IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
IV.A.6. Dismantling and Metrology of FBTR FSA
and Fuel Pins after 155 GWd/t Burn-up
A new computer controlled
Dimensional-Measurementscum-Laser-Dismantling
(DMLD)
machine was developed and
installed inside the hot cells to
carry out remote metrology and
laser based dismantling of high
burn-up FBTR fuel
subassemblies (FSA). The
machine consists of a
mechanical system located
within the hot cell, and the
associated motion control
system and laser system located
outside the hot cell. Fig.1
shows photographs of the four
axis mechanical system of the
machine.
High level of gamma
radiation, deformed nature of
the FSA and the requirement of
high level of measurement
accuracy provided immense
challenges in developing this
machine especially for remote
operation and maintenance.
Laser-based cutting was
adopted due to its favorable
features such as fast and noncontact
nature of cutting,
absence of moving parts, ease
of remote operation, minimum
remote repair/replacement of
parts, absence of coolant and
minimum generation of waste
such as dust, chips etc.
However challenges were
involved in delivering the
required laser power precisely
at the cutting location with
optimized parameters and
avoiding welding between the
outer and inner hexagonal
sheaths of FSA during cutting.
Precise dimensional
measurement of the FSA is
required to assess whether the
incremental deformations due
to irradiation is likely to pose
any constraints in the fuel
handling operations, and
thereby limit the burn-up of the
fuel. The DMLD machine make
use of an induction type touch
trigger sensor mounted on the
YZ- stage and a custom- made
motion control software for
dimensional measurements of
the FSA. The machine
automatically acquires the
coordinates of large number of
surface points at various cross
sections along the length of the
FSA through automatic
scanning as defined by the user.
These cross-sections of the FSA
are reconstructed by plotting
this data in the 2D drafting
environment of CAD software.
The width-across-flat and
corner-to-corner distance of
various cross sections are
(a) Outside hot cell
(b) Inside hot cell
Fig.1 Photographs of the mechanical system of the DMLD machine
88 FUEL CYCLE