This document summarizes a collaboration between Lawrence Berkeley National Laboratory and Clausthal University on coupled thermo-hydro-mechanical (THM) modeling of salt. It discusses the TOUGH-FLAC and FLAC-TOUGH simulators, benchmarking results, improvements made to both codes, and an example collaboration project modeling heater tests at the Asse mine. The collaboration has improved salt THM modeling through code comparisons and jointly developing new constitutive models.

1. Spent Fuel and Waste Science and Technology
Collaboration with Clausthal/Germany on
coupled THM modeling
Jonny Rutqvist, Mengsu Hu, Laura Blanco-Martin, Jens Birkholzer
Lawrence Berkeley National Laboratory
SFWST WG Meeting in Las Vegas
International Session
May 24, 2017

2. Spent Fuel and
Waste Science and
Technology
Salt Coupled THM Processes – TOUGH-FLAC
 Lux/Wolters solid salt constitutive model (creep, TM damage-induced permeability
(DZ), high pressure fluid filtration, sealing, heating)
 Crushed salt constitutive model (THM properties as a function of compaction and
solidification)
 Large-strain and deformable mesh
 Brine migration, evaporation, condensation, salt precipitation etc. (THMC)

3. Spent Fuel and
Waste Science and
Technology
Based on same software
Use of different numerical schemes
TOUGH-FLAC
(Berkeley Lab)
Sequentially coupled flow-geomechanics simulators
TOUGH2 (fluid + thermal flow)
FLAC3D (geomechanics)
Can deal with large strains & creep processes
Material-specific constitutive relationships available
FLAC-TOUGH
(TU Clausthal)
Similarities
Main difference
Fixed-stress split
Undrained split
TOUGH-FLAC vs FLAC-TOUGH

4. Spent Fuel and
Waste Science and
Technology
• LBNL expertise on multiphase flow and geomechanics with TOUGH-
FLAC complemented with Clausthal expertise on salt geomechanics
and constitutive models
• New improvements implemented in both TOUGH-FLAC and FLAC-
TOUGH and benchmarked against each other
• Collaboration results presented in journal (2) and conference (5)
presentations during 2014-2016..
• International code comparison project (BenVaSim) lead by Clausthal
University focusing on “simulator benchmarking” for full THM,
including fluid flow
LBNL-Clausthal Collaboration

5. Spent Fuel and
Waste Science and
Technology
Example of LBNL-Clausthal Collaboration:
TSDE (Heater Test) Asse Mine
Code-to-code verification and validation against experimental data

6. Spent Fuel and
Waste Science and
Technology Concluding Remarks
• Mutually very beneficial collaboration resulted in great
progress in salt coupled THM modeling within a few years
• Further model improvements and benchmarking is planned
focusing on full THM coupling, including fluid migration
(BenVaSim)