spent fuel and waste science and technology salt disposal ... · – volatiles in salt (e.g.,...

Spent Fuel and Waste Science and Technology

Salt Disposal R&D:Field Test + Big Picture

Kris KuhlmanSandia National Laboratories

SFWST Annual Working Group MeetingLas Vegas, Nevada

May 22-24, 2018

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. SAND2018-5424 PE


Salt R&DMay 23, 2018

1) Salt R&D Programmatic Overview2) Salt Heater Test Overview

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Overall Goals of Salt R&D

Salt’s Benefits as a medium for disposal:– Impermeable to flow in far field (≤ 10−20 m2)– High thermal conductivity (~5 W

m⋅K)

– Relatively dry – Biologically simple– Creep closure and healing of excavations/fractures– Easily mined via continuous miner

Where to Contribute to Salt Technical Basis?– Disposal of heat-generating waste vs. WIPP– Bedded vs. domal salt

Contribution to Long-Term PA– m-scale behavior over days/weeks is PA initial condition– Brine availability impacts corrosion & transport

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Recent Salt Field Test History

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DOE-EM planned Disposal Demonstrations planned at WIPP– DOE-Environmental Management (DOE-EM) Carlsbad Field Office runs WIPP

– Salt Disposal Investigations (SDI) – 2011 (hot alcove-style disposal demo)

– Salt Defense Disposal Investigations (SDDI) – 2013 (cooler in-drift disposal demo)

DOE-NE Salt R&D Albuquerque Workshop (March 27, 2013)

– SNL, LANL, LBNL, DOE: salt field experiments consistent w/ UFD roadmap

DOE-EM work on SDI/SDDI stopped (Feb 7, 2014)

DOE-NE Small-scale (phased) testing approach at WIPP

– 2014 DOE-NE ramps down generic modeling and laboratory work on salt

– 2014-2016: morphed from drift-scale demonstration to borehole-scale test

– Small-scale borehole heater test designed in FY17 (SNL/LANL/LBNL)

– Small-scale borehole heater test implementation beginning June 2018



Salt R&D in Safety Case

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SDI/SDDICurrent PlannedField Tests



Salt R&D Gaps: 2012 UFD Roadmap

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2012 UFD Roadmap Document– Five of top 6 high-priority FEPs (Appendix B) are on Salt [score]

1. 2.2.01.01 – Evolution of Clay/Shale EDZ [8.00]

2. 2.2.08.01 – Flow through salt host rock [7.73]

3. 2.2.08.02 – Flow through other geologic units near salt repository [7.73]

4. 2.2.08.06 – Flow through the salt EDZ [7.73]

5. 2.2.08.04 – Effect of repository excavation on flow in salt host rock [7.10]

6. 2.2.08.07 – Mineralogic dehydration of salt [6.49]

These FEPs rated “High: information essential to decisions” – Site Selection

– Site Characterization

– Site Suitability



Salt State of the Art: 2012 UFD Roadmap

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2012 UFD Roadmap Document: “State of the Art” for key FEPs– Need to understand fracturing and healing in clays and salt.

– Water migration in salt is a unique process that needs to be better understood. Need to understand thermal and pressure gradients and gas generation and migration.

– Need to know the evolution of the characteristics of the EDZ under the thermal-mechanical and wetting changes (clay and salt).

– Need to understand the coupled evolution of near-field host rock (EDZ) and backfill.

– Considerable work has been done for WIPP and European programs.

– European programs starting multi-year projects investigating thermal-mechanical and moisture effects in the EDZ.

– This issue includes other disturbances (e.g., ventilation) beyond just excavation effects.

2012 UFD Roadmap “take-away message” regarding Salt– Brine migration (+ventilation dry-out) needs to be better understood

– THMC Evolution of EDZ is complex, but important

– Significant existing international field testing database exists



Salt R&D Priorities

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Salt R&D is focused on field test– Shakedown heater test in existing boreholes (now)

– Heater test in new built-for-purpose boreholes (later this FY)

– Larger scale follow-on demonstrations

Salt R&D Modeling/Lab Efforts Support field test– Numerical modeling to design and interpret results of field test

• LANL (FEHM) & LBL (TOUGH-FLAC)

– Laboratory testing to analyze brine/gas/solid samples collected during field test

• SNL (solids and liquids) & LANL (liquids and gases)



Salt R&D Priorities

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Salt R&D Lab Efforts for Liquid Samples (SNL)– Analysis of brines not trivial, requires significant dilution and

there is interference between ions

– Using Ion Chromatograph (IC) & Inductively Coupled Plasma Optical Emission Spectrography (ICP-OES)

Salt R&D Lab Efforts for Solid Samples (SNL)– Pore space and mineralogy characterized via Zeiss X-ray microscope



Integration with GDSA/PA & Safety Case

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Developments for GDSA are lower priority in Salt R&D (FY18)– Numerical modeling to design/interpret tests takes priority

GDSA and PA potential contribution areas for Salt– Pitzer model needed to do “full chemistry” in salt (using EQ3/6 now)

– Other chemistry → fluid flow coupling effects with brine

• FEHM implements some of these now (e.g., vapor-pressure lowering)

• Implementing analogous features in PFLOTRAN is possible

– EDZ development and evolution is especially important in salt

• TOUGH-FLAC implements these now

• Moving features from TOUGH-FLAC to PFLOTRAN is difficult / requires “response surface” for PA



Integration with International

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Upcoming US/German Salt Repository Workshop– September 2018 in Hannover, Germany

– Same week/location as SaltMechIX conference

– NEA Salt Club meeting Friday before in Braunschweig, Germany

– WEIMOS geomechanical benchmarking meeting (SNL/BGR/IfG)

Field Test Design shared at 2017 US/German workshop

Increased exposure of test with foreign partners– Experimental data useful to German/Dutch/British repository programs

– More involvement with foreign partners in future design/interpretation

– Future WEIMOS-like US/German collaboration on seals (Matteo)



Salt Disposal R&D Five-Year Plan

Small-Diameter Borehole Heater Test (SDBHT)– FY17-18 test plan / late FY18 begin execution– Isothermal test & 120 °C test in existing holes– Re-design for follow-on heated tests

Other Possible Tests in “Out Years”– Further SDBHT configurations – Intermediate-scale testing

1. Large-scale granular salt reconsolidation2. Shear testing3. Single-canister thermal test

Laboratory/Modeling Investigations– Only those supporting field investigations

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(1)

(2)(3)

(SDBHT)

Salt Host Rock Integration Pyramid

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Waste Form (WF)

EBS Buffer/Backfill Host Rock

Was

te P

acka

ge(W

P)

ENGINEERED BARRIER SYSTEM (EBS) GEOSPHERE

THCMBR Processes

Radionuclide (RN) Transport

BIOSPHERE

Biosphere (and Surface)

[SNF][HLW]

[BENTONITE] [GRANITE]

NEAR FIELDSOURCE FAR FIELD RECEPTOR

Seal

s/Li

ner

Aquifer

Source Term RN Inventory WF Degradation WP Degradation

Receptor Dilution Water

Consumption Dose Conversion

Factors

Near-Field and Far-Field Buffer Degradation DRZ Evolution Chemical Interactions Thermal Effects

Advection Diffusion Sorption RN Decay and

Ingrowth

Dist

urbe

d Ro

ck

Zone

(DRZ

)

Processes

Lab & Field Experiments

Subsystems

ModelsTHC Moisture Redistribution

in Backfill (heat pipe)THM Drift Creep Closure / DRZ

Healing

Waste Form/ PackageDegradation

In Situ Brine

AvailabilityLab Salt Heat Pipe / Dry Out

Lab Acid Gas Generation

In Situ Shear Test

In Situ SaltReconsolidation

Heated Borehole Closure

“Single Canister” In Situ Heater Test

[Run of Mine Salt]

[Salt]

THMC → GDSA Initial Conditions (saturation) and EDZ distribution

Radionuclide Transport

Full Chemistry Reactive Transport (including Pitzer)

Backfill Reconsolidation

THMC BackfillReconsolidation

Drift-ScaleHeater Test

SDBHT (Phase 1)In Situ Testing Options

(Phase 2)

Drift-Scale(Phase 3)


Salt R&DMay 23, 2018 14

1) Salt R&D Programmatic Overview2) Salt Heater Test Overview



SDBHT Executive Summary

Goals of Small-Diameter Borehole Heater Test (SDBHT)– Brine availability, brine transport, brine composition, and gas evolution– Collect datasets for:

• Validating numerical models• Populating constitutive models

– Get back underground, gain hands-on experience Straightforward Modular Design

– Central test borehole (4”-6” diameter, ≤6 m long, ≤2 m test interval)– Satellite observation boreholes (1”-2” diameter)– Packer-isolated test interval– Test repeated at target temperatures (30, 50, 120, 160 & 200 °C)

Horizontal Test Orientation– Avoids mapped clay, polyhalite, or anhydrite layers– Interval completed in single geologic unit (MU-0 at WIPP)

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SDBHT Phased Approach (1) Packer inflation tested in Existing Borehole (Feb 2018) Heated “Shakedown” tests in Existing Boreholes (June 2018) Packer, Heater, Gas Circulation System & Borehole Closure

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SDBHT Phased Approach (2) New Boreholes to be drilled in 2018

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~Test target elevation

Existing Borehole location



Horizontal Bedded Salt Heater Test

Previous WIPP heater tests crossed significant clay layers Clay layers dominated response (especially ≥100 °C) Without clay/anhydrite, salt DRZ is main source of permeability

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Testing Outside Access Drift DRZ

Test interval should be outside access drift DRZ Test borehole DRZ should be main source of perm / porosity

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Damagemodeling

Damageobservations



Brine Composition Expectations

Brine collects in borehole H2O removed with dry N2 Brine composition evolves

– Initially precipitates halite– Becomes Mg & K rich

3 primary brine sources– Intergranular (pores)– Intragranular (inclusions)– Hydrous Minerals

Different brine sources have variable composition– Competing effects on observed

brine composition– EQ3/6 modeling to interpret

observations– Experiments to validate

approach

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K+/Mg++

Na+

/Cl-

Intergranular brine



Gas Composition Expectations

Gases from thermal decomposition of:– Volatiles in salt (e.g., hydrocarbons at Asse)– Gases trapped in fluid inclusions– Dissolved gas in brine– Rubber (silicone, neoprene & viton) components in seals and packers

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Water from brine– Natural H2O– D2O tracer

Acid gas from salt/brine– Decomposition of solid hydrous

Mg salts into MgO + HCl– Equilibration of PHCl(g) into

condensed steam from strong brines (especially Mg-Cl brines)

– Very low pH observed (≤1)– Acid may cause further

component decomposition

Site 1 (~195°C)

Coyle et al. (1987) BMI/ONWI-624



Brine Inflow Expectations

Brine inflow rate– Highest immediately after drilling– Exponential decay

Higher brine inflow at higher T– Especially from clay above 100°C

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Isothermal brine inflow at WIPP in MU-0

Vertical WIPP boreholes (Clay F)

50°C

130°C



SDBHT Test Design

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Tests In New Boreholes• Monitor Water Inflow• Sample Gases• Sample Liquid Brine• Geophysics:

• ERT• Acoustic Emissions• Temperature



SDBHT Project Plan

Project Plan Document developed in April 2018 Responsibilities of Participants in Project

– SNL: Project Management, Brine Sampling, Brine & Solids analysis, Borehole Closure, Acoustic Emissions, EBS

– LANL-Carlsbad: WIPP Underground Test Coordination Office– LANL: Heater Design/Control, Gas Handling, Packers, THC

modeling (FEHM), Brine & Gas analyses– LBL: Electrical Resistivity Tomography, Fiber-optics based

Observations, THM modeling (TOUGH-FLAC)– WIPP M&O Contractor (Nuclear Waste Partnership): Coring,

Site ES&H, Site access & power

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Salt R&D Session Summary

Remainder Salt R&D Session

~10 minute lightning talks– Doug Weaver (LANL): WIPP Support and Logistics– Phil Stauffer (LANL): Update on Salt Disposal R&D– Jonny Rutqvist (LBL): Update on Salt Disposal R&D– Melissa Mills (SNL): Laboratory Brine Evap. Studies– Peter Johnson (LANL): Coupled THC Processes in Salt– Yuxin Wu (LBL): Geophysics in Heater Test– Ed Matteo (SNL): International / EBS / Sealing

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Salt R&D Team (SNL/LANL/LBL) – Working towards a single common goal for several years– Implementing borehole heater field test at WIPP this summer

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spent fuel and waste science and technology salt disposal ... · – volatiles in salt (e.g.,...

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