An investigation of colloidal particles has been completed on leachate
samples collected from sand and soil-filled lysimeters (of the Field
Lysimeter Investigation: Low-Level Waste Data Base Development Program
) in which low-level radioactive waste forms were buried. An array of
analytical techniques including: gamma spectroscopy, liquid scintillat
ion spectrometry, gross alpha and beta particle proportional counting,
energy dispersive X-ray analysis (EDX), neutron activation analysis (
NAA), X-ray fluorescence analysis (XRF), proton induced X-ray emission
analysis (PIXE), gravimetric analysis, and scanning electron microsco
py (SEM), were performed on samples thought to contain colloidal parti
cles to determine particle composition and the nature of their associa
tion with radioactive material. Several different types of particles r
anging in size from 0.02 to 20 mu m were identified within the leachat
e including crystalline calcium hydroxide particles, rounded siliceous
grains, angular weathered soil, and spherical particles apparently co
mposed of an organic polymer. The primary radioactive material associa
ted with these particles was Sr-90. About 2% of the total Sr-90 activi
ty in the leachate is associated with colloidal particles. This inform
ation indicates that colloidal particles play a role in radioactive ma
terial transport through lysimeter soils. (C) 1998 Elsevier Science Lt
d. All rights reserved.