HYDROLASING OF CONTAMINATED UNDERWATER BASIN SURFACES AT THE HANFORD K AREA

摘要

This paper discusses selecting and implementing hydrolasing technology to reduce radioactive contamination in preparing to dispose of the K Basins; two highly contaminated concrete basins at the Hanford Site. A large collection of spent nuclear fuel stored for many years underwater at the K Basins has been removed to stable, dry, safe storage. Remediation activities have begun for the remaining highly contaminated water, sludge, and concrete basin structures. Hydrolasing will be used to decontaminate and prepare the basin structures for disposal. The U. S. Department of Energy's (DOE) Hanford Site is considered the world's largest environmental cleanup project. The site covers 1,517 Km~2 (586 square miles) along the Columbia River in an arid region of the northwest United States (U.S.). Hanford is the largest of the U.S. former nuclear defense production sites. From the World War II era of the mid-1940s until the late-1980s when production stopped, Hanford produced 60 percent of the plutonium for nuclear defense and, as a consequence, produced a significant amount of environmental pollution now being addressed. Spent nuclear fuel was among the major challenges for DOE's environmental cleanup mission at Hanford. The end of production left Hanford with about 105,000 irradiated, solid uranium metal fuel assemblies - representing approximately 2,100 metric tons (80 percent of DOE's spent nuclear fuel). The fuel was ultimately stored in the K Basins water-filled, concrete basins attached to Hanford's K East (KE) and K West (KW) reactors. K Basin's fuel accounted for 95 percent of the total radioactivity in Hanford's former reactor production areas. Located about 457 meters (500 yards) from the Columbia River, the K Basins are two indoor, rectangular structures of reinforced concrete; each filled with more than 3.8 million liters (one million gallons) of water that has become highly contaminated with long-lived radionuclides. At the KW Basin, fuel was packaged and sealed in canisters. At the KE Basin, fuel was stored in open canisters that were exposed to water in the basin. The irradiated spent nuclear fuel corroded during long-term, wet storage; resulting in thousands of fuel assemblies becoming severely corroded and/or damaged. Corrosion, especially in the KE Basin, contributed to the formation of a layer of radioactive sludge in the basins. Sludge removal is now progressing and will be followed by dewatering and dispositioning the concrete structures. The DOE Richland Operations Office (RL) has given Fluor Hanford Inc./Fluor Government Group (Fluor) the task of preparing Hanford's K Basins for decontamination and disposal. Prior to dewatering, hydrolasing will be used to decontaminate the basin surfaces to prepare them for disposal. By removing highly contaminated surface layers of concrete, hydrolasing will be used to meet the dose objectives for protecting workers and complying with regulations for transporting demolition debris. Fluor has innovated, tested, and planned the application of the hydrolasing technology to meet the challenge of decontaminating highly radioactive concrete surfaces underwater. Newly existing technology is being adapted to this unique challenge.