Proceedings of the Radon Barriers Workshop (NUREG/CP-0312)

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Publication Information

Manuscript Completed: June 2019
Date Published: August 2019

Prepared by:
Prepared by: Mark Fuhrmann¹, Craig Benson², Jody Waugh³, Morgan Williams⁴, and Hans Arlt¹

¹ U.S. Nuclear Regulatory Commission
² University of Virginia
³ Navarro Research and Engineering, Inc.
⁴ University of California Berkeley

Mark Fuhrmann, NRC Project Manager

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

The "Radon Barriers Project" is a research program to study the effects of changes in the properties of in-service engineered earthen covers over uranium mill tailings as these covers age. Field studies were conducted at four mill tailing disposal sites: Falls City in Texas, Bluewater in New Mexico, Shirley Basin South in Wyoming, and Lakeview in Oregon. Small areas on these sites were excavated, radon fluxes were measured, numerous observations were made, and samples were taken for a variety of parameters, such as saturated hydraulic conductivity, root counts, moisture, density, lead-210 concentrations, soil texture, structure, chemistry, and nematode counts.

On July 25–26, 2018, a one-and-a-half-day workshop took place at NRC Headquarters to discuss findings from the project with regard to the current state of the barriers and comparison to their as-built condition and natural analog sites, prediction of long-term evolution, monitoring approaches, and long-term implications. Presentations included detailed background and project findings on the following:

• NRC and DOE/LM activities that led to the Radon Barriers Project

• radon fluxes and their variability, radon diffusion coefficients, and radon travel times through the covers

• hydraulic conductivity of the barriers at various depths and comparisons to hydraulic conductivity at nearby natural analog sites

• ecological evolution of covers and the impact of vegetation on cover properties, especially on water percolation, radon flux, and evapotranspiration

• soil architecture observations, including soil structure, biology, and chemistry

• potential use of lead-210 as a long-term indicator of radon transport within barriers

A facilitated discussion followed each presentation to discuss long-term evolution of the sites as suggested by the project findings, use of the findings for maintenance and prediction, future information needs, and policy implications.