Vegetative uptake of technetium-99 from buried, solidified, low-level radioactive waste

Journal Article · Fri Oct 01 04:00:00 EDT 1993 · Journal of Environmental Quality

DOI:https://doi.org/10.2134/jeq1993.00472425002200040022x· OSTI ID:223878

Murphy, Jr, C E ^[1]; Johnson, T L ^[2]

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1. Westinghouse Savannah River Co., Aiken, SC (United States)
2. Savannah River Lab., Aiken, SC (United States)

At the Savannah River Site, liquid, low-level nuclear waste will be disposed by incorporating the waste into a solid, concrete waste form called saltstone. Saltstone monoliths will be buried in claycapped, subterranean vaults. Although the vault/cap burial system is designed to severely limit the access of vegetative roots to the saltstone, a study was begun In 1984 to determine the potential for root uptake of radionuclides. Thirty-two lysimeters were constructed and filled with soil. Saltstone samples, containing the liquid, low-level supernate from a waste disposal demonstration program, were buried in some of the lysimeters, at varying depths to investigate the relationship between source depth and plant uptake. Crops, grass, and trees were planted in the lysimiters and sampled periodically. Water samples also were collected from the lysimeter sumps and analyzed for radionuclide content. In the 5 yr following establishment of the lysimeters, only technetium-99 (Tc-99) and cesium-137 (Cs-137) could be detected at elevated concentrations In the vegetation. The Cs-137 concentration difference between the plants grown in control and saltstone lysimeters was barely detectable against background. The Tc-99 concentration was significantly higher in vegetation and sump water of lysimeters containing saltstone, when compared to the control lysimeters. The Tc-99 uptake by vegetation and sump waters appears to be related to release of the Tc-99 from the saltstone into soft water. Similar patterns exist: initial period of very low concentrations,then a coincident buildup period and a period of relatively uniform concentration. Vegetative uptake factors were calculated for uptake of Tc-99 from soil water. The results were very similar for the vegetative parts of all the species grown, 111 to 376 (nBq/kg{sub vegetation})/(nBq/kg{sub water}). The uptake factor calculated for the seeds of crops was less by a factor of 100 than the uptake factor for vegetative parts.

• OSTI ID: 223878
• Journal Information: Journal of Environmental Quality, Journal Name: Journal of Environmental Quality Journal Issue: 4 Vol. 22; ISSN JEVQAA; ISSN 0047-2425
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
54 ENVIRONMENTAL SCIENCES
BIOLOGICAL ACCUMULATION
EVALUATION
LEACHING
LOW-LEVEL RADIOACTIVE WASTES
PLANTS
SOLIDIFICATION
TECHNETIUM 99
UNDERGROUND STORAGE