05000341/LER-2012-003, Regarding Reactor Scram Due to Degrading Condenser Vacuum
| ML12240A026 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 08/24/2012 |
| From: | Plona J DTE Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NRC-12-0055 LER 12-003-00 | |
| Download: ML12240A026 (4) | |
| 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)(1) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3412012003R00 - NRC Website | |
text
Joseph H. Plona Site Vice President 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734,586,5910 Fax: 734.586.4172 DTE Energy 10 CFR 50.73 August 24, 2012 NRC-12-0055 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington D C 20555-0001
Reference:
Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43
Subject:
Licensee Event Report (LER) No. 2012-003 Pursuant to 10 CFR 50.73(a)(2)(iv)(A), Detroit Edison is submitting the enclosed LER No. 2012-003, Reactor Scram Due to Degrading Condenser Vacuum.
No commitments are being made in this LER.
Should you have any questions or require additional information, please contact Mr. Rodney W. Johnson of my staff at (734) 586-5076.
Sincerely, Enclosure cc: NRC Project Manager NRC Resident Office Reactor Projects Chief, Branch 4, Region III Regional Administrator, Region III Supervisor, Electric Operators, Michigan Public Service Commission
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: No. 3150-0104 Expires 10/31/2013 (10-2010)
Estimated
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the Information collection.
- 3. PAGE Fermi 2 05000341 1 OF 3
- 4. TITLE Reactor Scram Due to Degrading Condenser Vacuum
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEUNIA E
FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR 05000 NUMBER NO.
____05000 06 25 2012 2012 003 00 08 24 2012 FACILITY NAME DOCKET NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT SUBMITTED PURSU ANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
E 20.2201(b)
Q 20.2203(a)(3)(i)
Q 50.73(a)(2)(i)(C) 50.73(a)(2)(vii)
J 20.2201(d)
Q 20.2203(a)(3)(ii)
J 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A)
I 20.2203(a)(1)
Q 20.2203(a)(4)
E 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B)
Q 20.2203(a)(2)(i)
Q 50.36(c)(1)(i)(A) l 50.73(a)(2)(iii)
E 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 20.2203(a)(2)(ii) i 50.36(c)(1)(ii)(A)
J 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
E 20.2203(a)(2)(iii)
Q 50.36(c)(2)
E 50.73(a)(2)(v)(A) l 73.71(a)(4) 26 Percent 20.2203(a)(2)(iv) 50.46(a)(3)(ii)
Q 50.73(a)(2)(v)(B) 0 73.71(a)(5)
E 20.2203(a)(2)(v) 0 50.73(a)(2)(1)(A) 0 50.73(a)(2)(v)(C)
Q OTHER 20.2203(a)(2)(vi)
J 50.73(a)(2)(i)(B)
Q 50.73(a)(2)(v)(D)
Specify in abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THS LER FACILITY NAME rELEPHONE NUMBER (Include Area Code)
Fermi 2 / Robert J. Salmon - Supervisor, Nuclear Compliance (734) 586 - 4273CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX E
SJ TRB D055 Y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION E YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
X NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On 6/25/2012 after completing repairs to the main unit transformer, reactor power was raised to approximately 22%
and the unit was synchronized to the power grid at 1203 EDT. At 1234 EDT Operations began a power increase.
At 1322 to 1325 EDT multiple vibration related alarms were received for the south reactor feed pump, and the pump tripped at 1325 EDT. Manual operation of the north reactor feed pump was used initially to recover reactor level. At 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> a manual scram was performed by placing the reactor mode switch in shutdown in response to degrading condenser vacuum. All rods fully inserted and operators used the standby feedwater system to restore water level. Reactor water level reduced to below Level 3 as a result of the scram, and all isolations and actuations associated with that level occurred as expected. The south reactor feed pump turbine was damaged which resulted in main condenser vacuum leaks that were isolated following the event. Decay heat was removed using the main condenser via the turbine bypass valves.
NRC FORM 366 (10-2010)
Initial Plant Conditions
Mode 1
Reactor Power 26 percent Description of the Event On 6/24/2012 reactor power was reduced to about 20% and the Main Turbine Generator (MTG) [TA/TB] was taken off line to repair Main Unit Transformer 2B [EL]. On 6/25/2012, after completing repairs to the main unit transformer, reactor power was raised to approximately 22% and the unit was synchronized to the power grid [FK] at 1203 EDT. A power ascension began at 1234 EDT using a combination of recirculation flow and control rod pulls to increase reactor power. Feedwater Control [JB] was transferred from Startup Level Control to Single Element Automatic Control at 1300 EDT. Two separate south reactor feed pump vibration alarms (5D28) [IB]
were received in the Main Control Room at 1306 and 1312 EDT. Investigation of these alarms revealed no abnormal indications or conditions. At 1322 to 1325 EDT multiple vibration related alarms were received for the south reactor feed pump [SJ], and the pump tripped at 1325 EDT. The north reactor feed pump was started in manual, and multiple Reactor Level High and Low alarms were received as operators worked to control level. A main condenser [SG] pressure increase was identified at 1329 EDT as condenser pressure rose from 0.6 psia to 2.2 psia. At 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> a manual scram was performed by placing the reactor mode switch in shutdown in response to the degrading condenser vacuum.
All rods fully inserted [JC] and operators used the standby feedwater system to restore water level to the normal band. The lowest post scram water level was +154 inches which is below reactor water Level 3 and above Level
- 2. As expected, the High Pressure Coolant Injection [BJ] and Low Pressure Coolant Injection Systems [BO] did not actuate. No SRVs actuated, and all isolations [JE] and actuations associated with reactor water Level 3 occurred as expected.
Entry into the South Reactor Feed Pump Room after the scram revealed damage to the south reactor feed pump turbine which resulted in main condenser vacuum leaks. The vacuum leaks were isolated and condenser vacuum improved and stabilized at 4 psia following the event. Decay heat was removed using the main condenser via the turbine bypass valves. The south reactor feed pump/turbine is expected to be out of service for an extended time period.
Plant configuration changes were made to isolate the south reactor feed pump/turbine from plant systems and the reactor was restarted using the north reactor feed pump to feed the reactor. A steady 68% power level was achieved on 7/30/2012.
Significant Safety Consequences and Implications
This event posed no significant safety implications because the reactor protection and safety related systems functioned as designed following the manual reactor trip. Important safety-related and non-safety related equipment performed as discussed in the description of the event, and plant response was as expected. There was no increase in reactor pressure, and the reactor core was adequately covered and cooled throughout the event.U.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION Fermi 2 05000341 2012 NUMBER NUMBER 3 OF 3 202 --
003 00 Therefore, the health and safety of the public were not affected by this event.
This event is being reported under 10 CFR 50.73(a)(2)(iv)(A), as an event or condition that resulted in manual actuation of the reactor protection system and a reactor scram. A 4-hour non-emergency notification was made to the NRC Operations Center at 1638 EDT on June 25, 2012 (EN 48047) in accordance with 10 CFR 50.72(b)(2)(iv)(B) for an actuation of the reactor protection system.
Cause of the Event
The direct cause of the event was a degradation in condenser vacuum resulting in a manual scram. The degrading vacuum was caused by vacuum leaks that occurred as the south reactor feed pump was damaged during the event.
The cause of the mechanical failure of the south reactor feed pump is still under investigation.
Corrective Actions
This event was entered into the Fermi 2 Corrective Actions Program. The associated root cause evaluation is still in progress and includes a tear down of the south reactor feed pump and failure analysis. Additional corrective actions may be identified as a result of this effort.
The condition of the north reactor feed pump was assessed and it was determined to be undamaged. Each feed pump was designed to perform at up to 70% feedwater flow. Modifications were performed isolating the south reactor feed pump from its steam and water supplies and from the main condenser, so that the plant could be restarted and run at a lower power level using the north reactor feed pump while the cause of the failure of the south reactor feed pump turbine is investigated and the turbine is rebuilt or replaced. Procedures were revised to reflect running the plant on the north reactor feed pump. Sustained operation at a reduced power level was evaluated and determined to be achievable. Additional monitoring of the north reactor feed pump was performed and additional data gathering equipment has been installed for the north reactor feed pump to assist Engineering in evaluating vibration if needed.
Additional Information
A.
Failed Component:
Component: Reactor Feedwater Turbine / Pump Function: Supplies Reactor Feedwater Manufacturer: Imo Delaval, Inc.
Model Number: Type KJDF Reactor Feed Pump Failure Cause: Unknown B.
Previous Licensee Event Reports (LERs) on Similar Problems:
There are no other LERs on similar problems noted within the past five years