A Study Of The Hydrothermal Stability Of Copper For Use As A Container Material For Nuclear Waste At The Hanford Site, Richland, Washington

Abstract

The hydrothermal stability of copper has been studied to assess its suitability as a container material for disposal of nuclear waste in the proposed repository site at Hanford, Wa. The experiments were conducted using titanium reaction cells at 200° and 300°C, 30 MPa, using Dickson rocking autoclaves for up to 3000 hours. Three of the experiments contained a quartz normative Columbia River Basalt (RCE-3), synthetic low salinity groundwater (ca. 400 mg/L Cl-), and "purified" copper powder. The results of these experiments prompted a fourth to determine the suitability of titanium as a reaction cell. The results of the copper bearing experiments suggest that: (1) the use of copper as a container material would not significantly alter basalt-water reactions in the short term; (2) care should be taken to minimize oxygen contamination of the copper as this could adversely affect the redox conditions in the repository; (3) copper does not appear to affect the solution pH although any small changes would have been masked by reactions with the titanium reaction cell. The data from the titanium cell experiment showed significant differences (in comparison to similar previous gold cell experiments) in calculated high temperature pH values and dissolved sulfide concentrations; chloride concentrations were also slightly different. The results of this experiment suggest that titanium is not inert and should probably not be used in experiments containing low ionic strength solutions.