05000220/LER-2019-003-01, Manual Reactor Scram Due to Pressure and-Power Oscillations
| ML19218A108 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 08/02/2019 |
| From: | Tierney T Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NMP1L3305 LER 2019-003-01 | |
| Download: ML19218A108 (7) | |
| 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 10 CFR 50.73(a)(2)(i) |
| 2202019003R01 - NRC Website | |
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'7 ftt:*:t:'::...,;:Jf:" Exelon Generation(ID NMP1L3305 August 2, 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 2019-003, Revision 1, Manual Reactor Scram Due to Pressure and Power Oscillations The original NMP1 LER 2019-003 was submitted June 28, 2019. Enclosed is NMP1 Licensee Event Report (LER) 2019-003, Revision 1, Manual Reactor Scram Due to Pressure and Power Oscillations. This revision is to provide additional details on the cause of the event and the corrective actions following completion of the root cause analysis.
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,
~,~-~,
Plant Manager, Nine Mile Point Nuclear Station Exelon Generation Company, LLC TAT/DJW
Enclosure:
NMP1 Licensee Event Report 2019-003 Revision 1, Manual Reactor Scram Due to Pressure and Power Oscillations.
cc:
NRG Regional Administrator, Region I NRG Resident Inspector NRG Project Manager
August2,2019 NMP1 LER 2019-003, Revision 1 Page 2 bee:
P. M. Orphanos T. A. Tierney J. Barstow B. K. Shultz S. Brannan Cole D. P. Ferraro H.Apa COMMITMENTS IDENTIFIED IN THIS CORRESPONDENCE None
Enclosure NMP1 Licensee Event 2019-003, Revision 1 Manual Reactor Scram Due to Pressure and Power Oscillations Nine Mile Point Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-63
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 0313112020 (04-2017)
, the htt1,1://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3D 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 4
- 4. TITLE Manual Reactor Scram due to Pressure and Power Oscillations
- 5. EVENT DATE
- 6. LER 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 N/A N/A FACILITY NAME DOCKET NUMBER 04 29 2019 2019 - 003
- - 01 06 28 2019 N/A N/A
- 9. OPERA TING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.2201(bl D 20.2203(aJ(3Hil D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2201 (dl D 20.2203(a)(3)(iil D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
N D 20.2203(aJ(1)
D 20.2203(a)(4)
D so.13(aJ(2J(iiil D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2J(il D 50.36(c)(1)(i)(A) 1:8] 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(al(4l D 20.2203(aJ(2J(iiil D so.3s(cJ(2J D 50.73(a)(2)(v)(B)
D 13.11(aJ(sJ D 20.2203(a)(2)(iv)
D so.4s(aJ(3J(iil D 50.73(a)(2)(v)(C)
D 13.77(aJ(1J 084 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73. n(aJ(2J(il D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(aJ(2)(ii)
.\\0 >. ::, :
D 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in
E. METHOD OF DISCOVERY
YEAR 2019
- 3. LER NUMBER SEQUENTIAL NUMBER 003 This event was discovered by Reactor Operators when the reactor pressure, level and power oscillations were observed in the control room.
F. SAFETY SYSTEM RESPONSES:
All safety systems responded per design.
II. CAUSE OF EVENT
The organization did not effectively incorporate appropriate learnings from previous NMP events and operating history that would have provided adequate flexibility in the operating strategy to mitigate the risks of increased oscillations. The Nine Mile Point U1 operational strategy did not provide flexibility or incorporate an exit strategy from the oscillation region.
III. ANALYSIS OF THE EVENT
The reactor scram and specified system activation is reportable under 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 non-optimal tuning resulted in EPR pressure control issues in the 80-90% power region during reactor startup that produced reactor pressure, level and power oscillations greater than those allowed without a backup pressure regulator available. A manual reactor scram was inserted per procedure.
All other plant systems performed per design. Plant parameters, other than the pressure, level and power oscillations, remained within normal values throughout the event. There was no loss of offsite power to the onsite emergency buses, the HPCI mode of feed and condensate system initiated as designed on the low reactor water level signal.
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:
REV NO.
01 2019 003 Replaced bean valve and flushed/cleaned MPR sensing line. Tuning of the Turbine Control systems was completed prior to return to service.
B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
N1-SOP-31.2, "Pressure Regulator Malfunctions" has been revised to allow margin for expected oscillations. SOPs that direct a unit to shutdown or derate will be reviewed and revised as needed to incorporate the lessons learned pertaining to providing appropriate operational flexibility.
V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
Tuning of the EPR was not optimal. There were no individual component failures.
B. PREVIOUS LERs ON SIMILAR EVENTS:
NMP1 LER 2017-002, submitted May 18, 2017, was due to pressure oscillations at 4%.
power. The cause of that event was a partial blockage within the MPR sensing line coupled with hysteresis found within the cylinder stroke of the Mechanical Hydraulic Control (MHC) Bypass Relay. The actions to prevent recurrence in 2017 included:
- 1. Implementation of a two-year preventive maintenance activity for routine flushing and filling of the pressure sensing bellows line and associated piping with contingencies to replace when required.
- 2. Revision of associated procedures to include steps to flush and backfill sensing lines.
- 3. Revised the Turbine Trip Test procedure.
These actions do not ensure the EPR is optimally tuned and 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 Reactor Pressure Vessel Feedwater Level Control System High Pressure Coolant Injection System Reactor Protection System Turbine Control System Electronic Pressure Regulator IEEE 803 FUNCTION IDENTIFIER RPV N/A N/A N/A N/A RG IEEE 805 SYSTEM IDENTIFICATION AD JB BJ JC JJ JJ REV NO.
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