INTRODUCTIONThere exists approximately 100 million gallons of radioactive waste in underground storage tanks (USTs) at Department of Energy (DOE) sites across the United States. Approximately 54 million gallons are stored at the Hanford Site. The DOE is responsible for immobilization and permanent disposal of this tank waste. The Hanford tank waste is currently classified as high-level waste (HLW). While low-level waste (LLW) can generally be disposed of subsurface on-site, HLW must be disposed of in an underground repository such as that planned for Yucca Mountain. Since LLW disposal is obviously much less expensive than HLW, the plan for remediation at Hanford is to separate the UST waste into a small volume of HLW and a large volume of LLW.Of the 54 million gallons of UST waste at Hanford, approximately 20 volume-percent is solids-based, consisting primarily of sludge, and

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The key parameters ofČerenkov Correlated Timing (CCT) detectors are discussed. Measurements of radiator geometry, optical properties of radiator and coupling materials, and photon detector timing performance are presented.

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