These differences are well within the limits of experimental error. 

 Figure 3 shows several curves of settling-tube data and data obtained 

 by standard seiving techniques. 



Xenonation differs from kryptonation in that the former occurs at 

 low pressure. High temperature of the process causes vaporizing of any 

 carbonate contained in the sand, and thus adversely affects the labeling 

 process. Consequently, the carbonate fraction must be removed by acid 

 leaching before labeling. Therefore, xenonation is not a suitable tech- 

 nique where the dominant mineral constituent of sand is a carbonate. 

 Carbonate-free sand is heated to approximately 900° C in a specially 

 designed furnace containing an atmosphere of xenon-133. After cooling 

 with liquid Nitrogen (No), the sand is removed and packaged for shipment 

 to the test site. Due to desorption of xenon from sand, initial batches 

 of labeled sand had an effective half life of 2.7 days. However, recent 

 improvements in the technique show that the effective halflife of xenon- 

 ated sand is now 5 days, nearly identical to that of the gas itself. 

 Labeling of sand with this technique is a function of the mass of the 

 particle rather than the surface area. 



Labeling is presently limited to a batch of about HO liters (approxi- 

 mately 100 pounds) per day. Details of the process are presented in the 

 ORNL report in Appendix C. Though the process occurs at high temperature, 

 it does not affect the shape of grains (Figure h) , but has changed the 

 color of the sand to ash-gray. 



Other labeling techniques provide greater choice of isotopes, use 

 of which may ultimately be required to meet RIST program goals. Arti- 

 ficially manufactured sand has been used as a tracer (Sato, 1962; Taney, 

 1962; Ingram, et al, 1965). However, such a process requires placing an 

 element suitable for activation in a silica melt, maintaining specific 

 gravity near that of quartz, crushing the solid mass, resizing it to 

 match size distributional characteristics of sand in the test environ- 

 ment, and then shipping it to a reactor for activation. In special cases, 

 where the mineralogy is suitable, it is possible to activate a naturally 

 occurring impurity in quartz thereby permitting the use of sand indige- 

 nous to the test site (inman and Chamberlain, 1959)- Another possible 

 technique is to place desired activity on the external surface of the 

 grains and then seal it by the addition of an inert, abrasive-resistant 

 coating. 



Because these techniques may modify the specific gravity, size, 

 shape, and roughness of discrete particles, it is possible that the 

 hydraulic characteristics of the grains would be changed leaving results 

 of an experiment in some doubt. The U. S.. Naval Radiological Defense 

 Laboratory (NRDL), San Francisco, has developed a means of coating sand 

 grains by a water-glass procedure. Under contract to this RIST study, 

 personnel at NRDL conducted experiments on the leaching and abrasion of 

 beach sands tagged with barium-1^0 , lanthanum-lUO , and chromium-51 by 

 the NRDL water-glass procedure. These particular isotopes, with varying 



