Review of the thermal stability and cation exchange properties of the zeolite minerals clinoptilolite, mordenite, and analcime; applications to radioactive waste isolation in silicic tuff

Technical Report · Mon Jun 01 04:00:00 EDT 1981

DOI:https://doi.org/10.2172/59122· OSTI ID:59122

Smyth, J R; Caporuscio, F A

Silicic tuffs of the southern Great Basin and basalts of the Columbia River Plateau are under investigation as potential host rocks for high- and intermediate-level radioactive wastes. Nonwelded and partially welded tuffs may contain major amounts (> 50%) of the zeolite minerals clinoptilolite, mordenite, and analcime. Densely welded tuffs and some basalt flows may contain clinoptilolite as fracture filling that limits the permeability of these rocks. The cation exchange properties of these zeolite minerals allow them to pose a formidable natural barrier to the migration of cationic species of various radionuclides in aqueous solutions. However, these minerals are unstable at elevated temperatures and at low water-vapor pressures and may break down either by reversible dehydration or by irreversible mineralogical reactions. All the breakdown reactions occurring at increased temperature involve a net volume reduction and evolution of fluids. Thus, they may provide a pathway (shrinkage fractures) and a driving force (fluid pressure) for release of radionuclides to the biosphere. These reactions may be avoided by keeping zeolite-bearing horizons saturated with water and below about 85{sup 0}C. This may restrict allowable gross thermal loadings in waste repositories in volcanic rocks.

• Research Organization: Los Alamos National Lab., NM (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 59122
• Report Number(s): LA--8841-MS; ON: DE81026686
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
58 GEOSCIENCES
ANALCIME
CLINOPTILOLITE
COLUMBIA RIVER BASIN
DEHYDRATION
HIGH-LEVEL RADIOACTIVE WASTES
INTERMEDIATE-LEVEL RADIOACTIVE WASTES
ION EXCHANGE
MINERALOGY
MORDENITE
PERMEABILITY
RADIOACTIVE WASTE DISPOSAL
STABILITY
TEMPERATURE EFFECTS
TUFF
UNDERGROUND DISPOSAL
Yucca Mountain Project