11 Matching Results

Search Results

Advanced search parameters have been applied.

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

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: December 31, 1991
Creator: Yu, A. D.
Partner: UNT Libraries Government Documents Department

An estimation of tritium inventory limits for the E-Area vaults

Description: At the request of Waste Management, Interim Waste Technology has conducted a modeling study to estimate the tritium inventory limits for the E-Area vaults. These inventory limits are based on the groundwater impact of the planned waste disposal. The tritium inventory limit for an Intermediate Level Tritium Vault (ILTV) is estimated to be 400,000 Curies with a 100 year storage period. During this period, it is assumed that the ILTV will be vented, any leachate will be extracted, and its performance will be carefully monitored. The tritium inventory limits for a Low Activity Waste Vault (LAWV) and an Intermediate Level Non-Tritium Vault (ILNTV) are estimated to be 15,000 and 11,000 Curies, respectively. Venting and leachate extraction were not assumed necessary. These operational alternatives would further enhance the performance of these vaults. These limits are significantly higher than the forecasted maximum tritium inventories for the vaults. Details of the modeling study are described in the attached report.
Date: December 2, 1991
Creator: Yu, A. D. & Cook, J. R.
Partner: UNT Libraries Government Documents Department

Mechanisms of contaminant migration from grouted waste

Description: Low-level radioactive decontaminated salt solution is generated at the Savannah River Site (SRS) from the In-Tank Precipitation process. The solution is mixed with cement, slag, and fly ash, to form a grout, termed ``Saltstone``, that will be disposed in concrete vaults at the Saltstone Disposal Facility (SDF) [1]. Of the contaminants in the Saltstone, the greatest concern to SRS is the potential release of nitrate to the groundwater because of the high initial nitrate concentration (0.25 g/cm{sup 3}) in the Saltstone and the low Safe Drinking Water Act (SDWA) maximum contaminant level (MCL) of 44 mg/L. The SDF is designed to allow a slow, controlled release over thousands of years. This paper addresses a modeling study of nitrate migration from intact non-degraded concrete vaults in the unsaturated zone for the Radiological Performance Assessment (PA) of the SRS Saltstone Disposal Facility [3]. The PA addresses the performance requirements mandated by DOE Order 5820.2A [4].
Date: December 31, 1992
Creator: Magnuson, S. O. & 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

An estimation of tritium inventory limits for the E-Area vaults

Description: At the request of Waste Management, Interim Waste Technology has conducted a modeling study to estimate the tritium inventory limits for the E-Area vaults. These inventory limits are based on the groundwater impact of the planned waste disposal. The tritium inventory limit for an Intermediate Level Tritium Vault (ILTV) is estimated to be 400,000 Curies with a 100 year storage period. During this period, it is assumed that the ILTV will be vented, any leachate will be extracted, and its performance will be carefully monitored. The tritium inventory limits for a Low Activity Waste Vault (LAWV) and an Intermediate Level Non-Tritium Vault (ILNTV) are estimated to be 15,000 and 11,000 Curies, respectively. Venting and leachate extraction were not assumed necessary. These operational alternatives would further enhance the performance of these vaults. These limits are significantly higher than the forecasted maximum tritium inventories for the vaults. Details of the modeling study are described in the attached report.
Date: December 2, 1991
Creator: Yu, A. D. & Cook, J. R.
Partner: UNT Libraries Government Documents Department

Radiological performance assessment for the E-Area Vaults at the Savannah River Site. Part 2, Simulation of contaminant migration in the far-field

Description: Two papers presented in this session cover a numerical simulation of radionuclide migration beneath Savannah River Site`s E-Area Vaults (EAV) within the unsaturated and saturated flow fields. This paper (Part II) describes the simulation of radionuclide migration within the saturated zone. Simulations were conducted for 23 radionuclides which are planned to be disposed within the EAV Facility (EAVF). Part I of this study used a nominal starting inventory of 1 Curie for each radionuclide in each group of vaults. Output concentrations from the near-field model were utilized as input for the far-field, or saturated zone transport model. Mechanisms for the migration of radionuclides in the saturated zone are convection and diffusion. Other mechanisms impacting migration of radioisotopes are radioactive decay and adsorption. A partition coefficient (K{sub d}) is used in this model to account for other geochemical effects such as solubility, chemical speciation and colloid formation. Results of simulations indicate that contaminants migrate laterally toward discharge zones at local streams. Groundwater concentrations were calculated for the 23 radionuclides and were converted to doses to man for a groundwater pathway scenario in which an individual ingests 2 liters (L) of groundwater daily. Since calculated doses are in terms of a unit disposal quantity, they will be used to compute the disposal limits for each radionuclide. These limits, and hence the vault loading capacity, will be maximized while maintaining acceptable levels of exposure to individuals exposed through the different pathways. The source term for contaminants at the water table was generated by the vadose zone model described in Part I of this paper and entered as fluxes over time.
Date: March 1, 1994
Creator: Hiergesell, R. A.; Yu, A. D.; Cook, J. R.; McDowell-Boyer, L. M. & Kearl, P. M.
Partner: UNT Libraries Government Documents Department

Radiological performance assessment for the E-Area Vaults at the Savannah River Site, Part 1: Simulation of radionuclide migration in the near-field

Description: Two papers presented in this session cover a numerical simulation of radionuclide migration from Savannah River Site`s E-Area Vaults (EAV) to the groundwater. These vaults are constructed below the ground surface and above the historical high water table. This paper covers the simulation of radionuclide migration in the unsaturated zone. A saturated zone model containing aquifers affected by the facility was also developed. The rate (Curies/yr) of radionuclide release to the water table obtained from Part I was used as the source term for the saturated zone model. The migration of 23 key radionuclides for up to two million years was predicted [Westinghouse 1994]. The calculated annual dose of each of the radionuclides due to ingestion of water, based on unit initial inventory, is reported in Part II.
Date: February 1, 1994
Creator: Yu, A. D.; Cook, J. R.; Lam, P. S.; Wilhite, E. L. & Smith, C. S.
Partner: UNT Libraries Government Documents Department

Mechanisms of contaminant migration from grouted waste

Description: Low-level radioactive decontaminated salt solution is generated at the Savannah River Site (SRS) from the In-Tank Precipitation process. The solution is mixed with cement, slag, and fly ash, to form a grout, termed Saltstone'', that will be disposed in concrete vaults at the Saltstone Disposal Facility (SDF) [1]. Of the contaminants in the Saltstone, the greatest concern to SRS is the potential release of nitrate to the groundwater because of the high initial nitrate concentration (0.25 g/cm[sup 3]) in the Saltstone and the low Safe Drinking Water Act (SDWA) maximum contaminant level (MCL) of 44 mg/L. The SDF is designed to allow a slow, controlled release over thousands of years. This paper addresses a modeling study of nitrate migration from intact non-degraded concrete vaults in the unsaturated zone for the Radiological Performance Assessment (PA) of the SRS Saltstone Disposal Facility [3]. The PA addresses the performance requirements mandated by DOE Order 5820.2A [4].
Date: January 1, 1992
Creator: Magnuson, S.O. (EG and G Idaho, Inc., Idaho Falls, ID (United States)) & Yu, A.D. (Westinghouse Savannah River Co., Aiken, SC (United States))
Partner: UNT Libraries Government Documents Department