PARIS project: Radiolytic oxidation of molecular iodine in containment during a nuclear reactor severe accident: Part 1. Formation and destruction of air radiolysis products—Experimental results and modelling

摘要: Abstract In case of a hypothetical severe accident in nuclear LWR (light water reactor), the high radiation fields reached reactor containment building due to release fission products from core could induce air radiolysis. The radiolysis could, turn, oxidise gaseous molecular iodine into aerosol–borne iodine–oxygen–nitrogen compounds. Thereby, this reaction involves change speciation and decrease volatility atmosphere. Kinetic data were produced within PARIS project on formation destruction, their with iodine, objective developing validating existing kinetic models. current paper includes non-iodine tests whose was determine rates destruction presence both structural surfaces (decontamination coating (“paint”) stainless steel), aerosol particles such as silver rich (issued control rods) boundary conditions representative for or PHEBUS facility containments. It is found that concentration increases dose tend approach saturation levels at doses higher than about 1 kGy. This behaviour more evident oxygen/steam atmospheres, producing ozone, air/30% (v/v) steam latter favouring model-predicted on-going production nitrogen dioxide even very doses. No significant effect temperature, rate hydrogen addition (4%, v/v) observed. Furthermore, inserted do not exhibit effects concentrations. However, these “non-noticeable influence” be masking small by appreciable scattering experimental product results are then analysed using two different models, an empirical mechanistic one. constants model including products, derived results, reasonable agreement those determined previously lower fractions. From IODAIR-IRSN, it concluded ozone predominant low air/steam atmospheres. At 1 kGy, becomes increasingly important, increase its simultaneous concentration.