Nuclear Plant Journal, September-October 2014 NuclearPlantJournal.com
31
6.
Why do you think U.S. utilities are
slow to upgrade to digital?
The nuclear power plants would stay
with the exact same analog equipment
they were built with for as long as they
could. And if they could buy the exact
same relay switch, breaker, motor, valve,
if they could buy the same thing until the
end of life-time, they would. Doing a
design change, specifically on a safety-
related piece of equipment, is very costly
because there’s a lot of investment to
make that change. Digital equipment is
something new to them. The majority
of the plants were completely analog.
And so, they’re still learning the failure
modes of digital equipment. They’re
still learning how to address using digital
equipment in a system that was designed
using analog equipment.
The NRC, EPRI, and IEEE standards
have all started to address doing software
verification and validation using
commercial grade developed digital
equipment in safety-related applications.
There are a lot guidelines and standards
just in the last five years that the utilities
the vendors, and the engineering
companies are still getting used to.
7.
Is there an interest in replacing
analog controls by the digital controls?
There are digital control systems for
chillers. There are digital control systems
for diesels. Even equipment like a
regulating transformer will have a digital
aspect for it. Virtually every piece of
equipment you would buy today has some
kind of digital aspect to it. And more and
more of those products are starting to
make their way into the industry, safety-
related and non-safety-related. There are
a few more qualification issues you need
to address. They still need to do seismic
qualification, for example, but then you
need to do Electromagnetic Interference/
Radio Frequency Interference (EMI/RFI)
testing.
That can be very difficult. So, we
have to modify the equipment to get it
to pass correctly. Software verification
and validation, making sure that the
software is good, robust and it can handle
perturbations. So, that’s something that
NLI does more and more every year.
And the industry is putting in much more
digital equipment than they ever have.
Just in the last five years, the industry has
addressed it much more than they did for
the first 20 years.
8.
Is circuit breaker replacement a
priority for utilities?
Low and medium voltage circuit
breaker replacement is one of the larger
products for NLI.
What’s nice about the new breakers
is that they’re maintenance free in most
applications. They do not even need
relubrication. The medium voltage
breakers have minimal maintenance,
whereas the existing breakers that
the plants were built with are very
maintenance intensive. They require
maintenance every 5 to 7 years, sometimes
complete overhauls, very expensive
overhauls, very expensive parts. So the
new breakers, the immediate benefit are
no maintenance or reduced maintenance.
The second immediate benefit is that
it’s not an obsolete product. The plants
were built with very old breakers, 1960s
technology. And so, they’re obsolete or
the parts that are needed to do overhauls
are obsolete.
9.
Are utilities considering replacing
relays?
Some of the protective relays require
a lot of maintenance and surveillance
testing to make sure that they work
correctly or they’re calibrated correctly.
The plants continue to buy products until
the end of time, if they’re available, but a
lot of those relays are becoming obsolete.
They’re being replaced with a digital relay
alternative. So, some of the protective
relay lines are still made available from
the OEMs, but they’re becoming very
expensive, very long lead times, because
they’re only selling them to the nuclear
industry. So, at some point, probably
in the next seven to ten years, they’re
going to have to look at digital relay
replacement. So, we’re going to have
to take an analog relay and put a digital
relay in its place because the old analog
relay just is not going to be available or
it’s just not going to be cost effective to
buy it. Calibration can be very difficult to
maintain on them. So, digital relays are
better, but again, the utilities are slowly
adapting to that technology.
10.
Are analog instruments being
replaced with digital?
Most plants were built with modular
electronic systems, instrumentation, and
control and drive mechanisms. Even
the reactor protective system was old
electronic modules. Many of these old
electronic modules are starting to be
replaced with digital equipment solutions.
Some of them triple redundant PLCs.
So, digital technology is being used for
replacing those old electronic modules,
usually on systems like the RPS or digital
rod controls or nuclear instrumentation.
They’re slowly starting to address digital
technology there because they just don’t
have a choice. The digital technology
provides a lot of benefits. It’s more
accurate. It runs cooler, does not require
calibration, is more accurate, etc. So,
once you have an understanding of the
new platform, it is a good choice.
Note: On the WSI side, they’re
specialized in specialty welding, remote
welding, large equipment removal
and installation. The NLI side offers
equipment solutions. So, NLI is more
products focused and WSI is more site
service focused.
Contact: Craig Irish, AZZ | NLI,
7410 Pebble Drive, Fort Worth, Texas
76118; telephone: (978) 618-6930,
email:
.
