SYMPOSIA PAPER Published: 01 January 1989
STP22892S

Influence of Hydrologic Factors on Leaching of Solidified Low-Level Waste Forms at an Arid-Site Field-Scale Lysimeter Facility

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The release of contaminants from solidified low-level waste forms is being studied in a field lysimeter facility at the Hanford Site in southeastern Washington State. The lysimeter facility, constructed in 1984, consists of ten 3-m-deep by 1.8-m-diameter steel caissons surrounding a 4-m-deep central instrument caisson. Each lysimeter contains one field-scale waste form (210-L barrel), obtained from a commercial power reactor. Solidification agents being tested include masonry cement, Portland III cement, Dow polymer, and bitumen.

Most of the precipitation at the Hanford Site arrives as winter snow; this contributes to a strong seasonal pattern in water storage and drainage observed in the lysimeters. This seasonal pattern in storage corresponds to an annual range in the volumetric soil water content of 11% in late winter to 7% in the late summer and early fall. Annual changes in drainage rates cause pore water velocities to vary by nearly two orders of magnitude, from approximately 4 cm/week in early spring to less than 0.01 cm/week in early fall.

Measurable quantities of tritium and cobalt-60 are being collected in lysimeter drainage water. Approximately 30% of the original tritium inventory has been leached from the only two waste forms containing tritium. Cobalt-60 is contained in all waste form samples and is consistently being leached from five lysimeters. Total cobalt-60 collected from each of the five lysimeters varies, but in each case is less than 0.1% of the original cobalt inventory of the waste sample.

Author Information

Jones, TL
Pacific Northwest Laboratory, Richland, WA
Skaggs, RL
Pacific Northwest Laboratory, Richland, WA
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Details
Developed by Committee: D34
Pages: 358–380
DOI: 10.1520/STP22892S
ISBN-EB: 978-0-8031-5090-4
ISBN-13: 978-0-8031-1261-2