Colloidal Silica Introduced Colloidal Silica of Membrane
Preliminary studies of an advanced blind-tube apparatus for characterisation of underground sources
PhD student: Soraia Elisio (Engineering Department, Lancaster University) Academic supervisor: Malcolm J Joyce (Engineering Department, Lancaster University)
Industrial supervisors: James Graham (Central Laboratory, National Nuclear Laboratory Ltd.) Frank Cave (Hybrid Instruments Ltd.) Content
- The problem… - The challenge… 1. Infrastructure and deployment constraints 2. In-ground assets Current practice 3. Radiological
Soil sampling Groundwater sampling
Taken from Groundwater monitoring at Sellafield: Annual data review, 2016
Steel pipe Fluids Detector Radiometric logging probe
Sensing element
e.g. β Bremsstrahlung GM counter NaI:Tl γ HPGe CdZnTe
Signal conditioning e.g. Preamplifier
Signal processing e.g. Analog and Digital Pulse height analysis Visualisation of data
Counts versus depth Spectra display Gamma log at Maxey Flats site (Keys, 1997) Radiometric logging probe
Sensing element MSSS ퟗퟎ퐒퐫/ퟗퟎ퐘
Bremsstrahlung CeBr3 scintillation crystal Ø10 x 9 mm CeBr3 detector ퟏퟑퟕ퐂퐬 Commercialized by Scionix (Netherlands) Signal conditioning PM6660-SiPM 1. Good γ-ray detection efficiency + Preamplifier −3 푍푒푓푓 = 46 휌 = 5.2푔푐푚 2. Good energy resolution Signal processing 4 % @ 662 keV 3. High count-rate capability 휏 = 17 푛푠 Visualisation of data 4. High radiation hardness Counts versus depth Dose up to 100 kGy Spectra display Radiometric logging probe
Sensing element ퟗퟎ퐒퐫/ퟗퟎ퐘
Bremsstrahlung CeBr3 scintillation crystal ퟏퟑퟕ퐂퐬
Signal conditioning TOPAZ-SiPM digital MCA PM6660-SiPM Commercialized by BrightSpec NV + Preamplifier
Signal processing
Digitizer MCA
Visualisation of data bGAMMA Counts versus depth γ-ray spectroscopy software Spectra display Commercialized by BrightSpec NV The blind-tube test bed Ø7.5cm Ground content: Ø32cm W 1cm sand m
75 c 75 Source holder + plastic capsules:
h: 110 mm 28 mm 3. Plastic ‘void’ tube 4 1. Carbon steel tube 4. Plastic tubes to hold disk point sources mm 2.3 mm 2. Plastic sand retaining tube 5. Base support 4.4 Detector performance
5 V Power supply A. Preliminary desk studies:
A1. Spectral performance A2. Angular dependence of response A3. Detector response in practice of source holder (and capsules) use.
HV-supply C10940 MCA4
Voltage divider Hamamatsu E-10679-50
Ø 14 Photomultiplier Hamamatsu R9880-110 MPANT-MCA4 Software Ø 10 x 10 CeBr3 crystal 4 A1. Spectral performance
Experimental setup
energy resolution 5.2% @ 662 keV
photopeak efficiency 0.002% @ 662 keV
multiple peaks
4 A2. Angular dependence of response
Cs-137 (662 keV) Experimental setup 7
6.9
6.8
6.7
6.6
6.5 count rate (cps)rate count y = -1.7E-05x2 - 6.5E-04x + 6.8 6.4 R² = 0.6576
6.3 Cs-137 (32 keV) 13 12 11 10 9 8 7 count rate (cps)ratecount y = -0.0003x2 + 0.0015x + 10.7 D = 105 ± 2 mm 6 R² = 0.7625 5 -120 -90 -60 -30 0 30 60 90 120 4 θT (ͦ) + variation on peak position of about 2% A3. Practice with source holder + capsules
1.8 + variation on Experimental setup Empty capsules peak position of 1.6 Cs-137 (662 keV)
ln (cps) 1.4 3% y = (1.718±0.005) - (0.097±0.002)x 1.2 chi^2 = 2.5 2.5 Empty capsules 2 Cs-137 (32 keV) 10%
ln (cps) 1.5 y = (2.121±0.004) - (0.229±0.002)x chi^2 = 12.9 1 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 cm of plastic CeBr3 1.8 1.6 Sand-filled capsules 1.4 Cs-137 (662 keV) 1.2 50%
ln (cps)ln 1 0.8 y = (1.736±0.004) - (0.119±0.001)x chi^2 = 1.96 0.6 3 2 Sand-filled capsules 1 Cs-137 (32 keV) 0 20% y = (2.112±0.005) - (0.597±0.003)x ln (cps)ln -1 chi^2 = 36 -2 0 1 2 3 4 5 6 7 8 9 10 cm of plastic+sand Future work
A. Radiological tests ➢ Blind tube test bed Gamma-ray detection (Cs-137) ➢ High dose environment Bremsstrahlung detection (Sr-90)
B. Simulations Geant4 + C. Temperature dependence, waterproofing, vibration tests, etc
D. Extension of a single detector to a blind tube string network -> 3D underground mapping
1 m3 Tank soil PhD student Soraia Elisio e-mail : [email protected]
Thank you The Application of Electrokinetics for Remediation of Difficult to Measure Radionuclides
Shaun Hemming University of Southampton
TRANSCEND Theme Meeting 2 17/05/21 Sellafield, UK Hanford, USA
1 km 5 km
Groundwater Monitoring Annual Data Review 2016, Sellafield Ltd, 2017 Hanford Site Groundwater Monitoring Report for 2019, USDOE, 2020 Electrokinetics Experiments
Contaminants: Materials:
13 - • Sellafield sand • H CO3 • Sellafield sand + compost - - • I + IO3 barrier
• Sellafield sand + compost mix
• Sellafield GW Simulant
Cell pH Gradients Over Time 1.4
1.2
1.0
0.8
0.6
0.4
0.2 pH Difference Between Ends of Cell Ends of Between pH Difference 0.0 0 50 100 150 200 250 300 350 Time (hours)
C EK S I EK S C EK C I EK C C NEK S I NEK S C NEK M I NEK M C NEK C I NEK C Predictions:
• Sand only: nearly all carbon and iodine will migrate
• PRB and compost mix: all carbon will migrate but iodine migration will be more limited?
- • Carbon will exist primarily as HCO3 along with minor 2- component of CO3 and CO2
- - • Iodine will exist as both I and IO3 but the latter may be dominant at close proximity to the anode Next Steps
• Water sample analysis
• Sediment analysis
• Repeat experiments with a pH gradient present Transformative Science and Engineering for Nuclear Decommissioning
Any questions?
Contact Details
Assessing the strength of biomineral strategies for concrete repairs Thanos Karampourniotis, University of Strathclyde Theme 2: Site Decommissioning and Remediation email: [email protected]
Supervisors:
Professor Rebecca Lunn1 , Dr. Enrico Tubaldi2,Dr. Grainne El Mountassir3
1,2,3 Department of Civil and Environmental Engineering, Faculty of Engineering, University of Strathclyde, Glasgow, United Kingdom
17 May 2021 CONCRETE IN MODERN SOCIETY
What is concrete?
Concrete is a structural material consisting of a hard, chemically inert particulate substance, known as aggregate (usually sand and gravel), that is bonded together by cement and water. (Source: Britannica) Source: Znachor et al., 2016 Source: www.newatlas.com Name of Presenter,Slapy OrganisationReservoir, Czech Republic Wind Turbines, Gaildorf, Germany Why is it important? Meeting Title Approximately 4.4 billion tonnes of cement and 33 billion tonnes of concrete are produced each year, making concrete the second most consumed material in the world, after water. (Sources: Mehta and Monteiro, 2014 The American Society of Mechanical Engineers) Source: Jose Fuste Rago/Corbis Source: concreteconstruction.net
• Worldwide concrete production is estimated to be
responsible for 8.6% of all anthropogenic CO2 emissions. (Source: Miller et al., 2016)
• Global cement production is expected to rise from 4.4 billion tonnes to 5.5 billion in 2050 due to
further urbanization, increasing the amount of CO2 emissions. (Source: Chatham House, 2018)
A possible solution
More attention should be given to effectively repairing and maintaining the existing structures and infrastructure.
• Most of the UK’s nuclear power stations are decades old and in need of maintenance during the decommissioning process, to ensure both their safety and functionality. Presentation title • For instance, the Hunterston B and Hinkley Point B nuclear power stations in Scotland and England respectively, remain operationalName since of Presenter, Organisation 1976 and are scheduled for closure by 2023. Hunterston B nuclear power station, Scotland, Source: news.sky.com (Source: assets.publishing.service.gov.uk) Meeting Title
• The deterioration of concrete assets on these sites should be attended to effectively.
Hinkley Point B nuclear power station England, Source: world-nuclear- 17 May 2021 news.org TRADITIONAL CONCRETE-REPAIR MATERIALS Epoxy resins Cement mortar
• Epoxy resins have a much greater coefficient of • Cement mortar consists of big particle size grains, thermal expansion than concrete, something that can resulting in poor penetration, making it ineffective cause high shear stresses at the interface between when treating micro-cracking. the materials when temperature changes. As a result, cracks begin to form in the interface. Name of Presenter, Organisation • They need constant periodic care and maintenance, making them in many cases uneconomical. Meeting Title
Microbially Induced Carbonate Precipitation
A novel concrete repair method that takes advantage of the mineralization properties of certain types of bacteria like S. Pasteurii where together with a calcium source can form calcium carbonate (CaCO ) crystals on their surface. 3 Name of Presenter, Organisation CO(NH ) + 2H O → 2NH + H CO 2 2 2 3 2 3 Meeting Title + – 2NH3 + 2H2O ↔ 2NH4 + 2OH
– - – H2CO3 + 2OH ↔ HCO3 +H2O + OH
- - 2- HCO3 + H2O + OH ↔ CO3 + 2H2O
2+ 2- Ca + CO3 → CaCO3 (s) (calcite precipitation)
• Soil strengthening
• Sealing fractured rock
• Increasing fractured rock’s shearing resistance
• Leakage reductionName of from Presenter, carbon Organisation sequestration reservoirs Meeting Title • Permeability reduction
• Enhancing the compressive strength of cement mortar
AIM OBJECTIVES
• To repair concrete structures in nuclear sites so • To develop a modelling strategy, conduct that they are fully functional and safe for the experiments to validate it and show it can duration of the decommissioningNameprocess. of Presenter, Organisationpredict the mechanical behavior of MICP- treated concrete. Meeting Title • To optimize the repair strategy which is investigated.
Calcite crystals bridged the fracture after the MICP treatment was implemented
1) Vertical load on the top face of the half-core
2) Displacement rate on the second half-core Name of Presenter, Organisation 3) Horizontal fracture Meeting Title
4) Calcite distribution on half-cores’ surfaces
5) Displacement
Cohesive behavior assigned
FG2 Core: 0.50 MPa
FG4 Core: 0.73 MPa X-CT Image, FG2 64 elements 256 elements Core Model, FG2 Core Model, FG2 Core
Red elements:
Frictional behavior assigned
X-CT Image, FG4 64 elements 256 elements Core
FG2 Core FG4 Core
600 800 Experimental results Experimental results 500 700 FE model 256 elements 600 400 FE model 64 elements 500 FE model 64 elements 300 400 FE model 256 elements 300 200 Shear Stress [kPa] Stress Shear Shear Stress [kPa] Stress Shear 200
100 100 0 0 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2
DIFFERENT CALCITE
DISTRIBUTIONS 400
350 1 2 3
300
250 4 5 6 1 2 3 200 150
Reaction Force [N] Force Reaction 100
50
0 0 0.2 0.4 0.6 0.8 1 1.2 4 5 6 Horizontal Displacement [mm]
‘’Random distribution’’ of calcite ‘’Pillars distribution’’ of calcite models models 800 800 16 elements with cohesion 16 elements with 700 700 cohesion 600 600 36 elements with 500 36 elements with cohesion 500 cohesion 400 400 48 elements with 48 elements with cohesion 300 300 cohesion 200 200 Reaction Forces [N] Forces Reaction
Reaction Forces [N] Forces Reaction 100 100 0 0 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2 Horizontal Displacement [mm] Horizontal Displacement [mm]
0.5mm diameter glass beads on the half- core’s surface
The separated half-cores The half-cores wrapped together with
Rigid clear tube acting as core holder
1 2 2 3 After having the wrapped half-cores 15 minutes after having After removing the top layer immersed in colloidal silica introduced colloidal silica of membrane
• A Finite Elements Model has been developed and calibrated against experimental data.
• According to the sensitivity analyzes that took place, the model shows that there is relatively little effect on the geometry of the calcite and that strength is largely governed by the size of the contact area.
• Microbially Induced Carbonate Precipitation treatments will be implemented to old artificially-cut concrete cores and then subjected to shear tests to confirm the efficiency of the already developed Finite Elements Model.
• Concrete specimens with various fracture widths will be treated with MICP.
• Concrete specimens with rough (and thus closer to real condition cracking) rather than smooth fracture surfaces will be treated.
• The effect of the created flow paths due to the spatial distribution of calcite on the efficiency of the repair will be investigated.
• Different mechanical tests will be conducted to determine whether the same behavior will be observed.
Luke Lee-Brewin: [email protected] University of Surrey TRANSCEND Virtual Meeting
17/05/2021 Project Overview • Identify radioisotopes present within low SNR gamma signals
• Several Methods of Signal Analysis Explored:
o Wavelet Analysis
o Principal Component Analysis
o Neural Networks Wavelet Analysis Wavelet Analysis Analysis
Line 1: Line 2: Line 3: Line 4:
Energy: ~30-70 keV Energy: ~350 keV Energy: ~670 keV Energy: ~1450 keV
Source: Source: 152Eu left in Source: 137Cs left in Source: Background Background X-rays safe safe 40K Principal Component Analysis
• Algorithm designed to reduce dimensionality of a dataset
• Gamma spectra can be reduced to 2 or 3 “principal components” and analysed
• So far used to check quality of simulated datasets
• Can be used to identify isotopes – bad at multi-isotope identification without additional help Principal Component Analysis Neural Network Input: 1024 Hidden Hidden Output: 31 Layer 1: 660 Layer 2: 200
Neurons … … … …
Weights Neural Network
3 Gamma Spectrum 10.2 0.6 Correct Answer: 5 Each 0.1 137Cs 0 number of counts … in a 30 … channel … 60Co goes into … 1.2 1 1 neuron
1 Training Set: Resampling
137Cs 133Ba 60Co 241Am 22Na
18 Spectra 18 Spectra 18 Spectra 18 Spectra 18 Spectra Collected Collected Collected Collected Collected
137Cs + 133Ba 133Ba + 60Co 60Co + 241Am 241Am + 22Na
Initial set of 90 spectra are resampled into 6200
So far, 3 sets of 90 spectra have been created with different levels of shielding for 18600 spectra Isotopes:
Training Sets Testing Sets
Isotopes Activities / kBq Isotopes Activities / kBq
241Am 369.86 241Am 398.90
137Cs 129.77 137Cs 200.13
60Co 179.25 60Co 189.68
133Ba 219.52 133Ba 112.34
22Na 76.92 22Na 93.89 Testing Sets: 1. Different isotopes used with 3. Initially tested in same shielding different activities environments as training set
2. Fully experimental spectra, no 4. Finally, tested on new shielding resampling, all combinations environments to see how network collected handles new environments Results Lead Castle Accuracy: 96.77% (30/31) Shielding Size of Testing Set Accuracy
Lead Castle 31 96.77%
Lead Pot at 20cm 15 100.0%
20cm No shielding 31 100.0%
Lead Pot at 10cm 15 100.0%
Accuracy is measured as the percentage spectra the network has predicted with no false positives or negatives Conclusions
PCA Wavelets Neural Networks
• Good visualisation up to 3 • Excel at low signal to • Provides initial prediction dimensions noise ratio photopeak in easy to read format detection • Fast, basic analysis • Can be expanded to possible without expert • Struggles with provide confidence level knowledge overlapping peaks (at the in prediction and moment) recommend additional • New data can’t be added analysis once PCA has been • Expert knowledge performed required to read • Can be adapted to take in scaleogram wavelet or PCA data • Multi-isotope identification requires more than 3 dimensions Acknowledgements
Supervisors: Caroline Shenton-Taylor: [email protected], David Read: [email protected] Thank you
I would like to thank the Transcend consortium as well as Magnox Ltd. and NNL for funding and technical discussions supporting this study
[email protected] Modifying Colloidal Silica Grout for Nuclear Decommissioning Applications
David W T Morrison Dr Matteo Pedrotti, Dr Emily R Draper, Prof Rebecca J Lunn, Dr James Graham* Department of Civil and Environmental Engineering, University of Strathclyde *National Nuclear Laboratory, Sellafield, Cumbria TRANSCEND Theme 2 Meeting, 17th May 2021 Outline o Introduction • Hydraulic barriers in nuclear decommissioning • Permeation grouting • Colloidal silica grout • My project: chemically modifying colloidal silica o Background • What chemically is colloidal silica? • Modifying silica using polymers o Experiments on 3 polymers o Conclusion • Summary • Next steps
2 Introduction Hydraulic Barriers in Nuclear Decommissioning o At legacy nuclear sites, containment can be poor… • Contaminants in direct contact with soil - unlined trenches • Cement containment structures compromised over time o Employ sub-surface hydraulic barriers: • Shore up structures, secure contaminants • Conventionally clay-based, installed by excavation - expensive - Increases radiation exposure of workers - time consuming
• Can inject liquid grout instead…
3 Introduction Permeation Grouting o Permeation grouting • Low pressure injection of low viscosity grout to fill free ground porosity • Non-disruptive to ground
• Create vertical + horizontal barriers • Grout bulk space • Increases strength/density of soil - Resistance to compression, settling
Contaminated site 4 Introduction Colloidal Silica Grout
Colloidal silica permeation grout: o Water-like initial viscosity o Precisely controllable gel-time (mins to days) o Nano-scale particle size • Fill smallest fissures o Non-toxic, inert o Gel has extremely low hydraulic conductivity o Inexpensive • Comparable to concrete o Sorption of radionuclides (Cs-137, Sr-90) 5 Introduction My Project: Chemically Modifying Colloidal Silica o Colloidal silica – Highly promising permeation grouting material. • Can it do even more…?
Stretch o My project: chemically modify silica grout: • Further improve hydro-mechanical properties Original • Tailor for specific environments Cut • Open up to new applications - Encase waste containers for transport Heal on contact - Radiation shielding o Work so far: combining silica with polymers and polymer hydrogel • Super-materials from biomedicine
6 Background What is colloidal silica? o Suspension of silica nano-particles • Particles tend to stick together - Permanent chemical bonds form • Build up into a network => hydrogel o Particles have –ve charge that increases with pH • Solution kept at pH ~10 - Repulsion between particles sufficient to prevent gelation o Gelled by mixing with salt solution • +ve ions stick to silica particles • Screens –ve charge, allowing gelation
7 Background Colloidal Silica Gelation
Gelation adjustable using… - Silica concentration - Temperature - Ionic strength - pH
8 Background Polymer Hydrogels o Networks of hydrophilic polymers in water o Crosslinked through either… • Permanent chemical reaction Stretch • Transient physical interaction
o Used in biomedical research for: Original • Tissue engineering/replacement, cell scaffolding • Excellent, highly-customisable properties: Cut
- Super-strength - Re-healability Heal on - Super-flexibility contact 9 Background How to Combine Silica & Polymer Hydrogels o Need: • Simultaneous silica & polymer gelation • 2 independent, interpenetrating networks => a double network. o Must find a polymer gel which… • Doesn’t interfere with silica gelation • Is cheap • Gels in situ For permeation grouting: • Low enough initial viscosity for injection • Gels underground 10 Experimental
o Here, interesting polymer and silica/polymer o 3 candidate polymers investigated: hybrid gels are discussed • Polymer 1 o Gels produced by either… • Polymer 2 + crosslinker 1. Simply adding polymer to colloidal silica gel • Polymer 3 OR 2. Crosslinking the polymer into its own gel with colloidal silica present - Working towards a double-network
11 Experimental
Polymer 1 Control Low conc. High conc.
1. Adding polymer 1 to colloidal silica produces 2 gel variants depending on polymer concentration: Oven • Low conc. drying - Gives plasticity, mouldability. - Cracks heal upon applying pressure - White colour 60% - Rapid gelation 100 Gel time Water retention 80 • High conc. 55% 60 - Increased water retention 50% - Weakened structure 40 45%
Gel time (min) time Gel 20
- Delayed gelation 8 days after O loss 2 H 0 40% 0 1 2 3 4 5 0% 1% 2% 3% 4% 5% 6% 7% Polymer 1 mass % 12 Polymer 2 mass % Experimental Polymer 1
800 Effect of salt conc. 600 o Effect depends on pH + salt concentration 400 • Only occurs upon mixing with salt solution (for pH 10) 200 Gel time (min) time Gel
0 0.8 1 1.2 1.4 1.6 1.8 NaCl conc. (M) 2. Techniques for gelling polymer 1 on its own deemed unsuitable
13 Experimental Polymer 2
2. Gels using a chemical crosslinker o Polymer 2 makes very good gels: • Stronger, more flexible than controls o Can instil silica into polymer 2 gel • Double-network produced? • Does silica improve polymer 2 gel properties? o Gelation dependent on molecular weight - High: viscosity too high for permeation oOther applications: grouting • Encasing wastes which generate high temps - Lower: gelation very slow at soil temperature
14 Experimental Polymer 3
2. Forms self-crosslinks on drying or freeze-thaw cycling o Polymer 3 gives super-tough, flexible gels 0% 5% 10% 15% 20%
o Freeze-thaw • Strength depends on: Freeze-thaw - Polymer 3 concentration - # of freeze-thaw cycles • Can be frozen underground by injecting liquid nitrogen - Ground freezing already employed for hydraulic barriers
• Polymer 3 has strong interaction with silica – hard to mix Drying 15 Conclusion Summary o Experimental Work • Polymer 1 o Colloidal Silica - 2 gels produced depending on polymer conc. • Highly promising permeation grouting • Low conc.: mouldable, crack resistance material • High conc.: water retention, weakened structure • Considered for hydraulic barrier application in • Polymer 2 + crosslinker nuclear decommissioning - Strong, flexible gel • My Project: modify silica grout to - Can instil silica: double-network produced? improve/tailor properties - Likely unsuitable for permeation grouting • Polymer 3 o Polymer hydrogels - Gels on drying or freeze/thaw cycling • Excellent, customisable properties - Super-tough, flexible gel - Difficult to mix with silica • Combine them with silica in double-network gels?
16 Conclusion Next Steps o Short term o Long term • Analyse properties and structure of the gel • Modify colloidal silica particles via eg. coating variants produced using… with aluminium - Rheology - Further improve radionuclide sorption - Mechanical tests • Study colloidal silica, polymer hydrogel, and - Hydraulic conductivity tests hybrids as radiation shielding - SEM - Gels are 70-95% water - X-ray tomography - Rigid, can fit moulds • Confirm if double-networks have been - Easily vitrify silica to create a manageable produced, and the properties of such gels wasteform - No movement or leaking as with water • Communicate with industry partners to - Can embed radiation absorbers identify nuclear applications for these gels
17 References
[1,2] Zhao M, Liu G, Zhang C, Guo W and Luo Q 2020 Appl. Sci. 10 15 [3] Sögaard C, Funehang J and Abbas Z 2018 Nano Convergence 5 6 [4] Lin C-C and Metters A T 2006 Adv. Drug Deliv. Rev. 58 1379-1408 [5] Wang Q and Gao Z 2016 J. Mech. Phys. Solids 94 127-147 [6] Han L et al. 2017 NPG Asia Materials 9 e372 [7] https://www.youtube.com/watch?v=469C8l_wDeg&ab_channel=FluidDynamics [8] Bercea M, Morariu S and Rusu D 2013 Soft. Mater. 9 1244
18 Thank you for listening Electrokinetic Remediation and in-situ iron barrier generation
Dr. Jamie Purkis [email protected] University of Southampton
TRANSCEND Theme Meeting (virtual) Monday 17th May 2021 Electrokinetic Remediation, EKR electro kinetic
Electrical movement (of ions, …)
• Soil/groundwater/concrete
• Electromigration (A) movement of ions
• Electrophoresis (B) movement of particles
• Electro-osmosis (C) movement of water * *
*vs. standard hydrogen electrode (SHE) 2 Advantages of EKR
• In-situ (or ex-situ)
Anode Worker safety Cathode Injection well
• Cheap
(+ next day delivery)
Electrode material Additives • Adaptable Electrode placement Duration Electrolyte (In-)organic + radionuclide Voltage Combination (EKR-Bio…) 3 Ferric Iron Remediation and Stabilisation (FIRS)
Previously demonstrated at scale (1m +) in silica sand by NNL and will shortly appear in press: Purkis et al., manuscript under review (J. Haz. Mater.). Data are vs. SHE 4 Case Study – FIRS
In-situ barrier growth in real materials?
1. Sellafield Sand/Groundwater (GW) Anodes 2. Sellafield Clay/GW + + 3. Sellafield Sand/Seawater (SW) 16 cm 4. Sellafield Clay/SW
Steel electrodes, 0.5 V/cm 30 cm Monitor • Barrier over time • pH – – • Changes before/after Cathodes • (Sorptive properties)
pH sampling point Purkis et al., manuscript under review (J. Haz. Mater.) 5 Case Study – FIRS
1. Barrier over time 2. pH over time 3. Permeability 4. SEM 5. Mössbauer
Iron barrier thicker and forms faster in SW electrolyte
Different composition?
Sand with SW electrolyte Clay with GW electrolyte (GIF starts at day 0) Purkis et al., manuscript under review (J. Haz. Mater.) 6 Case Study – FIRS
1. Barrier over time 2. pH over time 3. Permeability 4. SEM 5. Mössbauer
Clay/GW (shown to day 20) Sand/SW (shown to day 21)
GW has lower ionic strength; weaker pH gradient forms (and forms slower) than SW
Purkis et al., manuscript under review (J. Haz. Mater.) 7 Case Study – FIRS
1. Barrier over time 2. pH over time 3. Permeability 4. SEM 5. Mössbauer
SAND in m/s Parent 1.1 x 10-3 GW 2.4 x 10-4 SW 1.6 x 10-4
CLAY in m/s Parent 1.3 x 10-10 GW 3.2 x 10-8 SW 4.6 x 10-7
Sand = ↓ permeability Clay = ↑ permeability Sand/SW Purkis et al., manuscript in preparation We acknowledge Prof. William Powrie and Mr. Jeerapat Sang-Iam (UoS) for data collection (BS EN ISO17892) Case Study – FIRS
1. Barrier over time 2. pH over time 3. Permeability 4. SEM 5. Mössbauer
2 cm
Clay/GW Clay/SW
Differences in iron phase formation SEM on thin sections of iron barrier material (+ microscopy) between GW/SW electrolyte High contrast (white areas; back-scattering) ∝ high [iron] Work ongoing Purkis et al., manuscript in preparation; thanks to Dr. Richard Pearce (UoS) Case Study – FIRS
1. Barrier over time 2. pH over time 3. Permeability 4. SEM 5. Mössbauer Mössbauer Spectroscopy (ongoing)
• Doublet 1 – likely Fe(III); oxide; Oh geometry Sextets 1 + 2 • Doublet 2 – likely Fe(II); oxide/hydroxide; doublet 2 likely Oh geometry
• Sextets – likely Fe(III); possibly (a-)Fe2O3 + ? haematite
Likely mix of iron oxides and oxyhydroxides, doublet 1 Clay/SW Fe(II) and Fe(III)
Work ongoing
Purkis et al., manuscript in preparation. We acknowledge Prof. Paul Bingham and Dr. Alex Scrimshire (Sheffield Hallam) for data collection and interpretation 10 Wider Context?
graphite
Purkis et al. J. Haz. Mater., 2021, 413, 125274 11 Conclusions, Further work, and Thanks
• EKR: in-situ, cheap, flexible
• Limited at scale
• Combined approaches FIRS: iron barriering (Si grouting – ongoing)
• Characterise iron barriers? ongoing (XRD, XRF…)
graphite
12 Sellafield Simulant GW:
MgSO4 = 250 mg
KHCO3 = 55 mg
CaCl2.2H2O = 472 mg
NaHCO3 = 470 mg
Ca(NO3)2 = 185 mg
SrCl2 = 167.5 mg 0.1 M HCl = 30 mL in 5 L of DI water J. Graham, MSSS GEMS Phase 2: Characterisation of Soils and Strontium Sorption Batch Testing, Report NNL 13224, National Nuclear Laboratory, NNL, 2015.
13 , Rebecca J Lunn Mountassir El
Gráinne Ronald J Turner, James M Minto, Emmanuel Salifu, Infrastructure Biotechnology for Treatment Treatment for Biotechnology Nuclear Concrete of Repair and
X THE UNIVERSITY OF STRATHCLYDE thaw and temperatures, thaw variable cycles, - Introduction exposure radiation to exposure broadly within whole built as a the environment within broadly freeze water, salt including degradation mechanisms, Many Significant volumes of concrete infrastructure can be found on UK Civil Nuclear sites, and also more more and sites, also UK Civil Nuclear found can on be of concrete infrastructure volumes Significant
X THE UNIVERSITY OF STRATHCLYDE Introduction Limits ingress of damaging chemical compounds chemical damaging of ingress Limits materials of reinforcing damage and resultant carbonation Minimises and present liquids air radioactive of any flux Decreases The reductionof permeability is key minimisingto thecorrosion of and isdesirable in other contextstoo therebar,
X THE UNIVERSITY OF STRATHCLYDE Existing repair methods for for methods repair Existing concrete at interface, delamination at interface, Epoxy resins coefficient expansion Thermal concrete, cracks to different Large grain size, won’t of parts small cracks (and small aperture won’t seal size, grain Large poor penetrability big cracks), Cement Cement mortars repairas
X THE UNIVERSITY OF STRATHCLYDE High pH environment (s) 3 O 2 CaCO + H + - 2 3 2+ + CO Ca - 2 + 2OH + + CO + + Sporosarcina pasteurii Sporosarcina 3 4 O 2 + 2H 2NH 2NH pH increase
mediated generation of calciumcarbonate generation mediated - 2 ) 2
O 2 + H CO(NH Bacterial ureolysis Bacterial using What is Calcite Calcite is What Biomineralisation? (calcite) from urea and calcium precursorscalciumand urea(calcite)from The enzymeThe
X THE UNIVERSITY OF STRATHCLYDE gain - reinforced concretes - structural. -
which are susceptibleto chloride attack/chloride ingress Bacterially generated the fracturecalcite may network be ableand to ‘plug up’ and couldeven contribute to some strength re so reduce permeability, This couldincrease the lifespanof concrete structures undergoing decommissioning, andparticularly is relevant to steel Concrete a mixture is of (un)hydrated calcium silicates,calcium hydroxide, and calcium carbonate (+ aggregate and iron rebar). Used in many nuclear infrastructure applications,both structural and non Bacterially generated Calcite for for Calcite generated Bacterially Repair Concrete
X THE UNIVERSITY OF STRATHCLYDE Concrete Samples Concrete foreshore, intertidal zone ~60 year~60 old concrete blockscollected from Hunterston
X THE UNIVERSITY OF STRATHCLYDE Concrete Samples Concrete Large blockscut down to produce 36x72mm concrete cores
X THE UNIVERSITY OF STRATHCLYDE CT analysis revealedCT a natural fracture - network in the concrete samples Visual Examination Visual and X Concrete Samples Concrete
X THE UNIVERSITY OF STRATHCLYDE is, - networks holder setupwas usedto treat the samples, through - cores selected for testing, 2 with natural fracture networks, Concrete Samples Concrete A core A injection of treatment solutions through the core 5 and3 with induced fracture effectively Initialtesting revealed that some corescould be treated as while others had too low a permeability be treatedto
X THE UNIVERSITY OF STRATHCLYDE Field implementation scale Testing scale - scale scale testing - Treatment of a wide range of range wide a of Treatment & orientations sizes crack Block •
scale induced scale -
methods materials filler Suitable Optimisation of fluids & delivery delivery & fluids of Optimisation • Bench in cores cracks • Next Step: Concrete Block Concrete Step: Next
X THE UNIVERSITY OF STRATHCLYDE observed were were of calcite as a method to repair repair calcite a methodas to of cores biomineralisation Treated cores were found to gain mass, based on dry weight dry weight on mass, based gain to cores were found Treated measurements fractures in in degraded fractures concrete through injection of treatment solutions concrete through permeability Significant reductions We have tested We Summary and Conclusions and Summary • • •
X THE UNIVERSITY OF STRATHCLYDE X THE UNIVERSITY OF STRATHCLYDE X THE PLACEUNIVERSITY OF USEFUL OF STRATHCLYDE LEARNING Reducing hazard in spent fuel removal at high temperature using colloidal silica gel
Arianna Gea Pagano, University of Strathclyde TRANSCEND Theme 2 meeting
14/05/2021 What is colloidal silica?
Formation of - - Aqueous siloxane bonds
suspension of (Si-O-Si) Gelling - silica particles
(SiO2) Name of Presenter, Organisation Meeting Title
Viscosity
Gel time
Time What is colloidal silica?
Formation of Aqueous siloxane bonds suspension of (Si-O-Si) Gelling silica particles
(SiO2) Name of Presenter, OrganisationWhat triggers gelling? Meeting Title • Electrolyte accelerator • Change in pH • Temperature
Viscosity
Gel time
Time Site decommissioning: removal of spent fuel and radioactive waste Fukushima: how the nuclear fuel rods will be removed | Hazard: Guardian Animations - YouTube • Release of airborne radioactive particulate during transport • Loss of radioactive debris in the rack during fuel retrieval • Waste corrosion may make the material not strong enough to be lifted up The Magnox Swarf Storage Silo: Making our most hazardous facility safer - YouTube • … OBJECTIVE: Reduce hazard in spent fuel removal at medium and high temperature by grouting the radioactive waste prior to retrieval Site decommissioning: range of operating temperatures
• Remediation of heavily contaminated soils Ambient temperature
• Removal of spent fuel rods from SFP
• Removal of radioactive 40 - 60°C waste from storage silos
Radioactive • Removal of radioactive debris debris following nuclear accidents > 100°C CS grouting around radioactive waste at high temperature
POSSIBLE VARIABLES: • Temperature of the radioactive waste (from ambient to > 100°C) • Grout volume • Grout properties (e.g. silica concentration) • Gelling conditions (dry, underwater) Experimental setup: schematic view
• Acrylic (PMMA) transparent container mm • Heater (steel casing + cartridge heater+ thermocouple) • PID temperature controller
Steel casing mm
Silica gel mm
Acrylic container mm Stainless steel casing PID Thermocouple temperature Cartridge controller heater Cartridge heater Thermocouple Experimental setup
• Acrylic (PMMA) transparent container • Heater (steel casing + cartridge heater+ thermocouple) Thermocouple • PID temperature controller Cartridge heater
Silica gel Acrylic container
Stainless steel PID casing temperature controller Experiment 1: grouting around an object at 60°C
• Grout mixing • Silica grouting around heater at 60 °C Colloidal 2M NaCl solution • Waiting for the silica to gel silica 1 part 5 parts • Leaving the heater at 60 °C for 8 hours
Gel time 8 h
20°C 60°C → 60°C 60°C
Heater Heater Heater Experiment 1: grouting around an object at 60°C
Setup transferred to XCT after 8 hours Experiment 1: grouting around an object at 60°C Sample extrusion Bottom – after heater removal Top – after extrusion
From visual inspection + XCT data: • No connected cracks • Small, isolated cracks due to decreased gas solubility with increasing temperature Grouting at higher temperature: 120°C 1. Effect of silica concentration
Concentrated silica (34% SiO2) Diluted silica (17% SiO2)
Colloidal + 2M NaCl Colloidal DI + 2M NaCl
solution silica 5 parts water solution 1 part silica 1 part 5 parts
Gel 12 8 h time mins 20°C 20°C 20°C 20°C → 120°C 120°C
Heater Heater Heater Heater Grouting at higher temperature: 120°C 1. Effect of silica concentration
• Silica concentration: 34% • Silica concentration: 17%
Top layer Bottom layer
Surface crack
‘Hard’ extruded gel
‘Soft’ extruded gel From visual inspection + XCT data: • Surface and radial cracks, resulting in • Reduced cracking, intact gel upon gel breakage upon extrusion extrusion Grouting at higher temperature: 120°C 2. Effect of sample height ‘Short’ sample (5 cm) ‘Tall’ sample (7 cm)
2 cm 4 cm
4 cm 3 cm 4 cm 3 cm
Gel 12 8 h time mins 20°C 20°C 20°C 20°C → 120°C 120°C
Heater Heater Heater Heater Grouting at higher temperature: 120°C 2. Effect of sample height
• Sample height: 5 cm • Sample height: 7 cm
Top layer Bottom layer
Lateral crack
From visual inspection + XCT data: • Surface and radial cracks, resulting in • Reduced cracking, intact gel upon gel breakage upon extrusion extrusion Grouting at higher temperature: 120°C 3. Effect of heating condition at gelling Gelling at 20°C Gel 12 8 h time mins 20°C 20°C 20°C 20°C → 120°C 120°C
Heater Heater Heater Heater
Gelling at 120°C Gel 8 h time 20°C 120°C ↑120°C 120°C
Heater Heater Heater Grouting at higher temperature: 120°C 3. Effect of heating condition at gelling
• Gelling at 20°C • Gelling at 120°C
Surface crack Lateral crack
From visual inspection + XCT data: • Reduced radial cracking when gelling at 120 degrees • ‘Looser’ silica gel above the heater when gelling at 120 degrees Grouting at higher temperature: 120°C 4. Grouting in a porous medium
Colloidal Colloidal silica+ silica glass beads
Gel 12 8 h time mins 20°C 20°C 20°C 20°C → 120°C 120°C
Heater Heater Heater Heater Grouting at higher temperature: 120°C 4. Grouting in a porous medium
• Silica gel • Grouted glass beads
From visual inspection + XCT data: • Grouted glass beads sample is fully intact (no surface or radial cracking) Grouting at higher temperature: 120°C 5. Dry gelling and gelling underwater
Dry gelling Gel 8 h time 20°C 120°C ↑120°C 120°C
Heater Heater Heater
Gelling underwater 8 h 65°C 65°C 20°C ↑120°C 120°C 85°C 85°C Heater Heater Heater Heater Grouting at higher temperature: 120°C 5. Dry gelling and gelling underwater Grouting at higher temperature: 120°C 5. Dry gelling and gelling underwater
• Dry gelling • Gelling underwater
From visual inspection + XCT data: • Reduced surface/radial cracking (intact gel upon extrusion) when gelling underwater Conclusions
• Colloidal silica grouting is suitable for grouting around medium-temperature (40-60°C) waste
• At higher temperature (>100 °C): o Lowering the silica concentration has a beneficial effect on crack formation o The formation of surface cracks may be inhibited or reduced by increasing the volume of grout above the waste o Grouting porous media improves the performance of the grout against crack formation o Gelling underwater reduces radial and surface cracking Thank you
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