IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
one) will align with secondary
coil. At any time atleast one
pick-up coil will be aligned with
secondary coil. The change in
voltage in pick up coil due to
change in position of DSR will
be the indication of DSR
reaching bottom most position.
Further, in order to avoid the
ambiguity as to which pick-up
voltage to be sensed, the sum
of the pick-up outputs is taken
and analyzed to detect DSR
position.
In order to validate the
proposed configuration a 1:1
model was fabricated. Presence
of sodium within the annular
space between the primary and
the secondary side coils is
simulated by 1mm thick
aluminum sheet. The set-up
was tested at various
frequencies from 100Hz to
1000Hz at constant current of
100mA, 200mA and 300mA.
From the test results it is seen
that at 300mA current the
change in pick-up output is
varying from 10-16mV for
various misaligned positions.
Fig. 2 shows the simulated
laboratory test result for change
in pick-up voltage with and
without target when the axial
misalignment is 45mm between
primary and secondary side.
The maximum change for
45mm comes out to be 13mV
which can indicate the position
of DSR.
Thus, from the experimental
results of the simulated sodium
testing, it can be observed that
the proposed configuration is
able to give a measurable
change in pick-up output (10-
16mV) for different misaligned
positions and hence, can be
applied for position detection
of DSR in the fast reactors.
Fig.2 Pick-up output voltage variation
with frequency with 45mm axial
misalignment
III.E.6. Techniques for Assessing Concrete Damage
In the secondary circuits of
Fast Breeder Reactors, if a
sodium spillage occurs on
concrete, sodium - concrete
reaction takes place and the
concrete gets weakened. To
assess the damage, Differential
Thermal Analysis (DTA) and
Fourier Transform Infrared
Spectroscopy (FTIR) techniques
have been adopted. The status
of the sodium interacted
concrete has been evaluated by
studying the change in
Ca(OH) 2 content through DTA
and O-H stretching frequencies
through FTIR techniques. To
study these techniques, blocks
of specially cast limestone
concrete with a square cavity
were exposed to burning liquid
sodium at initial temperature of
873 K for 30 minutes in open
Amount of Ca(OH) 2
(%)
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
10 20 30 40 50
Depth from the interacting surface (mm)
Fig.1 Variation of Ca(OH) 2 content
as a function of depth
air. Samples were collected
from 5 locations of the cavity
floor of the sodium interacted
blocks. From each location 5
samples were taken for every 1
cm depth.
Differential thermal analysis
(DTA) technique
Ca(OH) 2 is one of the
hydration products of Portland
Cement and is in the range of 6
to 7 % in concrete. It
decomposes in the temperature
range 753 to 773 K
endothermically. DTA is a
76 R&D FOR FBRs