Chapter 1 



PHYSICAL AND CHEMICAL PROPERTIES OF WASTES PRODUCED BY 



ATOMIC POWER INDUSTRY 



Charles E. Renn, The Johns Hopkins University 

 Department of Sanitary Engineering and Water Resources 



The ultimate forms and radioactivities of 

 wastes delivered for sea disposal will be deter- 

 mined by conditions that have not yet been 

 fully evaluated. Present and projected wastes 

 will undoubtedly be modified by requirements 

 for storage, transport, and economical handling, 

 and the ultimate form of wastes with which we 

 may be concerned will be further conditioned 

 by what we learn in early disposal practice. The 

 following represents the characteristics of high- 

 level reactor wastes that now exist, and which 

 are likely to appear soon. 



The primary radioactive wastes result from 

 the chemical extraction of inhibitory fission 

 products from metallic reactor elements. A 

 strong nitric acid solution of aluminum heavily 

 contaminated with a variety of fission products 

 is obtained after the useful reactor fuel is re- 

 covered. To conserve tank space and shielding, 

 the solutions are concentrated by evaporation. 

 Where storage is to be made in steel containers, 

 the solution may be neutralized and made 

 slightly alkaline with commercial caustic. A 

 neutral or alkaline salt solution or slurry is 

 developed — the concentration of salts may ap- 

 proach or exceed saturation values at storage 

 temperature. The neutral salt concentration of 

 the waste determines its density. Some types 

 of reactor elements are not directly soluble in 

 nitric acid and require solution in combinations 

 of other mineral acids and catalysts; most ulti- 

 mately require conversion to nitrates before 

 complete extraction, however. 



The cladding and alloying metals of the reac- 

 tor elements are also discarded in the wastes. 



Aluminum is the most common and abundant 

 of the metals used ; it appears in concentrations 

 as high as 80,000 ppm. in final wastes. Zir- 

 conium will also be present. 



Of the various non-radioactive components in 

 the wastes, the properties of the high-density- 

 producing salts, of the high nitrate concentra- 

 tions, and of aluminum are of greatest interest. 

 The presence of these at present limit the prac- 

 tical production of selectively adsorbed fission 

 waste products. If the wastes are concentrated 

 for economical storage and transportation and 

 neutralized to limit corrosion, the densities of 

 the waste liquids will exceed that of sea water. 



The temperatures for precipitation of super- 

 saturated salts in the various wastes are not 

 known, but it may be assumed that further 

 sludges will be formed on cooling to deep sea 

 temperatures — some corrosion-product sludges 

 already exist. 



The solubilities of both normal and radio- 

 active components of the waste will be condi- 

 tioned by the presence of nitrates in concentra- 

 tions exceeding equivalence. Aluminum nitrate 

 precipitates as a light floe in sea water at con- 

 centrations as low as 1 ppm. Al. At present 

 there are no data on its solubility in a sea water 

 waste mixture. Neither do we know what the 

 adsorption characteristics of the aluminum floe 

 in sea water may be. 



The range of physical and radiochemical 

 characteristics that may be anticipated in con- 

 centrated fuel re-processing wastes and approx- 

 imate quantities of wastes produced are indi- 

 cated in the three tables following. 



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