Michael D. Wheeler
Deep inside the Chernobyl nuclear power plant in northeastern Ukraine, the site of the worst nuclear meltdown in history, is a room filled with radioactive slag that has kept man and machine at bay for more than a decade. Now a team of researchers, led by Maynard Holliday of Lawrence Liver-more National Laboratory, has constructed a robot it hopes to send into the abandoned reactor.
Onboard will be the latest in a digital three-dimensional imaging system that will assist the team as the robot -- dubbed Pioneer -- attempts to navigate through the maze of rooms deep inside the reactor. The system features three radiation-hardened charge-coupled device (CCD) cameras manufactured by Hitachi Denshi Ltd. and designed to withstand the 1000 rads per hour typical of Chernobyl. These cameras will take a series of black-and-white still photos and transmit them for processing through a 100-m tether attached to Pioneer. Software will provide coordinates for 3-D mapping of the rooms.
If the imaging system proves effective, it may find a place on NASA's Mars 2000 mission.
Before deciding on the components of the imaging system, engineers had to weigh a number of options. They considered laser scanners, radar sensors and structured light rangers -- but all required onboard electronics that would be adversely affected by high levels of radiation. CCD cameras operate passively, require little power and allow off-board processing, making them a suitable choice. The team also considered using radiation-hardened cameras from Cidtec, a subsidiary of Thermo Vision Corp. based in Liverpool, N.Y. However, according to Mark Maimone of NASA's Jet Propulsion Laboratory, the electronics required for the Cidtec camera would have been too bulky.
To protect the Hitachi cameras from radiation, engineers encased them in lead shielding and used a lead-lined mirror to minimize direct exposure of the camera lens.
Off-the-shelf technology
Like many other components that are aboard the robot -- which resembles a bulldozer and is the size of a large desk -- the imaging system was designed using mostly off-the-shelf technology. That enabled the team to keep the project within its $2.7 million budget. That did not mean the engineers cut any corners, however.
"Everything has to be thought out very carefully -- from the type of camera and its hardness to the shielding it required," said Holliday.
Ukrainian scientists have agreed to pick up Pioneer in its completed form in the fall. First, Pioneer will run through a mock-up of the Chernobyl reactor, possibly as soon as this month. Provided the simulation goes according to plan, Pioneer may be plumbing the depths of Chernobyl by early 1999.