Nuclear Plant Journal, September-October 2016 NuclearPlantJournal.com
33
it is simple such as peer to peer serial
communications and is deterministic.
It runs over and over again at a defined
cycle. It has an external test processor
system that monitors the protection
system’s operation, each cycle. If it sees
any deltas, it will alert the operator via
MCR alarm and automatically place itself
in a safe state (i.e., partial trip condition).
If the system has a locks up, there is a
watchdog timer that will detect and place
these affected channels in a defined safe
state We put the 25+ year old Eagle 21
system into Watts Bar Unit 2, so the
units would be the same. Actually, I
have more confidence in Eagle-21 than
some of the other newer systems due to
its performance history, self monitoring
design, and deterministic nature. You
exchange new issues with old issues.
3.
What do you mean by that, exchange
new issues?
You have different or new issues. I don’t
want to compare systems, but there were a
lot of issues over having the maintenance
terminal attached to all four divisions,
where Eagle 21has maintenance carts that
we can only attach one at a time. There’s no
cross divisional type issues/concerns. We
don’t have inner channel communications
and we don’t really need that. We’ve had
no spurious trips or actuations out of the
Eagle-21 during the past 25+ years. What
protects you from those events is your
voting/logic channel which isWestinghouse
Solid State Protection System (SSPS) for
most Westinghouse designs. You’ll get one
channel that goes to a trip state, but for SSPS
you need to have two out of three or two out
of four logic to get a trip or actuation. This
provides with some time to fix the problem
before another trip condition occurs. When
a partial trip occurs, the plant will enter into
the appropriate Limiting Conditions for
Operability (LCOs) while the problem is
being fixed.
4.
What vendors are involved?
For Sequoyah and Watts Bar, it’s
been Westinghouse on the protection
system side. We’ve have standardized,
as a fleet, on the non safety side with
Foxboro I/A. We first implemented a
Foxboro I/A system in the ‘90s at Browns
Ferry. Due to the Brown Ferry’s success,
Foxboro I/A has been migrated to
Sequoyah and now to Watts Bar. You gain
a lot of advantages from standardization.
You can develop Subject Matter Experts
(SME), on the standardized platform.
So, whether it’s a Foxboro, Ovation, or
Siemens platform, standardizing is very
important for a multi-unit, multisite. Our
SMEs at Browns Ferry were brought
up to Sequoyah during the Feedwater
controls upgrade to work with the
Sequoyah Nuclear Plant (SQN) system
engineer onsite. The Sequoyah individual
is now a SME. Those two SME then went
to Watts Bar when we were doing the
Watts Bar NSSS upgrade, and they were
critical to the success of that project.
We’re developing new SMEs at Watts Bar
now. This provides our fleet with a value
resource of SMEs. If we have a problem
at one site, we can get all our SMEs on
the line. Hey, here’s what’s going on.
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