05000410/LER-2020-001, Manual Scram Due to an Electro Hydraulic Control Fluid Leak on the Turbine Control System
| ML20132A108 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 05/04/2020 |
| From: | Tierney T Exelon Generation Co |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NMP2L273010 LER 2020-001-00 | |
| Download: ML20132A108 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(viii)(A) 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)(i) 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 4102020001R00 - NRC Website | |
text
(?
Jjl&t&-
Exelon Generation~.
NMP2L273010 May 4, 2020 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 Docket No. 50-41 o 10 CFR 50.73
Subject:
NMP2 Licensee Event Report 2020-001, Manual Scram due to an Electro-Hydraulic Control Fluid Leak on the Turbine Control System In accordance with the reporting requirements contained in 10 CFR 50.73(a)(2)(iv)(A), please find enclosed NMP2 Licensee Event Report 2020-001, Manual Scram due to an Electro-Hydraulic Control Fluid Leak on the Turbine Control System.
There are no regulatory commitments contained in this letter.
Should you have any questions regarding the information in this submittal, please contact Brandon Shultz, Site Regulatory Assurance Manager, at (315) 349-7012.
Respectfully,
~a-~¥'
Todd A. Tierney
(/
Plant Manager, Nine Mile Point Nuclear Station Exelon Generation Company, LLC TAT/DJW
Enclosure:
NMP2 Licensee Event Report 2020-001, Manual Scram due to an Electro-Hydraulic Control Fluid Leak on the Turbine Control System cc:
NRG Regional Administrator, Region I NRG Resident Inspector NRG Project Manager
Enclosure NMP2 Licensee Event Report 2020-001 Manual Scram due to an Electro-Hydraulic Control Fluid Leak on the Turbine Control System Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69
NRCFORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150*0104 EXPIRES: 03/31/2020 (04*2017)
Estimated burdsn per response lo 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 />.
lW.'
Reported lessons learned are incorporated into the licensing process and fed back to industry.
LICENSEE EVENT REPORT (LER)
Send comments regarding burden estimate lo the Information Seivices Branch (T-2 F43), U.S.
- ~
I Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to ln!ocollects.
~
~~
(See Page 2 for required number of digits/characters tor each block)
Resource@nrc.gov, and to the Desk Officer, Office ol Information and Regulatory Affairs, NEOB-10202, (3150*0104), Office of Management and Budget Washington, DC 20503. II a means (See NUREG-1022, R.3 for instruction and guidance for completing this form used to Impose an information collection does not display a currently valid 0MB control number, the htt12://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3l)
NRC may not conduct or sponsor, and a person is not required lo respond to, the Information collection.
- 3. PAGE Nine Mile Point Unit 2 05000410 1 OF 5
- 4. TITLE Manual Scram due to an Electro-Hydraulic Control Fluid Leak on the Turbine Control System
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I.SEQUENTIAL I REV FACIUlY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR N/A N/A FACILllY NAME';
DOCKET NUMBER 3
04 2020 2020 - 001
- - 00 05 04 2020 N/A NIA
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D ~0.2201 (b>
D 20.22oa(a)(3)(i>
D 50.73(a)(2)(il)(A)
D 50.73(a)(2)(viii)(A) 1 D 20.2201 (dl D 20.2203(a)(3l(i1>
D 50.73(a)(2)(11)(B)
D 50.73(a)(2)(vili)(B)
D 20.2203(a)(1>
D 20.2203(aJ(4>
D so.1a(a)(2Hm>
D 50. 73(a)(2)(ix)(A)
D 20.2203(aJ(2)(il D 50.36(c)(1 )(i)(A) 181 50.73(a)(2)(iv)(A) 0 50. 73(a)(2)(x) 1 O. POWER LEVEL D 20.22oa(a)(2)(11>
D 50.36(c)(1)(ii)(A)
D 50.73(a)(2)(v)(A)
D 1a.11(aJ(4>
D 20.22oa(aJ(2>(m>
D so.as(c)(2J D 50.73(a)(2)(v)(B)
D 1a.11 (a)(s>
D 20.2203(a)(2)(iv)
D so.4s(a)(3)(n>
D 50.73(a)(2)(v)(C)
D 1a.11(a)(1>
88 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 1a.11(a)(2J
D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D so.1a(aH2>(v11>
D 1a.11(a><2)(ii)
D 50.73(a)(2)(i)(C)
D OTHER Specify In Abstract below or in NRC Fonn 366A
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT rELEPHONE NUMBER (Include Ares Code}
Brandon Shultz, Site Regulatory Assurance Manager (315) 349-7012 CAUSE SYSTEM COMPONENT MANU*
REPORTABLE
CAUSE
SYSTEM COMPONENT MANU*
REPORTABLE FACTURER TOEPIX FACTURER TOEPIX D
TG ACC GE y
N/A N/A N/A N/A N/A 14, SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 181 NO SUBMISSION DATE ABSTRACT (Limit to 1400 spaces, I.e., approximately 15 sing/a-spaced typewritten lines)
On March 4, 2020 at 12:05, Nine Mile Point Unit 2 (NMP2) inserted a manual reactor scram due to lowering Electro-Hydraulic Control System (EHC) level in the turbine control system. An un-isolable leak occurred when a %-inch stainless steel tube failed on the EHC supply header. The plant responded as designed following the manual scram with all safety systems remaining in a normal standby lineup. This event is reportable under 1 o CFR 50.73(a)(2)(iv)(A) as any event or condition that resulted in a manual or automatic actuation of any of the systems listed in 10 CFR 50.73(a)(2)(iv)(B).
The cause of the event is inadequate procedure quality that prevented the performance of appropriate preventative maintenance resulting in cyclic fatigue failure of the EHC line. The corrective actions include improving the preventative maintenance procedure and system monitoring strategies.
NRC FORM 366 (04-2017)
NRC FORM 368A (04-2017))
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150*0104 EXPIRES: 03/31/2020 Esttmated burden 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 />. Reported lessons learned are incorporated into the licensing prat:ess and led back to induslry. Send commenls regarding burden estimate to the Information Services Branch (T*2 F43), U.S. Nuclear Regulalory Commission, Washington, DC 20555-0001, or by e-mail lo lnlocollecls.Resource@nrc.gov, and lo lhe Desk Officer, Office of lnlormalion and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used lo impose an information collection does not display a currently vatid 0MB contrcl number, lhe NRG may nol conduct or sponsor, and a person is not required to respond lo, the information collection.
J:.,...,...,o.,i.,,,
l-~.. J\\ LICENSEE EVENT REPORT (LER) a.~**lo'i,f~:
CONTINUATI0"1 SHEET
\\~~,., <..:: :/,t.,i' 111 (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-colleclions/nuregs/staff/sr1022/r3/}
Nine Mile Point Unit 2 05000410 VEAR
- 3. LER NUMBER SEQUENTIAL NUMBER REV NO.
2020 -
001 00
NARRATIVE
I.
DESCRIPTION OF EVENT
A. PRE-EVENT PLANT CONDITIONS:
Prior to the event, NMP2 was operating at 88% reactor power.
B. EVENT:
At 11 :34 on March 4, 2020, NMP2 received Control Room Annunciation, Turbine Controls EHC Storage Tank low-level alarm. Following receipt of the low-level alarm, investigation by Operations identified a significant EHC leak on Turbine Building elevation 277' in the area of the Turbine Stop and Control Valves. Based on field assessments, the Control Room staff determined that the continuing lowering trend in EHC reservoir level was unable to be mitigated and a manual reactor scram was inserted at 1205. The plant responded as designed following the manual scram with all safety systems remaining in a normal standby lineup and operators stabilized the plant in Mode 3. The EHC leak was then isolated and the station entered a forced outage.
Nine Mile Point Unit 1 was unaffected by the scram at NMP2.
Operations performed the ENS notification (#54562) required by 10 CFR 50.72(b)(2)(iv)(B) and 1 O CFR 50. 72(b )(3)(iv)(A) for the reactor scram.
This event has been entered into the plant's corrective action program as IR 4323670.
C. INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:
No other systems, structures, or components contributed to this event.
D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES AND OPERATOR ACTIONS:
The dates, times, and major occurrences and operator actions for this event are as follows.
March 4, 2020 1134: Annunciator received for Low Turbine Generator Hydraulic Fluid Storage Tank Level. A lowering trend for the EHC reservoir level was observed on a local level gauge via cameras in the Control Room.
1138: A fire alarm was received for southeast Turbine Building 277. Fire Brigade Leader was dispatched and reported at 1142 a large leak and aerosol spray of EHC in this area. Fire Brigade Leader (FBL) reported no presence of fire or smoke.
1157: SOP for rapid power reduction was enter and commenced reducing reactor power to 85% to lower rate of EHC leakage.
1205: EHC tank level as read on local gauge continued to lower rapidly, with maximum make up to the reservoir. SOP for reactor SCRAM, was entered. Reactor mode switch placed in shutdown. EOP for RPV control entered on low reactor water level which occurred due to the reactor SCRAM. EHC fluid leak identified as a ~-
inch stainless steel tube upstream of manual isolation valve 2TMB-V157D, supply line to Main Stop Valve 1 D.
1207: Turbine is tripped which slowed the EHC leak significantly. EHC reservoir level then recovered through system make up.
1225: Unit 2 Turbine Building is evacuated due to the EHC leak, no EAL (HAS) threshold was met.
1350: With plant parameters stable, reactor SCRAM and EOP for RPV Control are exited and plant shutdown is continued.
1358: Operations and maintenance closed the system isolation valves to stop the leak.
E. METHOD OF DISCOVERY
This event was discovered by Reactor Operators when the Control Room Annunciation for Low Turbine Generator Hydraulic Fluid Storage Tank Level was received.
F. SAFETY SYSTEM RESPONSES:
All safety systems responded per design.
II. CAUSE OF EVENT
The cause of the event is inadequate procedure quality that prevented the performance of appropriate preventative maintenance resulting in cyclic fatigue failure of the EHC line. The Main Turbine Electro-Hydraulic Control Accumulator Preventive Maintenance was inadequate in the identification of degraded Turbine Control Valve (TCV) accumulator performance in 2016 and 2018, resulting in missed opportunities to replace or rebuild the degraded accumulators' bladders. This led to their eventual failure which caused increased EHC system pressure pulsations and excessive vibrations, resulting in the cyclic fatigue failure of the W' EHC supply line.
III. ANALYSIS OF THE EVENT
This event is reportable under 1 O CFR 50. 73(a)(2)(iv)(A) as any event or condition that resulted in a manual or automatic actuation of any of the systems listed in 1 O CFR 50.73{a)(2)(iv)(B).
The direct cause of the SCRAM was an un-isolable leak due to a failed ~-inch stainless steel tube on the EHC supply header. Based on Control Room annunciation, local indication and field assessments, the Control Room took appropriate action and inserted a manual scram.
Following placement of the mode switch to shutdown and subsequent scram, the EHC system remained in service. Main Steam Isolation Valves remained open and the Control Room staff was able to use bypass valves for normal pressure control. The plant was stabilized with all plant systems performing per design.
Based on the above discussion, it is concluded that the safety significance of this event is low and the event did not pose a threat to the health and safety of the public or plant personnel.
This event does affect the NRC Regulatory Oversight Process Indicator for unplanned scrams per 7000 hours0.081 days <br />1.944 hours <br />0.0116 weeks <br />0.00266 months <br /> of critical operation.
IV. CORRECTIVE ACTIONS
A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:
The failed EHC line and Turbine Control Valve Accumulators were replaced.
B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
Revise the Main Turbine Electro-Hydraulic Control Accumulator preventive maintenance procedure to properly detect and repair degraded accumulator performance.
V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
The EHC system Turbine Control Valve accumulators failed due to inadequate procedure quality that prevented the performance of appropriate preventative maintenance.
B. PREVIOUS LERs ON SIMILAR EVENTS:
None.
NAC YEAR 2020
- SEQUENTIAL NUMBER 001 C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:
COMPONENT Turbine Control Valve EHC Accumulators Main Turbine EHC System IEEE 803 FUNCTION IDENTIFIER ACC N/A IEEE 805 SYSTEM IDENTIFICATION TG TG REV NO.
00 Page _5_ of _5_