On June 7, 2012, with Unit 2 at 100 percent power, Dominion determined that a series of gaps in a
HELB barrier rendered the equipment in the west 480V switchgear room
inoperable. Dominion entered
TS 3.8.2.1,
TS 3.8.2.1(a) action C, and
TS 3.3.3.5 action A. The openings were sealed and the switchgear room was returned to
operable status at 1605 on June 8, 2012. Dominion determined that this condition may have existed since initial construction. In the past, Unit 2 has implemented compensatory cooling to the west switchgear room when normal ventilation was
OOS. Compensatory cooling includes opening one of the doors to the switchgear room. This could allow the steam from the
HELB to impact safety related equipment in other areas. The inspectors determined that there was a performance deficiency in that Dominion did not ensure that the gaps in switchgear room
HELB barrier were sealed. Additional information is necessary for the inspectors to determine if the issue is more than minor. The information required is the determination of safety related equipment that would be affected by the
HELB. This information will be available upon completion of Dominions detailed formal analysis. Upon receipt of the above information, the NRC will assess whether the performance deficiency is more than minor.
