Steady-state gamma-radiolysis of aqueous methyl ethyl ketone (2-butanone) under postulated nuclear reactor accident conditions

The steady-state gamma-radiolysis of aqueous solutions containing 1 x 10(-3 ) mol dm(-3) methyl ethyl ketone (MEK) has been studied at a dose rate of 0 .12 Gy s(-1), 25 degrees C and an initial pH of 10. Experiments were conduc ted in air-, Ar- or N2O-purged aqueous solutions, or in Ar-purged solutions with added tert-butanol. MER, its radiolytic products, and the change in p H resulting from MEK decomposition were analysed as a function of time (or total absorbed dose). The main initial step for the radiolytic decompositio n of MEK is the H abstraction from MEK by (OH)-O-., produced by gamma-radio lysis of water, to form MEK radical. In the absence of O, the main decay pa th of the MEK radical appears to be dimerization to form 3,4-dimethyl-2,5-h exanedione. In the presence of oxygen, the MEK radical reacts primarily wit h O to form the MEK peroxyl radical. This radical ultimately results in a s eries of progressively smaller oxidation products. The formation of organic acids, and eventually CO2, reduces the pH of the solution. This paper pres ents the experimental data and proposes the MEK decay kinetics and mechanis m. Published by Elsevier Science Ltd.