05000331/LER-2010-003, Regarding Unplanned Manual Reactor Scram Due to Increasing Turbine Vibrations
| ML101790067 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 06/25/2010 |
| From: | Costanzo C NextEra Energy Duane Arnold |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NG-10-0351 LER 10-003-00 | |
| Download: ML101790067 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(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)(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), System Actuation |
| 3312010003R00 - NRC Website | |
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June 25, 2010 u.s. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 Duane Arnold Energy Center Docket 50-331 License No. DPR-49 Licensee Event Report #2010-003-00
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DUANE ARNOLD NG-10-0351 10 CFR 50.73 Please find attached the subject report submitted in accordance with 10 CFR 50.73. This letter makes no new commitments or changes to any existing
commitments
Christopher R. Costanzo Vice President, Duane Arnold Energy Center NextEra Energy Duane Arnold, LLC NextEra Energy Duane Arnold, LLC, 3277 DAEC Road, Palo, IA 52324
NRC FORM 366 (9-2007)
PRINTED ON RECYCLED PAPER NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
APPROVED BY OMB NO. 3150-0104 EXPIRES: 8/31/2010 Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Records and FOIA/Privacy Service Branch (T-5 F52), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to infocollects@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202 (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME Duane Arnold Energy Center
- 2. DOCKET NUMBER 05000331
- 3. PAGE 1 OF 4
- 4. TITLE Unplanned Manual Reactor Scram due to Increasing Turbine Vibrations
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME DOCUMENT NUMBER 05000 04 26 10 2010 003 0
06 25 10 FACILITY NAME DOCUMENT NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 1 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A)
X 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 14%
20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)
OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
VOLUNTARY LER
- 12. LICENSEE CONTACT FOR THIS LER NAME TELEPHONE NUMBER (Include Area Code)
Bob Murrell, Engineering Analyst 319-851-7900 CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX
CAUSE
SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
X NO SUBMISSION DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On April 26, 2010, at 0300, while in day 1 of a 31 day Limiting Condition for Operation (LCO) for inoperable Primary Containment Isolation Valves (Traversing Incore Probe Drive Ball Valves), during the process of shutting down the plant for a planned outage to investigate an increase in Drywell leakage, a manual scram was inserted. The manual scram was inserted due to elevated vibration readings on Main Turbine Bearing number 6. The reactor scram and associated turbine trip was initiated at approximately 14% power in anticipation of reaching Main Turbine vibration limit.
The cause of the increase in bearing vibration was determined to be from a turbine rub. Turbine rubs can be induced in operating configurations of high turbine gland seal pressure with low main condenser back pressure. This configuration existed during the April 26, 2010 shutdown. The catalyst for inducing the rub was an excessive Low Pressure Turbine cool down rate which allowed one of the two Low Pressure Turbine casings to cool more than the other. This difference in casing temperatures created the formation of a rub which resulted in localized heating of the turbine shaft and resulting increase in vibration readings.
There were no Systems, Structures, or Components inoperable at the time of the scram that contributed to the event. There were no actual safety consequences and no effect on public health and safety as a result of this event.
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
PRINTED ON RECYCLED PAPER Interim Corrective Actions:
Added limits to the Precautions and Limitations section of IPOI 4 for condenser pressure, condenser pressure changes, Steam Packing Exhauster vacuum, and Steam Seal Header pressure.
Added new caution statement and additional direction in Operating Instruction (OI) 646, Extraction Steam and Feedwater Heaters, for removing the Second Stage MSRs to direct slowly closing the control valves and emphasize maintaining MSR outlet temperatures within 50 °F of each other.
Corrective Actions to Prevent Recurrence:
Implement existing work orders on the Second Stage MSR steam supply control valves to replace the resistor responsible for providing incorrect input to the controllers prior to shutting down for Refuel Outage 22.
V. Additional Information
Previous Similar Occurrences:
A review of LERs over the previous 3 years revealed the following similar occurrence:
LER 2009-001 - Manual Reactor Scram due to Loss of Condenser Cooling LER 2009-003 - Unplanned Manual Scram due to Increasing Reactor Water Level Neither of the similar events had root causes similar to the event being reported by this LER, and therefore, prior corrective actions from those events could not have prevented this event.
EIIS System and Component Codes:
SB - Main/Reheat Steam System IG - Incore Monitoring System TA - Main Turbine System JD - Reactor Power Control System
Reporting Requirements
This event is reportable under 10CFR50.73(a)(2)(iv), 'System Actuation.