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NuclearPlantJournal.com Nuclear Plant Journal, September-October 2016
Ryan Vanston
Ryan Vanston P.E. is a Principal
Engineer in the Technology Development
Group for Westinghouse Electric
Company. Since
2012, he has been
involved with design
and implementation
of post-Fukushima
safety upgrades
for nuclear plants
around the world. He
is the lead engineer
for the patented
Westinghouse
Mobius™ continuous
mobile boration
system. Mr. Vanston
has also worked
as the Pressurized
Water Reactor
Owners Group Post-
Fukushima program
director and the lead
systems engineer for the AP1000
®
plant
chemical and volume control system.
He holds a Bachelor’s degree from
The Pennsylvania State University
and a Master’s degree from Carnegie
Mellon University, both in Chemical
Engineering. He also completed the
Nuclear Engineering Certificate
program at the University of Pittsburgh.
were limited in flow rate and duration.
This was the only system on the market
that could provide a continuous flow of
highly borated water and meet our needs.
By pre-deploying this system at the
beginning of an outage, we will increase
our safety margins through operational
flexibility by having an alternate method
of borating the plant if needed.”
Mobius resides on a skid to simplify
transport, storage and deployment and
provides borated coolant on demand.
The construction of the system allows
for over-the-road transport, power from
a site source or diesel generator, and
setup utilizing industry standard quick
disconnects. It requires four main inputs:
water, a power source, boric acid powder
and a pH control agent powder. From
these inputs, the trailer-sized system
synthesizes a solution at the specified
concentration and flow rate, which can
range from 2,000 ppm boron at 150
gpm to 7,000 ppm boron at 30 gpm,
depending upon plant requirements.
The powders are placed into hoppers
and added automatically at a calculated
rate by a metering conveying system.
The discharge flow rate and level of
boron concentration are monitored and
controlled using the automated control
Continuous
Mobile...
system and touch screen interfaces.
While the flow rate and concentration
can be adjusted online, it self-regulates
and processes boric acid powder at
a calculated rate
without need of
operator intervention
unless a change
is
desired.
The
automated operation
uses a programmable
logic controller to
dissolve boric acid in
a series of three batch
mixing tanks before
the borated coolant is
supplied. The timing
of the dissolution in
the three batchmixing
tanks is staggered,
which contributes to
a steady flow of the
borated fluid to the
final dilution tank of
the Mobius system for discharge to the
receiving plant system without requiring
additional pumps.
The current Mobius system design
focuses on using boric acid as the neutron
poison but the system can be designed
to accept other powder, such as sodium
pentaborate, as required by a reactor
design and accident scenario. The high
flow rate design allows the ability to keep
the core cool during early post-accident
scenarios when decay heat is the highest.
Final check – the trailer-size system is ready to roll.
Westinghouse completed acceptance
testing in August 2016 for the Palo Verde
implementation, and Mobius made its
way to Palo Verde in September 2016 to
support the spring 2017 outage. The plant
plans to make full use of the Mobius
system’s capabilities to fill refueling
water storage tanks more easily and
quickly, inject coolant into the reactor
coolant system if needed during off-
normal events and to augment or replace
normal plant batching operations.
Contact: Donna Ruff, Westinghouse
Electric Company, 1000 Westinghouse
Drive, Cranberry Township, PA 16066;
telephone: (412) 374-4705; email:
