Technical Specification
LCO 3.6.6, requires two
containment spray trains and two containment cooling trains to be
operable in Modes 1, 2, 3 and 4. Condition C requires the
inoperable containment cooling train to be returned to service within seven days once it becomes
inoperable. Each train of containment cooling is comprised of two fully redundant fan units supplied with cooling water from a separate train of
service water. Each fan unit has two speeds of operation, high speed for normal operation and slow speed for post-accident operation. Under postaccident conditions, a single fan unit with at least 600 gpm of
service water flow provides sufficient cooling capacity to meet post accident heat removal requirements. Contrary to the above, the licensee made the A Train containment cooling
inoperable when they selected the 1B containment cooling fan for automatic start for the A train of containment cooling on January 23, 2012. The 1B fan had been started on January 18, 2012, and the closing springs for the circuit breaker failed to recharge, preventing any further subsequent fan starts. The licensee discovered the motor cut-off switch for the circuit breakers closing spring charging motor had failed, preventing the circuit breakers closing springs from being charged. This condition remained undiscovered until February 15, 2012, when the licensee attempted to start the 1B containment cooling fan and it failed to start. The 23 days that Train A containment cooling was
inoperable exceeded the seven days allowed by
LCO 3.6.6, and the subsequent
6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to enter Mode 3 and the
36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> to enter Mode 5. The licensee entered this condition in their
CAP as CR 407862. This finding was assessed using
IMC 0609, Phase 1 screening worksheet of Attachment 4 and Appendix H. The finding was determined to be of very low safety significance (Green), because the
inoperable equipment impacted late containment failure and source terms but not
large early release frequency.
