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ROBOTS IN RADIOACTIVE ENVIRONMENTS. INTRODUCTION. In a critical place such as a nuclear power plant , where the manual work is quite difficult the application of robots are really worth mentioning. Robots are used to prevent exposure of humans to radiations in Nuclear Power plants. CONCEPT.
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ROBOTS IN RADIOACTIVE ENVIRONMENTS
INTRODUCTION • In a critical place such as a nuclear power plant , where the manual work is quite difficult the application of robots are really worth mentioning. • Robots are used to prevent exposure of humans to radiations in Nuclear Power plants
CONCEPT • Webster’s dictionary definition “An automatic device that performs functions ordinarily described to human beings” • Robotic Institute of America definition “It is a reprogrammable multifunctional manipulator designed to move materials, parts, tools etc through variable programmed motion of the performance of a variety of tasks
CONTENTS • Minimize human exposure • Maintenance activities • Steam Generators • Tele-operation platform • End effectors • Remove fallen objects in • primary circuit nozzle • PWR reactor vessel
MINIMIZE HUMAN EXPOSURE • Risk of contamination which is accidental • Irradiation affects operators work areas • Professional workers are few in number and require years of experience • International laws exist which limit the max exposure rate of workers • Reduce working time and increase maintenance cost
PREVENTIVE MAINTENANCE AND UNFORSEEN INCIDENTS • Periodic maintenance require • Careful preparation • Safety • Well known working environment • Prepared using a full scale mockup • For telerobotics there is • Geometric model of the remote site • Mission is programmed • Operates in supervision mode
WHAT IS THE NEED OF ROBOTS IN STEAM GENERATORS ? • Steam Generators use U bent tubes. U bent tubes in WSG made using inconel alloy to ensure High thermal efficiency of heat exchanger • Multiple stresses • Mechanical and thermal loading vibrations & corrosion • Maintenance jobs during plant refueling are complex • Water cleaning, nozzle dam insertion etc.
ROSA NOZZLE DAM INSERTION ROSA in proximity to the nozzle dam, positioning gripper to remove it • Remote user interface • Control six axis arm
Arm base is attached to tube sheets by means of four hydraulic cam locks • Arm is equipped with a remote quick connector to facilitate the assembly and disassembly of such tools
TELEOPERATION PLATFORM • New platform developed using Hewlett Packard UX operating system • Local area network connects with teleoperation platform with robot control unit • Graphic models of arm, loader, tube sheet & channel head was developed using ROBCAD
The Sequence of observation made by the operator when robot is loaded at tube sheet of SG • Critical & Needs careful programming • Arm should be manually inserted in the channel head through a narrow man way
One inside the RQC is attached to a loader • Hence the cinematic tree is inverted • Operator moves the loader • Arm should perform a predefined motion scheme
After last motion the arm base should be • perfectly aligned with the tube sheet • Operator moves the base until the camlocks are inside the anchor tubes and expand them
END EFFECTORS • Develop tools that could operate on tube sheets of SG • Operations include • Detecting wrong tubes • Canceling wrong tubes • Recovering them • Drilling plugs • Placing the nozzle dams
ELECTRO DISINTEGRATION MACHINE • To disintegrate foreign elements located in the tubesheet
PARTS OF EDM • Remote Quick Connector (RQC) to attach to robot end, a fixed platform where vision are installed
CONTD…. • Potentiometer for alignment with the tubesheet & Camlocks for anchoring to it • Commands are provided to fit & activate EDH, to fit intensity and voltage parameters and to load and unload the tool
REMOVAL OF FALLEN OBJECTS IN PRIMARY CKT NOZZLE • Objects may fall inside primary nozzle during maintenance operation, if dam not installed • Necessary to develop special tools. • Tools are handled by jumpers from channel head nozzle so accumulated doses are high
INSPECTION & RETRIEVING VEHICLE • It is highly robust & fail safe.
REMOVAL OF FALLEN OBJECTS INSIDE PWR VESSEL • Parts of tools may fall inside vessel during refuelling because of human error
Teleoperated and robotized • system for maintenance • operation in nuclear • powerplant vessels • (TRON) is a four joint of • robotised pole • Used to retrieve fallen objects • from the PWR reactor vessel • It comprises jointed pole, end • effectors & computer vision • navigation system
APPLICATIONS • STEAM GENERATORS: • Primary tube inspection & maintenance. • Channel head cleaning . • Nozzle dam insertion. • REACTOR CAVITY: • Fuel transfer channel cleaning & underwater inspection. • REACTOR VESSEL: • Underwater inspection & repair. • Foreign fallen object removal.
CONCLUSION With improving technology & growing perception of the need to keep human workers away from high radiation areas, more competitive robotic systems are increasingly becoming available