ENGINEERED AND NATURAL NEW MEXICO ANALOGUES FOR GEOLOGIC ISOLATION OF HEAT GENERATING WASTE IN ROCK SALT

摘要

Underground nuclear detonations are confidence-inspiring engineered analogues for safe confinement of heat generating waste in geologic repositories. An excellent domestic example is the 3kt Gnome test (part of the Plowshare series) in salt beds east of Carlsbad, New Mexico. Radioactively laced steam vented briefly and dispersed quickly to innocuous concentrations immediately after the approx400m deep nuclear test, but regular monitoring since then has not detected releases of harmful materials in almost 50 years. Gnome therefore presents an extreme, beyond-worst-case scenario by comparison with the anticipated performance of the WIPP (approx12km northeast), and it augurs well for contemplated repositories in salt for heat generating waste. Igneous dikes prove the generally insignificant effects of significant heat sources on surrounding rocks. Specifically, vertical Tertiary basalt dikes cutting through horizontal Permian salt beds in Germany and New Mexico altered the host rock only along narrow rims and induced only very localized and insignificant fluid movement. The invaded rock salt remained impermeable even to gas through millions of years as demonstrated by pockets of CO_(2) under high pressure that potash mines encounter occasionally near the dikes. Repositories for heat generating waste will be suitable for their purpose and perform effectively if their locations are selected based on scientific and technical criteria. Local natural and engineered analogues demonstrate the suitability of the salt beds near Carlsbad for isolating all categories of dangerous materials (classified as radioactive or not, heat generating or not).