A Pioneer’s journey into the Sarcophagus28 February 1998
RedZone Robotics is pioneering the use of remote systems for investigating and assessing the environmental and structural condition of the Chernobyl Sarcophagus, the “shelter” built over the destroyed reactor. RedZone’s development of an inspection robot, called “Pioneer,” will contribute to the Chernobyl Shelter Implementation Plan (SIP), a $750 million international effort to make the site environmentally safe.
In early 1997, RedZone Robotics reached an agreement with the Lawrence Livermore National Laboratory (LLNL), NASA (America’s space agency), the Department of Energy (DOE), and the Chernobyl Nuclear Power Plant (ChNPP) to design and develop a modular, remote inspection system, now known as Pioneer, capable of being deployed into the harsh environment of the Sarcophagus which was hastily constructed over the destroyed unit 4 reactor within six months of the 26 April 1986 accident.
In the decade since the Sarcophagus was completed, concerns about its stability, as well as questions regarding the integrity of the underlying foundation, have been raised by Ukraine as well as many other countries. In fact, between May and November 1996, an international study sponsored by the European Commission under its Tacis Programme, recommended a phased, stepwise approach to remediation. Subsequently, this approach was approved by the G-7 Nuclear Safety Working Group (NSWG) and further developed into the Shelter Implementation Plan in the Spring of 1997.
With technical support from LLNL, Carnegie Mellon University, the National Robotics Engineering Consortium, and Westinghouse Science and Technology Center, and programme support from Pacific Northwest National Laboratory, ChNPP “Shelter” and Interbranch Scientific and Technology Center “Ukraine,” RedZone’s Pioneer will become the first system of its kind to support the Shelter Stabilisation Initiative. Pioneer’s primary objective is to assess shelter conditions – both structural and environmental – to aid in long-term planning. Delivery will take place in late June.
In May 1997, the Pioneer project team conducted extensive meetings with Ukraine members from the ChNPP Shelter and the Interbranch Scientific and Technology Center. Together, members reviewed mission scenarios, Sarcophagus conditions, previous robotics experience, drawings, photographs, and video data, as well as conducted a tour of the Sarcophagus to assess two robots developed and deployed previously by the Ukrainians.
Based on this information, the group designed the integrated system, including a mobility platform and tooling/sensor packages, to have one main function: to serve as a diagnostic tool that will provide a remote structural and environmental assessment inside the Sarcophagus. Structural assessment includes tasks such as:
• Visually surveying structural elements, walls, floors and ceilings for damage, cracking, or other deterioration.
• Taking samples of concrete to determine the physical properties or degradation due to prolonged exposure to high radiation fields and other hostile environmental conditions.
Environmental assessment includes tasks such as:
• Measuring the gamma field intensity and neutron flux.
• Locating and estimating the volumes of fuel containing material (FCM).
A manipulator will also allow Pioneer to place additional, standalone sensors in locations throughout the Sarcophagus to provide additional, longer-term monitoring capability.
MOBILE PLATFORM WITH INTERCHANGEABLE TOOLING/SENSOR PACKAGES
Capable of complete remote operation, the Pioneer utilises a skid-steered tracked mobility platform with the capability to navigate in a harsh, unstructured environment that features slopes, elevations, and objects remaining from the accident.
Able to withstand radiation levels up to 106 R TAD (total accumulated dose), the platform supports tooling/sensor packages, including:
• A coreborer designed to take cylindrical concrete samples from the Sarcophagus walls and floors which will then be analysed to determine the structural properties of the concrete. Pioneer’s coreborer is based upon coring/sampling technology originally developed by NASA.
• A 3D Mapper, also developed by NASA, comprised of both a remote viewing system and a computer/software subsystem; the Mapper provides a colour-textured 3D model of Pioneer’s environment.
• An environmental sensor package that records temperature, humidity, and radiation levels, including gamma field intensity and neutron flux.
• A manipulator that can pick up and move objects; handle separate tooling packages, such as cutting tools; and place additional sensors in various locations.
• A plow bucket to clear away debris to create access for operations.
In addition, a control console provides an operator station where the platform and sensor/tooling packages can be easily controlled, activated, and monitored.
Because Pioneer is modular and light-weight, it can be transported from outside the Sarcophagus to the deployment location by either hand-cart or by hand. In fact, Pioneer is designed to be disassembled for transport, each part weighing < 45 kg and small enough to fit through the Sarcophagus’ 1-metre-wide hallways and stairwells.
Pioneer’s benefits begin with its ability to provide diagnostic information regarding the Sarcophagus’ stability which will be critical to the structure’s stabilisation and future remediation plan. Furthermore, its ability to perform the data collection remotely will reduce the amount of radiation exposure to human workers that would otherwise be necessary. Pioneer will also allow Sarcophagus access where human entry is not favourable due to high radiation fields.
Due to the immediate need for further assessment of Sarcophagus stability, the Pioneer design team’s goal was two fold: to shorten development time to approximately one year and to create a highly-reliable, reduced-risk system. To accomplish this, members based Pioneer on RedZone’s field-tested, remote robotics system, “Houdini.”
A tracked vehicle of similar scale and performance capabilities, Houdini is currently deployed at Oak Ridge National Laboratories in the US where it retrieves nuclear waste from radioactive underground storage tanks. A folding-frame vehicle that fits through a 60-cm-wide opening, the system has been used for a wide range of tasks, including sludge retrieval and core sampling of tank walls. Currently, RedZone is developing second generation Houdini systems for use in other DOE weapons complex cleanup activities.
In creating Pioneer, design team members also relied on the experience they’ve gained from designing and building another RedZone remote system, “Rosie,” a remotely operated, hydraulic-powered mechanical robot with a control system that incorporates custom software and hardware for nuclear facility decontamination and dismantlement. At Argonne National Laboratory, a Rosie system is dismantling the CP-5 experimental reactor. Though radiation levels at the work site have been higher than expected, Rosie has proven to be reliable and flexible. Currently, RedZone has built two Rosie systems, Rosie-O and Rosie-C. Both were funded by the DOE. through the Federal Energy Technology Center (FETC) in Morgantown, West Virginia.