Behaviour of Ruthenium in high temperature oxidising conditions Ulrika Backman & Ari Auvinen & Jorma Jokiniemi & Maija Lipponen& Riitta Zilliacus SAFIR interim seminar

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 2 VTT PROCESSES Objective Quantify the effect of – Oxygen partial pressure – Oxidation temperature – Tube material on ruthenium release, transport and speciation

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 3 VTT PROCESSES Experimental facility

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 4 VTT PROCESSES Methods t Solid RuO 2 particles were collected on plane filters. t Gaseous RuO 4 was trapped in 1M NaOH-water solution. t Filters and precipitates were analysed with INAA (detection limit 2  g/sample). t NaOH solution was analysed using ICP-MS (detection limit 0.05  g/l). t Deposition profile was measured using radiotracer technique (Ru 103 -isotope) t RuO 2 particle morphology was determined with TEM. t RuO 2 particle crystallinity determined with SAD. t RuO 2 deposit morphology was studied with SEM.

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 5 VTT PROCESSES Experimental matrix

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 6 VTT PROCESSES

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 7 VTT PROCESSES RuO 2 - deposition profile and gas temperature

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 8 VTT PROCESSES SEM images of ceramic tube wall

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 9 VTT PROCESSES TEM image and SAD pattern of RuO 2 particle {101} {110}

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 10 VTT PROCESSES Conclusions (1/2) t Ruthenium release – Released mainly as RuO 3, 5% released as RuO 4. – Approximately constant 9-11 mg/min in air flow at 1500 K. – Release rate decreases as O 2 partial pressure decreases. – Release rate increases with oxidation temperature. t Ruthenium deposition – Very significant (65-88%). – Deposition by RuO 3 to RuO 2 reaction at 800°C. – Deposition by thermophoresis at furnace outlet. – Deposition by decomposition of RuO4 on steel at °C. – Deposition decreased by increased furnace temperature (faster quench), by seed particles and by decreased O 2 and RuO 3 partial pressures.

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 11 VTT PROCESSES t Transport of gaseous ruthenium – In dry experiments with stainless steel tube: % – Fraction was independent of release temperature, oxygen partial pressure and concentration of ruthenium – Probably due to the catalytic effect of the stainless steel tube surface on the decomposition of RuO 4 to RuO 2 – Using alumina tube: 5% – Comparable to the fraction given by thermodynamic equilibrium – RuO 2 seems not have a strong catalysing effect on the decomposition of RuO 4. – When atmosphere contained some water: 5 % – Most likely the water vapour passivated the stainless steel tube surface Conclusions (2/2)

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 12 VTT PROCESSES Further experiments t The effect of water vapour on Ru release and speciation – With and wo. seed particles. – Variable steam partial pressure. t The effect of seed particles on Ru transport – In dry conditions. – Variable particle number concentration. t Time dependence of Ru release rate and speciation – Online experiments with radioactive ruthenium. t Catalytic decomposition of RuO 4 by RuO 2 – Experiments with and wo. filters doped with RuO 2.

VTT TECHNICAL RESEARCH CENTRE OF FINLAND 13 VTT PROCESSES