05000254/LER-2019-002, Phase to Ground Fault in Isolated Phase Bus Duct Led to Generator Trip and an Automatic Scram
| ML19296B206 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 10/23/2019 |
| From: | Ohr K Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVP-19-074 LER 2019-002-00 | |
| Download: ML19296B206 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iii) 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) |
| 2542019002R00 - NRC Website | |
text
Exelon Generation.
SVP-19-074 October 23, 2019 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Quad Cities Nuclear Power Station, Unit 1 Renewed Facility Operating License No. DPR-29 NRG Docket No. 50-254 10 CFR 50.73
Subject:
Licensee Event Report 254/2019-002-00 "Phase to Ground Fault in Isolated Phase Bus Duct Led to Generator Trip and an Automatic SCRAM" Enclosed is Licensee Event Report 254/2019-002-00 "Phase to Ground Fault in Isolated Phase Bus Duct Led to Generator Trip and an Automatic SCRAM," for Quad Cities Nuclear Power Station, Unit 1.
This report is submitted in accordance with 1 O CFR 50.73(a)(2)(iv)(A) for an event or condition that resulted in automatic actuation of the reactor protection system (RPS) causing a SCRAM, and containment isolation signals affecting containment isolation valves in more than one system.
There are no regulatory commitments contained in this letter.
Should you have any questions concerning this report, please contact Rachel Luebbe at (309) 227-2813.
Kenneth S. Ohr Site Vice President Quad Cities Nuclear Power Station cc:
Regional Administrator - NRG Region Ill NRG Senior Resident Inspector - Quad Cities Nuclear Power Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04*2018)
, the NRG may not conduct or sponsor. and a person is not required 10 respond to, the ilforrnation collection.
- 1. F~cility Name
- 2. Docket Number 3.Page Quad Cities Nuclear Power Station Unit 1 05000254 1
OF 4
4, Title Phase to Ground Fault in Isolated Phase Bus Duct Led to Generator Trip and an Automatic SCRAM
- 5. Event Date 6, LEA Number 7, Report Date
- 8. Other Facilities Involved I
Sequential I ""
Facility Name Docket Number Month D*y Year Year Number No, Month D*y Year n/a 05000 Facility Name Docket Number 08 25 2019 2019 - 002 00 10 24 2019 n/a 05000
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 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
D D
D 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii)
- 50. 73(a)(2)(ix)(A)
D 20.2203(a){2)(il D 50.36(c){1 )(i)(A)
[8] 50. 73(a)(2)(iv)(A)
D 50.73(a){2)(x)
- 10. 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 73.77(a)(1) 100 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 01her (Specify in Abstract below or in
D. SAFETY ANALYSIS
System Design
YEAR 2019
- SEQUENTIAL NUMBER 002 REV NO.
00 The IPBD system associated with the UAT utilizes bare aluminum conductors that transfer electrical energy from the Main Generator to the UAT. There is a single conductor fer each phase of the circuit and each conductor is housed in a grounded aluminum duct thareffectively isolates each phase from the other. The conductors are positioned in the center of each bus duct to maintain sufficient air gap between the conductor and the bus duct walls. Insulators mounted to the top of the bus duct are used to position and support the conductor. Each insulator consists of a porcelain material that provides very high resistance to current flow and maintains the electrical separation between the conductor and the bus duct. The bus ducts are designed to be protected from water intrusion to prevent condensation from forming on the insulators and degrading their insulative qualities.
Safety Impact The safety significance of this event was minimal. Reactor Water Level lowered following the automatic SCRAM and was recovered via the Feedwater system. No relief valves were actuated during the event as Reactor pressure was controlled by the Turbine Bypass valves. All post-SCRAM equipment functioned properly.
The automatic SCRAM resulted in an event notification in accordance with 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). (ENS 54239, 1551.hours (ET), 8/25/19)
Risk Insights The equipment responsible for monitoring and detecting the presence of a phase to ground fault on the Main Generator circuit performed exactly as intended and proactively tripped the Generator as designed. 'There were no inoperable systems or Technical Specification action statements in place at that time to complicate the event. The operators responded to the event by performing the required actions safely and in accordance with procedures and training.
This event is a Maintenance Rule Functional Failure (MRFF). This event is not a Safety System Functional Failure (SSFF).
E. CORRECTIVE ACTIONS
Immediate Corrective Actions:
- 1. The insulators affected by the water intrusion were replaced
- 2.
The degraded gaskets on the hinged covers for the "A" IPBD were replaced Follow-up Corrective Actions:
- 1.
Additional PM activities related to gaskets and inspections will be implemented on the IPBDs
F. PREVIOUS OCCURRENCES
SEQUENTIAL NUMBER 002 REV NO.
00 No similar events were identified where a degraded gasket in the IPBD or non-segregated bus duct system allowed moisture intrusion or contributed to a fault.
G. COMPONENT FAILURE DATA
Failed Equipment - "A" Isolated Phase Bus Duct Component Manufacturer - General Electric Component Model - Miniflux Component Type - Self-Cooled This event has been reported to ICES/IRIS. Page _4_ of _4_