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A handbook for the determination of radon attenuation through cover materials

Description: Radon emissions from bare and covered uranium mill tailings can be estimated by diffusion theory if appropriate diffusion coefficients are known. The mathematical basis for the diffusion theory expressions are herein presented, as is a general survey of previous and present research, as well as technological developments associated with randon transport through tailing cover systems. Research is presently being conducted to define more clearly the influences of moisture, porosity, pore size distribution and other factors, on the attenuative properties of cover materials. The results of these present investigations will be incorporated in a subsequent addendum to this handbook. The radon fluxes or cover thicknesses can be calculated by hand or by available computer programs. The equations and procedure for the hand calculations is in direct support of the methodology contained in Appendix P of the Generic Environmental Impact Statement on Uranium Milling. Several examples are given to demonstrate the methodology.
Date: December 1, 1981
Creator: Rogers, V. C. & Nielson, K. K.
Partner: UNT Libraries Government Documents Department

Mathematical model for radon diffusion in earthen materials

Description: Radon migration in porous, earthen materials is characterized by diffusion in both the air and water components of the system as well as by the interaction of the radon between the air and water. The size distribution and configuration of the pore spaces and their moisture distributions are key parameters in determining the radon diffusion coefficient for the bulk material. A mathematical model is developed and presented for calculating radon diffusion coefficients solely from the moisture content and pore size distribution of a soil, reducing the need for resorting to radon diffusion measurements. The resulting diffusion coefficients increase with the median pore diameter of the soil and decrease with increasing widths of the pore size distribution. The calculated diffusion coefficients are suitable for use in simple homogeneous-medium diffusion expressions for predicting radon transport and compare well with measured diffusion coefficients and with empirical diffusion coefficient correlations.
Date: October 1, 1982
Creator: Nielson, K.K. & Rogers, V.C.
Partner: UNT Libraries Government Documents Department

Relationship of observed flow patterns to gas core reactor criticality

Description: The gas core reactor requires the establishment of stable and unique flow patterns. A recent series of room temperature flow tests have studied the hydrodynamics, particularly involving gases of differing densities. In an actual operating gas core reactor, the central gas of vaporized uranium will have a much higher density than the surrounding coolant. Testing was done in two different sized chambers (18 inch and 36 inch diameter) to study hydrodynamic scaling. Air was employed as the ''coolant'' gas. Air, argon, and freon, smoked for identification, was used to simulate the fuel. A variety of injectors at various locations in the cavity were employed. (auth)
Date: January 1, 1975
Creator: Macbeth, P.J.; Kunze, J.F. & Rogers, V.C.
Partner: UNT Libraries Government Documents Department

Characterization of radon penetration of different structural domains of concrete. Final project report

Description: This report documents the research activities by Rogers and Associates Engineering Corporation on grant DE-FG03-93ER61600 during the funded project period from August 1993 to April 1996. The objective of this research was to characterize the mechanisms and rates of radon gas penetration of the different structural domains of the concrete components of residential floor slabs, walls, and associated joints and penetrations. The research was also to characterize the physical properties of the concretes in these domains to relate their radon resistance to their physical properties. These objectives support the broader goal of characterizing which, if any, concrete domains and associated properties constitute robust barriers to radon and which permit radon entry, either inherently or in ways that could be remediated or avoided.
Date: May 1, 1996
Creator: Nielson, K.K. & Rogers, V.C.
Partner: UNT Libraries Government Documents Department

Predicting long-term moisture contents of earthen covers at uranium mill tailings sites

Description: The three methods for long-term moisture prediction covered in this report are: estimates from water retention (permanent wilting point) data, correlation with climate and soil type, and detailed model simulation. The test results have shown: soils vary greatly in residual moisture. Expected long-term moisture saturation ratios (based on generalized soil characteristics) range from 0.2 to 0.8 for soils ranging in texture from sand to clay, respectively. These values hold for noncompacted field soils. Measured radon diffusion coefficients for soils at 15-bar water contents ranged from 5.0E-2 cm/sup 2//s to 5.0E-3 cm/sup 2//s for sands and clays, respectively, at typical field densities. In contrast, fine-textured pit-run earthen materials, subjected to optimum compaction (>85% Proctor density) and dried to the 15-bar water content, ranged from 0.7 to 0.9 moisture saturation. Compacted pit-run soils at these moisture contents exhibited radon diffusion coefficients as low as 3.0E-4 cm/sup 2//s. The residual moisture saturation for cover soils is not known since no engineered barrier has been in place for more than a few years. A comparison of methods for predicting moisture saturation indicates that model simulations are useful for predicting effects of climatic changes on residual soil moisture, but that long-term moisture also can be predicted with some degree of confidence using generalized soil properties or empirical correlations based both on soils and climatic information. The optimal soil cover design will likely include more than one layer of soil. A two-layer system using a thick (1-m minimum) plant root zone of uncompacted soil placed over a moistened, tightly compacted fine-textured soil is recommended. This design concept has been tested successfully at the Grand Junction, Colorado, tailings piles.
Date: September 1, 1984
Creator: Gee, G.W.; Nielson, K.K. & Rogers, V.C.
Partner: UNT Libraries Government Documents Department

Radon attenuation handbook for uranium mill tailings cover design

Description: This handbook has been prepared to facilitate the design of earthen covers to control radon emission from uranium mill tailings. Radon emissions from bare and covered uranium mill tailings can be estimated from equations based on diffusion theory. Basic equations are presented for calculating surface radon fluxes from covered tailings, or alternately, the cover thicknesses required to satisfy a given radon flux criterion. Also described is a computer code, RAECOM, for calculating cover thicknesses and surface fluxes. Methods are also described for measuring diffusion coefficients for radon, or for estimating them from empirical correlations. Since long-term soil moisture content is a critical parameter in determining the value of the diffusion coefficient, methods are given for estimating the long-term moisture contents of soils. The effects of cover defects or advection are also discussed and guidelines are given for determining if they are significant. For most practical cases, advection and cover defect effects on radon flux can be neglected. Several examples are given to demonstrate cover design calculations, and an extensive list of references is included. 63 references, 18 figures, 6 tables.
Date: April 1, 1984
Creator: Rogers, V.C.; Nielson, K.K. & Kalkwarf, D.R.
Partner: UNT Libraries Government Documents Department

Contaminant pathway analysis and health risk assessment of the Metallurgical Laboratory Basin

Description: The specific objectives of this report are to present a technically detailed site description for the Metallurgical Laboratory basin, to document the manner in which it was modeled by the PATHRAE computer code, and to present the results of the pathway analyses, in terms of both contaminant transport and health risks. This will provide part of a detailed assessment of environmental risks and impacts from the Metallurgical Laboratory both in its present condition and after possible remedial actions to aid in selection of the appropriate remedial action options. In a broader sense, these objectives support the general SRP (Savannah River Plant) operations policy of protecting the environment and the health and safety of the public and operating personnel.
Date: December 1, 1985
Creator: Klein, R. B.; Merrell, G. B.; Nielson, K. K. & Rogers, V. C.
Partner: UNT Libraries Government Documents Department

Comparison of radon diffusion coefficients measured by transient-diffusion and steady-state laboratory methods

Description: A method was developed and used to determine radon diffusion coefficients in compacted soils by transient-diffusion measurements. A relative standard deviation of 12% was observed in repeated measurements with a dry soil by the transient-diffusion method, and a 40% uncertainty was determined for moistures exceeding 50% of saturation. Excellent agreement was also obtained between values of the diffusion coefficient for radon in air, as measured by the transient-diffusion method, and those in the published literature. Good agreement was also obtained with diffusion coefficients measured by a steady-state method on the same soils. The agreement was best at low moistures, averaging less than ten percent difference, but differences of up to a factor of two were observed at high moistures. The comparison of the transient-diffusion and steady-state methods at low moistures provides an excellent verification of the theoretical validity and technical accuracy of these approaches, which are based on completely independent experimental conditions, measurement methods and mathematical interpretations.
Date: November 1, 1982
Creator: Kalwarf, D.R.; Nielson, K.K.; Rich, D.C. & Rogers, V.C.
Partner: UNT Libraries Government Documents Department

Laboratory research on tailings stabilization methods and their effectiveness in radiation containment. [Uranium, reduction of radon exhalation]

Description: This report describes a study of various methods, techniques, and materials for stabilizing uranium mill tailings to reduce radon exhalation. Radon emanation from tailings particles, radon exhalation from tailings, and methods that could be used to reduce radon exhalation from tailings piles are discussed. Surface radon flux and soil gas concentrations were measured in experiment chambers or columns consisting of uranium tailings and various types and thicknesses of cover materials. The applicability of diffusion theory was examined and effective diffusion coefficients were determined for clay, soil, and sand. The variation of radon flux with atmospheric effects and moisture also was investigated. The effectiveness of several types of chemical stabilizers for both volumetric and surface application in reducing radon exhalation is reported. Some volumetric stabilizers reduced radon flux by 90 percent or more. Radon flux was determined through the use of charcoal gas mask canisters, and flux accumulation chambers sampled by Lucas cells. Both of these techniques are described. Soil gas concentration was sampled with Lucas cells and counted with a sodium iodide scintillation spectrometer system. Emanating power of uranium tailings was measured for several particle sizes and found to be relatively constant at about 20 percent. Two types of grasses were found that would grow in tailings if sufficient water and fertilizer were provided. The effect of vegetation on radon exhalation was not determined.
Date: April 1, 1978
Creator: Macbeth, P.J.; Jensen, C.M.; Rogers, V.C. & Overmyer, R.F.
Partner: UNT Libraries Government Documents Department

Lung cancer risks in the vicinity of uranium tailings sites. [UMTRA Project]

Description: Lung cancer mortality data have been assembled for many counties of interest to the Uranium Mill Tailings Remedial Action Program (UMTRAP). The counties generally either contain UMTRAP tailings sites or are adjacent to them. The lung cancer rates of nearly all counties are less than the US average rate. In addition, some of the many factors associated with lung cancer are identified as are cancer risk estimators for radon daughters. 17 refs., 19 figs., 1 tab.
Date: April 1, 1982
Creator: Rogers, V.C. & Sandquist, G.M. (Rogers and Associates Engineering Corp., Salt Lake City, UT (USA))
Partner: UNT Libraries Government Documents Department

Small-scale field test of simple earthen covers for uranium mill tailings. [Uranium Mill Tailings Remedial Action Project]

Description: A series of field tests has been conducted during the past year to provide benchmark data on the performance of simple, single-layer earthen covers at thee uranium tailings sites. The performance of the covers was evaluated in terms of their reduction of radon gas releases, although moisture profiles and other cover parameters were also monitored. The tests were designed to evaluate the effectiveness of local soils applied with minimum engineering design or compaction effort. The tests, therefore, tend to represent a lowest-cost, and perhaps a worst-case scenario for tailings reclamation. The field benchmark tests are part of a major research program being conducted by the US Department of Energy to develop technology for uranium tailings disposal. The present tests with simple earthen covers thus provide a comparative basis for evaluating the effectiveness of more highly-engineered systems and their proportionately higher costs. These tests were conducted on the inactive tailings piles at Salt Lake City; Mexican Hat, Utah; and Grand Junction, Colorado. The test covers were installed during the summer of 1981 (Ri81) and have been monitored during the following year. This report describes the experimental details of the cover tests, the data that were collected during the one-year monitoring period, and the conclusions that were drawn from the experiments. 5 refs., 5 figs., 13 tabs.
Date: January 1, 1983
Creator: Nielson, K.K.; Rogers, V.C. & Rich, D.C. (Rogers and Associates Engineering Corp., Salt Lake City, UT (USA))
Partner: UNT Libraries Government Documents Department

Laboratory measurements of radon diffusion through multilayered cover systems for uranium tailings

Description: Laboratory measurements of radon fluxes and radon concentration profiles were conducted to characterize the effectiveness of multilayer cover systems for uranium tailings. The cover systems utilized soil and clay materials from proposed disposal sites for the Vitro, Durango, Shiprock, Grand Junction and Riverton tailings piles. Measured radon fluxes were in reasonable agreement with values predicted by multilayer diffusion theory. Results obtained by using air-filled porosities in the diffusion calculations were similar to those obtained by using total porosities. Measured diffusion coefficients were a better basis for predicting radon fluxes than were correlations of diffusion coefficient with moisture or with air porosity. Radon concentration profiles were also fitted by equations for multilayer diffusion in the air-filled space. Layer-order effects in the multilayer cover systems were examined and estimated to amount to 10 to 20 percent for the systems tested. Quality control measurements in support of the multilayer diffusion tests indicated that moisture absorption was not a significant problem in radon flux sampling with charcoal canisters, but that the geometry of the sampler was critical. The geometric design of flux-can samplers was also shown to be important. Enhanced radon diffusion along the walls of the test columns was examined and was found to be insignificant except when the columns had been physically disturbed. Additional moisture injected into two test columns decreased the radon flux, as expected, but appeared to migrate into surrounding materials or to be lost by evaporation. Control of moisture content and compaction in the test columns appeared to be the critical item affecting the accuracies of the experiments.
Date: December 1, 1981
Creator: Nielson, K.K.; Rogers, V.C.; Rich, D.C.; Nederhand, F.A.; Sandquist, G.M. & Jensen, C.M.
Partner: UNT Libraries Government Documents Department