Effects of Introduced Materials in the Drift Scale Test.

[摘要] Water samples previously acquired from superheated (>140 degrees C) zones within hydrological test boreholes of the Drift Scale Test (DST) show relatively high fluoride concentrations (5 - 66 ppm) and low pH (3.1 - 3.5) values. In these high temperature regions of the rock, water is present superheated vapor only--liquid water for sampling purposes is obtained during the sampling process by cooling. Based on data collected to date, it is evident that the source of the fluoride and low pH is from introduced man-made materials (TeflonTM and/or VitonTM fluoroelastomer) used in the test. The test materials may contribute fluoride either by degassing hydrogen fluoride (HF) directly to produce trace concentrations of HF gas (-0.1 ppm) in the high temperature steam, or by leaching fluoride in the sampling tubes after condensation of the superheated steam. HF gas is known to be released from VitonTM at high temperatures (Dupont Dow Elastomers L.L.C., Elkton, MD, personal communication) and the sample water compositions indicate near stoichiometric balance of hydrogen ion and fluoride ion, indicating dissolution of HF gas into the aqueous phase.

[发布机构] Technical Information Center Oak Ridge Tennessee

[学科分类] 工程和技术（综合）

[关键词] Thermal expansion;High-level radioactive wastes;Deformation;Rock properties;Yucca Mountain