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Remote Handling Technology in Nuclear Industry
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Transcript of Remote Handling Technology in Nuclear Industry
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8/9/2019 Remote Handling Technology in Nuclear Industry
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22 MODERN MANUFACTURING INDIA - MAY 2013
MAIN FEATURE
Radioisotopes are used in the areas of power production, health care, industry,
agriculture, food preservation, etc. Due to their potential health hazards, high-active
isotopes are handled remotely using remote handling devices. This article describes
general-purpose remote handling devices developed by Bhabha Atomic Research Centre.
Remote Handling Technologyin Nuclear Industry
In India, the program ‘Isotopes and
Radiation for Betterment of Humankind’
was initiated more than fifty years ago by
Dr Homi Jahangir Bhabha, the father of
energy in the form of radiation. They may
emit alpha particles, beta particles or
gamma rays. In addition to the above, a
nuclear facility may also have neutron
radiations, which are emitted from neutron
sources or the core of nuclear reactors.
These ionizing radiations have varying
penetrating powers and can be a health
hazard in varying forms.
Radiation protectionOccupational workers have to be protected
from ionizing radiations to eliminate the
possibility of health hazards. Radiation
exposure can be minimized by controlling
the following three factors:
▶ Time
Reducing the time of exposure reduces
the effective dose proportionally
▶ Distance
Dose is inversely proportional to the
square of the distance to the source
▶ Shielding
Placing a radiation absorbing material
between the operator and the source
will reduce the dose
K Jayarajan, FNAEHead, Tele-Manipulator SectionDivision of Remote Handling and RoboticsBhabha Atomic Research Centre, [email protected]
Remote handling tools enable an operator to
perform a task in a hazardous environment,
while remaining at a safe distance from the
task area
S o u r c e : B A R C / C H R I S T
I A N D A R K I N / S C I E N C E P H O T O
L I B R A R Y
India’s Atomic Energy Program. While the
isotopes of Uranium, Plutonium and
Thorium are used for power production,
radioisotopes produced in nuclear reactors
are used in a variety of applications,
including agriculture, food preservation,
water resource management and many
others. They are also used for diagnosis and
treatment of cancer.
Radioisotopes are atoms with unstable
nuclei, which may stabilize by releasing
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MODERN MANUFACTURING INDIA - MAY 2013 23
MAIN FEATURE
In India, the dose limits for occupational
worker and public are governed by the
regulations of Atomic Energy Regulatory
Board (AERB). In addition to the regulatory
requirements, the As Low As Reasonably
Achievable (ALARA) principle is followed
in designing and operating radiation
facilities for further reducing the dose.
Radioisotope handling
High-active isotopes are handled in nuclear
facilities for power production, fuel
reprocessing, nuclear waste management,
post irradiation examination, radioisotope
production, decommissioning, etc. Alpha-
emitting isotopes are handled in sealed
containers, called glove boxes, whereas
gamma-emitting isotopes are handled in
heavily shielded rooms, called hot cells. To
prevent leakage of contamination, the
outgoing air is filtered using high-efficiency
particulate air (HEPA) filters. Also, the air
pressure in the cell is maintained below that
of outside air. Usually, radiation shielding
windows (RSWs) are provided on the
shielded cell walls to get the view of cell
interior. RSWs shield gamma rays, but
allow visible light to pass through. As the
entry of human operator is restricted in hot
cells, objects in these cells can only behandled using remote handling devices.
Remote handling tools
Remote handling tools enable an operatorto perform a task in a hazardousenvironment, while remaining at a safe
distance from the task area. A goodremote handling device should be capable
of quickly performing the job at a distance
or behind a shielding. Remote handling
strategy depends on the risk, complexity
and the frequency of operation of thetask. Automation can be adopted forrepetitive tasks in a structured area.However, unstructured tasks requiredexterous human intervention in real-time.
Designing a device for radioactiveenvironments has many challenges. Many
common materials and most of the
conventional electric and electronic
components have a short life in high
radiation. The device has to be designed for
remote maintenance and should be capable
of withdrawing from the remote area, if
necessary. The components should not get
damaged, when they are washed with water
or mild acids for decontamination.
Bhabha Atomic Research Centre (BARC)
has developed many types of multi-purpose
remote handling devices, including Remote
handling tongs, Mechanical master slave
manipulators, Servo manipulators, Power
manipulators and Autonomous vehicles. A
few of them are described here.
Master slave manipulators
Master slave manipulators (MSMs) are the
most widely used remote handling tools in
the nuclear industry. They can reproduce
the natural motions of human in 1:1 ratio,
on a gripper located in the remote hot cell.In master slave manipulation, the human
being is within the process; his manipulative,
sensory and decision-making capabilities
are extended to the remote site.
The tool has two arms, a master arm in the
operating area and a slave arm in the remote
site. The master arm has a handgrip and the
slave arm has a gripper at their free ends.
When the operator holds the master handgrip
and moves it along the desired path, the slave
gripper reproduces the motion in the remote
hot cell. The force and torque applied by theoperator also gets reproduced on the slave
gripper. The operator can get visual feedback
of the hot cell, through the RSW (viewing
window) or CCTV cameras.
S o u r c e : B h a b h a A t o m i c R e s e a r c h C e n t r e Remote handling experience in
nuclear industry has been useful
elsewhere also. At the Ordnance
Factory Khamaria, Jabalpur, about300 ammunition boxes, containing
anti-tank mine fuzes, were lying in
two rooms for more than 25 years.
The fuzes, being highly explosive,
were threat to the factory and the
surroundings. BARC has developed
a remote handling system
consisting of a vehicle, a
manipulator and a box-handling
device. Using the system, the fuzes
were safely taken out from the
rooms, transported to a remote
site and disposed successfully.
Explosive disposal system
S o u r c e : B h a b h a
A t o m i c R e s e a r c h C e n t r e
Four-piece servo manipulator. The modular manipulator can be installed in any type of hot cells.
Slave Arm
MasterHandgrip
MasterArm
MotorAssembly
Through-Tube
Slave Gripper
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24 MODERN MANUFACTURING INDIA - MAY 2013
MAIN FEATURE
Like a human arm or a robot manipulator,
the slave arm of an MSM consists of a series
of links connected together through joints.
Usually, the arms would have minimum six
joints for arbitrarily positioning the gripper.
It may be noted that for specifying theconfiguration of an object in space, six
variables are necessary: three for position
and three for orientation. All joints are
controlled synchronously to achieve the
desired gripper trajectory.
Depending upon the power source of the
slave arm, MSMs are classified into
Mechanical MSMs and Electrical MSMs
(Servo Manipulators).
Mechanical master slavemanipulators
In a mechanical MSM, the master arm and
the slave arm are mechanically coupled
through a through-tube in the cell wall.
Required power for the remote operation
in the hot cell is supplied by a human
operator himself standing outside. A
mechanical MSM is a multi-degree-of-
freedom mechanism, with six manually
powered joints and a gripper. Sometimes,
at most three electrically powered joints are
provided to increase the range of the slave
arm and to improve the operator’s comfort.
An MSM may be of articulate type ortelescopic type. While all joints of the former
are of revolute type, the later would have at
least one prismatic joint. BARC has
developed a variety of mechanical MSMs
with varying reach (1 m to 3.4 m) and
varying payload (4.5 kg to 45 kg). They use
various mechanisms to convert the
operator’s hand movements in the operating
area into the movement of the slave gripper
in the hot cell. The joints are counter-balanced to reduce the operator’s effort.
Servo manipulators
The slave joints of servo manipulators are
powered by external power sources such as
electric motors or hydraulic actuators.
External power sources reduce operator’s
efforts. Moreover, the force that can be
applied by the slave arm is not limited by
the strength of the operator.
In servo manipulators, the master arm
and the slave arm are connected through
electric cables or by wireless communication.
This provides flexibility of mounting the
slave arm on a transporter, like a vehicle or
a crane. As this would enhance its range, one
pair of servo manipulator could serve a hot
cell of any size. The servo manipulator can
approach hot cell equipment from arbitrary
directions. It provides flexibility in design of
the equipment and the layout of hot cell.
Servo manipulator technology is a multi-
disciplinary field, similar to that of robotics.
It requires expertise in various areas like,
mechanical, electrical, electronics, controlsystem, software, nuclear and ergonomics.
Advanced technologies
BARC has been actively involved in
enhancing the quality of tele-operation. The
major research activities in this area include
telepresence and telerobotic technologies:
Telepresence
For fast and accurate tele-operation, the
operator should feel that he is present at the
remote site and is handling the objects
directly with his own hand. A telepresence
system consists of operator’s site and remote
site, equipped with effectors and sensors.
The operator’s site is equipped with visual,
hearing and haptic (touch) interfaces. The
remote site contains the slave manipulator,
camera and various sensors, with
information traveling between the user and
the remote location. Although, sensing
touch or force is inherent in a mechanical
MSM, they have to be artificially created in
a Servo manipulator. Stereo image isrequired for depth perception of the remote
site. A computer mouse can position the
curser on a 2-dimensional screen. However,
object manipulation in 3-dimension requires
simultaneous control of six variables.
Therefore, a master arm with six joints is
used as input device for tele-operation.
Tele-robotics
While robots are autonomous devices
capable of repetitive handling in structured
environments, MSMs are versatile devicessuitable for unplanned handling in
unstructured environment. A telerobot
combines both these capabilities- it can work
S o u r c e : B h a b h a A t o m i c R e s e a r c h C e n t r e
MSM Laboratory of BARC. BARC has developed about ten models of MSMs with varying payloads,
reaches and other features.
S o u r c e : B h a
b h a A t o m i c R e s e a r c h C e n t r e
Suspendable servo manipulator for emergency
operations: It can be attached to the hook of a
crane and taken to the site for remote operations.
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MODERN MANUFACTURING INDIA - MAY 2013 25
MAIN FEATURE
S o u r c e : B h a b h a A t o m i c R e s e a r c h C e n t r e
Advanced servo manipulator has force control capabilities. Also the operator can feel the force
acting on the remote gripper. These features are useful for safe handling of delicate objects.
as an MSM as well as a robot. Telerobots can
play a major role in hot cell automation, such
as in advanced fuel fabrication. Advanced
servo manipulators developed by BARC are
capable of operating as telerobot.
Conclusion
Radiation protection has been one of the
priority areas of the Department of Atomic
Energy (DAE). Identifying its importance,
DAE had initiated the development of
remote handling tools long ago. It has
successfully developed a variety of tools for
operations in radiation environments and
installed them at various nuclear facilities.
These tools virtually extend the operator’s
hand to a remote site and perform a variety
of jobs—from operation of small instruments
to the maintenance of large process
equipment. Telerobots are being developedto augment the versatility of human-assisted
tools with the autonomy of robots. MMI