By D.E. Prudic and R.G. Striegl
ABSTRACT
Tritium activities in water vapor and radioactive carbon
(14C)
activities in carbon dioxide were determined in gas samples
pumped from small-diameter air ports installed in a test hole
within the unsaturated sediments next to a commercial burial site
for low-level radioactive waste south of Beatty, Nevada. In April
1994, gas samples were collected from test hole UZB-2, which was
drilled about 350 feet south of the southwest corner of the fence
enclosing the burial site. The test hole is part of a study to
determine the depth to which atmospheric air circulates through
the unsaturated sediments at the desert site. Laboratory results
completed in May 1995 show activities of tritium and 14C were
greater than expected, with measured tritium in the water vapor as
high as 762 tritium units at a depth of 79 feet and measured 14C
in carbon dioxide as high as 1,700 percent modern carbon at a
depth of 18 feet.
In July 1995, the uppermost five air ports in test hole UZB-2 were
resampled. In addition, water vapor was collected for tritium
analyses at a distant test hole, and water vapor for tritium
analyses and carbon dioxide for 14C analyses were collected from
three depths at the research shaft about 200 feet north of test
hole UZB-2, and at two shallow probes (depth of 5.5 feet) next to
the fence enclosing the burial site. Analyses of samples
collected in the upper 112 feet from test hole UZB-2 in July 1995
show the same distribution of tritium and 14C as analyses of
samples collected in April 1994, except that activities were
somewhat greater in July. The greatest activities of tritium and
14C were measured from a shallow probe next to the fence with
activities of 29,400 tritium units and 517,000 percent modern
carbon, respectively.
This abstract was published in U.S. Geological Survey Open-File Report 95-741.