The Lawrence Livermore National Laboratory is to conduct an in situ test of radionuclide migration in fractured granite. Radionuclides are to be injected into a fracture in the Climax Stock of the Nevada Test Site, then transported by fluid motion and subsequently withdrawn. The fluid will be injected through a borehole intersecting a near vertical fracture and withdrawn through a second borehole that intersects the fracture directly below the first. The scoping calculations presented here are intended to aid planning this experiment. In the absence of a detailed fracture description, this analysis treats the fracture as the space between parallel flat plates; the flow is a Hele-Shaw flow. The calculations predict the conditions for breakthrough of radionuclides at the outlet hole and describe the subsequent concentration history of fluid flowing from the fracture. The effects of advection, sorption, and geometric dispersion are treated.