Abstract
To facilitate the treatment of spent decontamination and chemical cleaning solutions, this study explored the feasibility of replacing stable complexing agents (such as EDTA) by complexing agents which can be readily decomposed using chemical or thermal treatment. Acetohydroxamic acid was found to be a promising candidate for such a role. Preliminary experiments carried out on actual corrosion products from steam generators indicated that 15% acetohydroxamic acid solutions had similar effectiveness to that of the EPRI/SGOG iron solvent (which contains 15% EDTA) with respect to certain magnetite-rich deposits. The addition of malonic acid and hydrazine enhanced the dissolution of magnetite in acetohydroxamic acid solution. EDTA and acetohydroxamic acid were similarly effective in the decontamination of stainless steel surfaces superficially contaminated with 60Co. It was found that acetohydroxamic acid in spent solvents can be completely decomposed through acid-catalyzed hydrolysis using nitric or hydrochloric acid. Complete decomposition can also be achieved through oxidation of acetohydroxamic acid with active manganese dioxide or potassium permanganate. Regeneration of spent, contaminated acetohydroxamic acid solutions was demonstrated using a cation exchange resin to remove ferric or ferrous ions from the solution. Cobalt ions were removed from such solutions using charcoal. Based on the experimental findings, acetohydroxamic acid solutions appear to be promising candidates for use in decontamination or chemical cleaning, followed by decomposition or regeneration of the spent solutions.
