ATR-2 Part A: Ruthenium chemistry and transport in a RCS due to air radiolysis products
Ivan Kajan, Teemu Kärkelä, Ari Auvinen, Christian Ekberg,
In the NKS-R ATR-2 activity (year 2015) by VTT Technical Research Centre of Finland Ltd and Chalmers University of Technology, Sweden the aim was to study the effect of the air radiolysis products N2O, NO2, HNO3 (see Part A) and CsI aerosol (see Part B) on the transport of gaseous and particulate ruthenium species through a model primary circuit. The outcomes of the air radiolysis products impact on Ru behaviour are summarized in this report (Part A).
All the experiments were conducted with VTT´s Ru transport facility. The RuO2 precursor was heated inside a furnace up to 1300 K, 1500 K and 1700 K under slightly humid air atmosphere and the formation of gaseous ruthenium oxides took place. The air radiolysis products N2O, NO2 and HNO3 were fed into the flow of ruthenium oxides. In the experiments nitrogen oxides as well as nitric acid originating from air radiolysis, which is an inevitable phenomenon during a severe nuclear accident, had a significant effect on the ruthenium chemistry in the model primary circuit. The fraction of transported gaseous ruthenium was increased when NO2 or HNO3 was injected into the air-flow with volatile ruthenium oxides. This effect was most prominent in case of NO2 precursor at temperature of 1300 K. The overall transport of ruthenium was strongly increased at 1500 K when N2O was injected into the gas phase, when compared to the pure humid air atmosphere.
The obtained results indicate a strong effect of air radiolysis products on the quantity of transported ruthenium and its partition to gaseous and aerosol compounds.
Ruthenium, Radiolysis, Nitrogen oxides, Severe Accident, Source Term