05000266/LER-2012-001
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. Point Beach Nuclear Plant 05000301 | |
| Event date: | 04-26-2012 |
|---|---|
| Report date: | 06-25-2012 |
| 2662012001R00 - NRC Website | |
Description of the Event
NextEra Energy Point Beach (NextEra) Is providing this voluntary LER regarding the Operability of the Point Beach Nuclear Plant (PBNP) G-01 and G-02 Emergency Diesel Generators (EDGs). Emergency Diesel Generators G-03 and G-04 were not affected by the condition.
During a Component Design Bases Inspection (CDBI) completed at PBNP on October 3, 2006, NRC inspectors identified a concern with respect to the potential impact of tornado missiles on the exhaust stacks for the EDGs. In an NRC Task Interface Agreement (TIA), Evaluation of Point Beach Nuclear Plant Tornado Missile Protection Licensing Basis (TIA 2011-011), the NRC concluded that the licensing basis for PBNP required the EDG exhaust stacks to be protected from tornado missiles. In 2011, NextEra received a green non-cited violation for failure to fully meet GDC-2 requirements for protection of components from tornado and high wind loads. The NRC position in TIA 2011-011 was that the EDGs were Operable, but non-conforming based on a perceived tornado season.
NextEra determined in a prompt operability determination (POD) that the EDGs were Operable, but non- conforming.
On April 24, 2012, NRC issued a second TIA, Applicability of GDC Requirements in Operability Determinations and Assessment of the Point Beach Operability Determination for Emergency Diesel Generators with Respect to Tornado Missiles, dated April 24, 2012 (TIA 2012-07). In TIA 2012-07, the NRC raised concerns with respect to Operability of the EDGs due to the potential vulnerability of the EDG exhaust stacks to postulated wind-generated missiles.
Specifically, the NRC concluded, based on information available at that time, that NextEra had not demonstrated that G 01 and G-02 complied with PBNP General Design Criteria 2 (PBNP GDC-2), and that NextEra should reassess the Operability of the EDGs. Subsequently, historical documentation has been discovered indicating that separation and redundancy of the EDG exhaust pipes was the original plant design concept to provide protection from tornado missiles.
In light of the information in the TIA, on April 26, 2012, at 0800, Operations declared the EDGs Inoperable and entered TSAC 3.8.1.E for standby emergency power being out of service to 1 and 2 A05 safeguards busses.
Required action E.3 is to restore standby emergency power to operable status within 7 days.
During the time the diesels were declared Inoperable, a temporary modification was completed to protect the G-01 and G-02 EDG exhaust stacks. On May 2, 2012, at 0245, upon completion of the temporary modification for G-02, Operations realigned 4160V safeguards buses and exited TSAC 3.8.1.E.
This issue is not being reported as a safety system functional failure.
Cause of the Event
The EDGs were declared Inoperable based on the information contained in TIA 2012-07, which raised additional questions concerning the Operability of the EDGs which may not have been adequately addressed in POD Revision 5.
The decision to declare the EDGs inoperable was made by Plant Management to ensure the safety of the plant was not compromised while the issues identified in TIA 2012-07 were being addressed.
Analysis of the Event
The specified safety function of the emergency diesel generators, for which the exhaust stacks are supporting equipment, are to start, automatically load safe shutdown and/or emergency loads, and to continue to supply those loads to maintain safe shutdown or mitigate the consequences of analyzed accidents.
Following review of the Task Interface Agreement (TIA), Evaluation of Point Beach Nuclear Plant Tornado Missile Protection Licensing Basis, dated August 16, 2011 (TIA 2011-011), NextEra performed an Immediate Operability Determination for G-01 and G-02 EDGs. The conclusion made was the EDGs were Operable but non-conforming. Immediate compensatory actions were established to protect the health and safety of the public.
Specifically, if a Tornado Watch or Tornado Warning was issued by the National Weather Service that included the PBNP site, both G-01 and G-02 would be administratively declared Inoperable and the appropriate TSAC entered.
A prompt operability determination (POD) was completed and concluded that G-01 and G-02 EDGs were Operable but non-conforming. To mitigate the minimal residual risk of G-01 and G-02 EDGs, specific compensatory actions were implemented.
On April 25, 2012, a POD was requested to document information received from TIA 2012-07. On April 26, 2012, G-01 and G-02 were conservatively declared Inoperable pending further evaluation of the TIA. Emergency Diesel Generators G-03 and G-04 were not affected by the condition. On May 2, 2012, a partial turnover for temporary modification for missile protection for the EDG exhaust stacks was accepted by Operations for the G-02 EDG. The modification established a tornado missile protection structure for G-02 EDG exhaust pipe. Therefore, at 0245 on May 2, 2012, Operations realigned 4160V safeguards buses and exited TSAC 3.8.1.E. Subsequently, historical documentation has been discovered indicating that separation and redundancy of the EDG exhaust pipes was the original plant design concept to provide protection from tornado missiles.
Analysis of Safety Significance The issue screened as very low safety significance because the issue did not represent a loss of system safety function.
Corrective Actions
Temporary Modification, Wind and Missile Protection for Emergency Diesel Generator Exhaust Pipes Similar Events None
Failed Components
None