USGS Science⌕ Search

Geology topics

Research about Oak Ridge National Laboratory

Source-linked reports with geographic coverage including Oak Ridge National Laboratory.

6 recordsLinked to original sources
USGS1996

Results of ground-water tracer tests using tritiated water at Oak Ridge National Laboratory, Tennessee

Ground-water tracer tests were conducted at two sites in the radioactive-waste disposal area of Oak Ridge National Laboratory from 1977 to 1982. The purpose of the tests was to determine if the regolith beds had weathered sufficiently to permit the substantial flow of water across them. Regolith of the sites has developed on the Pumpkin Valley Shale and the Nolichucky Shale of the Conasauga Group, both of Cambrian age. About 50 curies of tritium dissolved in water were used as the tracer at one site, and about 100 curies at the other. Distances from the injection wells to a semi-circle of observation wells were 12 and 30 feet, respectively. Results demonstrated that ground water is able to flow through joints in the weathered bedding and that the direction of the water-table gradient is the primary factor governing flow direction. Nevertheless, the substantial lateral spread of the plume as it developed showed that bedding-plane openings, important in controlling flow in the deeper rock, can still exert a significant secondary influence on flow direction in the weathered rock. About 3,500 water samples from the injection and observation wells were analyzed for tritium during the test period. Concentrations detected spanned 11 orders of magnitude. Measurable concentrations were still present in the two injection wells and most observation wells 5 years after the tracer was introduced. Matrix diffusion may have played a significant role in these tests. The process would account for the sustained concentrations of tritium at many of the observation wells, the long-term residual concentrations at the injection and observation wells, and the apparent slow movement of the centers of mass across the two well fields. The process also would have implications regarding aquifer remediation. Other tracer tests have been conducted in the regolith of the Conasauga Group. Results differ from the results described in this report.

Tennessee↗
USGS1989

Construction data and retrieval procedures for selected wells drilled from 1985 through 1987 at Oak Ridge National Laboratory, Tennessee

Twenty-eight wells were constructed by the U. S. Geological Survey for use in describing the groundwater flow system in Melton Valley, at the Oak Ridge National Laboratory in eastern Tennessee. The wells were installed at 18 locations in Melton Valley and along the Clinch River during the period 1985 through 1987. During the same period, 19 wells were constructed by Oak Ridge National Laboratory at 7 locations in or near radioactive-waste burial grounds in Melton Valley. Construction data for all 47 wells are in the U.S. Geological Survey Groundwater Site Inventory data system, where information is also stored for 450 wells that were completed at the laboratory in earlier years. The data can be electronically retrieved by personnel who have access to the U.S. Geological Survey Prime computer located in Nashville, Tennessee, and retrieval procedures are given in the report. (USGS)

Tennessee↗
USGS1988

Hydrology of the Melton Valley radioactive-waste burial grounds at Oak Ridge National Laboratory, Tennessee

Burial grounds 4, 5, and 6 were used sequentially from 195 1 to the present for the disposal of solid, low-level radioactive waste by burial in shallow trenches and auger holes. Abundant rainfall, a generally thin unsaturated zone, geologic media of inherently low permeability, and the operational practices employed have contributed to partial saturation of the buried waste, leaching of radionuclides, and transport of dissolved matter from the burial areas. Two primary methods of transport from these sites are by dissolution in circulating ground water, and the overflow of fluids in trenches and subsequent flow across land surface. The waste-disposal areas are underlain by the Conasauga Group (Cambrian age), a complex sequence of mudstone, siltstone, and limestone interbeds grading from one lithotype to the other, both laterally and vertically. Compressional forces that caused regional thrust faulting also caused much internal deformation of the beds. Folds, bedding-plane faults, and joints are widespread. Small solution openings have developed in some areas where the structurally-related openings have provided ingress to ground water. Both the regolith and bedrock sections of the aquifer are anisotropic, but anisotropy is more pronounced in the bedrock. The lower practical limit of ground-water circulation probably occurs at about 200 to 250 feet depth. A conceptual model of flow is described wherein the primary control on direction of ground-water flow changes from the water-table gradient in the regolith to the hydraulic head distribution within the secondary openings of the bedrock and the three-dimensional geometry of those openings. Locally, the direction of flow in the regolith also is controlled by gradients within openings in certain relatively resistant beds and structurally-related features. Hydraulic conductivities as measured by slug tests of wells range from 2.9 x 10m3 to 6.7 feet per day in the regolith, and 1.5 x 10s4 to 1.9x 10-l feet per day in bedrock at depths of 100 to 200 feet. Whiteoak Creek and its tributaries receive all overland flow from trench spillage, surface runoff from each site, and discharge of ground water from the regolith of each site. Potentiometric data indicate that this drainage system also receives ground water discharged from the bedrock of burial ground 5. By projection of the bedrock flow patterns characteristic of this site to other areas of Melton Valley, it is inferred that discharge from the bedrock underlying burial grounds 4 and 6 also is to the same drainage system. The differences in potentiometric heads and a comparatively thin saturated zone in bedrock do not favor the development of deep flow through bedrock from one river system to another. Hydraulic potentials, hydraulic conductivities, and hydrochemical data indicate that most ground water in the aquifer flows through the regolith. A smaller amount of water flows through the bedrock, where the flow paths are longer in distance and the time of travel is considerably greater. In burial ground 5 the regolith section of the aquifer has widespread contamination, principally by iron, tritium, and strontium-90. Contamination decreases substantially with increasing depth in bedrock, particularly below 100 feet. The sites have received little monitoring because they have not been considered a hazard. As improvements in plant facilities have reduced the discharge of radionuclides to the Whiteoak Creek system, the discharge of contaminants from the burial grounds has become relatively more significant. The burial grounds are now a principal source of 3H and a major contributor of 90 Sr in the discharge of Whiteoak Creek to the Clinch River.

Tennessee↗
USGS1982

Precipitation data for burial grounds 5 and 6, Oak Ridge National Laboratory, Tennessee, 1976-1980

As part of a hydrogeologic investigation, precipitation data were collected at two stations, one each in Burial Grounds 5 and 6 at the Oak Ridge National Laboratory, Tennessee. Daily, monthly, and annual values are reported herein for the period from January 1976 through December 1980. During this period, annual values ranged from about 25 percent above to about 25 percent below the calculated mean of 51.96 inches at Burial Ground 5 and 49.60 inches at Burial Ground 6.

Tennessee↗
USGS1977

Possibility of triggering earthquakes by injection of radioactive wastes in shale at Oak Ridge National Laboratory, Tenn.

Most investigators generally agree that the conditions for producing earthquakes by fluid injection through wells and by reservoir construction are (1) the presence of an underlying rock that is stressed to the verge of fracturing by tectonic stresses and (or) is on the brink of sliding on pre-existing fault planes, (2) the presence of potentially active faults(s), and (3) an increase of pore pressure in the rock caused by fluid injection or seepage from reservoir (s), which is probably the triggering force. The mechanism of disposal of radioactive wastes in shale by grout injection and hydraulic fracturing, which has been used at ORNL (Oak Ridge National Laboratory, Tenn.) is different from injection of fluid. The injected grout is in its liquid phase only during the injection period and, it is to be hoped, is confined in the hydraulically induced bedding-plane fractures. The grout is then allowed to solidify under pressure after termination of the injection, and, after solidification, it becomes an integral part of the shale. Significant characteristics of the disposal method and the site are as follows: (1) Because of the low permeability of shale and high viscosity of the injection grout, pore pressure in the rock, beyond the region of induced fractures, does not increase due to the injections; the injected grout enters newly formed bedding-plane fractures, (2) the injection site is free of local faults and of major interconnected joints and fractures; accordingly, injected grout in its liquid state is expected to be confined principally in the induced nearly horizontal bedding-plane fractures, and (3) due to low tensile strength along shale bedding planes, the energy needed to induce bedding-plane fractures is small; experiments made at ORNL indicate that the energy released during hydraulic fracturing in shale is so small that seismic signals generated by grout injections cannot be differentiated from ambient ground vibrations. In view of the fact 'that an increase of pore pressure in rock (the triggering force) and association with potentially active fault (s) do not occur at the proposed site at ORNL and that the disposal method does not produce an increase in pore pressure, it can reasonably be concluded that neither the method nor the site has the characteristics for triggering earthquakes during and after grout injections.

Tennessee↗