Unit 3
Technical Specification 3.3.8.1,
AC Sources - Operating, required
Emergency Diesel Generators (
EDGs) to be
operable in Modes 1, 2, and 3, and with multiple
EDGs inoperable, required all but one
EDG be returned to service in
2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or be in Mode 3 within
12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Mode 4 within
36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Contrary to this, between December 22, 2012, and January 9, 2013, the licensee determined that multiple
EDGs were
inoperable as a result of failed 3D
EDG and degraded 3A and 3B
EDG generator blower bearings. This TS violation was entered into the licensees
CAP as PERs 665217, 675339, and 675952. This finding represented an actual loss of function of the 3D
EDG for greater than the Technical Specification allowed outage time, and therefore, required a detailed risk evaluation. The regional Senior Reactor Analyst performed an analysis of the finding. The dominant results were loss of offsite power sequences with common cause
EDG failure combinations that result in injection and suppression pool cooling loss of function. Tornado and Seismic were not major contributors. The risk impact was determined to be very low safety significance (Green) for all three units.
