05000348/LER-2015-005-01, Regarding Condition Prohibited by Technical Specifications Due to Turbine Driven Auxiliary Feedwater Design Issue
| ML16183A339 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 07/01/2016 |
| From: | Pierce C Southern Co, Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-16-0719 LER 15-005-01 | |
| Download: ML16183A339 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 3482015005R01 - NRC Website | |
text
Charles R. Pierce Regulatory Affairs Director July 1, 2016 Docket Nos.: 50-348 50-364 Southern Nuclear Operating Company, Inc.
40 Inverness Center Parkway Post Office Box 1295 Birmingham, AL 35242 Tel 205.992.7872 Fax 205.992.7601 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 SOUTHERN*\\
NUCLEAR A SOUTHERN COMPANY NL-16-0719 Joseph M. Farley Nuclear Plant-Units 1 and 2 Licensee Event Report 2015-005-01 Condition Prohibited by Technical Specifications Due to Turbine Driven Auxiliary Feedwater Design Issue Ladies and Gentlemen:
This Licensee Event Report revision is being submitted pursuant to the requirements of the Code of Federal Regulations, 10 CFR 50.73(a)(2)(i)(B) for Unit 1 and Unit 2.
This letter contains no NRC commitments. If you have any questions regarding the submittal, please contact Ms. Julie Collier at (334) 814-4639.
Respectfully s~ed, C.tii'P C. R. Pierce Regulatory Affairs Director CRP/JAC/cg Enclosure: Units 1 and 2 Licensee Event Report 2015-005-01
U. S. Nuclear Regulatory Commission NL-16-0719 Page2 cc:
Southern Nuclear Operating Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. D. G. Bast, Executive Vice President & Chief Nuclear Officer Mr. M. D. Meier, Vice President-Regulatory Affairs Mr. D. R. Madison, Vice President-Fleet Operations Mr. B. J. Adams, Vice President-Engineering Ms. C. A. Gayheart, Site Vice President-Farley Ms. B. L. Taylor, Regulatory Affairs Manager-Farley Mr. J. E. Purcell, Operating Experience Coordinator-Farley RTYPE: CFA04.054 U.S. Nuclear Regulatory Commission Ms. C. Haney, Regional Administrator Mr. S. A. Williams, NRR Project Manager-Farley Mr. P. K. Niebaum, Senior Resident Inspector-Farley
Enclosure Joseph M. Farley Nuclear Plant-Units 1 and 2 Licensee Event Report 2015-005-01 Condition Prohibited by Technical Specifications Due to Turbine Driven Auxiliary Feedwater Design Issue
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 1013112018 (11-2015)
, the NRC may nol conduct or sponsor, and a person is not required to respond to, the infonnation collection.
- 3. PAGE Joseph M. Farley Nuclear Plant, Unit 1 05000 I 348 1
OF 3
- 4. TITLE Condition Prohibited by Technical Specifications Due to Turbine Driven Auxiliary Feedwater Design Issue
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
SEQUENTIAL I REV NO FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER MONTH DAY YEAR
~oseph M. Farley Nuclear Plant, Unit 2 05000-364 07 01 2016 FACILITY NAME DOCKET NUMBER 11 20 2015 2015 005 -
01
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.2201 (bl D 20.2203(a)(3)(i)
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) 1 D 2D.22D1(dl D 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D 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)
D 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(a)(2)(iii)
D 50.36(c)(2)
~ 50.73(a)(2)(v)(B)
D 73.71(a)(5) 100%
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1)
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)
~ 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(ii) 0 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in NRC Fonn 366A
- 12. LICENSEE CONTACT FOR THIS LER ICENSEE CONTACT ELEPHONE NUMBER (Include Area Code)
Julie Collier 334-814-4639 CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX B
BA sc W290 y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR DYES (If yes, complete 15. EXPECTED SUBMISSION DATE) I2J NO SUBMISSION DATE ABSTRACT (Umit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On 11/20/2015 at 12:33 CST with Unit 1 operating at 100 percent thermal power the Turbine Driven Auxiliary Feedwater Pump (TDAFWP) failed to start during an inservice test due to a turbine overspeed. The plant entered Technical Specification (TS) 3.7.5 Condition B. The overspeed trip was caused by a design issue that had been introduced into the governor control system in April, 2015, making the TDAFWP inoperable since that time, which was a period of time longer than allowed by TS 3. 7.5. The same design change was implemented on the Unit 2 TDAFWP in January, 2015. The Unit 2 TDAFWP was declared inoperable and TS 3.7.5 was entered on 11/22/15 at 07:50 CST. This is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B).
During the time of inoperability, there were two times when Unit 2 was left with a single AFW train in operation, which does not meet the TS Bases requirement for meeting the safety function for removal of residual heat.
Therefore for Unit 2 this condition is also reportable per 10 CFR 50.73(a)(2)(v)(B).
The cause of this condition was a misapplication of design inputs. Temporary Modifications were installed on both units to return the TDAFWPs to operable status. Permanent design changes will be pursued. A new user manual will be developed and implemented that is specific to Farley's Unit 1 and Unit 2 TDAFWPs and will I
have sufficient detail to ensure understanding of the operation of the TDAFWP Woodward 505 Controller.
A.
REQUIREMENT FOR REPORT YEAR 2015 SEQUENTIAL NUMBER 005 A design issue was introduced in April 2015 for the Unit 1 Turbine Driven Auxiliary Feedwater (TDAFW) system, and in January 2015 for Unit 2, which caused the TDAFW systems to be inoperable for a period of time longer than allowed by Technical Specification (TS) 3.7.5. This is reportable as an operation or condition prohibited by TS per 10 CFR 50.73(a)(2)(i)(B).
While the Unit 2 TDAFWP was considered to be inoperable there were two instances when a Motor Driven Auxiliary Feed Water Pump (MDAFWP) train accrued unavailability hours, in April and in May of 2015. This left Unit 2 with only a single AFW train in operation. The Technical Specifications (TS) Bases require availability of at least two of the three Auxiliary Feedwater (AFW) pumps for the AFW system to perform its safety function. Therefore for Unit 2 this condition is also reportable per 10 CFR 50.73(a)(2)(v)(B) as condition that could have prevented the fulfillment of a safety function of a system needed to remove residual heat.
B.
UNIT STATUS AT TIME OF EVENT Unit 1, Mode 1, 1 00 percent power Unit 2, Mode 1, 1 00 percent power
C. DESCRIPTION OF EVENT
On 11/20/15 at 12:33 CST the Unit 1 Turbine Driven Auxiliary Feedwater Pump (TDAFWP) failed to start during the quarterly inservice test due to a turbine overspeed upon startup. The failure to start occurred when the turbine exceeded its mechanical overspeed setpoint of 4480 revolutions per minute (rpm) and caused the trip and throttle valve to go closed. The undesired effect on the plant was an inoperable train of AFW and entry into Technical Specification (TS) 3.7.5 Condition B with a required action to restore the TDAFWP to an operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Troubleshooting revealed that a design vulnerability introduced by a design change implemented during the Unit 1 Refueling Outage in April 2015, 1 R26, allowed more steam to be admitted to the turbine and caused the turbine to overshoot pre-programmed start sequence setpoints resulting in a controller logic fault. The design issue was associated with the Woodward 505 Controller and the Magnetic Pick Up (MPU) Override timer setting and led to programming conflicts which allowed the overspeed event to occur.
REV NO OJ A Temporary Modification was installed on the U1 Turbine Driven Auxiliary Feedwater (TDAFW) controller allowing the U1 TDAFWP to be returned to operable status and the LCO to be exited on 11/22/15 at 04:30 CST. This design change had also been implemented on the Unit 2 TDAFWP in January 2015.
I The Unit 2 TDAFWP was also declared inoperable and TS 3.7.5 was entered on 11/22/15 at 07:50 CST.
A Temporary Modification was installed on the Unit 2 TDAFW controller allowing the TDAFWP to be returned to operable status and the LCO was exited on 11/22/15 at 15:26.
D. CAUSE OF EVENT
YEAR 2015 SEQUENTIAL NUMBER 005 The cause of this condition was a misapplication of design inputs. A lack of adequate information when completing a previous design change caused engineers to overlook a failure mode. The Unit 1 TDAFWP tripped on overspeed due to a design change which allowed the governor valve to admit more steam at REV NO 01 start up due to the MPU override timer being changed from 10 seconds to 600 seconds. This condition I
had the potential to affect the Unit 2 TDAFWP.
E. SAFETY ASSESSMENT
This condition made both units' TDAFW pumps vulnerable to an overspeed trip since the design changes were made in April on Unit 1 and in January on Unit 2. However, there were no actual demands on either unit's system to start automatically during that time. In addition, the TDAFW pumps had been successfully started 21 times for Unit 1 and 13 times for Unit 2 for surveillance, post-maintenance, and troubleshooting purposes while the design issue existed. During the installation of the new governor setpoints for Unit 2, the TDAFWP was available due to the fact that Operators were ready to act if necessary to restore the pump. There was procedural guidance for this activity and the personnel were trained on performing the task. Therefore there was no adverse effect on the health and safety of the public.
F. CORRECTIVE ACTION
Temporary Modifications were installed on the U1 and U2 TDAFW controllers allowing them to be returned to operable status. Permanent design changes will be pursued through the plant's approved design process. A new user manual will be developed and implemented that is specific to Farley's Unit 1 and Unit 2 TDAFWPs and has sufficient detail to ensure understanding of the operation of the TDAFWP Woodward 505 controller.
G. ADDITIONAL INFORMATION
- 1) Failed Components:
Auxiliary Feedwater System [BA]
- 2) Previous Similar Events:
LER 2015-001-00 was submitted for Farley Unit 2 on 3/9/2015, and was supplemented on 1/14/2016 in LER 2015-001-01, for an event affecting AFW with a similar cause, concerning a design flaw in the TDAFWP governor control system.
LER 2011-001-00 was submitted for Unit 2 for an AFW overspeed trip event that occurred as a result of an inappropriately planned maintenance activity to correct an apparent wiring discrepancy that impacted turbine governor speed control.
- 3) Energy Industry Identification System Code:
Woodward Speed Controller, component [SC]
- 4) Other systems affected: There were no other systems, structures, or components that were affected by or contributed to the event.