56. 



The disposal of high-level wastes includes pre-treatment to 

 make them suitable for ground disposal. This maybe considered 

 chemical processing in the sense that fission products having indus- 

 trial and medical use may be of sufficient interest to recover. The 

 critical isotopes are: Sr90, Y 90, Sr 89, Y 91 Cs 137 , Ba 137 , Ce 144 , 

 Pr 144 , Zr 95 , Nb 95 , Ba 140 , La 140 , andPm 147 . If these can be re- 

 moved the problem of heat will largely disappear. Chemical precip- 

 itation and solvent extraction methods for removing some of these 

 isotopes are being developed and the value of one or two isotopes 

 might pay for the removal of the rest of them. 



To increase the effective use of pits, the geologic and hydro- 

 logic conditions that seem to be most favorable for the location of 

 the pits are being studied. In addition, the possibility of developing 

 impervious liners is being explored: this includes mineral liners and 

 asphalt liners, and also possible self-sealing as the result of inter- 

 action between the wastes and the soil. In searching for a suitable 

 liner, we have studied concrete, limestone and asphalt in the contain- 

 ment of acid waste; high temperatures and radiation have a deleterious 

 effect on asphalt, but the concrete seems as though it might hold up 

 long enough once we have developed a method of permanently fixing 

 and fusing the waste. Asphalt has been tested with highly alkaline 

 waste and it has been in the pit for over a year without showing any 

 leakage. Even though an impervious liner is developed, it will be 

 necessary to immobilize the waste in the pit. The ceramists have 

 ideas which may prove helpful in permanently fixing and fusing the ma- 

 terial in the pit after the water has evaporated and the nitrogen oxides 

 have been driven off. 



Even if we have an impervious liner, and the material is per- 

 manently fixed and fused in the pit, it is important for purposes of 

 monitoring to understand the exchange properties of the soil in which 

 you locate the pit. The surface disposal of wastes is as much a prob- 

 lem of geochemistry as it is geology. We are concerned also about 

 the techniques of monitoring in wells and in the soil to determine the 

 underground movement. 



The acid aluminum nitrate wastes have been studied in the past 

 year to devise means of fixing the isotopes permanently. This is 

 acid- deficient waste which might form a gel or slurry when mixed with 

 cheap and readily available materials such as clay silicates, phoshate 

 tailings, and soda ash. The volumes added should be kept as low as 

 possible and should aid in fusion. To avoid creating a hazard from 



