Nuclear Plant Journal, March-April 2014 NuclearPlantJournal.com
21
WHEN IT
MATTERS
MOST. . .
Who would
you want to
be tied to?
Hukari
Ascendent
6XSSRUWLQJ WKH 1XFOHDU
6FLHQFH DQG 7HFKQRORJ\
,QGXVWU\ LQ
f (QJLQHHULQJ
f 1XFOHDU 6DIHW\ $QDO\VLV
f /LFHQVLQJ
f 4XDOLW\ $VVXUDQFH
f 3URMHFW 0DQDJHPHQW
f $QG PDQ\ UHODWHG
WHFKQLFDO GLVFLSOLQHV
303-384-9079
Hukari
Ascendent is a
Service-Disabled Veteran-Owned
Small Business
Please email your resume to:
In addition, please submit an on-line application at:
Hukari
Ascendent is an Equal Opportunity Employer
Research &
Development
Friction Stir Welding
Based on successful demonstration
tests using common reactor pressure
vessel materials, EPRI is designing
validation tests of the friction stir welding
process to be conducted at Oak Ridge
National Laboratory’s hot cell facility.
Solid-state welding technology is
being developed to allow the repair of
irradiated reactor pressure vessel internals
and attachments that cannot be welded
using current technologies. Known as
friction-stir welding, this innovation
could support extended nuclear plant
operations by ensuring structural integrity
while avoiding the need to replace these
critical components.
Over time, reactor pressure vessel
internals and attachments become
increasingly difficult to weld due to the
accumulation of helium (He) within
materials exposed to high levels of
radiation. The heat input associated with
conventional welding processes can
promote He-induced cracking. Current
welding technology is only applicable
below about 0.1 atom-part-per-million
(appm) He, a level reached in many
reactor pressure vessel locations after
about 30 years of operation.
Friction stir welding (FSW) is a
novel solid-state joining process in
which no physical melting occurs.
A specially designed tool is pressed
against the surfaces to be joined and
rotated as it traverses along the joint line,
creating frictional heating that softens
an underlying column of material. The
softened material flows around the tool
through extensive plastic deformation
and consolidates to form a continuous
joint. Dynamic recrystallization occurs
at reduced temperatures relative to
conventional welding technologies.
EPRI’sWeldingRepair&Technology
Center has demonstrated FSW in air and
underwater joining trials on test plates
fabricated from common reactor pressure
vessel materials, including 304 and 308L
stainless steel, Alloy 182, and Alloy 600.
EPRI also has conducted metallurgical
characterizations of crack and patch
repairs implemented on manufactured
defects. Based on these promising results,
FSW validation and optimization studies
will be conducted on irradiated materials
in a dedicated hot cell test facility at the
U.S. Oak Ridge National Laboratory
(ORNL).
Custom melts of 304 SS, 316 SS,
and Alloy 182 materials currently are
undergoing exposure at ORNL’s High
Flux Isotope Reactor to generate elevated
He levels representative of 40 to 70
years of commercial reactor operation
at internals locations. In 2015, EPRI
and ORNL will evaluate FSW and
other advanced welding techniques on
irradiated samples with 10, 20, and 30
appm He. This work and parallel model
validation studies will inform design of
FSW tools and processes optimized for
reactor pressure vessel applications.
Contact: Greg Frederick, telephone:
Acoustic Mouse
EPRI has achieved a key milestone
in the development of the acoustic mouse,
demonstrating full-matrix image capture
using a sparse-array probe.
EPRI recently applied advanced
ultrasonic transducers to validate the
use of sparse-array technology for
generating accurate 3-D images of
inspection volumes. Sparse arrays and
other innovations offer potential to
greatly reduce the hardware and software
requirements associated with field
implementation of handheld, real-time
ultrasonic imaging systems.
Nuclear and fossil power plants
apply ultrasonic testing (UT) to inspect
plant components, assess condition,
quantify service-induced degradation,
and support run/repair/replace decisions.
Manual UT scans provide operators with
immediate insights but may not record
the data, while computer-encoded (often
