An influx of tiny, jellyfish-like creatures last week forced the shutdown of one of the reactors at the Diablo Canyon nuclear power plant in
California. The creatures are called "Salp" and they can be held in the
palm of a hand, although they can grow up to four inches in length.
They maneuver in the water just like squid by pumping water through
their gelatinous bodies and ejecting it in a stream.
of an influx of the photoplankton they feed off, millions of the little
critters were swarming in the waters at Diablo Canyon, which sits on an
85-foot cliff overlooking the Pacific Ocean. Some hapless Salp were
getting sucked into the plant’s intake structure and pulled up against
screens that protect the condensers and heat exchangers from marine
of creatures passed right through the screens within the intake
structure and passed right through the plant; but others got caught up
against the metal mesh, clogging the screens. The plant’s Unit 1 has
been shut down since April 22 for a refueling outage that is expected to
last several weeks. On April 23, operators reduced power in the Unit 2
reactor to 15 percent as a protective measure. The Salp don’t pose a
danger to any of the plant’s safety systems, but operating at lower
power minimizes the impact of a shutdown, if one becomes necessary.
April 25, it did. The buildup of Salp in the intake prompted operators
to manually shutdown the reactor. All systems functioned as designed and
no unexpected equipment issues were encountered. Unit 2 restarted last