Florie Andre Caporuscio

Bentonite evolution at elevated pressures and temperatures: An experimental study for generic nuclear repository designs

Abstract Geologic disposal of spent nuclear fuel in high-capacity metal canisters may reduce the repository footprint, but it may yield high-thermal loads (up to 300 °C). The focus of this experimental work is to expand our understanding of the hydrothermal stability of bentonite clay barriers interacting with metallic phases under different geochemical, mineralogical, and engineering conditions. The hydrothermal experiments were performed using flexible Au/Ti Dickson reaction cells mounted in an externally heated pressure vessel at 150-160 bars and temperatures up to 300 °C for five to six weeks. Unprocessed Wyoming bentonite, containing primarily montmorillonite with minor amount of clinoptilolite, was saturated with a K-Ca-Na-Cl-bearing water (~1900 mg/L total dissolved solids) at a 9:1 water:rock mass ratio. The bentonite and solution combination contained either steel plates or Cu-foils and were buffered to low Eh using magnetite and metallic iron. During reactions, pH, K+, and Ca2+ concentrations decreased, whereas SiO2(aq), Na+, and SO42- concentrations increased throughout the experiments. Pyrite decomposition was first observed at ~210 °C, generating H2S(aq,g) that interacted with metal plates or evolves as a gas. The aqueous concentrations of alkali and alkaline earth cations appear to be buffered via montmorillonite and clinoptilolite exchange reactions. Illite or illite/smectite mixed-layer formation was significantly retarded in the closed system due to a limited K+ supply along with high Na+ and SiO2(aq) concentrations. Precursor clinoptilolite underwent extensive recrystallization during the six weeks, 300 °C experiments producing a Si-rich analcime in addition to authigenic silica phases (i.e., opal, cristobalite). Analcime and feldspar formation partially sequester aqueous Al3+, thereby potentially inhibiting illitization. Associated with the zeolite alteration is a ~17% volume decrease (quartz formation) that translates into ~2% volume loss in the bulk bentonite. These results provide chemical information that can be utilized in extending the bentonite barriers’ lifetime and thermal stability. Zeolite alteration mineralogy and illitization retardation under these experimental conditions is important for the evaluation of clay barrier long-term stability in a spent nuclear fuel repository.

Disposal Systems Evaluations and Tool Development - Engineered Barrier System (EBS) Evaluation.

Key components of the nuclear fuel cycle are short-term storage and long-term disposal of nuclear waste. The latter encompasses the immobilization of used nuclear fuel (UNF) and radioactive waste streams generated by various phases of the nuclear fuel cycle, and the safe and permanent disposition of these waste forms in geological repository environments. The engineered barrier system (EBS) plays a very important role in the long-term isolation of nuclear waste in geological repository environments. EBS concepts and their interactions with the natural barrier are inherently important to the long-term performance assessment of the safety case where nuclear waste disposition needs to be evaluated for time periods of up to one million years. Making the safety case needed in the decision-making process for the recommendation and the eventual embracement of a disposal system concept requires a multi-faceted integration of knowledge and evidence-gathering to demonstrate the required confidence level in a deep geological disposal site and to evaluate long-term repository performance. The focus of this report is the following: (1) Evaluation of EBS in long-term disposal systems in deep geologic environments with emphasis on the multi-barrier concept; (2) Evaluation of key parameters in the characterization of EBS performance; (3) Identification of key knowledge gaps and uncertainties; and (4) Evaluation of tools and modeling approaches for EBS processes and performance. The above topics will be evaluated through the analysis of the following: (1) Overview of EBS concepts for various NW disposal systems; (2) Natural and man-made analogs, room chemistry, hydrochemistry of deep subsurface environments, and EBS material stability in near-field environments; (3) Reactive Transport and Coupled Thermal-Hydrological-Mechanical-Chemical (THMC) processes in EBS; and (4) Thermal analysis toolkit, metallic barrier degradation mode survey, and development of a Disposal Systems Evaluation Framework (DSEF). This report will focus on the multi-barrier concept of EBS and variants of this type which in essence is the most adopted concept by various repository programs. Empasis is given mainly to the evaluation of EBS materials and processes through the analysis of published studies in the scientific literature of past and existing repository research programs. Tool evaluations are also emphasized, particularly on THCM processes and chemical equilibria. Although being an increasingly important aspect of NW disposition, short-term or interim storage of NW will be briefly discussed but not to the extent of the EBS issues relevant to disposal systems in deep geologic environments. Interim storage will be discussed in the report Evaluation of Storage Concepts FY10 Final Report (Weiner et al. 2010).

Brine Transport Experiments in Granular Salt

To gain confidence in the predictive capability of numerical models, experimental validation must be performed to ensure that parameters and processes are correctly simulated. The laboratory investigations presented herein aim to address knowledge gaps for heat-generating nuclear waste (HGNW) disposal in bedded salt that remain after examination of prior field and laboratory test data. Primarily, we are interested in better constraining the thermal, hydrological, and physicochemical behavior of brine, water vapor, and salt when moist salt is heated (Jordan et al., 2014; Stauffer et al., 2015). The target of this work is to use run-of-mine (RoM) salt; however during FY2015 progress was made using high purity, granular sodium chloride.

Book Review: Dangerous Neighbors: Volcanoes and Cities

Grant Heiken, a world-renowned volcanologist, has written a book based on his long history investigating volcanic hazards that is absolutely riveting. Eight of the ten chapters focus on the interplay between major metropolises and destructive volcanoes. The introductory chapter sets the stage for the remainder of the book. This chapter touches on various types of volcanic events; from Nyiragongo lava flows that disrupted the city of Goma, DRC, to debris flows from Nevado del Ruiz that killed 23,000 residents in Armero, Columbia, to the Eyjafjallajokull volcano in Iceland which spewed an ash column into the jet stream and disrupted air travel to 32 European countries for 6 days. Other issues weaved into the introduction are the social and political fallout when a predicted eruption does not occur (Soufriere de Guadeloupe), how hazard evaluation processes change, and why do major populations reside near high risk volcanoes. The next eight chapters deal with individual regions and their respective volcanic fields. The areas are: (1) Naples, Italy, (2) Mexico City, Mexico, (3) Quito, Ecuador, (4) Manila, Philippines, (5) a series of cities in Japan, including Shimabara, Kagoshima, and Tokyo, (6) Auckland New Zealand, (7) northwest United States (Seattle, Tacoma, Portland), (8) and two island cities (ancient Akrotiri, Thira, Greece and Plymouth, Monserrat, Caribbean) that may share a common fate. Most of these examples have “sidebars” at the end of the chapters that discuss the significant volcanic mechanism that is central to that volcano/ city history. These truly fascinating stories of the stunning volcanic eruptions and their aftermaths (debris flows, tsunamis, ash plumes) and how humans avoided these events (or not) should serve as notice to all cities large and small. The final chapter discusses at length how a major city should respond to volcanic hazards. It deals at length with the quandary posed over how to educate the populous and government officials at all levels. Heiken also postulates how scientists can provide potential risk and hazard assessments in a manner that can be understood by the public. He illustrates this complexity by considering the difficulty of accurate prediction of volcanic eruptions coupled with setting the criteria for evacuation notices. Declaring an eruption in 100 years is useless, while at 100 days may cause confusion and resentment if the eruption does not occur. If one waits till 10 days before a potential major eruption, it may impossible to evacuate a large population center. Of course, if you wait until 10 hours before the event, well it is probably a moot point. These are just a few of the numerous challenges that Grant Heiken poses and addresses in this wonderful, thought-provoking book. The book provides many great and in places dramatic photographs along with a chart listing large city populations and the last significant eruption by a nearby volcano. These are truly eye opening images. In addition, the frontispiece of the book contains definitions and descriptions of many volcanic phenomena central to understanding the book. The only disappointment was that there was no extensive reference list, only a group of suggested further readings. Who would be interested in such a book? I would highly recommend this to undergraduates in a variety of disciplines; geology, geography, mass communications, and risk assessment students. In addition, this should be a must read for first responders, government officials responsible for public safety at the local, state, and Federal level.

Draft Test Plan for Brine Migration Experimental Studies in Run-of-Mine Salt Backfill

The primary objective of the experimental effort described here is to aid in understanding the complex nature of liquid, vapor, and solid transport occurring around heated nuclear waste in bedded salt. In order to gain confidence in the predictive capability of numerical models, experimental validation must be performed to ensure that (a) hydrological and physiochemical parameters and (b) processes are correctly simulated. The experiments proposed here are designed to study aspects of the system that have not been satisfactorily quantified in prior work. In addition to exploring the complex coupled physical processes in support of numerical model validation, lessons learned from these experiments will facilitate preparations for larger-scale experiments that may utilize similar instrumentation techniques.

THE SMALE COLLECTION: BEAUTY IN NATURAL CRYSTALS: by Steve Smale (editors: G. Staebler and G. Neumeier), Lithographie. LLC, East Hampton, Conneticut (2006) 203 pages, hardcover,

This large format book is described by the author as a coffee table art book; however, it is much more like a labor of love for Steve Smale. Smale not only describes the early difficulties of trying to publish such a mineral “art” volume, but also his efforts to develop the talent of photographing his own specimens, some of which are published here. You can understand his passion for mineral specimens and the development of this eye-candy book from the fact that he decided to enlist the talents of Jeff Scovil (a renowned mineral photographer) to provide the remainder of the color plate images. In total, there are 101 exquisite mineral color photographs. Beside the magnificent photos, Smale also provides a very valuable discourse on his (and his wife Clara’s) personal collecting criteria. Among the many characteristics he discusses, three elements are paramount: beauty, balance, and economy. Beauty is self evident to him; the specimen should be attractive from all angles and all components (matrix and main crystal) should enhance the …