Geological Repositories: Scientific Priorities and Potential High-Technology Transfer from the Space and Physics Sectors

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Mineralogical Magazine, November 2015, Vol. 79(6), pp. 1651–1664

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Geological repositories: scientific priorities and potential high-technology transfer from the space and physics sectors

1 2 1 3 2 4 SUSANA O. L. DIREITO ,SAMANTHA CLARK ,CLAIRE COUSINS ,YOSHIKO FUJITA ,JON GLUYAS ,SIMON HARLEY , 5 6 5 7 4 4 RICHARD J. HOLMES ,IAN B. HUTCHINSON ,VITALY A. KUDRYAVTSEV ,JON LLOYD ,IAN G. MAIN ,MARK NAY LO R , 1 8,9 5 5 5 10 SAM PAYLER ,NICK SMITH ,NEIL J.C. SPOONER ,SAM TELFER ,LEE F. T HOMPSON ,KATINKA WOUTERS , 11 1,* JOANNA WRAGG AND CHARLES COCKELL 1 UK Centre for Astrobiology, SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, Midlothian, Scotland 2 Department of Earth Sciences, Centre for Research into Earth Energy Systems, Durham University, Durham DH1 3LE, UK 3 Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark 4 School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW, Scotland 5 Department of Physics and Astronomy, The University of Sheffield, Houndsfield Road, Sheffield S3 7RH, UK 6 Space Research Centre, Department of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK 7 School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK 8 School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK 9 National Nuclear Laboratory, Chadwick House, Birchwood Park, Warrington WA3 6AE, UK 10 Microbiology Unit, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre SCK•CEN, Mol, Belgium 11 British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK

ABSTRACT

The use of underground geological repositories, such as in radioactive waste disposal (RWD) and in carbon capture (widely known as Carbon Capture and Storage; CCS), constitutes a key environmental priority for the 21st century. Based on the identification of key scientific questions relating to the geophysics, geochemistry and geobiology of geodisposal of wastes, this paper describes the possibility of technology transfer from high-technology areas of the space exploration sector, including astrobiology, planetary sciences, astronomy, and also particle and nuclear physics, into geodisposal. Synergies exist between high technology used in the space sector and in the characterization of underground environments such as repositories, because of common objectives with respect to instrument miniaturization, low power requirements, durability under extreme conditions (in temperature and mechanical loads) and operation in remote or otherwise difficult to access environments.

K EYWORDS: carbon dioxide, CCS (Carbon Capture and Storage), climate change mitigation, geological disposal, geological repositories, radioactive waste disposal (RWD), space sector, technology transfer.

* E-mail:[email protected] DOI: 10.1180/minmag.2015.079.6.41

The publication of this research has been funded by the European Union’s European Atomic Energy Community’s (Euratom) Seventh Framework programme FP7 (2007–2013) under grant agreements n°249396, SecIGD, and n°323260, SecIGD2.

Introduction the atmosphere and the hydrosphere in the deep underground, confined by geological substrates/ THE disposal of radioactive waste from nuclear strata/formations is thus currently the favoured applications (e.g. from the nuclear power industry, approach (Long and Ewing, 2004; Toth, 2011). nuclear weapons, medical applications and research There are a number of challenges to be addressed programs) is currently an environmental concern that relate to the physical, geochemical and worldwide. According to the International Atomic biological processes that might occur in repository Energy Agency’s (IAEA) 2007 report, the world- sites worldwide. These challenges apply to either or wide amount of spent fuel mass (of heavy metal) is both RWD and CCS, and any other use of the ∼18 × 107 kg and 1 × 107 kg are produced per year subsurface for geodisposal. In order to evaluate (International Atomic Energy Agency, 2007). The plans for geological disposal of different types of leading option to address this problem is the waste, and to gather sufficient information to make construction of long-term (i.e. over tens of thousands the case compelling, it is necessary that the of years) subsurface geological repositories for the geophysical, geochemical and geobiological pro- management of these wastes (Long and Ewing, cesses that occur within the subsurface, and that 2004). According to the glossary of the U.S. Nuclear might influence the long-term fate of the waste are Regulatory Commission (NRC), the definition of a understood thoroughly. geological repository is: “An excavated, under- One of the important challenges is to identify ground facility that is designed, constructed, and technology transfer areas that could facilitate operated for safe and secure permanent disposal of geological repository site selection, construction high-level radioactive waste. A geological repository and monitoring. Many of the problems faced in uses an engineered barrier system and a portion of building and maintaining such facilities have the site’s natural geology, hydrology, and geochem- similarities to technology requirements in studying ical systems to isolate the radioactivity of the waste” the physics, chemistry and biology of any extreme (NUREG-1350, 2013). For radioactive waste dis- environment, and in particular environments posal (RWD), a multiple barrier approach is encountered during space exploration. preferable given the difficulty in predicting the Repository monitoring is one need, which performance of a geological repository over very could potentially benefit significantly from tech- long time frames (Toth, 2011), and it is critical that nology transfer. Monitoring could provide rele- the engineered barriers work together with the vant information during all stages of repository natural environment for isolation and containment development and maintenance, including during: (Vines and Beard, 2012). (1) surface exploration of the repository site; (2) Another class of geological repositories are access just prior to construction or exploratory those which are intended to safely and effectively drilling and underground exploration; (3) con- store carbon dioxide (CO2) gas (Carbon Capture struction or expansion of the repository; (4) and Storage; CCS). CCS repositories can be emplacement (for RWD) or injection (for CCS) located in depleted gas fields (Jenkins et al., of the waste; (5) disposal tunnel backfilling (for 2012), depleted hydrocarbon fields, deep saline RWD) or injection well plugging (for CCS); (6) aquifers and coal seams (Rütters and CGS backfilling and the sealing of the repository; and Europe partners, 2013). However, repositories possibly (7) the long post-closure period. In the can also be located away from potential resources case of RWD, monitoring is required to ensure and therefore they are less well characterized. the stability of nuclear safeguards. The European Depleted oil and gas reservoirs have an estimated Commission has funded a collaborative project storage capacity of ∼675–900 GtCO2 (giga- (MoDeRn – Monitoring Developments for safe tonnes of CO2), deep saline formations Repository operation and staged closure; Solente ∼1000 GtCO2 or an order of magnitude higher and et al., 2013), for developing and possibly uneconomical coal formations ∼3–200 GtCO2 implementing monitoring activities during rele- (Benson and Cook, 2005). These are globally vant phases of the RWD process (site character- significant amounts of CO2, and highlight the ization, construction, operation and staged potentially important role of geological repositories closure, and post-closure control phase). in addressing one of the major environmental Therefore, it is timely to review the potentially challenges of the 21st Century: climate change. promising areas of technology transfer from space Burying waste far from populated areas exploration and particle and nuclear physics (although this is often not possible), the biosphere, sectors.

1652 GEOLOGICAL REPOSITORIES: HIGH-TECH TRANSFER

Science priorities and technology transfer repositories in environments where synergies opportunities between both applications can be developed.

The establishment of geological repositories is a huge area in which a vast concentration of research Geophysics and technology development has occurred (e.g. Benson and Cook, 2005; Birkholzer et al., 2012; Robust knowledge of the geophysical and/or of Scott et al., 2013). In order to evaluate how the geomechanical context of a repository site is technologies developed for the space sector can essential to understanding mechanical, hydraulic, advance the scientific understanding needed for thermal and other physical processes (e.g. geological repository siting and operation, it is first formation and propagation of fractures, tempera- necessary to identify some of the key science ture-induced effects in relation to heat-generating questions that need to be answered. This paper does waste, swelling/sealing of clays) and other related not attempt to provide an exhaustive list of science facets like geochemistry and geobiology. Indeed, questions, but instead identifies some of the high the geochemistry of a repository site and the way priority areas in geological disposal that could in which the chemistry interacts with the benefit from tools and approaches developed in subsurface biota are constrained by the physical high-technology areas such as the space sector. characteristics of the environment. Key questions Science questions under the themes of geophysics, specific to geological repository siting and geochemistry and geobiology are reviewed, and monitoring include: potential technology transfer options are consid- (1) How can we accurately understand and monitor ered, noting that many of them could promote stress fields, before, during and after repository scientific advances under all three themes. These construction? This work is important for science areas and their potential for technology understanding how the geological repository transfer were identified by GeoRepNet (Geological environment will evolve over time and potentially Repositories Network), a three year UK Science identifying, and even forecasting, points of and Technology Facilities Council (STFC) network weakness. Examples of techniques currently used set up to investigate potential high-technology in carbon capture include the measurement of transfer into geological repositories. subsurface pressure, time-lapse 3D seismic The focus of this paper is on technologies that imaging, vertical seismic profiling and crosswell can be transferred from the particle and nuclear seismic imaging, passive seismic monitoring, land physics sector and, in particular, from the space surface deformation using interferometry and GPS, sector to tackle the prioritized science questions visible and infrared imaging from satellite or planes (Table 1). Space instrument engineers are dedicated (Benson and Cook, 2005). Most of these techniques to a number of specific aims in instrument require periodic mobilization of resources for repeat development including miniaturization, low surveys. Such episodic surveys conducted over time energy requirements, long-term operation and scales of tens of years are expensive (especially on- operation under extreme conditions and in difficult shore seismic surveys) and their results are affected to access locations (e.g. on the surfaces of other by environmental conditions not necessarily linked planetary bodies). Similar conditions and con- to the monitored parameters. straints are encountered in geological repository (2) Have we identified and understood the environments and thus it seems likely that some of uncertainties and do we have confidence in the these technologies and instrument strategies could results? Mapping subsurface geology and its be adapted with appropriate modifications, for use geophysical/geomechanical properties has inherent in the monitoring of geological repositories during uncertainties. Characterizing these uncertainties is construction and post-closure. essential to predicting the behaviour of a repository, There are also a range of facilities, such as particularly in the long-term post-closure and yet synchrotron sources and deep underground labora- carrying out this characterization of uncertainties tories that could potentially play a role in testing remains in its infancy. The level of uncertainty technology transfer in all three areas discussed. The varies between different locations, classes and type access to deep subsurface environments, such as of repository (RWD or CCS), for example there is underground laboratories, offers the potential to test only limited experience in identifying and locating technology appropriate for both planetary explor- sites suitable for CCS beyond the regional scale ation/high-technology physics and geological (e.g. for saline aquifers) (Wilkinson et al., 2013).

1653 TABLE 1. Major technology challenges on geological repositories and possible technology transfer from space technology, missions and other physics areas.

Major technical challenge Instrument/ Mission/ Space Technology reports/ Official (number in text) Agency Mission status Description of instrument(s) References webpages

Geophysics (1) Monitoring of stress SEIS seismic instrument/ In development Insight will carry three instruments Trebi-Ollennu et al. http://insight.jpl.nasa.gov//docs/ fields/ Seismic InSight (Interior (planned launch: in order to explore Mars’ interior: (2013) InSight_NASA_fact_sheet_ rev3_ monitoring Exploration using Seismic March 2016) its internal seismic activity (SEIS June_2013_FC.pdf Investigations, Geodesy seismic instrument), geothermal and Heat Transport) heat (HP3 heat-flow and physical lander/ NASA properties probe) and rotational variations (RISE X-band radio Doppler tracking experiment). MoonLITE (Moon In development Will demonstrate communications Davies et al. (2007); — Lightweight Interior and and navigation technologies Gao et al. (2008) Telecoms Experiment) directed at supporting future UAAO .DIREITO L. O. SUSANA orbiter/ UK Space Agency missions and will place four one- metre-long penetrators into the lunar surface in order to establish a global network of seismometers, heat flow sensors 1654 and volatile detectors to investigate the seismic environment and interior of the Moon. (2) Mapping subsurface CheMin – Chemistry and Current mission Comprises a powder X-ray Blake et al. (2012); http://msl-scicorner.jpl.nasa.gov/ geology and its Mineralogy instrument/ (launched: Nov., diffraction (XRD) and an X-ray Zimmerman et al. Instruments/CheMin/ AL ET geophysical properties Mars Science Laboratory 2011) fluorescence (XRF) instrument in (2013)

(MSL) Curiosity rover/ order to determine the . NASA mineralogical and chemical composition of Martian rocks and soils. Raman Laser Spectrometer Future mission (planned A compact Raman spectrometer Edwards et al. http://exploration.esa.int/mars/ (RLS)/ ExoMars rover/ launch: 2018) that will perform Raman (2012); Lopez- 45103-rover-instruments/? ESA and Roscosmos spectroscopy on crushed Reyes et al. fbodylongid=2130 powdered samples inside the (2013) rover in order to establish mineralogical composition and identify organic pigments. MARSIS – Mars Advanced Past mission (launched: A subsurface radar sounder with a Mouginot et al. On Mars Express: www.esa.int/ Radar for Subsurface and June 2003) 40 m antenna which has been (2012) esapub/sp/sp1240/sp1240web.pdf Ionosphere Sounding collecting data from the instrument/ Mars Express subsurface with the aim of orbiter/ ESA searching for water. MARSIS provided strong evidence for a former ocean on Mars. WISDOM – Water Ice and Future mission (planned An UHF (frequency range from Ciarletti et al. http://exploration.esa.int/mars/ Subsurface Deposit launch: 2018) 500 MHz to 3 GHz) ground- (2011) 45103-rover-instruments/? Observation On Mars penetrating radar to characterize fbodylongid=2128 instrument/ ExoMars the stratigraphy under the rover rover/ ESA and and to be used in combination Roscosmos with Adron; this can provide information on subsurface water content, to choose where to collect subsurface samples. Muon tomography First tests for geological Detectors of cosmic-ray muons Kudryavtsev et al. https://www.dur.ac.uk/dei/projects/ repository monitoring capable of measuring muon (2012) muon/ are in progress angular distribution beneath a

geological repository and TRANSFER HIGH-TECH REPOSITORIES: GEOLOGICAL compare it with predictions. Long-term measurements would allow us to monitor changes in density profile above the muon detector. (3) Movement, transport MOMA – Mars Organics Future mission (planned Has two complementary Evans-Nguyen et al. http://exploration.esa.int/mars/ and speciation of gases Molecule Analyser launch: 2018) operational modes: Gas (2008); 45103-rover-instruments/? instrument/ ExoMars Chromatograph-Mass Brinckerhoff fbodylongid=2132 rover/ ESA and Spectrometry (GC-MS) to et al. (2013) Roscosmos identify and analyse volatile

1655 molecules and Laser Desorption- Mass Spectrometry (LD-MS) to analyse less volatile molecules and heat-resistant materials. Modulus Ptolemy Current mission Modulus Ptolemy Evolved Gas Todd et al. (2007) http://sci.esa.int/rosetta/47366-fact- instrument/ Rosetta lander/ (launched 2004) Analyser instrument on board sheet/ ESA Rosetta (ESA mission to characterize the comet 67 P/ Churyumov-Gerasimenko) includes a miniaturized GC/MS system with an ion trap mass spectrometer particularly developed for isotope ratio measurements of solid and volatile materials. SAM – Sample Analysis at Current mission Comprises a set of three Atreya et al. (2013); On MSL: http://marsprogram.jpl. Mars instrument/ Mars (launched: Nov., instruments: a gas Leshin et al. nasa.gov/msl/news/pdfs/MSL_ Science Laboratory (MSL) 2011) chromatograph, a quadrupole (2013); Ming Fact_Sheet.pdf Curiosity rover/ NASA mass spectrometer and a tunable et al. (2014); laser spectrometer, in order to Wong et al. look for and measure the (2013) abundances of carbon, oxygen, hydrogen and nitrogen elements associated with life. (continued) TABLE 1. (contd.)

Major technical challenge Instrument/ Mission/ Space Technology reports/ Official (number in text) Agency Mission status Description of instrument(s) References webpages

LADEE (Lunar Atmosphere Ongoing mission, on To collect detailed information on Stubbs et al. (2010); http://www.nasa.gov/sites/default/ and Dust Environment science analysis stage the conditions near the lunar Sarantos et al. files/ladee-fact-sheet-20130129. Explorer) lander/ NASA after a controlled surface, atmosphere and (2012); pdf impact on the lunar environmental influences on Lakdawalla surface (launched: lunar dust. Onboard: Ultraviolet (2013) Sept. 6, 2013). and Visible Light Spectrometer (to determine the composition of the lunar atmosphere), Neutral Mass Spectrometer (to measure variations in the lunar atmosphere

over several lunar orbits), Lunar DIREITO L. O. SUSANA Dust Experiment (to collect and analyse samples of lunar dust) and Lunar Laser Communications Demonstration (for technology demonstration). 1656 Geochemistry (1) Mapping/ Monitoring CLUPI – CLose-UP Imager/ Future mission: A miniaturized camera system that Josset et al. (2012) http://www.space-x.eu/index.php? of chemical processes ExoMars rover/ ESA and Exomars, (planned will acquire high-resolution option=com_content&view= for modelling Roscosmos launch: 2018) colour close-up images of rocks, article&id=116&Itemid=56 outcrops, drill fines and drill core samples from 2 metres depth. AL ET PanCam - Panoramic Future mission: Stereo, multispectral wide angle Coates et al. (2012); http://exploration.esa.int/mars/

Camera/ ExoMars rover/ Exomars, (planned and high-resolution camera Cousins et al. 45103-rover-instruments/? . ESA and Roscosmos launch: 2018) which will provide contextual (2012); Yuen fbodylongid=2127 geological data through (1) et al. (2013) digital terrain mapping of the Martian surface by capturing wide angle stereo imagery, (2) acquiring multispectral (440– 1000 nm) images for the identification of mineralogically- distinct units and (3) acquiring high-resolution images of distant targets. It is comprised of two Wide Angle Cameras (WACs) and one High-Resolution Camera (HRC). MoonLITE* See above See above See above See above (2) Effects of impurities SAM* See above See above See above See above on geochemistry (3,4) Detection of leakage Mars chamber simulating Ground based Different kinds of Mars-simulating de Vera et al. — of CO2, radionuclides CO2 atmosphere and other chambers have been built over (2014); Sobrado and other gases that simulation chambers the years in order to simulate et al. (2014) could be indicative of Mars surface conditions. subsurface repository TGO – Trace Gas Orbiter Future mission: To detect methane and other Korablev et al. http://exploration.esa.int/mars/ change or leakage instrument/ ExoMars/ Exomars, (planned atmospheric gases that are present (2013) 46475-trace-gas-orbiter/ ESA and Roscosmos launch: 2016) in small atmospheric concentrations (<1%) on Mars. Includes the ACS (Atmospheric Chemistry Suite) which is a set of three spectrometers, covering a TRANSFER HIGH-TECH REPOSITORIES: GEOLOGICAL total range of 0.7–17 μm. CheMin* See above See above See above See above SAM* See above See above See above See above LADEE* See above See above See above See above Geobiology (1) Knowledge on SOLID – Signs Of LIfe Future mission (launch: An antibody microarray-based Parro et al. (2005); — subsurface microbial Detector/ Icebreaker Life 2018) instrument capable of including Stoker et al. communities Lander/ NASA up to 500 different antibodies for (2008); Parro the detection and identification of et al. (2011) microbes and biological 1657 compounds (e.g. proteins, polysaccharides, nucleic acids) by in situ analysis of solid (soil, sediments, crushed rocks or ice) and liquid samples. SOLID version 3.1 is a portable field instrument. LMC – Life Marker Chip, Potential for future life Microfluidic antibody- based Sims et al. (2012); http://robots.open.ac.uk/space/LMC. withdrawn from ExoMars detection missions instrument that uses surfactant- Sephton et al. html rover/ ESA and based solvents to extract organic (2013) Roscosmos compounds from samples of soil or crushed rock and to transfer the extracts to the detectors. Raman Laser Spectrometer See above See above See above See above (RLS)* SAM* See above See above See above See above (2) Better understanding SAM* See above See above See above See above of the disturbance on the ecology of deep repositories (3) Gases generated by TGO – Trace Gas Orbiter See above See above See above See above microbial metabolisms instrument* (continued) TABLE 1. (contd.)

Major technical challenge Instrument/ Mission/ Space Technology reports/ Official (number in text) Agency Mission status Description of instrument(s) References webpages

(6) Finding analogue ——Terrestrial analogue studies support Preston and Dartnell — environments most planetary missions and their (2014); Fairen use is essential for exploratory et al. (2010) missions. In the same way, analogue environments that in some way approximate to the geological repository environment should be considered. General monitoring Automatic sampling/ Icebreaker Life Lander/ Mars Future mission (launch: It will search for life in ice-rich Dave et al. (2013); — Robotics Icebreaker Life Mission/ 2018) regions on Mars carrying life- McKay et al.

NASA detection instruments, 0.5–5m (2013); Zacny DIREITO L. O. SUSANA automated rotary and rotary- et al. (2013); percussive drills (tested Glass et al. successfully in analogue field (2014) sites and Mars chambers and to 1–3 m depths) and a triple 1658 redundant sample delivery system. Radiation monitoring Radiation Assessment Current mission It is one of the first instruments sent Ehresmann et al. http://mars.jpl.nasa.gov/msl/mission/ Detector instrument (launched: Nov., to Mars in preparation for future (2014) instruments/radiationdetectors/rad/ (RAD)/ Curiosity Rover/ 2011) human exploratory missions. TAL ET NASA Capable of measuring all high- energy radiation on Mars’ surface (e.g. protons, energetic ions, . neutrons and gamma rays). Gamma-ray and neutron Extensive R&D efforts Work on improvements of detection – http://www.hep.shef.ac.uk/research/ detectors, radon efficiency for gamma-rays and applied.php measurements neutrons at 0.1–10 MeVenergies, typical for radioactivity. Development of new neutron detectors that do not use very expensive and rare He-3 gas

*Described previously GEOLOGICAL REPOSITORIES: HIGH-TECH TRANSFER

(3) What are the transport characteristics, fluxes techniques, they have a clear advantage of and speciation of gases in environments with less providing a continuous monitoring capability and than 1 km depth of relevance to geological possibly a significant saving on resources over a repositories? This question relates to the natural long time period. environment in and around geological repositories, Another non-intrusive technique used in the space but also the influence of perturbation during exploration sector but with potential for use in construction, operation and closure. In particular, geological repositories is Ground Penetrating Radar the way the subsurface structural characteristics (GPR). Depth of penetration is strongly influenced either facilitate or mitigate against the transport of by the subsurface substrate and presence of ice/water gases within the repository is relevant. and salinity levels, but typically can be tens of (4) Is the aim detection or quantification? For metres. An example of a GPR system applied in example, in CCS, technologies that are sensitive to space exploration is the WISDOM (Water Ice and detecting the presence of CO2 are not necessarily the Subsurface Deposit Observation On Mars) instru- best technologies for quantifying spatially variable ment on the planned ExoMars rover (ESA and saturation. In practice, early detection of unintended Roscosmos) (Ciarletti et al., 2011), which can migration of CO2 may enable mitigating activities to penetrate up to 3 metres with cm-scale resolution. be undertaken, whereas quantification is important Such high-resolution subsurface analysis can be for calculating a mass balance and imposing financial applied to monitoring the near-surface environment penalties that are dependent upon the amount of CO2 above a repository, particularly within terrains that that escapes. While for RWD in almost any geology/ would benefit from a miniaturized, low-power GPR. geological environment, no leakage is achievable The MARSIS (Mars Advanced Radar for with appropriate, often costly, engineering. Subsurface and Ionosphere Sounding) instrument on ESA’s Mars Express orbiter (Mouginot et al., Geophysics: technology transfer opportunities 2012) (Table 1) also employs GPR technology and was originally designed to probe the ice-rich polar A fundamental requirement for improving model layered deposits up to four kilometres and up to capabilities, confidence in the results and in several hundred metres in other lithic environments particular improving the modelling of gas flow of Mars. Therefore this technology can also be through the subsurface is high-resolution data to applied in the identification of deep repositories. categorize rock mass heterogeneities. Miniaturized, portable, low-power sensor technologies developed for space applications, which include X-ray Geochemistry diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) During the establishment of geological repositories, offer particular promise for on-site characterization the local geochemical environment is perturbed. of mineralogical heterogeneity of representative Some changes may be transient, but there may be samples of the stratigraphy comprising and sur- long-term effects of the intervention of humans within rounding the repository, which might provide data the geological environment. For example, permanent and understanding to underpin models. Examples changes to subsurface hydrology/groundwater flow of possible technology transfer from space tech- regimes associated with repository construction (e.g. nology are given in Table 1. installation of low permeability walls) may lead to Non-intrusive techniques can also be developed changes in redox states of subsurface fluids and to allow characterization of the underlying geology. minerals, most likely on a local scale. Questions A promising technique belonging to the particle related to geochemistry that may be particularly and nuclear physics sector (muon tomography), is pertinent to geological repositories include: based on the observation of cosmic-ray muons, (1) How can we successfully obtain data that can be sub-atomic particles produced in collisions of high- used to support the development of improved models energy primary cosmic radiation with nuclei in the such as the modelling of pore space chemical and atmosphere, in the deep subsurface (Kudryavtsev physical processes and translate them to large-scale et al., 2012). This method allows for the mapping fate and transport models? To understand the likely of geological structures. Muon detectors can be fate of radionuclides or supercritical CO2 in the emplaced in the subsurface at different sites to subsurface, we require simulation approaches monitor geological repositories. Although they supported by in situ geochemical monitoring and may not be able to fully replace more conventional mapping.

1659 SUSANA O. L. DIREITO ET AL.

(2) What are the effects of impurities in the injected geological repository during construction and poten- CO2 streams (e.g. SOx, NOx, Hg in flue gas) on the tially post-closure, such as X-ray fluorescence (XRF) nature and rates of chemical reactions during (see Table 1 for examples of possible technology transport and injection, which would lead to transfer). mineralization and geologic sequestration of carbon? We require better parameterization of interactions of impurities with other molecules, Geobiology which is important to fully understand the groundwater chemistry and flow in deep systems Microorganisms are pervasive in the environment, (at repository depths). including the deep subsurface (e.g. Wouters et al., (3) In terms of storage security, what chemical 2013). Near geological repositories, a variety of reactions mobilize and immobilize CO2 (including microbial metabolisms may be involved in chan- dissolution, residual saturation and mineralization ging the chemical speciation of elements and their as well as microbial effects)? Once waste is mobility through the subsurface (Lloyd and contained it is necessary to monitor, long-term, the Renshaw, 2005; Krawczyk-Barsch et al., 2012), environment to determine whether waste is escaping or in affecting the performance engineered barriers, and what geochemical reactions determine the rate or in enhancing canister corrosion, concrete of escape. This requires a more in depth deterioration and the structure and performance of investigation of geochemical reactions occurring in bentonite buffer materials used in nuclear waste natural geological repository environments. disposal scenarios (Masurat et al., 2010; Pedersen, (4) Can we identify potential geochemical 2010), thereby affecting the performance of the signatures that could be used to indirectly engineered barriers and their functions (isolation indicate CO2 leakage (i.e. other than measuring and containment). Microorganisms and their activ- CO2 itself) or the leakage of radionuclides into the ity can also change the transport properties of the environment? During leakage of radioactive waste host rocks of interest e.g. formation of biofilms can or CO2, these substrates are likely to geochemically effect porosity (Coombs et al., 2010). Despite the modify the surrounding environment. Both small- growing and impressive understanding of micro- scale and large-scale monitoring methods can be biology in the deep subsurface and microbial used to detect potential geochemical alterations. interactions with radionuclides, several key questions for biological science related to geological Geochemistry: technology transfer repositories can be identified: opportunities (1) What are the main processes by which the microbial communities associated with different Technology transfer areas include methods for lithologies can influence RWD and CCS?Weneed detecting the migration of radionuclides, CO2 and to know more about subsurface microbial other gases that could be indicative of subsurface communities of geological materials at depth, and repository change or leakage, although time scale their dominant and potential metabolic pathways and may be an issue. Of particular interest are spectro- how these respond to the changes imposed in and scopy techniques (e.g. infrared spectroscopy, gas around a geological disposal facility. One way is to chromatography coupled with mass spectrometry link the study of geological repository environments (GC-MS), X-ray diffraction (XRD)) developed for more directly with international continental and planetary exploration and astronomy. Both of these oceanic deep drilling programmes and especially communities seek to develop small, low-energy, permanent deep subsurface laboratories where long- robust instruments with very high sensitivity, particu- term analysis of deep microbial communities can be larly when this instrumentation is being used to search accomplished. for trace gases such as methane at the ppt/ppb/ppm (2) How do activities during excavation, level (e.g. Formisano et al., 2004; Korablev et al., construction and operation inhibit or promote 2013). An example of such technology is the Tunable specific microbial processes? During different Laser Spectrometer (TLS) of the Sample Analysis at phases of the development of a repository, new Mars (SAM) suite of Curiosity rover used for the microbial inocula, interfaces and chemical species recent in situ methane detection on Mars (Webster are likely to be introduced, which are expected to et al., 2015). Other examples include technologies to affect the resident microbial communities and their measure low concentrations of elements and impur- metabolic pathways. For instance, the introduction ities in the groundwater and in materials around a of oxygen during drilling or excavation is expected

1660 GEOLOGICAL REPOSITORIES: HIGH-TECH TRANSFER to affect subsurface microbial consortia that were and in space? Microbial influences can be studied in previously based on anaerobic metabolisms such as the laboratory or, in cases where the subsurface can anaerobic respiration (iron and sulfate), fermentation be directly accessed, either by sample collection or methanogenesis. There is a need to better during initial drilling, in deep subsurface understand the impact of the disturbance laboratories, or during the construction of the associated with reservoir or repository construction geological repository itself. However, a crucial and active operation on the long term ecology of objective must be to understand possible future deep repository environments and associated interactions using improved modelling supported by implications for safe waste isolation. empirical microbiological data. For example, there Related to point (2) is a priority to better is a need to establish input values such as rates of understand how communities change after the metabolism for different redox couples for a given closure of the facility. Ideally one would monitor environment, and the rate of dispersal or transport of the evolving microbial community over time, metabolic products and organic matter throughout linking back to changes in geochemical and the subsurface medium. geophysical properties. Although permanent deep (6) Can analogue environments be found that are subsurface laboratories make such monitoring representative of a geological repository possible, such laboratory facilities are limited to environment? The use of modelling, laboratory specific sites for logistics and cost reasons. studies and in situ investigations will advance our Therefore, one obvious priority would be to understanding of microbial interactions in advance our capacity to quantify and predict geological repositories. However, one means to microbial dynamics across temporal and spatial achieve improved modelling and real-world data is scales, which is itself directly linked to improved to find easily accessible and representative analogue capacities for geochemical modelling. environments. One such environment is the Boulby (3) What are the effects of microbial presence and International Subsurface Astrobiology Laboratory activity on local geochemistry, integrity of the (BISAL) dedicated to astrobiology analogue repository and radionuclide transport? What are the research in the deep subsurface and for the testing exact roles of local microbial consortia in corrosion, of space technology and technology transfer into the as well as on microbial interactions with ground- mining environment at 1.1 km depth in the Boulby water chemistry or radionuclides? For example, there Mine (Yorkshire, UK) (Cockell et al., 2013). is knowledge on the capacity of deep microbial communities to produce or metabolize gases Geobiology: technology transfer opportunities (including those that are relevant for RWD safety assessments e.g. methane and hydrogen), but not These identified challenges can be consolidated much is known on intermediate and final gas mass under technological innovation objectives that can balances in a repository system and on the subsequent be accomplished with technology transfer from a effects on the local chemical processes. Also the variety of areas, including molecular biology biodegradation of naturally occurring or introduced approaches, such as methodologies for the produc- organic material and the organic matter derived from tion of metagenomic libraries and their archiving and dead microorganisms (Bassil et al., 2014) is expected analysis. One promising area of research from the to influence the local geochemistry. space sector that may find application to geological (4) What is the role of microbial biofilms in disposal repositories is the ‘lab on a chip’ technology such as systems? In RWD, microbial biofilms on engineered the Life Marker Chip (see Table 1), an instrument interfaces such as concrete and metal can harbour capable of recognizing small biomarker molecules strong chemical gradients which increase material by the use of an antibody-based detection system deterioration rates, and can interact with and developed for use on spacecraft (Sephton et al., radionuclides, changing geochemistry in a micro- 2013). This approach is a good example of a environment. In CCS scenarios, extensive biofilms portable/low-power microfluidics technology that is may interact with supercritical fluids. It is also not transferrable to the deep subsurface. In general, this clear how microbial biofilm development is technology allows rapid identification of individual triggered and maintained in undisturbed and microbes and screening for specific metabolisms and perturbed deep subsurface environments. metabolites that would allow for in situ analysis of (5) How can our current experiment-based microbial dynamics. understanding of microbial processes and their Other technologies, such as synchrotron spectro- effects be abstracted and up-scaled, both in time scopies offer the chance to better understand the

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interactions of microorganisms with radionuclides and Storage. Intergovernmental Panel on Climate and the secondary mineral products formed follow- Change special report. IPCC, Interlachen, ing these interactions. The possibility of examining Switzerland. these effects at small spatial scales, e.g. using new Birkholzer, J., Houseworth, J. and Tsang, C.-F. (2012) techniques such as STXM (scanning transmission Geologic disposal of high-level radioactive waste: X-ray microscope), allows for improved mechan- Status, key issues, and trends. Annual Review of – istic understandings of these interactions that could Environment and Resources, 37,79 106. be applied at the larger scale. Computational Blake, D. et al. (2012) Characterization and calibration of resources (possibly including all aspects of mod- the CheMin mineralogical instrument on Mars Science Laboratory. Space Science Reviews, 170, 341–399. elling and data analysis, processors, etc) from space Brinckerhoff, W.B. et al. (2013) Mars Organic Molecule physics and other areas could be mobilized to Analyzer (MOMA) mass spectrometer for ExoMars improve the ability to model microbial-ground- 2018 and beyond. Aerospace Conference, 2013 IEEE, water interactions over time, and predict the effects DOI: 10.1109/AERO.2013.6496942 of geological repository construction on geochem- Ciarletti, V., Corbel, C., Plettemeier, D., Cais, P., Clifford, ical and geobiological processes. S.M. and Hamran, S.E. (2011) WISDOM GPR designed for shallow and high-resolution sounding Concluding remarks of the Martian subsurface. Proceedings of the IEEE, 99, 824–836. This paper concludes with the observation that Coates, A.J. et al. (2012) Lunar PanCam: Adapting there are strong synergies between high-technology ExoMars PanCam for the ESA Lunar Lander. areas such as space sciences and particle physics Planetary and Space Science, 74, 247–253. and the development of geological repositories. Cockell, C.S., Payler, S., Paling, S., and McLuckie, D. (2013) These synergies primarily arise because: (1) all The Boulby International Subsurface Astrobiology – these groups seek to build miniature, reliable, low Laboratory. Astronomy & Geophysics, 54,2.25 2.27. energy, rugged instruments and (2) the scientific Coombs, P., Wagner, D., Bateman, K., Harrison, H., questions they address have similar technological Milodowski, A.E., Noy, D. and West, J.M. (2010) The role of biofilms in subsurface transport processes. solutions. Some concrete examples of these links Quarterly Journal of Engineering Geology and are summarized in Table 1. We recommend that a Hydrogeology, 43, 131–139. stronger effort be made to link science and Cousins, C.R., Gunn, M., Prosser, B.J., Barnes, D.P., technology requirements in the development of Crawford, I.A., Griffiths, A.D., Davis, L.E. and Coates, geological repositories to these high-technology A.J. (2012) Selecting the geology filter wavelengths communities and ultimately to pool expertise and for the ExoMars Panoramic Camera instrument. resources in the development of technology. Planetary and Space Science, 71,80–100. Dave, A. et al. (2013) The sample handling system for the Acknowledgements Mars Icebreaker Life Mission: From dirt to data. Astrobiology, 13, 354–369. GeoRepNet is funded by the Science and Technology Davies, P. et al. (2007) UK lunar science missions: Facilities Council (STFC) as a Futures Programme Moonlite & Moonraker. 3rd International Conference Global Challenge Network (Grant No. ST/K001736/1). on Recent Advances in Space Technologies, Vols. 1 J. Wragg publishes with permission of the Executive and 2, 774–779. Director of the British Geological Survey. de Vera, J.P., Dulai, S., Kereszturi, A., Koncz, L., Lorek, A., Mohlmann, D., Marschall, M. and Pocs, T. (2014) References Results on the survival of cryptobiotic cyanobacteria samples after exposure to Mars-like environmental Atreya, S.K. et al. (2013) Primordial argon isotope conditions. International Journal of Astrobiology, 13, fractionation in the atmosphere of Mars measured by 35–44. the SAM instrument on Curiosity and implications for Edwards, H.M., Hutchinson, I. and Ingley, R. (2012) The atmospheric loss. Geophysical Research Letters, 40, ExoMars Raman spectrometer and the identification 5605–5609. of biogeological spectroscopic signatures using a Bassil, N.M., Bryan, N. and Lloyd, J.R. (2014) Microbial flight-like prototype. Analytical and Bioanalytical degradation of isosaccharinic acid at high pH. ISME Chemistry, 404, 1723–1731. Journal, 9, 310–320. Ehresmann, B. et al. (2014) Charged particle spectra Benson, S.M. and Cook, P. (2005) Underground geo- obtained with the Mars Science Laboratory Radiation logical storage. Chapter 5 in: Carbon Dioxide Capture Assessment Detector (MSL/RAD) on the surface of

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