Potential for radionuclide redistribution due to biotic intrusion: Aboveground biomass study at the Los Alamos National Laboratory for the closure of Material Disposal Area G
- QinetiQ North America Operations LLC, Los Alamos, NM (United States)
- Los Alamos National Laboratory, Los Alamos, NM (United States)
- URS Corporation (United States)
Low-level radioactive waste generated at the Los Alamos National Laboratories (LANL) is disposed of at Technical Area (TA) 54, Material Disposal Area (MDA) G. The ability of MDA G to safely contain radioactive waste was evaluated in the facility's performance assessment (PA) and composite analysis (CA). The PA and CA project that, due to uptake and incorporation of radionuclides into aboveground plant material, plant roots penetrating into buried waste may lead to releases of radionuclides to the accessible environment and potentially lead to the exposure to members of the public. The potential amount of contamination deposited on the ground surface, due to plant intrusion into buried waste, is a function of the quantity of litter generated by plants, as well as radionuclide concentrations within the litter. Radionuclide concentrations in plant litter is dependent on the distribution of root mass with depth and the efficiency with which radionuclides are extracted from contaminated soils by the plants roots. In order to reduce uncertainties associated with the PA and CA for MDA G, aboveground biomass surveys, plant litter production rates, and root mass with depth analyses for the four prominent vegetation types (grasses, forbs, shrubs and trees) are being conducted. Sampling occurred during the months of August and September of 2007 which measured aboveground biomass for the types of grasses and forbs that may become established at MDA G after the disposal facility undergoes final closure. Biomass data are representative of the future potential for the amount of contaminated plant litter fall, which could act as a latent conduit for radionuclide transport from the closed disposal area. Follow on work will be conducted to evaluate frequency and coverage of all growth forms, litter production rates will be measured, and root mass with depth for grasses, forbs, shrubs, and trees will be analyzed. Together, data collected are expected to reduce uncertainties associated with the PA and CA for MDA G and ultimately aid in the prevention of radionuclide transport within the environment from the closed disposal area and exposure to the public. In summary: Collection of aboveground grasses and forbs at TA-54 resulted in dry-weight biomass data for two of the four growth forms of interest for the MDA G PA and CA. Shrubs were not encountered in any of the grid cells selected for sampling. Trees were not encountered within MDA J. Mature trees (Juniper) were located in five grid cell locations at Zone 4. Dead and down trees (Pinon) were located in two of the grid cells at Zone 4. The grid size at MDA J was reduced to 15.2 m by 15.2 m (50 ft by 50 ft) because of the anticipated mass to be collected. MDA J has achieved a relatively uniform grass and forbs coverage, and due to time constraints the size was reduced by half. Material that was originally oven dried was weighed again after several weeks. Data from post oven drying reports weight gain, indicating a higher error associated with air versus oven drying methodology. The drying methods will be explored in greater depth with future studies. Future surveys will include measurement of aboveground biomass of shrubs and trees, measurement of litter production rates; root mass with depth for grasses, forbs, shrubs, and trees; and frequency and coverage surveys to determine the percent coverage of each growth form. The collection of this additional data will provide further site-specific information regarding the growth of grasses, forbs, shrubs, and trees within the expected successional growth stages expected at MDA G. These data will be incorporated into the biotic intrusion modeling for the MDA G PA and CA. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9 - 332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 21326180
- Report Number(s):
- INIS-US-10-WM-08502; TRN: US10V0658067545
- Resource Relation:
- Conference: WM'08: Waste Management Symposium 2008 - HLW, TRU, LLW/ILW, Mixed, Hazardous Wastes and Environmental Management - Phoenix Rising: Moving Forward in Waste Management, Phoenix, AZ (United States), 24-28 Feb 2008; Other Information: Country of input: France; 3 refs
- Country of Publication:
- United States
- Language:
- English
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