FILTRATION OF IODINE WITH A WET ELECTROSTATIC PRECIPITATOR

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1 VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD FILTRATION OF IODINE WITH A WET ELECTROSTATIC PRECIPITATOR M. Gouëllo, T. Kärkelä, J. Hokkinen, A. Auvinen, P. Rantanen VTT Technical Research Centre of Finland Ltd.

2 Outline Why focusing on filtering gaseous iodine? PASSAM project Experimental facility Tests performed with molecular iodine Summary and upcoming tests 23/07/2015 2

3 Outline Why focusing on filtering gaseous iodine? PASSAM project Experimental facility Tests performed with molecular iodine Summary and upcoming tests 23/07/2015 3

4 Why focusing on filtering gaseous iodine? (Cs 137, I 131, Ru 103, ) Mitigation systems within a NPP, like sprays, suppression pools, particle filters are generally characterized as regards aerosol retention efficiency in the short term, but to a far lesser extent as regards volatile iodine retention or long-term behavior. 23/07/2015 4

5 Outline Why focusing on filtering gaseous iodine? PASSAM project Experimental facility Tests performed with molecular iodine Summary and upcoming tests 23/07/2015 5

Passive and Active Systems towards enhanced Severe Accident source term Mitigation - PASSAM project Exploring potential enhancement of existing source term mitigation devices.

6 Passive and Active Systems towards enhanced Severe Accident source term Mitigation - PASSAM project Exploring potential enhancement of existing source term mitigation devices. Demonstrating the ability of innovative systems to achieve larger source term attenuation. Existing filtration systems: - Pool scrubbing systems - Sand bed filters plus metallic pre-filters Innovative filtration systems: - Accoustic agglomeration systems - Spray agglomeration systems - Electric filtration systems - Improved zeolite filtration systems - Combined filtration systems 23/07/2015 6

7 Outline Why focusing on filtering gaseous iodine? PASSAM project Experimental facility Tests performed with molecular iodine Summary and upcoming tests 23/07/2015 7

$Values in WESP tests range Temperature [ºC] 100-300 20-65 Absolute Pressure [bar] 1 10 1 Gas mass flow rate [kg/s] 1.0 30.0 0.001-0.003 Gas composition [molar fraction] I 2 mass [kg] 3.0.10-3 Air: 0-25% 0-100% H 2 O v : 40-100% 0-70% H 2 : 0-2% 0 CO 2 : 0-40% 0 CO: 0-20% 0 I 2 concentration [ppm] 0-10 CH 3 I [kg] 4.$

8 Experimental facility Objectives, method and boundary conditions Boundary conditions in the tests compared to the limits presented in the State of the Art Report [1] Parameter Anticipated Value range Values in WESP tests range Temperature [ºC] Absolute Pressure [bar] Gas mass flow rate [kg/s] Gas composition [molar fraction] I 2 mass [kg] Air: 0-25% 0-100% H 2 O v : % 0-70% H 2 : 0-2% 0 CO 2 : 0-40% 0 CO: 0-20% 0 I 2 concentration [ppm] 0-10 CH 3 I [kg] CH 3 I concentration [ppm] 0-10 Aerosol concentration [kg/m 3 ] < Particle diameter [m] Decay heat [kw] ) Use of existing industrial systems WESP: Wet ElectroStatic Precipitator (with potential improvements) to severe accident conditions. 2) Determination of the best parameters related to the WESP for filtering iodine at room temperature oxidation of gaseous iodine, addition of droplets, number of corona needles, WESP wall flushing 3) Assessment of the collection efficiency in more realistic conditions at 65 C, with several steam contents and different I 2 and ICH 3 concentrations. 23/07/ [1] Committee on the Safety, of Nuclear Installations, Status Report on Filtered Containment Venting (No. NEA/CSNI/R(2014)7). Nuclear Energy Agency - Committee on the Safety of Nuclear Installations.

9 Experimental facility Collecting iodine: Stage 1 Air D1 Air D2 Steam Generator Gaseous iodine generator Reaction chamber I 2 (g) generator: - Generated by sublimation of I 2 pellets - Gas flow: Ar - Thermostatic bath: 60 C - Heated PFA tubing: 75 C - [I 2 ] i : 45 ppm ± 12 % O 3 (g) generator: - Generated by passing air through a corona discharge - [O 3 ] i : 9000 ppm O 3 generator 1) Oxidation of iodine to particles, i.e. I 4 O 9 or I 2 O 5 [2] 23/07/ [2] Vikis, A.C., MacFarlane, R., Reaction of Iodine with Ozone in the Gas Phase. The Journal of Physical Chemistry 89,

10 Experimental facility Collecting iodine: Stage 2 H 2 O or NaOH Air Air D1 Air D2 Steam Generator Atomizer: - Pressurized air: 1.4 bar - Corresponding flow rate: ~21 l/min - Water droplets diameter: ~10 µm Reaction chamber Gaseous iodine generator Spray Chamber O 3 generator (Ref. Glatt GmbH) 2) Agglomeration and dissolution of iodine 23/07/

11 Experimental facility Collecting iodine: Stage 3 H 2 O or NaOH Air Air D1 Air D2 Steam Generator Reaction chamber Gaseous iodine generator Spray Chamber WESP O 3 generator 3) Iodine chemistry in an electric field 23/07/

12 Experimental facility Collecting iodine: Stage 4 H 2 O or NaOH Air Air D1 Air D2 Steam Generator Exhaust Reaction chamber Gaseous iodine generator Spray Chamber WESP O 3 generator 4) Flushing the WESP wall 23/07/

13 Experimental facility Assessment of the collection efficiency [%] H 2 O or NaOH Air Exhaust Ejector diluter Sampling filter Sampling filter Ejector diluter ELPI Spray Chamber WESP ELPI CPC Vacuum CPC Moisture sensor Vacuum Moisture sensor Exhaust Exhaust Exhaust 23/07/ TEOM TEOM

14 Outline Why focusing on filtering gaseous iodine? PASSAM project Experimental facility Tests performed with molecular iodine Summary and upcoming tests 23/07/

1M) 86 l/min Effect of the applied voltage [I 2 ] i ~ 45 ppm [O 3

15 Tests performed with molecular iodine Importance of the oxidation step by O 3 [I 2 ] i ~ 45 ppm V = -25 kv T = 20 C Droplets NaOH (0.1M) 86 l/min Effect of the applied voltage [I 2 ] i ~ 45 ppm [O 3 ] i ~ 9000 ppm T = 20 C Droplets NaOH (0.1M) 86 l/min 23/07/

16 Tests performed with molecular iodine [I 2 ] i ~ 45 ppm [O 3 ] i ~ 9000 ppm V = -25 kv T = 20 C Effect of droplets addition in the spray chamber and nature of the solution 23/07/

17 Tests performed with molecular iodine [I 2 ] i ~ 45 ppm [O 3 ] i ~ 9000 ppm V = -25 kv T = 20 C Droplets NaOH (0.1M) Effect of flushing the WESP wall with NaOH solution (0.5 l/min) 23/07/

18 Outline Why focusing on filtering gaseous iodine? PASSAM project Experimental facility Tests performed with molecular iodine Summary and upcoming tests 23/07/

19 Summary and upcoming tests Observations from first tests: Results showed a strong decrease of the collection efficiency for voltages below 10 kv (negative). When the flow rate is increased at the corona vicinity, the collection efficiency is decreased. Nature of droplets solution showed its importance in the collection efficiency of I x O y particles. Wall flushing with NaOH solution allows to reach a collection efficiency of 99.9% up to 132 l/min. On-going tests: At 65 C with steam (0 vol.% steam content 70 vol.%); Varying I 2 concentrations; Testing collection efficiency on ICH 3. Long-term aims: The precipitator scale and design will have an impact on the performance of the WESP. In order to assess the collection efficiency for different size of WESP, next steps are to: Understand the phenomena which play a role in the WESP; Develop models/correlations; Try to extrapolate of developed models to accident conditions. 23/07/

20 Thank You for Your Attention The research leading to these results is partly funded by the European Atomic Energy Community s (Euratom) Seventh Framework Programme FP7/ under grant agreement n

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