Radiation-chemical effects in the near-field of a final disposal site: role of bromine on the radiolytic processes in NaCl-solutions

The oxidation of Br- by Cl-2(-) is investigated by gamma pulse radiolysis in aqueous solutions of NaCl and NaBr. Depending on the ratio of the concentration of Br- to Cl-, the main product being observed is either Cl-2(-), or Br-2(-). The mixed radical anion ClBr- exhibits a broad absorption band at 350 nm with epsilon(350) = 9300 dm(3) mol(-1) cm(-1). The rate constants of the equilibrium Cl-2(-) + Br- double left right arrow ClBr- + Cl- are determined to be k(f) = 4 x 10(9) dm(3) mol(-1) s(-1) and k(b) 1.1 x 10(2) dm(3) mol(-1) s(-1). The formation of the Cl-3(-) (lambda(max) = 220 nm), Cl2Br- (lambda(max) = 230 nm) and ClBr2- (lambda(max) = 245 nm) ions in the radiation-chemical oxidation of Cl- and Br- ions in an aqueous solution was observed by pulse radiolysis, and its mechanisms of appearance and the equilibrium constants were determined.