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Title: Flow and transport at the Las Cruces trench site: Experiment IIb

The US Nuclear Regulatory Commission (NRC) has been directed by Congress in the Low Level Waste Policy Act of 1980 to develop regulatory guidance and assist the individual states and compacts in siting and assessing future low level radioactive waste (LLW) disposal facilities. Three water flow and solute transport experiments were performed as part of a comprehensive field trench study near Las Cruces, New Mexico to test deterministic and stochastic models of vadose zone flow and transport. This report presents partial results from the third experiment (experiment IIb). Experiments IIa and b were conducted on the North side of the trench, on a plot 1.22 m wide by 12 m long, perpendicular to the trench. The area was drip irrigated during two time periods with water containing a variety of tracers. The advance of the water front during the two irrigation episodes was measured with tensiometers and neutron probes. Solute front positions were determined from soil solution sampling through suction samplers and from disturbed sampling. The results from experiment IIb show predominantly downward water movement through the layered unsaturated soil, as evidenced from neutron probe data and gravimetric sampling. Tritium plumes were only half as deep and half as widemore » as the water plumes at 310 days after the beginning of experiment IIb. Chromium, applied as Cr(VI), moved a readily as, and similar to tritium, but there was a loss of mass due to reduction of Cr(VI) to Cr(III). Chloride and nitrate, initially present at high concentrations in the soil solution, were displaced by the low concentration irrigation water, resulting in chloride and nitrate concentration distributions that looked like negative images of the tritium distributions. The extensive data presented should serve well as a data base for model testing.« less
Authors:
;  [1] ; ;  [2]
  1. New Mexico State Univ., Las Cruces, NM (United States)
  2. Arizona Univ., Tucson, AZ (United States). Dept. of Soil and Water Science
Publication Date:
OSTI Identifier:
515518
Report Number(s):
NUREG/CR-6437
ON: TI97008405; TRN: 97:016600
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jul 1997
Research Org:
Nuclear Regulatory Commission, Washington, DC (United States). Div. of Regulatory Applications; New Mexico State Univ., Las Cruces, NM (United States); Arizona Univ., Tucson, AZ (United States). Dept. of Soil and Water Science
Sponsoring Org:
Nuclear Regulatory Commission, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
05 NUCLEAR FUELS; RADIOACTIVE WASTE FACILITIES; HYDROLOGY; NEW MEXICO; SITE CHARACTERIZATION; ENVIRONMENTAL TRANSPORT; TRACER TECHNIQUES; IRRIGATION; EXPERIMENTAL DATA; HYDRAULIC CONDUCTIVITY; SOILS