05000317/LER-2006-004, Re Reactor Trip Due to Loose Wire During Maintenance on Turbine Control System
| ML070470649 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/12/2007 |
| From: | Joseph E Pollock Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 06-004-00 | |
| Download: ML070470649 (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) 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 |
| 3172006004R00 - NRC Website | |
text
Calvert Cliffs Nuclear Power Plant Constellation Generation Group, LLC 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 0
Constellation Energy February 12, 2007 U.S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
SUBJECT:
Document Control Desk Calvert Cliffs Nuclear Power Plant Unit No. 1; Docket No. 50-317; License No. DPR 53 Licensee Event Report 2006-004 Reactor Trip Due to Loose Wire During Maintenance on Turbine Control System The attached report is being sent to you as required by 10 CFR 50.73.
Should you have questions regarding this report, please contact Mr. Jay S. Gaines at (410) 495-4922.
Very truly yours, Joseph E. Pollock Plant General Manager JEP/SMR/bjd
Attachment:
As stated cc:
D. V. Pickett, NRC S. J. Collins, NRC Resident Inspector, NRC R. I. McLean, DNR
- 71EQ2ý
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007
, the NRC may digits/characters for each block)inot conduct or sponsor, and a person Is not required to respond to, the
- 3. PAGE Calvert Cliffs Nuclear Power Plant 05000317 OF 004
- 4. TITLE Reactor Trip Due to Loose Wire During Maintenance on Turbine Control System
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILMES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTHFACILITY NAME
____ INUMBER NO.
FACILITY NAME DOCKET NUMBER 12 12 2006 2006 1- 04 00 102 12 2007
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check a# that apply) o1 20.2201(b) 0I 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii)
[1 20.2201(d) 0 20.2203(a)(3)(ii)
[0 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A)
[o 20.2203(a)(1) 0 20.2203(a)(4)
[0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viil)(B) 0_o 20.2203(a)(2)(i)
[3 50.36(c)(1)(i)(A)
[0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 0 20.2203(a)(2)(Ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
[0 50.73(a)(2)(x)
[o 20.2203(a)(2)(iii)
[I 50.36(c)(2)
[0 50.73(a)(2)(v)(A)
[0 73.71(a)(4) o 20.2203(a)(2)(iv)
[I 50.46(a)(3)(ii)
[0 50.73(a)(2)(v)(B)
[0 73.71(a)(5) 100 E-20.2203(a)(2)(v)
[0 50.73(a)(2)(i)(A) 03 50.73(a)(2)(v)(C) 0 OTHER [o 20.2203(a)(2)(vi)
[I 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify In Abstract below or In (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366,4)
A review of the trip and activities associated with the main turbine maintenance determined that the affected turbine control valve unexpectedly stroked shut when the selected VSVO card was deenergized because a broken wire on another VSVO card caused an erroneous position indication for the affected turbine control valve. Under these operating conditions, the turbine control valve should have remained 56 percent open. However, the erroneous position indication caused the control system to assume the valve was 93 percent open. The Mark VI turbine control system attempted to correct the indicated valve position by closing the valve further. The closure of the affected turbine control valve resulted in a rise in reactor coolant pressure since less energy was removed from the Reactor Coolant System.
An inspection was performed on the valve interface box for the affected turbine control valve and a broken wire was found on the Linear Variable Differential Transformer field cable. The wire was re-lugged and testing was performed to verify that the system was operating properly.
Maintenance was completed on the system with replacement of the VSVO cards prior to restart of the Unit.
An apparent cause evaluation (IRE-018-885) determined that the cause of the trip was the broken wire. The wire was repaired and additional inspections were performed to verify there were no other broken wires.
III.
ANALYSIS OF EVENT
The planned maintenance activity on December 12, 2006 involved de-energizing one of the three redundant logic branches of the MARK VI turbine control system. The control system self-diagnostics did not detect the broken wire on the Linear Variable Differential Transformer field cable from the interface box. The turbine control system began shutting the affected turbine control valve due to the combination of the de-energized logic branch plus the broken wire.
Control Room Operators manually tripped the reactor when Reactor Coolant System pressure increased.
This event resulted in manual actuation of the Reactor Protective System and is therefore reportable pursuant to 10 CFR 50.73(a)(2)(iv)(A). An immediate Event Notification Report was made to the Nuclear Regulatory Commission (NRC Event 43046). Condition Report IRE-018-885 was initiated to capture this event.
There were no actual nuclear safety consequences incurred from this event. An estimated conditional core damage probability of 3E-06 and an estimated conditional large early release probability of I E-07 were calculated for this event.
(If more space is required, use additional copies of NRC Form 366A)
IV.
CORRECTIVE ACTIONS
A.
The wire was repaired and additional inspections were performed to verify there were no other broken wires. Preventative maintenance will be performed during refueling outages to check for wire integrity.
B.
A software upgrade will be installed during the 2008 Refueling Outage to allow the observation of Linear Variable Differential Transformer field input values and failures.
V.
ADDITIONAL INFORMATION
A.
Component Identification Component Main Turbine Control Valve 3 IEEE 803 EIIS Function SCV IEEE 805 System ID TA B.
Previous Occurrences
A review of Calvert Cliffs' events over the past several years was performed. No previous occurrences were identified involving a reactor trip due to a broken wire in the main turbine control system.