05000387/LER-2014-002
| Susquehanna Steam Electric Station Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| Initial Reporting | |
| ENS 49821 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| 3872014002R00 - NRC Website | |
EVENT DESCRIPTION
Initial Plant Conditions/Status of Structures, Systems, and Components At 0105 hours0.00122 days <br />0.0292 hours <br />1.736111e-4 weeks <br />3.99525e-5 months <br /> on February 12, 2014, secondary containment alignment for removal of the refuel floor hatch was completed to support moving fuel bundles from the railroad bay to the refuel floor.
The event being reported in this LER involved a secondary containment door that was discovered ajar. There was no other equipment inoperable at the start of the event that contributed to the event.
Unit 1 — Mode 1, 99 percent Rated Thermal Power Unit 2 — Mode 1, 99 percent Rated Thermal Power
Description of the Event
On February, 12, 2014 at approximately 0711 hours0.00823 days <br />0.198 hours <br />0.00118 weeks <br />2.705355e-4 months <br />, while performing shift rounds, a security officer found Door- 612 wedged open. Door-612 provides access from the HVAC room to the Central Railroad Bay. With secondary containment aligned with the refuel floor hatch open, this door must be in the closed position with a sign posted on both sides of the door reading: "Secondary Containment Boundary, Emergency Use Only, Notify Control Room to Evaluate LCO if Door is Opened." The door was wedged open as the Secondary Containment Boundary Door sign was between the door and frame (hinge side). The security officer immediately contacted the Central Alarm Station (CAS) with his findings. At approximately 0712 hours0.00824 days <br />0.198 hours <br />0.00118 weeks <br />2.70916e-4 months <br />, the CAS contacted the Control Room. Prior to departing the Door-612 area, the security officer closed the door and re-positioned the sign. The action of closing the door restored the required configuration and secondary containment integrity. Nuclear Operations performed a status walkdown to ensure no other secondary containment door was found in this condition. Secondary Containment differential pressure was maintained throughout the period that Door-612 was open.
Reporting Criteria The event was reported under 10CFR50.72(b)(3)(v) as an event that, at the time of discovery, could have prevented the fulfillment of the safety function (EN 49821). This event is also reportable as an LER in accordance with 10CFR50.73(a)(2)(v) as an event that could have prevented the fulfillment of the safety function.
Investigation Normal differential pressure against door requires force to be exerted to close and latch door.
The operators who were the last personnel to utilize Door-612 were interviewed. Based on the interviews, the operators noted no abnormalities with Door-612 and challenged the door latch to confirm that it was in a latched condition prior to leaving area.
Plant personnel, including Engineering and Operations personnel, inspected Door-612 on the day of the event and found no apparent issues. The door opened and closed properly and all seals and hardware were found to be in satisfactory condition. Tests were conducted on Door-612 and determined that, with the door confirmed closed and latched, the door could not be pulled open. Engineering concluded that the Door-612 latch was not degraded and, for Door-612 to have come open, the latch could not have been fully engaged.
CAUSE OF THE EVENT
Direct Cause — The Door-612 latching system was not fully engaged The investigation did not decipher a definitive cause for the latching system not being fully engaged; however, the following are the most probable causes:
Apparent Cause — It was not Apparent that Door-612 was sufficiently challenged therefore, it did not close properly.
Casual Factor -The latching device on Door- 612 is not sufficient to ensure proper closure of the door.
ANALYSIS/SAFETY SIGNIFICANCE
Actual Consequences:
There were no actual safety consequences as a result of the condition. The condition resulted in inoperability of Secondary Containment and entry into the LCO without knowledge for up to six hours.
Potential Consequences:
When Refuel Floor Hatch Alignment is in effect, Door-612 provides a Secondary Containment Boundary. The potential consequences of having this door open could result in a failure to maintain/establish secondary containment during accident conditions.
CORRECTIVE ACTIONS
Key corrective actions include:
1. Issue a Site Communication to define expectations to site personnel on requirements when closing Secondary Containment doors.
2. Replace Door-612, 613, 721, and 718 to include a three-point latching device.
3. Until the new latch design is installed, require Operations to inspect Door-612 every 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> when secondary containment is aligned in a refuel floor hatch removal configuration.
Only Door-612 is required to be checked every 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The other three related doors are not being required to be checked based on the following:
- Door-721 is not subject to the high differential pressures to which Door-612 is subject.
- Door-613 and Door-718 crosstie Zone 2 to no zones and thus cannot be open unless a secondary containment LCO is entered. Thus these doors are not routinely operated for personnel access.
PREVIOUS SIMILAR EVENTS
Technical Specification 3.6.4.1 Technical Specification 3.6.4.1 Reactor Building Zone I Ventilation Exhaust System Condition Report 544951 involving a similar event with Door-718 on January 30, 2004