Charles R. Cole

Transient Inverse Calibration of Hanford Site-Wide Groundwater Model to Hanford Operational Impacts - 1943 to 1996

This report describes a new initiative to strengthen the technical defensibility of predictions made with the Hanford site-wide groundwater flow and transport model. The focus is on characterizing major uncertainties in the current model. PNNL will develop and implement a calibration approach and methodology that can be used to evaluate alternative conceptual models of the Hanford aquifer system. The calibration process will involve a three-dimensional transient inverse calibration of each numerical model to historical observations of hydraulic and water quality impacts to the unconfined aquifer system from Hanford operations since the mid-1940s.

Transient Inverse Calibration of Site-Wide Groundwater Model to Hanford Operational Impacts from 1943 to 1996--Alternative Conceptual Model Considering Interaction with Uppermost Basalt Confined Aquifer

The baseline three-dimensional transient inverse model for the estimation of site-wide scale flow parameters, including their uncertainties, using data on the transient behavior of the unconfined aquifer system over the entire historical period of Hanford operations, has been modified to account for the effects of basalt intercommunication between the Hanford unconfined aquifer and the underlying upper basalt confined aquifer. Both the baseline and alternative conceptual models (ACM-1) considered only the groundwater flow component and corresponding observational data in the 3-Dl transient inverse calibration efforts. Subsequent efforts will examine both groundwater flow and transport. Comparisons of goodness of fit measures and parameter estimation results for the ACM-1 transient inverse calibrated model with those from previous site-wide groundwater modeling efforts illustrate that the new 3-D transient inverse model approach will strengthen the technical defensibility of the final model(s) and provide the ability to incorporate uncertainty in predictions related to both conceptual model and parameter uncertainty.

Uncertainty Analysis Framework - Hanford Site-Wide Groundwater Flow and Transport Model

Pacific Northwest National Laboratory (PNNL) embarked on a new initiative to strengthen the technical defensibility of the predictions being made with a site-wide groundwater flow and transport model at the U.S. Department of Energy Hanford Site in southeastern Washington State. In FY 2000, the focus of the initiative was on the characterization of major uncertainties in the current conceptual model that would affect model predictions. The long-term goals of the initiative are the development and implementation of an uncertainty estimation methodology in future assessments and analyses using the site-wide model. This report focuses on the development and implementation of an uncertainty analysis framework.

Composite Analysis for Low-Level Waste Disposal in the 200 Area Plateau of the Hanford Site, Southeast Washington

A composite analysis of low-level radioactive waste disposal and other radioactive sources was recently completed for the Hanford Site in Southeast Washington State. Impacts from source release and environmental transportwere estimated for a 1 000-year period following Site closure in a multi-step process involving 1) estimation of radiological inventories and releases, 2) assessment of contaminant migration through the vadose zone, groundwater, and atmospheric pathways, 3) and estimation of doses. The analysis showed that most of the radionuclide inventory in past-practice liquid discharge sites and pre-1988 solid waste burial grounds on the 200 Area Plateau will be released in the first several hundred years following Hanford Site closure, well before projected releases from active and planned disposals of solid waste. The maximum predicted agricultural dose was less than 6 mrem/y in 2050 and declined thereafter. The maximum doses for the residential, industrial, and recreational scenarios, were 2.2, 0.7, and 0.04 mrem/y, respectively, and also declined after 2050.