This paper will describe operations and procedures used, and give 

 a preliminary analysis of the results of the experiments. 



Section II. ISOTOPES, TAGGING TECHNIQUES, AND INSTRUMENTS 



1. Isotopes and Tagging Techniques 



Two isotopes were used in this series of tests - xenon- 133 with 

 a half-life of 5 days and a mix of gold 198-199 with a half-life of 

 about 3 days . 



Radioactive xenon is injected into the quartz grain in a process 

 like that of kryptonation described by Chleck, et al., (1963). In 

 essence, the process involves heating carbonate- free quartz sand to 

 approximately 900 degrees centigrade in an atmosphere of xenon- 133, then 

 cooling rapidly with liquid nitrogen. Labeling is a function of the mass 

 of the particle and does not affect the hydraulic characteristics of the 

 grain. Xenonation has been described in detail by Acree, et al., (1969). 



Isotopes of gold were used in numerous sediment tracing programs 

 (Krone, 1960; Cummins, 1964; Ingram, et al., 1965; and Hart, 1969). 

 However, the tagging procedures have not been explained in detail. As 

 part of one of the RIST objectives - the search for isotopes and tagging 

 techniques suitable for sand tracing - the Oak Ridge National Laboratory 

 (ORNL) initiated a study of existing gold-tagging techniques, and 

 explored possible improvements. As a result of this research, a new 

 tagging technique was developed (Stephens, et al., 1968) and utilized 

 in RIST programs. The new technique involves pretreating carbonate- 

 free quartz sand with a solution of p_-isopropylbenzaldehyde-ethanol. 

 After washing and drying, the sand is treated with a solution of gold 

 chloride containing the gold isotopes 198 and 199. After decanting ex- 

 cess solution, the sand is cured by heating to 1,000 degrees centigrade. 

 Leaching and' abrasion tests show insignificant loss and an inclusive 

 process efficiency of 90 percent. 



Because this' new ORNL technique labels the surface, two drawbacks 

 were possible. One was inhomogeneous tagging on a mass basis because 

 of the wide range of surface areas present in natural sands consisting 

 of a range of particle sizes. A second was the possible effect on 

 hydraulic characteristics of the grains. Stephens, et al., (1969) 

 found that mass labeling could be approximated by fractionating the 

 sand prior to tagging, and then labeling each fraction with the requi- 

 site proportion of total sample activity of gold 198-199. While their 

 data indicate some differences in activity (counts per milligram) 

 among the size classes, counts reported from all size classes have 

 no significant statistical difference. 



