Neptunium has a high solubility in groundwaters from Yucca Mountain. Uranium in nuclear reactors produces 237Np which has a half-life of 2.14×106 years. Consequently, the transport of 237Np through tuffs is of major importance in assessing the performance of a high-level nuclear waste repository at Yucca Mountain. The objective of this work is to determine the amount of Np retardation that is provided by the minerals in Yucca Mountain tuffs as a function of groundwater chemistry.
