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The performance assessment and the design of an intermediate level tritium disposal vault

Description: The topic of this report is the assessment of the performance and design of the tritium disposal vault for the Westinghouse River Company at the Savannah River Laboratory. This paper describes how the groundwater modeling has affected the design of a tritium disposal vault at the Savannah River Site and this new vault will meet the regulatory performance requirements. (MB)
Date: January 1, 1991
Creator: Yu, A.D.
Partner: UNT Libraries Government Documents Department

Effect of Saltstone Vault Roof Configuration on the Rate of Contaminant Transport

Description: At the Savannah River Site, low-level radioactive decontaminated salt solution is mixed with slag, flyash, and cement to form a grout-like material called ``Saltstone``. The Saltstone is poured into concrete vaults constructed at the Saltstone Disposal Facility (SDF). The impact of SDF on groundwater has been studied in a radiological performance assessment (PA). Sophisticated groundwater models were used to predict the groundwater flow and contaminant transport problems. The modeling effort was divided into two parts: the unsaturated-zone model and the saturated zone model. One of the major performance objectives is to show that the impacted groundwater will be in compliance with the Safe Drinking Water Act.
Date: December 28, 1994
Creator: Hsu, R. H.; Yu, A. D. & Lam, Poh-Sang
Partner: UNT Libraries Government Documents Department

Effects of closure cap and liner on contaminant release rates from grouted wastes

Description: This paper describes a groundwater modeling study of waste disposal concepts using grouted waste forms. The focus of the study is on the effects of clay caps and concrete vaults on contaminant migration. The authors modeled three waste disposal scenarios: (1) Grouted waste was solidified in an earthen trench and covered with soil, there was no vault and no cap; (2) grouted waste was solidified in an earthen trench, the entire waste disposal facility was then closed under a clay cap; (3) grouted waste was solidified in a concrete vault and protected by the same closure as in 2. Because of the huge contrast in hydraulic conductivities and highly non-linear multi-phase flow characteristics, these waste disposal concepts presented a difficult problem for numerical simulation. Advanced fluid flow and contaminant transport codes were used to solve the problem. Among the codes tested, ECLIPSE out-performed other codes in speed, accuracy (smaller material balance errors) and capability in handling sophisticated scenarios. The authors used nitrate as a tracer for the simulation. Nitrate does not absorb in the solid phase and does not decay. As a result, predicted release rate based on nitrate is conservative. They also assumed that the facility is intact for 10,000 years. In other words, properties of the materials used for this study do not change with time. Predicted peak flux for the no vault and no closure case was 5.8 {times} 10{sup {minus}4} per year at 12 years. If a clay cap was installed, predicted peak flux was 8.5 {times} 10{sup {minus}5} per year at 110 years. If the grout was disposed in a concrete vault and covered by a clay cap, predicted peak flux became 4.4 {times} 10{sup {minus}6} per year at 8,000 years. Both concrete liner and clay cap can reduce the rate of contaminant release to ...
Date: August 1, 1996
Creator: Yu, A.D.; Fowler, J.R. & Bignell, D.T.
Partner: UNT Libraries Government Documents Department

Effect of roof slope and thickness on the performance of a saltstone vault

Description: At the Savannah River Site, low-level radioactive decontaminated salt solution is mixed with slag, flyash, and cement to form a grout-like material called ``Saltstone.`` The Saltstone is poured into concrete vaults constructed at the Saltstone Disposal Facility (SDF). The SDF is designed for the release of contaminants in a slow, controlled manner over thousands of years. The impact of SDF on groundwater has been studied in a radiological performance assessment (PA). Groundwater models were used to predict the fluid flow and contaminant transport at SDF. The models predicted a spatial contaminant concentration distribution in groundwater as a function of time. This study focuses on the roof configuration of Saltstone vault, with special interests in cost-effectiveness. We conducted a study to evaluate the effect of roof slope and thickness on the performance of a Saltstone vault. Four roof configurations were simulated. The tool used for the simulation was ECLIPSE, a finite-difference petroleum reservoir engineering code with an environmental tracer option. Nitrate was used as the ``tracer`` contaminant. In this study, ECLIPSE solves the two-phase two-dimensional flow and transport problem up to 10,000 years. This paper describes a modeling study used to evaluate roof design options for the Saltstone vault.
Date: September 1995
Creator: Yu, A. D.; Lam, Poh-Sang & Hsu, R. H.
Partner: UNT Libraries Government Documents Department