IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
radiation in RCB was 0.3 mR/h,
with a maximum of 1.0 mR/h at
specific locations. A PVC
cocoon was spread over the
pile and hoses provided to
direct the leaking argon to the
exhaust to reduce the activity
inside RCB.
During this experiment the
cover gas was also sampled
and analyzed using Fail Fuel
Localization System (FFLS). The
system performed as per the
design intent and in actual
failure of fuel pin it is expected
to give the age of the failed fuel
pin. Making use of DND
signals, East and West DND
signal ratios and the age of the
failed pin obtained from the
cover gas analysis, the
suspected failed fuel
subassemblies can be short
listed. Actual failed
subassembly can be identified
from this list by limited trial and
error fuel handling and reactor
operations.
I.5. Modification of Trailing Cable System of FBTR to
Minimise Failure of Cores of the Cable
Fuel handling operations in
FBTR are carried out in the
shutdown state of the reactor.
Fuel handling is done through
a single fuel handling canal
which gets aligned over 745
positions of the reactor by
relative rotation of two
eccentrically mounted rotating
plugs, viz. Small Rotating Plug
(SRP) and Large Rotating Plug
(LRP). Prior to plug rotation, the
cables carrying the signals
which are required for reactor
operation, but not for fuel
Fig.1 Original cable routing
handling, are disconnected
with the help of disconnectible
connectors. However, signals
which are essential for fuel
handling are routed through a
trailing cable system.
The trailing cable system
consists of four cables
originating from SRP & LRP.
During plug rotation, these
cables wrap around the LRP
and get wound and unwound in
cable guide grooves on the LRP.
To prevent the cables from
slackening and
to keep them taut
d u r i n g
unwinding, the
other ends of the
cables are
terminated in a
cable tower,
which houses a
set of fixed guide
pulleys at the bottom and a set
of mobile pulleys at the top.
Counter-weights fixed to the
mobile pulleys keep the cables
taut. The pulleys in the cable
tower are in the east-west
plane. Hence, the cables are
routed from the LRP through a
tortuous path, with two acute
turns - one as they come out of
the LRP and the other when they
turn to the east towards the
cable tower (see Fig.1).
Due to the tortuous path with
several turns, the cables were
getting subjected to tensile and
compressive stresses during the
winding and unwinding cycles
respectively. This cyclic loading
was resulting in frequent failure
of cores of cables during fuel
handling. Most of the failures
were taking place when the LRP
positioning angle was between
FAST BREEDER TEST REACTOR 9