identified that, during a fire, DC ammeter circuits without protective fusing could short to ground and with the proper polarity it was possible to cause high current in these unfused legs of small diameter cabling with the potential to cause secondary fires. These secondary fires could then result in damage to adjacent cabling.
E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
A postulated control room fire could lead to the shorting event occurring in the ammeter circuits, which subsequently could lead to additional fires in the Auxiliary Control Room and Turbine Building adversely impacting equipment necessary to support safe plant shutdown.
F. METHOD OF DISCOVERY
On October 22, 2013, review of industry OE regarding the impact of unfused DC ammeter circuits in the control room determined that the described condition was applicable to NMP1.
G. MAJOR OPERATOR ACTION:
Fire patrols were established as a compensatory measure in affected areas of the unit.
H. SAFETY SYSTEM RESPONSES:
No operational conditions requiring the response of safety systems occurred as a result of this event.
II. CAUSE OF EVENT
The cause of this event is that the equipment design issue was not recognized as an unacceptable configuration. The design issue is associated with an evolving industry understanding of the Appendix R common enclosure scope. Specifically, ammeter circuits were not required to be fused in the original design of the plant nor included within the scope of Appendix R evaluation of common enclosure type circuits because the failure mode of 'ground fault equivalent hot shorts' was not known to exist until NUREG-2128,
'ELECTRA-FIRE' was published in 2013.
This event has been entered into the Nine Mile Point Nuclear Station corrective action program as condition report number CR-2013-008747.
III. ANALYSIS OF THE EVENT
This event is reportable in accordance with 10CFR50.73(a)(2)(ii)(B) ) as a condition that resulted in the nuclear plant being in an unanalyzed condition that significantly degraded plant safety, and 10 CFR 50.73(a)(2)(ix)(A) as a condition that as a result of a single cause could have prevented the fulfillment of a safety function for two or more trains or channels in different systems.
NRC FORM 366 (10-2010)
There were no actual nuclear safety consequences associated with this event. The event was caused by equipment design that did not include fusing of DC ammeter circuits due to not understanding or anticipating a failure mode that had not been not known to exist until NUREG-2128 'ELECTRA-FIRE' was published in 2013. There were no actual fires impacting to any of the four DC ammeter circuits and as a result no actual challenge to the ability of the station to safely shutdown to cold shutdown conditions.
The configuration of the DC ammeter circuits has remained unchanged from original construction at NMP 1 and as such is a legacy issue. The original design did not include any protection (i.e. fuses) for the ammeter circuits. The original guidance (Generic Letter 81-12, "Fire Protection Rule," and later Generic Letter 86-1 0, "Implementation of Fire Protection Requirements") for completing a post-fire Safe Shutdown analysis did not identify the need for the evaluation of DC ammeters as they were not relied upon to bring the unit to a Cold Shutdown state. Hence they were not analyzed for the original Appendix R Safe Shutdown analysis. It is noted that NMP1 was not orginally designed to the Appendix R Safe Shutdown requirements since those requirements were issued following Unit 1 going into operation.
Guidance used as part of the NFPA 805 transition at Unit 1, mainly NEI-00-01, "Guidance for Post-Fire Safe Shutdown Analysis" and RIS-2005-30, "Clarification of Post-Fire Safe-Shutdown Regulatory Requirements" does not identify the need for the evaluation of the ammeter circuits. The methodology described in these documents requires the evaluation of circuits which are part of the required Safe Shutdown train of equipment, as well as any circuits which could cause spurious actuations of equipment - equipment not part of the required train of Safe Shutdown equipment which could affect the units ability to safely shutdown. As these ammeter circuits are indicating circuits only and could not cause spurious actuation of any equipment, they were not required to be evaluated under this guidance and were not evaluated for the upgrade of the Safe Shutdown analysis for the transition the to NFPA 805.
Currently, the safety related DC ammeter circuits have been deenergized at the DC buses preventing this postulated scenario from being able to occur.
Based on the above discussion, it is concluded that the safety significance of this event is low and the event did not pose a threat to the health and safety of the public or plant personnel.
This event does not affect the NRC Regulatory Oversight Process (ROP) Index items.
IV. CORRECTIVE ACTIONS
A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:
- 1.
The four unfused safety related DC ammeter circuits have been deenergized at the DC buses preventing this postulated scenario firom being able to occur.
B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
- 1.
A modification will be developed, issued and installed to provide adequate fuse circuit protection to preclude the postulated event from occurring at NMPI.
NRC FORM 366 (10-2010)
V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
There were no other failed components that contributed to this event.
B. PREVIOUS LERs ON SIMILAR EVENTS:
LER 2013-003 is being submitted for a similar condition at NMP2. Additionally, Edwin I. Hatch Nuclear Plant submitted LER 2013-004 (Revision 1) on November 13, 2013 for an unanalyzed condition postulated with a fire and resulting hot short that has a similar cause. There have been no previous similar LERs for NMP1.
C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:
IEEE 803 FUNCTION IDENTIFIER COMPONENT IEEE 805 SYSTEM IDENTIFICATION EJ Ammeter II D. SPECIAL COMMENTS:
None NRC FORM 366 (10-2010)