ESTIMATION OF ACOUSTIC AGGLOMERATION OF AEROSOLS PROCESS FOR SOURCE TERM MITIGATION IN NUCLEAR ACCIDENTS Manuel Aleixandre 1 , Enrique Riera 1 , Rosario Delgado-Tardaguila 2 , Luís E. Herranz 2 and Juan A. Gallego-Juárez 1 1 Department of Sensors and Ultrasonic Systems, ITEFI, CSIC (Madrid, Spain) Unit of Nuclear Safety Research, CIEMAT (Madrid, Spain) UIA46 Symposium, 24-26 April 2017, Dresden, Germany
Outline • Motivations • Objectives • Experimental Program and Results • Development of Numerical Model • Comparison of Experimental and Numerical Results • Scaling up – Simulations Results • Synthesis 2 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
MOTIVATIONS (1) Filtered Containment Venting Systems (FCVS) • After the TEPCO Fukushima accident of March 2011 one of the main concerns of nuclear industry has been the search for improved atmospheric source term mitigation • Several countries in Europe and China had already implemented Filtered Containment Venting Systems (FCVS) before and after the Fukushima accident 3 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
MOTIVATIONS (2) • New national R&D programmes and new coordinated international activities on Filtered Containment Venting Systems (FCVS) were promoted • Call for offers launched by European Commission in 2012 • PASSAM: “Passive and Active Systems on Severe Accident source term Mitigation” PASSAM OBJECTIVES The PASSAM project is of R&D experimental nature mainly on FCVS, aiming at: • Exploring potential enhancement of existing source term mitigation devices, and • Demonstrating the ability of innovative systems to achieve larger source term attenuation such as Acoustic Agglomeration of Aerosols (AAA) • To produce simple models and/or correlations based on the understanding of the physical phenomena involved • To generate a valuable database which may be strategic for helping the utilities and regulators in assessing the performance of the existing source term mitigation systems 4 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
AAA OBJECTIVES Investigate the performance of an acoustic agglomerator system at lab-scale under anticipated conditions Specific Objectives: • To develop an Mitigative System Acoustic Agglomerator (MSAA) and integrate it in the PECA facility • To measure and characterize the aerosol growth inside the MSAA • To find out the best operational conditions of the MSAA to work with the aerosols to be generated during the experiments. • To measure aerosol lifetime with and without fostering acoustic agglomeration • To estimate the practical requirements of a MSAA system in a real scenario Facilities: • PECA (Platform for Experimental Characterization of Aerosols) 5 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
EXPERIMENTAL PROGRAM EXPERIMENTAL SET-UP Platform for experimental Characterization of Aerosols (PECA) Gas supply system; Aerosol generator; Injection line; PECA vessel; Exhaust line Instrumentation and sampling Instrumentation and control of the thermal-hydraulic variables Real time devices (APS, ELPI) Gravitational devices (mass cascade impactors and membrane filters) Sampling Mitigation System by Acoustic Agglomeration (MSAA) A parallepipedic chamber; 2 Power ultrasonic transducers (21kHz, 155dB, 300W/unit) MEASUREMENTS During the experiments the effect in the aerosol concentration and its distribution was characterized by several magnitudes: Reduction of the aerosol mass concentration Reduction of the aerosol number concentration Increase of aerosol particle size 6 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
EXPERIMENTAL PROGRAM Selected Boundary Conditions for the Aerosol Particles 1 . Reproduction as close as possible of the real conditions of the aerosols a. Particle size between 0.3 μm and 2.5 μm b. SiO 2 and TiO 2 aerosols c. Concentrations on the range of 25-200 mg/m 3 d. Ambient conditions (temperature, humidity...) 2. Reproducible and known conditions of aerosol that facilitate future modeling a. High monodisperse and well characterized particles b. Mixture of monodisperse well characterized particles c. Controlled and characterized input mass concentrations d. Controlled and characterized treatment time in the ultrasound field 7 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
EXPERIMENTAL PROGRAM 8 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
EXPERIMENTAL MATRIX Total number of tests 20 9 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
EXPERIMENTAL MATRIX Each test consisted of two phases and were conducted 2 times Flush sub-phase: aerosol generator OFF, ultrasound OFF, gas flow =200 kg/h 10 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
EXPERIMENTAL RESULTS Ultrasound Effects: Particle Number Concentration 11 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
EXPERIMENTAL RESULTS Ultrasound Effects: Particle Number/Mass Concentration F1 F1 Particle Number Concentration Particle Mass Concentration F1´ F1´ F2 F2’ F2’ F2 75% mass of 0.3 μ m SiO 2 particles 25% mass of 1 μ m SiO 2 particles Flow 12.5 kg/h 12 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
METHODOLOGY DEVELOPED FOR THE EVALUATION OF THE AAA TESTS Mass/Number Reduction Coefficient (RC M /RC Np ) 𝑁 𝑐 = 𝑁 𝑂𝑞 𝑐 = 𝑂𝑞 𝐵𝑄𝑇 𝐵𝑄𝑇 𝑁 𝐹𝑀𝑄𝐽 𝑂𝑞 𝐹𝑀𝑄𝐽 𝑛𝑓𝑏𝑜 (𝑁 𝑐 𝑥𝑗𝑢ℎ 𝑉𝑇 ) 𝑛𝑓𝑏𝑜 (𝑂𝑞 𝑐 𝑥𝑗𝑢ℎ 𝑉𝑇 ) 𝑆𝐷 𝑛 = 1 − 𝑛𝑓𝑏𝑜 (𝑁 𝑐 𝑥𝑗𝑢ℎ𝑝𝑣𝑢 𝑉𝑇 ) ∙ 100% 𝑆𝐷 𝑂𝑞 = 1 − 𝑛𝑓𝑏𝑜 (𝑂𝑞 𝑐 𝑥𝑗𝑢ℎ𝑝𝑣𝑢 𝑉𝑇 ) ∙ 100% Agglomeration Growth Factor (AGF) 𝑛𝐵𝑄 𝑛𝐺𝑄 (𝑛𝐵𝑄+𝑛𝐺𝑄) 𝐵𝑁𝑁𝐸 𝐵𝑄 + (𝑛𝐵𝑄+𝑛𝐺𝑄) 𝐵𝑁𝑁𝐸 𝐺𝑄 𝐵𝐻𝐺 = 𝐵𝑁𝑁𝐸 𝑆𝑄 AMMD = Aerodynamic Median Mass Dimeter m is the mass in the phase AP (Acoustic Phase), FP (Flush Phase), RP (Reference Phase) 13 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
PARTICLE SIZE DISTRIBUTION STUDY To study the ultrasonic effects on the different particles sizes sums of lognormal distributions were adjusted by least squares to the measured distributions Fitted distributions for the AAA4 tests F2 F1 F1´ F2´ Extracted parameters : AMMD (Aerodynamic Median Mass Diameter) and GSD (Geometric Standard Deviation) of the adjusted distributions. Increases of about 37% and 17% were obtained respectively 14 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
NUMBER REDUCTION COEFFICIENT (RC) AGGLOMERATION GROWTH FACTOR (AGF) 15 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
DEVELOPMENT OF AAA MODEL Assumptions and Basic Equation a) Orthokinetic b) Orthokinetic with Scattering c) Mutual Radiation Pressure d) All kernels added 16 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
DEVELOPMENT OF AAA MODEL Comparison Model and Experimental Results Particle Number Concentration AAA8 Comparison (Example) Simulated with Model Measured with APS Experimental Results 17 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
DEVELOPMENT OF AAA MODEL Comparison Experimental and Model Results Particle Number Concentration RC = Particle Number Reduction Coefficient 18 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
SCALING UP BOUNDARY CONDITIONS AMMD = Aerodynamic Median Mass Diameter 19 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
SCALING UP - SIMULATION RESULTS Number Concentration Reduction at 90% Model Predictions Time for RC Np = 90% versus Mass Concentration 20 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
SYNTHESIS An experimental system was developed by CSIC and tested together with CIEMAT within the PECA vessel facility for the acoustic agglomeration at 21 kHz of SiO 2 (0.3, 1, and 2.5 microns) and TiO 2 particles For treatment times about 80 seconds and particle number concentrations in the range 10 4 – 10 5 cm -3 the smaller particles (0.3 microns) experiment a reduction of over 90% with an acoustic intensity of about 155 dB . Under the same conditions the increase of the particle size due to ultrasound was mainly observed for 1 µm particles in which increases of up to 37% were measured . Experimental results confirmed that the ultrasound agglomeration effect improves with particle number concentration and size dispersion and is proportional to acoustic intensity and treatment time . A numerical model , based on the fundamental interaction effects acoustic waves – aerosol particles, was developed and experimentally validated . From the model the acoustic power required in case of a severe accident could be established 21 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
THANK YOU FOR YOUR ATTENTION! ANY QUESTIONS? ACKNOWLEDGEMENTS: The authors thank the European Atomic Energy Community (Euratom) for showing a strong interest in the PASSAM Project, and for funding it in the frame of the 7 th Framework Programme FP7/2007-2013 under grant agreement nº 323217 22 UIA46 Symposium, 24-26 April 2017, Dresden, Germany
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