05000445/LER-2013-001
| Comanche Peak Nuclear Power Plant (Cpnpp) Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i)(C), 50.54(x) TS Deviation 10 CFR 50.73(a)(2)(V) |
| 4452013001R00 - NRC Website | |
I. DESCRIPTION OF THE REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION:
10CFR50.73(a)(2)(i)(B), "Any operation or condition prohibited by the plant's Technical Specifications.
B. PLANT CONDITION PRIOR TO EVENT:
On January 8, 2013, Comanche Peak Unit 1 was in Mode 1, Power Operation, operating at approximately 100% power.
C. STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT WERE
INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE
EVENT
There were no inoperable structures, systems, or components that were inoperable at the start of the event that contributed to the event.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE
TIMES:
On December 22, 2012, a door seal test of the Unit 1 Emergency Air Lock (EAL) interior and exterior doors [EIIS: (NH)(AL)(DR)] was performed satisfactorily.
containment in order to perform preventive maintenance on the Unit 1 EAL. When attempting to open the Unit 1 EAL interior door, the door would not move. Investigation by the Maintenance personnel discovered the door position indication for the exterior door appeared to indicate the exterior door was not completely cycled.
Believing that the position of the exterior door's position indication might mean the interlock preventing both doors from being opened simultaneously was engaged, the Maintenance personnel attempted to operate the exterior door's interior handwheel in the close direction. That effort yielded handwheel movement of 1 to 1-1/2 turns, clearing the interlock. The interior door could then be opened as desired.
containment. Upon exiting the Unit 1 containment, the Maintenance personnel contacted their supervision and expressed their concern that under similar conditions personnel containment via the Unit 1 EAL in an emergency.
On January 10, 2013, Operations (Utility, Licensed) and Engineering (Utility, Non- licensed) personnel entered the Unit 1 containment in an attempt to recreate the as-found conditions of January 8, 2013 in order to determine past operability. As there were no photographs of the door position indications, the as-found conditions were recreated based on the recollection of the Maintenance personnel involved.
Upon establishing the January 8, 2013 as-found conditions based on the recollection of the Maintenance personnel involved, the EAL exterior door equalizing valve was discovered to be partially opened.
On January 14, 2013, a past operability determination was completed, which determined EAL exterior door was considered inoperable from December 22, 2012 until January 8, 2013. Furthermore, that condition represented a violation of Technical Specification (TS) 3.6.2 Condition A, which required the interior door to be locked per TS within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the exterior door becoming inoperable.
E. THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE, OR
PROCEDURAL PERSONNEL ERROR
The inoperable condition was discovered by Operations (Utility, Licensed) and Engineering (Utility, Non-licensed) personnel during their past operability investigation.
II. COMPONENT OR SYSTEM FAILURES
A. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE
Not applicable — No component or system failures were identified during this event.
B. FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED COMPONENT
Not applicable — No component or system failures were identified during this event.
C. SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF
COMPONENTS WITH MULTIPLE FUNCTIONS
Not applicable — No component or system failures were identified during this event.
D. FAILED COMPONENT INFORMATION
Not applicable — No component or system failures were identified during this event.
III. ANALYSIS OF THE EVENT
A. SAFETY SYSTEM RESPONSES THAT OCCURRED
Not applicable — No safety system responses occurred as a result of this event.
B. DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY
The Unit 1 EAL exterior door was inoperable from December 22, 2012 to January 8, 2013, approximately 384 hours0.00444 days <br />0.107 hours <br />6.349206e-4 weeks <br />1.46112e-4 months <br />.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT
The Emergency Airlock is a 5 ft-9 in. diameter double-door assembly, with 2 ft-6 in.
diameter doors. Each door is hinged and double-gasketed, with leakage test taps between the gaskets. The doors are interlocked so that if one door is open, the other cannot be activated. The doors are also furnished with a pressure-equalizing connection with equalizing valves which are mechanically operated.
The Emergency Airlock has provisions to pressure test at pressure Pa (48.3 psig) the space between the door seal gaskets for each of the airlock doors and the volume between the airlock doors. The design function of the emergency airlock is to maintain containment Isolation.
The personal safety function is to provide a way of exiting the containment in a loss of coolant accident (LOCA) event or loss of power to the containment. Power is shed to the personal airlock in a LOCA event to prevent inadvertent opening and breach of Containment.
The issue in this event was that the exterior door equalization valve was not fully closed which violated TS 3.6.2 Condition A in not locking the operable interior door. However, during this event the containment isolation was still maintained since the interior door was still operable.
Based on the above, there were no actual safety consequences and the health and safety of the public was not affected and this event has been evaluated to not meet the definition of a safety system functional failure per 10CFR50.73(a)(2)(V).
IV. CAUSE OF THE EVENT
Procedures associated with operation of the EAL doors did not provide adequate guidance to ensure Operators were successful in operating the Unit 1 EAL exterior door mechanism sufficiently to shut EAL exterior door equalizing valve and to clear the interlock.
During troubleshooting efforts, it was discovered that that in 1985, a decision to not activate the valve position limit switches for the EAL door equalizing valves was made by the utility. This eliminated the only positive means of ensuring the valves were shut when required.
V. CORRECTIVE ACTIONS
Procedures for operation of the EAL doors will be revised to stipulate that when closing the EAL doors the door handwheel should be operated in the close direction until tight.
The EAL door equalizing valve limit switches will be activated and connected to the EAL door open alarms to provide Control Room personnel positive indication that the EAL doors and associated equalizing valves are shut.
VI. PREVIOUS SIMILAR EVENTS
There have been no previous similar reportable events at CPNPP in the last three years.