The Waste Isolation Pilot Plant (WIPP), a Department of Energy (DOE) facility located in southeastern New Mexico near Carlsbad, is the first nuclear waste repository certified by the United States Environmental Protection Agency (EPA). The first waste disposal panel, Panel 1, was completed in 1988, and Panel 2 was completed in 2000. Although the geometry of Pand 2 is identical to that of Panel 1, the pattern of creep behavior of Panel 2 is anticipated to differ from that of Panel I because of its proximity to the first panel. Early in situ monitoring results appear to match a conceptual model of excavation performance. Two three-dimensional numerical models are being used to assess the interaction between Panel I and Panel 2 and have produced initial results.


Three-dimensional numerical modeling of WIPP disposal panels has been performed to simulate the effect of mining a second waste disposal panel adjacent to an existing panel. The timing and geometry of the models were selected to simulate the effect of mining Panel 2 on Panel 1. The primary goals of the modeling were to quantify the potential increases in displacement rates and shear strain that contribute to fracturing in the old panel (Panel 1), and to estimate the long-term displacement rates in the new panel (panel 2).

1.1 Background

The work presented here was completed for the United States Department of Energy (DOE), which was authorized by Public Law 96-164 to provide a research and development facility for demonstrating the safe permanent disposal of transuranic (TRU) wastes from national defense activities and programs of the United States exempted from regulations by the U.S. Nuclear Regulatory Commission (NRC). The Waste Isolation Pilot Plant (WIPP), located in southeastern New Mexico near Carlsbad, an underground repository for disposal of TRU wastes located 650 meters deep in a bedded halite formation. In its final configuration, WIPP will include eight panels of seven waste disposal rooms each. The rooms are about 90 meters long, 10 meters wide, and four meters high. They are separated by 30 meter wide pillars. The panels are separated by 60 meter wide barrier pillars.

The excavation of Panel 1 rooms and access drffis was completed in 1988 and took about two years (DOE, 1992). Panel 2 excavation was completed in October 2000 and took about one year. Panel I required more extensive ground control maintenance than was originally planned, primarily because of the eleven-year delay in waste receipt. In general, the geomechanical performance of Panel 1 met all design requirements.

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