ASTEC V2 severe accident integral code: Fission product modelling and validation

Nuclear Engineering and Design 272 (2014) 195–206

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ASTEC V2 severe accident integral code: Fission product modelling and validation L. Cantrel ∗ , F. Cousin, L. Bosland, K. Chevalier-Jabet, C. Marchetto Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES/SAG/LETR, B.702, Centre de Cadarache, BP3 13115 Saint-Paul-lez-Durance Cedex, France

a r t i c l e

i n f o

Article history: Received 2 July 2013 Received in revised form 29 July 2013 Accepted 18 September 2013

a b s t r a c t One main goal of the severe accident integral code ASTEC V2, jointly developed since almost more than 15 years by IRSN and GRS, is to simulate the overall behaviour of fission products (FP) in a damaged nuclear facility. ASTEC applications are source term determinations, level 2 Probabilistic Safety Assessment (PSA2) studies including the determination of uncertainties, accident management studies and physical analyses of FP experiments to improve the understanding of the phenomenology. ASTEC is a modular code and models of a part of the phenomenology are implemented in each module: the release of FPs and structural materials from degraded fuel in the ELSA module; the transport through the reactor coolant system approximated as a sequence of control volumes in the SOPHAEROS module; and the radiochemistry inside the containment nuclear building in the IODE module. Three other modules, CPA, ISODOP and DOSE, allow respectively computing the deposition rate of aerosols inside the containment, the activities of the isotopes as a function of time, and the gaseous dose rate which is needed to model radiochemistry in the gaseous phase. In ELSA, release models are semi-mechanistic and have been validated for a wide range of experimental data, and noticeably for VERCORS experiments. For SOPHAEROS, the models can be divided into two parts: vapour phase phenomena and aerosol phase phenomena. For IODE, iodine and ruthenium chemistry are modelled based on a semi-mechanistic approach, these FPs can form some volatile species and are particularly important in terms of potential radiological consequences. The models in these 3 modules are based on a wide experimental database, resulting for a large part from international programmes, and they are considered at the state of the art of the R&D knowledge. This paper illustrates some FPs modelling capabilities of ASTEC and computed values are compared to some experimental results, which are parts of the validation matrix. © 2014 Elsevier B.V. All rights reserved.

1. Introduction The ASTEC (Accident Source Term Evaluation Code), jointly developed since several years by the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and the German Gesellschaft für Anlagen und Reaktorsicherheit mbH (GRS), aims at simulating an entire Severe Accident (SA) sequence in a nuclear water-cooled reactor from the initiating events to the release of radioactive substances out of the containment. The main ASTEC applications are therefore deterministic and probabilistic accident evaluations of SA consequences including PSA2, assessment and improvement of SA management procedures and contributions to emergency preparedness and to definition and efficiency assessment of SA consequences mitigation. ASTEC is designed to cope with any accidental situation in any nuclear installation, a capability which

∗ Corresponding author. E-mail address: [email protected] (L. Cantrel). 0029-5493/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nucengdes.2014.01.011

interest has clearly been reinforced by the Fukushima-Daiichi accidents. Nevertheless the level of accuracy of models is variable and the phenomenology of interest is of a particularly complex nature. ASTEC is thus also used in a coupled way with the uncertainty analysis IRSN tool SUNSET to characterise the phenomena that deserve additional R&D efforts and then to quantify the influence of models improvement. Predicting the SA consequences imposes to predict the amount and chemical speciation of all the radionuclides that can be released to the environment, the so-called “source term”. Due to the high reactivity1 of most of the fission products (FPs), predictive evaluations of the source term can only be reached by accounting for the complex physical and chemical phenomena affecting FPs during their transport from the fuel to the environment through the primary circuit and the containment. These

1 That is especially true for iodine and ruthenium that would be the main contributors to the effective dose at short to mid-term.

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2. ELSA module Nomenclature CANDU CANada deuterium uranium (pressurised heavy water reactor) CEA Commissariat à l’Energie Atomique et aux Energies Alternatives design basis accidents DBA ICHEMM iodine chemistry and mitigation mechanisms ISTP international source term programme mixed-oxide fuel MOX NPP nuclear power plants OECD Organisation for Economic and Cooperation Development FP fission product framework programme for research and technologFwP ical development PSA probabilistic safety assessment pressurised water reactor PWR RCS reactor cooling system severe accident SA SARNET severe accident research network of excellence SAM severe accident management SFR sodium fast reactor silver indium cadmium SIC SGTR steam generator tube rupture START study of the transport of ruthenium in the primary circuit source term evaluation and mitigation project STEM

phenomena have been the subject of many R&D international programmes whose results have been exploited to develop models capitalised in the ASTEC code. Validating models for such a complex phenomenology imposes adopting a validation strategy based on both separate-effect experiments and integral experiments. The ASTEC integral code is composed of a dozen of coupled modules, each one addressing a key part of SA phenomenology. This modularity clearly makes easier the implementation of this mixed analytical and integral validation strategy. This paper focuses on the validation of the three modules directly devoted to FP behaviour. The first one is the ELSA module whose aim is to predict release of FP from degraded fuel matrix and of the core structure materials; the second one is the SOPHAEROS module whose objective is to model transport and reactivity of FPs as well as of structural materials, and the last one is IODE which models the chemistry of iodine and ruthenium inside the nuclear containment building. The CPA models (AFP part of the CPA module, coupled to CPA-THY sub-module for thermal-hydraulics) of aerosol transport and depletion inside the containment, based on the poly-disperse MAEROS model (Gelbard, 1982), are not addressed in this paper because some complete references can be found elsewhere (Kljenak et al., 2010). This paper briefly describes these three modules and presents their main validation matrix. Due to the multiplicity of involved phenomena of interest and thus of models to validate, these matrices are large and for each module, only one comparison between simulation and experiment is provided for illustration and discussed. All the models implemented in ELSA/SOPHAEROS/IODE have been, for most of them, developed in declining, in complement to experimental databases, some mechanistic approaches performed with the support of advanced tool as for instance the MFPR software (Veshchunov et al., 2006) or of theoretical chemistry tools for condensed phases as for gaseous phases. ASTEC FP models are today close to the state of the art.

2.1. Overview of models ELSA, which deals with FPs and structural materials release from the degraded core, is tightly coupled with the ICARE module which treats the phenomena of the core degradation. Usually the FPs released from the fuel are classified into three groups: the volatile, the semi-volatile and the low-volatile ones. Among volatile FPs, we can find for instance noble gases, Iodine and Caesium isotopes; among semi-volatile FPs, we can cite Molybdenum and Barium isotopes; among low-volatile FPs, we can cite Uranium or Strontium isotopes for instance. Release of structural materials, mainly from control rods, is also considered. It is worth noticing that ruthenium behaves as a low volatile FP in reducing conditions whereas it has been evidenced to be released in large amounts when the fuel oxygen potential is high enough (air-ingress scenario, MOX fuels) (Giordano et al., 2010). A special attention is thus also paid to the modelling of Ruthenium release (Brillant et al., 2010). For volatile elements, the release kinetics is governed by a ratelimiting process of solid-state diffusion through the fuel matrix. For other elements, the vaporisation rate is the limiting process and depends on the chemical species formed in relation with its vapour pressure as well as the mass transfer rate from fuel to gas stream. Models related to low-volatile FPs have been recently reviewed (Brillant, 2011) whereas analytical models for Molybdenum and Barium, whose releases greatly depend on atmosphere composition, have been improved (Brillant, 2010). Models are briefly described below but more details are available in (Brillant et al., 2013a,b). a) Volatile species: - Release is described by species intra-granular diffusion through UO2 fuel grains, taking into account fuel oxidation (UO2+x ) and a grain-size distribution. - Tellurium, selenium and antimony can be partially trapped in the cladding, depending on the temperature and on the degree of cladding oxidation. - At the fuel melting point, all the remaining species located in the liquid part of the fuel are supposed to be instantaneously released. b) Semi-volatiles species: - Release is described by evaporation into inter-granular porosities and mass transfer processes. c) Low volatiles species: - Release is described by fuel volatilisation treated as the vaporisation of UO3 . This process can therefore take place only in case of high temperature degradation of the fuel rods. The difference between the configuration of fuel rod and debris bed is the determination of the average geometrical “surface/volume” ratio used in the calculation of the stoichiometry deviation. Concerning the molten corium pool configuration, given the high-temperature conditions, the chemical equilibrium can be assumed in the magma so that release is governed by mass transfer and evaporation processes from the free surface of the molten pool. Central to the modelling is the calculation of the vapour pressures of the elements in the molten pool. The assumption of non-ideal solution chemistry is also used for phase distribution. Finally, for the structure materials, releases of silver, indium, cadmium, tin, iron, nickel, and chromium are taken into account in ELSA as follows:

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Table 1 Main validation matrix for ASTEC/ELSA. Experiments

Main phenomena involved

VERCORS HT and RT (Ducros et al., 2001) MCE and HCE (Cox et al., 1991a,b; Barrand et al., 1999; Dickson et al., 2001) EMAIC (Rabu et al., 1999) HEVA (Le Marois, 1987–1989) ORNL HI and VI (Domagala et al., 1991) Phébus.FP (Drosik et al., 1995)

Releases for fuel pellets under steam or hydrogen carrier gas, different burn-ups, re-irradiated fuel pellets Releases from CANDU fuel fragments, under steam or hydrogen carrier gas, low bun-up SIC control rod releases Releases for fuel rods under steam or hydrogen carrier gas, different burn-ups, re-irradiated fuel Releases for fuel rods under steam or hydrogen carrier gas, different burn-ups, no re-irradiated fuel Integral tests (release from a 20 fuel rods bundle)

- Ag, In, and Cd (SIC alloy) are released from degraded control rods. The same approach as semi-volatile species is used, i.e. release is described by evaporation and mass transfer processes. The SIC release happens at the control rod failure. It is followed by release from free surface of the control rod and its molten alloys during their candling along the rod external surface. - Fe, Ni, and Cr are supposed to be released during the candling of steel materials, using the same approach as for the release of Ag, In and Cd. - Sn kinetics release is supposed to be proportional to the rate of ZrO2 formation, as lessons drawn from observations in the Phébus.FP integral experiments (Grégoire and Mutelle, 2012). These structure materials can also be released from the corium molten pool. For B4 C control rods, releases of Boron and Carbon are not managed by ELSA but obtained from the boron carbide oxidation model of the ICARE module. 2.2. Validation matrix The main validation matrix is provided in Table 1. The French VERCORS experiments were performed by CEA using pellets including cladding extracted from used rods of French PWRs. Fuel was UO2 or, to a lesser extent, MOX. Most of the time, the fuel was re-irradiated to follow FPs with short life. The Canadian MCE (metallurgical cell) and HCE (hot cell) programmes were composed of a total of 30 separate experiments (Andrews et al., 1999) which examined influence of burn-up, of thermal conditions and gas composition on the FP releases; these experiments were conducted on bare fuel fragments and shortlength fuel specimens with Zircaloy cladding derived from spent CANDU fuel. The four EMAIC experiments, conducted by CEA, were devoted to study the SIC control rod degradation. The French HEVA experiments were performed on PWR short fuel rods (4 cm) with their claddings. The burn-up of the fuel was of

36.7 GWj/tU. These tests were carried out in an atmosphere made of H2 O/H2 , excepted for the HEVA 6 where the atmosphere is reducing (only H2 ). ORNL HI and VI experiments were performed with pellets of PWR fuel rods (length ∼15 cm) with their claddings. For HI experiments the burn-up of the fuel used ranged between 10 and 40 GWj/tU whereas for VI experiments the burn-up was higher, between 40 and 47 GWj/tU. The on-going VERDON programme (Ducros et al., 2009), performed at CEA under the frame of the International Source Term Programme (ISTP) led by IRSN, explores the influence of additional parameters, i.e. air-ingress conditions as well as MOX fuel. 2.3. Example of validation: Phébus FPT1 test The extended validation matrix is detailed elsewhere (Brillant et al., 2013a,b) but hereafter some measured release rates from Phébus FPT1 experiment (Jacquemain, 2000; Dubourg et al., 2005) are compared with those calculated. In Fig. 1 the bundle history is displayed and, in Figs. 2–6, releases for some elements are presented. The calculated releases of the volatile elements really start at 9000 s with the increase of the fuel temperature and increase sharply near 11,000 s with the oxidation of the fuel. In the experiment, after 15,000 s, the degradation of the bundle leads to the formation of a debris bed and a molten corium pool. In the calculation, only the intact fuel geometry is considered. The release kinetics, for caesium, iodine, xenon, tellurium, is correctly reproduced by the code and the calculated total release fraction is in agreement with the experimental results (see Figs. 2 and 3) which give a final release fraction of about 85%. However, the Antimony release is not well estimated: 84% calculated final release against 30% measured final release. It seems that the fraction of Antimony trapped by the fuel cladding during the oxidation is underestimated by the code. For semi-volatile elements like molybdenum, as shown in Fig. 4, the calculated final release is overestimated by the code. A possible

Fig. 1. Bundle power and steam mass flow rate test during PHEBUS FPT1 test.

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Fig. 2. Release of iodine and xenon in the PHEBUS FPT1 experiment as measured (EXP) and as calculated with ASTEC.

improvement will be linked to a better prediction of the beginning of significant fuel melting (in FPT1, fuel melting was measured to start at 15,000 s). Indeed, it has been demonstrated that release from a molten pool is significantly lower than from intact fuel (Dubourg et al., 2005). More generally the behaviour of Molybdenum is the subject of R&D programmes such as the ISTP/VERDON programmes. The low amount (few per cents) of released Ruthenium is fairly well reproduced by the code. For non-volatile elements, an underestimation of the uranium release in comparison with experimental data is observed, as reported in Fig. 6. One of the means to improve these results will be to have a better description of the UO3 partial pressure which is a parameter of the UO2 volatilisation modelling. For structure materials, the release of SIC starts a bit too early in the calculation (∼9500 s predicted by the code compared to ∼11,000 s observed experimentally) due to an early rupture of the control rod cladding predicted by ICARE as illustrated in Fig. 5. For the total release, calculated and experimental data are in a fairly good agreement.

Fig. 3. Release of caesium and tellurium in PHEBUS FPT1 experiment as measured (EXP) and as calculated with ASTEC.

Fig. 4. Release of molybdenum and ruthenium in PHEBUS FPT1 test as measured (EXP) and as calculated with ASTEC.

Though some discrepancies exist, which are mainly due to a combination of uncertainties relative to the core degradation models and those relative to the FP release models, the agreement between calculation and experimental results is quite good. 3. SOPHAEROS module 3.1. Overview of models The SOPHAEROS module (Cousin et al., 2008) simulates transport of FP vapours and aerosols in the reactor cooling system (RCS), which is approximated with a 1D series of control volumes, to simulate gas flow to the containment, accounting for the chemical reactions in the vapour phase and aerosol physics, as displayed in Fig. 7. The thermal–hydraulic conditions are provided by the CESAR module of ASTEC (Bandini et al., 2010), based on a 1D 2-fluid 5-equation approach. Using five states (suspended vapours,

Fig. 5. Release of cadmium and tin in PHEBUS FPT1 test as measured (EXP) and as calculated with ASTEC.

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resuspension: the “Force balance” model and the “rock and roll” one (based on the JRC approach). - Dedicated pool scrubbing model to deal for example with the retention of aerosols in the secondary side of flooded steam generators in case of SGTR scenario. A sectional approach is adopted to model the aerosol distribution: the same species composition is considered in all the aerosol size classes. Materials for primary circuits of CANDU reactors are available in ASTEC V2.0, along with the corresponding chemisorption correlations. By default, the RCS axial nodalization (set of volumes connected by junctions) used by SOPHAEROS matches the CESAR one, but it is now possible in ASTEC V2 to activate an user option reducing the primary circuit meshing to be used by SOPHAEROS in order to save CPU time. 3.2. Validation matrix Fig. 6. Release of uranium in PHEBUS FPT1 test as measured (EXP) and as calculated with ASTEC.

suspended aerosols, vapour condensed on walls, deposited aerosols, sorbed vapours), SOPHAEROS uses either a mechanistic or a semi-empirical approach to model the main vapour-phase and aerosol phenomena. a) Vapour-phase phenomena - Gas equilibrium chemistry. The MDB (Material Data Bank) included in ASTEC contains data of about 800 species. - Chemisorption of vapours on walls. - Homogeneous and heterogeneous nucleation. - Condensation/revaporisation on/from aerosols and walls. - Preliminary model for kinetics of gaseous phase chemistry (focusing first on the Cs-I-O-H system), mainly based on the interpretation of the on-going IRSN CHIP experimental programme. b) Aerosol phenomena - Agglomeration; gravitational, Brownian diffusion, turbulent diffusion. - Deposition mechanisms: Brownian diffusion, turbulent diffusion, eddy impaction, sedimentation, thermophoresis, diffusiophoresis, impaction in bends. Deposit of aerosols in a flow contraction (either abrupt one with a 90◦ angle or conical) can be simulated. - Remobilisation of deposits: revaporisation and mechanical resuspension. Two models are available for aerosol mechanical

The main validation matrix can be split in three groups. The first concerns all phenomena linked to aerosol physics, the second deals with the vapour nucleation/condensation and chemical reactivity, and the third is constituted of more integral experiments with some coupled FP transport phenomena. The SOPHAEROS main validation matrix is depicted in Table 2. Phébus.FP experiments have highlighted that transport of Iodine through the RCS is much more complicated than expected with the presence of a gaseous Iodine fraction at the break and a mixture of Iodine vapour/aerosol in the RCS which depends on gas composition and temperature. SOPHAEROS has this capability to perform some chemistry speciation with the thermochemical assumption. 3.3. Example of validation: CHIP test with I, Cs and Mo A SOPHAEROS application is illustrated hereafter by modelling a CHIP test involving I, Cs and Mo in oxidising conditions (Grégoire and Mutelle, 2012). Molybdenum plays a key role (Gouello et al., 2011) on the iodine transport due to its chemical affinity with caesium to form caesium molybdates. The ISTP/CHIP experimental programme (Clément and Zeyen, 2005) was designed to better understand the Iodine transport and its reactivity with respect to others elements. The CHIP experimental line is schemed in Fig. 8. It is an open reactor with a high thermal gradient along the tube (see Fig. 9), and some reactants are fed with controlled flow rates diluted in a carrier gas which is a mixture of hydrogen, steam and inert gas. The maximum temperature, in the furnace, at the reactant inlet points, is fixed to 1600 ◦ C.

Fig. 7. ASTEC modelling of aerosol/FP behaviour along the RCS.

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Table 2 Main validation matrix for ASTEC/SOPHAEROS. Experiments

Main phenomena involved

TUBA (Zoulalian and Albiol, 1998) DEPAT (Saldo, 1996) LACE (Anon, 1988; Wright et al., 1987) TRANSAT (Verloo et al., 1996) STORM (Bujan et al., 2010) ADPFF (Ball and Mitchell, 1992)

Thermophoresis, diffusiophoresis Eddy impaction, resuspension in turbulent flow Eddy impaction, bend impaction Settling, eddy impaction, bend impaction Thermophoresis, eddy impaction, mechanical resuspension Settling, eddy impaction, bend impaction

Vapour

DEVAP (Le Marois and Megnin, 1994) AERODEVAP (Drosik et al., 1995) FALCON (Beard et al., 1992) REVAP-ASSESS (Anderson et al., 2000) CHIP (Grégoire and Haste, 2012)

Condensation and chemisorption Heterogeneous nucleation, condensation and vapour-aerosol interaction Chemistry, condensation and vapour-aerosol interaction Revaporisation Kinetics of Cs-I-O-H system

Integral

VERCORS HT HCE Phébus.FP (Schwarz and Hache, 1999)

Overall phenomenology

Aerosol physics

Fig. 8. CHIP experimental facility.

Downstream the furnace zone, the gas is cooled down in the so-called “transport zone” which has to be as much as possible representative of the material and of the thermal-hydraulic conditions of the primary circuit of a Light Water Reactor (LWR). Chemical reactions take place producing aerosols and gases. Particles and gases are then assumed to be separated at the outlet of the line before being analysed by offline chemical techniques. Aerosols are

collected on filters whereas the iodine gaseous species are collected in gas scrubbers filled with an alkaline solution (iodine traps). The steam is provided by a steam generator that delivers a mixture of steam/He. The operating conditions of the simulated experiment are reported in Table 3. Experimental results show that iodine was mainly released under gaseous form: up to 90% of injected Iodine was collected in the liquid trap, in gaseous form, the main part being molecular iodine I2 and the remaining part likely hydrogen iodide HI. Caesium and molybdenum were mainly retained in the filter under aerosol form. Roughly 27% of caesium and 25% of molybdenum were deposited onto walls of the tube. The CHIP facility between furnace and filters has been nodalised with 40 control volumes with a maximum difference temperature of less than 50 ◦ C between two successive control volumes. A

Table 3 CHIP operating conditions.

Fig. 9. Fluid/wall temperature profile along the CHIP tube.

H2 O flow rate He flow rate Pressure I molar flow rate (under I2 form) Cs molar flow rate (under CsOH form) Mo molar flow rate (under MoO3 form)

840 g h−1 15.1 Nl min−1 (∼162 g h−1 ) 2 bars 1.5 × 10−7 mol s−1 6.04 × 10−7 mol s−1 1.93 × 10−6 mol s−1

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Table 4 Comparison between CHIP experiments and SOPHAEROS simulation. % of injection

Gaseous outlet Aerosol outlet Condensation Aerosol deposition

Iodine

Caesium

Molybdenum

Exp.

Calc.

Exp.

Calc.

Exp

Calc.

>90% ∼3%

94.3 0.55 5.1 0.05

<1% ∼70%

0. 40.0 56.0 4.0

<1% ∼70%

0. 50.8 44.2 5.0

<1%

steady state computation was performed with permanent injection flow rates of iodine, caesium, molybdenum and steam. All models described in Fig. 2 are enabled except chemistry sorption because of lack of data concerning iodine, caesium and molybdenum sorption onto wall materials (alumina and 316 L SS). The gaseous composition is computed with the thermodynamic equilibrium assumption between all present reactive elements (I, O, Cs, Mo and H). Simulation provides that ∼95% of Iodine reaches the outlet under I2 gaseous form (see Fig. 10), a small fraction is under aerosol form and ∼5% are deposited by condensation onto the inner walls of the tube. In a near future, this test will be simulated again activating some kinetics to see any possible influence on the gaseous fraction as well as on the obtained species (HI or I2 ). Table 4 summarises the experimental and calculated element distributions. A good agreement is obtained for Iodine with no CsI formation. For caesium and molybdenum, too high deposits are predicted even if the computation is in agreement with the experimental results on Cs and Mo physical form. Caesium is predicted to be entirely under Cs2 MoO4 species whereas molybdenum is present as a mixture of H2 MoO4 , MoO3 and associated polymers and Cs2 MoO4 . All these species are in aerosol phase at the outlet. In the vapour phase, the first caesium species formed at high temperature is CsOH, but quickly, before CsOH condensation, Cs2 MoO4 and CsI are produced as shown on Fig. 10. Due to high condensation of Cs2 MoO4 (see Fig. 11), Mo/Cs ratio increases as displayed in Fig. 12 resulting in a caesium/iodine ratio decrease, which promotes gaseous iodine formation because Cs is no longer available in the gaseous phase. The general path of formation for gaseous Iodine is consistent with the experimental results. Compared to experimental results, caesium and molybdenum retention is too high in the computation. This disagreement could result of two combined effects: the first one deals with uncertainties on thermal gradient because the accuracy of temperature measurements is lower than 50 ◦ C due to some technical constraints; and the second one is relative to thermodynamic data

∼27%

∼25%

of condensed and gaseous C2 MoO4 which have to be reviewed to check and reduce some possible uncertainties. To summarise, SOPHAEROS reproduces the main trends of the experiment and illustrates the great interest to be capable of performing some chemistry speciation which directly impacts the FPs transport through RCS. 4. IODE module 4.1. Overview of models The IODE module (Bosland et al., 2010) simulates iodine and ruthenium behaviour inside the containment, except for the transport of the associated species that is computed by the CPA module. As radiochemical reactions in the reactor containment involve a large amount of elementary reactions and complex mechanisms, a phenomenological approach has been adopted for ASTEC. Therefore, for Iodine, the IODE module is composed of around 40 phenomenological models that focus on the predominant chemical

Fig. 11. Caesium retention profile along the tube with the two main species.

Fig. 10. Main vapour concentration species versus the tube length.

Fig. 12. Mo/Cs and Cs/I molar ratios along the CHIP tube.

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-

Fig. 13. ASTEC modelling of iodine chemistry in containment.

reactions in the sump, gaseous phase, at the liquid-sump interface and with surfaces (see Fig. 13). More precisely, it describes in a kinetic way (i.e. non-equilibrium) the chemical transformations of iodine in the reactor containment building, taking into account three kinds of processes: thermal reactions, radiolytic reactions and mass transfer processes. The Iodine species involved in the reactions are I2 , CH3 I, I− , IO3 − , HOI and AgI. The methyl iodide is assumed to represent all the organic forms, knowing that CH3 I is the most volatile one. The inorganic forms present in the gas phase are molecular iodine I2 and iodine oxides represented by IO3 − species. The other species are Ag (from in-core control rods), Ag2 O (Ag released and supposed to be oxidised in the containment), Rp and R (respectively initial amount of organics in the wall paints and gaseous concentration in the containment resulting from the paint releases) and O3 formed in the gas phase. Concerning ruthenium, the IODE module focuses on three predominant chemical reactions in the gaseous phase (detailed below). The main Ruthenium species involved in these reactions are ruthenium dioxide RuO2 under aerosol form and gaseous ruthenium tetroxide RuO4 . The phenomena considered can be split into three fields: the mass transfer phenomena, the chemical reactivity in the liquid phase and the chemical reactivity in the gas phase. These three macro-phenomena are briefly described hereafter whereas details and references are available in Bosland et al. (2010). a) Mass transfer reactions: - Adsorption/desorption of molecular iodine on painted, steel and concrete walls. - Mass transfer between sump and gas phase for diffusion/convection processes, based on the interpretation of IRSN SISYPHE experiments. This model is also available in evaporating conditions. - Condensation of steam on the walls and on the sump surface. - Transfer of non-volatile iodine oxides towards the sump. - Effect of spray on molecular iodine: mass transfer between gas phase and droplet, interfacial equilibrium at the droplet surface, liquid mass transfers inside the droplet, chemical reactions in the bulk liquid. The module computes kinetics of the overall process during the droplet fall down and the output information is the rate of capture of I2 for each compartment. b) Liquid phase chemistry:

Hydrolysis of molecular iodine I2 . HOI dissociation/disproportionation. Oxidation of I− by the oxygen dissolved in the sump water. Radiolytic oxidation of I− into I2 in the sump, where oxidation depends on the production rate of OH radicals, and where I2 reduction is temperature-, pH- and [I−]-dependent. - Reduction of iodates by radiolysis into molecular iodine. - Silver iodide (AgI) formation by heterogeneous reactions (both Ag2 O/I− and Ag/I2 reactions are considered, the reaction of Ag2 O with I− depending on the solubility of Ag2 O and AgI). - Formation of organic iodide RI by homogeneous reaction in the liquid phase with the Taylor’s homogeneous model: solvents are released from paint in liquid phase, then oxidised under radiation to form organic acids, and finally RI are formed by interaction between I2 and solvents or sub-products. - Decomposition of organic iodides in the liquid phase, according to two possible destruction processes (either radiolysis or hydrolysis). c) Gas phase chemistry: - Kinetics of ozone (O3 ) formation, which is considered as a surrogate of the air radiolysis products. - Oxidation of molecular iodine into iodine oxides (simplest form iodate) by air radiolysis products. - Decomposition of iodine oxides into organic iodides. - Organic iodide formation, either by an homogeneous model or by a heterogeneous model linked to iodine adsorption onto paint. - Radiolytic oxidation of organic iodine into iodine oxides (simplest form iodate). Concerning ruthenium, its chemistry in the gaseous phase (Mun et al., 2007, 2008) has been implemented in ASTEC V2 in order to complete FP chemistry models inside the containment. The main modelled reactions are: - Decomposition in bulk phase (dry and moist air) of the ruthenium tetroxide RuO4 (g) coming from the RCS into Ruthenium deposits. - Ruthenium ozonation (reaction between Ruthenium deposits and ozone). - Oxidation of ruthenium deposit due to the action of air radiolytic products (revolatilisation from RuO2 surface deposit producing RuO4 (g) at low temperature). 4.2. Validation matrix The main IODE validation matrix is indicated in Table 5. 4.3. Example of validation: P9T1 test in RTF facility The P9T1 test was performed in the RTF facility in AECL (Glowa and Moore, 2009), made of 316L stainless steel (the scheme of the facility is provided in Fig. 14). It was mainly designed to quantify I2 production and pH influence on Iodine chemistry. A solution of iodide ions (I− ) was irradiated, at 60 ◦ C, with a 60 Co source delivering a dose rate of 0.22 Gy s−1 in both liquid and gas phases. I− are oxidised into I2 . The initial iodide ions concentration was set to 6.5 × 10−6 mol L−1 . Over the course of the test duration (500 h), the pH was decreased from 10 to 5 (Fig. 15, right axis) to check its influence on iodine volatility. Experimental measurements were performed in the liquid and gas phases thanks to the sampling loops. In the gas phase, organic iodine was measured even if its presence resulted from organic pollution because there were no organic materials (paint) in the test. It was found that the gaseous iodine fraction is mostly composed of inorganic iodine species after 60 h of irradiation. Before that time, organic and inorganic species represent each about 50% of

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Table 5 Main validation matrix for ASTEC/IODE. Experiments

Type

Main Phenomena involved

CAIMAN (Cantrel, 2006) ACE and PHEBUS RTF (Kupferschmidt et al., 1992) Radiolysis tests (Burns et al., 1990) (Ashmore et al., 2000) etc. EPICUR (Verloo et al., 1996; Dickinson et al., 2010) PARIS (Langrock and Funke, 2005; Bosland et al., 2008, 2011) SISYPHE (Cantrel and March, 2006) BIP (Glowa and Moore, 2011; Glowa et al., 2013) PhD academic studies (Nugraha, 1997; Cantrel, 1997; Marchand, 1997; Aubert, 2002; Mun, 2007; Zhang, 2012), etc. CARAIDAS (Layly and Masson, 2002) European projects of the 4th and 5th FwP (Dickinson et al., 2001, 2003), etc. Literature data (Vikis, 1985; Thomas et al., 1980), etc. Phébus.PF (Schwarz and Hache, 1999)

Semi-global Semi-global Analytical Analytical Analytical Analytical Analytical Analytical

Mass transfer phenomena Liquid and gaseous chemistries and mass transfer phenomena Liquid chemistry (oxidation of I− ) Gaseous chemistry (Org-I formation) Gaseous chemistry (I2 oxidation) Mass transfer phenomena (liquid-sump) Gaseous chemistry (Org-I formation) Liquid and gaseous chemistries, mass transfer

Analytical Analytical Analytical Integral

Mass transfer phenomena (spray) Liquid and gaseous chemistries Liquid and gaseous chemistries Liquid and gaseous chemistries and mass transfer phenomena

Fig. 14. Schematic diagram of the radioiodine test facility (RTF).

Fig. 15. Evolution of the iodide ions (I− ) percentage in the sump and pH (right axis) for P9T1 test.

the gaseous iodine fraction. In fact, as the pH was alkaline, very little volatile iodine was produced and transferred towards the gaseous phase (<10−11 mol L−1 ) which made the organic proportion higher at the beginning of the test (No organic has been considered in the modelling). Among the inorganic iodine, it is assumed that iodine oxides (IOx) and gaseous iodine (I2 ) were both trapped into the inorganic filter, located before the charcoal trap used to trap the organics. The modelled concentration of inorganic iodine is thus the sum of I2 and IOx. P9T1 test was simulated with ASTEC/IODE V2.0 and the parameters used are similar to those used for the THAI 9 test modelling (Weber et al., 2010). The iodide ions concentration in the sump is shown on Fig. 15 (left axis). The I− concentration is quite well reproduced for pH >8 and pH <6. In between, the simulation overestimates it. For the gaseous phase, the total inorganic gaseous iodine (I2 + IOx) is compared with the experimental data on Fig. 16 (left axis). When the pH decreases, the gaseous iodine concentration rises. The modelling fits quite well the gaseous concentration profile as a function of pH even if the code underestimates the experimental gaseous iodine fraction. At the very end of the test when the pH was raised from 5 to 10, the alkaline sump was no longer a source of I2 volatilisation, thus in agreement with experimental data, the gas concentration decreased in the calculation, due to trapping in charcoal filters set in the gaseous sampling loop. As shown in Fig. 17 curve B, molecular iodine is the main calculated gaseous iodine species. Iodine oxides, which result from

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L. Cantrel et al. / Nuclear Engineering and Design 272 (2014) 195–206 Table 6 Comparison of the mass balance at the end of the P9T1 test.

Sump Gaseous phase Dry stainless steel deposits Wet stainless steel deposits Lost by liquid leaks Total mass balance a

Fig. 16. Evolution of the gaseous total inorganic iodine (I2 + IOx) concentration and pH (right axis) for P9T1 test.

I2 oxidation, form small particles by nucleation as highlighted by recent experiments (Funke et al., 2012; Zhang, 2012). For IOx behaviour, a settling and wall transfer rates was fixed to 10−6 s−1 in the simulation. Gaseous I2 is effectively trapped by the sump once the pH is increased from 5 to 10 at the end of the test. Some recent experiments in the OECD/STEM programme evidenced the fact that the iodine oxides might not be stable under irradiation but currently they are considered as iodine sink. The iodine mass balance at the end of the test is compared between experiment and simulation in Table 6.

Fig. 17. Gaseous speciation, in percentage, of inorganic iodine for P9T1 test.

Experiment (%)

Computation (%)

54.3 <0.01 0.2/5.2a 0.02/2a ∼15 64.5/71.5

49.7 <0.001 0.2 33.8 Fixed at 15 100

Estimation based on loop sections, associated with large uncertainties.

From 30 to 35% of the iodine was not recovered in the experiment. There are significant uncertainties on the surface deposits measurements (dry and wet stainless steel surfaces) that could be explained by corrosion spots in the recirculation and sampling loops of the liquid phase that might have trapped significant amount of iodine (sediment or adsorbed iodine). In fact the submerged surfaces in those loops represent 40% of the total submerged stainless steel surfaces which is significant. The amount of iodine trapped there could not be quantified because of a difficult access to these loops. Moreover, the modelling shows that about a third of the total iodine inventory should be adsorbed on the submerged surfaces whereas only 2% maximum was measured in the vessel. The missing iodine could therefore be deposited on the recirculation and sampling loops. To sum up, it can be concluded that the IODE iodine radiochemistry in the sump is relevant to predict I2 formation as the discrepancies are reasonable for representative pH (acidic or basic pH). A better modelling could be reached if a radiolytic destruction of iodine oxides into gaseous iodine would be taken into account in the module as well as a refined kinetics of settling and transfer to the sump and walls. The on-going OECD/BIP2 and OECD/STEM programmes are dedicated to check iodine oxides stability under irradiation and thus will help to address this issue. 5. Conclusion The ASTEC FPs models are at the state of the art and allow performing source term evaluations. It is worth noticing that the coupling of ASTEC to the SUNSET statistical tool (Chevalier-Jabet et al., 2013) allows making easier the realisation of sensitivity analyses thanks to an evaluation of the influence of uncertainties on parameters or models on the source term calculations. Validation of these FPs behaviour models is supported by a large set of experiments, most of which have been carried out in the frame of international research programmes. The main planned improvements in the near future are as follows: - For ELSA, integral VERDON experiments realised in the frame of the International Source Term Programme, together with multiscale experimental and theoretical approaches, will bring new insights on FP releases for situations that have been little considered up to now such as air-ingress conditions (mixed and steam), pure air conditions, MOx fuel, and scenarios for which the fuel cooling is recovered before fuel melt; - For SOPHAEROS, the main developments are linked to: • The transport of iodine through the RCS by implementations of some kinetics aspects (Cantrel et al., 2013) and of the ruthenium oxides behaviour in case of air-ingress accidents. For this last issue, the START (Study of the TrAnsport of RuThenium in the primary circuit) experimental programme is ongoing, as part of the OECD/STEM project and it will complete the already available data (Vér et al., 2010, 2012; Kärkelä et al., 2011) on this issue.

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• A better assessment of delayed releases linked to possible remobilisation of some FPs depositions along the RCS. This remobilisation can be due to chemical reactivity onto stainless steel pipes and inconel inner steam generator surfaces. The importance of revaporisation effects has been evidenced in integral experiments (Phébus.PF, VERDON,. . .) and a mixed theoretical and experimental analytical approach is on-going at IRSN to develop predictive models of this phenomenon that will certainly play an important role on the mid to long-term source term. • The extension of SOPHAEROS capabilities to deal with SGTR DBA accidents. New developments are ongoing to implement specific models to calculate the distribution of droplets which contain dissolved FPs, at the primary-secondary break as well as chemistry models which are suitable for predicting the gaseous fraction release during the flashing phase. • The extension of SOPHAEROS capabilities to simulate some accidents which could happen in ITER fusion facility (Virot et al., 2013). For this, some R&D is under way to better assess the Tritium and Beryllium chemistry. • In the frame of next generation of NPP, more specifically for SFR, sodium chemistry is under review (Mathé et al., 2013) to better model the chemical form of sodium release in case of an accident. - For IODE, concerning iodine chemistry, the still open issues are: first, relative to radiolytic stability of iodine oxide and more generally of metallic iodine aerosols which are partially deposited onto inner walls during a severe accident; secondly, to improve the organic iodide production models to take into account all possible sources of formation (from organics dissolved in sump, for organics in gas and between interactions in the iodine adsorbed onto paint and the organic paint network). All these points are key safety issues due to high potential radiological consequence in case of iodine and ruthenium releases outside the containment. A part of these tasks is conducted in the frame of the SARNET European network, especially for research topics related to iodine chemistry (Haste et al., 2012). Some of these new models will be implemented in the second major ASTEC V2 version (to be identified as V2.1) expected to be delivered in 2014. In addition, in a near future ASTEC will be coupled to atmospheric dispersion codes in order to perform PSA3 studies. Currently, ASTEC is the most advanced SA simulation software in terms of FPs behaviour that results from large efforts made to develop and implement models of all important phenomena from French and international R&D programmes of the field. References Anderson, G., Auvinen, A., Bottomley, P.D., Bryan, C.J., Freemantle, N.E., Hieraut, J.P., Jokiniemi, J.K., Kingsbury, A.F., Tuson, A.T., 2000. Revaporisation tests on samples of PHEBUS fission products. Summary final report. 4th EC framework. Report ST: RVP(00)-P30. Andrews, G., Lewis, B.J., Cox, D.S., 1999. Artificial neural network models for volatile fission product release during severe accident conditions. Journal of Nuclear Materials 270, 74–99. Anon., 1988. LWR Aerosol Containment Experiments (LACE) project. Summary report. Electric Power Research Institute (Report) EPRI NP. Ashmore, C.B., Brown, D., Dickinson, S., Sims, H.E., 2000. Measurements of the radiolytic oxidation of aqueous CsI using a sparging apparatus. Nuclear Technology 129 (3), 387–397. Aubert, F., (Ph.D.) 2002. Destruction par le rayonnement gamma de l’iodure de méthyle en faible concentration dans l’air humide. Université Paul Cézanne, France. Ball, M.H.E., Mitchell, J.P., 1992. The deposition of micron-sized particles in bends of large diameter pipes. Journal of Aerosol Science 23, 23–26. Bandini, G., Buck, M., Hering, W., Godin-Jacqmin, L., Ratel, G., Matejovic, P., Barnak, M., Paitz, G., Stefanova, A., Trégourès, N., Guillard, G., Koundy, V., 2010. Recent advances in ASTEC validation on circuit thermal-hydraulic and core degradation. Progress in Nuclear Energy 52, 148–157.

205

Barrand, R.D., Dickson, R.S., Liu, R.S., Semeniuk, D.D., 1999. Release of fission products from CANDU fuel in air, steam and argon atmospheres at 1500–1900 ◦ C: the HCE3 experiment. In: 6th International CNS CANDU Fuel Conference, CNS, Niagara Falls, pp. 1–10. Beard, A.M., Bennett, P.J., Bowsher, B.R., Brunning, J., 1992. The falcon programme: characterisation of multicomponent aerosols in severe nuclear reactor accidents. Journal of Aerosol Science 23, 831–834. Bosland, L., Cantrel, L., Girault, N., Clément, B., 2010. Modelling of iodine radiochemistry in the ASTEC severe accident code: description and application to FPT-2 PHEBUS test. Nuclear Technology 171, 88–107. Bosland, L., Funke, F., Girault, N., Langrock, G., 2011. PARIS project: Radiolytic oxidation of molecular iodine in containment during a nuclear reactor severe accident. Part 2. Formation and destruction of iodine oxides compounds under irradiation – experimental results modelling. Nuclear Engineering and Design 241 (9), 4026–4044. Bosland, L., Funke, F., Girault, N., Langrock, G., 2008. PARIS Project: radiolytic oxidation of molecular iodine in containment during a nuclear reactor severe accident. Part 1. Formation and destruction of air radiolysis products. Experimental results and modelling. Nuclear Engineering and Design 238 (12), 3542–3550. Brillant, G., Marchetto, C., Plumecocq, W., 2013a. Estimation of the fission product release from fuel using the accident code ASTEC/ELSA. I. Physical modelling. Annals of Nuclear Energy 61, 88–95. Brillant, G., Marchetto, C., Plumecocq, W., 2013b. Estimation of the fission product release from fuel using the accident code ASTEC/ELSA. II. Validation on small and large scale experiments. Annals of Nuclear Energy 61, 96–101. Brillant, G., 2011. Models for the release from fuel of Ce, La, Sr, and Eu in accident conditions. Progress in Nuclear Energy 53, 125–131. Brillant, G., 2010. Interpretation and modelling of fission product Ba and Mo releases from fuel. Journal of Nuclear Materials 397, 40–47. Brillant, G., Marchetto, C., Plumecocq, W., 2010. Ruthenium release from fuel in accident conditions. Radiochimica Acta 98, 267–275. Bujan, A., Ammirabile, L., Bieliauskas, A., Toth, B., 2010. ASTEC V1.3 code SOPHAEROS module validation using the STORM experiments. Progress in Nuclear Energy 52, 777–788. Burns, W.G., Kent, M.C., Marsh, W.R., Sims, H.E., 1990. The Radiolysis of Aqueous Solutions of Caesium Iodide and Caesium Iodate. Report AERE-R-13520. Atomic Energy Authority, United Kingdom. Cantrel, L., Louis, F., Cousin, F., 2013. Advances in mechanistic understanding of iodine behaviour in PHEBUS-FP tests with the help of ab initio calculations. Annals of Nuclear Energy 61, 170–178. Cantrel, L., 2006. Radiochemistry of iodine: outcomes of the CAIMAN program. Nuclear Technology 156, 11–28. Cantrel, L., March, P., 2006. Mass transfer modeling with and without evaporation for iodine chemistry in the case of a severe accident. Nuclear Technology 154, 170–185. Cantrel, L., (Ph.D.) 1997. Caractérisation de l’acide hypoïodeux. Réactions d’oxydation de l’iode. Université de droit, d’économie et de sciences d’Aix Marseille III. Chevalier-Jabet, K., Cousin, F., Cantrel, L., Séropian, C., 2013. Source term assessment with ASTEC and associated uncertainty analysis using SUNSET tool. Nuclear Engineering and Design, http://dx.doi.org/10.1016/j.nucengdes.2013.06.042. Clément, B., Zeyen, R., 2005. The Phébus FP and international source term programmes. In: Proc. Int. Conf. on Nuclear Energy for New Europe, Bled, Slovenia, September, pp. 5–8. Cousin, F., Dieschbourg, K., Jacq, F., 2008. New capabilities of simulating fission product transport in circuits with ASTEC/SOPHAEROS v1.3. Nuclear Engineering and Design 238, 2430–2438. Cox, D.S., Hunt, C.E.L., Liu, Z., Iglesias, F.C., Keller, N.A., Barrand, R.D., O’Connor, R.F., 1991a. A model for the release of low volatility fission products in oxidizing conditions. In: 12th Annual Conference, AECL-10440, CNS, Saskatoon, pp. 280–289. Cox, D.S., Hunt, C.E.L., Liu, Z., Keller, N.A., Barrand, R.D., O’Connor, R.F., Iglesias, F.C., 1991b. Fission product releases from UO2 in air and inert conditions at 1700–2350 K: analysis of the MCE-1 experiment. In: Safety of Thermal Reactors, AECL-10438, Int. Topical Meeting, ANS, Portland, pp. 1–20. Dickinson, S., Sims, H.E., Guentay, S., Bruchertseifer, H., Liljenzin, J.O., Glänneskog, H., Kissane, M.P., Cantrel, L., Krausmann, E., Rydl, A., 2003. Iodine chemistry and mitigation mechanism (ICHEMM). In: FISA-2003 Symposium: EU Research in Reactor Safety, Luxembourg, November, pp. 10–13. Dickinson, S., Andreo, F., Karkela, T., Ball, J., Bosland, L., Cantrel, L., Funke, F., Girault, N., Holm, J., Guilbert, S., Herranz, L.E., Housiadas, C., Ducros, G., Mun, C., Sabroux, J.C., Weber, G., 2010. Recent advances on containment iodine chemistry. Progress in Nuclear Energy 52, 128–135. Dickinson, S., Sims, H.E., Belval-Haltier, E., Jacquemain, D., Poletiko, C., Funke, F., Hellman, S., Karjunen, T., Zilliacus, R., 2001. Organic iodine chemistry. Nuclear Engineering and Design 209, 193–200. Dickson, L.W., Dickson, R.S., Liu, Z., Barrand, R.D., Semeniuk, D.D., 2001. Fissionproduct releases from CANDU fuel heated to 1650 ◦ C: HCE4 experiment. In: 7th International Conference on CANDU Fuel, Vol. 2, Kingston, Ontario, Canada, 3B/21–30. Domagala, P.E., Rest, J., Zawadzki, S.A., 1991. Assessment of improved fissionproduct transport models in VICTORIA against ornl HI and VI tests. AIChE Symposium Series 87, 182–189. Drosik, I., Kissane, M., Dumaz, P., 1995. Fission Analysis of aerodevap experiments with the sophaeros computer code. Journal of Aerosol Science 26, S709–S710.

206

L. Cantrel et al. / Nuclear Engineering and Design 272 (2014) 195–206

Dubourg, R., Faure-Geos, H., Nicaise, G., Barrachin, M., 2005. Fission product release in the first two PHEBUS tests FPT0 and FPT1. Nuclear Engineering and Design 235, 2183–2208. Ducros, G., Bernard, S., Ferroud-Plattet, M.P., Ichim, O., 2009. Use of gamma spectrometry for measuring fission product releases during a simulated PWR severe accident: application to the VERDON experimental program. In: 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications, ANIMMA 2009, Marseille, 7 June, p. 2009. Ducros, G., Malgouyres, P.P., Kissane, M., Boulaud, D., Durin, M., 2001. Fission product release under severe accidental conditions: General presentation of the program and synthesis of VERCORS 1-6 results. Nuclear Engineering and Design 208, 191–203. Funke, F., Langrock, G., Kanzleiter, T., Poss, G., Fischer, K., Künhnel, A., Weber, G., Allelein, H.J., 2012. Iodine oxides in large-scale THAI tests. Nuclear Engineering and Design 245, 206–222. Gelbard, F., 1982. MAEROS User Manual. Report NUREG/CR-CR1391. Giordano, P., Auvinen, A., Brillant, G., Colombani, J., Davidovich, N., Dickson, R., Haste, T., Kärkelä, T., Lamy, J.S., Mun, C., Ohai, D., Pontillon, Y., Steinbrück, M., Ver, N., 2010. Recent advances in understanding ruthenium behaviour under airingress conditions during a PWR severe accident. Progress in Nuclear Energy 52, 109–119. Glowa, G., Moore, C.J., Ball, J.M., 2013. The main outcomes of the OECD behaviour of iodine (BIP) project. Annals of Nuclear Energy 61, 179–189. Glowa, G., Moore, C.J., 2011. Behaviour of Iodine Project. Final Summary Report. NEA/CSNI/R(2011)11. Glowa, G., Moore, C.J., 2009. Radioiodine Test Facility P9T1 Test Report. Report AECL 153-126530-440-008 Revision D1 – BIP project. Gouello, M., Lacoue-Negre, M., Mutuelle, H., Cousin, F., Sobanska, S., Blanquet, E., 2011. Chemistry of iodine and aerosol composition in the primary circuit of a nuclear reactor , ICAPP 2011, 2–5 May 2011, Nice, France. Grégoire, A.C., Mutelle, H., 2012. Experimental study of the [B, Cs, I, O, H] and [Mo, Cs, I, O, H] Systems in the Primary Circuit of a PWR in conditions representative of a severe accident. In: 21st International Conference in Nuclear Energy for New Europe (NENE), Ljubljana, Slovenia, September, pp. 4–7. Grégoire, A.C., Haste, T., 2012. FP Release During the PHEBUS FP tests. Final Seminar of the Phebus FP Programme. Aix-en-Provence (France), June., pp. 13–15. Haste, T., Auvinen, A., Colombani, J., Funke, F., Glowa, G., Güntay, S., Holm, J., Kärkela, T., Langrock, G., Poss, G., Simondi-Teisseire, B., Tietze, S., Weber, G., 2012. Containment iodine experiments in the SARNET2 project. In: 5th European Review Meeting on Severe Accident Research (ERMSAR 2012), Cologne, Germany, March, pp. 21–23. Jacquemain, D., Bourdon, S., de Bremaecker, A., Barrachin, M., 2000. FPT1 Final Report IP/00/479. Kärkelä, T., Auvinen, A., Kalilainen, J., Lyyränen, J., Kajolinna, T., Pyykönen, J., Raunio, T., Kåll, L., Zilliacus, R., Tapper, U., Kekki, T., Järvinen, R., Jokiniemi, J., 2011. Primary Circuit Chemistry of Fission Products (CHEMPC): Summary Report. VTT Tiedotteita – Valtion Teknillinen Tutkimuskeskus 2571., pp. 301–311. Kljenak, I., Dapper, M., Dienstbier, J., Herranz, L.E., Koch, M.K., Fontanet, J., 2010. Thermal–hydraulic and AEROSOL containment phenomena modelling in ASTEC severe accident computer code. Nuclear Engineering and Design 240 (3), 656–667. Kupferschmidt, W.C.H., Ball, J., Buttazoni, J.B., Evans, G., Jobe, D.J., Melnyk, A.J., Palson, A.S., Portman, R., Sanipelli, G.G., 1992. Final Report on the ACE/RTF Experiments, Report ACE-TR-B3. Whiteshell Nuclear Research Establishment. Langrock, G., Funke, F., 2005. Synthesis of PARIS results (Program on Air Radiolysis, Iodine and Surfaces). Report NGTR/2005/en/0308. AREVA-Framatome ANP. Layly, V.D., Masson, V., 2002. Programme ASPERSION Bilan de la campagne d’essais IODE dans CARAIDAS. Report IRSN/DPEA/SERAC/LPMAC/02-03. Le Marois, G., 1987. Report CEA DMG n◦ 64/875. 1988. Report CEA DMG n◦ 58/88. 1989. Report CEA DMG n◦ 34/89.

Le Marois, G., Megnin, M., 1994. Assessment of fission product deposits in the reactor coolant system: The DEVAP program. Nuclear Safety 35, 213–222. Marchand, C., (Ph.D.) 1997. Production d’iodures organiques à partir des surfaces peintes de l’enceinte de confinement d’un réacteur à eau pressurisée en situation accidentelle. Université de Paris XI, Orsay, France. Mathé, E., Kissane, M., Petitpez, D., 2013. Modélisation de la transformation physicochimique des aérosols de sodium. In: Congrès Franc¸ais sur les Aérosols, Paris, France, 23–24 January. Mun, C., Cantrel, L., Madic, C., 2008. Radiolytic oxidation of ruthenium oxide deposits. Nuclear Technology 164 (2), 245–254. Mun, C., (Ph.D.) 2007. Study of the Radiochemistry of Ruthenium Fission Product Behaviour Inside the Containment in Case of Severe Accident. Paris-XI University, France. Mun, C., Cantrel, L., Madic, C., 2007. Study of RuO4 decomposition in dry and moist air. Radiochemica Acta 95, 643–656. Nugraha, T., (Thesis) 1997. Iodine Retention on Stainless Steel on Sampling Line. University of Toronto, Canada. Rabu, A.C., Pagano, C., Boucenna, A., Addes, E., Dubourg, R., Tourasse, M., d’Aillon, L.G., Boulaud, D., 1999. Silver–indium–cadmium–tin aerosol releases and control rod behaviour in PWR accidental conditions. Journal of Aerosol Science 30, S109–S110. Saldo, V., (Ph.D.) 1996. Etude du dépôt d’aérosols dans des conduites en écoulement fortement turbulent (Study of Aerosol Deposition in Highly Turbulent Pipe Flow). Université de Marseille 1, France. Schwarz, M., Hache, G., Von der Hardt, P., 1999. PHEBUS FP: a severe accident research programme for current and advanced light water reactors. Nuclear Engineering and Design 187, 47–69. Thomas, T.R., Pence, D.T., Hasty, R.A., 1980. The disproportionation of hypoiodous acid. Journal of Inorganic and Nuclear Chemistry 42 (2), 183–186. Vér, N., Matus, L., Pintér, A., Osán, J., Hózer, Z., 2012. Effects of different surfaces on the transport and deposition of ruthenium oxides in high temperature air. Journal of Nuclear Materials 420, 297–306. Vér, N., Matus, L., Kunstár, M., Osán, J., Hózer, Z., Pintér, A., 2010. Influence of fission products on ruthenium oxidation and transport in air ingress nuclear accidents. Journal of Nuclear Materials 396, 208–217. Verloo, E., Belval, S., Saldo, V., Albiol, T., Sabathier, F., 1996. Study of aerosol deposition in large pipes: transat programme. Journal of Aerosol Science 27, S453–S454. Veshchunov, M.S., Ozrin, V.D., Shestak, V.E., Tarasov, V.I., Dubourg, R., Nicaise, G., 2006. Development of the mechanistic code MFPR for modelling fission-product release from irradiated UO2 fuel. Nuclear Engineering and Design 236, 179–200. Vikis, A.C., Macfarlane, R., 1985. Reaction of iodine with ozone in the gas phase. Journal of Physical Chemistry 89 (5), 812–815. Virot, F., Barrachin, M., Souvi, S., Cantrel, L., Vola, D., 2013. Theoretical prediction of thermodynamic properties of tritiated beryllium molecules and application to ITER source term. In: International Symposium on Fusion Nuclear Technology (ISFNT), Barcelona, 16–20 September. Weber, G., Bosland, L., Funke, F., Glowa, G., Kanzleiter, T., 2010. ASTEC, COCOSYS, and LIRIC Interpretation of the Iodine Behavior in the Large-Scale THAI Test Iod9. Journal of Engineering for Gas Turbines and Power 132 (11), 112902 (article number 112902). Wright, A.L., Arwood, P.C., Wilson, J.H., 1987. Summary of Posttest Aerosol Code Comparisons for LWR Aerosol Containment Experiment (LACE). ORNL/M-365 report, EPRI. Zhang, S., (Ph.D.) 2012. Etudes cinétiques de l’oxydation radicalaire en phase gazeuse d’iodures organiques et de la formation de particules d’oxydes d’iode sous conditions simulées de l’enceinte d’un réacteur nucléaire en situation d’accident grave. Université Aix-Marseille, France. Zoulalian, A., Albiol, T., 1998. Evaluation of aerosol deposition by thermo and diffusiophoresis during flow in a circular duct – applications to the experimental program ‘Tuba diffusiophoresis’. Canadian Journal of Chemical Engineering 78, 799–805.