WHERE
VALVES
ARE USED
THE NUCLEAR
POWER INDUSTRY
All of the 104 operating nuclear power plants in the United
States are legacy Generation II
plants designed more than 30 years
ago. These plants generate about
20% of U.S. electric power; and
over the past 25 years, a pervasive
culture of continuous improvement
has resulted in an impressive safety
record that includes an availability
factor of more than 91% 1.
This record, in tandem with
heightened concerns about energy
independence and greenhouse gas
emissions, has spurred a “nuclear
renaissance” of plant construction.
About 30 new nuclear plants have
been proposed, and license applications are currently under review.
These new Generation III designs
are significantly different than
existing plants and will require a
mix of exotic, special, control and
traditional valves. The Nuclear
Energy Institute (NEI) estimates up
to 24,000 nuclear-grade valves will
be required for the first eight plants
alone2,a demand that will challenge
and present opportunities for the
valve industry.
IN THIS NEW SERIES, WE FOCUS ON
DIFFERENT INDUSTRIES ‘WHERE
VALVES ARE USED.’ WE START WITH
AN OVERVIEW OF THE BURGEONING
NUCLEAR INDUSTRY AND EXPLAIN
THE TYPES OF VALVES AND ACTUATORS
BEING EMPLOYED IN TODAY’S NEWEST
GENERATION PLANTS.
BY STEVEN PAULY
TYPES OF NUCLEAR
VALVES
For the purposes of this article,
nuclear power plant systems can
be broken down into several basic
groups, each with its own mission
and requirements. The “nuclear
island group” includes piping
systems that directly interface with
the reactor. In the U.S., valves in
these systems are designed and
built to ASME Section III, Class 1
requirements. These valves are one
of the first lines of defense in
preventing any spread of radioactive contamination, and they have the highest
level of quality requirements.
Moving away from the reactor core, safety systems are in place that ensure safe
shutdown of the plant should something unfortunate happen. Many of these systems
provide emergency injection of water at various pressures and flow rates. The water
acts to cool the fuel because even after a nuclear reaction is shut down residual heat
would remain for many hours. Left unmitigated, that heat would be sufficient to melt
the fuel. These systems also can provide protection for the equipment needed to shut
down the plant or provide sampling to monitor the health of the fuel. Even in systems
not required to operate during an emergency, there are critical valves for sealing the
