19 herold 20160830 elsa final

P. Herold – 08/2016US/D WorkshopWashington, USA, Sept. 7-9, 2016

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Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a

wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear

Security Administration under contract DE-AC04-94AL85000. SAND2016-XXXX.

Shaft seals for HLW repositories (ELSA project)

Philipp Herold1, Michael Jobmann1, Wolfram Kudla2, Matthias Gruner2

1DBE TECHNOLOGY GmbH2TU Bergakademie Freiberg

Washington, DCSeptember 7-9, 2016


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(1) Review of presentation from last Workshop- Latest developments related to in-situ compaction of backfill columns of crushed

salt–clay–mixtures- Alternative option: Binary mixture

(2) Shaft sealing concepts

(3) Shaft sealing elements made of asphalt and bitumen- ELSA experiments and parallel developments- Microstructure analysis of bitumen-salt interface

(4) In-situ experiment with MgO-concrete

(5) Small-scale test on bentonite-based sandwich systems

Contents


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Compaction of crushed salt–clay–mixtures

Vibrating pre-compaction satisfied our expectations All mixtures performed well Handling of the mixture with a maximum grain size of 4 mm ("mOBSM") has

almost no segregation effects Due to impulse compaction, the mixture "OBSM" (max. grain size 10 mm,

water content 3.4 m%) reached total porosities around 9.6 % (mOBSM ~11.9 %, with water content of 4.4 m%)

Calc. air voids are in a range between 1.8 and 3.5 % Due to surface bulking, final compaction affected only at the bottom Successfully transfer from laboratory scale into full scale

Results from 6th US/German Workshop in Dresden:


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Next steps:

• Development and test of a "shaft-impact-compactor“• Based on existing dynamic compaction equipment and optimized for

underground conditions: Falling weight: 1000 … 5000 kg Falling height: 0.3 … 2.0 m Compaction foot with diameter 0.8 m (pre test) and 2.0 m (shaft) "Weight-saving" and smaller construction for higher flexibility in shaft

working


Repeat in-situ test with the new compactor and with only one reference mixture


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Alternative option: Binary mixture

Layer of Rock Salt Compacts

Binary Mixture after Oedometer Test at 5 MPa

Component 1: Rock salt roller press compactsComponent 2: Crushed salt–clay–mixture (< 4 mm)

+ Well-known technology (bentonite binary mixture for shaft sealing)+ Low water content (no added water)- Additional roller compaction process- High permeability: 3∙10-14 m² (due to low density of component 2)



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ELSA project includes development of shaft sealing elements and corresponding shaft sealing concepts for salt and clay formations

Shaft sealing concepts

Sealing concept for Jurassic clay formations as expected in southern Germany:

Sealing concept for bedded rock salt as known in northern Germany:

different sealing elements made of asphalt/bitumen


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Bitumen and asphaltSystem Bitumen

SandwichBitumen filled gravel column

Asphalt with rounded gravel

Function Sealing Sealing and Abutment Sealing and Abutment

Design

Materials Bitumen with different viscosity

Crushed Basalt 32 / 63 mmBitumen, standard or with filler

Rounded Basalt 20 / 40 mmBitumen, standard or with filler

Related to

Konrad project ERAM project ELSA project

Status •Conceptual design

• In-situ test planned within ELSA-Project

•Pilot tests at TU Bergakademie Freiberg (presentation at 5th Workshop in Santa Fe)

•Full-scale field test (BISETO Project, supported by BfS)

• In-situ test within ELSA Project

•design and development• In-situ test within ELSA Project


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In-situ test during ELSA project:• Borehole D = 0.5 m, H = 1.0 m• Crushed Basalt 32 / 63 mm (1.708 g/cm³)• Filled with straight-run Bitumen (at 170 °C)

Initial permeability of the rock salt: 2∙10-22 m² (gas)Effective permeability of the system: 4∙10-20 m² (gas)

Bitumen and asphalt

Crushed Basalt Gravel – filled with Bitumen

Abutment, MgO-Concrete

control chamber

bitumen filled, crushed basalt gravel

test chamber


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• Same dimensions as Type 1 test (Borehole D = 0.5 m, L =1.0 m)

• Mixture of rounded Basalt (20/40 mm) with straight-run Bitumen at 140 °C

Bitumen and asphalt

Asphalt with special aggregates

Laboratory and in-situ tests during ELSA project:

• First lab tests to identify compaction properties of the rounded gravel and suitable bitumen/gravel mixture


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"Soft Core”, made of Bitumen/Bitumen with filler, Asphalt or Basalt, filled with Bitumen

"Hard Shell“, made of Oxidised Bitumen or Asphalt with oxidised Bitumen

In-situ test during ELSA project:• Two in-situ tests in rock salt (boreholes D = 0.3 m)• Initial permeability of the rock salt:

6∙10-22 m² (gas) and 5∙10-22 m² (gas) • Effective permeability of the system:

2∙10-20 m² (gas) and 6∙10-20 m² (gas)1∙10-20 m² (NaCl solution)

Bitumen and asphalt

Concept "Soft Core + Hard Shell"

Coating of entire sealing location


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Bitumen Priming Coat - Improvement of Wettability to Rock Salt

• Bitumen Priming Coat - Improvement of wettability to rock salt• Licensed by mining authority• Patent DE 102008050211

With coating: Good WettabilityNo Coating: Bad Wettability

Bitumen and asphalt


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Over-drilled sample (D = 0.5 m)

Hard Shell (oxidised Bitumen)

Soft Core (straight-run Bitumen)

Bitumen and asphalt

Concept "Soft Core + Hard Shell“

Removal of the bitumen seal


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Concept "Soft Core + Hard Shell"Sealing Performance of Bitumen in the Contact Zone and in the EDZ

Bitumen penetrates cracks

(max. 0.5 cm)

Bitumen and asphalt


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Concept "Soft Core + Hard Shell"Sealing Performance of Bitumen in the Contact Zone and in the EDZ

ca. 4 mm

ca. 100 µm

Con

tour

• Steady pressure (1.1 MPa) over long time (several weeks) allows inflow

• All micro-cracks next to contour filled

• Air filled endings• Corresponds to expected

rheological behavior (viscosity at 20°C 1E7 Pa*s, see also Working package 5 – Numerical Calculations)

Bitumen and asphalt


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Label C3 with long-term stable phase (3-1-8)

• In-situ test in rock salt (D = 1 m, L = 2 m)• Start: June 2014• Finish: January 2016• Removal and sampling during the last months• Ongoing analysis• Composition:

MgO (active) 6.75 %MgCl2-Solution 15.83 %Aggregate 77.42 %(incl. Quartz Flour)

MgO-Concrete

+ Thermodynamically stable phase up to 80 °C and if concentration of Mg2+ in salt solution > 0.5 mol / kg H2O

+ Low dTMax (at adiabatic conditions: 54.7 K, during in-situ test 40 K)+ Contact pressure at the rock salt contour > 2 MPa (measurement limit) at 2.5 mm/m

expansion

- Stress Relaxation


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DS ES DS ES DS

Host rock

Multi-layer sealing system of bentonite (DS) and equipotential layers (ES) Homogeneous wetting and swelling Functionality independent of host rock

Fluid inflow

Patent DE No. 10149972

Sandwich system for bentonite seal


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Semi-technical scale experiments

HTV-1 and HTV-4: shaft sealing HTV-2 and HTV-3: drift sealing

Fluid inflow


Gravel

Gravel


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• Next Step: Scheduling separate project for the in-situ test of a sandwich sealing system at the Mont Terri Test Site in Switzerland

• Target time: start in 2017 … 2018• Proposer/Coordination: KIT-CMM, BGR, GRS

• Further partners:Swisstopo, ENSI, Nagra (Switzerland)TU Bergakademie FreibergIBeWa, FreibergThomas Schmidt KG, Dornburg-Langendernbach



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Summary

• Development of "shaft-impact-compactor“ after successful large-scale test of compaction of crushed salt-clay-mixtures initiated

• Development of alternative Binary Mixture based on pellets and powder

• In-situ test for all types of bitumen/asphalt seals realized • Measured system permeability is close to initial host rock permeability• Bitumen penetrates EDZ and fills cracks

• First in-situ test of new MgO-concrete label C3

• Semi-technical scale experiments of bimodal bentonite sealing for a planned separate in-situ test at Mont Terri Site


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Acknowledgements

Many thanks…

…to all colleagues and participating organizations:

…to the Federal Ministry for Economic Affairs and Energy (BMWi) and the Project Management Agency Karlsruhe (PTKA) of the Karlsruhe Institute of Technology (KIT) for funding the R&D project


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Thank youfor your attention.