05000318/LER-2016-001, Regarding Automatic Reactor Trip Due to Main Turbine Electro-Hydraulic Control Fluid Leak
| ML17026A372 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  (DPR-069) |
| Issue date: | 01/24/2017 |
| From: | Flaherty M Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 16-001-00 | |
| Download: ML17026A372 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(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)(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 |
| 3182016001R00 - NRC Website | |
text
Exelon Generation.~
January 24, 2017 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Calvert Cliffs Nuclear Power Plant, Unit No. 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318 Licensee Event Report 2016-001, Revision 00 Mark Flaherty Plant Manager Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657 410 495 5205 Office 443-534-5475 Mobile www.exeloncorp.com mark.flaherty@,exeloncorp.com 10 CFR 50.73 Automatic Reactor Trip Due to Main Turbine Electro-Hydraulic Control Fluid Leak The attached report is being sent to you as required by 1 O CFR 50.73.
There are no regulatory commitments contained in this correspondence.
Should you have questions regarding this report, please contact Mr. Larry D. Smith at (410) 495-5219.
Respectfully,
~~J:)~
Mark D. Flaherty Plant Manager MDF/KLG/bjm
Attachment:
As stated cc:
NRC Project Manager, Calvert Cliffs NRC Regional Administrator, Region I NRC Resident Inspector, Calvert Cliffs S. Gray, MD-DNR
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- 3. PAGE Calvert Cliffs Nuclear Power Plant, Unit 2 05000 318 1 OF 4
- 4. TITLE Automatic Reactor Trip Due to Main Turbine Electro-Hydraulic Control Fluid Leak
- 5. EVENT DATE
- 6. LEA NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 12 03 2016 2016 - 001 00 01 24 2017 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITIED 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) 1 D 20.2201 (d)
D 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D so.73(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)
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 so.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71 (a)(5)
D 20.2203(a)(2)(iv)
D so.4a(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1) 100 D 20.2203(a)(2)(v) 0 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 so.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in 2231 - Operations completed verification that EOP-0 Safety Functions were met.
2236 - Operations implemented EOP-1 for an uncomplicated trip.
2325 - Operations exited EOP-1 and implemented Operating Procedure-4, Plant Shutdown from Power Operation to Hot Standby.
December 5, 2016 0225 - Unit 2 entered Mode 1.
1647 - Unit 2 returned to full power.
E.
FAILURE MODES:
As part of the investigation into this unit trip, 2CVMT-210P Emergency Trip Fluid Check Valve and two other non-failed, similar check valves were sent off site for analysis. Forensic analysis at the lab indicated the cause of the fracture, which incurred on the threaded portion of the check valve, was due to IGSCC. This fracture resulted in a large leak of EHC fluid which rapidly reduced EHC header pressure causing all the Unit Main Turbine Governor and Intercept Valves to rapidly shut. Based on the fracture characteristics observed in the lab, the most likely cause of the IGSCC in this aluminum-bronze alloy check valve is exposure to ammonia. While it is most likely that some source of ammonia was introduced to the threads of the check valve during some previous maintenance activity, the analysis is not able to determine the source or the length of time the 2CVMT-210P Emergency Trip Fluid Check Valve had been exposed to ammonia. The non-failed check valves did not have any signs of similar corrosion issues.
F.
METHOD OF DISCOVERY
The method of discovery was self-revealing upon the failure of 2CVMT-210P Emergency Trip Fluid Check Valve while it was in operation. This event is documented in the site's Corrective Action Program under IR03949100.
II. CAUSE OF EVENT
There were no human performance issues related to the reactor trip or the recovery following the unit shutdown.
A.
SAFETY CONSEQUENCES
The leak on 2CVMT-210P Emergency Trip Fluid Check Valve resulted in a rapid decrease in EHC header pressure which resulted in a Main Turbine load reject when the Main Turbine Governor and Intercept Valves went shut. This resulted in an automatic RPS actuation due to loss of load following the main turbine trip. The loss of load trip from 100 percent power is an analyzed anticipated operational occurrence event. All core damage mitigating systems and normal heat removal systems remained available after the trip. As a result the safety consequence from this trip involved minimal nuclear risk.
This event satisfies the criteria in NUREG-1022, Revision 3 for RPS actuation. Therefore this event is reportable pursuant to 1 O CFR 50.73(a)(2)(iv)(A). An immediate event notification report (52406) was also made pursuant to 1 O CFR 50.72(b)(2)(iv)(B).
B.
CORRECTIVE ACTIONS
REV NO.
2CVMT-210P Emergency Trip Fluid Check Valve was replaced and the EHC system was tested prior to returning the EHC system to service. All similar type valves in the U-2 EHC system (82 in all) will be replaced during Unit 2's 2017 refueling outage which starts in February 2017. Extent of condition is limited to U-2 Main Turbine system as Unit 1 Main Turbine is from a different manufacturer and does not have similar type valves. In addition Calvert Cliffs will establish an overhaul preventive maintenance strategy for each of U-2 Main Turbine Governor and Intercept Valve Actuators to include replacement of the actuators' associated aluminum-bronze alloy components. As part of the extent of condition review, components that contain aluminum bronze material and that are operational critical components being overhauled by vendors, will have written contract limitations specifically disallowing the use of ammonia for any part of the contracted maintenance.
A supplemental licensee event report will be submitted if additional information is subsequently developed that would significantly change the corrective actions for this event.
111. PREVIOUS SIMILAR EVENTS:
At Calvert Cliffs, in the last five years, there have been no similar events involving a reactor trip caused by loss of EHC header pressure.
A.
COMPONENT INFORMATION:
COMPONENT Main Turbine 21 Main Turbine Governor Valve Actuator (2CVMT-210P) 2CVMT-21 OP Emergency Trip Fluid Check Valve IEEE 803 FUNCTION ID TRB VOP CKV IEEE 805 SYSTEM ID TA TA TG 2CVMT-210P Emergency Trip Fluid Check Valve was manufactured by Admiral Valve LLC. Page 4 of 4