Radiation chemical effects in the near field of a final disposal site - II: Simulation of the radiolytic processes in concentrated NaCl solutions

The radiation chemical reactions in gamma-irradiated 2 to 5.3 mol/l NaCl so lutions were mathematically modeled by elementary reactions proceeding in p arallel. The calculations showed that if all radiolytic gases could escape from the solution, only three final compounds would be formed proportional to the dose and independent from the dose rate: H-2, O-2, and chlorate. All other products and intermediates reached a steady-state concentration afte r similar to 1 kGy. Within certain limits, the yields of final radiolytic p roducts were determined solely by the primary G values of H-2 and H2O2. The results of the corresponding irradiation experiments carried out in glass ampoules up to similar to 1 MGy were in good agreement with the calculation s. The simulation of the radiolysis under the condition that all gaseous pr oducts remain dissolved in the solution showed a nearly constant formation rate for hydrogen and oxygen. As opposed to this, the experiments conducted in autoclaves resulted in nearly steady-state conditions for the gases at some 100 kGy at a pressure of similar to 35 bars. For chlorate, the experim ents and the calculation gave a constant concentration of a few micromoles per litre in 5.3 mol/l NaCl solution. A better correspondence between exper iments and the simulation was achieved for the gases when the reaction mode l was extended for interaction of corrosion products from the autoclaves.