Nuclear strata: Enacting clay for the deep geological disposal of nuclear waste in Switzerland.

For the realization of a deep geological repository, geoscientists have investigated various geological formations and assessed their suitability as host rocks for the long-term disposal of high-level nuclear waste. A fundamental epistemological uncertainty has characterized this geoscientific exploration of the subterranean, evolving not only as a scientific-technical challenge in deep geological disposal projects but also as a sociopolitical one. This paper scrutinizes how the Swiss nuclear waste organization, during its recent drilling campaign, has publicly staged the Opalinus clay as a stable rock in order to make its disposal project feasible and sound. Based on ethnographic fieldwork as well as document and media analysis, it traces how science communication experts have created and arranged a series of maps, models, and materials to make the subterranean tangible to a surface audience over the course of the campaign. Strategically assembled at specific events, it shows that these political materials did not simply represent subterranean spaces but constituted a stratified subterranean geology on the surface. On this basis, this paper underlines the performative dimension of geology and the key importance of stabilizing geology in science-society encounters for deep geological disposal projects to advance. By illustrating how the subterranean has come to matter and became politically significant in Switzerland's contentious nuclear (waste) history, this paper contributes to a better understanding of the constitutive role of geology for imagining a postnuclear future.