05000374/LER-2018-001-01, Manual Reactor Scram Due to Main Condenser Vacuum Degradation
| ML19015A070 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 01/15/2019 |
| From: | Washko J Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA19-001 LER 2018-001-01 | |
| Download: ML19015A070 (4) | |
| 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)(iii) 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) |
| 3742018001R01 - NRC Website | |
text
Exelon Generation RA19-001 January 15, 2019 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Unit 2 Renewed Facility Operating License No. NPF-18 NRC Docket No. 50-374 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 2018-001-01, Manual Reactor Scram due to Main Condenser Vacuum Degradation In accordance with 1 O CFR 50.73(a)(2)(iv)(A), Exelon Generation Company, LLC (EGC) is submitting Licensee Event Report (LER) Number 2018-001-01 for LaSalle County Station, Unit 2.
There are no regulatory commitments in this letter. Should you have any questions concerning this report, please contact Ms. Dwi Murray, Regulatory Assurance Manager, at (815) 415-2800.
Respectfully, ro-ilw)~
John Washko Plant Manager 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*2018)
Estinated burtlen per response to comply with this mandatory collection request* 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />
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- 4. Title Manual Reactor Scram due to Main Condenser Vacuum Degradation
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved I
Sequential I Rav Facility Name Docket Number Month Day Year Year Number No.
Month Day Year NA NA Facility Name Docket Number I 08 31 18 2018 - 001 01 01 15 19 NA NA
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 1 O CFR §: (Check all that apply)
D 20.2201(b)
D 20.2203(a)(3)(i)
D 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)
D 20.2203(a)(4)
D 50.73(a)(2)(iii)
D 50. 73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
D 50.36(c)(1 )(i)(A)
IZI 50. 73(a)(2)(iv)(A)
D 50.73(a)(2)(x) 1 O. Power Level D 20.2203(a)(2)(ii)
D 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.71 (a)(4)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71(a)(5)
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 13.77(a)(1>
29 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(a)(2)(i)
D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(ii)
D 50.73(a)(2)(i)(C)
D Other (Specify in Abstract below or in REPORT ABILITY AND SAFETY ANALYSIS SEQUENTIAL NUMBER 001 REV NO.
01 The event was reported on August 31, 2018 (ENS 53576) in accordance with 10 CFR 50.72(b)(2)(iv)(B) for an RPS actuation. This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in a valid actuation of the RPS.
While operating at approximately 29 percent power, a reactor manual scram signal was inserted on Unit 2 due to main condenser vacuum degrading. The turbine was tripped following the scram. During the scram, one control rod did not fully insert but was manually fully inserted. The plant was in a stable condition, with reactor pressure being maintained by the turbine bypass valves, and reactor water level was controlled using feedwater. Except for the single control rod insertion, required safety systems and shutdown equipment performed as expected, and there was no impact to Unit 1.
CORRECTIVE ACTIONS
Immediate corrective actions taken in response to the condition were:
Operations personnel performed the required plant shutdown.
A more robust welded temporary patch was installed on the drain header with a complete header replacement scheduled in the upcoming Unit 2 Refuel Outage L2R17.
Procedure revisions were implemented as an interim action, to minimize the risk of a similar issue with the SPE loop seal during the start-up from L2M20.
Additional corrective actions identified from the root cause investigation are:
Install a design change to eliminate the Unit 1 and Unit 2 main steam 1 (2)MS08MA/B restriction orifices and install blanks in place as the corrective action to prevent recurrence.
Replace the 2TEC5A header during the next Unit 2 refueling outage L2R17.
Perform component failure analysis of the 2TEC5A header and evaluate for potential additional actions.
Enhance work instructions and procedures related to temporary leak repairs and significant challenges to maintaining off-gas air in-leakage or main condenser vacuum.
Perform training gap analysis, with specific actions to address the technical aspects of the event and reinforce the appropriate behaviors, and to enhance training for mechanical engineers regarding piping failure mechanisms.
PREVIOUS OCCURRENCES
Searches were performed of the LaSalle Corrective Action Program (CAP) database, operating experience records, and licensee event reports for the previous three years. No similar previous events for LaSalle Station was identified for the system or failure mode. However, one event was found that involved a pipe vent valve leakage as listed below.
LEA 37 4-2015-003-00 On August 7, 2015, LaSalle Unit 2 was in Mode 3 for a planned maintenance outage. During the initial drywell entry, a steam leak was observed on the reactor recirculation (RR) system line 2RR94AB-3/4", which is upstream of valve 2833-FOSOB (RR Pump Discharge Valve 2833-F067B Inspection Port - Reactor Side Upstream Stop Valve). The leak was determined to be pressure boundary leakage. Technical Specification 3.4.5, "RCS Operational Leakage," Required Actions C.1 and C.2 were entered, which required the unit to be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Mode 4 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />, respectively. The cause of the steam leak was determined to be poor weld quality and vibration induced fatigue. The weld was repaired during the maintenance outage.
COMPONENT FAILIRE DATA Manufacturer: NA Device: Turbine Drain Collecting Water Piping Component ID: 2TEC5A, Header, Piping, 8 Inch, for Turbine Drain Collection Water Piping (Cat ID 0001400796-4) Page _3_ of _3_