Transport and Containment Chemistry of Ruthenium under Severe Accident Conditions in a Nuclear Power Plant.

During a severe nuclear accident volatile elements and elements readily forming volatile compounds are the main concern regarding the release of radioactive material to the environment. As ruthenium is prone to form volatile oxides under severe nuclear accident conditions as well as having radiotoxic isotopes, it is one of the more important elements during such an accident.In this work the chemical behavior of ruthenium during the transport in the reactor cooling system and the chemistry of ruthenium within the containment was studied.Studies on ruthenium transport included the effect of temperature, air-radiolysis products and aerosols on the quantity and chemical form of transported ruthenium during an accident. During the experiments the temperature had significant effect both release and transport of ruthenium. Different air radiolysis products affected both quantity and physical form of the transported ruthenium.The other part of the studies was focused on the chemistry of ruthenium within the containment. These experiments aimed at the interaction of ruthenium tetroxide with metallic (Al, Cu, Zn) and epoxy paint covered surfaces within the containment. Ruthenium had great affinity towards these surfaces that led to the formation of ruthenium rich deposits and thus a clear retention. Chemical characterization as well as quantification of these deposits was obtained.The effect of gamma radiation on the formed ruthenium deposits was shown and re-volatilized fractions of ruthenium under different atmospheres and received doses were determined decreasing the retention significantly.\ua0Studies focused on interaction of ruthenium tetroxide with iodine-covered surfaces showed its ability to oxidize iodine deposit and re-volatilize iodine from the aluminum and zinc metals. Iodine covered surfaces were also proved to be an effective trap of ruthenium within the containment.Data obtained from these studies can be utilized for the better understanding of severe accident phenomenology and behavior of radionuclides during an accident

Solubility Thermodynamics of CyMe-BTBP in Various Diluents Mixed with TBP

The two organic ligands 6,6\u27-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[1,2,4]triazin-3-yl)[2,2\u27]bipyridine (CyMe-BTBP) and tri-butyl phosphate (TBP) have previously been investigated in different diluents for use within recycling of used nuclear fuel through solvent extraction. The thermodynamic parameters, , , and , of the CyMe-BTBP solubility in three diluents (cyclohexanone, octanol and phenyl trifluoromethyl sulfone) mixed with TBP have been studied at 288, 298 and 308 K, both as pristine solutions and pre-equilibrated with 4 molL nitric acid. In addition, the amount of acid in the organic phase and density change after pre-equilibration have been measured. The solubility of CyMe-BTBP increases with an increased temperature in all systems, especially after acid pre-equilibration. This increased CyMe-BTBP solubility after pre-equilibration could be explained by acid dissolution into the solvent. Comparing the and calculated using with the same parameters derived from a linear fit indicates temperature independence of all three thermodynamic systems. The change in enthalpy is positive in all solutions

RuO4 interaction with surfaces in the containment of nuclear power plant

During a severe accident different fission products will be released from the nuclear fuel and some of them may eventually reach the containment building. Ruthenium is considered to be an important fission product due to the possible formation of volatile oxides. Radiotoxicity and chemical toxicity of the volatile ruthenium compounds present a considerable hazard during the severe nuclear accident.In this work experiments regarding behavior of ruthenium tetroxide in the reactor containment were performed. Interaction of ruthenium tetroxide with zinc, copper, aluminium and epoxy paint in dry and humid atmosphere was examined. Several spectroscopic techniques were used to identify the chemical composition of the deposits formed after the interaction of RuO4 with different materials. Examination of the possible re-oxidation of ruthenium deposits to the volatile form by gamma radiation was also studied.Interaction of RuO4 with zinc, copper and aluminium had lead to different amounts of the deposited ruthenium among the metals. Most extensive deposition of RuO4 was observed on the aluminium metal. In dry atmosphere conditions preference of aluminium metal was very obvious. Deposits of ruthenium were identified to be a ruthenium dioxide on all metals. Speciation of the deposits formed on epoxy paint showed at least two different ruthenium species. One of them was identified to be probably a ruthenium dioxide, composition of the other one was not fully revealed.Experiments with the radiolytical re-vaporization of the ruthenium deposits from the epoxy paint indicated the release of ruthenium from the samples under the humid atmosphere. In the dry atmosphere re-vaporization of ruthenium wasn’t observed.The results showed how is ruthenium distributed between different materials in the containment. The chemical composition of the deposits was identified with use of different spectroscopic techniques. Dependence of re- vaporized ruthenium fraction on the received dose in the humid atmosphere was estimated

RuO4 interaction with surfaces in the containment of nuclear power plant

During a severe accident different fission products will be released from the nuclear fuel and some of them may eventually reach the containment building. Ruthenium is considered to be an important fission product due to the possible formation of volatile oxides. Radiotoxicity and chemical toxicity of the volatile ruthenium compounds present a considerable hazard during the severe nuclear accident.In this work experiments regarding behavior of ruthenium tetroxide in the reactor containment were performed. Interaction of ruthenium tetroxide with zinc, copper, aluminium and epoxy paint in dry and humid atmosphere was examined. Several spectroscopic techniques were used to identify the chemical composition of the deposits formed after the interaction of RuO4 with different materials. Examination of the possible re-oxidation of ruthenium deposits to the volatile form by gamma radiation was also studied.Interaction of RuO4 with zinc, copper and aluminium had lead to different amounts of the deposited ruthenium among the metals. Most extensive deposition of RuO4 was observed on the aluminium metal. In dry atmosphere conditions preference of aluminium metal was very obvious. Deposits of ruthenium were identified to be a ruthenium dioxide on all metals. Speciation of the deposits formed on epoxy paint showed at least two different ruthenium species. One of them was identified to be probably a ruthenium dioxide, composition of the other one was not fully revealed.Experiments with the radiolytical re-vaporization of the ruthenium deposits from the epoxy paint indicated the release of ruthenium from the samples under the humid atmosphere. In the dry atmosphere re-vaporization of ruthenium wasn’t observed.The results showed how is ruthenium distributed between different materials in the containment. The chemical composition of the deposits was identified with use of different spectroscopic techniques. Dependence of re- vaporized ruthenium fraction on the received dose in the humid atmosphere was estimated