The 1986 accident at Chornobyl left a ruined reactor holding 180 metric tons of highly radioactive fuel. To halt the ongoing spread of contamination, workers rushed to enclose the reactor with a 20-story steel and concrete "shelter." Intense radiation and heat made it impossible to build a stable, leak-tight structure.
The 20-story, 300,000-ton concrete and steel shelter was constructed hastily to contain some 180 tons of irradiated fuel.|
The shelter is unstable and could collapse, injuring workers and spreading radioactive dust. The shelter also has cracks and holes. Birds can enter and then spread contamination. More hazardous is the build-up of water from rain and snow. The water not only causes structural corrosion but is turning some of the melted, lava-like fuel into radioactive dust. The dust endangers workers and can escape through the shelter's holes.
Preventing Collapse of the Shelter
The International Shelter Project, in which the United States participates, has developed a "Shelter Implementation Plan" to prevent collapse of the shelter and safely contain the ruined reactor. Ukraine and the G-7 nations approved the Shelter Implementation Plan in June 1997.
The plan describes measures to protect workers and the environment, prevent collapse of the shelter, and construct a new shelter to cover the damaged reactor. The plan also calls for developing strategies for removing the radioactive mass of fuel from the shelter and placing it in safe confinement. The plan does not, however, include the actual removal of the fuel. Technologies are not available yet to move the fuel safely and cost-effectively.
The plan will cost about $760 million to carry out over an eight-year period. That estimate does not include the costs of actual fuel removal or the decommissioning and decontamination of the Chornobyl site.
U.S. and European experts composed the International Shelter Project, and support was provided by Ukrainian institutes, specialists from Russia and the Chornobyl plant, and European and Japanese contractors. The U.S. participants provided the primary technical support and led development of the plan's cost and schedule estimates.
The G-7 selected the European Bank for Reconstruction and Development to manage the project's finances and hire a consultant team to manage the shelter work. In April 1998, Ukraine and the European Bank awarded the management contract to a team comprised of Bechtel National, Inc., Electricité de France, and Battelle Memorial Institute. (Battelle also manages the Pacific Northwest National Laboratory for the U.S. Department of Energy.)
The consultant team is working with Chornobyl managers and staff to provide leadership on technical projects, operations and business programs, licensing, and regulatory strategies.
The team's first technical task is to place contracts for 17 urgent, early-start projects. These "early biddable projects" are combined into four packages. With a projected cost of about $50 million, the projects include the design work for stabilizing the shelter, shielding design, geotechnical and seismic investigations, emergency preparedness, dust management, nuclear criticality monitoring, water management designs, characterization of the fuel mass, strategies for radiological protection and industrial safety, and the development of strategies and technologies for removing and confining the fuel mass. Contracts were awarded the end of July 1998.
The G-7 nations pledged to contribute $300 million toward the $760 million cost. Representatives of 22 countries pledged an additional $37 million during a November 1997 pledging conference in New York City. Ukraine has pledged $50 million worth of in-kind contributions. Leaders of the International Shelter Project have agreed that the total of $387 million is sufficient to initiate work while they seek additional pledges.
The United States also is working with Ukraine to address immediate risks so work to upgrade the shelter can begin. In May 1996, U.S. experts examined working conditions inside the shelter and consulted with Ukrainian officials to identify the most pressing needs for equipment to protect the workers.
More than 800 workers currently conduct shelter surveillance and maintenance. As work at the shelter increases, so will the number of workers and their exposure to radiation and other hazards.
The United States has provided equipment for worker safety in four primary areas: radiation dose reduction, nuclear criticality monitoring, dust suppression, and industrial safety.
Radiation Dose Reduction: Shelter workers will be exposed to significant levels of radiation. They need dosimetry equipment to track the exposure of each individual and protective equipment to reduce their exposure. The radiological protection equipment at the Chornobyl shelter, however, was out of date and in disrepair. Furthermore, there was not enough equipment to protect the number of workers required to stabilize the shelter. The United States has provided up-to-date equipment to track and reduce radiation exposure to shelter workers, including U.S. employees at the site.
The United States supplied air-monitoring equipment, radiation protection clothing, and dosimeters. The United States also supplied software to track worker exposure and to plan work so as to manage the level of exposure to each worker over time.
Nuclear Criticality Monitoring: Hypothetically, water collecting inside the shelter could moderate the neutrons in the melted nuclear fuel, raising the risk of a criticality accident. Monitoring has shown occasional increases in the neutron count rate, raising a question of whether an uncontrolled nuclear chain-reaction might be taking place.
Specialists at the Pacific Northwest National Laboratory built a prototype neutron monitoring system for use inside the shelter. The prototype monitoring system is designed to help determine whether the occasional increased neutron count rate in the shelter is indeed caused by fission reactions. Shelter officials formally accepted the equipment in June 1998. The system consists of eight detector modules, power supplies, and a computerized control and data acquisition system. U.S. specialists provided training in use of the system.
Dust Suppression: Suppression of the radioactive dust inside the shelter is crucial for worker safety. Radiation and chemical changes in the fuel mass continue to turn some of the uranium into radioactive dust. The dust endangers shelter workers and can escape through the structure's holes. Should the shelter collapse, a radioactive dust cloud could endanger workers across the Chornobyl site.
Three types of dust suppression are needed. The Shelter Implementation Plan will address two of these: fixatives to coat highly radioactive material throughout the shelter and emergency dust suppression in case of a shelter collapse.
The United States has addressed the third need: equipment to support radiological cleanliness in the shelter's peripheral areas, such as access ways and staging areas. The U.S. Department of Energy has provided commercially available sprayers and vacuums to clean these relatively uncontaminated areas and keep them clean. These measures will reduce workers' radiation exposure.
Industrial Safety: Industrial safety equipment at the shelter is inadequate to protect workers. The shelter lacks the proper lighting, scaffolding, and tooling to prevent falls and injuries. The shelter needs additional equipment such as gloves, hard hats, and respirators to protect individual workers. Also inadequate are the emergency equipment, monitoring instruments, and communication and surveillance equipment. The United States has provided an array of equipment to address these needs.