Junk Plant River Bend: Massive Run to Failure

This is so unprofessional! I can't imagine why aux building ventilation isn't safety related.  

Potential Loss of Secondary Containment Safety Function Due to Failure of Auxiliary Building Ventilation System  

On January 5, 2016, at 10:58 p.m. CST, with the plant operating at 100 percent power, the main control room alarm indicating high pressure in the auxiliary building [NF] actuated. Operators confirmed that the building pressure was out of specification. Secondary containment was declared inoperable, and the Division 2 standby gas treatment system [BH] was started. This action restored building pressure to the acceptable range, and secondary containment was declared operable at 12:27 a.m. on January 6. This condition is being reported in accordance wi,th 10 CFR 50.73(a)(2)(iv)(A) as an event that caused the secondary containment to be potentially incapable of performing its safety function.

INVESTIGATION and immediate ACTIONS 

The normal ventilation system was inspected, and it was determined that a combination of degraded components caused the condition:  

• Seals on the exhaust fan (**FAN**) discharge damper (**BDI\1P**) vanes were degraded. This allowed air to flow backwards through the idle exhaust fan, causing the total exhaust outflow to decrease and building pressure to increase: 

• The flow controller for the supply fan modulating dampers (**CDI\1P**) had failed, allowing excessive air flow that caused building pressure to increase.