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Advances on Containment Iodine Chemistry. ERMSAR 2008, Nesseber, Bulgaria, 23-25 September 2008. Presented by : Shirley Dickinson. Iodine Chemistry Participants in SARNET.

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Advances on containment iodine chemistry

Advances on Containment Iodine Chemistry

ERMSAR 2008, Nesseber, Bulgaria, 23-25 September 2008

Presented by : Shirley Dickinson

Iodine chemistry participants in sarnet
Iodine Chemistry Participants in SARNET

Nexia Solutions, Harwell (GB),EDF, Villeurbanne (FR)VTT, Espoo (FI)AECL, Chalk River (CA)IRSN, Cadarache (FR)AREVA-ANP, Erlangen (DE)Chalmers University, Gothenberg (SE) CIEMAT, Madrid (ES)Demokritos, Athens (GR)CEA, Cadarache (FR)IRSN, Saclay (FR) GRS, Garching (DE)


  • Iodine chemistry in containment highlighted in 5FP EURSAFE – further research needed to reduce source term uncertainties

  • SARNET objectives:

    • Improve understanding of chemical phenomena in containment  improve predictability of iodine behaviour

    • Common interpretation of test data

    • Production of new / improved models

    • Compilation of existing knowledge

Interpretation circles
Interpretation Circles

  • Radiolytic Oxidation (ROX)

  • Sump-Atmosphere Mass Transport (MAT & THAI)

  • Iodine in Passive Autocatalytic Recombiners (IPAR)

  • Iodine Data Book (IDB)

  • Phebus Interpretation (FPT2)

    • See presentation to ERMSAR 2007

Radiolytic oxidation of iodine rox
Radiolytic Oxidation of Iodine (ROX)

  • Formation of volatile iodine from irradiated solutions

    • Extensively studied before SARNET, reasonably good understanding

    • Data sparse in some areas (high T, high D)

    • Some improvements to modelling / validation required

    • Other uncertainties e.g. impurities

  • Radiolytic reactions of gaseous iodine to form solid oxide aerosols

    • Few experimental data

    • Limited modelling capabilities (gas phase only)

Radiolytic oxidation in solution
Radiolytic oxidation in solution

  • New data mainly from EPICUR tests

    • On-line measurement of iodine volatility from g-irradiated solutions

    • 16 tests performed during SARNET: High temperature (80, 120°C), pH 5 or 7, 2 – 3 kGy/hr, painted surfaces, Ar / air atmospheres

    • Conditions changed during tests to highlight effects

  • Data also released from intermediate-scale CAIMAN and RTF tests

  • Test of radiolytic oxidation models: ASTEC-IODE, COCOSYS-AIM, INSPECT, LIRIC

Rox conclusions from epicur
ROX conclusions from EPICUR

  • Model performance generally satisfactory at pH 5

    • Effect of temperature confirmed to 120°C

    • Improved estimate of borate-catalysed I2 + H2O2 reaction activation energy for INSPECT

  • Decrease in volatility at pH 7 less well modelled

    • Mechanistic models reasonably OK

    • Changes required to COCOSYS-AIM

    • Choice of radiolytic oxidation model in ASTEC-IODE

Radiolytic oxidation in gas phase
Radiolytic oxidation in gas phase

  • Experimental data from PARIS programme

    • Extend measurement of radiolytic destruction rates to lower concentrations

    • Effect of surfaces

  • Mechanistic modelling apparently overpredicts radiolytic oxidation rate

  • Modelling of aerosol formation needs to be developed

  • More work needed in this area

Mass transfer thai
Mass transfer (THAI)

  • Validation of mass transfer models against large-scale test data

    • THAI IOD-9 (60 m3 vessel)

  • I2 mass transfer from gas – sump

  • Transport in stratified sump

  • Uptake on steel walls

  • Condensate wash-out

Mass transfer thai 2
Mass transfer (THAI) (2)

  • Calculations with ASTEC-IODE, COCOSYS-AIM and LIRIC

  • All codes simulated the test reasonably well

  • Identified some improvements needed to models

  • More tests to be analysed in SARNET-2

Mass transfer mat
Mass transfer (MAT)

  • Extension of sump-atmosphere mass transfer models to evaporating conditions

  • Semi-mechanistic model based on

    • Two-film model

    • Heat - mass transfer analogy

    • Surface renewal theory

  • Comparison with data from SISYPHE programme

  • Further validation needed on large-scale test data

Iodine in passive autocatalytic recombiners ipar
Iodine in Passive Autocatalytic Recombiners (IPAR)

  • Thermal decomposition of iodide aerosols by PARs  gaseous iodine production

  • RECI experiments showed significant I2 production from aerosols heated to PAR operating temperature

  • Analysis of RECI results by ASTEC-SOPHAEROS and CFD-based aerosol modelling

    • I2 production predicted if equilibrium chemistry is assumed in the heated zone but chemical composition is frozen in the cooling zone

    • The “chimney” of a PAR may be equivalent to the RECI cooling zone giving similar effect in containment

Iodine in passive autocatalytic recombiners ipar continued
Iodine in Passive Autocatalytic Recombiners (IPAR) (continued)

  • Evaluation of the impact of an additional gaseous iodine source 24h after severe accident transient

    • ASTEC simulation on PWR-900 reactor

  • Concludes that recombiner issue merits further investigation as there could be a significant impact on the iodine source term

  • Knowledge gained could be applied to potential effect of PARs on ruthenium source term

Iodine data book idb
Iodine Data Book (IDB) (continued)

  • A large body of data has been used in the development of models and methodologies for iodine source term predictions

  • Research in the area tends to be diminishing

    • UK experimental programme ceased in 2003

  • Collation of experimental/theoretical data forming the basis of the Sizewell B safety case

    • Aqueous inorganic radiation chemistry, organic iodine chemistry, surface reactions, mass transfer, gaseous radiation chemistry

  • Keep up-to-date with results from future programmes…