Yucca Mountain Drift Scale Test

Task 2 The Drift Scale Test (DST) in the Exploratory Studies Facility (ESF) at Yucca Mountain, USA... 

MEASURING THERMAL, HYDROLOGICAL, MECHANICAL, AND CHEMICAL RESPONSES IN THE YUCCA MOUNTAIN DRIFT SCALE TEST... 

CRWMS M O, 1997. Drift Scale Test Design and Forecast Results. Report BABOOOOOO-01717-4600-(KX)07, Rev.Ol, prepared by the Civilian Radioactive Waste Management System Management and Operating Contractor for the U.S. Department of Energy Yucca Mountain Site Characterisation Office, Las Vegas, Nevada, December 1997. 

Millard, A. and J. Rutqvist, 2003. Comparative Analyses of Predicted and Measured Displacements During the Heating Phase of the Yucca Mountain Drift Scale Test. Proceedings (to be published). GeoProc2003, Stockholm, Sweden, October 2003. 

Figure I. Three-dimensional view of the Yucca Mountain Drift Scale Test...

Millard, A. Rutqvist, I. 2003. A comparative analysis of predicted and measured displacements during the heating phase of the yucca mountain drift scale test. Geoproc Conf., Stockholm, Sweden. 

The host rocks for the proposed repository at Yucca Mountain include Topopah Spring Upper Lithophysal (Tptpul), Topopah Spring Middle Nonlithophysal (Tptpmn), Topopah Spring Lower Lithophysal (Tptpll), and Topopah Spring Lower Nonlithophysal (Tptpln) units. The drift-scale heater test facility is located in the Tptpmn unit (CRWMS M O, 1997). The Tptpmn unit is 30-40 m thick at the location of the drift-scale test area. This unit is overlain by the Tptpul and underlain by the Tptpll units. The heater drift is approximately 5 m in diameter and 47.5 m long, and its entrance is closed by a thermal bulkhead. 

Datta, R.N. DECOVALEX m PROJECT, Task 2A, Interim Report (Revised). Thermal-Hydrological Predictive Simulation of the Yucca Mountain Project Drift Scale Test, February 2002. 

Abstract As a part of the DECOVALEX 111 project—model predictions were carried out of thermomechanical (TM) rock-mass responses at the Yucca Mountain drift scale test (DST), Nevada. This paper presents model predictions of TM-induced rock displacements at the DST carried out by two independent research teams using two different approaches and two different numerical models. Displacements predicted by the two independent analyses compare reasonably well to the measured ones, both in trends and average magnitude. The analyses indicate that the rock mass behaviour is essentially elastic and that the in situ rock mass thermal expansion coefficient is well represented a temperature-dependent thermal-expansion derived from laboratory tests on intact rock. 

Dana R., Barr, D, Boyle, W., Jing, L. 2003. Measuring the thermal, hydrologic, mechanical and chemical responses of the Yucca Mountain Drift Scale Test. Geoproc Conf, Stockholm, Sweden... 

The long-term performance of the repository at Yucca Mountain will be affected by the coupling of thermal, hydrological and chemical (THC) processes in the rock around the emplacement drifts. The transport of heat, fluid, and vapor will result in changes in water and gas chemistry, as well as mineral dissolution and precipitation which may lead to permanent changes in porosity, permeability and unsaturated hydrological properties. The purpose of this contribution is to describe the approach used to model reaction-transport processes in the Drift Scale Test (DST) with comparisons of simulation results to measured geochemical data on water, gas, and minerals. 

Birkholzer, J, T. Tsang, Y. W. 1998. Interpretive Analysis of the Thermo-Hydrological Processes of the Drift Scale Test. In Drift Scale Test Progress Report, Chapter 6. Yucca Mountain Project Level 4 Milestone SP2930M4. Berkeley, California Lawrence Berkeley National Laboratory. 

The conceptual model in Figure 2, combined with a continuum model approach, is shown to be appropriate for the analysis of THM processes at the DST because the rock mass is highly fractured, forming a dense, wellfracture network for fluid flow. This differs from many other fractured rock sites in Canada, Europe, and Asia, where underground tests have been conducted in sparsely fractured crystalline rocks (Rutqvist and Stephansson, 2003). In those formations, fluid flow is dominated by a few widely spaced fractures, which means that a continuum approach may not apply on the drift scale. In relation to other fractured rock sites, the rock mass at Yucca Mountain is relatively homogenous (ubiquitously fractured), with much less variability in rock-mass mechanical and hydrological properties. 

Abstract Modeling of the drift-scale heater test at the Exploratory Studies Facility at Yucca Mountain, Nevada, U.S.A. was performed. The objectives of the analysis were to investigate the (i) temperature effects on mechanical deformation surrounding the heated drift and (ii) thermal-mechanical effects on rock-mass permeability. The continuum representation of a deformation-permeability relationship based on fracture normal stress was developed to assess rock-mass permeability variations because of temperature changes. The estimated rock-mass displacements and permeability variations as a function of heating time were compared with field measurements. The estimated trend of permeability responses using a normal stress-based deformation-permeability relationship compared reasonably to that measured. 

NUMERICAL SIMULATION OF THERMAL-HYDROLOGICAL PROCESSES OBSERVED AT THE DRIFT-SCALE HEATER TEST AT YUCCA MOUNTAIN, NEVADA... 

Abstract Results from the four-year long heating phase of the Drift-Scale Heater Test at the Exploratory Studies Facility at Yucca Mountain, Nevada, provide a basis to evaluate conceptual and numerical models used to simulate thermal-hydrological coupled processes expected to occur at the proposed repository. A three-dimensional numerical model was built to perform the analyses. All model simulations were predicated on a dual (fracture and matrix) continuum conceptualization. A 20-percent reduction in the canister heat load to account for conduction and radiation heat loss through the bulkhead, a constant pressure boundary condition at the drift wall, and inclusion of the active fracture model to account for a reduction in the number of fractures that were hydraulically active provided the best agreement between model results and observed temperatures. The views expressed herein are preliminary and do not constitute a final judgment of the matter addressed or of the acceptability of its use in a license application... 

---