Neutron and β/γ radiolysis of water up to supercritical conditions. 2. SF_6 as a scavenger for hydrated electron

摘要

SF_6 has been used as a specific scavenger to investigate the β/γ radiolysis yield of hydrated electrons in pressurized high temperature sub- and supercritical water. SF_6 is thermally stable in supercritical water, and each scavenging reaction is known to produce six fluoride ions, which can be readily measured using a fluoride-selective electrode. Problems in the application of this method are described, including buildup of acid product and chain reduction of SF_6 in the presence of organic ~·H and ~·OH radical scavengers. Ultimately we find that the combination of SF_6 and phenol in neutral solution gives reliable results in supercritical water, because the protons and fluoride ions remain associated as HF molecules. The β/γ yields in supercritical water are similar to previous measurements using N_2O scavenger.