IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
and having a variety of inert
gas voids. The pancake probe
when used in conjunction with
a scanner is expected to detect,
image and locate voids in fuel
pins and hence, detailed
experimental studies have been
carried out.
In order to simulate the voids
in sodium column, a 0.3 mm
thick aluminium tube having
electrical conductivity nearly
equal to sodium has been
chosen and a variety of holes,
notches and slots identical to
the expected voids have been
machined. Typical simulated
notch in aluminium tube
inserted in a FBTR cladding
tube, and the experimental set
up comprising of in-house
developed z-θ scanner, EC
instrument and pancake probe
are shown in Fig.1.
Vertical Output, mV
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
A
Void Size (long x trans)
A-2x3 mm 2
B-1.5x2 mm 2
C-0.8x1 mm 2
B
Frequency: 75 kHz
Gain: 25 dB
-5 -4 -3 -2 -1 0 1
Horizontal Output, mV
C
Typical EC signals from three
simulated voids of 2x3mm 2 ,
1.5x2 mm 2 and 0.8x1 mm 2 at
75 kHz using a pancake probe
are shown in Fig.2. As can be
observed, the 0.8x1 mm 2
notch, which is much smaller
than the specified void size of
1.4x2.1 mm 2 , has produced
unambiguous signal even at a
small gain of 25 dB.
Fig.2 EC signals of simulated voids (notches in aluminium tube)
at 75 kHz.
Fig.3 Eddy current image of 2x3 mm 2 notch simulating void in sodium.
In order to determine the
circumferential location of
voids, the pancake probe has
been attached to the z-θ
scanner and imaging of
simulated notches has been
carried out to develop detailed
test procedure for reliable
detection of voids. Typical
image of 2x3 mm2 notch is
shown in Fig.3. Studies reveal
that it is possible to identify the
location of a void from the
axial and the circumferential
location of the signal/image
feature and also to size it
reliably.
FUEL CYCLE 111