Casks intended to hold and isolate radioactive waste at the Yucca Mountain underground repository in Nevada can break down in decades, say Catholic University chemists in a study for the State of Nevada. The chemists say a combination of heat generated by the high-level radioactive waste and water seeping through the mountain will create a highly acidic concentrate that will quickly corrode the nickel-based alloy from which the casks will be made. They also say fluoride and chloride in the mountain's water will corrode a titanium "drip shield" that Department of Energy scientists have added to the design to stop water from reaching the casks. The integrity of the engineered waste isolation system has become increasingly important as geologists have found water to be moving through the mountain where the waste is to be buried. Regulations require DOE to design a repository that ensures the waste is isolated from the environment for at least 10,000 years. Allen Benson, a DOE spokesman, called the report "great theater," charging that the environment created in the study does not match the conditions at Yucca Mountain. Catholic University researcher April L. Pulvirenti (shown) responds that researchers subjected the alloys to water similar to that of the mountain and heat in the range expected from the waste casks. The potential for corrosion of the engineered system is the subject of a two-day meeting this week of the Nuclear Waste Technical Review Board, a DOE oversight body.