The following text was automatically extracted from the image on this page using optical character recognition software:
RESEARCH OBJECTIVES
DESCRIPTION OF AND NECESSITY FOR THE RESEARCH
This project developed low-level analytical methods for the measurement of radionuclides
by accelerator mass spectrometry. The contaminant radionuclides potentially measurable by
AMS include: 14C, 36C1, 59Ni, 63Ni, 90Sr, 93Zr, 99Tc, 1291, 239Np, 239Pu, and other actinides. We chose to
concentrate on 36C1, 99Tc, 90Sr, and 129I. These nuclides were globally distributed as fallout during
the era of atmospheric nuclear testing, and occur today in almost every environment. They also
are prominent contaminant nuclides at a variety of DOE sites. There is a need to develop these
low-level methods to observe the migration of radionuclides in natural environments. There are
at least three advantages of this: 1) the ability to conduct migration studies in locations most like
those of concern to public health, e.g., a "far-field" environment; 2) migration research does not
have to be conducted at sites of multiple contamination, e.g., by VOC's, which can produce
hard-to-interpret results; and 3) it becomes unnecessary to collect research samples that are
themselves radioactive waste and are therefore difficult to handle and dispose of in the
laboratory. Our approach of examining globally distributed, fallout radionuclides provides
another advantage: 4) since the nuclides are globally distributed, migration research can be
conducted in any chosen environment. Arid environments can be examined for purposes of
nuclear waste storage; riverine systems can be examined for the effects of long-range transport;
forested or agricultural regions can be examined for the effects of vegetative mediation; even
accessible arctic regions could be examined to better understand the fate of radionuclides in
remote northern Russia. The innovative aspect of this research project was that it developed
methods by which field studies of radionuclide migration could take place virtually anywhere,
making the research easier to conduct, less expensive, and better controlled scientifically.
Science is still in the process of trying to characterize the mechanisms by which
radionuclides migrate in natural environments. It is only by understanding these mechanisms that
improved methods for predicting contaminant radionuclide migration can occur. Improved
predictions will reduce costs of remediation by indicating where remediative actions will be the
most effective, by ensuring that the full extent of remediation required has been accurately
determined, by eliminating the need for over-engineered solutions to the problem, and in some
cases by demonstrating that natural attenuation near the release will decrease contaminant
concentrations below regulatory maximum permissible concentrations (thus eliminating the need
for any direct remediative action). Therefore, the development of AMS analytical techniques,
which provide strong advantages for scientific characterization of radionuclide migration in all
natural environments, thereby providing the means for improved predictive capabilities, will
ultimately reduce remediative costs significantly.
ONGOING RESEARCH BY OTHERS
Use of Chloride and 36C1 in Soil Moisture Movement Studies
Physical methods for assessing moisture flux in arid soils are inadequate. Chemical and
isotopic tracers, such as chlorine and 36C1, that move conservatively with the moisture and
therefore define flux by their distribution over time are preferred. Allison et al. (1994), in a
review of available techniques for measuring moisture flux in the unsaturated zone, have pointed
out that "[w]hen recharge rates are only a few millimeters per year or less, chemical and isotopic
methods are likely to be more successful than physical methods, such as water balance methods,
2
