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Deep Borehole Disposal of Nuclear Waste

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "B: Energy and Environment".

Deadline for manuscript submissions: closed (17 May 2019) | Viewed by 44871

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Special Issue Editors

Dr. Dirk Mallants

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Guest Editor

Land and Water - CSIRO, Private Bag 2, Glen Osmond, SA 5064, Australia
Interests: groundwater hydrogeology; radionuclide transport; engineered barrier performance; safety assessment
Special Issues, Collections and Topics in MDPI journals

Dr. Karl Travis

E-Mail Website
Guest Editor

Department of Materials Science and Engineering, Sheffield University, Sheffield S1 3JD, UK
Interests: sealing systems for deep geological boreholes; multiscale modelling; statistical mechanics; non-equilibrium simulation; radiation damage in ceramics and glasses

Prof. Neil Chapman

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Guest Editor

Department of Materials Science and Engineering, University of Sheffield, Mappin St, Sheffield S1 3JD, UK
Interests: radioactive waste management; deep geological disposal systems; multinational repository solutions; post-closure safety assessment; site characterisation; natural hazards

Dr. Patrick Brady

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Guest Editor

Sandia National Laboratories, Albuquerque, NM 87123, USA
Interests: nuclear waste disposal; water treatment; enhanced oil recovery

Mr. Hefin Griffiths

E-Mail Website
Guest Editor

ANSTO, locked bag 2001, Kirrawee DC, NSW 2232, Australia
Interests: radioactive waste management; radiation protection; safety assessment

Special Issue Information

Dear Colleagues,

Management of radioactive wastes from medical, scientific and industrial use of radio-isotopes and from energy production poses both technological and societal challenges. Low-level and some intermediate-level radioactive wastes (LILW) can be safely disposed in engineered near-surface repositories, but longer-lived intermediate-level waste (ILW), spent fuel from nuclear reactors (SF), high-level wastes from reprocessing of SF (HLW) and long-lived spent sealed sources (SSS) are considerably more radioactive and have a higher content of long-lived radionuclides. These wastes require a higher degree of containment and isolation deep underground, typically in geological disposal facilities (GDF). A wide range of GDF designs has been investigated and developed internationally, tailored to suit specific wastes types and geological conditions. Disposal in medium-depth (tens to hundreds of metres) boreholes in suitable hard rock or sedimentary formations can provide adequate isolation and containment for safe and cost-effective disposal of relatively small volumes of ILW and SSS. Deeper borehole disposal (hundreds to thousands of metres) has been considered for HLW, SF, separated plutonium wastes and some very high specific activity fission-product wastes—its modularity being one of the major advantages over traditionally mined GDFs. This Special Issue is intended to provide an overview of R&DD developments over the past decade in regards to both medium depth SSS disposal and deep borehole disposal for various nuclear wastes.

For this Special Issue, we invite papers that discuss aspects of identifying waste streams potentially suitable for borehole disposal, site suitability characteristics and site selection, subsurface characterisation of host rock and deep fluids, coupled thermal-hydraulic-mechanical-chemical modelling of borehole-host rock environments, borehole design and drilling and borehole management technologies, waste handling and emplacement technologies, borehole sealing, long-term engineered barrier behaviour under high pressure and temperature, post-closure safety assessments, cost and economic modelling and strategic aspects of borehole disposal in national waste management programmes. We also welcome discussions on regulatory challenges surrounding deep borehole disposal, including those around safeguards termination versus ongoing monitoring.

Dr. Dirk Mallants
Dr. Karl Travis
Prof. Neil Chapman
Dr. Patrick Brady
Mr. Hefin Griffiths
Guest Editors

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Keywords

Drilling technology
Seal behaviour
Extreme environment geosciences
Thermal-hydraulic-mechanical-chemical modelling

Published Papers (10 papers)

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Editorial

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7 pages, 193 KiB

Open AccessEditorial

The State of the Science and Technology in Deep Borehole Disposal of Nuclear Waste

by Dirk Mallants, Karl Travis, Neil Chapman, Patrick V. Brady and Hefin Griffiths

Energies 2020, 13(4), 833; https://doi.org/10.3390/en13040833 - 14 Feb 2020

Cited by 14 | Viewed by 5366

Abstract

This Special Issue of the Energies Journal on Deep Borehole Disposal of Nuclear Waste has delivered a timely update on the science and technology of borehole disposal and the types of radioactive wastes it could potentially accommodate. The Special Issue papers discuss (i) circumstances under which a national waste management programme might wish to consider deep borehole disposal; (ii) a status report of deep borehole disposal options in Germany; (iii) the analysis of corrosion performance of engineered barrier systems; (iv) a review of the potential cementing systems suitable for deep borehole disposal; (v) the thermal evolution around heat-generating waste for a wide range of material properties and disposal configurations; (vi) a geochemical analysis of deep brines focussed on fluid-rock interactions; (vii) post-closure performance assessment calculations for deep borehole disposal of Cs/Sr capsules and an example safety case for (viii) horizontal and (ix) vertical deep borehole disposal of nuclear wastes. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

Research

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7 pages, 819 KiB

Open AccessArticle

Granite Hydrolysis to Form Deep Brines

by Patrick Brady, Carlos Lopez and Dave Sassani

Energies 2019, 12(11), 2180; https://doi.org/10.3390/en12112180 - 07 Jun 2019

Cited by 9 | Viewed by 2912

Abstract

Reaction path calculations suggest that water fixation by zeolite and chlorite formation can account for much of the high salinity of deep brines in contact with deep granites, as well as their Ca/Na ratios, which reflect the rock-dominated chemistry of such brines. Resultant brines, undiluted by the influx of shallower fresher waters, are likely to be at equilibrium with laumontite, chlorite, calcite, dolomite, anhydrite/gypsum, K-feldspar, quartz, plagioclase, and possibly halite. The growth of laumontite and chlorite consumes water, causing the concentration of residual salts to increase during the formation of such brines. In these analyses, the major trends suggest that these fundamental processes drive this outcome naturally. Predicted phase assemblages and end-point water compositions are relatively unaffected by the chemistry of the starting/reacting fluid. Additionally, mineralogical and mineral compositional variations both appear to have no major impact on brine formational trends. More precise analysis involves the use of Pitzer coefficients and considers Br/Cl exchange in the alteration phases. Explicit consideration of silicate dissolution points to water availability as a key control over granite alteration. Diffusion-limited water availability appears to lead to stagnant systems dominated by the increasing brine density and Ca/Na ratios with depth. Alteration phases tend to decrease permeability and porosity, further isolating such systems from the flow of shallower dilute fluids. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

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21 pages, 4316 KiB

Open AccessFeature PaperArticle

Deep Borehole Disposal Safety Case

by Geoff A. Freeze, Emily Stein, Patrick V. Brady, Carlos Lopez, David Sassani, Karl Travis, Fergus Gibb and John Beswick

Energies 2019, 12(11), 2141; https://doi.org/10.3390/en12112141 - 04 Jun 2019

Cited by 9 | Viewed by 3722

Abstract

The safety case for deep borehole disposal of nuclear wastes contains a safety strategy, an assessment basis, and a safety assessment. The safety strategy includes strategies for management, siting and design, and assessment. The assessment basis considers site selection, pre-closure, and post-closure, which includes waste and engineered barriers, the geosphere/natural barriers, and the biosphere and surface environment. The safety assessment entails a pre-closure safety analysis, a post-closure performance assessment, and confidence enhancement analyses. This paper outlines the assessment basis and safety assessment aspects of a deep borehole disposal safety case. The safety case presented here is specific to deep borehole disposal of Cs and Sr capsules, but is generally applicable to other waste forms, such as spent nuclear fuel. The safety assessments for pre-closure and post-closure are briefly summarized from other sources; key issues for confidence enhancement are described in greater detail. These confidence enhancement analyses require building the technical basis for geologically old, reducing, highly saline brines at the depth of waste emplacement, and using reactive-transport codes to predict their movement in post-closure. The development and emplacement of borehole seals above the waste emplacement zone is also important to confidence enhancement. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

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28 pages, 2311 KiB

Open AccessArticle

Disposal of High-Level Nuclear Waste in Deep Horizontal Drillholes

by Richard A. Muller, Stefan Finsterle, John Grimsich, Rod Baltzer, Elizabeth A. Muller, James W. Rector, Joe Payer and John Apps

Energies 2019, 12(11), 2052; https://doi.org/10.3390/en12112052 - 29 May 2019

Cited by 21 | Viewed by 9019

Abstract

Spent nuclear fuel and high-level radioactive waste can be disposed in deep horizontal drillholes in sedimentary, metamorphic or igneous rocks. Horizontal drillhole disposal has safety, operational and economic benefits: the repository is deep in the brine-saturated zone far below aquifers in a reducing environment of formations that can be shown to have been isolated from the surface for exceedingly long times; its depth provides safety against inadvertent intrusion, earthquakes and near-surface perturbations; it can be placed close to the reactors and interim storage facilities, minimizing transportation; disposal costs per ton of waste can be kept substantially lower than for mined repositories by its smaller size, reduced infrastructure needs and staged implementation; and, if desired, the waste could be retrieved using “fishing” technology. In the proposed disposal concept, corrosion-resistant canisters containing unmodified fuel assemblies from commercial reactors would be placed end-to-end in up to 50 cm diameter horizontal drillholes, a configuration that reduces mechanical stresses and keeps the temperatures below the boiling point of the brine. Other high-level wastes, such as capsules containing ¹³⁷Cs and ⁹⁰Sr, can be disposed in small-diameter horizontal drillholes. We provide an overview of this novel disposal concept and its technology, discuss some of its safety aspects and compare it to mined repositories and the deep vertical borehole disposal concept. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

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15 pages, 2509 KiB

Open AccessEditor’s ChoiceArticle

Post-Closure Performance Assessment for Deep Borehole Disposal of Cs/Sr Capsules

by Geoff A. Freeze, Emily Stein and Patrick V. Brady

Energies 2019, 12(10), 1980; https://doi.org/10.3390/en12101980 - 23 May 2019

Cited by 6 | Viewed by 4061

Abstract

Post-closure performance assessment (PA) calculations suggest that deep borehole disposal of cesium (Cs)/strontium (Sr) capsules, a U.S. Department of Energy (DOE) waste form (WF), is safe, resulting in no releases to the biosphere over 10,000,000 years when the waste is placed in a 3–5 km deep waste disposal zone. The same is true when a hypothetical breach of a stuck waste package (WP) is assumed to occur at much shallower depths penetrated by through-going fractures. Cs and Sr retardation in the host rock is a key control over movement. Calculated borehole performance would be even stronger if credit was taken for the presence of the WP. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

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13 pages, 202 KiB

Open AccessEditor’s ChoiceArticle

Who Might Be Interested in a Deep Borehole Disposal Facility for Their Radioactive Waste?

by Neil A. Chapman

Energies 2019, 12(8), 1542; https://doi.org/10.3390/en12081542 - 24 Apr 2019

Cited by 20 | Viewed by 4205

Abstract

The deep borehole disposal (DBD) concept for certain types of radioactive wastes has been discussed for many decades, but has enjoyed limited R&D interest compared to ‘conventional’ geological disposal in an excavated repository at a few hundreds of metres depth. This article explores the circumstances under which a national waste management programme might wish to consider DBD. Starting with an assumption that further R&D will answer technical issues of DBD feasibility, it examines the types of waste that might be routed to borehole disposal and the strategic drivers that might make DBD attractive. The article concludes by identifying the types of national programme that might wish to pursue DBD further and the pre-requisites for them to give it serious consideration. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

17 pages, 3887 KiB

Open AccessArticle

Corrosion Performance of Engineered Barrier System in Deep Horizontal Drillholes

by Joe H. Payer, Stefan Finsterle, John A. Apps and Richard A. Muller

Energies 2019, 12(8), 1491; https://doi.org/10.3390/en12081491 - 19 Apr 2019

Cited by 12 | Viewed by 3384

Abstract

The disposal of spent nuclear fuel and other high-level radioactive waste in deep horizontal drillholes is an innovative system. Canisters of highly corrosion-resistant nickel-chromium-molybdenum (Ni-Cr-Mo) alloys are specified for the disposal of this nuclear waste. The canisters are emplaced along a steel casing in a horizontal drillhole that is one to three kilometers deep into or below a low-permeability geologic formation. The drillhole is in fully saturated rock with anoxic and reducing pore waters. A time-interval analysis method was used to track the evolution of the environment and to analyze corrosion performance of a representative engineered barrier system (EBS) configuration. In this analysis, the canisters remained perforation-free for tens of thousands of years. The amounts of hydrogen and metal oxides formed as by-products of the metal corrosion process were determined. These by-products are of interest, because both hydrogen and metal oxides can affect the chemical composition of the environment and the transport and sorption behavior of radionuclides and other species. Beneficial attributes that contribute to the extraordinarily long life of the canisters were identified. Several inherent characteristics of the horizontal drillhole disposal system reduced the complexities and uncertainties of the analysis. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

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23 pages, 4692 KiB

Open AccessArticle

Thermal Evolution near Heat-Generating Nuclear Waste Canisters Disposed in Horizontal Drillholes

by Stefan Finsterle, Richard A. Muller, Rod Baltzer, Joe Payer and James W. Rector

Energies 2019, 12(4), 596; https://doi.org/10.3390/en12040596 - 13 Feb 2019

Cited by 24 | Viewed by 4235

Abstract

We consider the disposal of spent nuclear fuel and high-level radioactive waste in horizontal holes drilled into deep, low-permeable geologic formations using directional drilling technology. Residual decay heat emanating from these waste forms leads to temperature increases within the drillhole and the surrounding host rock. The spacing of waste canisters and the configuration of the various barrier components within the horizontal drillhole can be designed such that the maximum temperatures remain below limits that are set for each element of the engineered and natural repository system. We present design calculations that examine the thermal evolution around heat-generating waste for a wide range of material properties and disposal configurations. Moreover, we evaluate alternative layouts of a monitoring system to be part of an in situ heater test that helps determine the thermal properties of the as-built repository system. A data-worth analysis is performed to ensure that sufficient information will be collected during the heater test so that subsequent model predictions of the thermal evolution around horizontal deposition holes will reliably estimate the maximum temperatures in the drillhole. The simulations demonstrate that the proposed drillhole disposal strategy can be flexibly designed to ensure dissipation of the heat generated by decaying nuclear waste. Moreover, an in situ heater test can provide the relevant data needed to develop a reliable prediction model of repository performance under as-built conditions. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

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Review

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15 pages, 1885 KiB

Open AccessReview

Status of Deep Borehole Disposal of High-Level Radioactive Waste in Germany

by Guido Bracke, Wolfram Kudla and Tino Rosenzweig

Energies 2019, 12(13), 2580; https://doi.org/10.3390/en12132580 - 04 Jul 2019

Cited by 14 | Viewed by 3268

Abstract

The phase-out of nuclear energy in Germany will take place in 2022. A site for final disposal of high-level radioactive waste (HLRW) has not yet been chosen, but a site selection process was restarted by the Site Selection Act in 2017. This Act was based on a recommendation by a commission which also advised to follow up the development of deep borehole disposal (DBD) as a possible option for final disposal of HLRW. This paper describes briefly the status of DBD in Germany and if this option is to be pursued in Germany. Although DBD has some merits, it can only be a real option if supported by research and development. The technical equipment for larger boreholes of the required size will only be developed if there is funding and a feasibility test. Furthermore, any DBD concept must be detailed further, and some requirements of the Act must be reconsidered. Therefore, the support of DBD will likely remain at a low level if there are no political changes. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

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15 pages, 262 KiB

Open AccessReview

A Review of Potential Cementing Systems for Sealing and Support Matrices in Deep Borehole Disposal of Radioactive Waste

by Nicholas Charles Collier, Neil Brennan Milestone and Karl Patrick Travis

Energies 2019, 12(12), 2393; https://doi.org/10.3390/en12122393 - 21 Jun 2019

Cited by 9 | Viewed by 2984

Abstract

Cementitious grouts are being developed for use as sealing and support matrices (SSMs) in deep borehole disposal (DBD) where temperatures do not exceed 190 °C. They will seal radioactive waste containers into the bottom 2 km of holes drilled up to 5 km deep into the crystalline basement. The temperature and pressure is likely to be similar to those in hydrocarbon and geothermal energy wells, where grout placement and durability are affected. This paper reviews the potential cementing systems suitable for this application and explains why a single solution of a formulation of Class G oil well cement, silica flour, water, fluid loss additive, and retarding admixture has been selected. This type of formulation has been used extensively for over 100 years in well cementing. It should provide the short-term performance and durability required for an SSM, maintaining the seal around the waste packages within the disposal zone long after the boreholes are sealed back to the surface, and thus augmenting the safety case for DBD. Full article

(This article belongs to the Special Issue Deep Borehole Disposal of Nuclear Waste)

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