Biomedical subjects

Chin-Fu Tsang

Publications and source records attributed to Chin-Fu Tsang.

3 recordsLinked to original sources

PubMedDate not supplied

Seepage into drifts with mechanical degradation.

Seepage into drifts in unsaturated tuff is an important issue for the long-term performance of the proposed nuclear waste repository at Yucca Mountain, Nevada. Drifts in which waste packages will be emplaced are subject to degradation in the form of rockfall from the drift ceiling, induced by stress-relief, seismic, or thermal effects. The objective of this study is to calculate seepage rates, for various drift-degradation scenarios and for different values of percolation flux, in the Topopah Spring middle nonlithophysal (Tptpmn) and the Topopah Spring lower lithophysal (Tptpll) units at Yucca Mountain. Seepage calculations are conducted by (1) defining a heterogeneous drift-scale permeability model with field data, (2) selecting calibrated parameters associated with the Tptpmn and Tptpll units, and (3) simulating seepage, based on detailed degraded-drift profiles obtained from a separate rock mechanics engineering analysis. The simulation results indicate (1) that the seepage threshold (i.e., the percolation flux at which seepage first occurs) is not significantly changed by drift degradation and (2) the degradation-induced increase in seepage above the threshold is influenced probably more by the shape of the cavity created by rockfall than by rockfall volume.

Geological Phenomena↗

PubMedDate not supplied

Analysis of thermal-hydrologic-mechanical behavior near an emplacement drift at Yucca Mountain.

A coupled thermal, hydrologic and mechanical (THM) analysis is conducted to evaluate the impact of coupled THM processes on the performance of a potential nuclear waste repository at Yucca Mountain, Nevada. The analysis considers changes in rock mass porosity, permeability, and capillary pressure caused by rock deformations during drift excavation, as well as those caused by thermomechanically induced rock deformations after emplacement of the heat-generating waste. The analysis consists of a detailed calibration of coupled hydraulic-mechanical rock mass properties against field experiments, followed by a prediction of the coupled thermal, hydrologic, and mechanical behavior around a potential repository drift. For the particular problem studied and parameters used, the analysis indicates that the stress-induced permeability changes will be within one order of magnitude and that these permeability changes do not significantly impact the overall flow pattern around the repository drift.

Mechanics↗

PubMedDate not supplied

Is current hydrogeologic research addressing long-term predictions?

Hydrogeology is a field closely related to the needs of society. Many problems of current national and local interest require predictions of hydrogeological system behavior, and in a number of important cases, the period of prediction is tens to hundreds of thousands of years. It is argued that the demand for such long-term hydrogeological predictions casts a new light on the future needs of hydrogeological research. Key scientific issues are no longer concerned only with simple processes or narrowly focused modeling or testing methods but also with assessment of prediction uncertainties and confidence, couplings among multiple physicochemical processes occurring simultaneously at a site, and the interplay between site characterization and predictive modeling. These considerations also have significant implications for hydrogeological education. With this view, it is asserted that hydrogeological directions and education need to be reexamined and possibly refocused to address specific needs for long-term predictions.

Forecasting↗