as definitive studies in sand-size distributions • They were made simply 

 to provide an order-of -magnitude estimate of the effects of coating, 

 firing, and abrasion on the size of the particles. Small, unavoidable 

 weight losses of the sand sample occurred as the tagging, sieving, and 

 abrasion routine developed. Sources of these weight losses were the 

 inability to transfer quantitatively the coated sand from the sodium 

 silicate mixing bottle to the porcelain casserole, losses due to the 

 high temperature firing of the sand (carbonate decomposition), changes 

 in the sorbed moisture on the sand, and losses in removing the smaller 

 sand fraction from sieves and weighing containers because of the electro- 

 static charge developed on the particles during the sieving. Since most 

 of the material losses were cumulative, the sieving routine was varied 

 from experiment to experiment so that the number of sieving operations 

 in any one experiment (and therefore also the total weight-loss error) 

 was minimized. The total loss caused by the sources listed above 

 varied from 2.5 to k.5 grams per 100 grams sand. 



The pre-tagging sieving results for Monterey sand and the various 

 Point Conception sands are given in Table A- I. Several Point Conception 

 samples consisted chiefly of coarse gravel and pebbles up to 1 1/2 

 inches in diameter. Because the coarse material would tend to bias 

 results when 100— gram sand samples were used in the experiments, only 

 material that passed through an 833-micr'on sieve was retained for the 

 experiments. Another objection to the retention of the coarse material 

 was the excessive grinding action that would be produced in the limited 

 confines of the 500-milliliter abrasion vessel. Such results would be 

 similar to those obtained with grinding pebbles in a ball mill, and 

 would be much more severe than those likely to be experienced under test 

 conditions. The arbitrary imposition of an upper limit to the particle 

 size does not in any way invalidate the results obtained, because the 

 objective of the investigation was the integrity of the silicate coating 

 under reasonable experimental conditions and not the particle size 

 distribution of the sand, Furthermore, on a weight basis, the smaller 

 fractions are the more important because the specific activity of a 

 particle increases inversely as its size. Also the smaller fractions 

 will be the most important ones in the field since they will travel 

 the farthest from the deposition site in a given time. 



The new size distribution data obtained after the removal of the 

 coarse material are shown in Table A-II. 



RESULTS 



Study No. 1 - Monterey Sand - A pilot study was made with Monterey 

 sand. This study was made for scaling down the established procedure 

 for concrete-mixer size batches of tagged sand to 100-gram laboratory 

 size batches. The study was made also for providing a standard tagged 

 sand for comparison with the Point Conception sands to be studied later. 

 The Monterey sand was tagged with Ba-La-lUO radioactivity. The leaching 

 and abrasion experiments extended over 12 days, approximately one half- 

 life of the activity. After 12 days about 1 percent of the activity hed 



A-5 



