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<p>In the context of a total loss of cooling in fission product storage tanks at spent nuclear fuel reprocessing facilities, the experimental work conducted aims to enhance the understanding of ruthenium transport mechanisms from concentrated nitric acid solutions under accidental conditions, particularly during thermal runaway events. Experiments were carried out using two distinct ruthenium sources (volatile RuO<sub>4</sub> or gaseous Ru coming from nitrosyl ruthenium -&#xa0;HNO<sub>3</sub> solution) to investigate the transport of gaseous ruthenium species through a controlled thermal tube made of either quartz or stainless steel. The SS tube is representative of the venting pipes and the Ru nitrosyl-HNO<sub>3</sub> source simulating HLLW. The influence of several parameters, including carrier gas composition (air, H<sub>2</sub>O), NO<sub>2</sub> feed, tube temperature, geometry and material was systematically examined. Results indicate that the key factors governing ruthenium transport at the tube outlet are the presence of NO<sub>2</sub> or nitric vapors and the tube temperature. The gas phase composition affected Ru transport which is more enhanced with HNO<sub>3</sub> vapors than with NO<sub>2</sub>. With SS tube at 150&#xa0;°C and Ru nitrosyl-HNO<sub>3</sub> source at 140&#xa0;°C, up to 95% was transported at the outlet predominantly in the gaseous form attributed to RuO<sub>4</sub>. At lower temperatures, deposition and condensation phenomena were favored, even in the presence of nitric vapors.</p>

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Experimental study of ruthenium transport from boiling nitric solution of high-level liquid waste with stainless steel tube

  • 期刊论文

  • 发表日期：

    2026年7月16日

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  • Marie-Noelle Ohnet,
  • Charlotte Moulin,
  • Cédric Gomez,
  • Naoki Yoshida

摘要

In the context of a total loss of cooling in fission product storage tanks at spent nuclear fuel reprocessing facilities, the experimental work conducted aims to enhance the understanding of ruthenium transport mechanisms from concentrated nitric acid solutions under accidental conditions, particularly during thermal runaway events. Experiments were carried out using two distinct ruthenium sources (volatile RuO4 or gaseous Ru coming from nitrosyl ruthenium - HNO3 solution) to investigate the transport of gaseous ruthenium species through a controlled thermal tube made of either quartz or stainless steel. The SS tube is representative of the venting pipes and the Ru nitrosyl-HNO3 source simulating HLLW. The influence of several parameters, including carrier gas composition (air, H2O), NO2 feed, tube temperature, geometry and material was systematically examined. Results indicate that the key factors governing ruthenium transport at the tube outlet are the presence of NO2 or nitric vapors and the tube temperature. The gas phase composition affected Ru transport which is more enhanced with HNO3 vapors than with NO2. With SS tube at 150 °C and Ru nitrosyl-HNO3 source at 140 °C, up to 95% was transported at the outlet predominantly in the gaseous form attributed to RuO4. At lower temperatures, deposition and condensation phenomena were favored, even in the presence of nitric vapors.