Risk constraint measures developed for the outcome-based strategy for tank waste management

This report is one of a series of supporting documents for the outcome-based characterization strategy developed by PNNL. This report presents a set of proposed risk measures with risk constraint (acceptance) levels for use in the Value of Information process used in the NCS. The characterization strategy has developed a risk-based Value of Information (VOI) approach for comparing the cost-effectiveness of characterizing versus mitigating particular waste tanks or tank clusters. The preference between characterizing or mitigating in order to prevent an accident depends on the cost of those activities relative to the cost of the consequences of the accident. The consequences are defined as adverse impacts measured across a broad set of risk categories such as worker dose, public cancers, ecological harm, and sociocultural impacts. Within each risk measure, various {open_quotes}constraint levels{close_quotes} have been identified that reflect regulatory standards or conventionally negotiated thresholds of harm to Hanford resources and values. The cost of consequences includes the {open_quotes}costs{close_quote} of exceeding those constraint levels as well as a strictly linear costing per unit of impact within each of the risk measures. In actual application, VOI based-decision making is an iterative process, with a preliminary low-precision screen of potential technical options against the major risk constraints, followed by VOI analysis to determine the cost-effectiveness of gathering additional information and to select a preferred technical option, and finally a posterior screen to determine whether the preferred option meets all relevant risk constraints and acceptability criteria