05000446/LER-2009-001, Regarding Gamma-Metrics Calibration Impact on Containment Pressure and RCS Tcold
| ML100541585 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/11/2010 |
| From: | Madden F Luminant Generation Co, Luminant Power |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CP-201000194, TXX-10009 LER 09-001-00 | |
| Download: ML100541585 (9) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ix)(A) 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)(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 |
| 4462009001R00 - NRC Website | |
text
Rafael Flores Senior Vice President
& Chief Nuclear Officer rafael.flores@ Luminant.com Luminant Power
'P 0 Box 1002 6322 North FM 56 Glen Rose, TX 76043 Lum inant 254 897 5550 C 817 559 0403 F 254 897 6652 CP-201000194 Log # TXX-10009 Ref. # 10CFR50.73(a)(2)(ix)(A)
February 11, 2010 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION DOCKET NO. 50-446 SINGLE CAUSE PREVENTING FULFILLMENT OF A SAFETY FUNCTION FOR TWO CHANNELS IN DIFFERENT SYSTEMS LICENSEE EVENT REPORT 446/09-001-00
Dear Sir or Madam:
Enclosed is Licensee Event Report (LER) 09-001-00 for Comanche Peak Steam Electric Station (herein referred to as Comanche Peak Nuclear Power Plant) Unit 2, "Unit 2 Gamma-Metrics Calibration Impact on Containment Pressure and RCS Cold Leg Temperature Channels."
This communication contains the following new commitment which will be incorporated into the Comanche Peak Nuclear Power Plant (CPNPP) licensing basis as noted.
Number 3889101
Commitment
Procedures will be changed to improve the control and use of test equipment to prevent this type of grounding interaction in the future.
The commitment number is used by Luminant Power for the internal tracking of CPNPP commitments.
Should you have any questions, please contact Tom Daskam at (254) 897-0348.
zrE~Da A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway - Comanche Peak
- Diablo Canyon
- Palo'Verde
- San Onofre
- South Texas Project
- Wolf Creek
U. S. Nuclear Regulatory Commission TXX-10009 Page 2 2/11/2010 Sincerely, Luminant Generation Company LLC By:
Fred W. Madden Director, Oversight & Regulatory Affairs c -
E. E. Collins, Region IV B. K. Singal, NRR Resident Inspectors, Comanche Peak
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSIO APPROVED BY OMB NO. 3150-0104 EXPIRES: 8/31/2010 (9-2007)
, 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 COMANCHE PEAK NUCLEAR POWER PLANT 05000 446 1 OF 7
- 4. TITLE Unit 2 Gamma-Metrics Calibration Impact on Containment Pressure and RCS Tcold
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCUMENT NUMBER NUMBER NO.
I N/A 05000 12 14 2009 2009 001 00 02 11 2010 FACILITY NAME DOCUMENT NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITn'ED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b)
Ej 20.2203(a)(3)(i)
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- 10. POWER LEVEL "0
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El 50.73(a)(2)(x)
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[] 50.36(c)(2)
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VOLUNTARY LER
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)
Tim Hop~e - Nuclear Licensing Manager (254) 897-6370CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU" REPORTABLE IIFACTURER TO EPIX FACTUREIR TO EPIX
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION El YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
WZ NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On December 14, 2009, at 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br />, Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 was in Mode 1 at 100% power. A channel calibration on Unit 2 Train B Neutron Flux Monitoring System (Gamma-Metrics) resulted in the inoperability of channels in different systems: Unit 2 containment pressure channel 4, and Channel 4 of the Overtemperature N-16 and Overpower N-16 reactor trips.
When the test equipment being used for the channel calibration was disconnected from the Gamma-Metrics system, the affected control room indications returned to normal. The cause of this event was grounding the Gamma-Metrics system to current paths and ground loops which served to couple a voltage potential through the plant grounding system to the affected plant parameters. Completed corrective actions include: 1) A Maintenance Standing Order-was issued to control the use of test equipment that has the ability to ground a floating circuit, and (2) The shield cable ground was corrected for the Unit 2 containment pressure channel 3 and 4 main control board indicators. Planned corrective actions include procedure changes to improve the control and use of test equipment.
All times in this report are approximate and Central Standard Time unless noted otherwise.
NRC FORM 366 (9-2007)
PRINTED ON RECYCLED PAPER (If more space is required, use additional copies of SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES On December 14, 2009, two I&C technicians (Utility, Non-licensed) were assigned to perform a channel calibration on Unit 2 Train B Neutron Flux Monitoring System (Gamma-Metrics) [EIIS: (IG)]. An oscilloscope was used as part of the test equipment for the channel calibration, and the oscilloscope was powered by a control room power outlet, which is grounded to plant ground. Between about 0830 and 0924, the oscilloscope test leads were twice connected to the Gamma-Metrics system as part of the calibration.
During this same time frame, Unit 2 control room Reactor Operators (Utility, Licensed) observed plant computer alarms and abnormal, fluctuating indications for Unit 2 containment pressure [EIIS: (1K) (PI)], channels 3 and 4, and Reactor Coolant System (RCS) temperature [ElIS: (AB) (TI)]. The Unit 2 Unit Supervisor (Utility, Licensed) approached the I&C technicians performing the channel calibration, discussed the abnormal control room indications with them, and, as a result, the Gamma-Metrics channel calibration was suspended. The I&C technicians disconnected the oscilloscope test leads from the Gamma-Metrics system, and the affected control room indications returned to normal.
Believing that the fluctuating indications were related to a ground in the oscilloscope, the I&C technicians installed a two-prong grounding adapter between the oscilloscope's power cord and the plant power outlet. This action isolated the oscilloscope power cord from plant ground. The Gamma-Metrics channel calibration was then completed with no further adverse impact on plant indications.
(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 (If more space is required, use additional copies of (if more space is required, use additional copies of NRC Form 366A) (17)
V.
CORRECTIVE ACTIONS
Completed corrective actions for this event include:
(1) Maintenance Standing Order 2009-003, Revision 0, was issued on December 15, 2009, concerning test equipment use under various circumstances. Maintenance Standing Order 2009-003, Revision 3, is currently in effect; it was issued on January 28, 2010, to control the use of test equipment that has the ability to ground a floating circuit in Modes 1 or 2.
(2) An Operations Shift Order was issued on December 17, 2009, to discuss the event. The Operations Shift order has carried this information for a month.
(3) The ground loop problem on containment pressure channels 3 and 4 was corrected on January 14, 2010.
Planned corrective actions include procedure changes to improve the control and use of test equipment to prevent this type of grounding interactions in the future.
VI.
PREVIOUS SIMILAR EVENTS
The cause evaluation for this event revealed two previous similar events. However, there were no previous Corrective Action Program identified causative factor ties to Gamma-Metrics calibrations.
During a Unit 2 Train B Gamma-Metrics channel calibration on November 29, 2006, plant computer data indicated that channel 4 RCS Tcold fluctuated for approximately 10 minutes. The RCS Tcold fluctuations coincided with the time the oscilloscope would have been connected to the Gamma-Metrics system for the channel calibration. Unexpected control rod stepping also occurred during this same time period and was addressed in CR-2006-003927. Post-event cause analysis of the control rod event did not state if the Gamma-Metrics channel calibration was considered as a possible causative factor.
During a Unit 2 Train B Gamma-Metrics channel calibration on June 4, 2008, fluctuations were again noted in channel 4 RCS Tcold. During this channel calibration, the RCS Tcold channel fluctuated for approximately one hour, which corresponded to the time period when the oscilloscope was connected to the Gamma-Metrics system.
During both the November 29, 2006 and June 4, 2008 channel calibrations, the only recorded or reported indication fluctuation was on channel 4 RCS Tcold.
There have been no previous similar events where a single cause prevented the fulfillment of a safety function for two or more trains or channels in different systems.
NRIC FORM 366A (9-2007)
PRINTED ON RECYCLED PAPER