05000445/LER-2011-002
| 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)(v), Loss of Safety Function |
| 4452011002R00 - NRC Website | |
I. DESCRIPTION OF THE REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION:
Any operation or condition prohibited by the plant's Technical Specifications.
B. PLANT CONDITION PRIOR TO EVENT:
On September 17, 2011, at 2330 hours0.027 days <br />0.647 hours <br />0.00385 weeks <br />8.86565e-4 months <br />, 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 September 16, at 0727 hours0.00841 days <br />0.202 hours <br />0.0012 weeks <br />2.766235e-4 months <br />, the Unit 1 Containment Personnel Airlock (PAL) [EIIS: (NH)(AL)] was prepared for personnel entry for pre-outage work and personnel began entering the Unit 1 Containment at 0738 hours0.00854 days <br />0.205 hours <br />0.00122 weeks <br />2.80809e-4 months <br />. On September 16, 2011 at 1609 hours0.0186 days <br />0.447 hours <br />0.00266 weeks <br />6.122245e-4 months <br />, Security verified and notified the Unit 1 Control Room that all personnel had exited the Unit 1 Containment and the Unit 1 PAL was secured by Operations personnel (Utility, Licensed) at 1653 hours0.0191 days <br />0.459 hours <br />0.00273 weeks <br />6.289665e-4 months <br />.
On September 17, 2011, at 2330 hours0.027 days <br />0.647 hours <br />0.00385 weeks <br />8.86565e-4 months <br />, Comanche Peak Operations personnel (Utility, Licensed) were unable to pressurize the Unit 1 PAL during a routine performance of OPT-802A, "Appendix J Leak Rate Test of Personnel Air-lock Door Seals," which placed the PAL in an inoperable condition.
Upon investigation, a 10 inch piece of yellow and black tape was removed from the inner door sealing surface [EIIS: (NH)(AL)(DR)(SEAL)]. The tape had been used to demarcate a tripping hazard caused by the difference in height between the inner loading ramp and the PAL deck. The LCO was exited on September 18, 2011 at 0426 hours0.00493 days <br />0.118 hours <br />7.043651e-4 weeks <br />1.62093e-4 months <br /> upon a satisfactory re-performance of OPT-802A.
During the subsequent investigation of the event, CPNPP Engineering personnel determined that the PAL inner door was INOPERABLE for approximately 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> which violated the time requirements of Technical Specification LCO 3.6.2, "Containment Air Locks.
E. THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE, OR
PROCEDURAL PERSONNEL ERROR
During a routine performance of OPT-802A, "Appendix J Leak Rate Test of Personnel Air-lock Door Seals," Maintenance personnel (Utility, Non-licensed) discovered a 10 inch piece of tape on the inner door sealing surface.
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 Containment Personnel Airlock inner door would not have been able to perform its safety function and was inoperable from September 16, 2011, 1653 to September 18, 2011, 0426, a total of approximately 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT
Containment airlocks form part of the containment pressure boundary and provide a means for personnel access during all MODES of operation. On both air locks, doors are interlocked to prevent simultaneous opening. During periods when containment is not required to be OPERABLE, the door interlock mechanism may be disabled, allowing both doors of an air lock to remain open for extended periods when frequent containment entry is necessary. Each airlock door has been designed and tested to certify its ability to withstand a pressure in excess of the maximum expected pressure following a Design Basis Accident (DBA) in containment.
As such, closure of a single door supports containment OPERABILITY.
The DBAs that result in a release of radioactive material within containment are a loss of coolant accident (LOCA) and a rod ejection accident. In the analysis of each of these accidents, it is assumed that containment is OPERABLE such that release of fission products to the environment is controlled by the rate of containment leakage. The containment was designed with an allowable leakage rate of 0.1% of containment air weight per day.
This allowable leakage rate forms the basis for the acceptance criteria imposed on the SRs associated with the air locks. During the period of time that the Unit 1 Containment PAL inner door was Inoperable, no LOCA or rod ejection accident occurred that required the door to perform its safety function.
Based on the above, it is concluded that the health and safety of the public were unaffected by this condition 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
The cause of this event was a piece of tape attached to the sealing surface of the inner PAL door due to insufficient controls in place to ensure that the PAL seals remained free of foreign material during modes 1 through 4 containment entries.
V. CORRECTIVE ACTIONS
The immediate corrective action was the removal of the tape at the time of discovery, and the OPT- 802A was re-performed satisfactorily.
Procedure STA-620, "Containment Entry," will be revised to add the requirement that the last person exiting containment is responsible for verifying the PAL or Emergency Airlock (EAL) seals and sealing surfaces are clear of any foreign material or debris prior to closing the doors during containment entries while in Modes 1 through 4. This procedure revision is being tracked in the CPNPP corrective action program.
VI. PREVIOUS SIMILAR EVENTS
There have been no previous similar reportable events in the last three years involving inoperable Containment Personnel Airlock doors.