Conasauga Near Surface Heater Experiment. Implications for a repository sited in a water-saturated argillaceous formation

Results of the Conasauga Near Surface Heater Experiment suggest that the effects of ground water on a repository located in shale would be most pronounced in their influence on chemical processes. Despite the water-saturated condition of the Conasauga shale, conduction, not convection, was the principal mode of heat transport. Metal corrosion, however, was found to be significantly enhanced by the refluxing steam. The several centimeters of scale left behind by the boiling water, in a repository, could interfere with retrieval operations or form a coating of low thermal conductivity material on a canister. Finally, alternate wetting and drying due to sporadic steam generation caused up to 20 microns of alteration on a sample of borosilicate waste glass simulant (PNL 75-25) included in the test