Executive SummaryThis report presents the rationale for adopting a recommended characterization strategy that uses a risk-based decision-making eamework for managing the Tank Waste Characterization Program at Hanford. The risk-managemendvalue-of-information (VOI) strategy that is illustrated explicitly links each information-gathering activity to its cost and provides a mechanism to ensure that characterization funds are spent where they can produce the largest reduction in risk. The approach was developed by tailoring well-known decision analysis techniques to specific tank waste characterization applications. 'This report illustrates how VOI calculations are performed and demonstrates that the VOI approach can definitely be used for real Tank Waste Remediation System (TWRS) characterization problems.The goal of a characterization strategy is to provide timely information to support decisions. Information has value if it leads to better decisions, which are those with better expected consequences. Thus the VOI should be gauged by the expected increase in the value of decisions. Frequently, information will reduce uncertainty about consequences. Idormation will also often lead to decisions that involve reduced risks.Qualitatively speaking, a source of information (e.g., a tank waste sample) is valuable if it has the potential for changing subsequent decisions, such as whether to keep transuranic (TRU) waste separate from high-level waste (HLW). For a source of information to be valuable, two conditions must be met:1. The decision alternatives must have uncertain consequences (otherwise, there is nothing to be learned from the information).2. Depending on the information obtained, different decisions may be best (otherwise, the information would not have any impact).VOI decision analysis techniques are used for determining risk-based characterization requirements.This approach provides an understandable technical basis that explicitly links sampling, analysis, physicalchemical modeling, and other "learning" activities to risk reduction. Furthermore, VOI analysis provides a clear measure of completion because additional characterization activities are not justified when the costs exceed the calculated risk reduction value.Risk-based requirements defined in terms of the VOI become a defensible basis for integration and prioritization of needs across tanks and program elements requiring information about waste composition, phenomenology, and performance. Knowing the value of obtaining specific information will provide an explicit basis for investments in research and/or technology development to reduce costs and technical uncertainty. This approach will also provide a defensible basis for budgeting and scheduling decisions by providing the means for selecting the most impactfid characterization work for funding each year. This integration, coupled with statistically and technically sound sampling and analysis, monitoring, and laboratow methods, will result in an implementation plan that provides the most cost-effect...