System Assessment Capability Research Articles

Vadose zone modeling of dispersed waste sites in the framework of an integrated stochastic environmental transport and impacts assessment code for the Hanford Site

The system assessment capability (SAC) is the first total-system stochastic simulator to address inventory distribution, environmental release and transport, and impacts to human health and ecological, economic, and cultural resources from hundreds of radiological and chemical waste disposal sites for the entire Hanford Site in southeast Washington State. Flow and contaminant transport modeling in the vadose zone at 720 individual sites has been integrated into the SAC stochastic software framework using the STOMP code, providing the means to define release to the regional aquifer to support the SAC groundwater transport model. Important features, events, and processes including remedial actions, time-variant natural infiltration rates, and high volume aqueous-phase discharges were addressed in the software and data. A separate data extraction program, VZGRAB, was developed to enable analysts to aggregate vadose zone release data across the hundreds of waste sites in various ways following a SAC simulation to develop an improved understanding of the system performance and uncertainty aspects.

Modeling Long-Term Risk to Environmental and Human Systems at the Hanford Nuclear Reservation: Scope and Findings from the Initial Model

The Groundwater Protection Project at the US Department of Energy Hanford Site in Washington State is currently developing the means to assess the cumulative impact to human and ecological health and the regional economy and cultures from radioactive and chemical waste that will remain at the Hanford Site after the site closes. This integrated system is known as the System Assessment Capability (SAC). The SAC Risk/Impact Module discussed in the article uses media- and time-specific concentrations of contaminants estimated by the transport models of the integrated system to project potential impacts on the ecology of the Columbia River corridor, the health of persons who might live in or use the corridor or the upland Hanford environment, the local economy, and cultural resources. Preliminary Monte Carlo realizations from the SAC modeling system demonstrate the feasibility of large-scale uncertainty analysis of the complex relationships in the environmental transport of contaminants on the one hand and ecological, human, cultural, and economic risk on the other. Initial impact results show very small long-term risks for the 10 radionuclides and chemicals evaluated. The analysis also helps determine science priorities to reduce uncertainty and suggests what actions matter to reduce risks.

A Stochastic Assessment of Nuclear Waste Management Practices at the Hanford Site, Washington

ABSTRACTWaste management and disposal decisions at the Hanford Site, Washington, depend in part on an understanding of the risks and impacts associated with alternate disposal and remedial actions. A proof-of-principle site-wide assessment of the risks and impacts associated with all wastes that will remain at the Hanford Site following cleanup has been performed for the first time. It simulates contaminant release, migration, and fate from the initiation of site operations in 1944 forward, and, thus, illustrates historical and near-term influences on long-term risk and impact.A stochastic simulation tool capable of addressing 1000 waste discharge and disposal sites and 10 contaminants for a period of 1000 years has been created and applied. Human health and ecological risks as well as impacts to the regional economy and local cultures are estimated. The methodology developed is known as the System Assessment Capability (SAC). It is currently in a Revision 0 state corresponding to a proof-of-principle demonstration.An initial assessment based on the planning baseline of the U.S. Department of Energy (Richland Operations office and office of River Protection) has been undertaken. Preliminary results of the assessment indicate variability in predictions is most influenced by uncertainty in:- geochemical adsorption (i.e., distribution coefficients, Kd) for contaminant release, vadose zone, and groundwater models; especially for uranium and iodine which are somewhat but not greatly adsorbed,- solid waste burial ground inventories of iodine-129, and- liquid discharge site inventories of technetium-99.It is apparent that variables governing change in performance are a function of space and time. Initially, these results point to the need for related models and data to be examined, and, if necessary, augmented through future laboratory and field studies to better quantify or reduce uncertainty.

Integrated Modeling for Launch System Architecture Optimization

ABSTRACTIn a world of increasing competition and declining government space budgets, the emphasis in new launch system design has shifted from performance optimization to cost reduction. Architects making complex launch system design decisions are handicapped by the unavailability of analytical tools that provide an integrated life cycle cost analysis that quantifies the impact of design decisions. Vehicle performance, operational efficiency, reliability and ground system design all have a major effect on cost. This paper focuses on a research effort to integrate 6 separate models developed at The Aerospace Corporation to provide an integrated launch system assessment capability. The impact on the system architecting process will be discussed as well as the ability to identify and prioritize necessary design enhancements or new technologies.