Physics
Scientific paper
Mar 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000gecoa..64..867l&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 64, Issue 5, pp.867-881
Physics
9
Scientific paper
Uranium and thorium-decay series disequilibria in groundwater occur as a result of water-rock interactions, and they provide site-specific, natural analog information for assessment of in-situ, long-term migration of radionuclides in the far field of a nuclear waste disposal site. In this study, a mass balance model was used to relate the decay-series radionuclide distributions among solution, sorbed and solid phases in an aquifer system to processes of water transport, sorption-desorption, dissolution-precipitation, radioactive ingrowth-decay, and recoil. Isotopes of U ( 238 U, 234 U), Th ( 232 Th, 230 Th, 228 Th, 234 Th), Ra ( 226 Ra, 228 Ra, 224 Ra), and Rn ( 222 Rn) were measured in 23 groundwater samples collected from a basaltic aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho. The results show that groundwater activities of Th and Ra isotopes are 2-4 orders lower than those of their U progenitors which average 1.35 ± 0.40 dpm 238 U/L, with 234 U/ 238 U ratios of ~1.6-3.0. 222 Rn activities range from 20 to 500 dpm/L. Modeling of the observed disequilibria places the following constraints on the time scale of radionuclide migration and water-rock interaction at INEEL: (1) Time for sorption is minutes for Ra and Th; time for desorption is days for Ra and years for Th; and time for precipitation is days for Th, years for Ra, and centuries for U. (2) Retardation factors due to sorption average >10 6 for 232 Th, ~10 4 for 226 Ra, and ~10 3 for 238 U. (3) Dissolution rates of rocks are ~70 to 800 mg/L/y. (4) Ages of groundwater range from <10 to 100 years. Contours of groundwater age, as well as spatial patterns of radionuclide disequilibria, delineate two north-south preferential flow pathways and two stagnated locales. Relatively high rates of dissolution and precipitation and -recoil of 222 Rn occur near the groundwater recharging sites as well as in the major flow pathways. Decay of the sorbed parent radionuclides (e.g., 226 Ra and 228 Ra) on micro-fracture surfaces constitutes an important source of their daughter ( 222 Rn and 228 Th) activities in groundwater.
Ku Teh-Lung
Luo Shangde
McLing Travis L.
Murrell Michael
Roback Robert
No associations
LandOfFree
In-situ radionuclide transport and preferential groundwater flows at INEEL (Idaho): decay-series disequilibrium studies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with In-situ radionuclide transport and preferential groundwater flows at INEEL (Idaho): decay-series disequilibrium studies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and In-situ radionuclide transport and preferential groundwater flows at INEEL (Idaho): decay-series disequilibrium studies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1290462