05000220/LER-2011-001, For Nine Mile Point, Unit 1 Turbine Trip Due to Oil Pressure Fluctuations to the Turbine Master Trip Solenoid
| ML11193A067 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 06/30/2011 |
| From: | Lynch T Constellation Energy Group, EDF Group, Nine Mile Point |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 11-001-00 | |
| Download: ML11193A067 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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)(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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 2202011001R00 - NRC Website | |
text
Thomas A. Lynch Plant General Manager CENG.
a joint venture of 0
Constellation
- FneM, eDF NINE MILE POINT NUCLEAR STATION P.O. Box 63 Lycoming, New York 13093 315.349.5205 315.349.1321 Fax June 30, 2011 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION:
SUBJECT:
Document Control Desk Nine Mile Point Nuclear Station Unit No. 1; Docket No. 50-220 Licensee Event Report 2011-001, Turbine Trip Due to Oil Pressure Fluctuations to the Turbine Master Trip Solenoid In accordance with 10 CFR 50.73(a)(2)(iv)(A), please find attached Licensee Event Report 2011-001, Turbine Trip Due to Oil Pressure Fluctuations to the Turbine Master Trip Solenoid.
There are no regulatory commitments in this submittal.
Should you have questions regarding the information in this submittal, please contact John J. Dosa, Director Licensing, at (315) 349-5219.
Very truly yours, TAL/RJC
Attachment:
Licensee Event Report 2011-001, Turbine Trip Due to Oil Pressure Fluctuations to the Turbine Master Trip Solenoid cc:
NRC Project Manager NRC Resident Inspector NRC Regional Administrator
ATTACHMENT LICENSEE EVENT REPORT 2011-001 TURBINE TRIP DUE TO OIL PRESSURE FLUCTUATIONS TO THE TURBINE MASTER TRIP SOLENOID Nine Mile Point Nuclear Station, LLC June 30, 2011
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the 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 6
- 4. TITLE Turbine Trip Due to Oil Pressure Fluctuations to the Turbine Master Trip Solenoid
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR None NA NUMBER NO.NoeA FACILITY NAME DOCKET NUMBER 05 02 2011 2011 001 00 1 06 30 2011 1 None NA
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
El 20.2201(b)
E] 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
E] 50.73(a)(2)(vii)
NA El 20.2201(d)
[I 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
[I 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
- 10. POWER LEVEL E] 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
[I 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
El 20.2203(a)(2)(ii)
[I 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
[I 50.36(c)(2)
[I 50.73(a)(2)(v)(A)
El 73.71(a)(4) 47%
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in
D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES
April 26, 2011:
0337 Thermal power was reduced at NMP1 to approximately 43 percent due to elevated vibrations on the turbine shaft driven feedwater pump gear box and generator.
April 26 through May 2, 2011:
Investigations continued to determine the cause of the vibrations on the turbine shaft driven feedwater pump gear box and generator.
May 2, 2011:
1805 NMP 1 was operating at approximately 45 percent power due to shaft driven feedwater pump gearbox maintenance.
2051 The reactor scrammed from 47 percent power on an automatic initiation of the RPS logic.
The HPCI system automatically initiated on a turbine trip signal.
2052 RPV level was restored to above the HPCI system low level actuation setpoint and the HPCI system initiation signal was reset.
May 3, 2011:
0310 NMP1 was in cold shutdown.
May 19, 2011:
Repairs to the NMP 1 turbine generator were completed and the unit was restored to 100 percent power.
E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
The HPCI system was initiated on a turbine trip signal. The HPCI system is an operating mode of the feedwater system. The HPCI system is not an ECCS.
F. METHOD OF DISCOVERY
This event was discovered by the operators when the reactor automatically scrammed.
G. MAJOR OPERATOR ACTION:
Upon discovery of the reactor scram, the operators verified all rods were fully inserted. No other actions were required to support shutting down the reactor.
NRC FORM 366 (10-2010)
H. SAFETY SYSTEM RESPONSES:
All safety systems responded per design. There was no loss of offsite power to the onsite emergency buses, the HPCI system initiated as designed, and the ECCS systems were available but not called upon to support the safe shutdown of the reactor.
II. CAUSE OF THE EVENT
The cause of the event falls under NUREG-1022 cause code A (personnel error). Inadequate implementation of management job performance standards resulted in the development and implementation of work performance documents which lacked sufficient detail associated with turbine maintenance activities. An over-reliance on the original equipment manufacturer to prescribe the routine maintenance activities, as well as the level of detail within the work documents and the use of skill-of-the-trade activities for supplemental personnel, resulted in degraded equipment conditions and poor maintenance practices.
In the spring 2011, the NMP 1 turbine exciter was disassembled and reinstalled by the manufacturer. In the course of reinstallation, a Falk insulating coupling between the exciter and generator was installed with a locking tab in contact with the generator shaft. With the locking tab in contact with the generator shaft the insulating properties of the coupling were bypassed. This short caused circulating currents resulting in changes to the shaft driven oil pump gears which caused oil pressure fluctuations to occur. Also during reinstallation, the fittings on the MTS supply lines were damaged which resulted in oil leaks around these fittings. These leaks contributed to the oil pressure fluctuations. Contributing to these errors was a pre-existing condition of control linkage binding on the secondary speed relay. This linkage had been visually inspected, but due to lack of specific inspection criteria, the binding was not noted. The combination of the leaking fittings on the MTS oil supply, the binding of the secondary speed relay linkage, and main shaft oil pump discharge pressure fluctuations caused the oil pressure to the MTS to fluctuate enough to cause it to actuate and trip the turbine. The turbine tripped on MTS actuation leading to an automatic RPS reactor scram. The cause of the MTS actuation was oil pressure fluctuations to the MTS.
This event was entered into the Nine Mile Point corrective action program (Condition Report 2011-004459).
III. ANALYSIS OF THE EVENT
This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph 10 CFR 50.73(a)(2)(iv)(B). Both the RPS and HPCI system (an operating mode of the feedwater system) were actuated during this event. Both systems are listed in 10 CFR 50.73(a)(2)(iv)(B).
At NMP 1, the HPCI system is an operating mode of the feedwater system. The HPCI system functions as a feedwater coolant injection system and is not an ECCS. Plant systems performed per design. Plant parameters, other than reactor water level, remained within normal values throughout the event. There was no loss of offsite power to the emergency buses, HPCI initiated as designed, and the ECCS systems were available, but not called upon to support the safe shutdown of the reactor. Had this event occurred at higher power, with or without the turbine shaft driven feedwater pump, the results would have been the same. The reactor would still have scrammed with reactor pressure vessel water level shrinkage and HPCI initiation.
NRC FORM 366 (10-2010)
It is therefore concluded that had a design basis accident occurred coincident with this event, even at higher power, plant systems would have responded per design to mitigate the accident. Based on the above considerations, the safety significance of this event is very low, and the event did not pose a threat to the health and safety of the public or plant personnel. This event affects the NRC regulatory oversight process (ROP) index for unplanned scrams. Due to this scram, the unplanned scram index value will be 1.83 compared to the green-to-white threshold value of greater than three. This reduction will not result in entry into the "increased regulatory (white) response band."
IV. CORRECTIVE ACTIONS
A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:
- 2. The tubing and damaged fittings associated with the master trip solenoid supply lines were repaired.
- 3. The secondary speed relay linkage was adjusted so it does not bind.
- 4. The shaft driven oil pump gears were repaired.
- 5. The repairs to the NMP 1 turbine were completed and the unit was restored to 100 percent power.
B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
- 1. Additional Nine Mile Point Nuclear Station oversight and supervision was present to oversee the repairs.
- 2. Procedures will be developed to detail the disassembly, inspection, reassembly and testing of the NMP1 turbine, generator, exciter and control components.
V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
The following components failed:
- 2. The shaft driven oil pump gears were damaged due to the circulating current.
- 3. The secondary speed sensing linkage was binding.
- 4. The tubing/fittings on the supply lines to the MTS were damaged and leaking oil.
B.
PREVIOUS LERS ON SIMILAR EVENTS:
There are no previous LERs related to pressure fluctuations on the MTS or binding on the secondary speed sensing relay.
NRC FORM 366 (10-2010)
C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:
COMPONENT IEEE 803 COMPONENT IDENTIFIER IEEE 805 SYSTEM IDENTIFICATION PART NUMBER HPCI Pump Master Trip Solenoid Turbine Bypass Valves Feedwater Pump Main Generator System Reactor Protection System D. SPECIAL COMMENTS:
None P
SOL V
P TG NA BJ TA JI SJ TB JC 180 X 274 NRC FORM 366 (10-2010)