Sorption of nickel and neptunium in tuff

Nickel and neptunium both are elements of importance in nuclear waste isolation studies. Sorption measurements for these elements have been performed with Yucca Mountain tuffs using three natural groundwaters of various compositions. The tuff samples were of the different sorptive varieties that have been identified at Yucca Mountain. One of the groundwaters was typical of the area wells and the other two represented extremes in groundwater composition found at Yucca Mountain. The neptunium measurements were performed under ambient and controlled-atmosphere conditions. Sorption coefficients were determined for nickel and neptunium and the results will be discussed and reported as a function of groundwater composition and of ambient or controlled-atmosphere conditions