91 92. june 9 overview febex-dp-and_ufd r&d activities related to febex-dp_zheng
TRANSCRIPT
Used Fuel Disposition Campaign
FEBEX-DP Collaboration
Liange Zheng, Hao Xu, Jonny Rutqvist, Jens Birkholzer Lawrence Berkeley National Laboratory June 9, 2016
Used Fuel Disposition
Part 1: Overview of FEBEX-DP
FEBEX: Full-scale Engineering Barriers EXperiment Experiment were based on Spanish HLW
emplacement concept for a granitic host rock It was initiated by ENRESA in 1994 under the
auspices of EU It is composed of laboratory experiments, Mock-up
and in situ tests, and THC/THM modeling.
Mock-up test February 1997– now
Galleries
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FEBEX Jan 1996 – Jun 1999
FEBEX II Aug 2000 – Dec 2004
NF-PRO (WP3.3) Jan 2005 – Dec 2007
FEBEX-e
Planning and design Set-up 1st Operational Phase 2nd Operational Phase Excavation
94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
FEBEX-DP
16
Partial dismantling Final dismantling
FEBEX in situ Test
Zürich
Grimsel
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FEBEX: in situ Test Partial Dismantling of heater 1 (2002)
Dismantled section
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FEBEX–DP: Dismantling of heater 2
Objectives Bentonite characterization
– Density, water content and spatial distribution – Chemical changes
Characterization of corrosion and microbial processes
– On instruments/sensors and coupons – Bacterial growth – All under evolving redox-conditions
Mineralogical interactions at material interfaces
– Concrete - bentonite, heater/liner – bentonite, rock - bentonite
– Impact on pore water composition
Integration of the monitoring results and modelling
– THM/THMC modelling – Pre- and post dismantling
5
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S49
FEBEX–DP: Dismantling of heater 2
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Hot sections
Cold sections
Hot sections
Cold sections
FEBEX–DP: Dismantling of heater 2
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Part 2: UFD R&D Activities Related to FEBEX-DP
Coupled THMC modeling The hydration of bentonite:
Non-Darcy flow – the presence of a threshold gradient Decrease of intrinsic permeability of the buffer due to swelling Action of thermal osmosis to counteract flow towards the heater
The chemical evolution in the bentonite Changes of more soluble minerals (gypsum, calcite and pyrite) and aqueous concentration, evolution of pH and Eh, alteration of smectite
Experimental work Synchrotron X-ray Microtomography Measurements to characterize the micro-
cracks of the bentonite(LBNL). Characterization of the microstructure of Bentonite and interface areas using
SEM – EDS – BSEI and X-ray CT Scan (SNL) Hydrothermal Experiments (LANL)
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THMC Modeling: Key Model Features
1D Model For hot sections Chemical reactions includes aqueous complexes, cation exchange, mineral dissolution-precipitation Two mechanical models were tested
Linear Swelling: dSlKd sws βσ 3=
Porosity change:
Permeability change: ( )Kekk
0
0
σσ −
=
BExM
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0.4 0.6 0.8 1 1.2
Wat
er co
nten
t (%
)
Radial distance (m)
Data 5.2 yrs Data 18.3 yrs
THMC-LS, 5.2 yrs THMC-LS, 18.3 yrs
THMC-BExM 5.2 years THMC-BExM 18.3 yrs
Model Results: T, RH and WC
Observations: As expected, THMC model outperform TH model in matching the RH data near the heater. THMC model reasonably match the water content and porosity data at 5.2 years (dismantling of heater 1) and at 18.3 years (dismantling of heater 2). The cooling period after heaters were switched off leads to significant redistribution of moisture.
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0 1000 2000 3000 4000 5000 6000 7000
Rela
tive
hum
idity
(%)
Time (day)
R = 0.52 mWCSE2-03WCSE2-04WCSE1-03WCSE1-04THMC-LSTH modelTHMC-BExM
Temperature
Relative humidity
Water content
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Model Results: Stress
E2 F2
Observations: Reasonable match between model results and stress data.
-1
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Nor
mal
Str
ess (
MPa
)
Time (day)
E2 data, r=1.1 mF2 data, r=1.1mTHMC-LS Radial THMC-LS circumferential THMC-BExM radialTHMC-BExM circumferential -1
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Nor
mal
Str
ess (
MPa
)
Time (day)
E2 data, r=0.5 mTHMC-LS circumferential THMC-LS Radial THMC-BExM circumferentialTHMC-BExM radial
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Model Results: Cl-
Observations: Porosity increase and permeability reduction in THMC model does not significantly improve the fit to measured Cl data; However, after 18 years, the model results for the THC and THMC model are similar. Increase in permeability near the granite improves the fit to Cl data
0.E+00
5.E-02
1.E-01
2.E-01
2.E-01
3.E-01
3.E-01
4.E-01
0.4 0.6 0.8 1 1.2 1.4
Conc
entr
atio
n (m
ol/L
)
Radial distance (m)
Cl- data S29, 1930 days
data S19, 1930 days
data S28, 1930 days
THC model, 5.2 yrs
THC model, 18.3 yrs
THMC-LS 5.2 yrs
THMC-LS, 18.3 yrs
THMC-BExM, 5.2 yrs
0.E+00
5.E-02
1.E-01
2.E-01
2.E-01
3.E-01
3.E-01
4.E-01
4.E-01
0.4 0.6 0.8 1 1.2 1.4
Conc
entr
atio
n (m
ol/L
)
Radial distance (m)
Cl-
data S29, 1930 days
data S19, 1930 days
data S28, 1930 days
THMC-LS base
THMC-LS sensitivity
( )0
0φφA
ekk =A Sensitivity case
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Checking the Microscopic Structure
Synchrotron X-ray Microtomography Measurements - Characterization of the microstructure of the material. - Description of the crack network in a quantitative fashion. - Study the mechanisms involved in the propagation of cracks. - Provide data for models.
Scanned with the 3.22 μm resolution setup
S59
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Sample as is (cropped), FOV ~6mm, 3.22 μm vx size Virtual cut to show the inside of the sample Cut sample with the medial axis of the crack network labeled with the aperture value All the (aperture color labeled) medial axes of the cracks in the sample Connected component labeling of the fractures larger than 1000 vx in volume
Checking the Microscopic Structure
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B-D
-59-
15
B-D
-59-
8
B-D
-59-
3
Sample rendering Aperture-labeled medial axes Overlapped data
1 mm
Checking the Microscopic Structure
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Bentonite – Concrete Interface Characterization (SEM – EDS – BSEI) (SNL)
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Back-Scattered Electron Image (BSEI) of Bentonite – Cement Interface
X-ray Map Line Scan: Ca
Portlandite Grain? Approx. Interface Location
So far – no indication of strong elemental gradients beyond the interface region
Cracks (desiccation?) tend to be abundant at the interface
Portlandite mineralization at the interface?
More elemental line-scans needed to resolve compositional gradients
Work in Progress!!!
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Ongoing and Future Work
Coupled THMC modeling Considering thermal osmosis and dual continuum for transport to improve the fit to conservative species. Refining chemical models to match reactive species
Synchrotron X-ray Microtomography Measurements
Taking more measurements for samples for section 59 and 49
Developing a tool to characterize the fracture network in a quantitative fashion
Used Fuel Disposition Sample from B-D-59-8
Thin horizontal slice from the whole measured volume, highlighting the microstructure and the fracture network (in yellow, on the right).
1 mm
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Thin horizontal slice from the whole measured volume, highlighting the microstructure and the fracture network (in yellow, on the right).
An aggregate particle in this sample displays negative crystals (dissolution?)
1 mm
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Displaying a thin slice of the sample reveals some more details about the method: B-D-59-3 B-D-59-8 B-D-59-15
To quantify the fracture network characteristics of the different samples we use a simple procedure (optimization of the process is ongoing): - Segment the voids from the dataset - Calculate the medial axis of the resulting binary dataset - Calculate the local thickness of the binary dataset - Label the medial axes with the local thickness value in the same position A statistical analysis of the aperture values becomes now possible and can be used to characterize and compare different sample in a quantitative fashion.
.5 mm
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Example of the results from a 3.22mm x 3.22mm x 1.61mm volume for each sample (3.22 μm voxel size, theoretical resolution)
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150000
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5 15 25 35 450
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5 15 25 35 45
BD 59-3
BD 59-8
BD 59-15
Bin [μm] Bin [μm]
Aperture analysis of the medial axes: Absolute values %
Larger amount of small voids due to a very (micro-) porous aggregate particle in BD 59-15
BD 59-3 has larger fractures
The negative crystals of BD 59-15 contribute to the larger aperture values amount
Used Fuel Disposition Some comments/conclusions
- Synchrotron X-ray microCT can be used effectively to characterize the microstructure of the sample, with special focus on fracture networks.
- Measurements at different resolutions found that a 3.22 μm vx size and ~6 mm field of view is the best compromise, in the context of the resolution vs. FOV problem.
- Still, given the high heterogeneity of the samples, the volumes investigated are hardly representative of the whole material. Plus sampling issues can be present as well.
- Encouraging results have been obtained in the perspective of developing an experimental strategy to monitor the development of cracks during the sample drying, to obtain further information about the fracturing mechanisms present.
- Quantitative characterization of the voids/fractures in the sample can be successfully carried out to compare different volumes and/or samples.