Technical Approach

With broad international financial support, the European Bank for Reconstruction and Development is conducting an eight year, $760 million project to reconstruct the shelter-enclosed Unit 4 of the Chornobyl Nuclear Power Plant, which was destroyed during the world's worst nuclear power plant accident on April 26, 1986. In support of this Chornobyl Shelter stabilization project, DOE and NASA have sponsored a National Laboratory, U.S. industry and university team to design and build a radiation-hardened mobile diagnostic robot dubbed Pioneer. Based on Ukrainian application drivers, Pioneer can characterize the environment inside the Chornobyl Unit-4 Shelter. Operating conditions within the reactor building ­ debris, high radiation fields, and structural instabilities ­ pose extreme health and occupational hazards. As an alternative to human laborers, Pioneer can clear rubble, make maps and acquire samples, advancing the stabilization of Chornobyl while minimizing worker risks.

Pioneer's major components are a teleoperated mobile robot for deploying sensors and sampling payloads; a mapper for creating photorealistic 3D models of the building interior; a drill for cutting and retrieving samples of structural materials; and a set of radiation and environmental sensors.


Mobile Robot

The Pioneer robot is a track-driven machine similar to a small bulldozer that is electrically powered and remotely operated via a 100 meter long umbilical. Tracked locomotion is well suited for driving over and through rubble; the robot's wide footprint provides ample stability and platform capacity to deploy payloads. A six axis manipulator allows positioning of sensors and tools. Intrinsic to the robot is a suite of radiation detectors, temperature probes and humidity sensors, as well as a rad­hardened color video camera for inspection and remote viewing. A ruggedized, portable control console provides the means to operate the robot from safe locations and is connected by a 400 meter cable to five sealed enclosures that house power supplies, control electronics, and the vehicle umbilical termination.

 

Pioneer is based on a predecessor robot, Houdini, developed by the DOE Environmental Mangement Office of Science & Technology to remediate waste storage tanks within the DOE complex. Two Houdini robots are currently in use at Oak Ridge National Laboratory.

 

 

 Houdini

 Pioneer


Photo-Realistic 3D Mapper

  

Pioneer will create 3D digital reconstructions that faithfully capture both the appearance and geometry of the Unit 4 interior using stereo videography. A custom, radiation resistant imager consisting of three black & white cameras with folded optics is deployed on Pioneer's sensor mast and positioned by a pan and tilt unit under computer control. Images that it acquires are processed to generate surface meshes that are texture-mapped with a frame of color video. By merging adjacent meshes, large contiguous 3D maps are generated which can be analyzed by experts outside the Shelter on-site or at remote locations via Internet connections. Because the map is digital, dimensions of and distances between objects in the scene can be estimated. Other data acquired by the robot can be tied into and accessed via the map, creating a 3D database. Pioneer's mapper is derived from stereo vision and 3D rendering developed by NASA for Mars Pathfinder, and modeling software developed by DOE for decommissioning nuclear facilities.


Sampling Drill

One of Pioneer's key capabilities is to assess the structural integrity of the Unit-4 building. A remotely operated concrete sampling drill has been designed to cut and retrieve cylindrical samples of floors and walls that can be subsequently analyzed for strength and brittleness. The drill consists of a linear carriage that thrusts a drill motor and bit into the target structure, and a sensor that measures reaction forces and torques during the coring process. Closed-loop computer control of both thrust and rotation helps to ensure quality of the sample and makes the process automatic. An important by-product of the approach is the ability to estimate material hardness based on the resistance and deflection measured by the drill sensors. Structural information from Pioneer's concrete sampler can be valuable for assessing the building's structural integrity and correlating it to radiation and other environmental parameters. The controller for Pioneer's drill is based on NASA technology for sampling materials on asteroids and comets.