05000249/LER-2010-001, For Dresden, Unit 3, OPRM Power Supply Failure During Maintenance Results in Unit 3 Automatic Reactor Scram

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For Dresden, Unit 3, OPRM Power Supply Failure During Maintenance Results in Unit 3 Automatic Reactor Scram
ML103550252
Person / Time
Site: Dresden Constellation icon.png
Issue date: 12/10/2010
From: Hanley T
Exelon Nuclear, Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
SVPLTR# 10-0050 LER 10-001-00
Download: ML103550252 (5)


LER-2010-001, For Dresden, Unit 3, OPRM Power Supply Failure During Maintenance Results in Unit 3 Automatic Reactor Scram
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)(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)(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
2492010001R00 - NRC Website

text

Exekn Exelon Generation Company, LLC www.exe oncorp.com Nucear Dresden Nuclear Power Station 6500 North Dresden Road Morris, IL 60450-9765 10 CFR 50.73 SVPLTR # 10-0050 December 10, 2010 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 3 Renewed Facility Operating License No. DPR-25 NRC Docket No. 50-249

Subject:

Licensee Event Report 249/2010-001-00, "OPRM Power Supply Failure during Maintenance Results in Unit 3 Automatic Reactor Scram" Enclosed is Licensee Event Report 249/2010-001-00, "OPRM Power Supply Failure during Maintenance Results in Unit 3 Automatic Reactor Scram" for Dresden Nuclear Power Station, Unit 3. This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A), Any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B).

There are no regulatory commitments contained in this submittal.

Should you have any questions concerning this letter, please contact Mr. Dennis Leggett at (815) 416-2800.

Respectfully, Tim Hanley Site Vice President Dresden Nuclear Power Station Enclosure cc:

Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station

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 Dresden Nuclear Power Station, Unit 3 05000249 1 OF 4
4. TITLE OPRM Power Supply Failure during Maintenance Results in Unit 3 Automatic Reactor Scram
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED SFACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR N/A 05000 NUMBER NO.

FACILITY NAME DOCKET NUMBER 10 11 2010 2010 001 00 12 10 2010 N/A 05000

9. OPERATING MODE
11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

El 20.2201(b)

[I 20.2203(a)(3)(i)

El 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii) 1 El 20.2201(d)

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

El 50.73(a)(2)(ii)(A)

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

El 20.2203(a)(1)

El 20.2203(a)(4)

El 50.73(a)(2)(ii)(B)

El 50.73(a)(2)(viii)(B)

E] 20.2203(a)(2)(i)

[] 50.36(c)(1)(i)(A)

[E 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

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

El 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)

[E 50.73(a)(2)(x)

El 20.2203(a)(2)(iii)

El 50.36(c)(2)

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

[1 73.71(a)(4) 100 El 20.2203(a)(2)(iv)

El 50.46(a)(3)(ii)

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

[1 73.71(a)(5)

El 20.2203(a)(2)(v)

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

[E 50.73(a)(2)(v)(C)

[I OTHER El 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B)

[E 50.73(a)(2)(v)(D)

Specify in Abstract below or in The operating procedure that was being used to transfer the RPS bus, DOP 0500-03 Reactor Protection System Power Supply Operation, contained a prerequisite to place APRM 6 in bypass prior to commencing the bus transfer. The OPRM was the only active component in the 107F relay string.

Troubleshooting indicated that OPRM 6 had no power. Further investigation revealed that the input fuse had blown on the OPRM power supply causing it to lose output power.

Initial examination of the circuit board, did not reveal any failures of board components other than the blown input fuse. The board was sent out for additional testing. No defects were identified besides the blown input fuse. The fuse was replaced and the power supply was successfully turned on. All indications were within expected ranges. Following seventy-two hours of operation, no defects were identified. The power supply was sent for a detailed failure analysis.

A failure analysis of the power supply indicates that the OPRM 5 Vdc power supply is susceptible to electrical noise.

The power supply is designed with a circuit (Crowbar Circuit) which senses voltage transients and prevents the voltage excursion from damaging voltage sensitive components downstream of the power supply output. When a voltage spike occurs, the crowbar circuit is activated, which essentially shorts the circuit to ground and blows the input fuse. This results in the power supply being turned off thus terminating the voltage transient on the down stream components.

Efforts have been made to identify the source of the electromagnetic interference. However, the source has not been identified at this time. Investigations and failure analyses are continuing in order to mitigate the affects of electromagnetic interferences on the OPRM power supplies.

D.

Safety Analysis

Following the scram, the plant response and appropriate Operator actions taken, indicates that the event is of low risk significance. The safety significance of this event is minimal due to minimal consequential impact on the health and safety of the public and reactor safety.

E.

Corrective Actions

The failed 5 Vdc power supply for OPRM 6 was replaced.

Planned work activities which require transfer of the RPS buses to their reserve power supplies are being moved to times that the OPRM system is not required to be operable. This practice will continue until a more viable resolution can be implemented.

F.

Previous Occurrences

A review of DNPS Licensee Event Reports (LERs) for the last three years did not identify any LERs associated with a failure of Nuclear Instrumentation power supplies.

G.

Component Failure Data

Manufacture Model Component Power Supply ABB Combustion Engineering 2001731-017