05000220/LER-1917-003, Regarding Automatic Reactor Scram Due to Reactor Vessel Low Water Level
| ML17325A994 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 11/02/2017 |
| From: | Kreider R Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NMP1 L3184 LER 17-003-00 | |
| Download: ML17325A994 (7) | |
| 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)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 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)(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) |
| 2201917003R00 - NRC Website | |
text
- -
Exelon Generation NMP1 L3184 November 2, 2017 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. NPF-63 Docket No. 50-220 10 CFR 50.73
Subject:
NMP1 Licensee Event Report 2017-003, Automatic Reactor Scram due to Low Reactor Water Level
. In accordance with the reporting requirements contained in 1 O CFR 50.73(a)(2)(iv)(A), please find enclosed NMP1 Licensee Event Report (LER) 2017-003, Automatic Reactor Scram due to Low Reactor Water Level.
There are no regulatory commitments contained in this letter.
Should you have any questions regarding the information in this submittal, please contact Dennis M. Moore, Site Regulatory Assurance Manager, at (315) 349-5219.
Respectfully,
~&.
Robert E. Kreider Jr.
Plant Manager, Nine Mile Point Nuclear Station Exelon Generation Company, LLC REK/RSP
Enclosure:
NMP1 Licensee Event Report 2017-003, Automatic Reactor Scram due to Low Reactor Water Level cc:
NRC Regional Administrator, Region I NRC Resident Inspector NRC Project Manager
Enclosure NMP2 Licensee Event Report 2017-001, Automatic Reactor Scram due to High Reactor Pressure Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69
'NRG FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPl'WVED BY 0MB: NO. 3150-0104 EXPIRES: 0313112020 (04-2017)
, the http://www. n re. gov/read ing-rm/d oc-collections/n u regs/staff/s r1 022/r3/)
- NRG 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 Automatic Reactor Scram due to Reactor Vessel Low Water Level
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YE.AR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR N/A NIA 2017 FACILITY NAME DOCKET NUMBER 09 06 2017
- - 003 00 11 2
2017 N/A N/A
- 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)
RUN D
D 20.2203(a)(1)
D 20.2203(a)(4) 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)
~ 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(aJ(2J(iiil 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 OTHER Specify in Abstract below or in 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.
September 6, 2017 1156:57 1157 1157 1157:15 1157:21 1157:34 1157:34 1157:34 1157:35 1157:35 1157:35 1158 1158:45 1203:31 1204:14 1217
- - 13 Feedwater Flow Control Valve rapidly closes
- - Annunciator F2-3-3, REACT VESSEL LEVEL HI-LO received for low RPV level
- - Lo-Lo Vessel Level reached, vessel and containment isolation signals received
- - All Reactor Recirculation Pumps trip
- - Reactor Water Cleanup isolates
- - Core Spray auto start signal
- - All MSIVs shut
- - Lo-Lo isolation signal clear
- - Reactor Operator executes N1-SOP-1 level control actions, secures both Feedwater Pumps due to high RPV level
- - 11 Emergency Condenser placed into service for RPV pressure control
- - MSIVs reopened, Main Condenser re-established for RPV pressure control
- - 11 Emergency Condenser removed from service
- - Core Spray is secured
E. METHOD OF DISCOVERY
This event was discovered by Reactor Operators when the 13 Feedwater Flow Control Valve began to rapidly close and Reactor Vessel Level Hi-LO Alarm was received for low RPV level.
F. SAFETY SYSTEM RESPONSES:
All safety systems responded per design.
REV NO.
QO
II. CAUSE OF EVENT
YEAR 2017
- 3. LER NUMBER SEQUENTIAL NUMBER
- 003 The cause of the scram was due to a failed power supply within the Proportional Amplifier, PAM-ID23E.
This power supply failure was determined to be due to a Schottky diode internal to the power supply of the Proportional Amplifier which resulted in the output from the module dropping out causing the #13 Feedwater Pump Flow Control Valve to close.
III. ANALYSIS OF THE EVENT
The automatic reactor scram is reportable under 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.73(a)(2)(iv)(A). It is defined under paragraph 10 CFR 50.73(a)(2)(iv)(A) as any event or condition that resulted in manual or automatic action of any of the specified systems listed in 10 CFR
- 50. 73(a)(2)(iv)(B).
The equipment failure associated with this event is a power supply within the Proportional Amplifier, PAM-ID23E. This power supply failure was determined to be due to a Schottky diode internal to the power supply of the Proportional Amplifier which resulted in the output from the module dropping out causing the #13 Feedwater Pump Flow Control Valve to drive closed. All other plant systems performed per design. Plant parameters, other than the RPV water level, remained within normal values throughout the event. There was no loss of offsite power to the onsite emergency buses, both trains of The HPCI mode of feed and condensate system initiated as designed, and the core spray initiation signal was received but injection was not required.
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.
After review and following the guidance contained within NEI 99-02 it was determined that this event did not require additional operator actions beyond that of a "normal" scram. The scram did not involve the unavailability of or inability to recover main feedwater nor did it involve the lifting of electromagnetic relief valves for pressure control. This event did not present additional challenges to plant operations staff and does not meet the criteria required to be classified as a complicated scram.
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:
Replaced failed Feedwater Level Control module PAM-ID23E.
REV NO.
00 B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
To prevent recurrence, a corrective design change is scheduled for 2019 which will implement and utilize fault tolerant digital controllers for the feedwater flow control valves.
V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
The root cause was a failed power supply within the Proportional Amplifier, PAM-ID23E. This power supply failure was determined to be due to a Schottky diode internal to the power supply of the Proportional Amplifier which resulted in the output from the module dropping out causing the #13 Feedwater Pump Flow Control Valve to drive closed. This failure was premature as the power
- supply was new as of March 2017.
- 8. PREVIOUS LERs ON SIMILAR EVENTS:
LER 2012-005 - In 2012 a scram occurred due to a pair of failed transistors internal to the flow error proportional amplifier. The cause of this failure was in a new power supply and the actions from 2012 would not have prevented this event C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:
COMPONENT Main Steam Isolation Valve Proportional Amplifier Reactor Pressure Vessel Feedwater Level Control System High Pressure Coolant Injection System Feedwater System Reactor Water Clean Up System Reactor Protection System Containment Isolation System Emergency Condenser System Core spray system D. SPECIAL COMMENTS:
None IEEE 803 FUNCTION IDENTIFIER ISV AMP RPV NIA N/A N/A N/A N/A N/A N/A N/A IEEE 805 SYSTEM IDENTIFICATION SB JB AD JB BJ SJ CE SC JM BL BG REV NO.
00 Page _5_ of _5_