Grout Vaults Research Articles

In-situ monitoring of electrochemical transport processes in Hanford Grout Vault Soil

Real-time spatially-resolved radiotracer and soil conductivity measurements were used to assess the fate of contaminants and the interaction of electrolysis products with Grout Vault Soil from the Department of Energy's Hanford site in Richland, Washington. Radiotracer techniques allowed the extent that a radioactive species was remediated to be unambiguously determined in the laboratory, and the method also provided insight into the immobilization of Cs + by adsorption to the soil. Conductivity measurements provided a window into the changing state of the porous medium and the propagation of electrochemically-generated species that were introduced by water electrolysis at each active electrode. Measurements of the velocity of conductivity fronts generated by water electrolysis were combined with detailed geochemical and geophysical data about the soil to evaluate plausible soil chemistries in the system. Based on ion transport rates, it was shown that the alkaline nature of the soil buffered protons generated at the anode and hydroxide anions generated at the cathode titrated surface groups in the soil.

Behavior of Concrete as a Barrier Material for Nuclear Waste Disposal

SummaryThe foundation necessary for a constitutive model to simulate the response of concrete at elevated temperature has been presented. A model including temperature dependent creep, material property degradation, and cracking is needed to evaluate the long term functional requirements of concrete as a barrier material for nuclear waste disposal. Since the stress due to thermal load is proportional to the modulus, the degradation of the modulus with time even at constant elevated temperatures requires continual redistribution of load. Furthermore, since this degradation is not recoverable, the response of the material at elevated temperatures exhibits a complex dependence not only on the temperature distribution, but on the prior thermal history of the structure.This constitutive model for the response of concrete at elevated temperatures has been implemented into an implicit, finite element program called ANACAP [8]. Because of the direct coupling with temperature, both through thermal loads and material property dependency, ANACAP also contains a heat transfer module that includes thermal effects due to fluid flow and moving material boundaries. This program has been applied to problems involving underground waste storage tanks and grout vaults at the DOE Hanford site in Richland, Washington.