tanks, 18-inch "long-bolt" manways8
provided
emergency venting. The weight of the manway
cover kept the opening sealed against the gasket.
When pressure developed to lift the cover, the
bolts allowed the cover to lift at least 1.5 inches.
Both of these relief devices vented directly to
the atmosphere.
All relief valves and rupture disks for pressure
vessels relieved directly to the atmosphere. Units
3 and 4 rupture disks were oriented upward
toward the north while the relief valves vented
to the east or the north. Tanks and vessels that
suffered the most severe damage were located
near the D-14 tank that served as the source of
feed to Unit 3. The unit operator blew nitrogen
into this tank just prior to the release.