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NuclearPlantJournal.com Nuclear Plant Journal, September-October 2014
Inspection of..
dose area. The vendor used the same
personnel to execute the performance
training and the tool installation and
removal at Surry; thus maximizing
dose savings. The Dominion Project
Team at Surry also conducted full scale
mock-ups of the water shield tanks and
the shielded work platform to address
personnel access and tooling installation
and removal requirements . This enabled
the Team to identify and promptly correct
any safety and technical concerns before
the shielded work platform was installed
in the high dose area and became
contaminated. The safe execution of the
Core Barrel Examination Project was a
direct result of the Team’s commitment
to operational excellence. Contributing
quality measures included: extensive
pre-planning for tool development
requirements, the use of mock-ups for
tooling optimization and personnel
training performance, and the execution
of detailed pre-job briefs as well as
supervisory oversight and management
reviews on the use of Human Performance
tools.
Cost Savings
The total cost savings to Dominion
for the SPS -1 automated CB examination
project is approximately $1,065,220.
Overall cost savings of $4,260,880 will
be realized by Dominion for use of the
automated examination tool at all four
Dominion units that have this unique
CB configuration (Surry Units 1 & 2
and North Anna Units 1 & 2). This cost
savings was realized as a result of the
unique automated tool design and the
resulting overall dose saving for the
tool operational performance. This
design also enabled per unit cost savings
of approximately $655,620 by the
elimination of three separate task teams
that are usually required to perform
parallel operations while on critical path.
Automated tool operation, use of the
special shielded platform, and operational
efficiencies enabled the per unit total dose
savings contribution of approximately
$409,625. The per unit dose cost savings
from minimizing personnel exposure by
the use of the automated tool and the
efficiencies in the Project execution were:
13.741 Rem ($343,525) and 2.643 Rem
($66,100) respectively. The Dominion
cost basis estimate is one man Rem
equals $25K. The dose/cost saving was
achieved by the following means:
•
Using the automated examination
tool to minimize personnel in the
examination area.
•
Conducting the upper girth weld
inspection while the core barrel
was still in the vessel, thus taking
advantage of more water shielding.
•
Using mock-ups of the water shield
tanks and work access platform.
•
Using dedicated RP Support and RP
Supervisory Oversight.
•
Placing support equipment in low
dose areas.
•
Applying Lessons learned from
previous outages (location of sub
operator, changing out of the crane
operator during the Core Barrel lift).
•
Maintaining reactor cavity water
level control 4 inches from the top
of the operations deck; this is about
1 foot higher than required. (Dose
rates are reduced by half for each 5.5
inches of water).
•
Using the shielded work platform
(a calculated 26% reduction in dose
rates from shielding).
•
Adding a second hand rail on the
work platform for tool and camera
accessories, so crews would not lean
over the shielded railing.
Innovation
The Project Team’s efforts resulted
in the Lower Girth Weld Inspection Tool
(LGWIT); designed to work with the
Surry unique core barrel configuration.
The core barrel extends out of the
water by 40 inches; the lower girth
weld is behind a thermal shield, and
when Surry’s core barrel is in the stand,
approximately 15% of the examination
area is against the wall and is not
accessible. AREVA designed the Lower
Girth Weld Inspection Tool (LGWIT) to
obtain the maximum examination area
coverage. The LGWIT was designed to
be easily installed on and removed from
the Core Barrel safely while minimizing
personnel exposure. The tool cart
platform attaches itself to the Core Barrel
by vortex suction devices with sufficient
suction to maintain stability, while
allowing it to travel circumferentially on
the top of the thermal shield by a drive
wheel that obtains its drive force friction
by the tool weight. Axial positioning
is performed by the rigid segmented
mast to position the camera and traverse
the examination area. Positioning of
the high radiation tolerant camera is
maintained and recorded by encoders for
both the axial position on the weld and
the circumferential location on the core
barrel. This important feature provided
encoded EVT-1 examination data to
support future examination location
repeatability. The tool cart platform
has multi-motion capabilities to clear
obstacle on the component to maximize
examination coverage. The multi-motion
features include the following:
•
Pneumatic tilt to position itself
away from the Core Barrel to gain
clearance while traversing under the
outlet nozzle boss area.
•
Z-motion to lift the camera up over
alignment pins and thermal shield
hangers.
•
Hydraulic tilt to extend examination
coverage to shielded areas of weld
below obstructions.
The Lower FlangeWeld Examination
Tool also attaches to the cart platform,
extending down to the examination area,
and utilizes the same remote operated
features and encoding to accurately
position and record the examination
area for future repeatability. The Lower
Flange weld end effector tool utilizes
a Pan/Tilt/Zoom camera and integral
resolution card to support continuous
remote controlled examination and
picture quality resolution checks once
installed. The cart platform contains a
hydro laze cleaning nozzle for remote
operated automated cleaning of both
weld examination areas for the required
EVT-1 examination. Special testing
was conducted to establish the optimum
reaction force nozzle to maintain the
tool rigid and stable during all high
pressure water cleaning evolutions. The
new FOAK Lower Girth Weld Tool
successfully completed the required
License Renewal Amendment (LRA)
examinations of the Lower Girth Weld
and Lower Flange Weld with exceptional
picture quality and repeatability as noted
