05000461/LER-2011-007, Regarding Unfused DC Ammeter Circuits Result in Unanalyzed Condition

Regarding Unfused DC Ammeter Circuits Result in Unanalyzed Condition

ML12053A099
Person / Time
Site:	Clinton
Issue date:	01/27/2012
From:	Noll W Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
U-604052 LER 11-007-00
Download: ML12053A099 (4)

LER-2011-007, Regarding Unfused DC Ammeter Circuits Result in Unanalyzed Condition

Event date:
Report date:
Reporting criterion:	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)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 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
4612011007R00 - NRC Website

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Nuclear Clinton Power Station 8401 Power Road Clinton, IL 61727 U-604052 10 CFR 50.73 January 27, 2012 SRRS 5A.108 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461

Subject:

Licensee Event Report 2011-007-00 Enclosed is Licensee Event Report (LER) No. 2011-007-00: Unfused DC Ammeter Circuits Result in Unanalyzed Condition. This report is being submitted in accordance with the requirements of 10 CFR 50.73.

There are no regulatory commitments contained in this report.

Should you have any questions concerning this report, please contact A. Khanifar, at (217) 937-3800.

Respectfully, William G. Noll

~Ad Site Vice President Clinton Power Station JLP/blf

Enclosure:

Licensee Event Report 2011-007-00 cc:

Regional Administrator, NRC Region III NRC Senior Resident Inspector, Clinton Power Station Office of Nuclear Facility Safety, IEMA Division of Nuclear Safety

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)

, the NRC may sfor each block)inot conduct or sponsor, and a person is not required to respond to, the digits/characters frecblk)information collection.

3. PAGE Clinton Power Station, Unit 1 05000461 1 OF 3

4. TITLE Unfused DC Ammeter Circuits Result in Unanalyzed Condition

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED IFACILITY NAME DOCKET NUMBER MONT DAY YEAR YEARSEQUENTIAL REV MONTH DAY YEAR YEAR SUEN NO.R MONTH DAY YEAR NA 05000 FACILITY NAME DOCKET NUMBER 12 08 2011 2011 007 00 01 27 2012 NA 05000

9. OPERATING MODE

11. THIS REPORTIS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

[o 20.2201(b)

El 20.2203(a)(3)(i)

[I 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii) 5 0l 20.2201(d)

[E 20.2203(a)(3)(ii)

[I 50.73(a)(2)(ii)(A)

El 50.73(a)(2)(viii)(A)

[o 20.2203(a)(1)

[I 20.2203(a)(4)

ED 50.73(a)(2)(ii)(B)

I] 50.73(a)(2)(viii)(B)

O 20.2203(a)(2)(i)

El 50.36(c)(1)(i)(A)

[I 50.73(a)(2)(iii)

[I 50.73(a)(2)(ix)(A)

10. POWER LEVEL Q 20.2203(a)(2)(ii)

[I 50.36(c)(1)(ii)(A)

El 50.73(a)(2)(iv)(A)

[I 50.73(a)(2)(x)

El 20.2203(a)(2)(iii) 0l 50.36(c)(2)

El 50.73(a)(2)(v)(A) 0l 73.71(a)(4) 000 El 20.2203(a)(2)(iv)

[I 50.46(a)(3)(ii)

El 50.73(a)(2)(v)(B)

El 73.71(a)(5)

El 20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A)

El 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

C. CAUSE OF EVENT

Review of industry standards for DC Auxiliary Power Systems identified that the design of this system meets all general design criteria contained in Institute of Electrical and Electronics Engineers (IEEE) Standard IEEE-484, Recommended Practice for Installation Design and Installation of Large Lead Storage Batteries for Generating Stations and Substations, and IEEE-946, Recommended Practice for the Design of DC Auxiliary Powered Systems for Generating Stations. These design requirements do not specify protection for shunt fed ammeter circuits. The design standard used at CPS for the DC system does not specify fusing for the ammeter shunt circuit and references IEEE-946. The premise for this event to occur requires two concurrent extremely low resistance (hard) grounds (i.e., one on the positive side of the battery through the ammeter circuit wiring routed to the control room and one on the negative side of the battery through a second ground on the same battery system). The DC distribution system is floating with no established ground other than the high resistance ground provided through the ground detector [GDET]. It is designed in this manner to allow the system to withstand one hard ground (zero resistance) with no adverse affect on the operation of any equipment fed from the DC system. Since this is a very low probability event, it was likely not considered during the development of the related IEEE standards, which are typically developed and refined based on industry experience.

D. SAFETY CONSEQUENCES

This event is reportable in accordance with 10 CFR 50.73 (a)(2)(ii)(B) as a condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety in that the overloaded ammeter wiring could damage other wiring in physical contact with the cable and result in a loss of the associated safe shutdown function/capability.

There were no actual consequences for this event. An extent of condition review determined that this issue applies to the Division 1, 2 and 4 DC ammeter circuit wiring. The Division 3 DC system is not affected because it does not contain a remote MCR ammeter circuit.

Testing performed for other stations in similar applications have determined that IEEE-383 rated wiring sized for this application is not susceptible to self ignition. Industry experience discussed in NUREG/CR-6738, Risk Methods Insights Gained from Fire Incidents, supports that self ignition and fire propagation of IEEE-383 rated wiring is highly unlikely.

E. CORRECTIVE ACTIONS

Compensatory fire watch measures have been implemented for the affected areas in the plant and will remain in effect until the deficiency is corrected.

A modification is planned to correct the design deficiency.

F. PREVIOUS OCCURRENCES

A review was performed and it was determined that no similar conditions have occurred in the past.

G. COMPONENT FAILURE DATA

None