This report summarizes the results of the in situ thermophysical properties measurements as part of the Drift Scale Test (DST) measurement program at Yucca Mountain, Nevada. Thermophysical measurements have been performed with three built-in thermal probes since November 13, 1997 and were expected to continue for three more years until the end of the DST cooling period. The Department of Energy (DOE), under Cooperative Agreement, Number DEFC28- 98NV12081, has funded a research project at the University of Nevada, Reno since November, 1999 titled: "Continuing site characterization and performance verification applications with the REKA method at Yucca Mountain, Task 13." This project is also referred to as "Drift Scale Tests," the previous title of a research project that was funded by a different contract from the DOE from 1997 to 1999 under M&O task WBS 126.96.36.199 (123E2265M1). The thermophysical properties include thermal conductivity and diffusivity, each pair determined simultaneously from an in situ temperature field measurement around a single-borehole thermal probe, using inverse modeling. The application of the method and apparatus have practiced U.S. patent 4,933,887, assigned to Sierra Science of Reno, NV. The method is called Rapid Evaluation of K and Alpha (REKA), referring to the determination of thermal conductivity and diffusivity from a single measurement. The application of the REKA method during the project period resulted in the submission of over 330 in situ, effective conductivity and diffusivity pairs during the reported period. The scope of work for Task 13, approved in 1999, included the design and fabrication of three new thermal probes for the use in the Enhanced Characterization of the Repository Block (ECRB) activity, as well as in subsequent performance verification. The promise of long-term application and measurement continuation at Yucca Mountain served as the basis for waiving the license fee for U.S. Patent 4,933,887 for the project. However, the scope of work for Task 13 was re-defined during the course of the work by DOE and M&O personnel, documented in the Scientific Notebook UCCSN-UNR-013 entries between May 2000 and November 2000. According to the new scope, re-usable REKA probes were needed, as a procurement of the method for the use in the lithophysal rock formation for a third party. Although the protracted decisions regarding the intellectual property issues effectively prevented the completion of the new probes and their application in site characterization, the design of the probes and the method evaluation for lithophysal application have been completed during the reported period. The in situ measurement results have shown that the effective thermophysical properties variations were moderate with mean values around the expected, conduction-only values, except for the readings taken when the boiling front was at or around the location of Probe 1. Thermophysical properties variations within a 10-20% regime indicate that the heat flow has been conduction-dominated around all three REKA probes in the DST during the study period excluding the time of the boiling front condition at a probe location. Slow, as well as periodic changes in the effective conductivity and diffusivity values were also observed, that may be attributed to convective and evaporative effects as well as moisture content changes. In addition, Probe 1 recorded consistent pool boiling for over a year in an area known to be in the condensate shredding zone.
Nevada – Yucca Mountain; Rocks – Temperature
Earth Sciences | Geology | Geophysics and Seismology
Smiecinski, A. J.
Drift scale test: Analyze and report.
Available at: https://digitalscholarship.unlv.edu/yucca_mtn_pubs/74