05000373/LER-2017-003, Regarding Automatic Reactor Scram Due to Main Generator Trip on Differential Current During Back-Feed Operations

Regarding Automatic Reactor Scram Due to Main Generator Trip on Differential Current During Back-Feed Operations

ML17104A085
Person / Time
Site:	LaSalle
Issue date:	04/14/2017
From:	Trafton W Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA17-035 LER 17-003-00
Download: ML17104A085 (4)

LER-2017-003, Regarding Automatic Reactor Scram Due to Main Generator Trip on Differential Current During Back-Feed Operations

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
3732017003R00 - NRC Website

text

Exelon Generation0 RA17-035 April 14, 2017 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Unit 1 Renewed Facility Operating License No. NPF-11 NRC Docket No. 50-373 LaSalle County Station 2601 North 21 51 Road Marseilles, IL 61341 815-415-2000 Telephone www.exeloncorp.com 10 CFR 50.73

Subject:

Licensee Event Report 2017-003-00, Automatic Reactor Scram due to Main Generator Trip on Differential Current During Back-Feed Operations In accordance with 1 O CFR 50.73(a)(2)(iv)(A), Exelon Generation Company, LLC (EGC) is submitting Licensee Event Report (LEA) Number 2017-003-00 for LaSalle County Station, Unit 1.

There are no regulatory commitments in this letter. Should you have any questions concerning this report, please contact Mr. Guy V. Ford, Jr., Regulatory Assurance Manager, at (815) 415-2800.

Respectfully, di~.ff-Site Vice President LaSalle County Station

Enclosure:

Licensee Event Report cc:

Regional Administrator - NRC Region Ill NRC Senior Resident Inspector - LaSalle County Station

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017)

, the htti;i://www.nrc.gov/reading-rm/doc-collections/nuregs/stafflsr1022/r3l)

NRC may not conduct or sponsor, and a person is not required to respond to, the inlormation collection.

3. PAGE LaSalle County Station, Unit 1 05000373 1 OF 3

4. TITLE Automatic Reactor Scram due to Main Generator Trip on Differential Current During Back-Feed Operations

5. EVENT DATE

6. LEA NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED I

SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH OAY YEAR YEAR NUMBER NO.

MONTH DAY YEAR NA NA FACILITY NAME DOCKET NUMBER 02 13 2017 2017 -

003

- 00 04 14 2017 NA NA

9. OPERATING MODE

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

D 20.2201 (bl D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2201 (d)

D 20.2203(a)(3)(ii)

D 50.73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B) 1 D 20.2203(a)(1 l D 20.2203(a)(4)

D so.13(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1 )(i)(A) 181 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x)

10. POWER LEVEL D 20.2203(a)(2)(iil D 50.36(c)(1 )(ii)(A)

D 50.73(a)(2)(v)(A)

D 13.11 (a)(4l D 20.2203(a)(2)(iiil D so.3s(c)(2)

D 50.73(a)(2)(v)(B)

D 13.11 (a)(s)

D 20.2203(a)(2)(iv)

D so.4s(a)(3)(ii) 0

• 50.73(a)(2)(v)(C)

D 13.11(a)(1) 100 D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

D 50.73(a)(2)(v)(D)

D 13.11(a)(2)(i)

D 20.2203(a)(2)(vi)

D 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 13.11(a)(2)(n)

D 50.73(a)(2)(i)(C)

D OTHER Specify In Abstract below or In REPORTABILITV AND SAFETY ANALYSIS YEAR 2017 -

3. LER NUMBER SEQUENTIAL NUMBER 003 This event is reportable in accordance with 1 O CFR 50.73(a)(2)(iv)(A) as an event or condition that resulted in manual or automatic actuation of the reactor protection system (RPS), including reactor scram. There were no safety consequences associated with the event since the RPS and other emergency safety systems functioned as designed.

CORRECTIVE ACTIONS

REV NO.

00 The immediate corrective action was to revise future switching orders to break the tie between the Unit 1 and Unit 2 345 kV ring buses when performing a back-feed to the MPT. The station also revised switching orders to isolate the Unit 1 and Unit 2 345 kV ring buses for energizing the SAT for each unit and performing generator synchronization operations.

The corrective action to prevent recurrence of a unit scram during back-feed operations is to install a more robust generator differential relay protection scheme. In addition, the switching scheme will be revised to break the tie between the Unit 1 and Unit 2 ring buses when the MPTs are energized.

PREVIOUS OCCURRENCES

A review of station Licensee Event Reports for the past three years related to reactor trips identified instances where a reactor manual or automatic scram was inserted. However, there were no previous occurrences related directly to main generator operation at the station. One event was identified related to turbine-generator run-back as follows.

LER 374-2017-001-00, Manual Reactor. Scram due to Turbine-Generator Run-Back Caused by Stem-Disc Separation in Stator Water Cooling Heat Exchanger Inlet Valve On January 23, 2017, operators initiated a manual scram of the Unit 2 reactor as a result of observing a generator run-back due to a generator stator winding cooling (GC) system malfunction. Inspections of the GC components were performed while the unit was shut down for a planned refueling outage. The cause of the GC system failure was stem-disc separation in the 'A' GC heat exchanger inlet valve. This event was reportable in accordance with 1 O CFR 50.73(a)(2)(iv)(A) as an event or condition that resulted in manual or automatic actuation of the RPS. There were no safety consequences associated with the event since there was no loss of safety function, and the RPS functioned as designed.

COMPONENT FAILURE DATA

Manufacturer: General Electric Company [GOBO]

Device: Main Generator Differential Current (CFO) Relay Trip Component ID: GE Model CFO Differential Relay 1687-MP010B Page_3_ of _3_