| 06-05-2003 | On March 7, 2003, at approximately 2:31 p.m. CST, the door assist device (DAD) on a secondary containment door in the auxiliary building failed, blocking the door open for a period of 78 minutes. At the time, the reactor was operating at approximately 87 percent power in end-of-cycle coastdown. This event is being reported in accordance with 10CFR50.73(a)(2)(v)(c) as a condition that could have prevented the fulfillment of the safety function of secondary containment. The failure was caused when an inappropriately installed set screw on an internal spur gear caused the gear to bind on its shaft when it should have been free to rotate. There were no actual consequences to the health and safety of the public. Engineering evaluations have shown that, had a design basis accident occurred while the condition existed, the main control room, exclusion area boundary, and low population zone doses would have remained within the limits of 10CFR50.67. |
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REPORTED CONDITION
On March 7, 2003, at approximately 2:31 p.m. CST, the door assist device (DAD) on a secondary containment door in the auxiliary building failed, blocking the door (**DR**) open for a period of 78 minutes. At the time, the reactor was operating at approximately 87 percent power in end-of-cycle coastdown. This event is being reported in accordance with 10CFR50.73(a)(2)(v)(c) as a condition that could have prevented the fulfillment of the safety function of secondary containment.
INVESTIGATION and IMMEDIATE CORRECTIVE ACTION Three secondary containment doors used for personnel access to the auxiliary building are equipped with assist devices that ease the opening of the door against differential pressure. The ventilation system draws a slight negative pressure in the building when operating normally, and in this condition, the doors may be opened manually without the use of the assist devices. When the standby gas treatment (GTS) system is operating, the differential pressure is greater, such that the doors are difficult to open.
The assist device incorporates a gear-operated jack that opens the door far enough to break the differential pressure, allowing the door to be fully opened by hand.
At the time of the event, the GTS system was running for a surveillance test, causing the differential pressure across the doors to be higher than normal. At 2:31 p.m., the door was opened by a station employee using the assist device. An apparent internal failure of the assist device caused the jack to stick in the extended position. The jack could not be retracted, thus the door could not be fully closed. Approximately 78 minutes later, the assist device was removed, and the door was successfully closed.
The assist device is not necessary for the safety function of the door, and it has not been re-installed pending completion of the failure analysis.
CAUSAL ANALYSIS
An internal inspection of the DAD found a set screw inappropriately installed in a spur gear. The spur gear is designed to rotate freely on its shaft for this application.
However, it had been drilled and tapped for a set screw. A vendor representative confirmed that the spur gears are commercially available parts that may be drilled and tapped by the manufacturer. The use of the set screw is not specified for this application, and it could not be determined why or when it was installed. The presence of the set screw caused metal shavings to be gouged from the gear shaft, which eventually caused the gear to bind. This caused the jack to stick in the extended position.
FACILITY NAME (1) DOCKET (2) LER NUMBER (6) PAGE (3)
CORRECTIVE ACTION TO PREVENT RECURRENCE
1. The DADs on the other auxiliary building door were inspected. Set screw holes were found in the corresponding spur gears, but no other set screws were found installed where not required.
2. The unnecessary set screw holes were peened to prevent installation of a set screw.
3. Maintenance instructions for the DADs will be revised with information concerning the unneccessary set screw hole in the spur gears.
PREVIOUS OCCURRENCE EVALUATION
A similar event occurred on August 8, 2000, as reported in LER 50-458/00-011-00.
That failure was caused by the loss of a jam nut from an external section of the DAD.
The corrective action for that event did not require disassembly of the DAD to the extent necessary for investigating the subject event of this report. Thus, the inappropriately installed set screw was not discovered at that time.
SAFETY SIGNIFICANCE
During the time the door was blocked open, the plant continued to operate normally.
There were no actual consequences to the health and safety of the public. Engineering evaluations have shown that, had a design basis accident occurred while the condition existed, the main control room, exclusion area boundary, and low population zone doses would have remained within the limits of 10CFR50.67.
(NOTE: Energy Industry Component Identification codes are annotated as (**XX**).)
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| | | Reporting criterion |
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| 05000397/LER-2003-010 | | | | 05000528/LER-2003-001 | Pressurizer Safety Valve As-Found Lift Pressure Outside of Technical Specification Limits | 10 CFR 50.73(a)(2)(v), Loss of Safety Function
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000277/LER-2003-001 | | | | 05000282/LER-2003-001 | | | | 05000301/LER-2003-001 | | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000261/LER-2003-001 | | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000251/LER-2003-001 | Channel Failure of Qualified Safety Parameter Display System | | | 05000316/LER-2003-001 | Unit 2 Shutdown In Accordance With Technical Specification 3.8.1.1, A.C. Sources, Action b | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown | | 05000324/LER-2003-001 | Main Steam Line Drain Isolation Valve Local Leak Rate Test Failures | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded | | 05000352/LER-2003-001 | | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000353/LER-2003-001 | | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | | 05000397/LER-2003-001 | | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition | | 05000364/LER-2003-001 | | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | | 05000529/LER-2003-001 | Reactor Trip with Loss of Forced Circulation Due to Failed Pressurizer Main Spray Valve | 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(v), Loss of Safety Function | | 05000278/LER-2003-001 | | | | 05000305/LER-2003-001 | | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000331/LER-2003-001 | | 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition | | 05000313/LER-2003-001 | | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | | 05000352/LER-2003-002 | | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000301/LER-2003-002 | | 10 CFR 50.73(a)(2)(v), Loss of Safety Function
10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown | | 05000305/LER-2003-002 | | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition | | 05000316/LER-2003-002 | Supplemental LER for Unit 2 Reactor Trip due to Instrument Rack 24 Volt Power Supply Failure | 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(iv), System Actuation | | 05000458/LER-2003-002 | | 10 CFR 50.73(a)(2)(v)(c) | | 05000348/LER-2003-002 | | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000341/LER-2003-002 | Automatic Reactor Shutdown Due to Electric Grid Disturbance and Loss of Offsite Power | 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000261/LER-2003-002 | | | | 05000285/LER-2003-002 | 4 | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000397/LER-2003-002 | | | | 05000499/LER-2003-002 | Safety Injection Actuation | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | | 05000440/LER-2003-002 | Reactor Scram as a Result of a Loss of Off-site Power | 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
10 CFR 50.73(a)(2)(iii) | | 05000400/LER-2003-002 | 1 O OF 3 3 | | | 05000266/LER-2003-002 | | 10 CFR 50.73(a)(2)(iv), System Actuation | | 05000250/LER-2003-003 | Unescorted Access Inappropriately Approved Due to Falsified Pre-Access Information | | | 05000261/LER-2003-003 | | 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor | | 05000219/LER-2003-003 | | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | | 05000247/LER-2003-003 | | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | | 05000530/LER-2003-003 | | 10 CFR 50.73(a)(2)(v), Loss of Safety Function
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000331/LER-2003-003 | | | | 05000529/LER-2003-003 | SOURCE RANGE MONITOR INOPERABLE DURING CORE RELOAD | 10 CFR 50.73(a)(2)(v), Loss of Safety Function
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | | 05000440/LER-2003-003 | Unrecognized Diesel Generator Inoperability During Mode Changes | | | 05000348/LER-2003-003 | | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | | 05000482/LER-2003-003 | REACTOR PROTECTION SYSTEM ACTUATION AND REACTOR TRIP DUE TO FEEDWATER ISOLATION VALVE CLOSURE | 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(iv), System Actuation | | 05000301/LER-2003-003 | | | | 05000302/LER-2003-003 | Reactor Coolant System Pressure Boundary Leakage Limit Exceeded Due To Pressurizer Instrument Tap Nozzle Cracks | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded | | 05000382/LER-2003-003 | RCS Pressure Boundary Leakage Due to Primary Water Stress Corrosion Cracking (PWSCC) | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded | | 05000397/LER-2003-003 | | 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)(iv), System Actuation | | 05000458/LER-2003-003 | | 10 CFR 50.73(a)(2)(v)(c) | | 05000454/LER-2003-003 | Licensed Maximum Power Level Exceeded Due to Inaccuracies in Feedwater Ultrasonic Flow Measurements | | | 05000282/LER-2003-003 | | | | 05000346/LER-2003-014 | Steam Feedwater Rupture Controls System Re-Energizes in a Blocked Condition | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
10 CFR 50.73(a)(2)(v), Loss of Safety Function
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
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