No radioactive materials are used in this test, only safe chemical tracers. Sprinklers atop a large block of rock distribute water and tracers. Sensors monitor the water and tracer movement at the bottom of the block. If a repository were located here, scientists expect minerals in the rock, called zeolites, to act as a natural barrier, limiting or slowing the movement of radioactive particles. Movement, cracking, and other changes could affect the rock's suitability for housing a repository.
Excavation creates pressure on the rock.
This test, conducted at several locations, measures how Yucca Mountain rock responds. Aluminum jacks set horizontally inside a test alcove apply force to rock walls. Instruments monitor movement of the walls and compression of the rock beyond the walls. Measuring the squeezing of the rock provides scientists with data they can use to predict how stresses will affect the rock. Each week, scientists download information into laptop computers from instruments installed in the steel sets in the tunnel.