title: Hydrous mineral dehydration around heat-generating nuclear waste in bedded salt formations.
abstract: Heat-generating nuclear waste disposal in bedded salt during the first two years after waste emplacement is explored using numerical simulations tied to experiments of hydrous mineral dehydration. Heating impure salt samples to temperatures of 265 °C can release over 20% by mass of hydrous minerals as water. Three steps in a series of dehydration reactions are measured (65, 110, and 265 °C), and water loss associated with each step is averaged from experimental data into a water source model. Simulations using this dehydration model are used to predict temperature, moisture, and porosity after heating by 750-W waste canisters, assuming hydrous mineral mass fractions from 0 to 10%. The formation of a three-phase heat pipe (with counter-circulation of vapor and brine) occurs as water vapor is driven away from the heat source, condenses, and flows back toward the heat source, leading to changes in porosity, permeability, temperature, saturation, and thermal conductivity of the backfill salt surrounding the waste canisters. Heat pipe formation depends on temperature, moisture availability, and mobility. In certain cases, dehydration of hydrous minerals provides sufficient extra moisture to push the system into a sustained heat pipe, where simulations neglecting this process do not.
authors.affiliation: †EES-16: Computational Earth Science, MS T003, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Amy B
authors.initials: AB
authors.lastname: Jordan
authors.affiliation: ‡EES-14: Earth System Observations, MS J-599, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Hakim
authors.initials: H
authors.lastname: Boukhalfa
authors.affiliation: ‡EES-14: Earth System Observations, MS J-599, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Florie A
authors.initials: FA
authors.lastname: Caporuscio
authors.affiliation: §SPO-CNP: Civilian Nuclear Programs, MS H816, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Robinson
authors.affiliation: †EES-16: Computational Earth Science, MS T003, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Philip H
authors.initials: PH
authors.lastname: Stauffer
mesh_terms: D003198:Computer Simulation; D003890:Desiccation; D006358:Hot Temperature; D008903:Minerals / Q000032:analysis*; D008962:Models, Theoretical; D008970:Molecular Weight; D009716:Numerical Analysis, Computer-Assisted; D016062:Porosity; D011850:Radioactive Waste / Q000032:analysis*; D012037:Refuse Disposal; D012965:Sodium Chloride / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D008903:Minerals; D011850:Radioactive Waste; D014867:Water; D012965:Sodium Chloride