05000220/LER-2019-004, Average Power Range Monitors Declared Inoperable
| ML19281A860 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 10/03/2019 |
| From: | Tierney T Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NMP1L3310 LER 2019-004-00 | |
| Download: ML19281A860 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 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)(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) |
| 2202019004R00 - NRC Website | |
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NMP1L3310 October 3, 2019 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Nine Mile. Point Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-63 Docket No. 50-220 10 CFR 50.73
Subject:
NMP1 Licensee Event Report 2019-004, Average Power Range Monitors Declared Inoperable In accordance with the reporting requirements contained in 1 O CFR 50.73(a)(2)(v)(A), please find enclosed NMP1 Licensee Event Report (LEA) 2019-004, Average Power Range Monitors Declared Inoperable.
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/RD
Enclosure:
NMP1 Licensee Event Report 2019-004, Average Power Range Monitors Declared Inoperable cc:
NRC Regional Administrator, Region I NRC Resident Inspector NRC Project Manager
Enclosure NMP1 Licensee Event 2019-004 Average Power Range Monitors Declared Inoperable Nine Mile Point Nuclear Station, Unit ~
Renewed Facility Operating License No. DPR-63
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017)
, the htt1;1://www.nrc.govlreading-rmldoc-col1ections/nuregslstafflsr1022/r3!)
NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Nine Mile Point Unit 1 05000220 1 OF 5
- 4. TITLE Average Power Range Monitors Declared Inoperable
- 5. EVENT DATE
- 6. LEA NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR NIA NIA FACILITY NAME DOCKET NUMBER 08 04 2019 2019 - 004
- - 00 10 03 2019 NIA NIA
- 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)(3J(il D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
N D 20.2201 (dl D 20.2203(aJ(3J(iil D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(aJ(1J D 20.2203(aJ(4l D so.13(aJ(2J(iiil D 50.73(a)(2)(ix)(A)
D 20.2203(aJ(2Jol D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. POWER LEVEL D 20.2203(aJ(2J(iil D 50.36(c)(1)(ii)(A)
~ 50.73(a)(2)(v)(A)
D 73.11(aJ(4l D 20.2203(aJ(2J(iiil D so.36(cJ(2J D 50.73(a)(2)(v)(B)
D 73.11 (a)(sJ D 20.2203(a)(2)(iv)
D so.46(aJ(3J(iil D 50.73(a)(2)(v)(C)
D 73.77(a)(1l 100 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(aJ(2Jol D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(aJ(2J(iiJ D 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in 17:45 - Received annunciator F2-2-1 for "React Recirc M-G Set 11" indicating it had tripped.
17:46 - Entered N1-SOP-1.3, "Recirc Pump Trip at Power was entered 17:46 -APRMs declared inoperable and Technical Specification 3.6.2a was entered.
18:07 - RRP 11 discharge valve is closed per N1-SOP-1.3, APRMs declared operable and Technical Specification 3.6.2a was exited.
E. METHOD OF DISCOVERY
This event was discovered by Reactor Operators when the control room alarm was received for "React Recirc M-G Set 11 ".
F. SAFETY SYSTEM RESPONSES:
No operational conditions requiring the response of safety systems occurred as a result of this condition.
II. CAUSE OF EVENT
The cause of the RRMG trip was determined to be an intermittent poor electrical connection within the tachometer generator. The most likely location would be between one of the brushes and the commutator.
III. ANALYSIS OF THE EVENT
This event is reportable under 10 CFR 50.72(b)(3){v)(A) and 1 O CFR 50.73(a)(2)(v)(A) as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: (A) Shut down the reactor and maintain it in a safe shutdown condition.
There were no actual nuclear safety consequences associated with the event. Although the flow-biased portion of the high neutron flux trips was not conservative, the trip function remained available. A portion of the flow-biased trip function curve is clamped at a maximum value of 122% of rated thermal power. This portion of the setpoint curve was not impacted by the non-conservative flow signal and remained available to provide the scram trip function as designed.
An assessment of the potential impact on the safety limit minimum critical power ratio (SLMCPR) was performed. This assessment included a review of thermal hydraulic stability and transients. NMP1 is analyzed for thermal-hydraulic instability using the Boiling Water Reactor Owners' Group Option II. The Option II analysis is performed to demonstrate the SLMCPR protection for postulated instability events by the APRM flow-biased flux scram setpoints. Should oscillations occur, they will be automatically detected and suppressed by YEAR 2019
- 3. LER NUMBER SEQUENTIAL NUMBER 004 the flow-biased APRM neutron flux scram. This analysis credits the flow-biased flux scram.
As such, when APRMs are declared inoperable, operators are required to use procedures in conjunction with the Exclusion _and Restrlcted regions on the power to flow map, to protect the SLMCPR. At rated conditions during the APRM inoperable scenario, instability is not a concern barring additional reactor recirculation flow reduction and entrance into the Restricted region.
For transient review, the Recirculation Pump Trip and Stall Malfunctions are inherent power decay situations in which the core thermal transients remain within permissible limits.
Transient results from tripping various combinations of recirculation pumps do not result in a scram or trip. With respect to cycle specific transient analyses performed for Anticipated Operational Occurrences (AOOs), these events terminate on a direct scram (Turbine Stop Valve Closure, Generator Load Reject, MSIV closure) and are therefore, unaffected by APRM reading. As such, if one of these events were to occur after a ARP trip and before the APRMs could be declared operable again, the SLMCPR would still be protected.
The direct cause of the APRMs being declared inoperable was the trip associated with the ARP 11. Operators were able to stabilize plant conditions quickly by properly executing the respective operating procedures and remaining in compliance with TS requirements.
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 safety system function failures.
IV. CORRECTIVE ACTIONS
A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:
Replacement of the tachometer generator was completed. The ARP 11 was placed back into service.
B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
Corrective actions to prevent recurrence are to revise the preventative maintenance strategy to replace the tachometer generator every two years.
REV NO.
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V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
The tachometer generator failed due to an intermittent poor electrical connection between one of the brushes and the commutator. There were no individual component failures.
B. PREVIOUS LERs ON SIMILAR EVENTS:
LEA 2014-001 was submitted acknowledging the failure to report two separate occasions in 2011 and 2012 in which ARP trips led to the inoperability of APRMs. The actions taken as a result of LEA 2014-001 regarding the missed reportability, led to the correct determination in this report.
C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:
COMPONENT Average Power Range Monitor {APRM)
Reactor Recirculation Pumps IEEE 803 FUNCTION IDENTIFIER JIC p
IEEE 805 SYSTEM IDENTIFICATION JC AD REV NO.
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