f '•:, ..• ;ffi; ,.:«•' . ;K: ..X: ..'. '&.: • . •%l^.;;:^-'«i;^li'̂ li"i^Si«y;Sli;ra.'§.i{|(-«i^&i-.!?iC:iat iW:,X-':Sj.:: xS- : • •.»;•- :!;;;*;.

For some decades now, automation and robots havebeen used with success in various forms for industrialhandling, assembly, and manipulation jobs. In thenuclear industry, a wide range.of specialized manipulatorsand equipment have been, and continue to be, developedto perform remote tasks such as inspection, maintenance,repair, and refurbishment.

The use of such devices is one important way ofreducing human exposure to radiation during decommis-sioning and decontamination operations at nuclearfacilities. Consequently, decommissioning costs alsomay be reduced.

What is meant by the terms "robot" and "manipulator"?Within the context described here, a robot is a pro-

grammable handling machine that has a memory, can betrained, and can be retrained easily when changed to anew job. This latter capability is the characteristicdifference between robots and other pieces of automatedequipment, although the flexibility of numericallycontrolled equipment is also high. Robots basicallyconsist of mechanical components, actuators, controls,and sensors, and generally have many degrees of freedom.

A manipulator, on the other hand, has many featuresof a robot, but it is usually operated directly under someform of manual control, which may be remote. Pro-grammed control of a manipulator can be accomplished(producing a form of robot), just as manual control of arobot is possible through an appropriate control system.

For decommissioning and decontamination work,the following components are important for both robotand manipulator applications:

Task analysisRemote control technologyAdvanced mechanical engineeringSimulation technologyRemote sensing equipmentMan-machine interface.

Programmes in the nuclear industry

In the nuclear industry, remotely operated equipmenthas been used for handling, inspection, dismantling,assembly, repair, replacement, and fabrication tasks in

reactors, shielded cell facilities, underwater bays, repro-cessing plants, fuel fabrication plants, and radioisotopeproduction facilities, for example.

Of most interest from a decommissioning viewpointare the remotely operated manipulators, robots (stationaryand mobile), the visual and sensor technology, and thecomputer hardware and software associated withthe equipment.

The types of manipulators in use include relativelysimple master/slave manipulators, sophisticated bilateralforce-reflecting electric manipulators (in which themaster and slave can be connected by direct wire, radio,or laser beam) and the most advanced and dexterouscomputer-aided master/slave servomanipulators. Inaddition, industrial manipulators can be equipped withenvironmentally conditioned and shielded cabenclosures and mounted on vehicles if necessary.

Automatically guided vehicle systems have been usedin industry for many years for a variety of tasks. Some,are free-ranging with optical or radio-controlled guidancesystems while others follow guidance wires installedunder the floor. Specialized track and wheel vehicleshave been developed for the nuclear industry as well.For decommissioning, such vehicles may be used asmobile bases for carrying manipulator arms and equip-ment to do work in areas having high radiation fields. Astudy detailing the options for decommissioning hasbeen completed for the Commission of the EuropeanCommunities (CEC).*

These general purpose mobile robots can advantageouslyreplace man for multiple tasks such as surveying andmonitoring. Physical measurements are possible (forexample, of radiation levels, temperature, humidity) aswell as scabbling and decontaminating walls and floors.The load capacity of the vehicle-borne manipulatorsdetermines the extent to which small compacts can bedisassembled and other tasks, such as1 building shieldingwalls, can be achieved.

The remote technique can be extended to largervehicles such as bulldozers, backhoes, and^excavators .required for mass concrete demolition. Radio-controlledsystems that operate control levers on these'machinesare commercially available.

This article has been adapted from The Methodology and Techno-logy of Decommissioning Nuclear Facilities, IAEA TechnicalReport (in press). For related articles, see the IAEA Bulletin,Vol.27, No.3 (Autumn 1985).

* See "Review of Systems for Remotely Controlled Decom-missioning Operations", by L. Da Costa et al., Commission ofthe European Communities (in press 1985).

IAEA BULLETIN, WINTER 1985 35

Decommissioning nuclear facilities

Robotic arm for use in decommissioning activities.

(Credit: Cincinnati Milacron)

At TMI-2, workers check "Rover",a robot that made the first extensivepost-accident examination of thereactor building basement. (Credit:GPU Nuclear)

For underwater use. manipulators mounted on sub-mersibles are available, and similar ones can be envisagedfor underwater nuclear decommissioning applications.However, this would require significant development.

In France, a sophisticated servomanipulator equippedwith television and telescopic supports with computercontrol has been developed and is being used for remotemaintenance and decommissioning tasks. The com-bination of options permits the arm to be operatedeither as a manually controlled maintenance manipulatoror as a computer-controlled robot.

In Canada, a sophisticated remote manipulator sub-system (RMS) is being developed by SPAR Aerospace forOntario Hydro for possible use in the retubing of

Pickering reactors. It uses technology developed bySPAR for the arm used on the US space shuttle vehicles.The RMS is one part of a co-ordinated Remote Mani-pulator and Control System that will be used for a varietyof handling, inspection, support, and transport activities,as well as maneuvering containers in the fuelling machinevault . In another project, Atomic Energy of CanadaLimited has developed a complex remotely controlledarm with a viewing system and a remote welding machineto repair leaking pipes located in a vault below theDouglas Point nuclear reactor.

In Japan, a comprehensive programme is in progressto develop a robotic remote handling system for thedecommissioning of the 90 megawatt ( t h e r m a l ) power

36 IAEA BULLETIN, WINTER 1985

Decommissioning nuclear facilities

»Removal of circumferential machinery»Removal of reactor internals

• Removal of reactor pressure vessel• Removal of remaining machinery

Containment vessel

\

Shield concrete

Pressure vessel\,

Reactor internals'\

Air lock

Removal of reactor containmentvessel and concrete

In Japan, the first reactor to have generated electricity will also be the first one decommissioned. Called the JPDR (forJapanese power demonstration reactor), the plant began operations in 1963, was shut down in 1976, and now is scheduledto be dismantled by the end of this decade. The diagram shows the tentative procedure envisioned for taking apart theboiling-water reactor. The decommissioning project is being conducted by the Japan Atomic Energy Research Institute(JAERI). (Credit: Science & Technology in Japan. Vol.4, No.16, Three "I" Publications, Ltd.)

demonstration reactor (JPDR). During the first part ofthe study, emphasis is being placed on the developmentof man-machine interfaces and advanced control systemsto improve ease of operation, flexibility, dexterity, andautonomy. Features such as semi-automatic trajectorycontrol and collision avoidance for vehicle andmanipulator will be developed. Based on this work,light- and heavy-duty remote handling systems equippedwith underwater power manipulators capable ofhandling 10 and 100 kilograms, respectively, will beavailable by the end of 1986.

In the United Kingdom, the Atomic Energy Authorityis developing sophisticated remotely operated equipmentfor the decommissioning of the 33-megawatt Windscale

advanced gas-cooled reactor (WAGR), scheduled forcompletion by 1994. In concept, the decommissioningmachine system consists of a shielded gantry supportingan extendable rigid mast, and an elevating platformholding a remotely operated manipulator that will beused to perform the dexterous activities associated withdismantling. Remotely operated plasma-arc cutting andstereo TV systems are being investigated for use withthe decommissioning machine in dismantling the reactorand removing the waste.

In the Federal Republic of Germany, similar auto-mated or remotely operated dismantling and handlingequipment is being developed for the decommissioningof the 100-megawatt Niederaichbach (KKN) gas-cooled

IAEA BULLETIN, WINTER 1985 37

Decommissioning nuclear facilities

pressure tube reactor. The reactor will be dismantled,segmented, and packaged by remote operation using arotary manipulator, a cutting manipulator, and a cranemanipulator.

The principles developed at WAGR and KKNcan be applied to the design of manipulators for use inthe decommissioning of other pressure vessels.

Criteria for remote operations equipment

The use of remotely operated equipment in thenuclear industry implies that it will be operated in ahostile environment in which it may get contaminated.Also, human access to the equipment for adjustments,repairs and/or replacement is often difficult or hazardousand cannot be done until the unit has been decon-taminated.

In designing or selecting remotely operated equipmentfor use in decommissioning tasks, the performance of theequipment should be carefully considered. Criteria thatshould be followed wherever possible include:• Performance of the machine even under fault con-ditions must be fail safe.• The machine must be reliable, durable, and able tocomplete the appointed task.• Human access to the machine, although often restricted,must be sufficient for deployment, operation, and

retrieval. The machine design should also enable easymaintenance, repair, and dismantling.• When used in contaminated conditions, the machinemust be designed to allow easy decontamination.

• The life-cycle cost should be calculated to includedecontamination and/or disposal of the machine.

• The man-machine interface must be considered in thecontrol of the machine to ensure that the operator'sperformance is not impaired.

• The machine should be extensively tested in mock-upfacilities before it is committed to the actual task.• Connectors and fasteners should be designed foroperation under remote conditions when necessary.• Components should be radiation tolerant; controlsand as many other components as possible should bedesigned to remain separate from, and outside of, theactive zone.• The operational environmental conditions (such astemperature, pressure, humidity, dust, chemical activity)should be considered in the design.

• Where practical, available and proven industrial com-ponents and/or units should be used, even if minormodification is required.

• The design should be as simple as possible, but stillachieve the foregoing criteria.

Industrial robots: Various types for multiple uses

The kinematic functions of industrial robots usually areevaluated by comparison with the original "multipurposemanipulator" — the human arm and hand — and mostrobots are designed to try and duplicate man's capabilities.Many have an articulated mechanical arm onto whichvarious devices such as a gripper, grinder, paint sprayer,welding gun, or pneumatic wrench can be attached. Thedesign and operation of these devices (called "end-effectors") — which take the place of the human hand —are as important as the design of the robotic arm itself.

The human arm and wrist — in addition to spatialcontrol — can re-orient an object through three planes ofrotation giving a total of six degrees of freedom (threetranslational axes and three rotational axes). The humanhand itself has 22 separate movements. When combinedwith human sensory functions, the feedback system, andthe ability of the human brain to automatically select thesensory feedback most appropriate to every moment, thehuman arm is a very versatile and complex mechanism. Itis also very strong ( a strength to weight ratio of about 5)and lightweight.

To simulate the spatial and re-orientation functions ofthe human arm and wrist, a robotic arm or manipulatormust have at least six degrees of freedom. Often as manyas eight or nine degrees of freedom are used to permit therobotic arms to reach around obstacles. In most cases,the 22 movements of the human hand are replaced witha simple pincer device, although in very special cases

anthromorphic hands with articulated and powered fingershave been developed.

The actuators of a robot can be operated pneumatically,hydraulically, electrically, mechanically or in some com-bination of the four basic drives.

The most difficult task in developing a robotic arm isto simulate the control functions of the human arm. Thedevelopment of specialized computers, processors, andmemories has ushered in a new phase for robotic control.The designer can increase the intelligence of the robot byusing mathematical equations for complex motions andmore complicated sensory devices.

The design of the robots and control systems currentlyin use vary widely and range from simple limited-sequencerobots to sophisticated computer-controlled robots.

Many thousands of limited-sequence robots — mainlyof the "pick and place" type — are being used successfullyin factories throughout the world. These robots onlyrequire a limited number of sequential actions to do theirjob and do not require the control of motion of moresophisticated robots. Each step of the operations sequenceis pre-programmed and controlled by an electric orpneumatic signal from a plugboard control panel.Mechanical stops are generally used to limit the motion ofeach joint. Although most devices have no ability to getfeedback from their working environment, some havebeen combined with other devices to permit someintelligence. The technology associated with limited

38 IAEA BULLETIN, WINTER 1985

Decommissioning nuclear facilities

sequence robots would not appear to have much applic-ation in decommissioning and decontamination work,since the robots are relatively difficult to re-program.

In more sophisticated commercial robots, one of themost important components is the control system whichdictates when and how the robotic hardware will performits tasks. The control system, which consists of a com-puter, a high capacity memory and sensory feedback,must have simple and fast on- and off-line programmingabilities. Additionally, it must be capable of interactingwith an operator and with feedback from as many sensorsas are required to do the job. Sensors permit themeasurement of the system's state in real time and canprovide feedback to the controls. Typical ones are laserrange finders, television systems, tactile, force, torque, andproximity sensors. Computers store input data andcomplex programs for the robot, compare the measuredand desired performance, generate complex sequences ofdesired outputs and permit communication between ahuman and the complex robot.

Software technology

Just as important as the robotic hardware and controlsis the new software technology being developed. Forexample, interactive computer graphics systems couldpermit the automation engineer to put the roboticallyoperated equipment through its paces on a computerscreen rather than through "trial and error" in a highlyradioactive environment. This means that the engineercan feed into the graphics computer the design andlocation of the piping, equipment, and the surroundingfacility, for example. The robot and its working tool alsocan be pre-programmed before installation.

For example, if a series of pipes of various sizes andshapes have to be cut, a robot mounted on a mobileremote-controlled vehicle, a crane, or a gantry, and havinga cutting torch as an end-effector could be pre-programmedto cut through the pipes in the right sequence. Collisionavoidance should be achieved by using sensors or thesoftware model of the environment derived from thegraphics system. This type of technology would appearto be well worth developing for decommissioning anddecontamination, as well as for maintenance, using eithersophisticated robots or more conventional kinds of remotesystem technology combined with various tools.

Advanced robotic systems, which are being used in awide range of factories for welding, foundry applications,spray painting, delicate assembly jobs, etc., will relievemany workers of dangerous and unpleasant tasks. Directapplication of specific industrial robotic systems todecontamination and decommissioning tasks in thenuclear industry depends on activity and contaminationlevels. However, application of the technology, com-ponents and specific robots is feasible and desirable formany tasks. It must be kept in mind that robots having

Using its "arms and hands" this robotic system can griptools and pick up small objects. (Credit: ACEC)

force, touch, and visual sensory capability are availablebut are still under development; even modest maintenancetasks challenge current robotic technology.

Robotic systems work best when the co-ordinates ofthe physical environment surrounding them are welldefined and within the robot's memory. Continuedinvestment in artificial intelligence research and develop-ment and the establishment of interface standards whichare common to all robot suppliers will increase theflexibility of future robot applications.

In evaluating the financial attractiveness of applyingrobotic technology to any activity, conventional return-on-investment and payback calculation methods shouldnot be applied. In addition to the standard savings of thesalaries of workers displaced by the robotic system, othersavings include the cost of items such as health insurance,less supervision, no parking space, less training, heat,light and power, no pension, sick leave, or man-rem costs,etc. A cost/benefit analysis technique has been esta-blished to allow comparison of the cost of roboticapplications to nuclear facility inspection.

IAEA BULLETIN, WINTER 1985 39