GLOBAL MODEL FOR IODINE BEKAVIOUR FN REACTOR CONTAaYMENT
Anandhi Narayanan
A thesis submitted in conformity with the requirements for the degree of Master of Applied Science Graduate Department of Chemical Engineering and Applied Chemistry University of Toronto
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Master of Applied Science, May 2000
Anandhi Narayanan
Graduate Department of Chernical Engineering and Applied Chemistry
University of Toronto
ABSTRACT
The objective of this thesis was io develop a mechanistic model to simulate iodine behaviour within the containment structure of a nuclear generating station. The model included both aqueous and gas phase radiolysis and interfacial mass transfer.
Validation of the model was conducted for each phase separately and the combined model was applied to a few reactor accident scenarios. The aqueous model successfùlly reflected various experimental data over a wide range in pH, iodide concentration, temperature, and dose rate. The incorporation of gas phase chemistry served to determine the dominant chemical forms of gaseous iodine. In addition, it was observed that hydrogen, likely to be present in the containment atmosphere, would hinder the elimination of molecular iodine. Finally, the interaction of iodine with nitrogen oxides was signincant when compared to reactions with ozone. Hence, the deposition of ozone onto surfaces did not impact iodine behaviour. The development of this model will serve as a usefbl tool for reactor safety assessments. The people acknowledged in this section assisted by either providing technical assistance or emotional support while completing this thesis. 1 am very grateful to them.
Professor G.J. Evans for his supervision, patience and guidance throughout the course of my research. I tmly appreciated your critical review of my thesis document. You enabled me to learn a great deal.
NSERC for fbnding my research.
Professon M.J. Philiips and C.A. Mims for their participation in my defence cornittee and reviewing my thesis document.
The entire nuclear and aerosol research group for their friendship; in particuiar Tutun for his constant assistance throughout, Fariborz for helping me get started and Lis for critiquing my presentation.
Paul, Samar and Vani for the coffees, lunches and chats: a much needed break.
My mother, father, Desi, Anin and Rudy for their unconditional love and support. Finally God, without whom I would not be. 1.0 INTRODUCTION...... w...w..m.I*000.8*a...... 8...e...... 8...... f 2.0 LITERATURE REVIEW ...... 4 2 .L Severe Reactor Accidents ...... 4 2.2 Aqueous Phase Radiolysis ...... 6 2.2.1 Statw cf Iodine Models ...... 6 2.2.2 Aquesous Phase Chemistry ...... 11 2.2.2.1 Effect of pH ...... 11 2.2.2.2 Effect of Temperature ...... 12 2.2.2.3 Effect of Total Iodide Concentration ...... 12 2.2.2.4 Effect of Dose Rate ...... 13 2.2.2.5 Effect of Dissolved Gases ...... 13 2.3 Gas Phase Radiolysis ...... 15 2.3.1 Status of Models ...... 15 2.3.2 Gus Phase Chernistry ...... 17
3.1 Introduction to Radiation Chernisûy ...... 22 3.2 Aqueous Phase Radiolysis ...... 22 3.2.1 Water Radiolysis ...... 23 3.2.2 Aqueous Iodine Chemistry ...... 24 3.3 Gas Phase Radiolysis ...... 26 3.3.1 Primav Yields ...... 27 3.3.2 Radiation Chemistry of Moist and Dry Air ...... 29 3.3.3 Gas Phase lodine Chemistry...... 31 3.3.4 Ozone Deposition ...... 32 3.4 interfacial Mass Transfer ...... 36 4.0 MOOEL DEVELOPMENT ...... e...... ~~oe.~...... 38 4.1 Facsimile Code ...... 38 4.2 Basis for Aqueous Mode1...... 38 4.3 Basis for Gas Mode1...... 39 4.4 Combined Mode1 ...... 40 5.0 RESULTS AND DISCUSSION ...... m...... 41 5.1 Aqueous Mode1 Analysis ...... 4 1 5.1. I Water Radiolysis ...... 41 5.1.2 ludine Volatility ...... 48 5.1.2.1 Impact of pH and Iodide Concentration...... 48 5.1.2.1.1 Flow Experiment...... 49 5.1 .2. L .2 Sparging Apparatus Experiment ...... 50 5.1.2.1.3 Effect of pH for High Iodine Concentration ...... 53 5.1.2.1.4 Effect of pH for Low Ioduie Concentration ...... 54 5.1.2.2 impact of Dose Rate ...... 55 5.1.2.3 Impact of Temperature...... 58 5. 1.2.4 Impact of Organics...... 61 5.1.3 Summary of Mode l...... 64 5.2 Gas Model .b slysis ...... 67 5.2.1 Air Radiolysis ...... 67 5.2.1.1 Ozone Yield: Theoreticai Estimation in Dry Air ...... 67 5.2.1.2 Ozone Yield: Theoretical Estimation in Moist Air ...... 69 5.2.1.3 Ozone. . Formation: Experimental Cornparison ...... 71 5.2.1.4 Nitnc Acid Formation ...... 75 5.2.2 Iodine Elimination ...... 75 5.2.2.1 Mechanisin for Iodine Elirnination ...... 76 5.2.2.2 Effect of Steam ...... 79 5.2.2.3 Effect of Dose Rate ...... 80 5.2.2.4 Effect of Temperature ...... 80 5.2.2.5 Effect of Ozone ...... 81 5.2.2.6 Effect of Hydrogen ...... 82 5.3 Combined Mode1 Evaluôtion ...... 83 5.3.1 Bench Scale Tests...... 83 5.3.2 Large Scale Tests ...... 89 5.3.3 Accident Scenario Condition ...... 93 5.4 Sensitivity Analysis ...... 105 6.0 CONCLUSIONS ...... 109 6.1 Aqueous Mode1 ...... 109 6.2 Gas Mode1 ...... 1 Il 6.3 Combined Mode1 ...... 1 12
7a0 RECOMMENDATIONSaaa~aaaaee~aao~aea~aa~e~~maaoaaoaaaaaaaemaeeeaoaoaaeaaaaaeaaaao113
A .1 FACSIMILE Code ...... 127 A.2 References for FACSIMILE Mode1 ...... 175 A.3 Summary of Madelled Reactions and Kinetics ...... 189 A.3.1 Aqueow Reactions...... 189 A.3.2 Gaseous Reactions...... 195 A.4 Summary of Amendments to Aqueous Model ...... 200 AS Summary of Amendments to Gas Mode1...... 207 B .1 Rate Constants for Selected Iodine Species ...... 2 14 B .2 Temperature Dependent Rate Constants ...... 214 8.3 Iodine Hydrolysis ...... 215 B.4 Henry's Law Coefficients ...... 216 APPENDIX C ...... 4...... ~...... 218 C. 1 Kinetics of OH + Iz ...... 218 C.2 Kinetics of I2 + O3...... 218 C.3 Kinetics of 10 + IO ...... 219 C.4 Kinetics of HO2 + IO ...... 220 APPENDIX D .....e...... ~...... ~...... m...221 FIGURE5.1 : ESTIMATIONOF LIQUIDSIDE MASS TRANSFER COEFFICIENT ...... 42 FIGURE5.2. RADIOLYSISOF WATERCONT~G H202 AND H2...... 43 FIGURE5.3: HYDROGENPEROXIDE FORMATION FROM THE RADIOLYSISOF WITH DISSOLVEDH2/02 ...... 44 FIGURE5.4: EFFECTOF DOSERATE ON H202PRODUCTION FROM DEARATEDSOLUTIONS ...... *...... 45 FIGZ~X5.5. HITIROGEXPEROXDE FOR~~IATIOX L'ROM ~DIOLYSISOF PUE WATER...... 46 FIGURE5.6: EFFECTOF HEADsPACE ON H202FORMATION FROM IRRADIATEDloJ M IODIDESOLUTIONS ...... 47 FIGURE5.7. EFFEC~OF HEADSPACEON H202FORMATION FROM WATER RADIOLYSIS .... 48 FIGURE5.8. IODINEVOLATILIZATION RATES: ~~EASURED AND PREDICTEDRESULTS ...... 50 FIGURE5.9. EFFECTOF PH ON I2 VOLATUITYAT A LOW DOSERATE (0.26 KGY/HR)...... 52 FIGURE5 .Io: EFFECTOF PH ON I2 VOLATILITYAT A HIGHDOSE RATE (1 -95 KGY/HR).... 52 FIGURE5.1 1 : IODMEOXIDATION MECHANISM FOR HIGHIODIDE CONCENTRATION ...... 53 FIGURE5.12. IODINEOXIDATION MECHANISM FOR LOW IODIDE CONCENTRATIONS...... 54 FIGURE5.13 : EFFECTOF DOSERATE UNDERVARIOUS MASS TRANSFER CONDITIONS ..... 57 FIGURE 5.14: EFFECTOF PH ON IMPACT OF DOSERATE ON IODINE VOLATILIZAT~ONRATE UNDERHIGH MASS TRANSFERCONDITIONS (Km = sx IO-' DM'S) ...... 57 FIGURE5.15. EFFECTOF TEMPERATUREON IODMEPRODUCTION ...... 60 FIGURE5.16. LxFORMATION FROM IRRADIATEDIODIDE SOLUTIONS ...... 61 FIGURE5.17: MODELLEDRESULTS COMPARED WITH &CL AND IPSN ORGANIC EXPERIMENTS...... +...... t...... 63 FIGURE5.18: MAXIMUMTRANSFER RATE OF IODMEFROM IRRADWTEDIODIDE SOLUTIONS ...... 64 FIGURE5.19. MODELLEDSYSTEM FOR ESN EXPEREMENTS...... 65 FIGURE5.20. IPSN EXPERIMENTALDATA vs . MODELLEDRESULTS ...... 66 FIGURE5.21: COMPARISONOF MODELLED VS . EXPERMENTAL&SULTS M THE PRESENCE AND ABSENCEOF ORGANICS(FTR/TIME = FRACTIONTRANSFERRED PER SECOND A~RA GNEN AMOUNTOF TIME)...... 67 FIGURE5.22. PREDICTEDOZONE YELD FROM ~RADIATEDDRY AIR ...... 69 FIGURE5.23. PREDICTEDOZONE YELD FROM ~RRADIATEDMOIST AIR ...... 70 FIGURE5.24: IMPACT OF MOISTUREON OZONEPRODUCTION: DRY AND SATURATEDAIR AT 293 K ...... 70 FIGURE5.25: PREDICI'EDOZONE CONCENTRATIONS FROM GERMANAND U OF T MODELS ...... 73 FIGURE5.26. OZONECONCENTRATIONS ROM ~RADIATEDMOIST AIR AT 298 K ...... 73 FIGURE5.27. OZONECONCENTRATIONS FROM IRRADIATEDAMB~ AIR AT 298 K...... 74 FIGURE5.28 (A) AND (B): MODELLEDAND EXPERLMENTALRESULTS FOR I2 EL~ATION ...... 76 FIGURE5.29: MECHANISM FOR Iz ELMINATIONIN THE GASPHASE FOR HIGHIODINE CONCENTRATIONS...... 77 FIGURE5.30: MEcKANISM FOR I2 ELIMINATIONIN THE GASPHASE FOR LOW IODINE CONCENTRATIONS...... 78 FIGURE5.3 1 (A) AND (B): MODELLEDAND EWERIMENTALRESULTS FOR I2 ELIMMATION ACCOUNTINGFOR HI ...... ,...... 79 FIGURE5.32: EXPERIMENTALAND MODELLEDRESULTS FOR 12= ELIMMATIONDURING ~RRADMTIONOF MOISTAND DRYAR ...... 80 FIGURE5.3 3 : EFFECTOF SURFACEAFFINITY ON OZONECONCENTRATIONS ...... 8 1 FIGURE5.34: EFFECTOF VAEUOUSHYDROGEN COMPOSITIONS ON IODINEFRACTION ..... 82 FIGURE5.35: MODELLEDVS. EXPERIMENTALRESULTS FOR PSN TEST~~TRLX ...... 84 FIGURE5.36: A COMPAEUSONBETWEEN AQUEOUS AND COMBINEDMODEL RESULTS FOR THE FRACTIONALREMOVAL RATE CALCULATEDFOR THE NOCOMPARTMENT IPSN EXPEUMESTAL COXDIT~OXS...... ,...... 1,...... 85 FIGURE5.37: PREDICTEDPC FROM COMBMEDMODEL 1 8 HOURS &TER RADIATION .87 FIGURE5.38: PREDICTEDWC FROM AQUEOUSMODEL 18 HOURS &TER ~RRADIATION... 87 FIGURE5.39: TOTALGASEOUS IODNE CONCENTRATION...... 90 FIGURE5.40: EXPERIMENTALAND MODELLEDRESULTS FOR RTF ZINC-PRIMERCOATED VESSELEXPERTMENT ...... 93 FIGURE5.4 1: PREDICTEDFRACTION TOTALGASEOUS IODME 24 Hm.AFTER LARGE LOCA ACCIDENTFOR CANDU SYSTEMWITH THE GASPHASE CHEMISTRY ON OR OFF ...... 95 FIGURE5.42: A COMPAFUSONOF PREDICTED I2 CONCENTRATIONSAS A FCMCTION OF TIME:FRENCH MODEL VS, U OF T MODEL...... *.. ,...... 99 FIGURE5.43: IMPACT OF HYDROGENON NET I2 VOLATILIIY24 HRS. AFl"ER ~RRADIATION ...... 100 FIGURE5.44: EFFECTOF GASVOLUME AND H7CONCENTRATION ON IODINE VOLATILITY &TER 24 HRS OF RADIATION ...... 10 1 FIGURE5.45: CODECOMPARISON OF PREDICTEDNET RELEASEOF i0DiNE AT F 60000s ...... 102 FIGURE5.46: COMPARISONOF IODINE FRACTIONTRANSFERRED UNDERALL ACCIDENT SCENARI~~EXAMND USINGTHE U OF T COMBINEDMODEL ...... 103 FIGLIRE5.47: EFFEC~OF I2O3AEROSOL SETTLMG RATE ON TOTALGASEOUS ATOMIC IODINEFOR CONDITIONSOUTLMED IN TABLE5 22...... 104 FIGURE5.48: SENSITIVITYANALYSIS OF AQUEOUSMODEL TO ALTERATIONSIN SPECIFIC RATE CONSTANTS,REFERENCE TABLE 5.3 FOR CONDITIONS...... 106 FIGURE5.49; SENSITIVITYOF COMBMEDMODELLED ~~SULTS TO ~ETICS OF It f No3 UNDERCONDITIONS APPLICABLE TO RTF STPJNLESSSTEEL EXPERIMENTS, REF. TABLE5.18 +...... IO8 FIGURED. 1: INITIAL OZONEFORMATION MECHAIVISM ...... 223 TABLE2.1. TESTMAT RU(. FOR iNSPECT VALIDATION...... 8 TABLE2.2. TEST MAT^ FOR IODE VALIDATION...... 9 TABLE2.3. RTF TESTCONDITIONS FOR ISP CODEVALIDATION ...... 10 TABLE2.4. HYDROGENPEROXDE CONCENTRATION FROM WATERRADIOLYSIS ...... 14 TABLE2.5. YIELDSFROM MODELPREDICTIONS ...... 15 TABLE2.6. OZONEDESTRUCTION CYCLES ...... 19 TMLE2.7. SIEXESS E.XPE.PLMENTAL TEST .M 4m.x ...... 20 TABLE3.1 : PWY YELDSFROM WATERRADIOLY SIS ...... 23 TABLE3.2. TOTALMASS A~NTUATIONCOEFFICIENTS FOR GASSPECIES ...... 27 TABLE3.3. PR~MARYYELDS FROM OXYGENRADIOLYSIS ...... 27 TABLE3.4. PRIMARYYIELDS FROM NITROGENRADIOLYSIS ...... 28 T.ULE 3.5. PRIMARYYIELDS FROM WATERVAPOUR RADIOLYSIS ...... 28 TABLE3.6. REACTIONPROBABILITIES ...... 36 TABLE3 .~.CALCULATED OZONE DEPOSITIONAL VELOC~TY ...... 36 TABLE5.1 : HOCHANADEL[19] EXPERLMMTALMATEUX FOR WATERRADIOLYSIS ...... 43 TABLE5.2: NARAYANAN[16] EXPEFUMENTALMA~RD( FOR H202FORMATION DURMG WATERRADIOLYSIS ...... 45 TABLE5.3: TAGHIPOUR[12] EXPERIMENTAL MA^ FOR IODINEVOLATILZATION RATE MEASUREMENTS...... 49 TABLE5.4: ASHMOREET . AL . [Il] EXPERIMENTALMATU FOR IODMEVOLATIL~ZATION FROM A SPARG~NGAPPARATUS ...... 51 TULE ~.~:GORBOVITSKAYAET. AL . [25] EWERU~~ENTALMATRIX FOR Iax FORMATION. 60 TABLE5.6. PSN EXPERIMENTALMATRIX FOR ORGANICSIN GAS PHASE ...... 62 TABLE5.7. PSN EXPERIMENTALMATRIX FOR ORGAMCSM AQUEOUSPHASE ...... 62 TABLE5.8: AECL EXPERIMENTALMATEUX FOR ORGANICSiN GAS,AQUEOUS AND BOTH PHASESEXPE~NTAL RESULTS ...... 63 TABLE5.9. GEOMETRICPARAMETERS FOR IPSN EXPEIUMENTALAPPARATUS ...... 65 TABLE5.10. PSN TWOCOMPARTMENT EXPER~MENTAL TEST MATRUC ...... 65 TABLE5.1 1: FUNKE ET . AL . [39] EXPERIMENTALhlAfRlX FOR OZONEFORMATION ...... 72 TABLE5.12. OZONEEXPERIMENTAL MATRLX AT U OF T ...... 72 TAEBLE5.13: CONCENTRATIONSOF OZONE AND !&%IN NOxSPECIES M GASPHASE ER 20 HRS. OF IRRADIATION...... 74 TABLE5.14. ASKMOREET . AL . [64]EWER~MENTAL MAT^ FOR HNQ3FORMATION ..... 75 TABLE5.15. FUNKEET . At . [39] EXPER[MENTALMATRIX FOR I2 ELIMINATION...... 76 TABLE5.16. MODELLEDMATEUX FOR H2ÙMPACT ...... 82 TABLE5.17. EFFECTOF I2 CONC~TIONON IMPACT OF H2...... 83 TABLE5.1 0 (PAGE 65): IPSN TWOCOMPARTMENT EXPERIMENTAL TEST MATRIX ...... 84 TABLE5.1 8: EVANS[14] EXPER~MENTALM.ATRE FOR IPC ...... 86 TABLE5.19. RTF STAINLESSSTEEL EXPEFUMENTAL MATEUX ...... 90 TABLE5.20. RTF ZINC-PRIMERCOATED EXPER~MENTAL MA TRUC...... 92 TABLE5.2 1: ACCLDENTSCENARIO TEST MATEUX ...... 94 TMLE 5.22: PART~TION~GOF IODINE UNDER CmU ACCIDENT s~EN.4~10: EFFECT OF TABLE5.23. ACCIDENTSEQLIENCE CONDITIONS FOR FRENCH PW'R ...... 97 TABLE5.24. ACCIDENTSEQUENCE CONDITIONSFOR PmiN SPAIN...... 98 TABLE5.25: SENSITIV~TYANALYSIS OF AEROSOLSE~LING RATE ON GASPHASE IODME SPECIATION ...... 104 TABLE5.26: RATE CONSTANTMODIFICATION TO TEST SENSITIVI~OF AQUEOUS MODEL Np = Mass attenuation coefficient (cm2ig)
PRG = Production rate in the gas phase (mol~e~~s-'~~'~~molecule~~)based on the dose rate (kGy/hr) wj = Weighi tiaction of the parent atom from which the species is formed vd = Depositional velocity si = Surface area of ih sUCface y = Surface uptake
Js = Net flux of species to surface (rn~l~dm~~.s'')
Cs= Pollutant concentration adjacent to surface (mol~dm") cv> = Boltzmann velocity (crnes-') k = Boltzmann constant (Ki) m = Mass of molecule (g)
T = Temperature (K)
Jo = Flux by diffision (rn~l.dm'~*s-')
9) = Species molecular diffisivity (m's-')
C = Species concentration (M)
6, = Concentration boundary layer (dm)
KA= Adsorption coefficient (Ws)
= Interfacial surface area (dm2)
KTL= Liquid side mass transfer coefficient (Ms)
KT== Gas side mass transfer coefficient (dmls) H(x) = Henry's Coefficient for species x
&Ji = Concentration of species X in aqueous phase at gas-liquid interface (M)
[XJi = Concentration of species X in gas phase at gas-liquid interface (M) ti~= Half Life (s)
V, = Gas phase volume (dm3)
Vi = Aqueous phase volume (dm3) k = Reaction rate constant 1.0 INTRODUCTION
When a neutron bombards a fissile nucleus, initiating a fission chah reaction, a large amount of energy is released. This energy can then be captured and converted to a form usefbl for human needs, namely electricity. The power generated from nuclear reactors is founded on this principle. In general, a nuclear generating station comprises:
i) A reactor: where the fission process occurs;
ii) A heat transport system: to convey the energy released to the steam
generators; and
iii) Steam generators: responsible for producing electricity.
During normal operation, this process is, for the most part, environmentally benign and highly efficient. Fission products are primarily retained within the fuel elements of the reactor core. However, srnall leaks through cracks in the fuel cladding are inevitable resulting in the passage of some radioactive species into the primary coolant water.
While provisions have been included to mitigate potential accident scenarios, the failure of these systerns must also be considered. Under these circumstances the release of radioactive material fiom the containment building could have adverse environmental consequences.
In the event of a severe reactor accident, typically resulting fkom a breech in the main pipe of the heat transport system, higher concentrations of fission products fiom the core inventory are expected in the containment building. Amongst these is cesium iodide, an aerosol, which dissolves to yield iodide when contacted with water. The complex chemistry occuming in both aqueous and gas phases will lend to the oxidation and subsequent volatilkation of iodineL. Once in the containment atmosphere, iodine can be released through deliberate venting posing a serious health concem. Iodine accumulates in the thyroid causing an increased risk of cancer. As a result, one aspect of nuclear reactor safety is to investigate the factors influencing the behaviour of iodine under accident conditions.
Ultimately, the development of a model to simulate iodine behaviour will sewe as a useful tool for safety assessments. To date, focus has been placed predominantly on aqueous phase chemistry since most of the iodine will initially be concentrated in the water pool. The impact of gas phase radiolysis bas only recently gained interest arnongst the iodine cornmunity. nie goal of this research project was to create a mechanistic rnodel to include aqueous and gas phase chemistry, as well as interfacial mass transfer.
The model developed for each phase was validated against results fiom available bench scale experirnents covering a wide range of conditions. Specifically, the model was judged on its ability to respond to various initial iodide concentrations, pH values, temperatures, and dose rates. The joint model was cornpared against results 6om the aqueous rnodel to assess the impact of gas phase radiolysis. Experimental data Rom both bench scde and intermediate scale test facilities were used to evaluate the combined model. Finally, the combined model was applied to the simulation of iodine behaviour for a few reactor accident scenarios.
' Iodhe in this thesis nfers to iodine in any of iîs many chemicai fom. Specfic chernical fomare referred by their names or fornula (e.g. iodide, I; rnoIecuIar iodine, Ib iodate, IO; etc). The topics covered in this document include:
A literature review explaining the sequence leading to a reactor accident and the conditions prevailing, the status of aqueous and gaseous iodine models, and a summary of the impact of specific parameters on aqueous and gas phase chemistry. The section to follow discusses key theoretical aspects, namely details of the chemistry occurring during both gas and aqueous phase radiolysis, the transport equations used to determine the ozone depositional velocity on steel and painted surfaces, and the expression used to descnbe interfacial mass transfer of al1 species. A brief summary of the model development is presented in the fourth section. Section five describes the model validation process, presenting and explaining the results obtained. Finally the 1st two sections provide an overview of the conclusions derived and recommendations for future research. 2.0 LITERATURE REVIEW
2.1 Severe Reactor Accidents
During normal operation the coolant, in the primary heat transport (PHT)system of a
CANDU reactor or the reactor coolant system (RCS) of a light water reactor (LWR), absorbs the heat produced i?om nuclear fission in the fuel. Under these conditions, the fuel and coolant properties are of interest as opposed tu the transport of other material, such as fission products and oxidized material. However, during a severe accident the mobility of these species becomes increasingly important as they pose a hazard to the environment. Cesium, iodine and tellwium are of greatest concem during the early stages of a severe accident sequence, while additional fission products such as bariurn and strontium may be released fiom a molten core [l]. Ongoing interest in iodine stems fiom its potential radiobiological impact, if released in the environment. This species accumulates in the thyroid glands, causing an increased risk of cancer. in the aqueous phase iodine can be contained during the event of an accident. However, when volatile, it becomes difficult to manage its spread. As a result, understanding iodine behaviour in the reactor containment is a necessary safety requirement.
There are several types of reactor accident and within each the degree of severity cm vq. A large loss of coolant accident (LOCA) is considered the worst design basis accident. Here the coolant fails to adequately rernove heat generated, resulting in a breach in the RCS or opening of a relief valve. If temperatures increase an eventual loss to the fuel cladding integrity will occur, resulting in a significant release of fission products. Continued failure of sdety systems may lead to a core meltdown, wherein the 131 134 molten matenal accumulates at the bottom of the pressure vesse1 and I, Cs and '"CS are introduced into the coolant Stream. Eventually this molten material may be transported into the reactor containment. Based on the core inventory of a Light Water
Reactor (LWR), an iodide concentration of < 1x10~M is expected in the containment
under core meltdown conditions. in addition, boric acid, degraded organics and metallic
species will be present in the aqueous mixture. Finally, lithium hydroxide, present in the
spray solutions, is intentionally introduced to. increase the sump water pH [3].
In addition to a complex aqueous composition, the containment has an enormous gas
volume. The aidsteam mixture present in the containment during an accident will
contain varying bels of hydrogen gas, depending on the severity of the accident. The
hydrogen distribution will be inhomogeneous, with higher concentrations found near
metallic surfaces. Under a design basis accident (DBA) where the emergency core cooling system (ECCS)is operating correctly, hydrogen will accumulate as a result of
prolonged water radiolysis and reaction of metals with aqueous sprays. For a 1300 MW
PWR with a 65 000 m3containment, the atmosphere will probably contain 2.5 vol% Hz.
If the accident resuits in a degraded core, the zircaloy metal cladding of the fuel will react
with the steam producing up to 7 vol% of H2in an equal volume containment at 2 atm
and 90°C. Finaily, if core meltdown should occur, concentrations as high as 15 vol.%
can be expected [2].
The coacrete material of the containment acts as a heat sink, thereby causing stem
condensation along the containment wall. Paint, coating the containment wall, serves as a surface for species deposition, as well as a source of organics leaching both into the aqueous and gas phases. Finally, the system is Mercomplicated by the impact of radiation. Radiation energy in the aqueous phase is primarily absorbed by water, the dominant substance. In contrast, in the gas phase the energy is distributed arnongst the compounds present. Ionizing radiation produces excited species that are highly reactive creating an interesting chernical envuonment.
2.2 Aqueous Phase Radiolysis
The potential for ioduie to become volatile depends on the aqueous chemistry. As a
result, aqueous phase radiolysis has been, and continues to be, examined by iodine
researchers. Much arnbiguity remains regarding specific mechanisms, and the impacts of
temperature and organics.
2.2.1 Status of lodine Models
Several international initiatives have been undertaken to develop codes that mode1 iodine
behaviour in reactot containment. The motivation stems fiom the need to quantifi the
volatilization of iodine under reactor accident conditions. Using these codes the potential
hazards cm be assessed and necessary safety measures can be taken. The most well
known models are LIRIC (AECL Canada), INSPECT (LIK), IMPAtR (Switzerland and
Gemany) and IODE (France and Spain).
There are two schools of thought with respect to the method of modelling. One assumes
a mechanistic approach, while the other adopts an empirical one. Both LIRIC and
INSPECT are based on a mechanistic approach. As a result, their reaction sets are
extensive (approx. 150 reactions) in order to consider al1 significant reaction pathways. IMPAIR and IODE,on the other hand, take the empincal approach, which focuses on deriving a selected set of reactions in order to represent a more complex mechanism.
Naturally, there are benefits and downfalls to each. The mechanistic models require experimental data on specific reactions to determine necessary kinetic parameters. Many unresolved issues remain in determining some of these. Empincal models obtain kinetic data fkom experimental curve fitting and as a result, their applicabiliîy is limited to the experimental conditions upon which they are based. This method is less tedious, thereby allowing for a more complete picture of the accident scenario to be developed in a shorter time hune. For the same reason, the rnethod also lends itself to the possibility of neglecting potentially important species. That is, the expression representing a pathway or process may only be applicable to a specific case. Clearly, researchers attempt to include al1 known phenornena and constantly modib their models as their understanding improves. Mode1 validation is continually required. Some success has been obtained using both methodologies.
LIRlC 3.0, the latest version, was concluded to adequately model the effects of radiation, pH and dissolved oxygen on iodine reactions, aqueous-gas phase mass transfer and water radiolysis [4]. The effect of adsorption to surfaces, organics and trace metal impurities still required investigation. The model was tested against RTF experiments perforrned in stainless steel and vinyl painted vessels. The only parameter varied was pH, which spanned a range of 5-10. Both dose rate and initial iodine concentrations remained constant. lnterfacial mass transfer was included and the only adsorption phenornenon considered was the retention of iodine on SUffaces in contact with the gas phase. A cornparison of the INSPECT model with experimental data was published by Barton and Sims [SI. The aim of these authon to was investigate the rnodel's capabilities to predict iodine trends over an applicable pH and temperature range. Experiment results obtained by these authors as well as other laboratones were used to validate the model.
The experimental conditions selected resulted in the test matrix illustrated in Table 2.1.
Table 2.1: Test Matrix for INSPECT Validation Parameter Condition Temperature (OC) 20-90 Dose (kGy) i .9-3 5 pH 4.6-8 L
Experimental data, on the effect of temperature, were limited to1 a weakly acidic condition at high dose. The model concurred with the experimental results, suggesting that II fmation was inhibited at elevated temperatures. For temperatures higher than 30°C, the model under-predicted the experimental results by 40%. The effect of temperature variation during post-irradiation was found to be negligible. Attempts to simulate iodate were less successful, amibuted at least in part to the complexity of the system. However, the authors concluded that iodate was not a prionty concem.
IMPAIR, which uses a minimum set of differential equations and considers only six
iodine species, namely 12, HOI, I', IOj-, CHjI and Ag1 was validated against radioiodine
test facility (RTF) experimental results [6].Unfominately, the conditions explored
involved both organics and I2 deposition on painted vessels, neither of which are
applicable to the scope of this thesis. Only two pH conditions were tested, pH 5.5 and 9
and similar to the LIRIC evaluation, no variations to dose rate or iodine concentration
were made. Validation of IODE [7] against IPSN experiments, AECL experiments and AEAT experiments was conducted. The modelled experimental conditions have been swnmarized in Table 2.2.
Table 2.2: Test Matrix for IODE Validation Parameter Condition Temperature (OC) acidic 20-40 medium onlv
1 Dose Rate (kGy/hr) 1 0.26-1.95 1
The effect of initial iodine concentration was not examined. The predicted trends compared well with the expenmental results. However discrepancies between radiolysis correlation coefficients derived from two different experimental approaches raises questions regarding the ability of the mode1 to correctly predict iodine behaviour under different scenarios. The modelled impact of dose rate opposed experimental trends, however the effect of pH was well represented.
An international initiative to compare different code predictions for a given physical problem has been ongoing (International Standard Problems (ISPs)). The results of an exercise involving LIRIC, MELCOR-1, IMPAIR and IODE was presented during the
OECD Workshop in Finland 1999 [8]. Al1 codes were compared against RTF results produced at AECL's Whiteshell Laboratories. The experimental test conditions are summarized in Table 2.3. Table 2.3: RTF Test Conditions for ISP Code Validation 1 Parameter 1 Condition
1 Dose Rate &Gy/hr) 1 1.4 1 1 Vesse1 Twe 1 Stainless Steel 1
Ail the modeis inciuded the airiwater interfacial mass trisuisfer of iodine and surfacc adsorption of gaseous iodine as a reversible adsorption-desorption process. The results of each mode1 were evaluated based on their ability to predict gas phase iodine concentrations to within an order of magnitude for al1 pH values, and aqueous phase concentrations to within 20% as a function of the. More emphasis was placed on the aqueous phase since it served as the source of iodine. While many of the models overestimated the aqueous concentration, the adsorption onto the surface was equally underestimated. In terms of speciation, al1 models concurred that iodide was the predominant species. The fraction of iodate experimentally observed was Iess than 1% of the initial iodide concentration. The modelling of iodate, however, remains tsnresolved.
The authors established that models are quite sensitive to the selection of both mass transfer parameters and surface adsorption constants for 12. Consequently, the volatility predictions are affected. Comparing modelled results, independent of organics or surfaces, revealed differences in predicted iodine concentrations. Therefore, it is obvious a proper description of the aqueous chemistry remains a prionty as it is thought to ultimately dictate iodine behaviour. 2.2.2 Aquesous Phase Chemistry
Recognizing the importance of aqueous chemistry, iodine research has focused heavily on the factors affecting its behaviour in an aqueous medium.
2.2.2.1 Effect of pH
Understanding the impact of pH on iodine volatility is essential to adequstely mode! accident scenarios. Any combination of organics, dissolved gases, buffers or additives will affect the solution pH. Furthemore, these in conjunction with radiation will increase the complexity of the system. Several bench scale tests [9,10,11,12,13,14] and intermediate scale experiments [15] have shown that iodine volatility is suppressed under alkaline conditions. For iodide solutions in the range of 10" - 104 M the iodine partition coefficient (IPC)was detemined to Vary between 200 - 1000 over a pH range of 4-6
[IO]. Evans [14] reported iPC values for irradiated IO^' M and M solutions to Vary fiorn below lo3 at pH <5 to above 10' for pH >8.
Under acidic conditions, Sirns et. al. [II] report an "Sm shaped cwefor the dependence of iodine volatiliîy on dose rate. The explanation was given as follows. Initially the production of eAqand H dominate over OH. Thus, while hydroxyl is being produced the volatility of iodine is minimal; however once H202has accumulated it cornpetes with and Ot for the hydrated electron increasing the hydroxyl yield. Several bench scale shidies [16,17,18,19,20] have shown that hydrogen peroxide formation increases under acidic conditions. Sims et. al. [Il] suggest higher yields result fiom a favoured reaction of HOC and H' to fom HzOlunder acidic conditions. 2.2.2.2 Effect of Temperature
The temperature of the containment in the event of a reactor accident will Vary based on design. The PWR is expected to cool fiom 283OC to 93OC within 20 hours of shutdown
[2 11. A temperature of 80°C is expected in the CANDU containment after a severe
LOCA [22]. The efEect of temperature on iodine volatility has not been confhed. For high iodide concentrations, 0.1 M, Burns et. al. [23] found haie impact due to temperature over the range of 20 - 100°C. Typically, it has been observed that increases in temperature result in a decrease in volatility since hydrolysis of iodine dominates
[10,24,25]. Contrary to this, Lucas [IO] observed a decrease in IPC with an increase in temperature frorn 43OC to 95°C for lV3M Modide solutions. However, he also reported a decrease in the iodine transfened to the gas phase, over the same temperature range.
Decreases in IOa' and Io, (rneasured as I2 + HO1 + 4') and increases in hydrogen peroxide concentrations were found from iodide solutions (6x 1O"M - 1 x 1 o5 M), when temperatures were raised fiom 50400°C [25]. In the same study, the PCreached a minimum between 60-70°C when plotted against temperature. These results suggest that there exists a delicate balance between increased volatility from preferential partitioning at elevated temperatures and decreased Iz production at these temperatures
2.2.2.3 Effect of Total Iodide Concentration
The expected concentration of iodine in the containment under accident conditions depends on the severity of the accident, the amount of hie1 present and the age of the fuel.
It has been estimated, based on the iodine core inventory, that concentrations of iodine released to the containment will not exceed 104 M [Il. Bench scale studies range fiom
10" M - 1o-~ M, while intermediate scale RTF tests assume a concentration of 1O-' M. A decrease Ui volatilization has been observed for lower iodine concentrations [12,13].
Evans [14] also observed, in acidic solutions, iPC to have a strong dependence on iodide concentrations behveen 10" M -10" M. The dependency was not observed between 10" and IO-' M solutions. The measured increases in iodate for lower iodine concentrations
1261 support the theory that I2 hydrOlysis plays a significant role in dilute solutions.
Furthemore, it is expected that at lower concentrations, iodide will cornpete less effectively with other radicals for OH [Il] thereby suppressing its oxidation to molecular iodine.
2.2.2.4 Effect of Dose Rate
Little experimental work has been conducted to observe the effects of dose rate.
Experirnents conducted at AEAT [Il] indicate that dose rate only impacts volatility under acidic conditions. Dose rates used for bench scale tests range f?om 0.15-5 kGy/'hr, while
RTF studies use a dose rate of 2 kGy/hr.
2.2.2.5 Effect of Dissolved Cases
The air above the containment pool is a stem-air mixture with variable arnounts of hydrogen. Hydrogen is emitted fiom reactions of stem with rnetallic surfaces. Shce the
Three Mile Isle accident, interest in hydrogen accumulation in the gas phase has ensued.
The research aims at reducing the potential of an explosion causing a ruphire to the containment structure. Flammable air compositions have been calculated for LOCA conditions using the CONTAIN code. The expected concentrations are 12.4% Hz,7.5%
02,55% stem and 25% Nt [27]. A hydrogen level between 4-9% in an air system is the estimated lower flammability limit [Il. Nitrogen present in the containment can be oxidized forming nitric acid. Nitnc acid decreases the sump water pHypromoting the volatilization of iodine. Furthemore, nitric acid is highly corrosive and may detenorate metal components in the containment.
The accumulation of dissolved oxygen has been shown to suppress volatility [9,11,24].
The oxygen molecule can interact with radiolysis products arecting the formation of 12.
Specifically, oxygen cm compete with hydrogen peroxide for the hydrated electron thereby reducing the formation of hydroxyl radicals. The superoxide ion, Oi,produced fiorn the reaction is a strong reductant for molecular iodine.
Hydrogen peroxide concentrations are kther increased when oxygen and hydrogen together, are present in the water [28]. Tabulated results from Hochanadel [28] have been presented in Table 2.4. The effects of hydrogen peroxide on iodine volatility are discussed in Section 3.2.2.
Table 2.4: Hydrogen Peroxide Concentration from Water Radiolysis 02(Ml a2 (Ml Steady State Hz02 0 5.5 xlo4 4.4~1o4 5.5~10" 7.6 ~10'~7.3~ 10' 2.8~10~ 4.5 XIO-' O i .4~io4 5.0 XIO" O 2.0~10-~
Karasawa et. al. [26] showed that when nitrogen and oxygen are bubbled through an aqueous system and subsequently irradiateci, aqueous nitrate and nitric acid formed at a rate of 0.24 pmoVJ. However Linacre et. al. [29] report that nitrate formation is initiated
in the gas phase alone. Reactions of water radiolysis with rnolecular nitrogen are insignificant. Research in this area is limited but has recently gained renewed interest amongst the iodine community [7].
2.3 Gas Phase Radiolysis
When gas mixtures are irradiated a complex series of reactions between the ions, excites and dissociates take place. Vikis et. al. [30] determined that the volatile iodine formed can be converted to solid iodine oxides in the gas phase, and removed through particulaie filtration. However, nitric acid formed in irradiated moist air may decrease the solution pH thereby increasing iodine volatility. As a result, cwent research aims at understanding reaction mechanisrns occurring in the gas phase.
2.3.1 Status of Models
Few models have been developed to evaluate the impact of gas phase radiolysis on iodine volatility. Sagert [3 11 created a mode1 to determine nitric acid, ozone, hydrogen and hydrogen peroxide yields fiom irradiated moist air. Reactions used in his code were predominantly take from Willis et. al. [32,33] and Busi et. al. [34]. Predicted yields for m03,H202, HI and O3have been summarized in Table 2.5.
Table 2.5: Yields from Model Predictions Species GValue (poVJ) Model Predictions 1 HNo3 0.32
Experimentally, a yield of 0.2 poVJ for nitric acid has been [40,41] confïrmed. Based on this value and assuming a gadliquid volume ratio of 10 and a dose rate of 10 kGy/hr, Sagert [3 11 estirnated the sump water pH to drop to 3.6 in 10 hours and to 2.6 in 100 hour
(equivalently producing 1.1x 10' M HN03).
A preliminary mechanistic model to predict nitrate and ozone concentrations was created
by Evans [35]. This model expanded on the work by Sagert [3 11 to include iodine oxide
formation and potential reactions of ozone with surfaces. The model predicted the nitrate
concentrations reported by Ashrnore and Sims [36], however it did not fair well when
compared against the large scale PHEBUS FPTO nitrate measurements. Evans speculated
that, in larger facilities, nitrate formation might not be solely attributed to the radiolysis
of air. Furthemore, the ndiolytic depletion of nitrate in the aqueous phase needed
evaluation. Since ozone was not detected in the PHEBUS RTF tests, the modelled results
could not be compared against experimental values. Evans suggested that interactions
with surfaces rnight have a significant effect on ozone concentrations. Several
researchers evaluating indoor air quality have determined that relative humidity and
surface material will impact ozone depositional rates [37,3 81.
Funke et. a1.[39] included the elimination of T2(g) hughits oxidation by ozone, using the
IMPAIR code. Kinetic parameters were adopted kom experimental work completed at
Siemens. The empirical model was adapted to include the formation and destruction of
ozone and iodine oxide through radiolysis. Iodine oxide was assumed to form through
the 12/03reaction. To date, a mechanistic mode1 to study al1 lcnown iodine reactions in the gas phase with radiolysis products has not been developed.
2.3.2 Gas Phase Chemistry
Limited literature exists on the chemistry of gas phase radiolysis for the purposes of nuclear reactor safety [40,29,411. Experiments conducted concluded that nitric acid forms in solution, on the irradiation of moist air-water systerns. The studies were performed in the late 50s', when nitric acid was of concern in tems of its corrosive potential. With our current knowledge on the effects of containment water pH on iodine volatility, there has been renewed interest in this area. Results fiom the study by Linacre and Marsh 1291 showed that a linear relationship between NO3- concentrations and gasAiquid volume ratio existed, indicating that gas phase radiolysis played a key role to the formation of NO3-. Reactions between water radiolysis products and nitrogen appeared to have little significance. The subsequent dissolution of the nitrate ion was assurned to fom nitric acid. The effect of oxygen in the gas phase was an increase in nitrate yields while the opposite occurred with hydrogen present. The initial formation of nitrate arose hmthe reaction of nitrogen with water vapour, as opposed to oxygen.
Dissolved oxygen, however had no appreciable impact. in air mixtures containing hydrogen, ammonia was also observed to accumulate. Yields of ammonia did not compensate for the loss of nitrate suggesting that competition kinetics were not occumng. Moist air and hydrogen are expected to be constituents of the containment atmosphere under accident conditions. Therefore, nitric acid and ammonia (although probably in much lower concentrations) may potentially be present in the sump water.
Recent work completed at Harwell laboratories [36] concurs with early work on nitric acid yields in irradiated moist air of approx. 0.2 poVJ. Sirnilar to previous observations, increased production occurred for higher gasAiquid volume ratios and little formation was noted in the aqueous phase. The authors extended the experimental parameters to evaluate the impact of temperature over a range of 25-90 OC and found no effect on the production of nitric acid.
Durhg the early 70s' Willis et. al. [32,33,42,43] provided extensive literature on expected yields nom various irradiated gas systems, including nitmgen, oxygen, water vapour and hydrogen. Dunng the late 80s' and 90s', researchers interested in flue gas treatment through electron beam irradiation examined gas phase radiolysis. These researchea provided insight regarding reactions and rnechanisms involved. Similar to aqueous radiochemistry, the initial yields frorn irradiation dictate the possible reactions that ensue. As a result, the total dose absorbed is a key parameter. Nishimura et. al. [44] concluded that under low doses (10-20 kGy) HN02 and NO2 are formed. At medium doses, NO2 is fomed and regeneration of NO occurs. At high doses (50-60kGy), HN03 and N205are produced. These results shed li@t into the various species formed fiom the interaction of radiolysis products. Recall that ia the earlier work by Linacre et. al. [29] the direct formation of nitric acid in the gas phase was not considered. That is, these authors assumed nitric acid was formed in the aqueous phase once the nitrogen oxides were transferred fkom the gas to the liquid medium.
Research conducted in atmospheric chemistry has proven very useful to the study of iodine behaviour in the gas phase. Interest in iodine stemmed fkom its potential ability to destroy ozone in the atmosphere. The depletion of ozone can arise £iom one of the three mechanisms illustrated in Table 2.6:
Table 2.6: Ozone Destruction Cycles 1 A 1 B 1 c 1 (I+O3+I0+O2)X2 1+03+10+02 I+O~+IO+O~ IO + 10 + 1202 O+10+I+O2 10 + HO2 + HO1 + O2 I2O2+hv+I+I+O2 0+03+02+02(net) HOI+hv+OH+I 203 -+ 302 (net) HOz + Oz + OH + 0: + OZ(net)
While the oxidation of atomic or molecular iodine by ozone is potentially hazardous from an atmospheric point of view, it is a favourable phenomenon for reactor safety. The iodine oxide (IO) once formed is reactive towards HO2, NOt and itself. The second and third patbways lead to iodine sinks forming ION@ and I,O, although, it appears that
IONO*may be short lived [45]. Evidence of I,O, bas been found deposited on walls during experimental mns [46,47], causing difficulties in examining the IO + IO decay process. Loss of 10 to the walls resulting in the formation of ho9has been hypothesized to occur through [47]:
The final I,O, product is non-volatile and will either settle or dissolve in the aqueous phase fomiing iodate (IO3*).
Due to its possible involvement in ozone depletion, the self-reaction of IO bas received
some attention. Researchers have determined that four product pathways cm occur with
varying probabilities. The exact rate expression for each has yet to be established,
although an estimate of the importance of each path is laiown. Still a definitive
understanding on the ultimate fates of the iodine oxide products from the IO + IO reaction is required. As well, Merinvestigation into other iodine reservoirs, such as
IONOz needs attention.
Most recentiy, Funke et. al. [39] studied the impact of various parameters on the decrease of Izw through gas phase radiolysis. An overview of the experimental matrix has been provided in Table 2.7.
Table 2.7: Siemens Experimental Test Matrix Parameter Condition Temparature (OC) 20,80, 130 Dose Rate (kGy5r) 1.9,20 D2In (M) 4~ 1O", 2~ 1O" Air Composition Dry Air Saturated with Stem (20 mg/L at 20°C,200 mg/L at 80°C and 130°C1
Their results suggested that the presence of stearn had no impact on the rate of iodine oxidation fiom radiation. However, from the preceding discussion on the formation of nitrate in the gas phase, the presence of water vapour is essential to initiate the nitrogen kation process. These findings suggest that iodhe reactions with nitrate may be less important than its oxidation by ozone. However, considering that ozone deposition may be more pronounced in the reactor containment, the removal of iodine through ozone oxidation could be lirnited. Increases in temperature reduced the elimination of II, which was explained to have occurred because of lower ozone production. The reduced ozone concentrations counteracted the accelerated rate of the 12/03reaction at elevated
temperatures [30]. Lower initial iodine concentrations resulted in a higher rate of
oxidation. Finally, dose rate did not appear to have a significant impact on iodine
elimination, suggesting that initial ozone concentrations produced were suficient to oxidize the iodine. No other experimental data involving iodine and gas phase radiolysis products are available for cornpanson. 3.0 THEORETICAL CONSIDEMTIONS
3.1 Introduction to Radiation Chemistry
Radiation chemistry is the study of chemical changes arising fiom the absorption of high energy, ionizing radiation. Independent of the source of ionizing radiation, the interaction with the stopping material is the same; either ionic species are formed or atoms and/or molecules become excited [48]. The species formed are called primary products and their yields are normally defmed in terms of G-values (poVP). The subsequent reactions of these primary products dictate the effect of radiation on the material chemistry.
Actuai ionkation occurs as the photon or particle passes through the material, forming tracks of excited and ionized atoms or molecules. The species in the tracks may be concentrated in spurs or blobs. Alternatively, they can be spread through short tracks branching from the main path. The chemical species formed under both conditions are similar. The rate of energy deposition in a material determines whether a spur, blob or short track is formed. The energy loss is rneasured as the linear energy transfer (LET) and varies based on the type of radiation (e.g. alpha (a),beta (fi), gamma (y), x-ray or electron bearn).
3.2 Aqueous Phase Radiolysis
The interaction of water radiolysis products with iodine has made the chemistry of th system difficult to understand. As a result, several separate effect tests have been perfomed to examine the impact of specific parameters on the system. From these, dominant mechanisms occurring have been derived. 3.2.1 Water Radiolysis
The sump water is expected to comprise various species described in Section 2.1.
However water is the dominant substance and will therefore absorb al1 the energy transmitted. Radiolysis of water has been studied extensively [17,18,19,28,49]. Primary yields fiom water radiolysis are sumrnarized in Table 3.1.
Table 3.1: Primary Yields from Water Radioiysis Species GValue (prnol/J) e' 0.275 H 0.063 O , H2 .O45 OH 0.27 Hz02 0.058 E-f 0.27
The major reactions initially involved during water radiolysis are presented below. In the presence of oxygen reactions AL 8 and A23R become important. e-+02+02 [A181 e-+H20+H+OK W3RI
The formation of the superoxide ion (O;) results in increased hydrogen peroxide formation through reaction A34
Of + HO2 +H20+ HrOl+ OH-+ O2 [A341
3.2.2 Aqueous lodine Chemistry
Interaction of iodine with radiolysis products can result in the oxidation of iodide to molecular or atomic iodine. Both products are volatile. The hydroxyl radical initiates iodine oxidation through reaction A52B.
ï+OH+I+OH' [A52B]
Molecular iodine is subsequently formed from the recombination reaction, A54.
1+1+r2 [A541
Atomic iodine can also react with iodide leading to the production of tniodide (b*).
1+ 1' t, 12- [A551 1 + If + 13- w61
12- + 1; + 13- + 1- [A591
If ûiiodide concentrations are hi&, volatility may increase through the reverse of reaction A60. r2+ r f) 13- [A601
The superoxide ion, if present, can reduce 1, 12, Iiand r3-
I~+O;+I~+O~ [A571 Elimination of I2 can occur directly through hydrolysis or its reaction with radiolysis products OH, e and H. The mechanism of Iz hydrolysis to IO3'still remains unresolved.
Experimental work published by Burns et. al. [50] suggest that the impact of hydrolysis is most pronounced during the first 3 minutes for 3x10" M Iz solutions. However,
Truesdale et. al. [5 11 show a much more pronounced depletion of iodine fiom lxlo4 M I2 solutions over a longer time span. The reaction scheme oEered by Truesdale [52] was adopted and was based on a pre-equilibriurn mode1 consisting of the four reactions below: h+HzOtt 120K+K [A62B]
120H' t, HO1 + 1- [A641
HOI o H' + IO' [A651
I2 + I' t, 13- [A601
Subsequent reactions between HOI, IO*and 4OBare rate deterrnining steps to the production of 102'.
HO1 + HO1 + IOi + 2K + 1- [A67A]
120K+ IzOK -t IO? + 2g+ 3 1- [A 1701
120K+ HO1 -t 102' + 2r+ 21' [A 17 11
HOI+O~+IO~+~+I- [A 1721 or + or -+ 102' [AI731 IIOK + or- + IO2*+ H' + 21- [Al 741
Hydrogen peroxide is involved both in the oxidative and reductive processes of Iz. As mentioned previously, oxidation relies on the hydroxyl radical. While the hydroxyl radical is directly produced from water radiolysis, increased concentrations cm result from reactions A 15 and A22, both involving hydrogen peroxide. e'+ Hz02+ OH +OH [A151
H + H202-+ H20 + OH [A221
Reduction of I2 by hydrogen peroxide was most recently reviewed by Bal1 et. al. [53] and a new mechanism was proposed.
GOH- + H202C) 1' + IO2H + HzO [A681
IOIH+ OH- + I' + H20+ 02 [A691
Where IzOK forms fiom reactions A62B, A63 and A64.
I~ + OH--+ OH- ~31
120Kt, HO1 + 1- [A641
33Gas Phase Radiolysis
Yields fiom gas phase radiolysis are largefy dependent on the gas composition. Under reactor accident conditions, mixtures of nitrogen, oxygen, hydrogen and water vapour can be expected. The ability of a component to absorb energy and the abundance of that component will dictate the products formed. A description of the method to evaluate
initial primary yields fkom gas phase radiolysis has been provided. 3.3.1 Primary Yields
The interaction of gamma rays with matter can occur through the photoelectric effect, pair production and the Compton effect. The ability of an atom or molecule to attenuate the gamma ray is called the mass attenuation coefficient [cm21g], defined as:
Mass attenuation coefficients, for relevant molecules, were obtained nom the NIST
XCOMM: photon cross section database (NBSIR 87-3597) and presented in Table 3.2.
Table 3.2: Total Mass Attentuation Coefficients for Gas Species Species Total Mass Attenuation Coefficient (cm21g) Nitrogen 5.51~10'~ Hydrogen 1.9~10" Water 6.12xi0-'
Oxygen 5.52~1 O*' A
Willis and Boyd [33,43] conducted extensive research on the primary products formed fiom the irradiation of several pure gases. Yields, in G units, of primary ionic and neutral excitation processes were published for oxygen, nitrogen, hydrogen and water vapour systems. Based on their data, the G-values of products formed from the irradiation of each gas were determined and are summarized in the tables below. Table 3.4: Primary Yields from Nitrogen Radiolysis Species Gvalue (pmoVJ) Nzi 0.227
Tabl lysis
The rate of production (mous) of each primary radiolysis product could then be determined using equation 3-2:
Where: a[ i ]/at = rate of production of species "i" in mixture
PRG = production rate in the gas phase (rnol~e~~s-'*~~~~moleculé')based on the dose rate (kGy/hr) wj = weight hction of the parent atom from which the species is formed Gi = G-value in pure gas Stream
(Np)j=mass attenuation coefficient of parent atom
L(p/p) = total weighted sum of energy attenuated described by equation 2-2:
Equation 3-2 ensured that variability in gas composition was accounted for in yieids predicted by the model.
3.3.2 Radiation Chemistry of Moist and Dry Air
Due to the low density of gaseous medium, transient ions, radicals and excited molecules produced from irradiation readily diffuse and have longer lifetimes [54]. As a result, there is a higher probability of interaction between the vanous ions, radicals and molecules formed in the gas phase, than in the aquecus phase. Furthemore, since the species are not limited by their particle tracks, LET effects are not significant. Stable primary species formed frorn irndiated air are 0, Oz,H2, OH, H and N. Subsequent reactions of these yield Hr02, HOr, NO and O, (Reactions G8, G9,G56 and G18).
H+02+H02 [GSI o+02+03 [Gg]
OH + OH + Hz02 [G56]
N+02+NO+0 [G18]
Lower collision rates increase the longevity of species in the gas phase. As a result, the
products of the above reactions can react with each other, new species formed or plimary
radiolysis products. The formation of nitric acid was of particular interest in this study. In oxygen-nitrogen mixtures, initial yields of nitmgen oxide (NO) result from reaction G18. However, subsequent oxidation and reduction processes occur through reactions with the stable primary and secondary products, listed below. Ultimately nitnc acid cm fom through reaction G25A.
Reduction
H+N02+NO+OH
H+N03+N02+OH
N+NO+Nî+O
N + NO2 + 2N0 In the presence of water vapour, primary yields from gas phase radiolysis can react with the water leading to the formation of an excited water molecule, ~~0'and eventually the hydroniurn ion, ~30'.
N; + H20+ &O-+ N2 [GU N'+ H~O-+ H~O' +N WI 0; + H20+ H2O0+ O? PI
0' + ~~0-P HzO' + O [W HzO' + H20+ H30-+ OH WI
Reactions of H30-with nitrate ions result in the direct production of NO2 and NO3. H30' + NOz' + H + NOr + H20 WI
~~0'+ NOi* + H + NO, + HzO [G40]
3.3.3 Gas Phase lodine Chemistry
For nuclear reactor safety the oxidation of iodine in the gas phase is favourable, if the iodine species is eventually converted to an aerosol particulate. Oxidation processes are strongly dependent on the reaction of molecular or atornic iodine with O3and 0, expressed by reactions G 106, G108, G109A/B and Gl10.
Oxidation
0+12+10+1 [G 1061
I+Oi + IO+O2 [GlOS
I~+O~+IO+I+O~ [G 1 O~A]
12+03+IO +IO? [G 109B] The fate of the IO forrned determines whether the iodine will be converted to an aerosol or return to one of its original volatile forms.
IO + IO + IOt + I [G118B]
IO2+ IO + 120, (aerosol) [Glll]
10+10+1+1+02 [Gl 18A]
IO + IO + I2 + O7 [G L 18C]
10+NO+NOz+I [GI 171
10 + HO;!+ HO1 + O? [G 124Al
IO+HO;,+OH+I+O2 [G12431
IO+0+O2+I [G1071
3.3.4 Ozone Deposition
Ozone plays a significant role in both nitnc acid formation and iodine oxidation.
Therefore, the potential for ozone to deposit ont0 surfaces needs evaluation. Scientists studying indoor air quality and art deterioration due to air pollutants have researched the deposition of ozone onto surfaces. Nazaroff and Cass [55,56] published mathematical correlations to descnbe the transport of ozone onto surfaces under natural convection.
The continuation of this work by Cano-Ruiz et. al. [37] enabled the development of an expression to determine ozone depositional velocities on diflerent daces. The
matenals of uiterest, based on Evans [35], are stainless steel, dry paint and wet painted
surfaces. In this section the theory governing the expression derived for depositional
velocity by Nazaroff et. al. [55,56] and Cano-Ruiz et. al. [37] is reviewed. The net loss of any pollutant from a room can be described as:
Where : vd = depositional vclocir;. si = surface area of i" surface
For stagnant airflow conditions, the actual mechanism arises from both molecular diffision and surface uptake. The pollutant reaches the surface through molecular diffision and is removed through physico-chemical interactions with the surface. Either process may be rate limiting. Several assumptions have been made to describe the system.
1. There exists a concentration boundary layer of thickness 6, distinguishing the surface
concentration Csfrom the core concentration Ca. This Iayer controls the pollutant
flux to the surface.
2. The core is well mixed.
3. Quasi steady state conditions are assumed, UnpIying the pollutant deposition at any
given surface is constant.
4. Only concentration gradients normal to the surface are of concem.
5. Surfaces are smooth Fick's law of difision is used to represent the transport of the species to the surface, while uptake by the surface is predicted by molecular theory of gases and the concept of reaction probability.
Fick's Law
JD = Flux by diffision
9 = Species molecular diffisivity = 1.82~10-5 m2 s -1 for ozone
C = Species concentration
Surface Uptake
The reaction probability, notated as y, is defined as:
pollutant removal rate Y= (3-61 pollutant collision rate
Interchangeable terms for reaction probability are "sticking coefficient" and "uptake coefficient". The surface uptake flux is then defined as the product of molecular collisions with the wall and the reaction probability.
Where:
Js = net flux of species to surface
Cs= poilutant concentration adjacent to surface
Boltzmann velocity for O3(T=293K) cv> = 3.6x10'cm s-l
indoor depositional velocity can be defined as:
Where J is the total species flux to the surface. Under the quasi-steady state assumption, J
Therefore the depositional velocity can be expressed as the sum of the resistances fiom
mass transfer and surface uptake.
Where :
A theoretical approach was employed to estimate values for kg based on the local Grashof
number. The calculated values were similar to the general gas phase mass transfer
coefficient incorporated in the model, which was obtained from the experimental work
completed by Taghipour [12]. Reaction probabilities were taken fiorn values compiled
by Cano-Ruiz et. a1.[37] have been summarized in Table 3.6. Table 3.6: Reaction Probabilities 1 Material Y 1 Comments 1 Stainless Steel 4.05~1Od Average value from chamber decay exoeriments I I 1 Latex Paint 1 3x10-~ 1 Tube penetration experiments, 9% rel. 1 (dry) humidity Latex Paint 8x 1O" Tube penetration experiments, 9 1% rel. 1 (wet) 1 1 humidity 1
Depositional velocities using reaction probabilities in Table 3.6 and Equation 3-10 were calculated for stainless steel, dry paint, wet painted surfaces, and presented in Table 3.7.
Table 3.7:Calculated Ozone De~ositionalVelocitv - - -- Surface kg(dm/~) k, (dmls) vd (dds) Stainless Stee1 0.12 3.6x105 3x10" Dry Paint O. 12 2.7~10" 2~10" Wet Paint 0.12 7.2~1 5x 10"
3.4 Interfacial NIsiss Transfer
The mode1 developed assumed bulk concentrations of species in each phase and that mass îransfer occurred across a thin interfacial region. Therefore, the flues in both gas and aqueous phases were equal. Henry's law constants were used to correlate the interfacial concentrations, namely:
H(x)= lxq ] i / lxg1 i
Wàere
KIi= concentration of species X in the aqueous phase at the interface (mol/L)
[xJi = concentration of species X in the gas phase at the interface (mon)
The flux of species X (mous) fÎom the gas to aqueous phase is then described as: Similariy, the transfer From aqueous to gas phase is descnbes as:
hr= interfacial surface area (dm')
VLand VG = liquid and gas phase volume, respectively (dm')
Kn = liquid side mass transfer coefficient (dmfs)
KT== gas side mass transfer coefficient (drn/s)
In conforming with a mechanistic approach, where partition coefficients were available, the mass transfer of al1 species was included. 4.0 MODEL DEVELOPMENT
The model was developed in two separate stages, namely the aqueous phase and the gas phase. With the completion of each, a validation process ensued. The final combined model was an amalgamation of both models. The entire model has been provided in
Section A. 1 of Appendix A. A table of al1 reactions included with the corresponding rate constants, activation energy and reference(s) has been provided in Section A.2 of
Appendix A.
4.1 Facsimile Code
The model was developed using the FACSIMLLE computer package created by AEA
Technologies. It is a powerful tool for solving differential equations through numerical methods. The basis of FACSIMILE is the Fortran computer langage and hence programs created using FACSIMILE follow a similar logic as Fortran programs. The typical components include:
1. Variable definition
2. Parameter definition
3. 'Compile initial' routine to initialize parameters andor variables
4. 'Compile General' routine to solve for various parameter values
5. 'Compile Equation' routine to solve differential equations
6. 'Compile Out' to define the desired output variables andor parameter
4.2 Basis for Aqueous Mode1
The aqueous model was founded on the program developed by F. Taghipour during his
PhD thesis [12]. The rate constants were re-evaluated based on an extensive literature review and more reactions were included to expand the mechanistic database.
Approximately 85 new reactions were added, 2 were removed and a few minor changes were made to the kinetic parameters. In addition, temperature dependent rate expressions were included where available. A table summarizing the additions made has been provided in Section A.4 of Appendix A. Mass transfer between phases was included using the equations described in Section 3.4.
While iodine has been the focus of many studies, its behaviour is still not fully undentood. As a result, an explanation of estimated kinetic parameters used in the model has been provided in Appendix B.
43 Basis for Gas Mode1
The gas phase model was elaborated from the version created by G.J.Evans [35]. The reaction set was updated based on an extensive iiterature review and the NIST database.
Namely, approximately 95 new reactioas were added with minor modifications to existing kinetic data. A table surnmarizing the additions made has been provided in
Section A.5 of Appendix A. The model was modified to accommodate temperature variance and account for effects of gas composition on direct radiolysis products. Finally, a basic mechanisrn describing the deposition ofozone ont0 surfaces was included.
Much ambiguity remains regarding the kinetic parameters for gaseous iodine species.
SpecificaiIy, reactions with multiple product pathways are not well defined. For the reactions OH + Iz + products, It + O3+ products, IO + IO + products and IO + HO2 + products an explanation for the choice in kinetic data has been provided in Appendix C. 4.4 Combined Mode1
Although the combined model was simply the joining of the two separate models, an additional component needed inclusion, namely the fate of the aerosol 1203.In the isolated systems, this was not a concern.
The aerosol 1203or I,O,, has been observed expetirnentally. However, insufficient data are available regarding its exact speciation, surface deposition and aqueous dissolution.
Omitîing the removal of 1203in the gas phase resulted in the accumulation of the aerosol, effectively serving as a gaseous iodine sink. The removal rate was estimated based on a half life of 40 min. reported by Ritman et. a1.[57].
The aerosol, having settled in the aqueous medium, was anticipated to undergo hydrolysis eventually regenerating iodide. However, this mechanism remains unexplored. As a result, an overall reaction was speculated with a relatively high rate constant.
Iz03+ HzO + 210< + 2H' k = 1x10~MY
The deposition of 1103on surfaces was not included in the model. 5.0 RESULTS AND DISCUSSION
5.1 Aqueous Model Analysis
The model was validated against available literature results. A limitation associated with the validation process was attempting to simulate experimental conditions with the mode\. In order to accuntely model any experimental apparatus specific parameters are required, for example mass transfer parameters and the system's pH. However, under most circumstances, not al1 the necessary data was published, as they were typically not measured. Therefore, these values were estimated based on literahire assessments and theoretical principles. In the sections to follow the results of several validation attempts along with a description of the assumptions made and a cornparison to the associated expenmental results has been provided.
5.1 .l Water Radiolysis
The first level of validation involved the radiolysis of water. Results published by
Hochanadel [19,28] are popular amongst modellers for validation [18,58]. To mode1 the experimental conditions descnbed, a closed, stagnant aqueous systern at room temperature was assumed. Since mass transfer parameten were not measured, their values were hypothesized based on the results obtained by Taghipour [12]. Taghipour concluded that the stir speed of the solution had no affect on the gas side mass transfer coefficient (KTG),but did affect the aqueous side mass transfer coefficient (KTL). He measured the KTL for two stir speeds, which when plotted allowed for an estimation of
KTL for a stagnant solution, as seen in Figure 5.1. This method clearly assumes a Iinear relationship. Effect of Stir Speed on KTL 4SE-04 -
Stir Speed (rpm)
Figure 5.1: Estimation of Liquid Side Mass Transfer Coefficient
The pH of the solution had not been published by Hochanadel [19] and was assumed to
be neutral by Boyd et. al. [18]. A one molar solution of hydrogen peroxide has a pH < 4.
Since the solution consisted of 2.86~10"M H202,it would have probably been slightly
acidic. Subsequent irradiation would have merdecreased the pH of the system. A
simple experiment was performed to validate the choice in pH. Two solutions of
hydmgen peroxide in distilled water (z 2x10~~M and 14x10~~ M) were prepared. A
volume of 15 rnL of each solution was dispensed into separate 25 mL glass scintillation
vials. Duplicate samples were made. In a fia vid, 15 mL of pure distilled water was
dispensed. The vials were then irradiated for 60 minutes in a Co-60 gamma ce11 at the
University of Toronto at a dose rate of 4.2 kGyh. The pH of each sample was then
measured ushg an Orion pH probe and as suspected, the values hovered around pH 4.
For the pure water condition, the pH was slightly higher, approximateiy 5. The
experimental values were taken fkom the paper by Christensen & Bjerbakke [SE!], but
were checked against the values published by Hochanadel [19]. The points in Figure 5.2
represent experimental values, while the line curves are the modeiled results. Table 5.1 : Hochanadel 1191 Experimental Math for Water Radiolysis I Parameter I I Temeprature (K) 298 pH 4 [H2021o 0 2.8x10-~ Fh10 (Ml 7.8 x104 Dose Rate &Gv/hr) 2.4 Experimental vs. Modeled Results for Selected Water Radiolysis Species
1.OE-03
8.0 E-O4 6.OE-04
4.0 E-OJ
2.0 E-O 4 O.OE+OO O.E+ûO f.E+OJ 2.E4-04 3.E+04 4.E+04 S.E+04 Time (seconds)
Figure 5.2: Radiolysis of Water Containing H202and HI(a exp. -mod.)
In order to mode1 the bubbled expenments conducted by Hochonadel [28], a closed aqueous system with fmed concentrations of Hzand Ozwas assumed. The pH of the system was an essential parameter. The authors neither reported the solution pH nor indicated whether it was buffered at pH 7. From the work completed by Narayanan [16], it was observed that irradiation would Lower the pH of water. Assuming a value of 7 resulted in peroxide concentration predictions much lower than experimentally determined. However, lowering the pH to 5 yielded better results. Adopting a pH of 5 was jusfined based on the observations made in [16] and the simple experiment described earlier. The results at pH 5 have been presented in Figure 5.3. Hydrogen Peroxide Formation from Irradiated Water ai 298 K Dose Rate = 532 kGyhr Experimental vs. Modeled Results
O 20 40 60 80 100 Time (minutes)
Figure 5.3: Hydrogen Peroxide Formation from the Radiolysis of With Dissolved Hd02(a exp. -mod.)
Schwarz [59] published data regarding the effect of dose rate on the formation of hydrogen peroxide in dearated solutions. The system was modelled by assuming a negligible gas volume (V, = lx 10'" dm3)and an aqueous phase without dissolved oxygen. Similar to the previous discussion, a pH of 5 was adopted. The results comparing mode1 and experimental values have been presented in Figure 5.4. Hydrogen Peroxide Concentrations from Water Radiolysis of Dearated Solutions Experimental vs. Modeled Results
100 150 Dose Rate ln(k~y/hr)'R
Figure 5.4: Effect of Dose Rate on H2O2Production from Dearated Solutions (0 erp. -mod.)
Narayanan [16] measured the production of hydrogen peroxide in a stagnant closed system with both aqueous and gas phases present.
Table 5.2: Narayanan [ 61 Experimental Math for H202Formation During Water Radiolysis Parameter Condition Temperature (K) 298 Pressure (atm) 1 KTL (drnk) 4x 10-5 KTG (dm/s) 1.2~10-l Vc (L) 0.0057 VI (LI 0.02 AGL(dm2) 0.057 Dose Rate (kGy1h.r) 6.2
Results for the test matrk under the conditions outlined in Table 5.2, have been presented in Figure 5.5. The steady state concentration measured by Narayanan [16] was 1.2xlo4
M t 0.1~10~M, higher than the predicted concentrations. The initial hear slope observed in Figure 5.5 remains as such until approximately 1.5 kGy, which has equally been observed experimentally by Pastina and LaVerne [20]. In their research they report that the initial production of hydrogen peroxide is 0.088 f 20% prnoUJ. The G-value estimated by Narayanan [16] for hydrogen peroxide formation during water radiolysis was 0.1 poVJ. The mode1 suggested a value of 0.09 poVJ which fell within the error
limits reported by Pastina and La Veme[ZO].
Hydrogen Peroxide Formation During Water Radiolysis Modelied vs. Experimental Results
120E-04 - h .#me. 0. r 1.00, - E cO 8.00E-05 . 2 = 6.00E-05 . U U 2 4.00E-05 - U 2.00E-05 -
. - 0*00E+00 1- - - -- O 2 4 6 8 10 12 14 16 Dose (kGy)
Figure 5.5: Hydrogen Peroxide Formation from Radiolysis of Pure Water
Narayanan [16] also tested the effect of headspace for 104 M iodide solutions under the
following conditions,
i) Bubbling nitrogen to remove oxygen fiom the aqueous phase,
ii) hcreasing the headspace by !4 filling the vials; and
iii) Removing the headspace by completely filling the vials. Results of the nitrogen purged system were inconclusive suggesting the need for Mer
tests. The trends observed for conditions (ii) and (fi) suggested that increasing the headspace decreased the initial peroxide concentration. The model yielded similar results.
At first this appeared erroneous since intuîtively an increased headspace would yield higher concentrations. Extending the irradiation time on the model helped to partially cl&@ these observations, as seen in Figure 5.6. A larger headspace prolonged the accumulation of H2O2however the maximum concentration attained was lower than that obtahed for smaller gas volumes.
Effect of Headspace on Hydrogen Peroxide Formation from 104 M Cs1 Solutions
Dose (kGy)
Figure 5.6: Effect of Headspace on H202Formation from Irradiated IO-' M Iodide Solutions
Repeating the model nin in the absence of iodine yielded the expected trends (Figure 5.7) suggesting that iodine was interfering with the hydrogen peroxide formation. In the presence of iodine, H202production was enhanced particularly when gas volumes were low. Effect of Headspace on Hydrogen Peroxide Formation from Water Radiolysis
O 20 40 60 80 100 Dose (kGy)
Figure 5.7: Effect of Headspace on H202Formation From Water Radiolysis
5.1.2 lodine Volatility
As described in Sections 2.2.2.1-5, various conditions can impact the volatilization of iodhe. Several separate effect tests have been conducted to undentand the effect of various conditions, e.g. pH, on the net volatility of iodine. The model's ability to react to parameter changes was also evaluated using these experiments. The results will be discussed in the sections to follow.
5.1.2.1 Impact of pH and Iodide Concentration
Experimental work completed by Taghipour [12] and Ashmore [Il] was used to validate the model's response to changes in pH and total iodide concentration. 5.1.2.1.1 Flow Experiment
The apparatus used by Taghipour [12] consisted of a staidess steel irradiation vessel with both aqueous and gas phases present. The air was constantly drawn from the vessel and passed through a charcoal tnp to determine the volatilization rate of iodine.
Simultaneously, fresh air replaced the gas phase. Volatilization rates were determined fkom the siope of the accurnuiation of iodinz on the charcoal trap over time. This value is equivalent to the flw of iodine (rnole~.dm~~.s-')undergoing transfer from the water to the gas phase. The model's results correspond to the rate measured after 1000 minutes of irradiation, and were expressed in ternis of iodine atoms as opposed to molecular iodine.
Table 5.3: Taghipour [121 Experimental Matrix for Iodine Volatîlzation Rate Measurements Parameter 1 Condition 1 Temperature (OC) 28 - 30 (used average value of 29) Dose Rate (kGyh) O. 15 KTL (dm/s) 1.5~10~ KTG (Ms) 1x10'~ pH 5-9 [CSI] (MI tx104- 1x10" Gas Volume IV,] (dm3) 0.75 Aqueous Volume [Vil (dm3) 0.25 GasLiquid Interfarial Area (dm2) 1.O3 Gas Flow Rate (dm3/s) 7x 10-~ Air Composition Dry Air (2 1% 02,79% N2)
Initially, volatilization rates predicted by the rnodel under acidic conditions were much higher than those experimentally observed. Through a detailed rate and sensitivity analysis it was determined that increasing the rate constant for reaction A72 (&Oz + I), fkom 3x10~~rnol'~s-~ to 7.5~ 10" U~OT'S-' greatly improved the results. Since the source of this value had not been found, it was speculated that selecting a value of
7.5~10~~/mof's-l was justified. The final outcome was an improvement to the model, illusûated in Figure 5.8. The Gibbs fkee energy for the direct reaction of 1 with Hz02is
10305 Jfmol, hence this reaction is not thermodynamically favoured. Another possibility examined was that the reduction of atomic iodine by H202rnay be indirect, that is through its reaction with HO?'and that this is the actual mechanism for the process represented by reaction A72. However, since no rate constant for this reaction has been reported, it was not included in the model, and since uncertainty existed in the validity of
A72 it was removed.
HO$ + 1 -, 1- + HO? (AG = -56308 J/mol)
Iodine Volatilzation Rates : Experimentai vs. Modeled Results
1.OE-09 Experirnental Results O Mode1 Results No A72 mode1 Results wIA72
Figure 5.8: Iodine Volatilization Rates: Measured and Predicted ResuIts
5.1.2.i.2 Sparging Apparatus Experiment
The aqueous model was altered to imitate the experimental conditions published in
Ashmore et. al [1 Il. These authors used a sparging apparatus in order to measure iodine volatility fiom an hdiated aqueous iodide solution. Since the mass transfer parameters were not published in this article a value of 3x10~dmfs was selected based on the work completed Taghipour [12]. The authors assessed the impact of aitering the sparge gas flow rate and observed no difference in mass transfer. Hence they concluded that the production of volatile iodine was rate limiting. The effect of bubbling air through the solution was an increase in surface area. In order to incorporate this in the model, a value of 10 dm2 for the interfacial area was chosen. Increasing the area to 100 dm' did not appear to have an effect on the results. Ashmore et. al. conducted experiments at different dose rates and temperatures allowing for an assessrnent of these parameters on iodine volatility.
Table 5.4: Ashmore et. al. [Ill Experimental Mathfor Iodine Volatilbation from a
Between pH 5 and 7, the predicted fiaction tmasferred was higher than experimentally observed. The characteristic "S'? shaped cuve for the volatilization of iodine described by Ashmore et. al. [Il] was observed between pH 4.6-5.4. However, uniike the published data, it extended throush to pH 6. Iodine Transferred from Irradiated 10~M Iodide Solutions : Erperimental and Modeled Results
O 20 40 60 80 100 Time (hours)
Figure 5.9: Effect of pH on 12 Volatility at a Low Dose Rate (0.26 kGy/hr). (@ pH 4.6 *H 5 A pH 6 *pH 7 X pH 8) erp. (-) mod.
The model's prediction under the higher dose rate condition better matched those reported by Ashmore et. al. [ 1 11. except at pH 6 where the mode1 yielded an '5"shaped curve with higher volatility than experimentally determined.
Iodine Transferred from Irradiated 10~M Iodide
Selutionx ErgeRntentaLandModeled kwlts -
O 20 40 60 80 100 Time @ours)
Figure 5.10: Effect of pH on I? Volatiüty at a High Dose Rate (1.95 kGyhr). (e pH 4.6 .pH 6 A pH 7 *pH 8) exp., (-) mod. 5.1 .Z.t.3 Effect of pH for High lodine Concentration
From the detailed rate and sensitivity analysis mentioned in Section 5.1.2.1.1 a mechanism describing the fate of iodide under acidic and basic conditions was developed. Under high iodine concentrations, the dominant path for iodine has been show in Figure 5.1 1. The reduction under acidic conditions occurred mainly through the reaction of atornic iociine wirh hydrogen peroxide and molecular iodine with thc superoxide ion.
Figure 5.11: Iodine Oxidation Mechanism for High Iodide Concentration
Under basic conditions, the reduction of molectsiar iodine was further enhanced as hydrolysis played a significant role. In addition, the superoxide ion was favoured under aikaline conditions. in the absence of the 0; + O2reactioa, the volatility at pH 9 was underestimated since the 1; formed was Wediately consumed by the 02-generating 21'.
The formation of triiodide and subsequently molecular iodine was inhibited. 5.1.2.1.4 Effect of pH for Low lodine Concentration When concentrations of iodide were low, the formation of I2 was largely dependent on the recombination of atornic iodine. The pathway has been illustrated in Figure 5.12.
Figure 5.12: Iodine Oxidation Mechanism for Low Iodide Concentrations
Unlike the hi& iodide system, atomic iodine volatilbation was more dominant than that
of molecular iodine. Molecular iodine, once formed was reduced by the superoxide ion.
Under basic conditions, this reduction was enhanced. In order to Merunderstand the
effects of the superoxide ion and the hydrogen peroxide reduction of l2 mechanism, the
latter was removed and the system was tested under low and hi@ iodide concentrations at
pH 5 and 9. In the absence of the reduction of Iz by HzOz,the predicted volatility under
acidic conditions was overestimated. However, in an alkaline medium the mode1
conformed better to experimental data. These results suggested that the reduction of
iodme at low pH was dictated by the peroxide mechanism, while the superoxide ion
dominated under alkaline conditions. However, the kinetics currently in place result in
the reduction of Iz by hydrogen peroxide to create a divergence from the experimental
results at high pH. 5.1.2.2 Impact of Dose Rate
The effect of dose rate was more pronounced for lower pH as concluded by Ashmore etal [Il]. Higher dose rates would generate more hydroxyl radicals and therefore create a more oxidizing environment. However, higher concentrations of reducing species should equally be formed. Results kom the sparging apparatus may not have provided a tme description of the dose rate effect, due to the hi@ rate of mass transfer. in effect, the instantaneous removal of volatile iodine may cornpete with the reduction processes.
Thus, the effect of dose rate for alkaline and acidic solutions was re-evaluated under high and low mass transfer conditions. As seen in Figure 5.13, below = 1.5 kGy/hr the dose rate influenced the net amount of iodine transferred to the gas phase, in an acidic medium
for high mass trans fer rates. When the mass transfer coefficient was decreased to 1x 1O-' dm/s the dose rate effect was observed only below 0.1 kGy/hr. Under aikaline conditions with a high mas transfer coefficient the impact of dose rate was less significant (Figure
5.14). An explanation of the results for the acidic conditions has been provided. The
volatilization rate of iodine is a function of:
a) the oxidation of iodide (RI) and reduction of iodine (R2) in the aqueous
phase and
b) the mass transfer of iodine (R3)to the gas phase. RI =VL * k[OH][I-] 4 GOH* VL * DR[I-] WI
R2 a Ge- *VL* DR[12] 15-21
R3 =AGL*~TL[I~] L5-3 1
Where k = reaction iatc constant (?.l.'s-')
G, = G-value for species x (pmoVJ)
VL= Volume of Aqueous Phase (dm3)
DR = Dose Rate (Jk)
AcL = interfacial Surface Area (dm')
Km = Liquid Side Mass Transfcr Coeficient (Ws)
At steady state
VL * DR[I-]GoH [12 1= tram fer rate =
t. VL *DR*G,- let
When DR is small or kT is large, then 1 »B and the transfer rate is a DR which conforms to the results in Figure 5.13 for kT = 5x 104 dm/s. Conversely when the DR is large or kT is srnaIl 1 B and there is no longer a dose rate dependence. The slight dependency observed below 0.1 kGyhof the low mass transfer condition resulted from an insuficient accumulation of hydrogen peroxide.
Effect of Dose Rate on Volatihation Rate of Iodine at pH 5
E 1E-10 - V KTL = 5x10~dds O Y
Dose Rate (kGy/hr)
Figure 5.13: Effect of Dose Rate Under Various Mass Transfer Conditions
E ffect Dose Rate and pH on Iodine Volatiüzation Rates
1E-13 0.00 1 0.0 1 o. 1 1 10 Dose Rate (kGyhr)
Figure 5.14: Effect of pH on Impact of Dose Rate on Iodine Volatilization Rate Under aigh Mass Transfer Conditions (km = 5x10~dds) 5.1.23 Impact of Temperature
Ashmore et. al. [Il] published data for the transfer of iodine from solution at pH 4.6 and
7, over the temperature range of 25 - 70 OC. The results fiom the acidic medium did not show any particuiar trend. In fact, above 40 OC, temperature did not seem to have any effect. For the pH 7 case, the variability in the results made it difficult to determine whether temperature had an effect. These conditions were modelled and from Figure
5.15, it was obvious that the effect of temperature was less significant at pH 4.6, which
agreed with the observations made by Ashrnore et al. [Il]. At low pH, raising the
temperature by 45 degrees caused a 15% increase in the hction of iodine transferred.
Gorbovitskaya and Tiliks [25] showed a decrease in oxidized aqueous iodine species with
elevated temperatures, suggesting that increased temperatures resulted in a lower net
volatility. For low iodide concentrations a sirnilar trend was predicted by the model,
however the model and experimental results deviated for conditions of higher iodide
concentrations.
Modelled conditions have been summarized in Table 5.5 and results illustrated in Figure
5.16.
The deviation between modelled and experimental results for higher iodide
concentrations may be due, in part, to the assumptions made by these authors concerning
the species being measured. The authors measured L as the sum of I2 + 13' + HO1 by
mWng a concentrated KI solution with the sample, thereby converting the IÎ and HO1 to
IF. The 13- was then analyzed with a W spectrophotometer at 287 nm. The sample was
then combined with a solution of sulfuric acid to subsequently convert the IO3'to 13-.
Again, the Ij- was measured using a W spectrophotometer at 287 m. There was no special analytical tool to ensure that IO3-alone was being measured. In addition, no confirmation was made that the oxidized species were in fact II, 4- and HOI. When modelled, a similar trend was observed for Lxspecies, particularly for lower iodide concentrations.
Gorbovitskaya and Tiliks [25] also presented iodine partition coefficient (IPC) data over a temperature range of 300-400 K for solutions at pH 5. Their results indicated that WC decreases, reaching a minimum beiween 350-360 K after which the PC increased.
Based on these findings, the increased fraction of iodine transferred at elevated temperatures, observed in Figure 5.15, was expected. Poletiko et. al. [7] concluded that the overall effect of temperature neither increases nor decreases the volatility of Iz. There exists a balance behveen the increased reductioo at elevated temperatures and the increased partitioning of molecular and atomic iodine at higher temperatures. This effect was well illustrated by the IPC data published by Gorbovitskaya and Tiliks [25]. Effect of Temperature on Fraction of Iodine Transferred to Gas Phase from irradiated 104 M Iodide Solutions : Modeled Results
Figure 5.15: Effect of Temperature on Iodine Production
Table 5.5:Gorb witskayn et. al. 1251 Experimental Matrix for 1, Formation Parameter 1 Condition 1
KTL (drn/s) 4x 1O' KTG Idm/s) 1 1.2~10"
AGL(dm') 12 I Effect of Temperature on Iox Formation : Experimental vs. Modeled Results - -9.8E-4M (Model) 3.1E-4h.1 (Model)
Figure 5.16: Io, Formation from Irradiated Iodide Solutions ([Il. : A = 7.8~10~M, a= 3.1~10~M, i = 5.85x10-' M) exp. results. (Ref. Table 5.5)
5.1.2.4 Impact of Organics
Reactions involving organics are of significant concem to the containment chemistry but have not been included in the current model. It is expected that organic impurities
Ieached from containment surfaces will increase the volatility of iodine, through the formation of organic iodides. Experimental data ~omIPSN studies involving organics in aqueous, gas and both phases were compared against modelled results in the absence of organics. The experirnental conditions involved the rneasurement of iodine in the gas phase for stagnant airflow conditions. Tests over a larger range of conditions were also perfomed for organics in either the gas or aqueous phase. The test parameters and corresponding results have been summarized in Tables 5.6 and 5.7. Table 5.6: IPSN Erperimental Matrix for Organics in Gas Phase ([r)(hl) l~oseRate (kGyhr) Jp~I~em~erature I~trltirne 1
Table 5.7: IPSN Ex~erimental x for Organics in Aqueous Phase Temnerature CK) hltime
Experimental work completed at AECL was similar to those performed at PSN, however the initial iodide concentration was maintained at 1x10" M for al1 tests. The conditions and results have been summarized in Table 5.8.
A cornparison between al1 the expenmental data for organics fiom both PSN and AECL studies with modelled results has been presented in Figure 5. L 7. Ail studies combined suggest an increase in iodine volatility by two orders of magnitude due to the presence of organics. Although, the data provided was predomiaantiy collected for acidic solutions, the AECL study contained some results at pH 9, which were highlighted in Figure S. 17, and show a Iower enhancement of volatilization. Table 5.8: AECL Experimental Matrix for Organics in Gas, Aqueous and Both Phases Ex~erimentaiResults ------0rgGic Dose Rate pH Duration Temperature Ftrltime (kGy/ hr) (hrs) 313 K 363 K Gas Phase 0.50 5 78 313 & 363 2.8E-06 I 3.2E-06 Aqueous 0.50 5 Phase Both 0.50 5
GasPhase b.!4 ! 5 Aqueous O. 14 5 Phase t--=- t--=- Aqueous
Aqueous
Gas Phase Aqueous 1 Phase
Organic Experiments (IPSN and AECL)
O IPSN Organics in Cas / W IPSN Orgmics in Aquesous /+--- h MCL (Organics in Cas, Aqueous and Combineci)
/ # 0 /
l.OE-09 l.OE-08 1.OE-W l.OE06 1.OE45 1.OW Experimental Results (FiWtime)
Figure 5.17: Modeiled Resuits Compared with AECL and IPSN Organic Experiments 5.1.3 Surnmary of Mode1
The overall performance of the model over a range in pH, dose rate, initial iodide concentration and temperature has been illustrated in Figure 5.18 through a cornpuison of the maximum volatilization rate predicted by the model with results reported by
Taghipour [12] and Ashrnore et. al. [l 11.
Cornparision of Mode1 and Experimental Vola tilizatiou Rates (mous)
Experimental
Figure 5.18: Maximum Transfer Rate of Iodhe from Irradiated Iodide Solutions (Variable pH : ob.26 kGy/hr [il = 104 M, 1.95 yihr m=104 M, A 0.15 = IO-' 0 0.15 = IO-'. M, .lS = kGy/hr [Il M, kGyIhr [q Eil kGy/ür [Il 10~~M, Variable Temperature: + 1.95 kGy/hr (Tj = IO-' M pH 4.6, * 1.95 kCy/hr = IO-' MPHV
In addition, a recent publication by Poletiko et al. [7] offered experimental data f?om
IPSN covering a wide range of experimental conditions, namely initial iodide
concentration, pH, temperature and dose rate. The measured parameter was the hction
of iodine transferred per second after a given amount of the (FTR/time). The IPSN [7]
experiments were comprised of two - compartments, wherein the second cornpartment
contained a basic solution designed to trap gaseous iodine (Figure 5.19). This system 65
was modelled by including additional interfacial transport equations to describe the flux
of iodine into the trap. The KTL was estimated fkom Section 5.1.1 as 4x10" dm/s for
stagnant airflow conditions. The trapping surface area was reported by Hueber et. al.
[60] as 7.854~1O-.' dm'.
Gas Phase Trapping Solution Aqueous Phase
Figure 5.19: Modeiled System for IPSN Experiments
Table 5.9: Geometric Parameters for IPSN Experimental Apparatus Parameter Two Cornpartment Experiments with Experiments Organics
, VG (dm3) o. 1 7.5~1 o'~
, VL (dm3) 5.0~ 10'' 2.5~1oS2 AOL (dm2) 0.08 4.9~1O-'
The conditions exarnined have been sumrnarized in Table 5.10 and the corresponding
results have been presented in Figure 5.20.
ble 5.10: IPSN Two Compartment Experimental Test Matrix Data Point [Il (hl) Dose Rate pH Temperature (K) on Graph (kGyfhr) Ji] 1.OE-03 4.00 4.8 316 12: 1.OE-03 4.00 6.4 316 [3 : 1.OE-03 4.00 8.2 316 [4; 1,OE-04 1.48 5 293 1.OE-O4 1.48 6.4 [5] 293-- - 1.OE-04 1.22 5 363 1.OE-04 1.22 5 403 1.OE-OS 1.48 5 293 Cg] 1.OE-O6 1.48 5 293 Figures 5.18 and 5.20 were useful in assessing the model's performance. Together, these graphs included experimental results From three digerent sources covering a wide range of conditions. The model's predictions corresponded well with the experimental results under al1 conditions examined. Deviances were most pronounced for tests performed at very high temperatures.
Iodine VoIatility from Two Cornparment Experiments
ExpenmentaI Results mime)
Figure 5.20: IPSN Experimental Data vs. Modelled Results
Combining the modelled results for experiments conducted in the presence and absence of organics clearly illustrates that, without organics, the model predicts the behaviour of iodine well. However, the results from this exercise further emphasize the need to incorporate the impact of organics into the model. Modeiied Results for Experiments With and Without Organics 1.OE-O4 - /
1.OE-09 1.OE-08 1 .OE-07 t.OE-06 1.OE-05 1.OE-O4 Experimental Results (FTWtime)
Figure 5.21: Cornparison of Modelled vs. Experimental Results in the Presence and Absence of Organics (FTR/time = Fraction Transferred per Second After a Given Amount of Tirne)
5.2 Cas Mode1 Anrlysis
With Iittle experimental data or analysis of the interaction of air radiolysis products with
iodine, the gas model validation process differed fiom the aqueous. Rather than focusing on experimental comparisons, the model was usehl in determining the factors
influencing iodine behaviour under containment conditions.
5.2.1 Air Radiolysis
Validation of the gas phase relied largely on shidies perfonned on irradiated moist and
dry air. Measurements of ozone and nitric acid were used to compare against modelled
5.2.1.1 Ozone Yield: Theoretical Estimation in Dry Air
Willis et. al. [32] conducted a detailed study on ozone formation in nitrogen-oxygen
mixtures. The dose rate admlliistered was 1.152~10' kGyk delivering 1.2 kGy per electron pulse. The authors examined ozone formation and determined the conditions for maximum ozone production to be:
(1) Complete charge transfer from al1 N~~to Oz:N~+ + Ot + 02++ N2
(2) Neutralization of Ozt yielding O
02f+e+0+0
2O7+e-+0i+O2
o;+Q-+o+ O+02
(3) N reacting partially with O2 and partially with NO disabling the NO to react with O3
(4) O reacting with oxygen to form ozone
From this scheme, an ozone yield was estimated as G(03)= 2G(e) + G(N) + G(0)=
2(0.306) + 0.480 + O. L 24 = 12 16 pmoVJ. The model, however predicted a much lower yield, G(03) = 0.346 pmoVJ. The modelled results reflect a low dose rate scenario, namely 4.45 kGy/hr for a total absorbed dose of 1.2 Gy. The method employed by Willis et. al. [32] to detemine the path for initial ozone formation was adopted and descnbed in
Appendix D. From the mechanism denved the yield was estimated to be 0.32 prnoUJ.
This value was slightly lower than the value of 0.35 pmoVJ predicted by the model in
Figure 5.22 because it does not take into consideration the small contribution of e' through reactions with O;. Ozone Yield from Irradiated Dry Air at 293 K
7.OE-09 -
O 0.01 0.02 0.03 0.04 0.05 0.06 0*07 Dose (kGy)
Figure 5.22: Predicted Ozone Yield from Irradiated Dry Air
5.2.1.2 Ozone Yield: Theoretical Estimation in Moist Air
In the presence of water vapour, the ozone yieid measured after an absorbed dose of 1.2
Gy, was 0.32 pmoVJ. Mer a dose of 19 Gy the production of ozone, under moist air conditions, accelerated at a higher rate than under dry air conditions, illustrated in Figure
5.24. Ozone Yield from Irradiated Moist Air at 293 K
1.4E-08 -
- 0.00 0.02 0.04 0.06 0.08 Dose (kGy)
Figure 5.23: Predicted Ozone Yield from Irradiated Moist Air
Effect of Moisture on Ozone Production Under Ambient Conditions
w E I.2E-O8 - O YQ 1,OE-08 - L - - *DryAir U 8.OE-09 - -Moist Air V, 6.OE-09 - 4.OE-09 -
O 0.02 0.04 0.06 Dose (kGy)
Figure 5.24: Impact of Moisture on Ozone Production: Dry and Saturated Air at 293 K
The eventual increased yield resulted fkom the reaction of ionic precursors with water, namely G2 and G3. N'+H~o+H~~'+NG2
0' + ~~0+ &O- + O G3
The theoretically estimated yield, elaborated in Appendix D, was 0.34 pmoVJ. The lower value of 0.32 pmoVJ predicted by the model resuited fkom the depletion of ozone through NO;.
NO<+03+N03-+O2 G136
5.2.13 Ozone Formation: Experimental Cornparison
The paper published by Funke et. al. [39] provided a simplistic ernpirical mode1 for iodine elimination in the gas phase considering the formation and destruction of ozone.
Using kinetic parameters and rate expressions reported by Funke et. al. [39], a simple
FACSMLE program was developed. Ozone concentrations for air saturated with water at 293 and 353 K, with an initial concentration of gaseous iodine of 4 xlo4 M and a dose rate of 1.9 kGy/hr, were estimated using both models. A summary of the conditions has been presented in Table 5.1 1. The German model predicted much higher concentrations, as seen in Figure 5.25. The trend for the impact of temperature was similar under both rnodels and has been observed experimentally. As a note, the German model was not developed to predict ozone concentrations but to evaluate the effect of ozone on iodine elimination in the gas phase. in contrast, however, ozone concentrations measured by fourth year thesis student, Myra Fong, were much lower than the German model's predictions. Experiments were conducted Ui 240 mL glass vials, containhg 2 mL of water to remove nitrogen oxides and nitric acid hmthe atmosphere. The viais were irradiated in a cobalt 60 gammacell at the University of Toronto. Ozone concentrations were then quantified using an indigo carmine method involving W photometric analysis.
Initial experiments were conducted in the absence of an aqueous phase and yielded much higher apparent ozone concentrations. It was suspected that the indigo cannine, used to measure ozone, was reacting with NO,. A cornparison of the modelled and expenmental results has been illustrated in Figure 5.26 and the conditions used in the mode1 were summarized in Table 5.12.
Table 5.11: Funke et. al. 1391 Experimental Matrix for Ozone Formation Pararneter Condition 12d inhl (bu 4~ 1O& Pressure (atm) 1 Temperature ( K) 293 353 'IIFraction 0.77 0.54 O?Fraction O .20 0.14 H20 Fraction 0.03 0.32
Table 5.12: Ozone Experimental Matrix at U of T Parameter Conditions for Ambient Conditions for Two Air Experiments Phase Experiments Dose Rate (kGy/hr) 4.45 4.45 Temperature (K) 298 298 Pressure (atm) 1 1 N2 Fraction 0.79 0.77 O2Fraction 0.2 1 0.20 H20 Fraction 5x10~ O .O3 ------VG- (dm 1 0.24 0.22 . VL(dm3) 1x10-" 0.02 AGL(dm') 0.05 0.05 Effect of Temperature on Ozone Formation from Irradiated Moist Air Co mparison of Modeled Results
Gerrnan UofT Steady Stnte Ozone Concentrations (ppmv)
Figure 5.25: Predicted Ozone Concentrations from German and U of T Models
Erpected Ozone Concentrations From Irradiated iMoist Air: Experimental vs. ModeUed Results
Time (hours)
Figure 5.26: Ozone Concentrations from Irradiated Moist Air at 298 K (0 exp. - mod.)
The initial yields as predicted by the mode1 closely resembled the experimentd data, however the expenmental steady state concentratioas were three times higher. As mentioned eariier, measured ozone concentrations in the absence of an aqueous phase
were significantly higher. The model was run under ambient air conditions, outlined in
Table 5.12, to examine the potential interference of NOXs'on the measured ozone
production. Adding die model's ozone and dominant NOx concentrations resulted in a
better match behveen modelled and experimental results, illustrated in Figure 5.27. The accumulation of the main NO, species included in the modelled results has been
summarized in Table 5.13.
Ozone Concentrations from Irradiated Ambient Air
-- - - O 5 10 15 20 Time (hours)
Figure 5.27: Ozone Concentrations from Irradiated Ambient Air at 298 K (a exp. - mode1 (O3 + NOX's, - - - - rnodel O3 alone)
Table 5.13: Concentrations of Ozone and Main NOx Species in Gas Phase After 20 Hrs. of Irradiation O3 (ppmv) HN03(pprnv) NO2 (ppmv) N205 (ppmv) N20(pprnv) 0.5 167.9 14.6 3.2 23 -9 5.2.1.4 Nitric Acid Formation
The formation of nitric acid in irndiated moist air was most recently reviewed by
Ashrnore and Sims [64]. Experiments were carried out in a gamma irradiation facility va-g gadliquid volume ratio and temperature. A summary of the conditions used to mode1 this system is presented in Table S.M.
Table 5.14: Ashmore et. al. 1641 Experimental Matrix for HN03 Formation Parameter Condition Dose Rate (kGy/hr) 1.6 v, (dm3) 0.043 vi (dm3) 0.005 AGL(dm2) 0.038 Temperature (K) 298 361 H20Frac 0.03 0.35 O2 Frac 0120 O. 14 Nz Frac 0.77 0.52 Pressure (atm) 1 1.9
The G-value was rstimated to be 0.2 1 prnoVJ at 298 K and 0.18 pmoYJ at 361 K afier an absorbed dose = 1 kGy. Ashmore and Sims [64] reported a yield of 0.22 prnoVJ for nitric acid independent of tempenture. Since the change in yield predicted over this temperature nnge fell within the expenmental error, the difference could not be considered significant.
5.22 lodine Elirnination
The only available data for the elimination of iodine during gas phase radiolysis was published by Funke et. al. [39]. These authors observed the effects of dose rate, moisture content, temperature and iodine concentration. The system was modelled using the conditions presented in Table 5.15. Table 5.15: Funke et. al. 1391 Experimental MaMx for II Elimination - Parameter Condition Dose Rate (kGv/hr) 1.9 and 20
1 Hi0 Frac 1 0.027 1 0.322 1 0.368 1 1 N7 Frac 1 0.769 1 0.536 / 0.50 1 1 07 Frac 1 0.203 1 0.142 1 0.132 1 1 Pressure (atm) II II 1 I I
I1 Eliminntion nt 353 K Iz Eliminatioa at 403 K
-- O 50 100 Dose (Ky) Dose (kGy)
Figure 5.28 (a) and (b): Modelled and Experimental Results for I2 Elimination, Dose Rate = 1.9 kGyIhr ([Iijo : += 2x10~~M, A = 4.0~10~M, fi= 5.9x10-') exp. results -.. m210 :-- - 2~10"~,-- - 4.0~10~M, -= 5.9x10-' M) mod. resuits
5.2.2.1 Mechanism for Iodine Elimination
A detailed rate analysis was perfonned to deteme the mechanism for iodine
elimination. Under high iodine conditions, the formation of 1203was significantly
suppressed; instead iodine was largely converted to HI as illustrated in Figure 5.29.
Although HI can react with OH or NOr, neither occurs at any appreciable rate, resulting in the accumulation of HI. The predominant patbway for 1203formation was the recombination reaction, IO + IO.
Figure 5.29: Mechanism for I2 Elimination in the Gas Phase for High Iodine Concentrations
When iodine concentrations were low, the reaction of HO1 + O2was no longer important and the formation of IO2relied more on the reaction of IO with O3than the recombination of IO. The reaction scheme developed has been illustrated in Figure 5.30. Figure 5.30: Mechanism for I2 Elimination in the Gas Phase for Low Iodine Concentrations
As seen by cornparhg Figures 5.3 1 and 5.28 accounting for the HI concentration resulted in much slower fractional elimination rates at higher iodine concentrations. Calculating an effective ''Ir" concentration using equation 5.1 was used to include the accumulation of HI.
[HI] iz ~ffective=[I~]+~ - f 5-71
However, this method assumes that the l2 concentration measured by Funke et. al. [39] was actually a combination of Iz and HI. The method employed for quantifj4ng iodine was I2 specific and therefore it is unlikely that it included HI concentrations. The similarity between experimental and modelled results on inclusion of the HI concentration suggested that a mechanism by which HI may be converted to IO was missing fiom the model. From the scheme presented in Figure 5.29 the IO would then regenerate Iz through reactions with nitrogen oxides. 1, Eiimination at 403 K
Dose (kCy) Dose (kGy)
Figure 5.3 1 (a) and (b): Modelled and Experimental Results for I2 ELimination Accounting for HI, Dose Rate = 1.9 kGy/hr. ([IIIa : 2x10'~ M, A = 4.0~10" M, i = 5.9x10-') exp. results ([IlIo :-- = 2x1~~M, - - 4.0~10~M, -= 5.9x10-') mode results
5.2.2.2 Effect of Stem
Experirnentally, the authors did not observe an affect of stem on iodine elimination while fiom Figure 5.32 the model suggests that steam may increase the rate of I2 removal.
The dry air composition was modelled assuming a small fhction of water was present
(specifically. 0.05 %). Based on the model, little variability due to stem would be expected for moisture fractions above 0.2%. Hence it is reasonable that no effect of stem was observed expenmentally. Effect of Dose Rate on I2 Elimination : Experimental vs. Modelled Results F. Dry Air '.A Mdst Air
O 50 100 150 Dose (Ky)
Figure 5.32: Experimentnl and Modeiied Results for IIg ELimination During Irradiation of Moist and Dry Air (Expe~mentaidata :A = 20 kGylhr = 1.9 kGyIhr, Modelled Data :- = 1.9 kGy1hr - = 20 kGyIhr)
5.2.23 Effect of Dose Rate
Both modelled and expenmental results concur that the dose rate does not affect the rate of Iî elimination. Although the model predicted a slower elimination for the lower dose rate case than experimentally observed, the experimental error suggests that the deviation may not be statistically significant.
5.2.2.4 Effect of Temperature
The impact of temperature, for higher iodine concentrations, was not well predicted by the model. The elimination rate, at the higher temperature, illustrated in Figures 5.28 (a) and @) was more rapid than expenmentally observed. The fast decline observed at elevated temperatures resulted fiom the HI accumulation discussed earlier. 5.2.2.5 Effect of Ozone
Evans [35] discussed the need to evaluate the potential for ozone to interact with surfaces. No experimental data concerning this issue were available, therefore the kinetic parameters were estimated based on studies pertaining to indoor air quality. A detailed description of the method used has been provided in Section 3.3.4. While ozone showed an afkity to surfaces, no effect was observed on the elimination of iodine. For exampie, the mode1 indicated that deposition with a velocity of 2.6~10~dm/s on a stainless steel surface area of 6.4 dm', would approximately halve the O3concentration (Figure 5.33).
Increasing the deposition rate by an order of magnitude caused a reduction of 85% in the
Oaconcentration. However no impact on the rate of I2 removal occurred for either case.
Reviewing the mechanisms described in Section 5.2.2.1, ozone would not be expected to play a signifiant role on iodine elimination since the reaction of IO + O3is not rate limiting.
Effect of Ozone Deposition on Steel Surface
Time (hours)
Figure 5.33: Effect of Surface Affinity on Ozone Concentrations 5.2.2.6 Effect of Hydrogen
Hydrogen is expected to form from the reactions of stem with metallic surfaces, however no experimental work has been completed to examine the effects of hydrogen on iodine elimination in the gas phase. The conditions modelled have been summ~zed in Table 5.16 and the results presented in Figure 5.34.
Table 5.16: Modelled Matrix for Htimpact Parameter Condition Temperature (K) 353 Pressure (atm) 1 Dose Rate (kGy/hr) 1.9 L, (initial) (M) 5 .9~1oe7 HzFrac O 5x10-' 0.01 0.02 0.05
NzFrac 0.54 0.53 . 0.53 0.52 0.50 OIFrac 0.14 0.14 0.14 0.14 0.13 H20Frac 0.32 0.32 0.32 0.32 0.32 Effect of Hydrogen on Iodioe Fraction
100% -
I? Fraction in Absence of Hydrogen
Figure 5.34: Effect of Various Hydrogen Compositions on Iodine Fraction, Ref. Table 5.15 The impact of hydrogen on decreasing the rate of I2 removal was more pronounced for lower iodine concentrations. For example, by the time when 80% rernoval occurred in the absence of HZ,only 50% was elirninated with 5% Hz(Figure 5.34). When tested under the same conditions with a higher initial I2 concentration, 4x10~M, minimal effect was observed. A cornparison between high and low iodine concentrations on the 50% removal with 5% H2 has been surnmarized in Table 5.17. The hydrogen retards the elimination process by accelenting the cyclic Ioop of iodine regeneration through IO +
Tabte 5.17: Effect of Zz Concentration on Impact of Hz [hlo Percent of II Remaining in Gas Phase 5% H:, 0% Hz IX 1o-~ M 50 49 5.9~10"' M 50 20
53 Combined Mode1 Evaluation
The combined mode1 was evaluated using results fiom bench scale and large scale test
facilities. The expenmental work spanned over a wide range in pH, temperature, dose rate and initial iodide concentration. Therefore, the model's performance was rneasured
against several parameters. Finally, the mode1 was run under conditions prevailing in a
severe reactor accident.
5.3.1 Bench Scale Tests
A description of the two cornpartment PSN experiments has been provided in Section
5.1.3. The amount of 1203expected in the trap was estimated by the ratio of the trapping
surface area to the gasfliquid interfacial area. As seen in Figure 5.35 (point 9), the inclusion of gas phase reactions negatively impacted the results for lowest initial iodine concentration, i.e 104 M. A graph comparing modelled resdts with and without the inclusion gas phase chemistry has been included to illustrate the impact of the combined model.
Iodine Volatiiity from Two Compartment
Experimental Resuits (FTWime)
Figure 5-35: Modelled vs. Experimental Results for IPSN Test Math
Table .IO (page 65): IPSN Two Compartment Experimental Test Matrix Data Point [I-1 (M) Dose Rate pH Temperature (K) on Graph (kGyhr) 111 1.OE-03 4.00 4.8 316 r21 1.OE-03 4.00 6.4 1316 Effect of Gas Phase Chemistry on Iodine Volatilty
1.OE-09 1 .OE-O8 l.OE-07 1,OE-06 1.OE-05 Aqueous Phase Model
Figure 5.36: A Cornparison Between Aqueous and Combined Model Results for the Fractional Removal Rite Calculated for the Two Cornpartment IPSN Experimental Conditions
The dominant species found in the modelled alkaline trap solution were HO1 and IOz. increasing their partition coefficient by up to two orders of magnitude had linle impact on the results. In addition, nising the settling velocity of the aerosol, I2O3,by 50% minimally improved the predicted fraction in the trap.
Similarly a cornparison between aqueous and combined mode1 results for experimental data published by Evans [14] for iodide concentrations ranging from loJ - 10" M and pH fiom 2 - 12 was perîormed. The experiments were carried out in Pyrex flasks under stagnant airflow conditions. A summary of the parameter inputs employed in the mode1
has been presented in Table 5.1 8. ' Table 5.18: Evans [14] Expenmentd Matrix for IPC Parameter Condition 11-1 (MI 1x104, IX~O-~,IXIO-' DH 2- 12 - - -- ~emperature(K) 298 NzFrac 0.769 OzFrac 0.203 HzOFrac 0.027 Pressure (atm) 1 KTL (drnisj 3x 1o*~ KTG (dm/s) 1.2~1 O*' Dose Rate (kGy/hr) 0.25 V, (dm-') 0.05 -VI (dm') 0.0 1 AGL(dm') 0.07 ------
Comparing modelled results for the IPC experiments using the combined mode1 (Figure
5.37) with those using the aqueous model (Figure 5.38) indicate that both performed about equally for acidic conditions. Under alkaline conditions, the combined model underestimated the volatility w hereas the aqueous rnodel overestimated it. For alkaiine
10%M solutions the combined model results were in closer agreement with experimentai data than the aqueous model. Again, under acidic conditions, the inclusion of gas phase chernistry resulted in the model under predicting the volatility for low iodide concentrations. Effect of pH and Iodide Concentration 298 K
Figure 5.37: Predicted IPC fiom Combined Model 18 hours After Irradiation [r]= 1x10~M [( x) exp. -mod.], II*] = lrlo" M [(+) exp. - - - rnod.], [rl = 1xi0-~M [(*) exp. +-++- mod.1
Effect of pH and Iodide Concentration on IPC at 298 K
Figure 5.38: Predicted IPC from Aqueous Model 18 hours After Irradiation FI = 1x10-4 M [( x ) exp. -rnod.], [I-] = 1x10-5 M [(+) exp. - - - mod.], [I-1- 1x10-8 M [(*) exp. +++ mode] Cornparhg the deviance observed under the IPC system for low iodide concentrations suggests that through gas phase reactions Iz is being converted to a fom which partitions more favourably in the aqueous phase. Furthemore, this species, once in the aqueous medium does not adequately contribute to the regeneration of volatile iodine under acidic conditions. However, for the IPSN system, the reduced volatility implies that the partitioning of an iodine specie is insufficient.
Radiolysis products formed in the gas and aqueous phases separately impact the iodine chemistry in each medium. Since the cornbined mode1 includes the radiolysis of both phases, the role of interfacial transfer of oxidizing species was evaluated.
The reaction of 1' + O3depended on the gas phase chemistry, and was limited by the flux of ozone into the aqueous phase. Under the conditions prevailing in the IPC expenrnents, the rate of the reaction was two orders of magnitude lower than that of r + OH and therefore did not have a significant impact on the oxidation of iodide. In the absence of gas phase chernistry the net flux (MS-')of OH and H202was from the aqueous to the gas phase. However, the inclusion of gas phase radiolysis caused a reversal in the transport of both OH and &O2. The absolute value of the flux of OH into the aqueous phase was much Iower than the rate of the reaction OH + r, and as a result did not affect the oxidation of iodide. Based on the mechanisrn illustrated in Figure 5.29 the removal of
OH fiorn the gas phase may reduce the cyclic regeneration of Iz, enhancing its elhination through the formation of ho3and/or ION02. 5.3.2 Large Scale Tests
The Radioiodine Test Facility was designed to examine iodine volatility under various conditions. Results from expenments conducted in a stainless steel vessel at 60°C and a zinc primer coated vessel at 25°C have been used to validate the model.
The test conditions examined in the staidess steel vessel have been summarized in Table
5.19. Both phases were considered 'well mixed' since they were continually recirculated during expenmentation. Wren et. al. [61] selected a value for KTL of 7x10~drnls for mixing and non-condensing conditions. Taghpour [12] reported a value of 4x10~dm/s for solutions stirred at a rate of z JO0 rpm. Based on these, a value of 5x10~dm/s was selected for the model. Kupfenchmidt et. al. [15] report a recovery of 28% of the initial iodine on the gas phase surfaces. Therefore, a loss of both molecular and atomic iodine to adjacent gas phase surfaces was included in the model. A deposition rate of 0.01 dm/s was selected based on the findings of Nugraha [62]. Table 5.19: RTF Stainless Steel Experimental Matrix Parameter Condition , u-I (MI 1~10-~ Temperature (K) 333 1 Pressure (atm) 11 I . NF7 rac 0.34 1 OIFrac 0.09 1 H20Frac 0.568 Depositional Velocity of IZs and I, on Stainless 0.0 I
KTL (dm/s) 5x10" KTG (dm/s) 1.2~1O-1 V, (dm3) 313 VI (dm3)- 27
Dose Rate (kGy/hr) 2 Gas Phase Steel Surface Area (dm') 220
RTF Experiments in Stainless Steel Vesse1 at 333 K
RTF Experiment 1 Aqueous Model 3 ------.--,l -12 - I\ t Combined Model
-13 , -. - ---- .- - O 50 100 150 200 250 300 Time (hours)
Figure 5.39: Totri Gaseous Iodine Concentration
As seen in Figure 5.39, the pH effect observed experimentaily was well predicted by both models. In the absence of gas phase chemistry the deviance between experimental and modelled results, at low pH, was more pronounced. Whereas, for the iPC experiments there was little clifference between the aqueous and combined mode1 resultç at pH 5 for
10-~M solutions. Furthemore, the predicted IPC for pH 9, IO-' M (Figure 5.38) was approximately 10'. Based on this, the predicted concentration of total 1, under the RTF conditions using the aqueous model was expected to be 10''~M. However, fiorn Figure
5.39 the predicted volatility was much lower. The apparent discrepancy, for both cases, may be attributed to the adsorption of gaseous molecular and atomic iodine to the vesse1 surface, which was included in the rnodelled RTF system.
The combined model underestimated the volatility, by an order of magnitude, when compared to the experimental data. Conversely, according to points 6 and 7 in Figure
5.35, which correspond to experiments at elevated ternperatures, the mode1 over estimated the volatility. Dominant gaseous species in the modelled RTF experiments were HO1 > I2 > MO2 > 120i,whereas in the alkaline trap experiments the prevailing species were MOz >HO1 > IOz > II. The partitionkg of HO1 rnay have caused the discrepancy in the results.
Kupferschmidt et. al. [15] reported the build up of hydrogen in the gas phase, resulting in the need to periodicaily vent the systern to maintain concentrations of H2below flammability. The model was used to evaluate the effect of hydrogen gas under these experimental conditions. In addition, the impact of ozone deposition ont0 the gas daceswas investigated. Systems with an initial hydrogen content mnging nom 1 - 5% resulted in a minimal change in the total gas phase concentration. Ozone deposition at a velocity as high as 2. Sx 1O" Mshad no impact on the volatility of iodine.
Experiments conducted in a zinc-primer-coated vesse1 at the RTF indicated that iodine had an affinity for these surfaces, particularly in the aqueous phase [22]. Therefore, in order to mode1 this system. a deposition of molecular and atomic iodine in the aqueous phase was estimated based on the experimental results. The parameten employed to simulate the expenment have been summarized in Table 5.20.
Table 5.20: RTF Zinc-Primer Coated ExperimentaI Matrix [ Parameter 1 Condition 1 Dose Rate (kGy/hr) 2 II-1(Ml 1x10" 298
Pressure (atm) 1 Iodine Depositional Velocity on Zinc Primer (drnk) 0.003 KTL (dds) 5x 1O-' KTG (dm/s) 1.2~10'~ v, (dm3) 315 VI (dm3) 25 AGL(dm') 37 Aqueous Zinc Primer-Coated Surface Area (dm2) 52
A cornparison of the experimental and modelled results afier 100 hours of irradiation has been presented in Figure 5.40. Here, the predicted values closely resemble the experimental data. Predicted and Measured Total Gaseous and Aqueous Iodine from Zinc-Primer RTF Experiments
Time (hours)
Figure 5.40: Experimentrl and Modeiled Results for RTF Zinc-Primer Coated Vesse1 Experiment ( Aqueous Concentration: .exp. - mod. Gaseous Concentration: A exp. -mod.)
5.3.3 Accident Scenario Condition
The motivation for the development of this code was to assist in predicting the fate of iodine under accident conditions. Accident scenarios will Vary between reactors, largely depending on the specific failure(s) that occur. From a safety perspective the volatility of iodine should be estimated for the worst-case scenario, iiamely a large Ioss of coolant accident (LOCA). A large LOCA occurs because of a guillotine rupture to the main heat transpoa system (HTS). During this tirne, the coolant spills into the reactor building
(containment) and the emergency core cooling system (ECCS)is activated to prevent mercore degradation. However, for CANDU reactors, failure of the ECCS to respond is estimated to increase the release of 1- 13 1 fiom 0.37% to up to = 13% of the total core inventory. Both conditions have been examined with the model, recognizing that the failure of the ECCS is the less credible situation. The data to model this systern was obtained from Ontario Power Genention safety reports and design manuals for the
CANDU reactos at Pickering Stations A and B [63,64,65,66]. However, feahires unique to this power plant were not included, namely the vacuum building and associated dowsing system. Instead, the modelled system was tailored to reflect a genenc case with the purpose of estimating the expected volatility. Values for parameters used have been summarized in Table 5.3 1. For a large LOCA with ECCS available, hydrogen levels are not expected to exceed 1 kmol, corresponding to 0.5% of the gas composition. A concentration of 3% was assumed for the analysis where ECCS was assumed to be unavailable.
Table 5.21 : Accident Scenario Test Matrix - - Parameter Condition Condition ECCS Unavaiiable ECCS Avaüabie Dose Rate (kGyhr) 1.O [79] 1.O [79] 1 ~em~eranire(K) 1313 1313 Pressure (atm) 1 1 , v, (dm3) 5.1~10' 5.0 1x106 VI (dm3) 1.5xio5 9.33~10' &L (dm2) 1.4~10' 1.4~10' pH 8.5 and 6.5 8.5 and 6.5
, Mo(Ml 2.5x104 1.1~10~ KTL (drn/s) 5x10~ 5x10~ KTG (dm/s) 1.2~10-1 1.2~1O" N2Frac 0.553 0.573 OzFrac O, 147 O. 152 H20Frac 0.270 0.270 H2Frac 0.030 0.005
The model, under the conditions described in Table 5.21, was used to calculate the fiaction of total iodine tnnsferred to the gas phase. Independent of the availability of the
ECCS, the inclusion of gas phase chemistry resulted in a lower net volatility, obsenied in Figure 5.4 1. For al1 systems tested the deposition of iodine onto surfaces was not accounted for.
Effect of Gas Phase Chemistry on Gaseous Iodine Fraction
- - l.E-O2 - U 1.E-03 - = lr O L r-t<- L.E-04. 2 2 1.E-05- i( 1.E-06 - ECCS Available CCS Unavailable
Figure 5.11: Predicted Fraction Total Gaseous Iodine 24 Hrs. After Large LOCA Accident for CAXDU System with the Cas Phase Chemistry ON or OFF in neglect of gas phase reactions, molecular iodine was predicted to be the dominant gaseous iodine species. However, with gas phase chemistry occurling, Iz was eliminated and MOt was the main gaseous species of iodine. Since the partitioning of this specie was 100 times greater in the aqueous phase than 4, the combined mode1 predicted a lower volatility. Table 5.22: Partitioning of Iodine Under CANDU Accident Scenario: Effect of Gas Phase Chemistry Gas Phase pH Total Aqueous Total Gaseous WC Chemistry Iodhe Iodine ECCS Unavailable ON 8.5 2.50~10~ 1.96~10-13 1.28~10' OFF 8.5 2.49~10" 2.04~10" 1.22~1 O' ON 6.5 2.50~10~ 3.3 1x1~" 7.56~10' OFF 6.5 2.42~10~ 2.39~10"~ ~01xl0'' ECCS Available ON 8.5 1.10~10'~ 1.95~1 5.65~10~ OFF 8.5 l.loxl~~ 5.46~1 0'12 7.0 1x ld ON 6.5 1.10~10~ 2.46~10*'~ 4.47~1 0' OFF 6.5 1.10~10'~ 7.65~10-l2 1 .43x103
In Section 5.2.2.6, hydrogen was observed to retard the elirnination of I2 for systems with lower iodine concentrations. When tested under the conditions investigated using the
RTF, hydrogen had no impact on the net volatility. However, for accident scenario modelling the effect of Iiydrogen was observed. Namely, a higher volatility resulted with increased levels of hydrogen. The concentration of iodine in the gas phase in the presence of 3?6 hydrogen was 1.J times higher than that for 0% hydrogen
Analysing reactions occumng in the gas phase suggested that the direct reaction of ozone with iodine was not a significant event in the elirnination of iodine. In order to verify this statement, the effect of ozone deposition was investigated under the accident scenario involving a failed ECCS. The containment wall was assumed to comprise wet paint, as the deposition of ozone would be highest under these conditions. As established earlier, no impact on the concentration of gaseous iodine species was observed.
Typically, rnodellers have used higher initial iodide concentrations when evaluating accident sequences [84,85,86,87] as core meltdown was usually assumed. Petit et. a1.[84] and Herrero and Verduras [SI,provided the conditions prevailing during a severe
accident in a 1300 Mwe French PWR and 2785 MWt (~900MWe)Spanish PWR
respectively. For both accident scenarios, failure of the ECCS was expected to occur.
These have been surnmarized in Tables 5.23 and 5.24. The air composition was not
descnbed by Petit et. al. [Y4],therefore two cases were examined for the French PWR:
c) 0% Hydrogen content in containment atmosphere,
d) 3% Hydrogen content in containment atmosphere.
The containment for the Spanish NPP was simplified for modelling purposes, and
dimensions wrre estimated based on the configuration descnbed by Herrero and Verdura WI*
Table 5.23: Accident Sequence Conditions for French PWR Parameter Condition VG (dm3) 7.0ix108
, VL(dm3) 2.65~1o5
, AGL (dm2) s 1.16~10' pH 6.4 Dose Rate (kGy/hr) 1.O (assumed) 1, 1, (initial) (M) 4.3~1O-' [Izln(initial) ( M) 4.3~1om9 Temperature (K) 375 Pressure (atm) 2.33 (calculated from water vapour pressure) Case 1 Case 2 N2Frac 0.43 0.40 OzFrac 0.1 1 0.1 1 H20hc 0.46 0.46
H2Frac O 0.03 A Table 5.24: Accident Sequence Conditions for PWR in Spain 1 Parameter 1 Condition VG (dm3) 5.5~10" VL(dm3) 4.3~1os &L (dm') 1.3~10' 8 and 5
Leak Rate (s") 1.2x10-' Dose Rate (kGy/hr) 1.O (assumed) Temperature (KI 375 (assumed) Pressure (atm) 2.3 (calculated from water vapour pressure) N7Frac 0.43
The empirical model employed by Petit et. al. [84] was based on several assumptions to
descnbe the fate of iodine. Speci fically the model considered:
Release of iodine into the containment partly as a water-soluble aerosol and partly
in the gaseous fom.
Oxidation of aqueous iodide to molecular iodine and the subsequent interfacial
transfer of I1 betwcen aqueous and gas phases
Formation of A@ in the aqueous medium
Formation of orpic iodine through interactions of iodine with painted surfaces
in the gas phase and reactions of iodine with methane in the gas phase
Adsorption of iodine on concrete and painted surfaces.
Gas phase interactions and reactions were deemed to ultimately dictate iodine behaviour.
The model considered only two gaseous iodine species, T2 and CH& To compare the
models the I2 concentration reported by Petit et. al. [84] was multiplied by two to give a
value equivalent to the total gaseous iodine concentration predicted by the U of T model.
Both rnodels suggested a concentration of =l0-'* M couid be expected in the gas phase over the long terni. Although the concentration profile predicted by the French code differed, observed in Figure 5.42. hitially the concentration of ioduie rises kom the
formation of volatile iodine through aqueous radiolysis. However, the subsequent gas phase reactions results in the conversion of gaseous I2 and 1 to various iodine species,
specifically HO 1, INOZ, IOz and 120j Once they have sufficiently accumulated, these
species partition favourably in the aqueous phase, except the aerosol, 1203,which
deposits into the water medium. As a result a drop in the total concentration was
observed over time.
Predicted Iz Concentration Profde
5 1.0E-O8 -U of T Model f O - - -French Model "L 1.OE-09 C, t
------1.OE-13 - O 20000 40000 60000 80000 100000 Time (seconds)
Figure 5.42: .4 Cornparison of Predicted I2 Concentrations as a Function of Time: French Model vs. U of T Model. The results presented in Figure 5.41 correspond to the conditions outlined in Table 5.22 for Case 1 with gas phase chernistry included.
The effects of gas phase ndiolysis and of hydrogen were also examined. As illustrated in
Figure 5.43, predicted results Born the combined mode1 for case 2 (containhg 3% Hz)
were two orders of magnitude higher. The impact of hydrogen was only observed with
the combined mode1 indicating that small arnounts of dissolved hydrogen had a negligible effect on the aqueous phase chemistry. Neglecting gas phase chernistry may result in a significant underestirnation of iodine volatility. Results from modelling the RTF experiments conducted in a stainless steel vesse1 indicated that a hydrogen content as high as 5% did not affect the gaseous iodine concentration. Simulations of a CANDU reactor accident with 3% Hzin the containment atmosphere resulted in a 40% increase in the gas phase concentration of iodine. Finally, the predicted volatility under the French
PWR accident condition was greatly affected by the hydrogen content. Clearly the effects of hydrogen were rnagnified by a specific condition that prevailed the greatest in the PWR and least in the RTF stainless steel expenments. It was suspected that the gadliquid volume ratio was the influencing parameter, specifically the higher the ratio the greater the impact of hydrogen.
Impact of Hydrogen on Total Gaseous Iodine (12)
1.OE-07 : 0% Hz (Case 1) 3% Hz (Case 2)
Cas Phase ON Gas Phase OFF
Figure 5.43: Impact of Hydrogen on Net Iz Volatility 24 Hrs. After Irradiation
A test was performed wherein the gas phase volume was varied, maintainhg the aqueous phase volume and interfacial surface area at the values specified in Table 5.23. The results have been presented in Figure 5.44. The impact of hydrogen was most pronounced when the gas volume was 3 orden of magnitude higher than the aqueous
Effect of Gas Volume on Impact of H2
Cas Phase Volume (dm3)
Figure 5.44: Effect of Gas Volume and H2Concentration on Iodine Volatility After 24 hrs of Irradiation
Herrero and Verduras [85] and Dutton et. al. [87] both evaluated the impact of iodine chernistry on the predicted release of volatile iodine by MAAP (a mode1 used for level II probabilistic safety assessments). MAAP did not consider different iodine species; instead it assumed that iodine remained in the Cs1 form and was modeied as an aerosol.
Herrero and Verduras [85] compared the estimated release of iodine from both IODE and
MAAP codes. Their objective was to determine whether the inclusion of iodine chernistry would greatly impact the MAAP results. A 1% vol. leak flow was assumed to occur upon containment failure (specifically 48 hours after the accident sequence began assuming ECCS was unavailable and the operators did not mitigate the situation) [85]. Results fiom both studies suggested that gaseous species (other than aerosols) were a small fraction of the total release, i.e. QO%. The combined mode1 however, predicted higher releases than estimated by IODE,illustrated in Figure 5.45. Thus, the conclusion drawn ftom the previous studies [85,87] regarding the contribution of iodine chemistry to the predicted releases needs re-evaluation. With the inclusion of hydrogen and organics, it is expected that the role of gaseous iodine chemistry will be even higher than the aerosol predictions by MAAP.
Predicted Release of Iodine Under Severe Reactor Accident
\ IODE (Spain) UofT
Figure 5.45: Code Cornparison of Predicted Net Release of Iodine at t= 60000s
Since the accident scenarios examined covered a range in initial iodide concentrations, the fractions transferred were compared for al1 three sequences (Tables 5.21,5.23 and
5.24). The much higher volatility predicted for the IO-' M condition was examined and determined to have resulted from a shifl in the main gaseous species present. Effect of Intial Iodide Concentration on Net Volatility
Time (hours)
Figure 5.46: Comparison of Iodine Fraction Transferred Under al1 Accident Scenarios Examined Using the U of T Combined Mode1 (a: French PWR, b: Spanish PWR, c: CANDU LOECI)
For iodide concentrations I10'' M, INOz was most abundant. On the other hand, for iodide concentrations > IO-' M; 12, IO?and INO, equally dorninated. Sincr I2 is more volatile than INOZ the net volatility for higher initial iodide concentrations was significantly greater. In addition, the predicted speciation under high iodide concentrations was strongly affected by the settling rate of the aerosol, Ir03. A sensitivity study was performed, increasing and decreasing the estimated settling rate by one order of magnitude. The results have been summaiized in Table 5.25. Illustrated in Figure
5.47, decreasing the settling rate below 10 4 s-1 resulted in an increase in volatility by
100% at t = 24 hours. In addition, the maximum volatility predicted was 30% higher at the lowest settling rate (Figure 5.47). Table 5.25: Sensitivity Analysis of Aerosol Settling Rate on Gas Phase Iodine Speciation AerosolSettling Iz % HI % HO1 % IO2% Iz03 % IN02 Oh IONO* % Rate (s-') 3x1~' 23 1 8 28 1 36 3 3x10~ 2 1 I 8 25 9 33 3 70.6 O O 0.7 97 0.9 O
Effect of 120, Settling Rate on Total Gaseous Iodine Concentration (IJ
-Settiing Rate = 3110-' sS' ...... Settling Rate = 3r10"s" P\ \ -,,Settling Rnte = 3x 10'' s" I \
Time (hours)
Figure 5.47: Effect of Iz03Aerosol Settling Rate on Total Gaseous Atomic Iodine for Conditions Outiined in Table 5.22
It has been well established that the aqueous iodide inventory influences iodine volatility.
Namely, increased concentrations result in higher volatility. This has been observed
independent of gas phase chemistry. However, the difference in the iodine fraction
transferred between the 1O-' and 1OS5M versus the 10-5M and 10" M was largeiy due to
the role of gas phase chemistry. Reactions occumng in the gas phase ultimately dictated
the main iodine species present. In such a manner, the predicted volatility became IargeIy
a function of the chemistry occurring in both phases. The seventy of an accident and the
type of reactor will affect the hction of iodine released f?om the core to the sump water.
Evaporation of the sump water may Mher Încrease the aqueous iodine concentration. Finally, elevated temperatures will increase hydrogen levels within the containment
atmosphere through the reaction of water with metallic surfaces at high temperatures.
The influence of these factors on iodine volatility was revealed only through the
combined mode!.
5.4 Sensitivity Analysis
A potential source of error associated with modeling is the selection of kinetic
parameten. Key reactions pertaining to the oxidation and reduction of iodine in the
aqueous phase were determined and illustrated in Figures 5.1 1 and 5.12. Any
discrepancies or errors associated with these reactions, based on literature, were
incorporated to test the sensitivity of the modeled results. The conditions employed
correspond to the experimental apparatus used by Taghipour [12] and were outlined in
Table 5.3. For each modification made, the mode1 was run to determine the impact on
the results. A surnrnary of the changes made has been provided in Table 5.26.
Table 5.26: Rate Constant Modification to Test Sensitivity of Aqueous Mode1 Reaction Original Rate Modified Rate Reference for Constant (M-'s") Constant (MIS-') Modified Value ï +OH + I + OH. 7x10' 1.2~1 0'O il41 1; 1; + 1 + 13* 4.6~1 0' 8.4~10' [841 1; + I?. -, G- + 1- 2.5x109 4.5~10' [881 I+I+I~ 1.5~10~~ Lower 8x10~ [891 1 Uooer 2.4~10'~ l I XL 1 1+ 0; -+ I* + O2 3x10'~ 1 3x10' 1 Both speculated Sensitivity of Aqueous Model to Modification in Specific Rate Constants
Figure 5.48: Sensitivity Analysis of Aqueous Model to Alterations in Specific Rate Constants, Reference Table 5.3 for Conditions
Only minor fluctuations were observed fiom the modifications made as illustrated in
Figure 5.48. The kinetics of the hydrolysis of I2 was not altered due to the arnbiguity associated with its reaction mechanism. It is recornrnended that merinvestigation regarding I2 hydrolysis be conducted to test the model's sensitivity to the kinetics of this reac tion.
Since Iittle impact was observed to changes in the kinetics of the aqueous model the effect of gas phase kinetics was investigated using the combined model. The conditions applicable to the RTF stainless steel experiments were employed, which were summanzed in Table 5.19. Again, the kinetics of the key reactions outlined in Figures
5.29 and 5.30 were altered based on error lirnits reported in literature. A summary of the modifications made is provided in Table 5.27.
Table 5.27: Rate Constant Modification to Test Sensiti.vity of Combined Mode1 Reaction Ori inal Rate Constant Modified Rate Constant (Mk s-') (AT's-l) Upper 5.17~1~~~e'-~~~ I Lower 2.77~10il e (-2Ol-r) 1 Upper 1.2~1OS Lower 6x 1o8 Uooer 1.7~10 ' 1
The alterations made minimally affected the results. The greatest impact observed was
due to the change in the rate constant for G119 (Iz + NOi + IONOl + 1 ) and has been
presented in Figure 5.49. Sensitivity of Combined Model to Rate Constant for Reaction I2 + NO3
1.OE-09 Original Mode1 - - *KG119=6E8 5 LOE-10 -; + KG119 = 1.2E9
-èO 1.OE-11 ! =m pH9 Y pH9 O CI 1.OE-12 ;
Figure 5.49: Sensitivity of Combined Modelled Results to Kinetics of I2 + NO3 Under Conditions Applicable to RTF Stainless Steel Experirnents, Ref. Table 5.18
The sensitivity study was limited by the literature available concerning reaction rate constants ofiodine species in the gas phase. Often only a single publication reporting a measured rate constant for a reaction was found. Further experimental research as well as an extensive sensitivity analysis of the reactions included in the mode1 is required to properly determine the errors associated with the model's predictions. 6.0 CONCLUSIONS
Several international initiatives have been taken to simulate iodine behaviour in nuclear reactor containment. Thus far, modelles have focused primarily on aqueous phase chemistry in efforts to estimate volatility fiom irradiated iodide solutions. The potential impact of gas phase chernistry on iodine volatility has gained a renewed interest amongst the iodine research comrnunity. The principal achievement of this research project was the developrnent of the first combined mechanistic model to include radiation chemistry in both aqueous and gas phases, interfacial mass transfer and temperature variance. The model for each phase was fint validated against available experirnental data, before the combined model was tested. The conclusions drawn from this project summarize both the performance and knowledge gained fiom the model.
6.1 Aqueous Mode1 The aqueous component of the mode1 successfully predicted hydrogen peroxide concentrations from water radiolysis. Both a decrease in solution pH and increase in headspace volume maximized the production of hydrogen peroxide.
Under acidic conditions and iodide concentrations M, the reaction of hydrogen peroxide with atomic iodide was observed to greatly impact iodine volatilization rates.
However, the kinetics of this reaction still requires experirnental verification. Predicted volatilization rates closely matched vanous experirnental results over the following range of conditions:
a) Iodide concentrations: 1O"- 1o4 M
b) pH: 5-9
c) Dose Rate: 0.2 - 2 kGy/hr, and
d) Temperature: 298 - 403 K (25 OC - 120°C).
The oxidation of iodide to molecular andor atomic iodine was confirmed to occur primarily through its reaction with the hydroxyl radical. For higher iodide concentrations molecular iodine dominated, whiie for lower iodide concentrations atomic iodine contributed most to the volatility. Hydrogen peroxide and the superoxide ion were responsible for the reduction of molecular iodine. Increased concentrations of 02'under alkaline conditions explained the lowered volatility observed.
Dose rates below 1.5 kGy/hr were observed to affect iodine volatility at pH 5 under high mass transfer conditions. For low mass transfer conditions, the dose rate effect observed below 0.1 kGyhcould be attributed to insufficient hydrogen peroxide accumulation. A minimal dose rate impact was observed for basic solutions.
Temperature had Little efEect at pH 5, but appeared to increase volatility at pH 9.
Expenmental data at elevated temperatures was less abundant and somewhat contradicting. The mode1 conformed to the theory proposed by Gorbovistakaya et. al. [25], suggesting that volatility increases with temperature untilr 363 K after which the volatility decreases.
Cornparisons between modelled results in the absence of organic reactions with experiments containing painted coupons suggested that the organic material increased
iodine volatility by as much as two orden of magnitude.
6.2 Gas Modef
Little expenmental data was avai lable regarding gas phase radiolysis under the condition
relevant to accident scenario analysis.
From a theoretical approach. initial ozone yieids were estimated as 0.32 and 0.34 pmoVJ
under dry and moist air conditions, respectively. Concentrations of ozone significantly
reduced with an increase in temperature and ozone showed a strong afinity to surfaces.
However, unlike original ly anticipated, ozone did not have a large impact on the
oxidation of iodine to 1203.
Predicted yields of nitric acid were = 0.2 poYJ and independent of temperature. Both
findings conesponded with experirnental results.
The elimination rates of gaseous iodine at low concentrations compared well with
experimental data obtained at Siemens, by Funke et. al. [39]. Formation of the aerosol
GOj was suppressed by the regeneration of I2 through reactions with nitrogen oxide. In 112 the absence of an aqueous phase, hydrogen iodide served as an iodine sink accounting for the deviance between predicted and expected results at high iodine concentrations.
6.3 Combined Mode1
The fate of gaseous molecular or atomic iodine depended on the solution pH, initial iodide concentration and temperature of the system. The most dominant gaseous species were HOI, INOz and IO?. The kinetics of 10 played a significant role in the formation of
INOZand IOz and therefore had a direct impact on the net volatility. A key recomrnendaiion derived was the need to explore IO reactions, as much ambiguity surrounds the fate of this species. The presence of hydrogen in the gas phase was found to hindet the elimination of iodine resulting in high concentrations of total gaseous iodine. However, the impact of hydrogen was partially dependent on the gadliquid volume ratio. 7.0 RECOMMENDATIONS
The following is a Iist of suggested recomrnendations for future work.
The existence of a reaction or mechanism by which HI is oxidized to IO, in the
gas phase, needs to be considered.
r Where not available, a temperature dependent rate expression for aqueous and gas
phase reactions is required, particularly reactions involving iodine.
The Henry's constant for iodine species formed in the gas phase, e.g. IONO?, IO2
and MO2,needs quantification. Currently the values used have been estimated.
The deposition rate of 1203needs to be validated. In addition, the effects of air
flow on the resuspension of the aerosol must be addressed. The existence of other
aerosols of the form I,O, needs to be determined as well as the mechanism and
kinetics of their formation. The dissociation of 1203in the aqueous phase requires
examination, particularly with respect to the intemediate products formed.
r A detailed sensitivity test should be performed to determine the erron associated
with the model. To date suficient data are not available on which to base this
analysis on the error limits for significant reactions. Therefore, the sensitivity test
should examine the effects of altering rate constants by, for example, + 20% and
determinhg the impact on the volatility of iodine. The impact of gaslliquid volume ratio on the elirnination of gaseous iodine in the presence of hydrogen should be expenrnentally verified. 8.0 REFERENCES
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J. Chim. Phys. 70, 1404-9, 1973. Al FACSIiMILE Code
*GAS/AQUEOUS PHASE MODEL; "CREATED BY ANANDHI 2000; *Final Combined Model;
COMPILE iNSTANT; OPEN 6 "sensitivity.log";
PERMIT +- *< >;*symbols used with variables; VARIABLE N2G 02G H20G H2G C02G CH4G O3G N2G* 02G* NG OG N2G+ NG+ OG+ 02G+ H20G+ OHG+ H3G+ HG OHG EG- H30G+ 02G-H202G NOG HN02G HN03G N02G N03G N20G N205G N02G- N03G- C02G- COG CH3G CH3IG CH2IG IG HIG I202G CH302G CH20G CH30HG CH20HG CH30G CH30N02G CH30NOG CH302N02G C2H602G HOIG IOG I02G I203G INOG N02G H02N02G ION02G HCOG CH300HG 12G HC02HG H02G KNOG NO- NOG- 03G- IN03G HG* N02G+ N3G+ 2 1- 13- 01- HO1 1 12- 10-2 HOI- MEK PROD 102H OH- E- HO2 0- H OH 02- 03- I20H- I2B- 03HO3 OH- H02-HZ02 H203 IWET TRAP 102- 103- H3P04 H2P04- HP042- P043- P042-H2P04 HP04- M+ M2+ HI03- IO2 CO2 CH302 CH300H CH20 CH30H CH20H HC02H NO3 N03- NO2 N02- NO HN03 HN03- KN02 N203 CH20HOH C02H 1202 IO IN02 IN03 HI HOlOH 103 N O H2 02 1203 12s IS KPSN I2IPSN HOIIPSN IOIPSN HIPSN IN02IPSN IN03IPSN I2021PSN I02IPSN I203IPSN LEAK LEAKI2;
*DOSERATE [kGy/hr]; *P [atm]; *TEW KI; *MW [g/mol]; *PRA = aqueous production rate; *PRG = gas production rate; *M = third body reactions in gas phase;
PARAMETER DOSERATE 2 PEU PRG DOSE; +dose rate in kGyh; PARAMETER MOLE 6.022E23 TEMP 333 P 1 R 8.3 14 M ; PARAMETER DO 8 H20 55.56 H+ PH AEROSOL 3E-4; PARAMETER N2GO N2Frac 0.34 1 02G0 02Frac 0.09 1 H2GO H2Frac H20GO H20Frac 0.568 10- 1E-5 12GO ; PARAMETER VG 3 13 VL 27 AGL 37 N2MOLE 02MOLE H20MOLE H2MOLE ISMOLE TOTMOLE; PARAMETER N2F 02F H20F H2F I2F; *"N2 fraction"; PARAMETER MW MN2 28 MO2 32 MH20 18 MI2 254 MH2 2 WN2 W02 WH20 WH2 W12; *"WN2 = weight fraction of N2";
*IPSN Experiments; PARAMETER IPSN O AGL 1 OE-3 IPSNG;
*Tuming compents of the mode1 on/off; PARAMETER GAS 1 AQUE 1;
*G-values for N2 gas; PARAMETER GN2G+ 2.27 GEG-
*G-values for 02 gas; PARAMETER G02G+ 2.07 GEG-
*G-values for water vapour; PWTERGEG-
*G-values for liquid water; PARAMETER GE-2.75 GH 0.63 GH2 0.45 GOH 2.7 GH202 0.58 GH+ 2.7;
*Gas mass attenuation coefficients; PARAMETER EN2G 5.5 1 E-2 E02G 5.52E-2 EH20G 6.12E-2EH2G 1 .O9E- 1 TOTEN; * [cmA2/g];
*Surface Areas of Various Materials; PARAMETER STEEL 220 AERO 180 WPAINT 3300000 DPAINT IO6 ZINC 52;
*Ozone Deposition Calculation Parameters; PARAMETER VD 1 2.3E-3 VD2 1.1 E-2 VD3 2.8E-3 KA O;
'Interfacial Transfer; PARAMETER KTL SE-4 KTG 1.2E-1 ;
*Henry's Constants [=] (mol/L)aq / (mollL)gas; PARAMETER HE12 HE1 HEC02 HEHO2 HEM HE02 HEH202 HE03 HEHCOZH HECH300H HECH302 HEHN03 HENO HENO2 HEN03 HEOH HEHNOZ HEHOI 1.1 E4 HE10 1.1 E4 HEHI 5E4 HEIN02 5E4 HEIN03 5E4 HE1202 5E4 HE102 1.1 E4; * HEHOI, HEIO, HEHI, HEINOZ, HEIN03, KEI202 [LI * HE102 (assumed based on HEIO); *Venthg of Airborne Iodine; PARAMETER FLOW OE-2 LEAKRATE OE-07; *Le& rate = 1.2E-7; *Mass Balance of Species; PARAMETER IPC ISUPvlG ISUM TOT ;
PARAMETER GlG2G3G4G5G6G7G8G9GlOGllGI G20B G21 G22A G22B G23A G23B G23B 1 G23B2 G23C G24 G25A G25B G26 G27A G27B G27C G27D G29 G30 G3 1 G32 G33 G35 G37 G38 G39 G40 G41 G42 G43 G44 G45 G46 G47 G48A G48B G49 G50 G5 1 G52 GS3 G54 G55 G56 G57 G58 G59 G60 G6 1 G62 G63 G64A G64B G64C G65 G66 G67 G68 G69 G70 G71 G72 G73 G74 G75 G76 G77 G78A G788 G79A G79B G80 G8 1A G8 1 B G82 G83 G85 G86 G87 G88 G89 G90A G90B G91A G9lB G92 G93 G94 G95A G95B G95C G95D G96 G97 G98 G99 G100 GlOl G1O2 G103 G104 G105 G106 G107 GlO8 Gi09A GZ09B G110 G111 G112 GlU Gll4 G115 G116 G1 I7Gll8A Gll8B G118C GIN G120 G121 G122 G123 G124A G124B G125 G126 G127 G128 G129 (3130 G131 G132 G133 G134 G135 (3136 (3137 G138 G139 G140 (3141 G142 G143 G144 (3145 G146 G147 G148 G149 G150 G151 G152 G153 G154 G155 G156 G157 Gl58 G159 G160 G161 G162 G163 G164 (3165 G166 GL67 G168 (3169 G170 G171 G172 (3173 (3174 G175 (3176 G177 G178 G179 OZ1 022 023 OZ4 MT1 MT2 MT3 MT4 MT5 MT6 MT7 MT8 MT9 MT1 O MT1 1 MT13 MT1 3 MT14 MT 15 MT 16 MT 17 MT 18 MT 19 MT20 MT2 1 MT22 MT23 MT24 MT25 MT26 MT27 MT28 MT29 MT30 MT3 1 MT32 MT33 MT34 MT35 MT36 MT37 MT38 MT39 MT40 MT4 1 MT42 MT43 MT44 MT45 MT46 MTIPSNl MTIPSN2 MTIPSN3 MTIPSN4 MTIPSNS MTIPSN6 MTLPSN7 MTIPSNI MTTPSN9 MTIPSNlO MTIPSNI 1 MTIPSNl2 MTIPSN13 MTIPSN14 MTIPSN15 M'MPSN16 MTIPSN17 MTIPSNl8 CTA CTB CTC CT1 CT2 CT3 CT4 CTS CT6 CT7 CT8 CT9 CTlO CT11 CT 12 CT13 CT14 CT15 CT16 CT17 CT18 CTI9 CT20 CT21 CT22 CT23 CT24 CT25 CT26 CT27 CT28 CT29 CT30 CT3 1 CT32 CT33 CT34 CT35 CT36 CT37 CT38 CT39 CT40 CT4 1 CT42 CT43 VOLRATE FTR SS1 SS2 SS3 SS4 SS5 SS6 SS7 SS8 SS9 SS10 SSll SS12 SSl3 SSl4 SS15 SSl6 SSl7 SS18 Si9 SS20 SS21 SS22 VDS 0.0 1 Al A2 A3 A4 A5 A6 A7 A8 A9 A10 AIOA Al 1 A12 A13 A14 Al5 A16 A17 A18 A19 A20 A21 A22 A23 A24 A25 A26 A27 A28 A29 A30 A3 1 A32 A33 A34 A35 A36 A37A A37B A38 A39 A40 A41 A42 A42 A43 A44 A45 A46 A47 A48 A49 A50 A5 1 A52A A52B A53 A54 A55 A56 A57 A58 A59 A60 A6 1 A62A A62B A63 A64 A65 A66 A67 A67A A67B A68 A69 A70 A71 A72 A73 A74 A75 A76A A76B A77 A78 A79 A80 A8 1 A82 A83 A84 A85 A86 A87 A88A A88B A89 A90 A91 A92 A93 A94 A95 A96 A97 A98 A99 A100 A101 AI02 A103 A104 A105 A106 A107 A108 A109 Al 10 Al1 1 A112 Al 13 A1 14 Al 15 A1 16 A1 17 A1 18 Al 19 A120 A121 A122 A123 A124 A125 A126 A127 A128 A129 A130 A131 AL32 A133 A134A A1348 A135 A136 A137 A138 A139 A140 A141 A142 A143A A143B A144 AL45 A146 A147 A148 A149 A150 A151 A152 A153 A154 A155 A156 A157 A158 A159 Al60 A161 A162 A163 A164 A165 A166 A167 Al68 A169 Al70 Al71 A172 A173 A174A175 A176 A177 A178 A179 A180 A181 A182 A183 A184 A185 A186 A187 A188 A189 A190 A191 KG1 KG2 KG3 KG4 KG5 KG6 KG7 KG8 KG9 KG 10 KG1 1 KG1 2 KG 13 KG 14 KG 15 KG16 KG17 KG1 8 KG 19 KG20A KGSOB KG2 1 KG22A KG22B KG23A KG23BF KG23BR KG23C KG24 KG25A KG25B KG26 KG27A KG27B KG27C KG27D KG29 KG30 KG3 1 KG32 KG33 KG34 KG35 KG37 KG38 KG39 KG40 KG41 KG42 KG43 KG44 KG45 KG46 KG47 KG48A KG48B KG49 KG50 KG51 KG52 KG53 KG54 KG55 KG56 KG57 KG58 KG60 KG61 KG62 KG63 KG64A KG64B KG64C KG65 KG66 KG67 KG68 KG69 KG70 KG71 KG72 KG73 KG74 KG75 KG76 KG77 KG78A KG78B KG79A KG79B KG80 KG81A KG8 1%KG82 KG83 KG85 KG86 KG87 KG88 KG89 KG90A KG90B KG9 1A KG9lB KG92 KG93 KG94 KG95A KG95B KG95C KG95D KG96 KG97 KG98 KG99 KG100 KG101 KG102 KG103 KG104 KG105 KG106 KG107 KG108 KG109A KG109B KG1 10 KG1 Il KG1 12F KG1 12R KG113 KG1 14 KG1 15 KG1 16 KG1 17 KG1 18A KG1 18B KG1 18C KG1 19 KG120 KG121 KG122 KG123 KGl24A KG124B KG125 KG126 KG127 KG128 KG129 KG130 KG131 KG132 KG133 KG134 KG135 KG136 KG137 KG138 KG139 KG140 KG141 KG142 KG143 KG144 KG145 KG146 KG147 KG148 KG149 KG150 KG151 KG153 KG153 KG154 KG155 KG156 KG157 KG158 KG159 KG160 KG161 KG162 KG163 KG164 KG165 KG166 KG167 KG168 KG169 KG170 KG171 KG172 KG173 KG174 KG175 KG176 KG177 KG178 KG179 KA1 KA2 KA3 KA4 KA5 KA6 KA7 KA8 KA9 KA10 KAlOA KA1 1 KA12 KA13 KA14 KA15 KA16 KA17 KA18 KA19 KA20 KA21 KA22 M23F KA23R KA24 KA25 KA26 KA27 KA28 KA29 KA30 KA3 1F KA3 1R KA32 KA33 KA34 KA35 KA36 KA37A KA37B KA38 KA39 KA40 KA4 1 KA42F KA42R KA43 KA44 KA45F KA45R KA46 KA47KA48 KA49 KASOF KASOR KAS 1 KASSA KA53 KA52B KA54 KA55F KA55R KA56 KA57F KA57R KA58 KA59 KA6OF KA6OR KA61 KA62AF KA62AR KA62BF KA62BR KA63F KA63R KA64F KA64R KA65F KA65R KA66F KA66R KA67F KA67R KA67 KA67A KA67B KA68F KA68R KA69 KA70 KA71 KA72 KA73F KA73R KA74 KA75 KA76A KA76B KA77 KA78 KA79 KA80 KAS 1 KA82 KA83 KA84 KA85 KA86 KA87 KASSA KA88B KA89 KA90 KA9 1 KA92 KA93 KA94 KA95 KA96 KA97 KA98 KA99 KA100 KAlOlF KAlOlR KA102 KA103F KA103R KA103 KA104F KA104R KAIOSF UlO5R KAlO6F KAI06R KA107 KA108 KA109 KA1 10 KA1 11 KA112 KA1 13F KA1 l3R KA1 14F KA1 l4R KA1 15 KAI 16F KA1 l6R KA1 I7F KA1 lïR KA1 18 KA1 19 KA120 KA121 KA122 KA123 KA124 KA125 KA126 KA127 KA128 KA129 KA130 KA13 1 KA132 KA133 KA134A KA134B KA135 KA136 KA137 KA138 KA139 KA140 KA141 KA142 KA143A KA143B KA144 KA145 KA146 KA147 KA148 KA149 KA150 KA150 KA151 KA152 KA153 KA154 KA155 KA156 KA157 KA158 KA159 KA160 KA161F KAl61R KA162 KA163 ~~164~~165KA166 KA167 KA168 KA169 KA170 KA171 KA172 KA173 KA174 KA175 KA86 KA176 KA177 KA178 KA179 KA180 KA181 KA182 KA183 KAi84F KA184R KA185 KA186 KA187 KA188 KA189F KAl89R KA190F KA190R COMPILE INITIAL; * %BATCH% RUNS=l !JJNITS] I,N:\ANANDHI\FACS\DATA\sensitivity,OUT [PHI 9 %BATCH END% ;
H+ = 10.0 @(-PH) ; OH-= 1.OE- 14M+ ; HE02 = exp(l700ITEMP - 9.14); *[2]; HEH2 = exp(SOO/TEMP - 5.62); *[2]; 1- = IO-; M = P * IOl.XY(R * TEMP); 02GO = 02Frac * M; N2GO = N2Frac * M; H2GO = H2Frac * M; H20GO = HSOFrac * M; 02G = 02GO; N2G = N2GO; MG= H2GO; H20G = H20GO; I2G = I2GO; 02 = HE02 * 02GO; H2 = HEHS * H2GO; IF (TEMP - 385) 1 2 2; LABEL 1; HE12 = 10@((4220S/TEMP) - 19.99 1 + 0.02583 * TEMP); *[3]; HE1 = 1.8Y8O * HEI2;
LABEL 2; HE12 = 10@((5615.4/TEMP) - 25.179 + 0.02990 * TEMP); *[3];
LABEL 3:
COMPILE GENERAL;
DOSE = DOSERATE * TIME/3600; VOLRATE = CTA * 60 ; *Iodine Volitilzation Rate (moumin); *FTR = TRAP /(IO- * VL); *FTR = IPSNG/(IO- * VL); *IPSN Experiment; FTR = ISUMG * VG/(IO- * VL);
*Gas Composition Calculation; *-----_------N2MOLE = N2G * VG; 02MOLE = 02G * VG; HSOMOLE = H20G * VG; H2MOLE = H2G * VG; I2MOLE = I2G * VG; TOTMOLE = P * 101.325 * VG/ (R * TEMP); N2F = N2MOLE/TOTMOLE; 02F = 02MOLE/TOTMOLE; H20F = H20MOLE/TOTMOLE; H2F = H2MOLE/TOTMOLE; *12F = IZMOLE/TOTMOLE;
*Keeping track of I(g); [SUMG = 2 * 12G + IG + CH3IG + CH2IG + HIG + HOIG + EOG + 102G + 2 * I203G + MOG + N02G + 1ON02G + 2 * I202G + IN03G; *Keeping track of I; ISUM=2* D+HOI+I-+3 *13-+O[-+I+2* 12-+HOI- + 10-2 + 2 * I20H-+ I02H + 103- + 102- + HI03- + 102 + 2 * 1202 + 10 + NO2 + NO3 + HI + HOIOH + 2 * 1203; IPSNG = 2 * 12IPSN + IIPSN + HIIPSN + HOIIPSN + IOIPSN + I02tPSN + N021PSN + IN03IPSN + 2 * I202IPSN + 2 * I203IPSN; TOT = ISUMG * VG + ISUM * VL + Tl3A.P + IPSNG + (2 * 12s + IS) * VG + LEAK; *Reaction Rate Constants;
*Ga Reactions;
*------__---,-,------KG1 = 1.40E12; *[6]; KG2 = 1.40E12; *[6]; KG3 = 1.00E10: *[6]: KG4 = l.4OEll; *[6]; KG5 = 7.20E11; *[6]; KG6 = 2SOE 10; *[6]; KG7 = 1.9OE 10; *[6]; KG8 = 1 .OSE 1511 E06 * exp(8251TEMP); *[LA2/(molA2*sec)][298-5 801 [7]; KG9 = 1.63E 14/ 1E6 * (TEMP/298)@,(-2.7); *[LA2/(molA2*sec)][150-4001 [8]; *KG 1O = 4.828 12/ 1000 * exp(-206OKEMP); * [2OO-4OO] [ 1O]; KG 10 = 1.9E- 1 1 * 6.0228231 1000*exp(-23001TEMP); * [220- 10001 [9]; KG 1 1 = 2.698 1711 E06 * (TEMP/298)@(-2.4); * *[LA2/(molA2*s)][ 1O]; KG 12 = 3.78 1E 1811 EO6 * (TEMEV298)@(-4.27) * exp(-55 1.4/TEMP); * ~A2/(molA2*s)][l 11; KG13 = 1.6E10; *[12]; KG 14 = 7.125E16/1 E06 * (TEMP/298)@(-2.299) * exp(-228.7l'EMP); *&A2/(molA2*s)][200-23001 [Il]; KG 15 = 2.39E 18/ 1E6 * (TEMP/298)@(-3.94) * exp(- 1146JTEM.P); * [LA2/(molA2*s)][200-250Oi(3 [13]; KG16 = 3.EE lZl000 * exp(l20lTEMP); *[200-2500][ 131; KG17 = 6E09; *[9]; KG18 = 7.733E 12/1000 * exp(-3562REMP); *[zoo-3000] [il]; KG19 = 1.323E12/1000 * exp(-1414/TEMP); *[195-443] [Il]; KG2OA = %23E1 O/ 1000 * exp(-2450A'EMP); * [230-6OO] [ L O]; KGZOB = 6.03?2+05/1000; *[141; KG2 1 = 6.06803; *[14]; KG22A = 2.ZE 1211000 * exp(Z4O/TEMP); *[230-5001 [ 151; KG22B = 5.48E5/1000 * exp(28 19/TEMP) ; *[27 1-3031 [16]; KG23A = 7.23807; *[17]; KG23BF = 5.45E 16/ 1 E06 * (TEMP/298)@(-3.2); * [LA2/(moiA2*s)][220-3601 [ 151; KG23BR = 3.0 1E 181 1000 * exp(-9994TTEMP); *[Ll(mol*s)][245-3281 [ L 81; KG23C = 6.3 1El 7 * exp(- 13084A'EMP); *[sA- 11 [245-3281 [19]; KG24 = 9.04E 1 1/ 1000 * exp(360/TEMP); *[1 O]; KG25A = 1.1 SEO9; *[20]; KG25B = 1.5 1EO9; *[20]; KG26 = 4.94E 13/ 1000*exp(-4 1 O/TEMP); * [298-6701 [21]; KG27A = 1.8 1EO9; *[22]; *KG27£3= 3 SEW; * Willis & Boyd; KG27B = 1E09: *Literature reassessment; KG27C = 1.1 EO9; *[23]; KG27D = 1.4E09; *[23]; KG29 =1 .O 1E13/1000 * exp(l031TEMP) ; * [223 -4001 [24] ; KG30 = 4.3E 10/ 1000 * exp(- 14 I4REMP); *[25]; KG3 1 = 9.MlEll/lOOO * exp(1 l.WTEMP); * [200-5381 [Il];
KG58 = 2.89E l3IlOOO * exp(2SOTTEMP); * [252-4001; *[101; KG60 = 1.39E W1OOO * exp(1 lO/TEMP); *[220-5001; *[IO]; KG6 1 = 1.24812/1000 * (TEMP/298)@(1.S2)*exp(-1736lTEMP);*[250-258 11; * WI; KG62 = 1.75E 1211000 * expG 16OlTEMP): * [240-4601 [1 O]; KG63 = 1.69E 11/ 1000 * exp(594lTEMP); * [2 10-4201 [4 11; KG64A = 2.828 1YlOOO * exp(- IZOKEMP); *[23 1-4641 [42]; KG64B = 3.0 1E 13/ 1000 * exp(-866/TEMP); *[3UO- 10001 [43]; KG64C = 1.02E 12/ 1000 * exp(ZOO/TEMP); *[23 1-4641 [42]; KG65 = 8.50E04; *[44]; KG66 = 2SOE 1 1; *[44]; KG67 = 1.OOE 12; *[Ml; KG68 = 2SOE 1 1; *[44]; KG69 = 3.258 10/1000 * (TEMP/298)@( lS)*exp(250/TEMP); * [300-20001; *WI; KG70 = 2.OOE 1 1; *[44]; KG7 1 = 2.OOE 1 1; *[44]; KG72 = 1.00E 12; *[44]; KG73 = 1.OOE 12; *[44]; *KG96 = 1.00E 10; *2e9 in Sagert; *KG96 = 7.2808; *Las210 et.a1.(1995) uncertain though; *KG96 = 6.2E09; * Sander(1986) WAS IN USE; KG96 = 2.36E14/1E6 * exp(754/TEMP); *[45]; KG97 = 1.OOEO8; *[44]; KG98 = 1.00E08; *[a]; KG99 = L.OOE06; [44]; KG100 = 1.OOEO6; [44]; KG101 = 1.8E10; *[IO]; KG102 = 9.6E10 ; *[46]; KG103 = 7.00E09; *KG103 = lSEll; KG104 = 7.OOE- 18; KG105 = 0.06; *[47]; KG106=8.4E10; *[48]; KG 107 = 9.OE 10; *[49]; KG 1O8 = 1.2 1E 13/ 1000 *exp(-890/TEMP); * [200-3501 [ 1O]; KG lO9A = 9E03; *[Ml; KG109B = 9E03; *[44]; KG 1 10 = 2.00E08; *[44]; KG 1 1 1 = 1.OOEO9; *[44]; KG 112F = 3.97E l4/ 1000 * exp(-20/TEMP); * [250423] [SOI; KG1 12R = 8.02E11 * exp(-18685/TEMP); *[300-1000][5 11; KG1 13 = 5.00E10; *[44]; KG 114 = 5.00E05; *[44]; KG 1 15 = 1.75E L 3/ 1000 * exp(-26OOtTEMP); *[298-400]; *[IO]; KG1 16 = 5.00E 10; *[300] [52]; KG 11 7 = 4.4E 12/ 1000 * exp(330/TEMP); * [200-4001 [ 1O]; IF(TEA4P-373) * * 11; KG1 l8A = (1.73E-12 * exp (lOZO/TEMP) - (2.5E-11 + 1E-30 * (P * 10 1.3W (R * TEMP)))) * MOLE/ 1000; m 12; LABEL 11; KG1 18A = 9.92E8; LABEL 12; KG 118C = 0.05 * MOLE/lOOO * 1.73E-12 * exp (1020/TEMP); KG1 188 = (2.5E-Il+ 1E-30 * (P * 10 1.325/(R * TEMP))) * MOLE/1000 - KG118C; *KG1 18-/C [53];
KG1 19 = 9.OE08; *[54]; KG 120 = 3.2E-02; *[55]; KG12 1 = 2.7Ell; *[54]; KG1 22 = 7.838 1 1/1000 * exp(- l83O/TEMP); *[298-373 ][56]; KG123 = 8.86E12/1000 * exp(4090A'EM.P); *[283-353][57]; KG124A = 3.9E10; *[47]; KGl24B = 2.3E 10; *[58]; *for G 1NA and G l24B information from Waynes Halogen Oxide review used [59]; KG125 = 3E05; *average value [23]; KG126 = 3.OlEll; *[23]; KG127 = UEIl; *[23]; KG128 = 2.4E14; *[23]; KG129 = 1.2E14; *[23]; KG 130 = 1.2E 15; *[23]; KG13 1 = 6.02E13; *[23]; KG 132 = I .2E 15; *[23]; KG 133 = 4.2E 1 1; *[23]; KG134 = 5.4E 1 1; *[23]; KG 135 = 2E 1 1; *average value [23]; KG 136 = 6E9; *[23]; KG137 = 3.4808; *[23]; KG 138 = 4.7E 10; *[23]; KG139 = 4.8EI 1; *[23]; KG 140 = 3.7E09; *[23]; KG141 = 3.6E08;*[23]; KG 142 = 6E 13; *[60]; KG143 = 1.8lE14;*[60]; KG144 = 2.41E14;*[60]; KG145 = 4.8E14;*[60]; KG146 = 9.6E8;*[60]; KG147 =5.8E8;*[60]; KG148 = 7.8E8 * En(-950/TEMP);*[60]; KG149 = 1E10;*[60]; *KG150 = lElO;*[60]; KG 150 = 1.8E4;*[22]; KG 15 1 = 1.8E6;*[60]; KG152 =l.OE-1;*[60]; KG153 = 2.4E9; *[6]; KG154 = 4.2OEll: *[6]; KG155 = 2.29E4; *[61]; KG156 = 9E9; *[13]; KG157 = 1S9E 12; * [43]; KG 158 = 1.498-5; *[62]; KG 159 = 1.63 E 13/ 1000 * exp(-224/TEMP); * [200-400] [ 1O]; KG160 = 1.07E17IlE6 * (TEMP/298)-1; * [15]; KG161 =1.2E10; *[6]; KG 162 = 7.2E8;*[6]; KG163 = 4.00El1;*[6]; KG164 = 5.30E11; *[6]; KG165 = 2.03Ell; *[6]; KG 166 = l.8OEll; *[6]; KG167 = 4.06E10; *[6]; KG168 = 7.20E10; *[6]; KG169 = 2.26ELO; *[6]; KG170 = 3.00E10; *[6]; KG171 = l.7OEll; *[6]; KG172 = 3.5481 1; *[6]; KG173 = 5.00E11; *[6]; KG174 = 1.20E10; *[6]; KG 175 = 6.00E9; *[6]; KG176 = I.OOE1; *[6]; KG 177 = 6.OOE 1; *[6]; KG178 = 1.20E15; *[6]; *Aquesous Reactions; *------"---. KA 1 = 1.87E 10 * exp(-3700/(R * TEMP)) ; *[293-4531 [63]; KA2 = L88E 12 * expM 26OO/(R * TEMP)); *[64]; KA3 = 3.23E 12 * exp(- l26OO/(R * TEMP)); *[64]; KA5 = 6.00E+09; * [66]; KA6 = l.38E 13 * exp(- 176OO/(R * TEMP)); *[293-558, pH 8.51 [65]; KA7 = 8.50E+09; *pH 10- 13 [66]; KA8 = 8.47E09 * exp(- l4OOO/(R * TEMP)); *[287-433, pH = 7.81 [67]; KA 1O = 8.328 10 * exp(- 1gOOO/(R * TEMP)); *[293-503, pH 5.31 [68]; KAIOA = 1.1E08; *[69];
KA 1 1 = 6.328 13 * exp(-23000/(R + TEMP)); *[278-423, pH 1 1- 131 [70]; KA12 = 2.47El3 * exp(-16300/(R * TEMP)) ; * [277-338, pH 8.31 [71]; KA 13 = 2.20E+ 10; *[66]; U14= 1.30E+10; *[66]; KA 15 = 7.288 1 1 * exp(- 10000/(R * TEMP)); * [293-473] [72] ; KA16 = 3.508+09; *[66]; KA 17 = 3.3E 12 * exp(- 12000/(R * TEMP)); * [283-473] [73]; KA1 8 = 1.878 12 * exp(- 1 1500/(R * TEMP));* [293-4731 [63]; KA19 = 2.09812 * exp(-14700/(R* TEMP)); *[293-523, pH 21 [74]; KA20 = 3.23812 * exp(- lZ6OO/(R * TEMP)); *[64]; KA21 = 3.23812 * exp(-12600/(R * TEMP)); *[Ml; KA22 = 3.75E 10 * exp(- l64OO/(R * TEMP)); *[293-3531 [94]; W3F= 1.32E14 * exp(-38400/(R * TEMP)); *[286-3421 [75]; KA23R = 3.56808 * exp(-31700/(R * TEMP)); *[s"-11 [277-338, pH9.21 [71]; KA24 = 1.37E 11 * exp(-6200/(R * TEMP)); *[293-353, pH 21 [72]; KA25 = 1.WE+IO; *[66]; KA26 = 1.298+08; *[66]; KA27 = 6.00E+08: *[76]: KA28 = 7.00E+08; *[76]; * A27 and R28 rate constants estimated by Sehested,; *Holcman, Bjerbakke, Hart;
KA29 = S.OOE+O8; *[66]; KA30 = 4.00E+08; *[76]; KA3 1F = 3.48E 1 1 * exp(- 1 1 2OO/(R * TEMP)); *[293-3531 [77]; KA3 1R = 8.WE 1O * exp(43000/(R * TEMP)); *[sA- 11 [293-3431 [77]; KA32 = 8.00E+07; *[66]; KA33 = 3.98809 * exp(-20600/(R * TEMP));* [292-3 73, pHcZ] [78]; KA34 = 9.7807; *[95]; KA35 = 2.00E+00; *[66]; KA36 = 1Ell; *[79]; KA37A = 5.2OE+ 10; *[SOI; KA37B = 9E 10; *[8 11; KA38 = 3.60E-02; *[66]; KA39 = 2.00ElO; *[66]; KA40 = 1.988-05; *[66]; KA41 = 2.33E13 * exp(-12600/(R * TEMP)); *[64]; KA42F = 1.3OE10; *[82]; KA42R = 9.4E07; *[82]; KA43 = 1.5E09; '179,831; KA45F = 8.1E12 * exp(-12600/(R * EMP)); *[64]; KA45R = 1.29E8 * exp(-12600/(R * TEMP));*[64]; KA46 = 0.5; *[96]; KA47 = O. 13; *[96]; KA48 = 1E04; *[79]; KA49 = 7E1; *[79,97]; KASOF = 1.6E6 * exp(- 126OO/(R * TEMP)); *[64]; KASOR = 1.O3 E 12 * exp(- 18900/(R * TEMP)); *[64]; KA5 1 = 5.5806; *[97]; *KA52B = 9.68+09; * Bal!, Kupferschmidt ; *KA52B = 1.2E+ 10; * Evans; KA52B = 7E+09; *Sensitivity Analysis;
KA54 = 1SE+lO; *[98]; KA55F = UEl3*EXP(- 188401(R * TEMP)); *based on [100]; KA55R = 8.9E I 1*En(-40400/(R * TEMP)); *based on [100]; KA56 = 4.60E+09; * [98]; KA57F = 5.8E 10 * EXP(-6700/(R * TEMP)); *based on [100]; KA57R = KA57F11.875E6;*based on [100]; KA58 = 5.00E+08; *[84]; KA59 = 1 E 12 * exp(- 15OOO/(R * TEMP)); *[295-364, pH 71 [Ml; KA6OF = 6.38+09; *[86]; KA60R = 8.9E+06; *[86]; KA6 1 = 1.OE 12 * EX'(-2.050 16E4/ (R * TEMP)); *[276-3371 [87]; KA62BF = 3.2/H20; *[86]; KA62BR = 2.00E+ 10; *[86]; KA63F = 1.2E 11 *EXP( -125001 (R * TEMP)); *based on [86] and [100]; KA63R = KA63F/ 1.6E4; *based on [86] and [LOO]; KA64F = 1.34E+O6; *[86]; KA64R = 4.00E+08; *[86]; KA65F = 4.6E-0 1; *[100]; KA65R = 2.00E+IO; *[100]; KA66F = 1.00E+9; *based on [100]; KA66R = 7.8 lE+O3; *based on [100]; * See Aug2 1/98 paper notes; IF (PH - 6) * 4 4; KA67A = 4SOOE+ 1 ; *[100]; KA67B = 1.7E1; *[100]; mMP 5; LABEL 4: IF (PH- 8) * * 6; KA67A = 6.0 192 lO7E 1 * PH@2 - 6.3 l4573E2 * PH + 1.684972E3; *WI; KA67B = 0; *[88]; NMP 5; LABEL 6; KA67A = 5.8E2; *[£BI; KA67B = O; *[88]; LABEL 5; KA68F = 2.OE6; *[99]; KA68R = 1.3E7155.5; *[99]; KA69 = 1.3E 12 * En(-16OOOI (R * TEMP)); *based on [100];
KA7 1 = 1.200E-02; *[102]; *KA72 = 3E+03; *[103]; KA72 =7.5E4; *Sensitivity; *KA73F = 2.6E 1 1 * EXP(4 6OOO/(R * TEMP));*based on [100]; *KA73R = 3.2E8 * EXP (-16000 1 (R * TEMP)); *based on [100]; *KA74 = 1.3ELZ * EXP(- l6OOOI (R * TEMP));*based on [100]; *KA75 = l.2E8 * EXP(-50000/(R * TEMP)); *based on [100]; *KA76A = 2.00E+02; * Sims ; *ISA76B = 2.2E 10 * EXP (-50000/ (R * TEMP)); *based on [100]; KA77 = 9.5E+10; * [98]; KA78 = S.lOOE+lO; *[106]; KA79 = 3.500E+10; *[87]; KA83 = 3E 10; *Hypothetical; KA84 = 12.5; * [1 001; KA85 = 12.5/(H+)@2; *[IO01 ; KA86 = 3.OE9; *Based on CI02 reaction [107]; KA87 = 3.8E+10; *[103]; K488A = 2.1406+09; * [89]; KA88B = 2.6E09; *[go]; KA89 = S.OOOE+ 10; * Modified HOI- ; KA90 = 1.6E+10; *[9 11; KA9 1 = 1.800E+07; *[87] ; KA92 = 1.000E+ 10; *[87]; KA93 = 4.64E7; *[104]; KA94 = 2E9; *Lin, k estimated, 2e9 recommended, 2e8 originally; KA95 = 7.1 EOQ*(H+); *[92];
KA96 = 5E4; * le5 by Paquette, Se4 recommended ; KA97 = 9.58+07; * Paquette ; KA98 = 6.OE+09; * Mezyk ; KA100 = 25;*[105]; KA102 = 7.789; *[93]; KA 1O3F = 2.400E2 ; KA103R= L.OEO; *New frorn SIMS Model; KA142 = 1.9E06; *[79]; KAl43A = 1.3E09;*[5]; KA143B = 1.3EO9; *[79]; KA144 = IE09; *[79]; KA145 = 1E10; *[79,5]; KA 146 = 4.6E03; *[79]; KA147 = 5E05; *[79]; KA148 = 1.2EO9; *[79]; KA149 = 1E08; *[79]; KA150 = 1.1E09; *[108]; KA 15 1 = 45E09; * Estimated by [79]; KA152 = lE09; *Estimated by [79]; KA157 = 6.OEl: *[LI: KA158 = lSE09; *[LI; KA159 = 4.2E09; *[1]; KA160 = 1.7E9; *[log]; KAl6lF = 1E19;*Based on pKa for HI = -9.5; KA 16 1 R = 1E 1O;*assumed; KA162 = IElO; *Based on [l]; KA163 = lE10; *Based on [Il; KA164 = 1E 10; *Based on [l]; KA1 65 = 1E5; *[89]; KA166 = 5.1E7; *[1 IO]; KA167 = 7E9; *[Il 11; KA168 = 2E10; *[Il 11; KA169 = 1.3E6; *[Il 11; KA 170 = 1.33El; *[88, 114, 1 151; KA 173 = 6.6784; *[88, 1 14, 1 151; IF (PH - 6) * * 7; KA171 = 6E3; * [88, 1 14, 1 151; KA172 = 1.42E5; *[88, 114, 1151; KA 174 = 5E7; *[88, 114, 1151; JUMP 8; LABEL 7; IF (PH - 8) * * 9; KA 17I= 3.270298E4 * PH@3 - 6.994284E5 * PH@2 + 4.983908E6 * PH - 1.182602E7; KA172 = 4.2677 1E6 * LOG(PH) - 8.0 19 17E6; KA1 74 = 5.6907E22 * PH@(-1 -8061 E 1); JUMP 8; LABEL 9; KA171 = 6E4; KA172 = lE6; KA174 = 1XE6; LABEL 8; *KAl71/172/174 [85,114,115]; KA175 = 1.8E7; *[112]; KA1 76 = 3.23E 12 * exp(-12600/(R * TEMP)); *[64]; KA 177 = 5.2E 12 * exp(- l26OO/(R * TEMP));*[64]; KA 178 = 1.6ES * exp(- l26OO/(R * TEMP));*[64]; KA 179 = 2.6E 12 * exp(- 12600/(R * TEMP));*[64]; KA 180 = 7.6E8 * exp(- l26OO/(R * TEMP));*[64]; IC4 18 1 = 2.3E9 * exp(- l26OO/(R * TEMP));*[64]; KA 182 = 1.8E 12 * exp(- l26OO/(R * TEMP));*[64]; KA 183 = 1 -6E1 1 * exp(- 12600/(R * TEMP));*[64]; KA184F = 5.3E7; *[113]; KA l84R = 5.3E5;*[113]; KA1 85 = 9.7E9;*[113]; KA186 = lE7;*[113]; KA 187 = 1.44E 12 * exp(- l26OO/(R * TEMP)); *[64]; KA 188 = 1.6289 * exp(- 12600/(R * TEMP)); * [64]; KA189F = [.WEI 1; *pKa = -1.3; KA l89R = 1E 10; *assumed; KA190F = 5.1E6; *pKa = 3.29; KA 190R = 1E 1O; *assumed;
*S. 9 COMPILE EQUATIONS; *Radiolytic Production Rates;
*------,----,,------*' PR1 % PRG *GN2G *EN2G/(TOTEN) *WN2 := N2G; PR2 % PRG *G02G *E02G/(TOTEN) *WO2 := 02G; PR3 % PRG *GN2G* *EN2G/(TOTEN) *WN2:= N2G*; PR4 % PRG *G02G* *E02G/(TOTEN) *W02:= 02G*; PR5 % PRG *GNG *EN2G/(TOTEN) *WN2 := NG; PR6 % PRG/(TOTEN) *(GOG
MT13 % AGL/(VL * (1/KTL + HEH202KTG)) * (K202G * WH202 - H202):=H202; MT14 % AGL/(VG * (l/KTL + HEHZOZKTG)) * (H202 - H202G *HEH202) :=H202G; MT15% AGL/(VL * (1/KTL+ HE03KTG)) * (03G * HE03 - 03):=03; MT16 % AGL/(VG * (IKTL + HE03KTG)) * (03 - 03G * HE03) :=03G; MT1 7 % AGL/lVL * ( LKTL + HEHN03KTG)) * (HN03G * HEHN03 - HN03):=HN03; MT18 % AGL/(VG * (IKTL + HEHN03KTG)) * (HNO3 - HN03G * HEHN03):=HNO3G; MT19 % AGL/(VL * (KTL+ HENOKTG)) * (NOG * HENO - NO):=NO; MT20 % AGL/(VG * (l/KTL + HENOKTG)) * (NO - NOG * HENO) :=NOG; MT2 1 % AGL/(VL * (IKTL + HENOZKTG)) * (N02G * HENO2 - N02):=N02; MT22 % AGL/(VG * (KTL + HENOZKTG)) * (NO2 - N02G * HEN02):=N02G; MT23 % AGL/(VL * (l/KTL + HEN03KTG)) * (N03G * KEN03 - N03):=N03; MT24 % AGL/(VG * (LKTL + HEN03KTG)) * (NO3 - N03G * HEN03) :=N03G; MT25 % AGL/(VL * (IKTL + HEOWKTG)) * (OHG * HEOH - OH):=OH; MT26 % AGU(VG * (1KTL + HEOWKTG)) * (OH - OHG * HEOH) :=OHG; MT27 % AGU(VL * (LKTL + HEHN02KTG)) * (HNOZG* HEHNO2 - HNO2):=KN02; MT28 % AGL/(VG * (l/KTL + HEHNOZKTG)) * (HN02 - HNOZG * HEHNOZ):=HN02G; MT29 % AGL/(VL * (IKTL + KEHOVKTG)) * (HOIG * HEHOI - HOI):=HOI; MT30 % AGL/(VG * (1KTL + HEHOVKTG))* (HO1 - HOIG * HEHOI) :=HOIG; MT3 1 % AGL/(VL * (I/KTL + HEIOKTG)) * (IOG * HE10 - IO):=IO; MT32 % AGU(VG * (l/KTL + HEIOIKTG)) * (IO - IOG * HEIO) :=IOG; MT33 % AGL/(VL * (1KTL + HEHVKTG)) * (HIG * HEM - HI):=HI; MT34 % AGL/(VG * (1KTL + HEHVKTG)) * (HI - HIG * HEHI) := HIG; MT35 % AGL/(VL * (1/KTL + HEINOZKTG)) * (W2G * HEIN02 - IN02):=IN02; MT36 % AGL/(VG * (l/KTL + HEINOUKTG)) * (IN02 - INO2G * HEMOZ) := NO2G; MT37 % AGL/(VL * (1KTL + HEIN031KTG)) * (IN03G * HEIN03 - IN03):=IN03; MT38 % AGL/(VG *(lIKTL + HEIN03KTG)) * (IN03 - M03G *HEIN03) := IN03G; MT39 % AGL/(VL * (LKTL + HEI202KTG)) * (1202G * HE1202 - 1202):=I202; MT40 % AGL/(VG * (IKTL + HEIZOZKTG)) * (1202 - I202G * HEI202) := I202G; MT41 % AGL/(VL * (1KTL + HEIOZKTG)) * (I02G * HE102 - I02):=102; MT42 % AGL/(VG * (MTL + HEIOZKTG)) * (102 - I02G * HEIO2) :=I02G; MT43 % AEROSOL * AGL/(AGL + AGL 1) * I203G * VGNL := 1203; MT44 % - AEROSOL * I203G := 1203G; MT45 % IPSN * AEROSOL * AGL L/(AGL + AGLI) * I203G * VG := 12031PSN;
*Mas Transfer for [PSN Experiments;
MTPSN1 % IPSN * AGLI/(l/KTL + HEI2KTG) * (I2G * HE12 - IZIPSN) :=IZIPSN; MTIPSN2 % - IPSN * AGLll(VG * (IIKTL + HEIZIKTG)) * (I2G * HE12 - I2IPSN):=[2G; MTIPSN3 % iPSN * AGLII (IKTL + HEKTG) * (IG * HE1 - IIPSN):=IIPSN; MTPSN4 % - IPSN * AGLl/(VG * (1KTL + HEKTG)) * (IG * HE1 - IIPSN):=IG; MTIPSNS % IPSN * AGL l/(I/KTL + HEHOUKTG)* (HOIG * HEHOI - HOIIPSN) :=HOIIPSN; MTIPSN6 % - IPSN * AGL l/(VG * ( IKTL + HEHOVKTG)) * (HOIG * HEHOI - HOIIPSN) :=HOIG; MTPSN7 % PSN * AGL lI(1KTL + HEIOIKTG) * (IOG * HE10 - IOIPSN):=IOIPSN; MTIPSN8 % - IPSN * AGLl/(VG * (IKTL + HEIOKTG)) * (IOG * HE10 - IOiPSN):=IOG; MTIPSN9 % IPSN * AGLl/(l/KTL + HEHI/KTG) * (HIG * HEHI - HIIPSN):=HIIPSN; MTIPSNlO% - IPSN * AGL 1/(VG * (1KTL + HEHI/KTG)) * (HIG * HEHI - HIIPSN):=HIG; MTIPSN11% LPSN * AGL l/(I/KTL + HEMOZKTG) * (INOZG * HEIN02 - INOZIPSN) :=iNOZIPSN; MTIPSNI2 % - IPSN * AGLl/(VG * (1IKTL + HEINOZKTG)) * (INOLG * HEIN02 - INOZIPSN) :=n\102G; MTIPSN13% IPSN * AGLl/(L/KTL + HEIN03KTG) * (IN03G * HEIN03 - IN03IPSN) :=IN03IPSN; MTIPSN14 % - [PSN * AGLl/(VG * (l/KTL + HEM03KTG)) * (M03G * HEM03 - M03IPSN) :=IN03G; MTLPSNlS % IPSN * AGLl/(l/KTL + HEI202KTG) * (I202G * HE1202 - 1302IPSN) :=12021PSN; MTIPSN 16 % - IPSN * AGL l/(VG * (l/KTL + HEIZOZKTG)) * (I202G * HE1202 - 1202IPSN) :=I202G; MTIPSN17 % IPSN * AGLl/(l/KTL + HEIO2KTG) * (I02G * HE102 - IOZIPSN) :=I02LPSN; MTIPSN18 % - IPSN * AGLl/(VG * (11KTL + HEIOZKTG)) * (102G * HE102 - IOZIPSN) :=102G;
*Tramfer of Species to Charcoal Trap;
(r_~---,,-_,,,-,--,,,,,,,-,-," *(r_~---,,-_,,,-,--,,,,,,,-,-," ** CT1% - FLOWNG * H2G :=H2G; CT2 % - FLOWNG * 12G :=i2G; CT3 % - FLOWNG * IG:=IG; CT4 % - FLOWNG * C02G :=C02G; CT5 % - FLOWNG * H02G :=H02G; CT6 % - FLOWNG * H202G :=H202G; CT7 % - FLOWNG * 03G :=03G; CT8 % - FLOWNG * HCOZHG :=HCOZHG; CT9 % - FLOWNG * CH300HG:=CH300HG; CTlO % - FLOWNG * CH302G :=CH302G; CT11% - FLOWNG * HN03G :=HN03G; CT12 % - FLOWNG * NOG :=NOG; CT13 % - FLOWNG * N02G :=N02G; CT14 % - FLOWNG * N03G :=N03G; CT15 % - FLOWNG * OHG :=OHG; CT16 % - FLOWNG * HN02G :=HN02G; CT17 % - FLOWNG * HOIG:=HOIG; CT18 % - FLOWNG * IOG :=IOG; CT 19 % - FLOWNG * HIG := HIG; CT20 % - FLOWNG * N02G := IN02G; CT21% - FLOWNG * N03G := IN03G; CT22 % - FLOWNG * I202G := 1202G; CT23 % - FLOWNG * CH3IG := CH3IG; CT24 % - FLOWNG * CHîIG := CH21G; CT25 % - FLOWNG * 102G := I02G; CT26 % - FLOWNG * i203G := 1203G; CT27 % - FLOWNG * MOG := iNOG; CT28 % - FLOWNG * ION02G := ION02G; C129 % FLOWNG * (02GO - 02G) := 02G; CT30 % FLOWNG * (N2GO - N2G) := N2G;
CT3 1 % - LEAKRATE * HOIG := HOIG; CT32 % - LEAKRATE * IOG :=IOG; CT33 % - LEAKRATE * HIG := HG; CT35 % - LEAKRATE * IN02G := IN02G; CT36 % - LEAEXATE * M03G := IN03G; CT37 % - LEAKRATE * 1202G := I202G; CT38 % - LEAKRATE * I02G := I02G; CT39 % - LEAKRATE * I203G := I203G; CT40 % - LEAKRATE * INOG := INOG; CT41% - LEAKRATE * ION02G := ION02G; CT42 % - LEAKRATE * 12G :=I2G; CT43 % - LEAKRATE * IG:=IG;
*Accumulation of Iodine on the Charcoal Trap;
* -----,,,----,-,,,,,,,,,--,------,------CTA % FLOW * (2 * 12G + IG + CWIG + CH2IG + HIG + HOIG + IOG + 102G + 2 * I203G + [NOG + IN02G + ION02G + 2 * 1202G) :=TW: CTB % LEAKRATE * VG * (2 * 12G + [G + CH3IG + CHXG + HIG + HOIG + IOG + I02G + 2 * I203G + INOG + ïN02G + ION02G + 2 * 1202G) :=LEAK; CTC % LEAKRATE * VG * I2G := LEAKIS: *Adsorption of Iodine on Stainless Steel Surface;
*---* --,,,,,--,------,-,,,-,,------,------. SS 1 % STEEL/VG * ( VDS * t2G ) : = 12s; *3 16 SS; SS2 % STEEL/VG * (VDS * IG ) : = IS; *3 16 SS; SS12 % STEEL 1 VG * ( - VDS * I2G) : = 12G; *3l6 SS; SS13%STEEL/VG*( -VDS*IG):=IG;*316SS; *SS3 % ZINC 1 VL * (- VDS * 1) := 1; *ZINC PRIMER; *SS4 % ZINC / VL * (- VDS * 12) := 12; *ZINC PRIMER; *SS5 % ZINC/ VL * (VDS * 1) := IS; *ZMC PRIMER; *SS6 % ZINC / VL * (VDS* 12) := 12s; *ZMC PRIMER;
* GAS PHASE CHEMISTRY;
* Reactions with H20G; *------Gl % KG1 * GAS : N2G-t + H20G = H20G+ + N2G; G2 % KG2 * GAS : NG+ + H20G = H20Gt + NG; G3 % KG3 * GAS: 02G+ + H20G = H20G+ + 02G; G4 % KG4 * GAS: OG+ + H20G = H20G+ + OG; G5 % KG5 * GAS: H20G+ + H20G = H30G+ + OHG; *Reactions with 02G;
-*,~-,,,,,,,,,,,,,------* -*,~-,,,,,,,,,,,,,------G6 % KG6 * GAS: N2G+ + 02G = N2G + 02Gt; G7 % KG7 * GAS: EG- + 02G = 02G-; G8 % KG8 * GAS: HG + 02G + M = H02G + M; G9OhKG9 *GAS: OG+02G+M=03G+M: GI0 % KG10 * GAS : 03G + OG = 02G + 02G;
*Reactions with NOG/N02G/N03G;
*-,-,,,,,,,,-,,,,,,------,--- (311% KG11 * GAS: NOG + OHG + M= HNO2G + M; G12% KG12 * GAS: N02G + OHG + M = HN03G + M; G13 % KG13 * GAS: N03G + OHG = H02G + N02G; G14 % KG14 * GAS: NOG + OG + M = N02G + M; GI5 % KG15 * GAS: N02G + OG + M = NO3G + M; G16 % KG16 * GAS: N02G + OG = NOG + 02G; G17 % KG17 * GAS: OG + N03G = 02G + N02G; G18%KG18*GAS:NG+02G=NOG+OG; GI9 % KG 19 * GAS: NOG + 03G = N02G + 02G; G20A% KG2OA * GAS: N02G + 03G = N03G + 02G; G20B% KG2OB * GAS: N02G + 03G = 02G + 02G + NOG ; G21% KG21 * GAS: NO3G + O3G = N02G + 02G + 02G; G22A % KG22A * GAS: NOG + H02G = N02G + OHG; *NASA; G22B % KG22B * GAS :NOG + H02G = 02G + HNOG; G23A % KG23A * GAS : N02G + H02G = HNO2G + 02G; G23B % KG23BF * GAS % KG23BR * GAS: N02G + H02G + M = H02N02G + M; G23C % KG23C * GAS: H02N02G = HNO2G + 02G; G24 % KG24 * GAS: OHG + H02N02G = H20G + N02G + 02G; G25A % KG25A * GAS: N03G + H02G = HN03G + 02G; G25B % KG25B * GAS: N03G + H02G = OHG + N02G + 02G; G26 % KG26 * GAS : NOG + NG = N2G + OG; G27A % KG27A * GAS: NO2G + NG = N20G + OG; G27B % KG27B * GAS : N02G + NG = NOG + NOG; G27C % KG27C * GAS: N02G + NG = N2G + 02G; G27D % KG27D * GAS: N02G + NG = N2G + OG + OG; G29 % KG29 * GAS: NOG + N03G = N02G + N02G; G30 % KG30 * GAS: N03G + N02G = N02G + NOG + 02G: G3 1 % KG3 1 * GAS: N02G + N03G = N205G; G32 % KG32 * GAS: N205G = N02G + N03G; G33 % KG33 * GAS: N205G + H20G = HN03G + KN03G; *G35 % KG35 * GAS: N03G + N03G = N02G + N02G + 02G; G37 % KG37 * GAS: EG- + N02G = NO2G-; G38 % KG38 * GAS: EG- + N03G = N03G-; G39 % KG39 * GAS: H30G+ + N02G- = HG + N02G + H20G; G40 % KG40 * GAS: H30G+ + N03G- = HG + N03G + H20G; G41% KG41 * GAS: HG + N02G = OHG + NOG; G42 % KG42 * GAS: HG + N03G = OHG + N02G; G43 % KG43 * GAS: HN02G + OHG = N02G + H20G; G44 % KG44 * GAS: HN02G + HN02G = NOG + N02G + H20G; G45 % KG45 * GAS: HN02G + HN03G = N02G + N02G + H20G; G46 % KG46 * GAS: HN02G + N03G = HN03G + N02G; G48A % KG48A * GAS: N03G = NOG + 02G; G48B % KG48B * GAS: N03G = N02G + OG; G49 % KG49 * GAS: N03G + COG = NOSG + C02G; G50 % KG50 * GAS: N03G + N20G = N2G + N02G + 02G; G51% KG5 1 * GAS: N03G + H202G = H02G + HN03G; G52 % KG52 * GAS: OHG + HN03G = N03G + H20G;
*Miscellaneous Gas Reactions;
* _U__---- 9 G53 % KG53 * GAS: H30W + 02G- = HG + 02G + H20G; G54 % KG54 * GAS: H30G+ + EG- = HG + H20G; GS5 % KG55 * GAS: NG + NG + M = N2G + M;
*OHG Reactions; * ------
G56 % KG56 * GAS: OHG + OHG + M = H202G + M; G57 O/o KG57 * GAS: OHG -+ OHG = H20G + OG; G58 % KG58 * GAS: OHG + H02G = H20G + 02G; G60 % KG60 * GAS: OHG + OG = 02G + HG; G6 1 % KG6 1 * GAS: OHG + H2G = H20G + HG; G62 % KG62 * GAS: OHG + H202G = H20G + H02G;
*H02G Reactcions; *------G63 % KG63 * GAS: H02G + H02G = H202G + 02G; G64A % KG64A * GAS: HG -+ H02G = OHG -+ OHG; G648 % KG64B * GAS: HG + H02G = H20G + OG; G64C % KG64C * GAS: HG + H02G = H2G + 02G;
*COG/C02G Reactions;
*------"- ,,,,,,,, . G65 % KG65 * GAS: EG-+ C02G = C02G-; G66 % KG66 * GAS: 02G- + C02G = C02G-+ 02G; G67 % KG67 * GAS: C02G-+ H30W = HG + H20G + C02G; G68 % KG68 * GAS: 02- + C02G-= COG t- 02G + OG; G69 % KG69 * GAS: COG + OHG = C02G + HG; G70 U/o KG70 * GAS: 02G- + OHG+ = 02G + OHG; G71% KG71 * GAS: C02G-+ OHG-+- = C02G + OHG; G72 % KG72 * GAS: 02G-+ H2G+ = 02G + H2G; G73 % KG73 * GAS: C02G- + H2G+ = C02G + H2G; * Iodine Reactions;
*-, ,,,,,,,- G96 % KG96 * GAS: IG + TG + M = I2G + M; G97 % KG97 * GAS: MG* + 12G = N2G + IG + IG; G98 % KG98 * GAS: 02G* + I2G = 02G + IG + IG; G99 % KG99 * GAS: N2G* + N2G = N2G + N2G; G 100 % KG100 * GAS: 02G* + N2G = 02G + N2G; G101% KG101 * GAS: HIG+OHG = H20G + IG; G 102 % KG 102 * GAS: OHG + 12G = HOIG + IG; G 1 O3 % KG103 * GAS: OHG + HOIG = H20G + IOG; G104 % KG 104 * GAS: HOIG = OHG + IG; G 105 % KG 105 * GAS: HOIG + 02G = IOG + H02G; G106 % KG106 * GAS: OG + 12G = IOG + IG; G107 % KG107 * GAS: OG + IOG = 02G + IG; GlO8 % KG108 * GAS: IG + 03G = IOG + 02G; G109A % KG109A * GAS: 12G + 03G = IOG + IG + 02G; G109B % KGl09B * GAS: 12G + 03G = IOG + I02G; G110 % KG1 10 * GAS: IOG + 03G = I02G + 02G; Gl 1 I % KG1 1 1 * GAS: LOG + I02G = I203G; G112 % KG112F * GAS % KG1 12R* GAS : HG+ 12G = HIG+ IG; G113 % KG113 * GAS: HG+ HOiG = H2G+ IOG; G114 % KG1 14 * GAS: HOIG + HN02G = IN02G + H20G; G115 % KG1 15 * GAS: N02G + N02G = 12G + N02G + N02G; GH6% KG116 * GAS: EG +IN02G=I2G+N02G; Gll7 % KG117 * GAS: IOG+NOG=N02G + IG; G118A % KG1 18A * GAS: lOG + IOG = IG + IG + 02G; G 118B % KG 118B * GAS: LOG + IOG = I02G + IG; *G1 1SB % KG 118B * GAS: IOG + IOG = I202G; G 118C % KG 118C * GAS: IOG + IOG = I2G + 02G; G119 % KG1 19 * GAS: 12G + N03G = IG + ION02G; G 120 % KG120 * GAS: ION02G = IOG + N02G; G121% KG121 * GAS: IG +N03G = IOG +N02G; G 122 % KG 122 * GAS: N03G + HIG = HN03G + IG; G 123 % KG 123 * GAS: IG + H02G = HIG + 02G; G124A % KG1 24A * GAS: IOG + H02G = HOIG + 02G; G124B % KG124B * GAS: IOG + H02G = OHG + IG + 02G;
*New reactions from boyd paper:
* ------* G125 % KG125 * GAS: 02G+ + N2G = NOGi + NOG; *average value; Gl26 % KG 126 * GAS: N2G+ + NOG = NOG+ + N2G; G127 % KG127 * GAS: 02Gt + NOG = NOG+ + 02G; G128 % KG128 * GAS: NO= + EG- = NG + OG; G129 % KG 129 * GAS: 02G+ + EG- = OG + OG; G130 % KG130 * GAS: 02G+ + 02G-= OG + OG + 02G; Gl3l %KG131 * GAS: N2G++ EG-=NG+NG; G132 % KG 132 * GAS: N2Gt + 02G-= NG + NG + 02G; G133 % KG133 * GAS: 03G- + N02G = N02G-+ 03G; G134 % KG134 * GAS: NOG- + 02G = 02G- + NOG; G 135 % KG 135 * GAS: 02G- + 03G = 03G- + 02G; *average value; G136 % KG136 * GAS: N02G- + 03G = N03G- + OSG; G137 % KG137 * GAS: NG + 03G = NOG + 02G; G138 % KG138 * GAS: EG-+ NOG + M = NOG- + M; G139 % KG139 * GAS: 03G- + NOG = N02G-+ 02G; G140 % KG140 * GAS: NG+OG+ M =NOG+ M; G141% KG14 1 * GAS: 02G + NOG + NOG = N02G + N02G;
G142 % KG142 * GAS : 02Gt -+ N02G- = 02G + N02G; G 143 % KG 143 * GAS: N02G- + NO= = N02G + NOG; GI44 % KG144 * GAS: 02G- + NOG+ = 02G + NOG; G145 % KG145 * GAS: 02G-+ N02G =N02G-+ 02G; G146 % KG146 * GAS: NG + N20G = NOG + N2G; G147 % KG147 * GAS: OG + OG + N2G = 02G + N2G; G148 % KG148 * GAS: OHG + 03G = H02G + OSG; G149 % KG149 * GAS: OG + HN02G = N02G + OHG; G150 % KG150 * GAS: OG + HN03G = N03G + OHG; G151% KG151 * GAS: HO2G + O3G = OHG + 02G + 02G; G 152 % KG152 * GAS: NOG + W03G = HN02G + N02G; G153 % KG153 * GAS: N02G-+ N02G = N03G- + NOG; G 154 % KG154 * GAS: N02G- + N205G = N03G- + N02G + N02G; G 155 % KG 1% * GAS: OHG + N20G = H02G + N2G; G 156 % KG156 * GAS: OHG + HNOG = H20G + NOG; G157 % KG157 * GAS: OHG + HG + H20G = H20G + H20G; G158 % KG158 * GAS: H02G + H2G = HZ02G + HG; GIS9 % KG159 * GAS: H02G + OG = OHG + 02G; G160 % KG160 * GAS: IG + N02G + M = IN02G + M; Gl61 %KG161 *GAS: OG++02=02G++OG; Gl62 % KG162 * GAS: OG++ N2G = NOW + NG; G163 % KG163 * GAS: 02G-t + N02G = N02G+ + 02G; G164 % KG164 * GAS: 02- + N205G = N02G+ + N03G + 02G; G 165 % KG1 65 * GAS: NG+ + 02G = NG + 02G+; Gl66 % KG166 * GAS: NEt + 02G = NOG+ + OG; G167 % KG167 * GAS: NG+ + 02G = OG+ + NOG; G168 % KG168 * GAS: NG+ + N2G = N3Et; G169% KG169 * GAS: N3G++OîG =NOG++OG+N2G; Gl7O % KG170 * GAS: N3Et + 03G = N02Et + N2G; G 17 1 % KG 17 1 * GAS: N02G-t + NOG = NO@ + N02G; G 172 % KG 172 * GAS: NOG+ + N205G = N02Gt + N02G + N02G; *G173 % KG173 * GAS: 02G- + N02G = N02G- + 02G; (3174 % KG174 * GAS: 03G- + N02G = N03G- + 02G; G175 % KG175 * GAS: 03G- + NOG = N02G- + 02G; G176 % KG176 * GAS: NG + N03G = N02G + NOG; G177 % KG177 * GAS: NG + N20SG = N02G + N02G + NOG; G178 % KG178 * GAS: NO= + N03G- = N02G + N02G; G 1 79 % KG 179 * GAS: N02G+ + N03G- = N02G + N03G;
*AQUEOUS PHASE CKEMISTRY;
* Reaction with OH; * ------O----* Al% KA1 *AQUE:OH +OH =H202; A2 % KA2 * AQUE: OH + E- = OH- ; A3 % KA3 * AQLIE: OH + H = H20 ; A5 % KAS * AQUE: OH + HO2 = H203; A6 % KA6 * AQUE: OH + 02- = OH- + 02 ; A7 % KA7 * AQUE: OH + 03- = HO2 + 02- ; A8 % KA8 * AQUE: OH + H202 = H20 + 02- + H+ ; AlO%KAlO*AQUE:OH +H2 =H20+H; A 1OA% KA1 OA * AQUE: OH + 03 = HO2 + 02;
* Reactions wiîh e- ; * ------,------All%KAIl 'AQUEE- +E- =HZ+OH-+OH-; A12% KA12*AQUE:E- +H =OH-+H2; A13%KA13*AQUE:E- +O- =OH-+OH- ; A14 % KA14 * AQUE: E- + 02- = H02- + OH- ; AIS% KA15 *AQUE: E- +HZ02 =OH +OH-; A16% KA16 * AQUE: E- + H02- =O- +OH- ; A17% KA17*AQUE:E- +H+ =H ; A18% KAlg*AQUE:E- +O2 =02- ; * Reactions with H ;
* ------,------•
Al9 % KA19 * AQUE: H + H = H2 ; A20 % KA20 * AQm: H + HO2 = H202 ; A21 % KA21 *AQUE:H +02- =H02- ; A22 % KA22 * AQUE: H + H202 = H20 + OH; A23 % KA23F * AQUE% KA23R * AQUE: H + OH- = E- + H20;
A24 % KA24 + AQUE: H + 02 = HO2 ; A25 % KA25 * AQUE: H + O- = OH- ;
* Reactions with O- ; * ------. A26 % KA26 * AQUE: 0- + 0-= H202 + OH-+ OH- ; A27 % KA27 * AQUE: O-+ 02-= 02 + OH-+ OH- ; A28 % KA28 * AQUE: O- + 03-= 02-+ 02- ; A29 % KA29 * AQUE: O- + H202 = 02-+ H20 ; A30 % KA30 * AQUE: O-+ H02- = OH-+ 02-; A31% KA31F*AQUE%KA3lR*AQUE:O-+02=03-; A32 % KA32 * AQUE: O-+ H2 = H + OH-;
* Other Reactions ;
* ------,------,---,*' A33 % KA33 * AQUE: HO2 + HO2 = H202 + 02 ; A34 % KA34 * AQUE: HO2 + 02- + H20 = HZ02 + OH-+ 02; A35 % KA35 * AQUE: K203 = 02+ H20; A36 % KA36 * AQLrE: 03-+ H20 = 02+ OH + OH-; A37A % KA37A * AQUE: 03- + H+ = HO3 ; A37B % KA37B * AQUE: 03-+ H+ = OH + 02; A38 % KA38 * AQUE: H202 = H+ + FIOZ-; A39 % KA39 * AQUE: H+ + H02- = H202 ; A40 % KA40 * AQUE: H20 = H+ + OH-; A41 % KA4 1 * AQUE: H+ + OH- = H20; A42 % KA42F * AQUE % KA42R * AQUE : OH + OH- = O-+ H20; A43 % KA43 * AQUE: 02- + 03= 02 + 03- ; A45 % KA45F * AQUE% KA45R * AQUE : H+ + 02- = HO2; A46 % KA46 * AQUE: HO2 + H202 = OH + 02+ H20; A47 % KA47 * AQUE: 02- + H202 = OH + 02 + OH-; A48 % KA48 * AQUE: HO2 + 03 = OH + 02 + 02; A49 % KA49 * AQUE: 03 + OH-= 02 + H02-; A5 1 %KA5 1 * AQUE: H02- + 03= HO2 + 03- ;
*Oxidation of 1-;
*-*------** A52B % KA52B * AQUE: 1- + OH = I+ OH-; A54 % KA54 * AQUE: 1 + 1 = 12 ; A55 % KA55F * AQUE% KA55R * AQUE : 1 + 1- = 12- ; A56 % KA56 * AQUE: 1 + 12- = 13- ;
------..* A57 % KA57F * AQUE% KA57R * AQUE : 12 + 02-= 12- + 02 ; A58 % KA58 * AQUE: 12- + 02- = 1- + 1- + 02 ; A59 % KA59 * AQUE: 12- + 12- = 13- + 1- ; A60 % KA6OF * AQUE% KA6OR * AQUE: 12 + 1- = 13- ; A61 % KA61 *AQUE: I3-+02-=02+I-+I2-;
*A62A % KA62AF * AQUE% KA62AR * AQUE : I2 + H20 = HO1 + 1- + H+ ; A62B % KA62BF * AQUE% KA62BR * AQUE: 12 + HZ0 = I20E-I- + H+ ; A63 % KA63F * AQUE% KA63R * AQUE: 12 + OH- = 120H- ; A64 % KA64F * AQUE% KA64R * AQUE: I20H-= HO1 +. 1- ; A65 % KA65F * AQUE% KA65R * AQUE: HO1 = H+ + 01- ; A66 % KA66F * AQUE% KA66R * AQUE: HO1 + OH- = H20 + QI- ; A67A % KA67A * AQUE: HO1 + HO1 = 102- + 1- + H+ + H+; A67B % KA67B * AQUE: 102- + t- + H+ + H+ = HO[ + HOI;
*Reactions with H202; * ------
A68 % KA68F * AQUE% M68R * AQUE: I20H- + H202 = 1- + IOZH + H20 ; A69 % KA69 * AQUE: I02H + OH- = 02 + H20 + 1- ; A7 1 % KA7 1 * AQUE: H202 + 1- = HO1 + OH-; *A72 % KA72 * AQUE: H202 + I= t- + HO2 + H+ ;
*altemate mechanism; *A73 % KA73F * AQUE% KA73R * AQUE: 12 + H02- = 1- + I02H ; *A74 % KA74 * AQUE: HO1 + H02- = I02H + OH-; *A75 % KA75 * AQUE: I02H = 1- + 02 + H+ ; *A76A % KA76A * AQUE: HO1 + H202 = H+ + 02 + 1- + H20 ; *A76B % KA76B * AQUE: HO1 + H202 = I02H + H20;
*Water Radiolysis Products With 12 & 1;
*Ot.erReactions;
A83 % KA83 * AQUE: 02- + 1= 1- + 02 ; *specuIated reaction; A84 % KA84 * AQUE: 02- = 02 ; A85 % KA85 * AQUE: 02- + H+ + H+ = H202 ; A86 % KA86 * AQUE: 02- + 102 = 102- + 02; A87 % KA87 * AQUE: I2- + OH = 12 + OH- ; A88A % KAMA * AQm: I- + 0-= 10-2 ; A88B % KA88B * AQUE: I- + 0- = 1+ OH- ; A89 % KA89 * AQUE: 10-2 + H+ = 1 + OH- ; A90 % KA90 * AQUE: E- + 01- = 10-2 ; A91 % KA91 *AQUE: HO2 +I2=H++02+12-; A92 % KA92 * AQUE: HO2 + 12- = 12 + H02- ;
* Iodate Reaction Set;
*,---,-*,,---,_---- -,,--,,,, A93 % KA93 * AQUE: 102 + 102 + H20 = 103- + 102H + H+; A94 % KA94 * AQUE: 102 + OH = 103- + H+ ; A95 % KA95 * AQUE: 103- + E- + H+= HI03-; A96 % KA96 * AQUE : 103- + 02-= H103- + 02+ OH- ; A97 % KA97 * AQUE: 103- + H = HI03- ; A98 % KA98 * AQUE: HI03- + HI03- = 102H + 103- + OH-; Al00 % KA100 * AQUE: I02H + I02H = H+ + 103- + HO1 ; A102 % KA102 * AQUE: E- + 103- = IO2 + OH- + OH-; A103 % KA103F * AQUE% KA103R * AQWE: HO1 + 102- = 103- + I- + H+;
*Nitrogen Oxide Reactions;
* ------,------*- A142 % KA142 * AQUE: NO3 + H202 = N03- + H+ + H02; A143A % KA143A * AQUE: NO2 + OH = H+ + N03- ; A143B % KA143B * AQUE: NO2 + OH = HN03; A144 % KA144 * AQUE: HN02 + OH = NO2 + H20; A145 % KA145 * AQUE: N02- + OH = NO2 + OH-; A146 % KA146 * AQUE: HN02 + H202 + H+ = HN03- + H+ + H20; A147 % KA147 * AQUE: N02- + 03 = N03- + 02; A148 % KA148 * AQUE: N02- + NO3 = NO2 + N03-; A149 % KA149 * AQUE: NO2 + NO2 = HN02 + H+ + N03-; Al50 % KA150 * AQUE: NO2 +NO=N203; A151 %KA151 * AQUE: N03+H02=N03- +H++02; A152 % KA1 52 * AQUE: NO3 + 02- = N03- + 02;
*New Reactions Found; *------" ------
A 157 % KA 157 * AQUE: 102- + Hz02 = 103- + H20; A 158 % KA158 * AQUE: IO + IO = HO1 + 102- + H+; A159 % KA159 * AQUE: 1- + O3 = HO1 + 02; A 160 % KA 160 * AQUE : 0- + 01- = IO + OH-; A161 % KA161F * AQUE %KA161R * AQUE : HI = H+ + 1-; A162 % KA162 * AQUE: MO2 + H20 = HO1 + HN02; A163 % KA 163 * AQUE: IN03 + H20 = HO1 + HN03; A 164 % KA 164 * AQUE: 1202 + H20 = HOI + 102- + H+: Al65 % KA165 * AQUE: 12- + HO1 = IO + 1- + 1- + Hi; A166 % KA166 * AQUE: 12- + 01- = 1- + 1- -+ IO; A167 % KA167 * AQUE: OH + HO1 = HOiOH; A168 % KA168 * AQUE: E- + HO1 = HOI-; A1 69 % KA L 69 * AQUE: HOIOH = HZ0 + IO;
*New Additions to 12 Hydrolysis; ------O--- - A170 % KA1 70 * AQUE: 120H-+ 120H-= 102- + H+ + H+ + 1- + 1- + 1-; A1 7 1 % KA17 1 * AQUE: I20H- + HO1 = 102- + H+ + H+ + 1- + 1-; A172 % KA172 * AQUE: HO1 +OI-~102-+H++ 1-; A173 % KA173 * AQUE: 01- + 01- = 102- + 1-; A1 74 % KA1 74 * AQUE: I20H- + 01- = 102- + H+ + 1- + 1-; A175%KA175 *AQUE:I2-+H=[-+1-+H+; AI76 % KA 176 * AQUE: E- + HO2 = H02-; A177 %KA177 * AQüE: N+OH =H+NO; A178 % KA178 * AQUE: NO + 02 = NO2 + 0; A179 % KA179 * AQUE: N02- + H = NO + OH-; A 180 % KA L 80 * AQUE: N03- + H = NO2 + OH-; A181 %KA181 *AQUE:NO+NO+02=N02+NO2; A182 % KA182 * AQUE: E- + H20 + N03- = NO2 + OH- + OH-; A1 83 % KA 183 * AQUE: H+ + N02- + E- = NO + OH-; A184 % KA184F * AQUE% KA184R * AQUE: OH + HN03 = NO3 + H20; A 185 % KA 185 * AQUE: E- + N03- = NO2 + H20; A186 % KA 186 * AQUE: H + N03- = NO2 + H20; A187 % KA187 * AQUE: OH + NO = N02- + H+; A188 % KA188 * AQUE: NO2 + NO2 + H20 = H+ + H+ + N02-+ N03-; A189 % KA189F * AQUE% KA189R * AQüE: HN03 = H+ + N03-; A190 % KA l9OF * AQüE% KA NOR * AQUE: HN02 = H+ + N02-;
A191 % lE9 * AQUE : 1203 + ti20 = H+ + H+ + 102- + I02-;
SETPSTREAM 1 8; TIME PH ISUMG;
COMPILE PHI;
OH-= 1.OE-14/H+ ;
COMPILE Pm;
OH-= LOE-14W ; COMPILE PH3;
OH- = 1.OE-14M+ ;
COMPILE PH4;
OH- = 1 .OE-14M+ ;
COMPILE
COMPiLE OUT; PSTREAM 1;
WHENEVER
*SZMS TIME; *TIME = O +5760*24 CALL OUT; *TIME = 165600 +2 l6OO* 10 CALL OUT; *TIME = 3.7E5 %;
*SIMS TIME FOR TEMP; *TIME = O + 1440*25 CALL OUT; *TIME = 3.7E4 %;
*FAR.IBORZ TIME; *TIME = O + 96*5 CALL OUT; *TM= 4.8E3 + 5.76E3*20 CALL OUT; *TIME = O + 4.8E3*25 CALL OUT; *TLME = 1.3E5 %;
JIANANDHITIME; *TIME = O + 720*5 CALL OUT; *TIME = 3600%; *TIME = O + 374*25 CALL OUT; *TIME = 2.38E4 + 1.435E4*3 CALL OUT; *TIME = 8.13e4%; *TIME = 9.36E3%;
*GORBOVITSKAYA TIME: *TIME = O + 288*25 CALL OUT; *TIME = 7200 CALL OUT; *TME = 720 1%; *TIME = O + 2E3*25 CALL OUT; *TIME = 5.1 E4%; *TIME = 7.2E3 CALL OUT; *TIME = 720 1%;
*HOCHONADEL TIME; *TIME = O + 6O* IO CALL OUT; *TIME = 1080 + 480*90 CALL OUT; *TIME = 5.5E3%; *TIME = O + 0.02 * 10 CALL OUT; *TIME =0.3% ;
*TUME = 2.808e5 CALL OUT; *TIME = 2.88e5 CALL OUT; *TIME = 8.424e5 CALL OUT; *TIME = 8.5E5%; *TTME = O + 8000*25 CALL OUT; *TIME = 2.1E5%; *TIME = S.l6ES CALL OUT; *TIME = 2.17E5%; *ASHMORE TIME; *TIME = O + 1.08E4*10 CALL OUT; *TM= I.lES%:
*PH STEP CHANGES; *TIME = O + l8OOO*5 CALL OUT; *TIME = 9000 1 CALL PH 1 RESTART; *TIME = 90002 + 54000*5 CALL OUT; *TIME = 3.6 1ES CALL PH2 RESTART; *TIME = 3.62E5 + 7.2E4*5 CALL OUT; *TIME = 7.23E5 CALL PH3 RESTART; *TIME = 7.24E5 + 4.32E4*5 CALL OUT; *TIME = 9.4 1E5 CALL PH4 RESTART; *TIME = 9.42E5 + 3.6E4*5 CALL OUT; *TIME = 1.123E6 CALL PH5 RESTART; *TIME = l.lNE6 + 2.88E4*5 CALL OUT; *TIME = 1.27E6%;
*RTF ZINC TIME; *TIME = O + 1.ME4 * 25 CALL OUT; *TIME = 3.7E5 %;
*IPSN TIME; *TIME = 2.16E5 CALL OUT; *TIME = 2.1 7E5%; *TME= O + 4032 * 25 CALL OUT; *TIME = 1. LE5%; *RTF STANLESS STEEL; TIME = O + 54000* 10 CALL OUT; TLME = 54000 1 CALL PH2 RESTART; TLME = 540002 + 396OO* 10 CALL OUT; TIME = 936003 CALL PH 1 RESTART; TLME = 936004 + 28800 * 5 CALL OUT; TIME = 1080005%;
"ACCIDENT; *TIME = O + 360 * 10 CALL OUT; *TIME = 360 1 CALL PH 1 RESTART; *TIME = 3602 + 360" 10 CALL OUT; *TIME = 7202 CALL PH2 RESTART; *TIME = 7203 + 360* 10 CALL OUT; *TIME = 10804 CALL PH3 RESTART; *TIME = 10805 + 36O* 10 CALL OUT; *TIME = 14406 CALL PM4 RESTART; *TIME = 14407 + 36O* 10 CALL OUT; *TIME = 18008 CALL PH5 RESTART; *TIME = 18009 + %O* 10 CALL OUT; *TIME =2l6lO %; **. I BEGIN; STOP; A.2 References for FACSINiILE Model
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115. V. W. Truesdale "Kinetics of Disproportionation of Hypoiodous Acid at High pH,
with an Extrapolation to Rain Water" J. Chem. Soc. Faraday Trans. 93, 1909-
1914, 1997. A.3 Summary of Modelied Reactions and Kinetics
A.3.1 Aqueous Reactions
~eaction r~eaction 1 Rate Constant (M%')' 1 E. IRef. 1 Number (J~OT'KI) Al OH + OH + H202 1.87~1~'~*e'"'~"~ 3700 [631 3 .88x 1O "e[-'2m'(R3mtp A2 OH + e'+ OH' 1) 12600 [64] 3 23x1 O 12e'-"mi(RnMP)) A3 OH+H+HzO 12600 1641 A5 OH + HO2 + H203 6.00~1o9 1661 A6 OH + Oz-+ OH*+OZ 1.3 8x 1~"*e'-"~'"~'~~'~)) 17600 Lw A7 OH 03-+ HOZ+ 8.50~1o9 Lw A8 OH + HzOr+ HP + 0i + 8.47~10~*e'-'~~'(~œTEMP)) 14000 WI ET 8.32~ TE'tP)) A10 OH + Hi+ H20+ H 1~~~*e~*'~~'~ 19000 [681 AlOA OH +O3+ HOt+O1 1,!x1o8 [69I
OH- A27 0*+Oi+02+OH-+OH. 6x10' ~761 A28 0-+O3-+Ot-+O2- 7.00~1o8 1761
2 For second order reactions (A + B -r C + D). For third order reactions uni& are M*s-'. A32 0' + Hz+ H + OH- 8x 1o7 Lw A33 HO- + HO2 + HzOz+ O2 3.98~1o~*&-'~"~ TE"P') 20600 LW
' OH' I I I 1 A37A 03-+ H+ + HO3 5.2~10" [go]
A37B O3*+H*+OH+O2 9~ 1 O" 1811 A38 HIOl+ H + HO; 3.6~1O-' C66I A39 H + HO; + H202 zx 1Ol" WI A40 H-0+ W + OH' 1.98x10-~ 1661
A4 1 H' + OH-+ H20 1o~~~(-EWI(R*TEMP)) 12600 A42 OH +OH'@ O' + HtO kf= 1.3~10'~ kr = 9.4~10'
OH' A48 H0~+0,-tOH+02+02 1x10' [791 A49 O3+ OH--+ O2+ HO; 7x10' [79,97)
P81 18840 Based 40400 on [IO01 PSI 6700 Based on 120H'+ HzOzt, I' + IOtH+ H20 IOtH + OH' + O2+ H20+ 1-
Iz+OH+HOI+I Iz + e- + 1.1' it+H+Iy+W 02-+I + 1-+O2 *speculated reaction O< + O:!
02-+ 102 -, IO?'+ O:! Iz' + OH + I2 + OH' r + o- -+ IO-? A92 H02+Ii+G+H0< lxlOfO [87] A93 IO? + 102+ H~O+ IO; + 4.64~10~ [ 1041 lOlH + tf A94 IO?+ OH -+ 10~' + K 2x1 0' 'Lin, k estimated, 2e9 recomrnended, 2e8 originally A95 IO3'+ e- + IT + HI03- 7. LX~O'*(H~ [92] I t I I I I
A96 IO3*+ 0; + HIOt' + O? + 5x10'' OH' * 1e5 by Paquette, 5e4 recommended A97 IO3' + H + 9.5~1o7 * Paqueîte A98 Hi03'+ HI03*+ I07H + 6x10' * Mezyk IO3*+ OH- Al00 I02H + IOzH + Hc + 103' + 25 [ 1051
* from SIMS Mode1 A142 NO3+HzO2-tN0<+H-+ 1.9~10~ 1791 HO:! A143A NO2 + OH -> H' + NOi- 1.3~1O' PI A143B 1.3~10' [79] A144 HNOt + OH + NO?+ Hz0 1791 A145 NO; + OH + NOz + OH' 1x10~~ [791
L Ai51 NO3 + HOz -+ NOi + K + 4.5~10' Est. by 02 [791 A152 NO3 + O?' + NO3-+ O? 1x10' Est.by [79] A157 10; + H202+ IO3-+ H20 6x10' 111 kf= 1x10'~ kr = I x 10" assume 1x10'~
OH + HO1 + HOIOH
HOIOH + H1O+ IO 120H'+ 120H' + IO2-+ H* +H-+I-+I'+I' 120H-+ HOI + IOz'+ H*+ H-+I'+ 1-
I;+H+I-+I-+H+ e' + HO2 + HO; N+OH+H+NO NO+02+NOZ+0 NOz- + H + NOz + OH' NO3' + H + NO3+ OH' NO+NO+Ot+N02+ e' + H20+ NO3- -P NO2 + OH' + OH-
A.3.2 Gaseous Reactions
Reaction Reaction Rate Constant (M%')' Number GI N< + HzO + HzOv + Nz G2 K + HzO + H20'+ N 1AOX 1 O" G3 Ozt + Hz0 + HzO' + 0: 1.00~10~~ G4 O' + H20+ HzO' + O 1.40~10~~ G5 H20' + Hz0 + H30' + OH 7.20~10" G6 N2'+02 + Nz +Oc 2.50~f 0'' G7 e-+O2 + O< 1.9~1 O"'
G8 H+02+M+H02+M 1 .05x 1 09e's25TEEIIP) G9 0+Or+M+03+M 1.63~1 O~(TEMP/~~~)"+~ GIO o~+o+o~-+o~ 1.1 4x I ~~~e'-~~~~~~~' GIL NO + OH + M + HNO? + M 2.6% IO"(TEMP /298)-2-J G 12 NOI + OH + M + HNO, + M 3.78 1 x 1 ~"(TEMP1298)~." x e(-55 1 .JCIZMP) G 13 NOa + OH + HO2 + NOz 1.6~10'" G 14 NO+O+M+N02+M 7.1 25x 1 ~''(TEMP /298)-'+"' x
' For second order reactions (A + B + C +D). For third order reactions uni& are M*S-'. m0~+ NO3 + HN03+ NOz NO3 -+ NO + O2 NO1 -+ NO, + O 02 +N*+O2+N, HI+OH +HzO+I 0H+12-+HOI+I OH + HOI + Hi0 + IO
Temp S 373 ( 1 .73x 1 O-" e('020fT'EMP' -
(2sx IO-^' + 1x 1u30x (Px t 0 1 .325/(R4TEMP)))) x 6.022~l O"/ 1000 Temp>373 9.92~10' (2.5~10-'~+ lxl~"~x (Px L O 1.325/(R*TEMP)))x 6.022~10~/1000- KG1 18C (0.05)(6.022~1 ou/ 1000) x ( ,731 O-t~e~~~~~m~~~
02- + N23 NO- + NO N2++ NO + NOt + N* O*' + NO + NO'+ 01 NO'+e'+N+O G129 OZf+e'+0+0 1 .2xl0l4 Lw G130 01'+0~+0+0+0~ 1.2~10" 1231 G131 ~c+e-+N+N 6.02~10'~ i23 1 G132 Nzc+Ot-+~+~+02 1.2~1ois C231 G133 03- + NOi -+ NO2-7- O3 4.2~10" f23I G134 NO- + O2+ 02*+ NO 5.4~10" 1231 G135 02-+O3+o3-+Ot 2x10~~ 123 I G136 NO; + O3 + No3-+ O2 6x 1 0' 1231 (3137 N+03+NO+02 3.4~10" VI GI38 e'+NO+M+NO'+M 4.7~1oL0 [23 1 G139 03-+ NO -+ NO< + O2 4.8~1 O' l 1231 G140 N+O+M+NO+M 3.7~10' [231 G141 02+NO+NO+N02+NOr 3.6~10' 1231 (3142 0; + NOi' + O?+ NOz 6x l O" [O01 (3143 NO?' + NO' + NO? + NO 1.81~10~~ [6OI Gt44 02- + NO++ 0, + NO 2.41~10'~ r601
G154 N0i+ N205-+ NO,' + NO?+ 4.2~10" FI NO2 G155 OH + NIO + HO2 + NI 2.29~1 O" 1611 . (3156 OH + HNO + H20+ NO 9x 1 o9 1 [131
02 G165 N'+023N+O< 2.03~10'~ C61 G166 N'+02-t~O'+0 1.8~10'~ FI Gt67 N'+02-+or+~o 4.06~ 10'' FI Gt68 N'+N2+N3' 7.2~1 O" 161 G169 N,'+02+NOC+O+N2 2.26~1 O 'O VI G170 N3- f O3 3Nolt N2 3.0x10'~ FI G171 NO2' NO + NO' + NOz 1.7~10" FI G172 NO' + NtOJ+ NO: + NO2 + 3.54~10" NO? A.4 Summary of Amendments to Aqueous Mode1
Rxn. Reaction New Mode1 New Mode1 Original # (T = 298m iModel [l21 (T = 298K) Al OH + OH -+ HQ2 1.87~10~~*e'"'"'~' 4.2~1o9 5.5~10" A2 OH + e-+ OH' 3.8gx 0 12e(-l'600"R 'TEMP)) 2.4~IO" 3~ 10" O 1Ze(-12m4"TLW) A3 OH+ H + Hz0 3 ,23x 2~ 10Io 2.5~10" A5 OH + HO2+ H203 6.00~10' 6x10' 6x 10" A6 OH + 02.+ OH.+ 1.38x 1013*e"17600'~R*TEMP" 1.13~10'~ 1 8x10' 1
Removed Removed 7.5~10'
d 3.9~10' 4.2~1o7
l.lxloY 1.1~10"
+ OH' A 12 e- + H + OH-+ Hz 2.47~ ' 3.4~10'~ 2.5~1O" A13 e-+O-+OH-+OH-2.20~10" 2.2~101° 2.2~loiO Al4 e-+o<+HO;+ 1.30~10'~ 1.3~10'~ 1.3x101' OH' A 15 6 + -, OH + 7.28~10"*e'*'~'~~~ OH- w A16 e'+HOi+O-+ 3 SOX10' 3.5x10Y 3.5~10' 0' + 0' + H202+ I A26 I OH' + OH' 1 1.29x108
+ oz *A34 HO2 + O< -, Os+ Removed Removed
1 A36 03-+H20+02+ 1~10'~ 1x10" OH + OH' L A37A O< + H'+ Ho3 5.2~10" 5,2x10'~ A37B O;+ K -, OH -+ 9x10" 9x10'~ 5.2~10"
o2+ OH- A48 HO2+O3+OH+ 1x10~ 1x10~ O*+ 01 A49 03+OR+02+ 7x10' 7x10' HO; Iz + H + Iz- + H+
*meculated reaction 2.6~1 OY 5x 10l0 * Modified WOI- 1.6~10''
2~ 1o9 *Lin, k estimated, 2e9 recornrnended, 2e8 originally 7. lxloY*[~
5x10' * 1e5 by Paquette, Se4 recornmended - - 9.5~lor * Paquette A98 HI03' + HI% + 6x10' * Mezyk I02H-t IO3' + OH' 101' + H20z+ IO,' + H20 IO+ IO+ HO1 + 101' + H' 1*+Oj+HOI+02 O*+OI-+10+ OH' kf= 1x10~~ kf= MO'' kr = 1x 10" assume kr= 1x10'~
OH + HO1 + HOIOH A 168 e' + HO1 + KOI' A169 HOIOH+HzO+ IO A176 1 l+uo2+Hoi A177 N+OH+H+NO A178 NO + O2+ NO-+
A181 NO+NO+07+ NOI + NO2 A182 e-+U20+N03'+ NO2 + OH' + OH' AI83 H+NO?-+e-+ NO + OH'
to Gas AS Summary of Amendments Mode1 .c
bu.# Reaction Rate Constant New Mode1 Original Mode1 (Mis-') (T = 298K) [Evans]
Order Reaction)
3.78 lxlol'( TEMP /298)4"." (-55 1.JtlEMP) .Y e 1 Order Reaction)
3.3 1x10~~ 1.6~10' (2"" Order Reaction) 5.1 1x10'~ 1.3~IoY (2' Order Reaction) 5.86~10' 5.84~10'
NO3 NO2+ O 0.2 N03+CO+NOr 2.4l~l~' + COr
Hm0 N+N+M+N2+ 5.7~10' 1 x 10' (2" Order M Reaction) OH + OH + M -1 2.9~~~"(TEMP 1298)"~~ 2.9~1 O' ' 1.8~1 oY (rd H202+ M Order Reaction) OH + OH + HzO + 2.53~I ~~e'*~~~~"~) 1.13~10' 1.14~10~ O OH i HO^ -, H~O 2.89~10'~e'""~~~' 6.69~10" 6.62~10" + o2 OH +O + 0,c H , 1.39x101'e'l' 1 + I+ M + I~+ M 2.36~10~e['~~-~) 2.96~10~ 1 .Oxlo10(2nd Order Reaction) N?' + II -+ + 1 -+ 1x10~ 1x10" 1
HO:! O+I2-,10+E 8.4~1 0" 8.43~IO" 0+10+02+1 9x10~~ 1.81x10'~ I+O~+IO+O~ 1.2ix10~~e'-"' r2+oi+ro+r+ 9x10.'
- Io+Io2+1203 ~xlo~ 1x10~ H+12t,HI+I kf= 3.97~~o"~(-X~~MP' kf = lxlo7 (- 18685iTZMP) kr = &02x 10 1 1 e 3.71~10" Forward Reaction Only
4.71~10''~ H + HO1 -+Hz+ 5x10" 5x 101° Temp 1 373 (1 .73x 10-12 e(lOZOmMP) - (2.5~10-"+ 1x10~~~x (Px 1O 1.325/(R*TEMP))))x (6.022~1 O"/ 1000) Ternp>3 73 9.92~10' (2.5~10-"+ lx10"'~ (Px 10 1.325/(R* TEMP))) x (6.022~loz3/ 1000) - KGIMC 0.05~6.022~1 O? 1000 'r 1 ,73xL~-Ee( IO'OmMP) 9x 1 o8
N2-+0i+N+N + 02 03-+ NOI + NO; + 03 NO'+02+ O<+ NO O;+ o3-) 03-f 02 NO; + O3+ NO3- + 02 N+03+NO+02
O + N2 N3- + 0, -t NO2' 3.0~10'" N2 NO2'NO+NO0+ 1.7~10" NOz NO' + N20S+ 3.54~10" NOr- + NOî, + NO2 03'+ NO2+ NO3- 1 .ZX 10"
NO:!+ NO NO- + NO; -+ 1.2~1 oi5 APPENDIX B
B.1 Rate Constants for Selected Iodine Species
~andHand07+I+I'+~0~+~~
Reactions A84 and A72 were added to the new reaction set and are expected to impact iodine chemistry in the basic and acidic regions, respectively.
O< + O? [A841
Hr02+I+I'+H02+H- [A721
The reaction of O? + O2was adopted from the report published by Dickinson and Sims
[67] to account for the loss of the superoxide in alkaline solutions containing iron. The reaction of hydrogen peroxide with atomic iodine was obtained from the reaction set published by Burns and Manh [23].
B.2 Temperature Dependent Rate Constants Temperature dependent rate constants for iodine reactions are not abundant. Dickinson and Sims [67] report the activation energy for a srnall subset of iodine reactions.
Assuming Arrhenius behaviour, these values were used to estimate a temperature dependent rate constant. However, without the original source for the activation energies, the expression developed is assurned applicable over the temperature range being investigated. Table B.1: Tem~eratureDe~endent Rate Constants Reference Reaction Rate Constant 3 1~7112 + HO; O IOzH ki = 2.6~1oL1exp(- 16000/(~*~)),
HO1 + HO? + k = 1.3~1OLLexp(- 1~ooo/(R*T)) IO7H + OH'
k, = 8.9~10 ' 'exp(-40400/(~*~)) 2 + OH- IIOH* kr = 1.2~10' 'exp(- 12500/(~*~)), 7k, = kr/l.6xlo4 (k, determined using &, published by Lengyel et. al. [2] , which assumes K, to be independent of temperature. Neither a reverse Ea nor K, for this reaction was provided in r 11).
B.3 Iodine Hydrolysis The kinetics goveming iodine hydrolysis has caused some debate. In [50], Burns et. al.
focus on determining a temperature dependent equilibrium constant for iodine hydrolysis.
In addition, they provide the rate constants at elevated temperatures for the recombination
of HOI. The mechanisrn of hydrolysis was presented as:
Iz + HzOo HOI+ 1' + H' [A62A]
HOI+HOI~IO~+I-+H+[A67A]
HOI+IO~~IO<+I-+H'[A1031
The experirnentai conditions included the use of boric acid solutions to maintain a
constant pH, as the authors admitted that pH mut be accurately known to determine the
equilibrium constant of iodine hydrolysis. The results published for the recombination of HO1 and I2 hydrolysis were at pH 5.6. The equilibrium expression was not useful to the model, since one of the fonvard or reverse rate constants as a function of temperature is required. In addition, since these authon have only considered one pathway to It hydrolysis, the equilibrium constant measured probably represents the overall stoichiometric reaction. in both Lengyel et. al. [68]and Truesdale [69]the reaction mechanism of iodine hydrolysis involved the formation of HO1 through 120H' initiated b y:
I2 + HzO 120H'+ H' [A62B]
Truesdale et. al. [S 11 performed a detail study on the effect of pH on the entire mechanism of iodine hydrolysis. Their results were incorporated into the model since they presented a more complete reaction mechanism than Burns et. a1 [50]. Furthemore, the effect of pH on the recombination of HO1 was more prominent than that of temperature. The reaction of HO1 + HO1 [A67A/B] has traditionally been reported as an equilibriurn reaction, however Tnisesdale et. al. [5 11 suggest that the reverse reaction would only bear any importance below pH 5.5. Therefore, the reverse reaction was only included for pH below 6. At a pH below 6, the room temperature rate constants for reaction A67A and B reported by Burns et. al [SOI were used. However, the temperature effect was not included.
B.4 Henry's Law Coeficients Vogt et al. [70] reported a compilation of Henry's coefficients applicable to the model, however these authors did not experimentally determine them. In addition, it was assessed that HI, INOz, l'NO3 and IzOz are highly soluble in water with a Henry's coefficient at a,since once these species enter the aqueous phase they quickly dissociate. To incorporate this into the model, a very high Henry's constant was selected (50000) and a high rate constant was arbitmily chosen for the dissociation of these species into the aqueous phase.
19 HI + IT + 1- kr= 1x10 S-1 k,= 1x10'~M-'s" [A1611
NOz + HzO + HO1 + HN02 k = lx101° M%' [A 1621
NO3 + HzO + HO1 + m03 k = 1x10'~M%' [A 1631
IzOt + H20 -+ HO1 + IO2' + K' k = lx 10" M*'s-' [A 1641 C.1 Kinetics of OH + I2
The reaction of OH + Iz + products (G102)was most recently studied by Loewenstein
[71], who reported two product pathways, namely: OH + I2 -t 1 + HO1 and OH + Iz +
IO + HI. At room temperzhire the second pathway was considered negligible, which was verified experimentally. Since a temperature dependent rate expression was not . determined, only the first pathway was assumed to occur. However, at elevated temperatures the second pathway may become significant. Pending future experimental work, this reaction should be re-evaluated.
C.2 Kinetics of I2 + O3
The reaction of Iz + o3+ products (G 1O9A G 109B), reviewed by Vikis and MacFarlane
[30], has two possible charnels of occurrence: It + O3-t IO + I + O2and i2 + Oi+ IO +
IO2. The second path was deemed energetically more favounble as it is estimated to be less endothermic [72], however the actual branching ratio was not detemined. An overall temperature dependent rate expression was reported as, k = 5.75~10 7* e(-ISOOO/RT)
[293-3701. The rate constant at room temperature based on this expression is
2x1o3 ~*rno~'*s-'which is lower than the original value of 9x io3 mol-'*s-' from
Evans [35]. Assuming a branching ratio of 30% for the first charnel and 70% for the second and adopting the temperature variant rate constant caused a reduction in the elimination rate of iodine at STP conditions. No eEect was observed for higher temperahires. The original value was unaltered since more data is required to obtain a definitive value. C.3 Kinetics of IO + IO
The reaction of IO + IO -+ products (KG1 18A KG 118B KG 1 18C) has been evaluated by
Sander [72], Martin et. al. [73], Lazlo et. al. [74] and Harwood et. al. [75]. Harwood et. al. [75] rnost recently studied the kinetics of this reaction and proposed four possible reaction pathways:
10+IO+Iz+O.,
I0+IO+I+I+O1
IO + IO + 1 + IO2
10 + IO + I2O2
The authors did not observe statistically significant temperature dependence for the overall rate constant, over the range of 250 -373 K, contradicting the work by Sander
[72]. However, insuscient information was provided regarding the branching ratio and therefore appropriate rate constants could not be eluded. The publication by Sander [72] was most thorough enabling for an expression for each pathway to be calculated. Unlike
Harwood et. al. [75], Sander [72] only reported 3 product pathways, namely:
1O+I0+I+I+O2 (a)
10 + 10 + [?O2 (b)
IO+IO+r2+o2 (cl
It is not expected that Iz02 will be stable and therefore the products of this path were assumed to be I + IOz. The specific rate constants were determined using the following relationships: kovera~i= ka + kb * kc kb+kc=2.5x10-11+l.r10-30[~/~*~]cm 3 molecules -1 s -1 k, = 0-~~~k*verafl)
Where P = Pressure (Wa)
R = L'nivcnal Gns Constant (5.3 14 .!mol-' K1)
T = Temperature (K)
This approach results in a negative rate constant for G 1 18A at temperatures above 373 K.
Therefore, the value was fixed at 9.92~1 o8 mol-'s" for 'P373 K.
C.4 Kinetics of HOz + IO
Finally, the reaction of HOr -+ IO + products (G 124A G 124B) has been recently investigated by Cronhite et. al [76]. These authors reported four product pathways with a temperature dependent expression for the overall reaction. However, the branching ratios remained undetermined. Therefore the room temperature rate constants, originally obtained from Jenkin et. al. [77] and Maguin et. al. [78] were used. The first two conditions for maximum ozone concentration, as described by Willis et al.
[32], requires the complete charge transfer of and the subsequent neutralization of
Ozt yielding O atoms. This process require two e- and as a result 2G(e) was accounted
for in the G(Oi) calculation. The results in Table D. 1 suggest that the mode1 also predicts
the complete charge transfer of N21 to 0; However, from Table D.2,the OzTprimarily
reacts with N2 and NO. Therefore, the contribution of ionic precursors has little effect on
the initial ozone concentration. Wiliis et. al. [32] also note that at low dose rates ion
recombination is slow.
Table D.1: Weighted Contributions of Important Reactions
% Nt' Reaction Reac tion Modeiled
Result ,
% N Reaction [ Reaction 1 ModelledResult 1 % N>+Reaction 1 Reaction 1 Modelled Result 1
Table D.2: O*' Reaction Pathway
% 0,' Reaction 1 Reaction 1 Modelled Result 1
Table D.3: N+ Reaction Pathway
%vReaction Reaction Modelled Result N'+O~+N+~; 29 N'+o~+NO++O 126
The third condition requires that N react partially with 02and partially with NO disabling the reaction of NO with 03.At low dose rates, the authors predict lower ozone yields because N atoms no longer contribute to the ozone yield. They suggest that the O atoms formed through N + Oz produce ozone which is subsequently consumed through the reaction of NO + 03.The initial yield measured in Figure 5.19 corresponds to an absorbed dose of 1.2 Gy. At this point sufficient concentrations of NO have not accumulated for the reaction of NO + O, to bear much significance. Therefore, in addition to the O resulting fiom the radiolysis of oxygen, the O formed fiom reactions of
N with NO and O2directly produce ozone. Finally, one more source for O radicais was established in the mode1 analysis not descnied in the Wills et. al [32] scheme. Reactions of bf ions, presented in Table D.3, also contribute to the initial ozone yield. Figure D. 1 best describes the overali mechanism of ozone formation.
Figure D.l: Initial Ozone Formation Mechanism
Based on these findings the G value can be estimated as follows:
Wzere: ~(x)'= G value for O under a pure oxygen system and N under a pure nitrogen system W, = weight fraction of species x E, = mass attenuation coefficient for species x
Under moist air conditions, the O directly produces ozone while the nitrogen atom reacts with oxygen increasing the yield of O radicals. An upper limit G(03)can be estimated as: