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

Conference · Thu Aug 01 04:00:00 EDT 1996

OSTI ID:270697

Yu, A D; Fowler, J R; Bignell, D T

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 the water table and delay the peak time.

• Research Organization: Westinghouse Savannah River Co., Aiken, SC (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC09-89SR18035
• OSTI ID: 270697
• Report Number(s): WSRC-MS--96-0042; CONF-960482--9; ON: DE96012429
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
CLAYS
COMPUTERIZED SIMULATION
CONCRETES
CONTAMINATION
COVERINGS
E CODES
FLOW MODELS
GROUND DISPOSAL
GROUND WATER
HYDRAULIC CONDUCTIVITY
LINERS
PERFORMANCE
PERMEABILITY
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE FACILITIES
RADIONUCLIDE MIGRATION
SAVANNAH RIVER PLANT
SEALING MATERIALS
SOILS
SOLIDIFICATION
WASTE FORMS