Monitoring radionuclide contamination in the unsaturated zone - Lessons learned at the Amargosa Desert Research Site, Nye County, Nevada

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Abstract

Contaminant-transport processes are being investigated at the U.S. Geological Survey’s Amargosa Desert Research Site (A DRS), adjacent to the Nation’s first commercial disposal facility for low-level radioactive waste. Gases containing tritium and radiocarbon are migrating through a 110-m thick unsaturated zone from unlined trenches that received waste from 1962 to 1992. Results relevant to long- term monitoring of radionuclides are summarized as follows. Contaminant plumes have unexpected histories and spatial configurations due to uncertainties in the: (1) geologic framework, (2) biochemical reactions involving waste components, (3) interactions between plume components and unsaturated-zone materials, (4) disposal practices, and (5) physical transport processes. Information on plume dynamics depends on ex-situ wet-chemical techniques because in-situ sensors for the radionuclides of interest do not exist. As at other radioactive-waste disposal facilities, radionuclides at the ADRS are mixed with varying amounts of volatile organic compounds (VOCs). Carbon-dioxide and VOC anomalies provide proxies for radioactive contamination. Contaminants in the unsaturated zone migrate along preferential pathways. Effective monitoring thus requires accurate geologic characterization. Direct- current electrical-resistivity imaging successfully mapped geologic units controlling preferential transport at the ADRS. Direct sampling of water from the unsaturated zone is complex and time consuming. Sampling plant water is an efficient alternative for mapping shallow tritium contamination.

Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Monitoring radionuclide contamination in the unsaturated zone - Lessons learned at the Amargosa Desert Research Site, Nye County, Nevada
Chapter 6.4
Year Published 2004
Language English
Publisher Center for Integrated Sensor Technology and Environmental Monitoring Systems
Contributing office(s) Nevada Water Science Center
Description 6 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Proceedings, Workshop on long-term performance monitoring of metals and radionuclides in the subsurface
Conference Title Joint workshop on long-term monitoring of metals and radionuclides in the subsurface: Strategies, tools and case studies
Conference Location Reston, VA
Conference Date April 21-22, 2004
Country United States
State Nevada
County Nye County
City Beatty
Other Geospatial Amargosa Desert Research Site