F Dacquait

J Francescatto

F Broutin

J B Genin

G Bénier

M Girard

D You

G Ranchoux

J Bonnefon

M Bachet

SIMULATIONS OF CORROSION PRODUCT TRANSFER WITH THE OSCAR V1.2 CODE

Activated Corrosion Products (ACPs) generate a radiation field in PWRs, which is the major contributor to the dose absorbed by nuclear power plant staff working during shutdown operations and maintenance. Therefore, a thorough understanding of the mechanisms that control the corrosion product transfer is of the highest importance. Since the 1970's, the R&D strategy in France has been based on experiments in test loops representative of PWR conditions, on in-situ gamma spectrometry measurements of the PWR primary system contamination and on simulation code development. The simulation of corrosion product transfers in PWR primary circuits is a major challenge since it involves many physical and chemical phenomena including: corrosion, dissolution, precipitation, erosion, deposition, convection, activation… In addition to the intrinsic difficulty of multi-physics modelling, the primary systems present severe operating conditions (300 °C, 150 bar, neutron flux, fluid velocity up to 15 m.s -1 and very low corrosion product concentrations). The purpose of the OSCAR code, developed by the CEA in cooperation with EDF and AREVA NP, is to predict the PWR primary system contamination by corrosion and fission products. The OSCAR code is considered to be not only a tool for numerical simulations and predictions (operational practices improvements and new-built PWRs design) but also one that might combine and organise all new knowledge useful to progress on contamination. The OSCAR code for Products of Corrosion, OSCAR PC, allows researchers to analyse the corrosion product behaviour and to calculate the ACP volume and surface activities of the primary and auxiliary systems.

In the new version, OSCAR PC V1.2, the corrosion product transfer in the particulate form is enhanced and a new feature is the possibility to simulate cold shutdowns. In order to validate this version, the contamination transfer has been simulated in 5 French PWRs with different operating and design characteristics. After a description of the models of the main transfer mechanisms, the paper presents the calculated ACP surface and volume activities, the calculated concentrations of metallic elements and their comparisons with on-site measurements for one of the 5 validation cases. The simulations of a steam generator replacement and a cold shutdown are also presented. There is a good agreement between the OSCAR PC V1.2 results and the measured values during power operation and cold shutdown as well. Furthermore, the variations with operating cycle of the surface activities are correctly reproduced. Compared to the previous versions, these improvements are mainly due to the improvement of the thermodynamic database of the OSCAR chemistry module, PHREEQCEA, and to the enhancement of the corrosion product transfer in the particulate form.

INTRODUCTION

Activated Corrosion Products (ACP) generate a radiation field in PWRs which is the major contributor to the dose absorbed by nuclear power plant staff working during shutdown operations and maintenance. Therefore, a thorough understanding of the mechanisms that control the corrosion product transfer is of the highest importance. Since the 1970's, the R&D strategy in France has been based on experiments in test loops representative of PWR conditions, on in-situ gamma spectrometry measurements of the PWR primary contamination and on simulation code development. The simulation of corrosion product transfers in PWR primary circuits is a major challenge since it involves many physical and chemical phenomena including: corrosion, dissolution, precipitation, erosion, deposition, convection, activation... In addition to the intrinsic difficulty of multi-physics modelling, the primary systems present severe operating conditions (300 °C, 150 bar, neutron flux, water velocity up to 15 m.s -1 and very low corrosion product concentrations). The purpose of the OSCAR 1 code, developed by the CEA in cooperation with EDF and AREVA NP, is to predict the contamination of the PWR primary system in power operating and cold shutdown conditions. The OSCAR code is the merging of two contamination codes: PACTOLE for corrosion products and PROFIP for fission products and actinides. The OSCAR code is a new version of these contamination transfer codes developed by the CEA since the 1970's [START_REF] Beslu | A computer code PACTOLE to predict activation and transport of corrosion product in PWR[END_REF], [START_REF] Beslu | PACTOLE-PROFIP : two codes allowing prediction of the contamination of PWR primary circuits[END_REF], [START_REF] Tarabelli | Status and future plans of the PACTOLE code predicting the activation and transport of corrosion products in PWRs[END_REF], [START_REF] Marchetto | PACTOLE V3 : a new code version to predict corrosion product contamination[END_REF], [START_REF] Nguyen | First numerical simulations of contamination of the PWR primary circuit by activated corrosion products with the PACTOLE V3.0 code[END_REF], [START_REF] Dacquait | Simulations of corrosion product transfer with the PACTOLE V3.2 code[END_REF], [START_REF] Genin | The OSCAR code package : a unique tool for simulating PWR contamination[END_REF]. In order to validate the new version of the simulation code OSCAR for Products of Corrosion, OSCAR PC V1.2, the contamination transfer has been simulated in 5 French PWRs with different operating and design characteristics. After a description of the models of the main transfer mechanisms, for one of the 5 PWR cases this paper presents the calculated ACP surface and volume activities, the calculated concentrations of metallic elements and their comparisons with in-situ measurements. In the last part, simulations of a cold shutdown and a steam generator replacement are also presented.

PRESENTATION OF THE SIMULATION CODE OSCAR PC V1.2.1 CORROSION PRODUCT TRANSFER MODELLING

The corrosion product transfer modelling of OSCAR PC V1.2 is almost identical to the previous versions [START_REF] Genin | The OSCAR code package : a unique tool for simulating PWR contamination[END_REF], briefly:

The PWR systems (RCS, CVCS, RHRS)2 are discretized into several control volumes or regions (typically around 100 regions) defined according to the geometric, thermal-hydraulic, neutronic, material and operating characteristics. Seven media can be taken into account in each control volume: the base metal, the inner oxide layer, the outer oxide layer, the deposit, the particles and ions and the purification system (filter and resins) for particles and ions. The metallic elements taken into account are those composing the main alloys found in any primary system that generate the main ACPs: Ni, Co, Fe, Cr, and Mn. Their radioisotopes, which generate the dose rates around the primary systems, are: Cr. The mass balances are calculated for each isotope (stable and radioactive) of these metallic elements in each medium of each region using the following equation: ] and J m the mass flux between 2 media (except for nuclear reactions that represent a mass transfer inside the same medium) [kg.s ]. The transfer mechanisms taken into account are: corrosionrelease, dissolution, precipitation, erosion, deposition, diffusion, convection, activation and radioactive decay.

MAIN TRANSFER MECHANISMS

In addition to the corrosion mechanism which is the source term, the main mechanisms involved in the corrosion product transfer are dissolution/precipitation and erosion/deposition.

Dissolution/Precipitation

The dissolution of a deposit occurs when the concentration of a soluble species in the coolant is less than its equilibrium concentration. The dissolution flux of the element elt,

elt dissol J [kg.s -1
], may be written: ]. The equilibrium concentration of each chemical element and the oxide speciation of the deposit are calculated by the OSCAR chemistry module, PHREEQCEA (a version of the PHREEQC code [START_REF] Parkhurst | User's guide to PHREEQC (version 2) -A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations[END_REF] extended to the PWR temperature range) in combination with a thermodynamic database developed by the CEA [START_REF] Plancque | Role of chemistry in the phenomena occurring in nuclear power plants circuits[END_REF]. PHREEQCEA determines the composition of the ideal solid solution (mixed oxides and any pure solid phases possibly in excess) and the equilibrium concentration of each element in relation to the chemical conditions (pH, H 2 , O 2 ), the coolant temperature and the masses of the metallic element of the deposit in each control volume. As the dissolution velocities are not well known in PWR conditions, they are calibrated in OSCAR. However, in order to have data of dissolution velocities, an experimental program is underway in the CEA to determine the oxide dissolution kinetics [START_REF] Plancque | Experimental study and modeling of the corrosion product dissolution. Applications to PWR conditions (nominal operating and cold shutdowns conditions)[END_REF]. Soluble species precipitate when their concentration in the coolant reaches their equilibrium concentration. The expression of the precipitation flux is similar to that of the dissolution flux considering that the limiting phenomenon is the mass transfer in the fluid and not the precipitation surface reaction rate coefficient. The expression of the precipitation flux,

) ( 1 1 elt elt equil dissol elt dissol C C V h S J - ⋅ + = with S
elt precip J [kg.s -1
], is thus: ].

) ( elt equil elt elt precip C C S h J - ⋅ ⋅ =

Erosion/Deposition

The erosion term of a deposit results from the coolant friction forces. The model assumes that a deposit can be eroded above the laminar sub-layer. In a volume control, the erosion flux, J eros [kg.s ], S dep the surface of the deposit [m²] and T eros the erosion characteristic time [s] which is a calibration parameter. The particle deposition rate takes into account 1) the turbulent diffusion and the effects of inertia [START_REF] Beal | Deposition of particles in turbulent flow on channel or pipe walls[END_REF], 2) the sedimentation for horizontal ducts [START_REF] Michell | Fluid and particle mechanics[END_REF] and 3) the thermophoresis for temperature gradients between the coolant and the wall [START_REF] Ponting | Intrinsic filtration and retarded deposition for the control of colloidal corrosion product deposition on PWR fuel[END_REF]. In a volume control, the deposition flux, J depos [kg.s

Calibration

For OSCAR V1.2, we have reassessed the relative influences of the ionic and particulate forms in the corrosion product transfer. Compared to the previous versions, the corrosion product transfer in the particulate form is enhanced. To achieve this goal, the thickness of the laminar sub-layer e lim has been reduced by a factor of 5 and the deposition velocity of particles has been reduced by a factor of 10 [START_REF] Girard | Experimental study of particle deposition kinetics in the primary circuit of the CIRENE loop and comparison with OSCAR V1.2 code simulations[END_REF]. With 58 Co and 60 Co contributing by over 90% on the average to the dose rates around primary systems, the parameters V dissol , T eros , e lim, and V depos have been calibrated by focusing on these two radioisotopes with respect to typical surface activities, volume activities and ion concentrations measured in PWR primary systems. The results obtained with this new configuration are presented in the next paragraph.

SIMULATIONS USING OSCAR PC V1.2

In order to validate OSCAR PC V1.2, the corrosion product behaviour has been simulated in 5 French PWRs (DAMPIERRE-1, CRUAS-1, CHINON-B1, CATTENOM-2 and GOLFECH-2) which have different operating and design characteristics (900/1300 MWe PWRs, Inconel 600MA/600TT/690TT SGs, Inconel 718/Zry grids, pH of 7.0/7.2, different fuel managements …). The results have been compared to on-site measurements: surface activities (EMECC campaigns [START_REF] Eimecke | Ensemble de Mesure et d'Etude de la Contamination des Circuits (EMECC)[END_REF] [16]), volume activities (total, ionic and particulate forms) and chemical element concentrations. We present the simulation of one of the 5 validation cases below (CATTENOM-2). Like the previous versions, OSCAR takes into account the refuelling and a steam generator replacement if necessary. Cold shutdowns can be simulated using OSCAR PC V1.2, which is a major improvement of this new version, or only the effects of cold shutdowns can be taken into account (like in the previous versions). The simulations of DAMPIERRE-1 which underwent a Steam Generator Replacement (SGR) and of a cold shutdown of GOLFECH-2 are also presented in this part.

MAIN INPUT DATA

To run the OSCAR PC code, it is necessary to provide a set of input data:

The geometric parameters of a control volume are the hydraulic diameter and the wet surface.

The thermal-hydraulic data, which includes the velocity, the flowrate, the bulk and wall temperatures of the coolant.

The materials are defined by their density, their composition and their roughness. Any possible surface treatment is taken into account via the experimental corrosion and release rates.

As the activation of the corrosion products is directly proportional to the neutron flux, the power fraction is specified in each part of the core. The neutron reaction rates, as a function of PWR type, fuel burnup, 235 U enrichment and Pu content, are extracted from a nuclear database interfaced with OSCAR. In terms of operating data, a cycle is defined by its duration, its power history and its concentration levels in boron, lithium, hydrogen and oxygen. The refuelling of fuel assemblies at each end of cycle.

SIMULATION OF CATTENOM-2

Unit 2 of the nuclear power plant of CATTENOM is a 1300 MWe PWR commissioned in 1988. It is equipped with Inconel 600TT SG tubes. From the 3 rd cycle, the fuel assembly grids made of 718 alloy have been replaced by Zircaloy grids. For every cycle, one-third of the fuel was removed and replaced. The RCS and CVCS are described by 83 regions including 48 for the core (see Figure 1). The first 11 operating cycles have been simulated using OSCAR PC V1.2. CATTENOM-2 operated according to coordinated boron-lithium chemistry at pH 300°C of 7.0 for the first 7 cycles and then at pH 300°C of 7.2 with a maximum lithium concentration of 3.5 ppm (modified chemistry). The operating parameters are given in Figure 2 and the pH 300°C calculated using OSCAR/PHREEQCEA in Figure 3. Mn surface activities calculated using OSCAR V.1.2 with the surface activities measured at the beginning of some unit outages (cycles 3 to 5 and 7 to 11) using the EMECC system for the hot legs and the cold side of steam generator tubes. The simulation reproduced the levels and the trends of the surface activities of the primary system correctly: The average differences over the cycles between the calculated and measured activities are less than a factor of 2. Cr deposited inside the primary system cannot be measured due to its low gamma energy of 320 keV and the great thicknesses of the primary coolant pipes and steam generator shell. However, EMECC measurements of some auxiliary systems (SG by-pass or CVCS letdown pipe) allow us to estimate the 51 Cr surface activities of the primary system of the order of a few tenths of GBq/m² to a few GBq/m² [START_REF] Dacquait | Auxiliary System Contamination in French PWRs[END_REF]. The calculated range between 0.2 and 0.5 GBq/m² is of the same order of magnitude. In Figure 6, we have plotted the calculated and measured 58 Co and 60 Co surface activities on the SG cold and hot sides. The calculated surface activities on the cold side and on the hot side of the SG tubes of CATTENOM-2 are in good agreement with the EMECC measurements. The differences of measured contamination between the hot and cold sides of the SG tubes are low (less than 20%) or even zero. The measured 60 Co surface activity is higher on the cold side than on the hot side from cycle 7 (about 3,500 days) whereas the levels were similar at cycle 3 (about 1,700 days). In agreement with the measurements, the results obtained with OSCAR V1.2 show differences less than 15% between the two sides and the same trends: no difference for 60 Co contamination at cycle 3 and a higher contamination on cold side at cycle 7 and later. However in some cases after SGR, the temperature impact on the contamination levels of the hot and cold sides is very marked [START_REF] Dacquait | The impact of steam generator replacement on PWR primary system contamination[END_REF], reflecting a strong chemistry effect which is not reproduced by OSCAR PC V1.2. Fe is probably due to an underestimation of soluble and particulate activities (see Figure 9).

SIMULATION OF A SGR

DAMPIERRE-1, a 900 MWe PWR commissioned in 1980, underwent a Steam Generator Replacement (SGR) at the outage of cycle 8. The Inconel 600MA SGs have been replaced by Inconel 690TT SGs. The average Co content of the SG tubes was 270 ppm before SGR and 130 ppm after SGR. From the 6 th cycle, the fuel assembly grids made of 718 alloy were replaced by Zircaloy grids.

The first 15 operating cycles with an aimed pH 300°C of 7.0 have been simulated. The operating parameters are given in Figure 11 and the pH 300°C calculated using OSCAR/PHREEQCEA in Figure 12. Co coming from the Ni° activation to the dissolution of Ni°, which is done by a ratio. We have simulated 5 operating cycles including the cold shutdown of the 2 nd outage of GOLFECH-2, a 1300 MWe PWR equipped with Inconel 690TT SGs. GOLFECH-2 operated according to coordinated boron-lithium chemistry at pH 300°C of 7.0 until cycle 3 and then at pH 300°C of 7.2 (see Figure 15 and Figure 16). From cycle 2, the fuel assembly grids made of 718 alloy were replaced by Zircaloy grids. The average differences over the 5 cycles between the calculated and measured surface activities on the primary system are less than a factor of 1. There is a relative good agreement between the OSCAR PC V1.2 results and the measured values during power operation and cold shutdown as well. Furthermore, the variations with operating cycle of the surface activities are correctly reproduced. The simulations of a French 1450 MWe PWR and of an US 1100 MWe PWR have also shown a good consistency with the measurements [START_REF] Riot | Modeling of corrosion products contamination in PWR with the calculation code OSCAR V1.2[END_REF].

Compared to the previous versions, these improvements are mainly due to the improvement of the thermodynamic database of PHREEQCEA coupled to OSCAR and to the enhancement of the corrosion product transfer in the particulate form. Nevertheless, further improvements are scheduled in the next version that will be released in 2013, OSCAR PC V1.3. Its objectives in particular will involve: finding a better balance between the corrosion product transfers in the ionic and particulate forms in order to reproduce some phenomena, focusing not only on 58 Co and 60 Co but also on the other radioisotopes, improving the cold shutdown simulation, reassessing the erosion and release mechanisms, modelling the crud growth under nucleate boiling conditions [START_REF] Ferrer | Modelling of crud growth phenomena on PWR fuel rods under nucleate boiling conditions[END_REF].

  being the mass of the isotope (i) in a given medium [kg], t the time [s],

1 ]

 1 being the wet surface proportional to the mass of the element elt of the deposit [m²], h the mass transfer coefficient of ions in the fluid [m.s -, V dissol the dissolution velocity (dissolution surface reaction rate coefficient) of the element elt [kg.m -3 ] and C elt the bulk concentration of the element elt [kg.m -3

1 ]

 1 with h being the mass transfer coefficient of ions in the fluid [m.s -, S the wet surface [m²], C elt the bulk concentration of the element elt [kg.m of the element elt [kg.m -3

  being the mass of the deposit [kg], e lim the thickness of the laminar sub-layer, ρ dep the density of the deposit [kg.m -3

4 with 1 ]

 41 V depos being the deposition velocity of particles [m.s -, D h the hydraulic diameter [m] and m part the mass of particles in the fluid [kg].

Figure 1 :

 1 Figure 1: CATTENOM-2 -Control volumes (HL : Hot Leg / COL : CrossOver Leg / CL : Cold Leg)

Figure 2 : 4

 24 Figure 2: CATTENOM-2 -Operating parameters Figure 3: CATTENOM-2 -pH 300°C

Figure 4 :

 4 Figure 4: CATTENOM-2 -Activities deposited on the hot legs

  tend to decrease for the first cycles and then stabilize. The 60 Co surface activities increase for 6 to 8 first cycles and then stabilize. In general, 51

Figure 6

 6 Figure 6: CATTENOM-2 -58 Co and 60 Co activities deposited on the SG tubes (cold and hot sides)

  59

Figure 7

 7 Figure 7: CATTENOM-2 -58 Co and 60 Co volume activities

Figure 9 :Figure 10 :

 910 Figure 9: CATTENOM-2 -Soluble and particulate activities

Figure 11 :CAT2

 11 Figure 11: DAMPIERRE-1 -Operating parameters Figure 12: DAMPIERRE-1 -pH 300°C

Figure 15 :

 15 Figure 15: GOLFECH-2 -Operating parameters Figure 16: GOLFECH-2 -pH 300°CThe coolant temperature, the CVCS flowrate, the boron, dihydrogen and dioxygen concentrations during the cold shutdown of cycle 2 are presented in Figure17. Figure18shows the comparison of the calculated and measured 58 Co volume activities.

Figure 17 1 :

 171 Figure 17: GOLFECH-2 -Cycle 2 Cold shutdown procedure

OSCAR : Outil de Simulation de la ContAmination en Réacteur (tOol of Simulation of ContAmination in Reactor)

RCS : Reactor Coolant System -CVCS : Chemical and Volume Control System -RHRS : Residual Heat Removal System

Paper Reference n° 193 P1-24

Surface activities

Figure 13 and Figure 14 Mn surface activities calculated using OSCAR V.1.2 with the surface activities measured at the beginning of some unit outages (cycles 1 to 3, 6 to 13 and 15) using the EMECC system for the Hot Legs (HL) and the Steam Generator tubes (SG) (cold side). The simulation correctly reproduces the levels and the trends of the surface activities of the primary system before and after SGR: The average differences over the cycles between the calculated and measured activities are less than a factor of 2. Mn. Before SGR, the 58 Co surface activities tend to decrease with cycles. After SGR, they increase for two cycles and then decrease. Before SGR, the 60 Co surface activities increase for the first 5 to 7 cycles and then stabilize. After SGR, they are stagnant or even decrease on the primary pipes and they increase on the new SG tubes. The SGR impact is quite suitably reproduced with OSCAR PC V1.2. The increase in the 58 Co surface activities for the first cycles after SGR is due to a high Ni release from the new SG tubes during the formation of an inner protective oxide layer on the fresh alloy surfaces and also due to the state of the circuit cleanliness after a SGR process [START_REF] Dacquait | The impact of steam generator replacement on PWR primary system contamination[END_REF]. After SGR, the decrease in the 60 Co surface activities on the primary pipes and the increase by a lower rate than before SGR on the SG tubes are due to the lower Co content and a lower corrosion rate of the replacement SG tubes.

SIMULATION OF A COLD SHUTDOWN

Physico-chemical conditions significantly vary during cold shutdowns: power, temperature and pH decrease and primary coolant oxygenation. These changes lead to corrosion product releases in the primary coolant. The RCS oxygenation in particular causes a large dissolving of the in-core Ni° deposit. The metallic nickel deposit dissolution involves the dissolution of Co peak activity then appear, typically, of the order of several ppm and 100 GBq/Mg, respectively [START_REF] Dacquait | Corrosion product transfer in French PWRs during shutdown[END_REF] (except for PWRs equipped with improved manufacturing process SG tubes [START_REF] Dacquait | Low Primary System Contamination Levels in Some French PWRs[END_REF]). To simulate these releases, it is necessary: to know the solid speciation of the crud on fuel elements (calculated by OSCAR/PHREEQCEA), to vary the phase dissolution velocities (V dissol , see §2.2.1) as a function of the temperature,


Alexandre Ferrer

Frédéric Dacquait

Benoit Gall

Gilles Ranchoux

Mathieu Corbineau

The OSCAR code: modelling and simulation of the corrosion product behaviour under nucleate boiling conditions in PWRs

Keywords: Corrosion products, nucleate boiling, PWR, OSCAR

The PWR primary circuit materials are subject to general corrosion leading to metallic elements (mainly Fe, Ni, Cr, Mn, Co) transfer and subsequent ion precipitation and particle deposition processes on the primary circuit surfaces. When deposited on fuel rods, these species are activated by neutron flux. Thus, crud erosion and dissolution processes result in primary coolant activities. During a normal operating cycle in an EDF PWR, the volume activities in the coolant are relatively stable (usually about 10-30 Bq.g-1 in 58Co). During some cycles (depending on fuel management), a significant increase in 58Co and 51Cr volume activities can be observed (10 to 100 times the ordinary volume activities). This increase in volume activities is due to local sub-cooled nucleate boiling on the hottest parts of some fuel assemblies. Indeed, it is well known that nucleate boiling enhances the deposition and precipitation processes.

Crud growth in boiling conditions is related to different phenomena:

 Enrichment: concentration increases at crud-coolant interface,  Boiling deposition by vaporisation: fluid vaporization at wall results in particle deposition and ion precipitation. As the crud growth, boiling occurs in the crud itself, so do the ion precipitation and deposition of the small particles.  Boiling deposition by trapping: some of the small particles trapped at the interface bubble/fluid make deposit when a bubble leaves the wall.  Enhanced erosion: turbulences generated by bubbles collapsing close to the wall and spalling above a certain deposit thickness enhance erosion; it results in the release of particle agglomerates. These phenomena have been modelled in the OSCAR V1.3 code.

In this article, we present the modelling of these mass transfer mechanisms in boiling conditions and we show that the crud amount on fuel rods and the volume activities in the primary coolant in case of boiling calculated by OSCAR are in accordance with the experimental feedback on French PWRs.

INTRODUCTION

The PWR primary circuit materials are subject to general corrosion leading to metallic elements (mainly Fe, Ni, Cr, Mn, Co) transfer and subsequent ion precipitation and particle deposition processes on the primary circuit surfaces. When deposited on fuel rods, these species are activated by neutron flux. Thus, crud erosion and dissolution processes result in primary coolant activities. During a normal operating cycle in an EDF PWR, the volume activities in the coolant are relatively stable (usually about 10-30 Bq.g -1 in 58 Co). During some operating cycles (depending on fuel management), a significant increase in 58 Co and 51 Cr volume activities can be observed (10 to 100 times the ordinary volume activities) generally in the second half of the cycle (see Figure 1). The PWR operation feedback shows that the volume activities in these cases are mainly due to particles, indicating that these increases in volume activities are due to erosion of thick crud on fuel rods. This thick crud is due to local sub-cooled nucleate boiling on the hottest parts of some fuel assemblies. Indeed, it is well known that nucleate boiling enhances the deposition and precipitation processes. The thickness of the crud layer can reach 100 µm in boiling areas and it is sometimes linked to CIPS (Crud Induced Power Shift) in extreme cases [START_REF] Epri | PWR Axial Offset Anomaly (AOA) Guidelines[END_REF]. The modelling of the crud growth and erosion fluxes in cases of non-boiling and boiling flows are essential to enable calculations of surface masses and volume activities in the coolant.

In partnership with EDF and Areva NP, the CEA has developed the OSCAR calculation code to predict the surface and volume activities in the PWR primary circuit and the amount of deposited/precipitated material on the primary circuit surfaces [START_REF] Dacquait | Simulations of corrosion product transfer with the OSCAR V1.2 code[END_REF]. One further improvement of this calculation code is the simulation of the deposited/precipitated/eroded material due to nucleate boiling. This development was the subject of a PhD thesis [START_REF] Ferrer | Modélisation des mécanismes de formation sous ébullition locale des dépôts sur les gaines de combustible des Réacteurs à Eau sous Pression conduisant à des activités volumiques importantes[END_REF] and is presented in this paper.

In a first part we will present the phenomenology of the crud growth, then the mass transfer mechanisms in nucleate boiling conditions developed for the OSCAR code and finally the crud amount on fuel rods and the volume activities in the primary coolant in case of boiling calculated by OSCAR and their comparison to the experimental feedback on French PWRs.

PHENOMENOLOGY OF CRUD GROWTH

In a region with sub-cooled nucleate boiling, the crud can be described as a porous media. The void proportion in the magnetite crud was measured to be about 60% to 70% according to Macbeth [START_REF] Macbeth | An investigation into effect of crud deposits on surface Temperature, dry-out and pressure drop, with forced convection boiling of water at 69 bar in an annular test section[END_REF] and Jones [START_REF] Jones | Modeling and Thermal Performance Evaluation of Porous Crud Layers in Sub-Cooled Boiling Region of PWRs and Effects of Sub-Cooled Nucleate Boiling on Anomalous Porous Crud Deposition on Fuel Pin Surface[END_REF]. The pore size is of the order of the particle size in the coolant with a typical pore diameter size between 0.1 and 0.5 μm. Furthermore, the formation of a very regular distribution of large pore holes (diameter of about 5 µm) penetrating deep into the deposit is observed (these are called chimneys) [START_REF] Macbeth | An investigation into effect of crud deposits on surface Temperature, dry-out and pressure drop, with forced convection boiling of water at 69 bar in an annular test section[END_REF].

In the case of local nucleate boiling, two cases may arise:  the coolant/crud interface (wall) temperature Tw is equal to the wall boiling temperature Tb (Case 1),  the coolant/crud interface temperature is lower than the wall boiling temperature, critical temperature for boiling may only occur inside the crud above a given thickness (Case 2). In Case 1, boiling occurs directly at the wall. As illustrated in Figure 2, in the case of local nucleate boiling at the surface, phenomenology of crud growth can be divided into three mains steps:

 Boiling starts at the crud/fluid interface as soon as boiling temperature is reached. It is worth pointing that boiling process needs an overheat (ΔTsat), boiling temperature being Tb = Tsat + ΔTsat (Figure 2.a).  Crud is formed on fuel rod clad due to particle deposition and ion precipitation, which are enhanced by boiling. Since crud is a high porosity medium, boiling can start with a lower boiling temperature than in the case of a heated flat surface in contact with the fluid. So, as the crud grows, boiling process is not located anymore at the coolant/crud interface but in the crud itself (Figure 2.b).  To run this process, porosity feeds the boiling with fluid thanks to capillarity pumping action [START_REF] Macbeth | An investigation into effect of crud deposits on surface Temperature, dry-out and pressure drop, with forced convection boiling of water at 69 bar in an annular test section[END_REF][START_REF] Pan | Concentration level of solutes in porous deposits with chimneys under wick boiling conditions[END_REF]. This operating mode generates chimneys through action of the steam exhaust and feeds surrounding crud (Figure 2.c). This induces progressive filling of the porosity with ions and particles as well as crud thickness increases. In Case 2, where the wall temperature is slightly lower than the boiling temperature, the process also implies three phases illustrated in Figure 3:  The crud grows in a first phase by particle deposition and ion precipitation in singlephase flow (see Figure 3.a). The oxide/crud interface temperature increases as the crud grows (effect of the crud thermal resistivity).  When oxide/crud interface reaches the boiling temperature, bubbles are created by boiling action inside the crud (see Figure 3.b). Boiling is fed by coolant fluid pumped through capillarities. This fluid motion generates porosity filling inside the crud as well as crud extension at crud/fluid surface (so porosity decreases in the crud).  This process can go up the generation of a superheated vapour layer at the oxide/crud interface. Thanks to crud inhomogeneities, some steam exit paths may be favoured, inducing chimneys creation in further crud grow process as it is the case in Case 1 (see Figure 3.c).

MODELLING OF MASS TRANSFER MECHANISMS IN BOILING CONDITIONS

Enrichment phenomenon

Boiling action at the wall or in the crud implies an imbalance between ion and particle radial advection flows from the coolant to the wall region and from the wall region to the coolant. Thus, ion and particle concentrations near the wall are higher than the ones in single-phase flow [START_REF] March | Caractérisation et modélisation de l'environnement thermodynamique et chimique des gaines de combustible des réacteurs à eau sous pression en présence d'ébullition[END_REF]. This phenomenon is called "enrichment". The ratio of the wall concentration Cwall to the coolant concentration without boiling C0 is called "enrichment factor" FE, for a considered species:

0 wall E C C F  (1)
The enrichment factor can be moderated if particles and ions are absorbed by the capillarity action to feed boiling in case of boiling in the crud.

Enrichment factor -Boiling at the wall (Case 1)

In order to give a realistic description of the enrichment factor when nucleate boiling occurs directly at the wall, we consider the fluid as three layers radially organized around fuel rod (See Figure 4) [START_REF] March | Caractérisation et modélisation de l'environnement thermodynamique et chimique des gaines de combustible des réacteurs à eau sous pression en présence d'ébullition[END_REF]:

 The first layer, called Zone L, is the laminar layer. We assume that the ion and particle concentrations (Cwall) are constant in this region.  The second layer, called Zone P, composes the intermediate zone. In this intermediate layer, turbulences tend to homogenize the fluid temperature and species concentrations. The thickness of this fluid layer is assumed to be equal to the detachment radius of bubbles, namely a few tens of micrometers.  The last layer, called Zone C, is fully turbulent. The average void fraction is considered to be less than 2% in this zone. In order to estimate the enrichment factor, a mass balance is done at the wall vicinity based on this three-layer structure and on the assumption that the superheated fluid layer thickness is thin enough to neglect recondensation effect. The thickness of this superheated layer is supposed to be equal to the bubble radius at detachment. By a mass balance in Zone P and Zone L and assuming that:

Cp = k . Cwall + (1 -k) . Cc (2)
with k a constant depending on the thicknesses of Zone P and Zone L, March [START_REF] March | Caractérisation et modélisation de l'environnement thermodynamique et chimique des gaines de combustible des réacteurs à eau sous pression en présence d'ébullition[END_REF] obtained:

x ) x 1 ( 1 C C 0 C      (3) and   x ) x 1 ( 1 1 n 1 ) 1 ( k / 1 n C C C C F c c 0 C C wall E               (4)
with nc the circulation number ( The enrichment factor of equation ( 4) is only valid in the case of boiling at the wall. When boiling occurs in the crud, particles and ions are trapped due to capillarity action. The corrosion products concentration is very close to the equilibrium concentration and they are not volatile. So, we can consider that each particle or ion driven by the capillary forces is trapped in or on the crud (deposition/precipitation). A flow balance in the crud shows that the pumped liquid flow rate Gpump in the crud is equal to the vaporization rate v m  corresponding to the liquid mass vaporized and driven to the bubbles nucleation sites:

Gpump = v m  (5)
Considering the pumping action, we have:

Gc-p = Gp-c + v m  (6)
Gc-p . Cc = Gp-c . Cp + Gpump . Cwall (7)

By combining equations ( 2), ( 3), ( 5), ( 6) and ( 7), we obtain Cwall/CC = 1 and then the enrichment factor in Case 2 is equal to:

x ) x 1 ( 1 F E      (8)
For corrosion products under PWR conditions, the mass quality and the volatility being almost 0, the enrichment factor in Case 2 is practically equal to 1.

Between the extreme values of the enrichment factor of Case 1 and Case 2, we have defined a linear interpolation as a function of the thicknesses of the crud and the fluid layer under a bubble [START_REF] Ferrer | Modélisation des mécanismes de formation sous ébullition locale des dépôts sur les gaines de combustible des Réacteurs à Eau sous Pression conduisant à des activités volumiques importantes[END_REF]. The enrichment factor decreases with the crud growth due to the pumping effect (see an illustration in Figure 5).

Enrichment -Precipitation/Dissolution at the wall

The mechanisms of precipitation and dissolution at the wall of the OSCAR code [START_REF] Dacquait | Simulations of corrosion product transfer with the OSCAR V1.2 code[END_REF] are modified to take into account the enrichment at the wall.

The expression of the precipitation rate [kg.m -2 .s -1 ] becomes:

) C C F ( h dt dm equil 0 E     (9)
and the dissolution rate:

) C F C ( V 1 h 1 1 dt dm 0 E equil dissol      (10)
with h the mass transfer coefficient of ions in the fluid [m.s -1 ], Vdissol the dissolution velocity coefficient (dissolution surface reaction rate coefficient) [m.s -1 ], FE the enrichment factor, C0 the bulk concentration of an element [kg.m -3 ] and C equil the equilibrium concentration of the element [kg.m -3 ] calculated by the OSCAR chemistry module, PhreeqCEA [START_REF] Plancque | Role of chemistry in the phenomena occurring in nuclear power plants circuits[END_REF].

Boiling deposition

Boiling deposition by vaporization

Particles contained in the fluid sub-layer vaporized during the growth of a bubble are deposited on the wall. As well, non volatile ions contained in this fluid sub-layer precipitate directly on the wall or precipitate on particle contained in the sub-layer and then are deposited. Thus, note that the term "deposition by vaporization" also refers to precipitation by vaporization. We propose to use the following mechanism for the boiling deposition by vaporization. This mechanism is based on Asakura studies [START_REF] Asakura | Deposit of Iron Oxide on Heated Surfaces in Boiling Water[END_REF]. The boiling deposition rate by vaporization [kg.m -2 .s -1 ] is expressed by:

0 E v vap C F m K dt dm      (11)
with Kvap a constant (see below), v m  the vaporization rate [kg.m -2 .s -1 ], FE the enrichment factor and C0 the ion/particle concentration in the bulk [kg.kg -1 ]. The main differences with the Asakura expression are:  Use of the vaporization rate v m  instead of the maximum vaporization rate L  (L: latent heat of vaporization). Indeed, in the Asakura experiment, the flow at the end of the test section is in vapour form. In our case, the void fraction at the end of the core is about 1% to 2%;  For a given species, use of the wall concentration Cwall = FE . C0 (higher ion/particle concentration in a boiling region close to the wall due to boiling) instead of the bulk concentration;  Extension to ionic species, ions contained in the micro-layer precipitate due to the increase of the concentration by vaporization of this fluid micro-layer.

Calculation of Kvap -Boiling at the crud/fluid interface

According to Asakura, the Kvap constant is the ratio of the volume used to form the dry region (V2) to the total volume used to form a bubble during step 2 to step 3 (V1). These volumes are schematized in Figure 6. The Kvap constant calculated by geometric relations is equal to [START_REF] Ferrer | Modélisation des mécanismes de formation sous ébullition locale des dépôts sur les gaines de combustible des Réacteurs à Eau sous Pression conduisant à des activités volumiques importantes[END_REF]:

2 l v b b 3 1 2 vap R 3 4 2 1 V V K                       (12)
with Rb the maximum bubble radius (radius at detachment) calculated by the Unal model [START_REF] Unal | Maximum bubble diameter, maximum bubble-growth time and bubblegrowth rate during the subcooled nucleate flow boiling of water up to 17.7 MN/m²[END_REF], b the maximum micro-layer thickness calculated by the Torigai model [11], v and l respectively the density of vapour and liquid.

Note that the expression of the Kvap constant calculated here is different than the Asakura one by a factor 1/2. The expression considered in our study (blue curve) fits very well with the values of Charlesworth [START_REF] Charlesworth | Chemical Engineering Program Symposium Series[END_REF] (one of the two values), Rassokhim [START_REF] Rassokhim | Iron oxide deposits on heat surfaces and their removal High Temperature and High Pressure Electrochemistry in Aqueous Solutions[END_REF] and Turner [START_REF] Turner | Modelling magnetite particle deposition in nuclear steam generator and comparison with data plant[END_REF].

Calculation of Kvap -Boiling in the crud

The Asakura expression of the deposition rate is only valid in the case of boiling at the crud/fluid interface. However, in the case where boiling occurs deeper in the crud, if we suppose that bubbles are formed with the same volume V1 between step 2 and step 3, all particles contained in this volume are trapped in the deposit by the capillary action. In this limit case, the particles and ions contained in the volume V1 are deposited or precipitated, thus the Kvap constant is equal to 1.

The Kvap constant increases as the crud grows. We propose to use a linear variation as a function of the maximum micro-layer thickness and the crud thickness from the value of Kvap calculated at the wall (eq. 12) and the value of 1 [START_REF] Ferrer | Modélisation des mécanismes de formation sous ébullition locale des dépôts sur les gaines de combustible des Réacteurs à Eau sous Pression conduisant à des activités volumiques importantes[END_REF].

Boiling deposition by trapping

Basset et al. [START_REF] Basset | Deposition of particles onto alloy-800 Steam Generator Tubes[END_REF] and Thomas et al. [START_REF] Thomas | Experimental investigation of the deposition of suspended magnetite from the fluid flow in steam generating boiler tubes[END_REF] observed another kind of deposit (in sub-cooled boiling regions), deposit in form of ring, different than the one formed by micro-layer vaporization studied by Asakura (deposit in form of spot). They explained the ring formation by the fact that small particles (i.e. colloids) are trapped at the liquid/vapour interface and when a bubble grows, particles slide on the bubble and settle around the base of the bubble at the crud/fluid interface. Basset and Thomas proposed to use the Asakura formalism for this phenomenon. The form of the deposit is different, so we can think that the mechanism must be different, but the driving factor is the vaporization rate as the Asakura mechanism. The constant Ktrap can be defined as the ratio of the volume of a particle skin around the bubble Vskin to the volume evaporated V1.

The boiling deposition rate by trapping [kg.m -2 .s -1 ] is based on the Lister and Cussac model [START_REF] Lister | Modelling of particulate fouling on heat exchanger surfaces: influence of bubbles on iron oxide deposition[END_REF] and is expressed by:

           part 0 E v trap C 2 F 1 m K dt dm  (13) with dt V V K t 0 1 skin trap     (14)
and ξ the proportion of particles trapped at the vapour/liquid interface, Vskin the volume of the particle skin, V1 the volume evaporated to form a bubble, v m  the vaporization rate [kg.m -2 .s -1 ], FE the enrichment factor and part 0 C the particle concentration in the bulk [kg.kg

-1 ],         part 0 E C 2 F 1
is the average particle concentration around a bubble.

Erosion in boiling conditions

The erosion rate is higher in a two-phase flow than in a single-phase flow due to the turbulences generated by the bubbles collapsing close to the wall [START_REF] Lister | Modelling of particulate fouling on heat exchanger surfaces: influence of bubbles on iron oxide deposition[END_REF]. Furthermore, above a certain crud thickness, the deposit is eroded by spalling, thus releasing large particle agglomerates. The erosion rate in boiling conditions [kg.s -1 ] is expressed by:

1 ln E             
the erosion coefficient [s -1 ] (based on the Cleaver and Yates model [START_REF] Cleaver | Mechanism of detachment of colloidal particles from a flat substrat in a turbulent flow[END_REF]), wall the shear stress at the wall [kg.m -1 .s -2 ], Kboil a constant in boiling conditions which is calibrated, fluid the dynamic viscosity of the fluid [kg.m -1 .s -1 ], the resistance to erosion (Zakharov model [START_REF] Zakharov | Bond strength of coating applied by the flame plating technique[END_REF]) and merod the mass [kg] which can be eroded and which depends on a spalling thickness.

SIMULATIONS IN BOILING CONDITIONS USING THE OSCAR CODE

Comparative study of the mass transfer mechanisms in boiling conditions

In

Simulation of a PWR case

The case is a 1300 MWe PWR (the description of the primary circuit is given in [START_REF] Dacquait | Simulations of corrosion product transfer with the OSCAR V1.2 code[END_REF]). The first 4 operating cycles are simulated, the 2 first ones without boiling and the following ones with sub-cooled nucleate boiling. Boiling starts during cycle 3 and from the beginning of cycle 4. It is localized on the penultimate grid span (region C7 where the cladding temperature is the highest) of 1/3 of the fuel assemblies (Zone A of the core) which accounts for around 4% of the total fuel surface. The average heat flux density is 0.6 MW.m -2 ; the temperatures and the power factor are given in The crud thicknesses in regions C7A (with boiling) and C7B (without boiling) are presented in Figure 9. The maximum crud thickness is some µm without boiling, whereas it reaches 30 µm in sub-cooled boiling conditions. The crud is rich in Fe (and Ni) in boiling conditions, reflecting the fact that iron precipitates on the upper part of the fuel assemblies in boiling conditions (see Figure 10), whereas it is not the case in single-phase conditions. The crud thickness and composition are consistent with experimental data. Note that the deposit thickness is mainly determined by the vaporization rate (depending on the average heat flux density and the power factor) and by the erosion rate which is calibrated. The erosion rate being higher in boiling conditions, the 58 Co volume activity and, to a lesser extent, the 51 Cr one increase a lot, up to 200-300 Bq.g -1 in 58 Co and 50-100 Bq.g -1 in 51 Cr (see Figure 11). The increase in 60 Co and 54 Mn is low. Due to the stretch-out, the volume activities tend to decrease because the boiling conditions are not met anymore. These levels and variations are consistent with the experimental feedback (see Figure 1). As the crud growth, boiling occurs in the crud itself, so do the ion precipitation and deposition of the small particles. In PWR sub-cooled nucleate boiling conditions, this crud growth mechanism is the major one.  Boiling deposition by trapping: some of the small particles trapped at the interface bubble/fluid make deposit when a bubble leaves the wall.  Enhanced erosion: turbulences generated by bubbles collapsing close to the wall and spalling above a certain deposit thickness enhance erosion; it results in the release of particle agglomerates. OSCAR simulations have shown that predicted crud thickness on fuel rods as well as volume activities in the primary coolant under nucleate boiling conditions are in good agreement with the field experience of French PWRs.

Figure 1 .

 1 Figure 1. 58 Co, 60 Co, 51 Cr and 54 Mn volume activities during an operating cycle with increase in 58 Co and 51 Cr

Figure 2 .

 2 Figure 2. Illustration of crud growing process in Case 1. Wall temperature is above the wall boiling temperature (Tw = Tb)

Figure 3 .

 3 Figure 3. Illustration of crud growing process in Case 2. Wall temperature is below the wall boiling temperature (Tw < Tb)

Figure 4 .

 4 Figure 4. Illustration of the three fluid regions model in Case 1

  -p the fluid radial flow rate from Zone C to Zone P and v m  the vaporisation rate), x the mass quality and the volatility of a considerate species. 3.1.2 Enrichment factor -Boiling in the crud (Case 2)

Figure 5 .

 5 Figure 5. Enrichment factor as a function of the crud thickness for different values of heat flux density  (P = 155 bar, G = 3500 kg . m -2. s -1 )

Figure 6 .

 6 Figure 6. Bubble growth on a heated surface Figure 7 presents the variation of the Kvap constant with pressure, experimental data are reported.The expression considered in our study (blue curve) fits very well with the values of Charlesworth[START_REF] Charlesworth | Chemical Engineering Program Symposium Series[END_REF] (one of the two values), Rassokhim[START_REF] Rassokhim | Iron oxide deposits on heat surfaces and their removal High Temperature and High Pressure Electrochemistry in Aqueous Solutions[END_REF] and Turner[START_REF] Turner | Modelling magnetite particle deposition in nuclear steam generator and comparison with data plant[END_REF].

Figure 7 .

 7 Figure 7. Variation of Kvap with pressure

Figure 8 .

 8 Figure 8. Impact of each mechanism on the crud thickness in PWR conditions with sub-cooled nucleate boiling

Figure 9 .Figure 10 .

 910 Figure 9. PWR simulation -Crud thickness on grid span C7 with and without boiling

Figure 11 .

 11 Figure 11. PWR simulation -Volume activities of the primary coolant

Table

Table 1 . PWR simulation -Temperatures and power factor of region C7 with and without boiling

 1

	Region C7	Without boiling	With boiling
	Bulk temperature (°C)	323	325
	Wall temperature (°C)	338	345
	Power factor	1.08	1.2

. The PWR operates in Stretch-Out ("SO" in the figures below) at the end of cycle 4.

NPC 2014 SAPPORO


Marie Bultot

Frédéric Dacquait

Etienne Tevissen

Kim Schildermans

Raphaël Lecocq

Zinc effect on the primary circuit contamination of a Belgian PWR using the OSCAR V1.3 code Paper Number: 80

The purpose of the OSCAR code, developed by the CEA in collaboration with EDF and AREVA NP, is to simulate the contamination of the PWR (Pressurized Water Reactor) primary system. The OSCAR code, coupled to its chemistry module PHREEQCEA, allows researchers to analyse the corrosion product behaviour and to calculate the volume and surface activities of a primary system. It synthesizes knowledge and allows us to progress in understanding the phenomena involved in the contamination caused by activated corrosion products.

The OSCAR V1.3 code has been used to simulate the effect of zinc on the primary circuit contamination of a Belgian PWR operated by ENGIE. This paper highlights the physicochemical phenomena involved during a zinc injection. The OSCAR simulation shows that:  Zinc precipitates on the inner oxide (Cr-rich layer) instead of cobalt showing that zinc has a better affinity than cobalt with chromites (change in the Co equilibrium concentration).  Cobalt concentration and 58 Co and 60 Co activities increase in the primary coolant and on the outer oxide of both the in-core and out-of-core surfaces (Fe-rich layer). Different plants have observed this increase during the first cycles of Zn injection.  An antagonist effect exists between the decreasing 58 Co and 60 Co activities of the inner oxide and the increasing activities of the outer oxide, which explains the slight impact of a zinc injection observed by EMECC campaigns.

INTRODUCTION

The purpose of the OSCAR code, developed by the CEA in collaboration with EDF and AREVA NP, is to simulate the contamination of the PWR primary system [START_REF] Dacquait | Simulations of corrosion product transfer with the OSCAR V1.2 code[END_REF]. The OSCAR code, coupled to its chemistry module PHREEQCEA (a version of the PHREEQC code [START_REF] Parkhurst | User's guide to PHREEQC (version 2) -A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations[END_REF] extended to the PWR temperature range) in combination with a thermodynamic database developed by the CEA [START_REF] Plancque | Role of chemistry in the phenomena occurring in nuclear power plants circuits[END_REF], allows researchers to analyse the corrosion product behaviour and to calculate the volume and surface activities of a primary system. It synthesizes knowledge and allows us to progress in understanding the phenomena involved in the contamination caused by activated corrosion products.

The OSCAR V1.3 code is used to simulate the effect of zinc injection on the primary circuit contamination during 3 cycles after 22 operating cycles of a Belgian PWR, hereinafter referred to as Reactor A, operated by ENGIE. Firstly we present the simulation of the first 22 cycles of Reactor A without zinc injection and then during the 3 following cycles with zinc. In the last part, we highlight the physical phenomena involved by a zinc injection. Brighton, United Kingdom -October 2-7, 2016 Paper Number: 80

SIMULATION OF THE FIRST 22 CYCLES OF REACTOR A WITHOUT ZINC INJECTION

Reactor A is a 3-loop PWR equipped with alloy 690 tubed steam generators from the Steam Generator Replacement (SGR) at cycle 11.

The structure of the primary circuit is described by control volumes using the design data of the reactor (wetted surfaces, hydraulic diameters, material compositions, nominal temperatures…). The operation data (water chemistry, reactor power) is averaged to obtain a few-day step simulation.

As a matter of comparison, we use the surface activities measured with the EMECC device [START_REF] Eimecke | Ensemble de Mesures et d'Etude de la Contamination des Circuits[END_REF] during the shutdowns at the end of cycles 9, 14 and 22 and the volume activities measured by ENGIE during power operation (data available from cycle 13). The results focus on the activities of 58 Co and 60 Co because of their major contribution to the dose rates around the primary system. Figure 1 and Figure 2 present the simulation-measurement comparison of 58 Co and 60 Co activities deposited on the primary surfaces (hot legs, crossover legs and hot and cold sides of the Steam Generator (SG) tubing). Figure 3 presents the simulation-measurement comparison of 58 Co and 60

Co volume activities of the primary water during power operation.

There is a relatively good agreement between the simulation and the measurements of the 58 Co and 60 Co deposited activities. The calculated contamination trends are consistent with the measured ones, in particular the variations due to the SGR at the end of cycle 11 (at about 4200 days): there is an increase and then a decrease in the 58 Co contamination. The 60 Co contamination level is lower after SGR.

Figure 3 shows that the calculated 58 Co and 60 Co volume activities during power operation are consistent with the measurements (about 10 Bq/g for 58 Co and between 0.1 and 1 Bq/g for 60 Co). Note that the measured peak volume activities correspond to the cold shutdowns at the end of cycles which have not been modelled accurately in this simulation but their effects have been taken into account by the OSCAR code. This simulation illustrates the ability of the OSCAR code to simulate the contamination transfer of a reactor during several cycles, given design and operating data.

Hot legs

Crossover legs

SIMULATION OF THE 3 FOLLOWING CYCLES OF REACTOR A WITH ZINC INJECTION

The OSCAR V1.3 code is used to simulate the effect of zinc on the primary circuit contamination of Reactor A during 3 cycles. Two calculations are performed by adding 3 cycles similar to the 22 nd cycle:

 A reference simulation without a zinc injection during those 3 cycles.  A simulation with a target Zn concentration of 15 ppb during those 3 cycles.

20 th NPC International Conference Brighton, United Kingdom -October 2-7, 2016

Paper Number: 80

Injection rate and zinc concentration

The zinc concentration calculated by using OSCAR of the primary coolant during cycles 23 to 25 is presented in Figure 4. To obtain the target level of 15 ppb after several operating months with zinc injection, the injection rate of zinc, depleted in 64 Zn, is set to the following values:

 65 g/day during the first 9 months of the 23 rd cycle  13 g/day during the 11 remaining months of the 23 rd cycle  12 g/day during the 24 th cycle  11 g/day during the 25 th cycle.

After 150 injection days, the zinc concentration is above 1 ppb and it is stabilized at about 15 ppb after a 280-day duration.

Figure 4: OSCAR simulation -Zinc concentration of the primary coolant. Co and 60 Co volume activities is commonly observed when zinc is injected in a PWR, for instance see [START_REF] Tigeras | Complete Analyse of Zinc injection impact at BUGEY 2&4[END_REF].

Volume and surface activities

The 65 Zn volume activity ranges between 0.2 and 2 Bq/g as the zinc concentration is about 15 ppb, which is consistent with the on-site measurements when zinc is depleted in 64 Zn. To illustrate the impact of zinc injection on the surface contamination of the primary system, Figure 6 presents the comparison between the simulated 58 Co and 60 Co surface activities on the hot legs, cold legs, cold side of the SG tube bundles (the impact is practically the same on the SG hot side) and the total 58 Co and 60 Co activities deposited on the fuel rods with and without zinc injection.

When zinc is injected, the 58 Co surface activity increases at the end of cycle regardless of the region and the cycle. For the 60 Co surface contamination, it depends on the region and the cycle. At the end of the first cycle with zinc, there is no significant difference between 60 Co contaminations on the primary loops with and without zinc injection, except on the fuel elements where the 60 Co contamination is higher when zinc is injected; and then the gaps become larger and larger. At the end of the third cycle, the 60 Co activity deposited on the primary surfaces increases with zinc injection, the hot legs excepted.

Table 1 shows the impact of 3 cycles with 15 ppb of zinc on the 58 Co and 60 Co activities deposited on the primary circuit. According to the OSCAR simulation, there is a beneficial impact of zinc on the primary system contamination for the sole 60 Co activity deposited on the hot legs. The impact on the contamination of the out-of-flux surfaces and on the 58 Co contamination of the fuel elements is relatively low after 3 cycles with zinc injection (less than about +30%). On the other hand, the impact on the 60 Co contamination of the fuel elements is high (about +80%). This impact is consistent with the field experience based on EMECC campaigns which shows that zinc has a slight effect on the contamination of old oxidized surfaces, but a strong increasing effect on the 60 Co contamination deposited on the fuel elements (increase in the 60 Co peak activity during cold shutdown when zinc is injected [START_REF] Tigeras | Complete Analyse of Zinc injection impact at BUGEY 2&4[END_REF]).

ANALYSIS OF THE PHYSICOCHEMICAL PHENOMENA IN THE PRESENCE OF ZINC

Due to its great affinity for chromite [START_REF] Lister | Activity transport and corrosion processes in PWRs[END_REF], zinc changes the stability of the chromium-rich solid solution, i.e. the stability of the inner oxide. Zinc greatly incorporates in the inner oxide and has an impact on the equilibrium concentrations of chemical elements, including cobalt in particular, with the inner oxide. In the OSCAR code, the equilibrium concentration of each chemical element and the oxide speciation are calculated by PHREEQCEA. The PHREEQCEA code determines the composition of the ideal solid solution (mixed oxides and any pure solid phases possibly in excess) and the equilibrium concentration of each element in relation to the chemical conditions (pH, H 2 , O 2 ), the coolant temperature and the masses of the metallic elements of the considered oxide in each region. Figure 7 presents the comparison between the Co concentrations in the bulk in equilibrium with the inner oxide of the steam generator tubing calculated by PHREEQCEA with and without zinc injection. The presence of zinc increases the equilibrium concentration of Co in the bulk. This increase results in a change of the system of dissolution/precipitation of Co: cobalt has a tendency to precipitate on the inner oxide until the end of the incubation phase (phase during which Zn greatly precipitates on the inner oxide up to its saturation). It then has a tendency to dissolve after the incubation phase (see Figure 8). The OSCAR code provides an explanation of some physicochemical phenomena involved in the contamination by activated corrosion products in the presence of zinc. This explanation is in accordance with the assessment of the EMECC campaigns carried out in PWRs in which zinc is injected. It should be pointed out that no specific mechanism has been added to the OSCAR code to reproduce the effect of zinc on the water chemistry (see [START_REF] Dacquait | Simulations of corrosion product transfer with the OSCAR V1.2 code[END_REF] for the corrosion product transfer modelling). It should also be noted that the effect of zinc on the corrosion [START_REF] Harding | Modelling the effect of zinc addition on the uptake of cobalt by oxide films in PWRs[END_REF] is not taken into account in OSCAR V1.3, but this effect is of second order for old oxidized surfaces such as those of Reactor A. Nevertheless, this effect will be taken into account in OSCAR V1.4 which is scheduled to be released in 2017.

CONCLUSION

Based on an OSCAR V1.3 simulation, the study of zinc injection in a Belgian PWR shows that:

 Zinc incorporates in the inner oxide (Cr-rich layer) replacing cobalt because of zinc's higher affinity with chromite.  Cobalt concentration and 58 Co and 60 Co activities increase in the primary coolant and on the outer oxide of both the in-core and out-of-core surfaces (Fe-rich layer).  An antagonist effect is pointed out between the decreasing 58 Co and 60 Co activities of the inner oxide and the increasing activities of the outer oxide. It explains the slight impact of a zinc injection observed by EMECC campaigns.

NOMENCLATURE

Figure 1 .

 1 Figure 1. OSCAR simulation -58 Co and 60 Co surface activities on the hot legs and crossover legs -Comparison to EMECC measurements.

Figure 3 .

 3 Figure 3. OSCAR simulation -58 Co and 60 Co volume activities of the primary coolant -Comparison to measurements.

Figure 5

 5 Figure 5 presents the 58 Co, 60 Co and 65 Zn volume activities with and without zinc injection from cycle 23 to cycle 25. The 58 Co and 60 Co volume activities are twice as high during the zinc injection. An increase in the 58

Figure 5 :

 5 Figure 5: OSCAR simulation -58 Co, 60 Co and 65 Zn volume activities of the primary coolant with or without zinc injection.

Figure 7 .

 7 Figure 7. OSCAR simulation -Co concentration in the bulk in equilibrium with the inner oxide of the SG tubing cold side with and without zinc injection.

Table 1 .

 1 Impact of zinc injection on the 58 Co and 60 Co activities deposited on the primary surfaces at the end of cycle 25.

			Brighton, United Kingdom -October 2-7, 2016
			Paper Number: 80
		58 Co	60 Co
	Hot legs	+18%	-23%
	Cold legs	+32%	+34%
	SG hot side	+28%	+10%
	SG cold side	+27%	+10%
	Fuel rods	+23%	+84%

20 th NPC International Conference Brighton, United Kingdom -October 2-7, 2016 Paper Number: 80

It should be pointed out that cobalt always dissolves from the outer oxide (Fe-rich layer) regardless of the concentration of zinc. Zinc thus has no beneficial effect on the outer oxide, i.e. ferrites, as expected and it even has a detrimental effect. We have plotted the 60 Co activity of the inner oxide and the outer oxide of the SG tubing cold side with and without zinc injection in Figure 9. When zinc is injected, the 60 Co activity of the inner oxide (chromites) decreases due to the dissolution of cobalt (see Figure 8). This dissolution concerns not only 60 Co but also the other isotopes of Co including 58 Co and 59 Co which forms 60 Co by neutron activation. Therefore there is a double effect resulting in an increase of Co in the primary coolant: the precipitation of Co on the inner oxide stops and Co dissolves from the inner oxide. A part of this surplus of Co is deposited on the fuel elements leading to an increase in the formation of 60 Co (see Figure 6). This activated deposit is eroded and the particles are deposited on the outer oxide of the out-of-core components, including the SG tubing, resulting in an increase in the 60 Co contamination of this outer oxide (see Figure 9). Thus, there is a decrease in the 60 Co contamination of the inner oxide on the one hand and an increase in the 60 Co contamination of the outer oxide on the other. Depending on the region and time, it results in an increase, decrease or a stagnation of the 60 Co contamination of the out-of-flux surfaces (see Figure 6).


Disruptionen: Sprachliche und seelische Brüche in »Sam va mieux« von Alain Damasio Manuela Mohr, Université de Strasbourg, FR, manuela@easy-netpower.de

The writer Alain Damasio (1969-) is one of the best-known SF authors in France. Recently, Damasio has made a name for himself in the English-speaking world through various projects such as translations, blogs, animated films, video games and fan art based on his novels. In Damasio's fiction, disruptive elements interact on a structural and narrative level. The short story »Sam va mieux« (»Sam is doing better«, first published in 2010, republished in 2021) represents a particularly complex case in terms of use and functioning of disruption. The lonely protagonist imagines a counterpart -in this case a samovar -as his son Sam. This article deals with the concept of post-apocalypse, which is evoked by linguistic means. The short story's creative linguistic treatment of resistance to (uncomfortable) reality is intended to show that the hero's psychological defense mechanisms are based on disruption. The treatment of disruptive conditions in »Sam va mieux« points to Damasio's specific conception of the post-apocalyptic narrative. Sam and all the protagonist's other imaginary children serve functions that are central to post-apocalyptic fiction as a whole: a cathartic function (providing comfort), a critical and educational function (disillusionment and warning), and and an empowering and emancipatory function (maintaining agency). »Sam va mieux« explores the question of how agency unfolds despite the catastrophe and what effects can possibly be generated as a result. One possibility is the will to deal creatively with a changing world. Human beings have the potential and the duty not to suffer the world passively.

Der Schriftsteller Alain Damasio (1969-) Je suis la pluie qui grenaille sur le zinc, tu trottines comme elle sur les toits, à petits pas de moineau mat. Je suis l'eau qui ruisselle le long des huisseries, entre le plâtre et les châssis, le ruisseau en colimaçon, issu du sixième étage et qui cascade sur le bois de l'escalier que je remonte, trempé, avec Sam sur ton dos et le jerrican dans nos bras.

[…] Je suis les câbles qui rouillent et les poulies encore huilées, je suis le treillis que ta main décale avec un boucan de ferraille et le bouton d'appel qui s'allume encore, nous sommes les ascenseurs qui marchent après six ans sans aucune maintenance, sans aucune présence, pour ton plaisir. (Damasio, »Sam va

Aufbruch: In der Lüge liegt die Kraft

-Comment va Sam ce matin ?

-Sam va mieux.

-Vieux comment ?

-À peu près comme moi.

-Et comment va Sam ?

-Lui, ça va. Il me parle.

-Qui d'autre ?

-Plein de gens.

- -Dans toute la ville ?

-Je suis tout seul. Les cheminées aussi.

-Il y a moi quand même, non ? Tu ne me comptes pas ?

-Je ne te connais pas bien, alors... -Wie alt?

-Ungefähr so wie ich.

-Und wie geht es Sam?

-Ihm geht es gut. Er spricht mit mir.

-Wer sonst noch? -Viele Leute.

- -C'est mes petits frères, papa ? Je m'approche des niches aménagées dans les murs. Il y en a huit en tout. Et trois sont occupées. La première par un cylindre de bois, ouvragé de tubes et de trous. Une oeuvre de doux dingue.

-Tu t'en souviens ? -Non, Sam.

-C'est Jim. Il te parlait avec du vent, il était pas sage. T'as fait un an avec lui.

Le second est une petite harpe éolienne. Sur son cadre, c'est écrit »Line«.

Je tends ma torche vers la troisième niche... Un son très ample de didjeridoo monte dans la pièce, j'ai soudain la chair de poule, je frissonne violemment, des pieds à la tête, la torche tremble, je la lâche et je tends les mains vers le samovar en melchior qui trône dans la niche avec ces trois lettres gravées dessus : TOM (ibid. 287 f.) 21

  gehört in Frankreich zu den bekanntesten SF-Autoren. Im englischsprachigen Raum macht sich Damasio dank verschiedenster Projekte wie Übersetzungen, Blogs, Animationsfilme, Videospiele und Fanart zu seinen Romanen seit einigen Jahren einen Namen. Als politisch engagierter Autor tritt Damasio regelmäßig in Radiosendungen, an Konferenzen und Kundgebungen auf. In seinen Werken, die Elemente von SF, Dystopie, Fantastik und anderen verwandten Genres kombinieren, werden oft hoch technologisierte Geräte und komplexe Computersysteme in einem urbanen Umfeld in Szene gesetzt. Damasio selbst lebt ohne Smartphone, mal in einer abgelegenen Region auf Korsika, mal in den Bergen Frankreichs. In Damasios Fiktionen interagieren disruptive Elemente auf struktureller und narrativer Ebene miteinander. Die Kurzgeschichte »Sam va mieux« (»Sam geht es besser«, zuerst erschienen 2010 und kürzlich neu veröffentlicht in Aucun souvenir assez solide, 2021; dt. Keine ausreichend dauerhafte Erinnerung) stellt bezüglich der Verwendung und Funktionsweise der Disruption einen besonders komplexen Fall dar. Im postapokalyptischen Paris unserer Zeit scheinen eine namenlose Hauptfigur und ihr dreijähriger Sohn Sam nach weiteren Überlebenden zu suchen. Doch der Sprachfehler, den der Protagonist durch Ausspracheübungen beheben will, deutet schon früh an, was erst im Laufe der Handlung zur Gewissheit wird: Der einsame Protagonist, der an Schizophrenie leidet, imaginiert sich ein Gegenüber -in diesem Fall stellt er sich einen Samowar als seinen Sohn Sam vor. Das Verständnis dieser Zusammenhänge wird beim Lesen dadurch erschwert, dass die Erzählung auf den Vater fokalisiert ist und die Situation aus seiner Perspektive schildert. Damasio verwendet paradoxe grammatikalische Formulierungen und typografische Normabweichungen, wodurch die mentalen Prozesse des Helden nur langsam begreifbar werden. Schließlich wird klar, dass es vor Sam schon weitere imaginierte Figuren gegeben haben muss, die der Protagonist in Musikinstrumente oder Geräte, die Geräusche machen, projiziert und wieder verdrängt hat. Im deutschen und englischen Forschungsdiskurs ist Damasios Kurzgeschichte bislang unbeachtet geblieben. Der frankophone Raum zeigt vor allem am politischen Engagement Damasios Interesse, welches eng mit seiner schriftstellerischen Aktivität zusammenhängt. 1 Poetologische Herangehensweisen an Damasios Stil werden vom Autor selbst im Rahmen von Interviews vorgeschlagen, haben bislang aber keinen Eingang in die französische SF-Forschung gefunden. Dieser Beitrag hat zum Ziel, sich mit dem Konzept der Postapokalypse auseinanderzusetzen, die durch sprachliche 1 Siehe die zahlreichen Interviews mit Alain Damasio zum aktuellen französischen und internationalen Zeitgeschehen sowie Artikel über die emanzipatorische oder Hoffnung spendende Funktion von SF und dystopischer Literatur, die Damasio als Beispiel zitieren (vgl. Andrevon; Duret; Hopkins-Loféron). Mittel in der Fiktion evoziert wird. Die fiktionale Repräsentation der Apokalypse kann zur Abwendung der realen Apokalypse beitragen. Der sprachlich-kreative Umgang in der Kurzgeschichte mit dem Widerstand gegen die (unbequeme) Realität soll zeigen, dass die psychologischen Schutzmechanismen des Helden auf Disruptionen beruhen. Der Umgang mit disruptiven Bedingungen in »Sam va mieux« weist auf Damasios spezifische Konzeption der postapokalyptischen Erzählung hin: Denn weder rettet ein (männlicher) Held die Welt, noch vermittelt die Erzählung eine komplett hoffnungslose Konklusion. Damasio erforscht vielmehr, wie Leser der SF handlungsmächtig werden können, indem er seine Werke als Botschaftsträger konzipiert, 2 die Möglichkeiten zur Handlung in kleinem Maßstab anstoßen. Um aufzuzeigen, wie Damasios Kurzgeschichte durch die Problematisierung verschiedener Brüche Handlungsmöglichkeiten herausarbeitet, untersucht dieser Beitrag zunächst, inwiefern die Katastrophe durch ihren unbekannten Ursprung und das Verschwimmen von Grenzen zwischen Personen und Objekten mysteriös bleibt. Diese unklare Trennung von Lebewesen und Artefakten weist auf den Wunsch nach anderen Überlebenden der Apokalypse und deren identitätsverändernde Kraft hin. Lebensformen, die sich erhalten haben, findet der Protagonist in sich selbst, indem er teilweise andere Identitäten annimmt. Damasio baut auf eine populäre Auffassung der Schizophrenie als Identitätsspaltung auf, um zu zeigen, dass die pathologische Konstruktion von Identitäten eine prekäre Lösung ist. Indem der Held stetig weiter in die Illusion eintaucht, wird die Realität immer sichtbarer und bewusster. Gerade dadurch, dass er Kinder erfindet, um die er sich kümmert, macht die Kurzgeschichte die Produktivität und Vitalität der Katastrophe begreifbar. In einem solchen Kontext können postapokalyptische Fiktionen Leser zu einer aktiven Verbesserung ihres Handelns einladen (Claisse und Delvenne 165 f.). Die Postapokalypse: Historische Zäsur und sprachlicher Paradigmenwechsel Ihre Themen und die Erzählweise markieren die Kurzgeschichte »Sam va mieux« als postapokalyptische Erzählung. Diese wird manchmal als Unterkategorie des SF-Genres aufgefasst und auch als End-of-civilisation-Literatur, Endzeitliteratur, Dystopie u. Ä. bezeichnet. Im Gegensatz zur Apokalypse fokussiert die postapokalyptische Erzählung auf die Zeit nach der jeweiligen Katastrophe. Diese fungiert nicht bloß als Erzählvorwand, sondern als Motor der Handlung. Der Bruch mit Bekanntem, der im Zentrum apokalyptischer Fiktionen steht, führt in postapokalyptischen Erzählun-gen wiederum zur Reflexion über das Fortbestehen von Personen, soziokulturellen und ökonomischen Strukturen, Handlungs-und Denkweisen. Was genau zum Bruch geführt hat, kann dabei vage bleiben. Auch in »Sam va mieux« werden die Gründe des Kollapses nicht erläutert. Durch diese mysteriösen Kausalzusammenhänge wird die fantastische Dimension der Kurzgeschichte hervorgehoben. Das Ende der Zivilisation besteht also im Nicht-Enden. Dem katastrophalen Ereignis folgt eine neue Ordnung, die erzählt werden muss. Jacques Derrida schreibt in einem solchen Zusammenhang: »Die Prämisse des post-apokalyptischen Texts lautet: die eigentliche Apokalypse hat längst stattgefunden. Das Erzählen findet immer nachträglich statt« (Derrida, »No apocalypse« 173). Damasios Kurzgeschichte beginnt mit einer unheilvollen Atmosphäre. In einer zerstörten Großstadt irren zwei Figuren im strömenden Regen umher. Was zunächst wie eine zwischenmenschliche Verbindung, eine Hoffnung gebende Fraternität aussieht, erweist sich jedoch schon ab dem ersten Satz als fragwürdig: Je suis le petit salon au plafond crevé du 15, rue Gay-Lussac, avec ses trois fauteuils décloués et le tapis gorgé comme une éponge où chacun de tes pas forme empreinte.

  mieux« 265 f.) 3 Die zitierte Passage weist offensichtliche Wiederholungseffekte auf phonetischer, morphologischer und syntaktischer Ebene auf. Diese werden durch die Anapher »Je suis«, Alliterationen (zum Beispiel »petits pas de moineau mat«), Assonanzen (»rouillent et les poulies encore huilées, je suis le treillis«) und die Wiederholung der Zahl sechs mit 3 »Ich bin das kleine Wohnzimmer mit der rissigen Decke in der Gay-Lussac-Straße 15, mit seinen drei ausgemusterten Sesseln und dem Teppich, vollgesogen wie ein Schwamm, auf dem jeder deiner Schritte einen Abdruck hinterlässt. Ich bin der Regen, der auf dem Zink körnt, und du trabst wie er über die Dächer, mit kleinen, matten Spatzenschritten. Ich bin das Wasser, das an den Fensterrahmen herunterläuft, zwischen dem Putz und den Fensterrahmen, der sich windende Bach aus dem sechsten Stock, der über das Holz der Treppe kaskadiert, die ich durchnässt mit Sam auf deinem Rücken und dem Kanister in unseren Armen hinaufsteige. […] Ich bin die rostenden Kabel und die noch geölten Rollen, ich bin das Gitter, das deine Hand mit einem lauten Knall von Schrot verschiebt, und der Rufknopf, der noch leuchtet, wir sind die Aufzüge, die nach sechs Jahren ohne jegliche Wartung, ohne jegliche Anwesenheit, zu deinem Vergnügen funktionieren«. Alle Übersetzungen von der Autorin.

  und ohne Suffigierung hervorgerufen. Die rhythmische Unterteilung der Passage durch diese Wiederholungen vermittelt zum einen die Idee der Zyklizität, welche der Postapokalypse inhärent sein kann. Zum anderen wird ihr musikalisches Potenzial zum Vorschein gebracht. Dadurch entsteht ein Eindruck eines Déjà-vus. Wiederholungseffekte auf der Laut-, Wort-, Satz-und Sinnebene tragen zur literarischen Darstellung psychologischer Probleme bei. In der Tat deutet die Repetition auf ein Problem hin, auf das die Figur immer wieder zurückkommt. Obwohl die Figur mental aktiv zu sein scheint, wird das Problem nicht gelöst, weil es fast gänzlich ins Unbewusste verdrängt wurde. Im Bereich zwischen bewusst und unbewusst finden sogenannte Latenzphänomene statt: Damasio gelingt es während der gesamten Erzählung, solche durch besondere sprachliche Mittel ausdrücken. Dazu gehört das Spiel mit den Personalpronomen, das in der zitierten Passage besonders hervorsteht. Zunächst soll erklärt werden, wie die Wiederholungseffekte mit der Entstehungsgeschichte des Werks zusammenhängen. »Sam va mieux« ist als Teil einer thematischen Sammlung entstanden, die in Damasios das Bedürfnis geweckt hat, sprachliche Möglichkeiten zu erkunden: »Sam va mieux« ist eine Kurzgeschichte, die für eine Sammlung mit einem vorgegebenen Thema geschrieben wurde [...] sie handelt von Schizophrenie. Es schien mir, dass es etwas zu versuchen gab, was nicht unbedingt getan worden war, nämlich mit dem Zittern der Äußerung zu arbeiten. Dass man nicht mehr weiß, wer gerade grammatikalisch spricht. Das war eine stilistische Herausforderung, die mich sehr interessierte. (Interview, »Le Bû«) 4 Damasio interessiert sich ausdrücklich nicht für den medizinischen Aspekt der Schizophrenie, sondern für ihre poetische Ausdrucksmöglichkeiten. Er stellt die Frage »Wer spricht?« in den Kontext der Katastrophe. Die Aufmerksamkeit, die der Autor linguistischen Besonderheiten zukommen lässt, vernetzt also mehrere Problematiken und Herausforderungen der SF und insbesondere der Postapokalypse mit psychologischen Themen, genauer gesagt der Identitätsfrage. Die Kurzgeschichte erzählt von den Auswirkungen der Apokalypse auf die Identität. Laut Derrida ist die problematische Autorität -im eigentlichen Wortsinn -eng mit der Repräsentation der Katastrophe 4 »›Sam va mieux‹ est une nouvelle écrite pour un recueil avec un thème imposé […] celle-ci porte sur la schizophrénie. Il me semblait qu'il y avait quelque chose à tenter qui n'avait pas forcément été fait, qui était de travailler sur le tremblement de l'énonciation. Qu'on ne sache plus qui est en train de parler grammaticalement. C'était un défi stylistique qui m'intéressait beaucoup«. Die erwähnte Kurzgeschichtensammlung trägt den Titel Le Jardin schizologique. Nouvelles apparues dans le miroir (2010; dt. Der schizologische Garten. Im Spiegel erschienene Kurzgeschichten).

  Figuren oder sogar den Lesern manifestiert sich in Formulierungen wie »ensemble«; »je suis la bouteille et tu es le bourbon«. In der obigen Passage werden fast alle existierenden Personalpronomen benutzt. 9 Damasios Textkomposition geht von der strengen Auslegung der Sapir-Whorf-Hypothese aus, die er hinsichtlich der Innenwelt des Protagonisten weiterentwickelt: Dessen Psyche kreiert eine Welt und suggeriert einen Zustand mit dem Ziel, den Protagonisten zu schützen. Eine Art Theaterinszenierung findet statt, wobei die eigene Psyche Regie zu führen scheint. Darüber ist die Figur teilweise in Kenntnis, wie wir an lexikalischen Abweichungen von der Norm sowie deren Interpretation und Integration in die postapokalyptische Welt sehen. In der oben zitierten Textpassage vollzieht sich eine Umkehr: Während die Verben und Adjektive im ersten Teil negativ behaftet sind (›leer‹, ›rar›, ›überquellen‹, ›bet-teln›‹), werden sie durch eher positiv konnotierte Ausdrücke im zweiten Teil ersetzt (›in Wallung bringen‹, ›in Atem halten‹; hierbei ist jedoch anzumerken, dass diese in gewissen Kontexten ebenfalls als negativ empfunden werden können). Die Passage schlägt in dem Moment um, als der Protagonist sein alkoholisches Getränk in sich hineinkippt. Der Konsum von bewusstseinsverändernden Substanzen (je nach Epoche handelt es sich um Opium, Absinth oder fiktive synthetische Drogen) gehören seit dem 19. Jahrhundert zu den Topoi der französischen Fantastik. 10 Auf phonetischer Ebene situiert sich eine Wandlung an derselben Stelle im Text: Die Minimalpaar-Folgen [bɔ] oder [bɔ] (aber auch die Buchstabenfolge »bo«) kommen in jedem Satz vor, bis der Alkoholkonsum konkret stattfindet. Der kurze Satz hebt sich von den vorhergehenden komplexeren syntaktischen Konstruktionen ab, womit er ebenfalls eine Veränderung oder einen Bruch signalisiert. Mit dem Verschwinden der phonetischen Lautfolge bzw. der Buchstabenfolge verschwinden auch Bob und das Mädchen, wodurch Sam wieder in den Vordergrund tritt. Auch im folgenden Satz, mit welchem der Incipit abschließt, ist die Folge, die auf den Namen Bob verweist, nicht vertreten. Es deutet sich so ein Zusammenhang zwischen der problematischen Präsenz anderer Menschen, der Sprache und einem psychologischen Problem an. Als sich der Bewusstseinszustand des Protagonisten verändert, verändert sich seine Entourage mit; dies spiegelt sich in der Sprache wider. Die zunächst konventionell wirkende Textpassage birgt also in

  hôtel inondé ? Combien de planches ? 15 Siehe z. B. Bouju et al.; Jouve und Chonavey.

-

  Tu te souviens qui je suis ? -Pas très bien... -Je suis Sam. -Ah... Comment ça va ? (Damasio, »Sam va mieux« 166 f.) 16 Die Frage nach Sams Befinden setzt logischerweise die Existenz dreier Individuen voraus: Die des Protagonisten, seines Sohnes Sam und einer Person, die nach Sam fragt. Der Schluss des bizarren ›Dialogs‹ suggeriert aber, dass die dritte Figur und Sam sowie der Protagonist und die dritte Figur ein und dieselbe Person sind. Anstatt einen Eindruck von Abgeschlossenheit und Vollständigkeit zu vermitteln, ruft diese ›Zirkularität‹ einen Eindruck von Verschlossenheit und Eingeschlossensein hervor. Sie ist bezeichnend für die Art und Weise, wie Damasio die Schizophrenie darstellen will: »[J]e voulais expérimenter la schizophrénie comme un dédoublement je/tu intérieur entrelacé et fluide, et je trouve le résultat très beau, beaucoup plus naturel que je ne l'avais espéré« 16 »-Wie geht es Sam heute morgen? -Sam geht es besser.

  Wer zum Beispiel? -Der Regen... [...] -Wie viele von euch sind hier? -In diesem überfluteten Hotel? Wie viele Bretter? -In der ganzen Stadt? -Ich bin ganz allein. Die Schornsteine auch. -Es gibt mich aber trotzdem, oder? Zählst du mich nicht? -Ich kenne dich nicht gut, also... -Weißt du noch, wer ich bin? -Nicht sehr gut... -Ich bin Sam. -Ah... Wie geht es dir?«. Man denke auch an den Roman Le dernier monde (2007; dt. Die letzte Welt) von Céline Minard, in dem der Erzähler und Überlebende einer Katastrophe Jaume sagt: »Je dois me doubler. S'il faut me tripler, je me triplerai« (»Ich muss mich verdoppeln. Wenn es notwendig ist, mich zu verdreifachen, dann verdreifache ich mich« (113).

(

  Tannhauser), 17 wobei »natürlich« hier nicht realitätsgetreu, sondern überzeugend und kohärent bedeutet. Damasios Werk will nicht mit medizinischer Forschung wetteifern, sondern eine fiktive Welt erschaffen, in der mentale Prozesse die Leser zum Nachdenken anregen. Die hohe Anzahl an Fragezeichen und Auslassungspunkten, die Kürze der Repliken sowie das Beantworten einer Frage mit einer Gegenfrage vermittelt den psychischen Zustand des Protagonisten, der geplagt ist von der Einsamkeit und der Ausweglosigkeit seiner Situation. Nun gilt es zu zeigen, dass die verdrängte Wahrheit schon teilweise in der abweichenden Sprache präsent ist. Nicht nur die Grenzen zwischen den Individuen verwischen, auch Mensch und Materie (»gens«/»pluie«, »moi«/»cheminées«) verschmelzen. Es scheint sogar mehr als nur drei Gesprächspartner zu geben, mit denen potenziell ein vielseitiger Austausch stattfinden kann. Der Protagonist fügt sich in ein selbstgebautes (Sicherheits-)Netz ein, das ihm durch die schwere Zeit hilft. Die Tatsache, dass er vorgibt, genauso alt zu sein wie Sam (drei Jahre), deutet an, dass der Held einen symbolischen Tod gestorben ist, als die Katastrophe eintrat. Dank Sam konnte er in einer neuen Form wiederauferstehen. Es ist also von großer Bedeutung für den Protagonisten, dass es Sam möglichst gut geht. »Besser« impliziert, dass es Sam zuvor schlecht ging, doch die genauen Umstände seiner Genesung bleiben vage. Daher drängt sich die Frage auf, ob es nicht eher dem Protagonisten besser geht, weil Sam da ist und mit ihm spricht. Während der Beginn des Austauschs noch banal erscheint und an eine Alltagssituation erinnert, in der sich zwei Elternteile treffen und über Kinder sprechen, vollzieht sich rasch eine Wandlung zur postapokalyptischen Atmosphäre. Der Text gibt zu verstehen, dass schon Austausche stattgefunden haben können (denn sonst würde sich die dritte Figur nicht nach Sams Befinden erkundigen). Zwischen den Zeilen bricht Ungesagtes hervor, so als ob die Wirklichkeit einen Riss bekäme. Daher entsteht der Eindruck, dass eine unterschwellige Kraft an die Oberfläche des Bewusstseins gelangen möchte und dies ihr aber nur teilweise gelingt. Im Dialog stehen miteinander unvereinbare Aussagen in einem Spannungsfeld gegenüber; Fragen, die potenziell die angsteinflößende Wahrheit ans Licht bringen könnten, werden mehrmals gestellt und ziehen so die Aufmerksamkeit der Leser auf sich. Sam will für den Protagonisten gehalten werden, ihm wichtig sein und nicht ersetzt werden. Sam macht sich so teilweise unabhängig von seinem Vater/ Erschaffer; der Intertext von Mary Shelleys Frankenstein (1818) 18 erscheint so bei Damasio auf neuartige Weise. Es soll daher erkundet werden, wie Sam sich von sprachlichen Normen freimacht und Worte sowie die Vater-Kind-Beziehung in ihr Gegenteil verkehrt. 17 »[I]ch wollte die Schizophrenie als eine verflochtene und fließende innere Ich-Du-Verdopplung erleben, und ich finde das Ergebnis sehr schön, viel natürlicher, als ich es mir erhofft hatte«. 18 Auch Mary Shelley hat sich der Problematik des letzten Überlebenden in ihrem Roman The Last Man (1826) gewidmet. Das Wortspiel »mieux«/»vieux« signalisiert auf den ersten Blick ein akustisches Verständnisproblem, das angesichts der Tatsache, dass der Protagonist nur mit sich selbst spricht, absurd erscheint. Entscheidend zum Verständnis ist hier die Art, wie die Beziehung zwischen Sam und seinem Vater aufgebaut wird. Der Protagonist etabliert eine Verbindung über die Spracherziehung von Sam: -Tu es prêt ? C'est parti ! Crache, ma grosse, crache ta crasse ! -Tu es pêt ? C'est pâti ! Cache, ma gosse, cache ta casse ! -Pas de farces, hein ? -Pas de faces, hein ? -Applique-toi ! Répète après moi : le braquet... -Le baquet... -La trombe nous brise... -La tombe nous bise... -Ça marche pas ! -Ça mâche pas ! (Damasio, »Sam va mieux« 279) 19 Der Held spielt während diesen improvisierten Logopädiestunden die Rolle der Lehrperson, was ihm Bedeutung und Autorität verleiht. Er hat somit eine wichtige Funktion für Sam. Seine Aufgabe fördert das Zwischenmenschliche, das die Apokalypse vernichtet hat: Das von einer Generation an die nächste weitergegebene Wissen bildet die soziale Grundlage der Menschheit (Chonavey 55). Einerseits handelt es sich also um eine Beschäftigung, die dem Protagonisten guttut, die er selbst implementiert hat und der er regelmäßig nachgeht. Andererseits entsteht durch die fehlerhafte Wiederholung durch Sam ein neuer Wortsinn. Diese Vorgehensweise erinnert an die berühmte Szene der Nymphe Echo in Ovids Metamorphosen, in der Echo Narziss' Worten durch geringe Veränderungen eine völlig neue Bedeutung verleiht. Bei Damasio bezieht sich der neue Wortsinn auf den psychischen Zustand des Protagonisten, der sich an ein erfundenes Lebewesen klammert.

  19 »-Bist du bereit? Jetzt geht's los! Spucks aus, Riesending, spuck den Dreck aus! -Bis du beeit? Jets ists vobei! Vesteck, mein Kind, vesteck das Kaputte! -Mach keinen Unsinn, in Ordnung ? -Keine Gesichta, in Odnung? -Bemüh dich! Sprich mir nach: Das Umwandlungsverhältnis... -Eima... -Die Trombe zerbricht uns... -Das Grab küsst uns... -Es funktioniert nicht! -Es kaut nich!«. Die Wortspiele verraten etwas über die Identität Sams, der nichts anderes als ein Samowar ist. Sam kann das Phonem [ʀ] nicht aussprechen, hat aber kein Problem mit Zischlauten. Der entweichende Wasserdampf eines Samowars gibt eben solche Zischlaute von sich. Sams Sprechweise ist also ein Indiz dafür, dass er nur ein Objekt ist, aber sie erinnert auch an häufig vorkommende Ausspracheschwierigkeiten bei Kindern. So wird »crache« zu »cache«: Etwas ausspucken, das auch als Metapher verstanden werden kann (»mit der Wahrheit herausrücken«) wird zu »verstecken«. Wie Echo verkehrt Sam die Aussage in ihr Gegenteil und schickt die Nachricht (im linguistischen Sinn) als »Anderes« zum Sender zurück. Im Folgenden wird »farce« zu »face«, »kein Unsinn« zu »keine Gesichter«: Diskret gibt Sam zu verstehen, dass es keine weiteren Überlebenden der Katastrophe gibt. Schließlich verwandelt Sam »trombe« in »tombe«, d. h. in das Grab. Die Versuche zur Spracherziehung können die Realität der Situation nicht überwinden: Diese wird durch die »falsch« ausgesprochenen Worte sichtbar. Die Wortspiele, Zungenbrecher usw. sind Anzeichen für die Art und Weise, auf die der Protagonist seine »Spracherschaffungsmaschine« -ein von Damasio benutzter Begriff (Nicolas und Oreste) -konstruiert hat. Die lebenserhaltende Lüge des Helden gibt ihm die Kraft, weiterzumachen und sich sogar der Realität zu stellen. Als er eines Tages glaubt, dass irgendwo in der Stadt doch noch jemand überlebt hat, will er dieser Vermutung zunächst nicht nachgehen. Erst Sam ermutigt ihn dazu: La mélopée flottait dans l'air, comme un fado, comme un parfum. J'étais dans une rue sèche, la toute première de la journée. Aucune parole parasite, issue de l'eau bavarde, ne me gênait plus. »Ça vient de là-haut, derrière le bloc«, j'ai dit à Sam. Tout son corps a éclaté de joie. -On y va, papa ? On y va ? -Il va faire nuit Sam. Faudrait plutôt se trouver une chambre et du bois-qui-brûlebien, tu crois pas ? Ça va faire froid, cette nuit… -On y va !!!! (Damasio, »Sam va mieux« 282) 20 20 » Die Melodie schwebte in der Luft, wie ein Fado, wie ein Parfüm. Ich befand mich auf einer trockenen Straße, der allerersten des Tages. Kein parasitäres Wort aus dem geschwätzigen Wasser störte mich mehr. ›Das kommt von da oben, hinter dem Block‹, sagte ich zu Sam. Sein ganzer Körper platzte vor Freude. -Sollen wir hingehen, Papa? Sollen wir hingehen? -Es wird bald dunkel, Sam. Wir sollten uns lieber ein Zimmer suchen und ein bisschen Holz, das gut brennt, meinst du nicht? Es wird kalt werden heute Nacht... -Wir gehen hin!!!!«. Sam motiviert den Protagonisten zur Begegnung mit den angeblichen Überlebenden. Der Held lehnt dies zuerst ab und verstrickt sich dabei in Widersprüche, weil er instinktiv vermeiden will, sich an seine Lüge zu erinnern. Eine aufgedeckte Lüge bedeutet aber nicht unbedingt deren Ende: Der Protagonist hat bereits mehrmals vergessen, dass er sich ›Kinder‹ gebastelt hat. Er lebt in einem Kreislauf des Vergessens und sich wieder Erinnerns: -C'est quoi ça, papa ? souffle Sam. -Quoi quoi ? -Là ! Tu ne les avais même pas vus, obnubilé par les cônes. Ils sont pourtant à hauteur d'homme.

  21 »-Was ist das, Papa?, haucht Sam.-Was ist was? -Da! Du hast sie nicht einmal gesehen, weil du so auf die Kegel fixiert warst. Dabei sind sie mannshoch.-Sind das meine kleinen Brüder, Papa? Ich nähere mich den Nischen, die in die Wände eingelassen sind. Es sind insgesamt acht. Und drei sind besetzt. In der ersten befindet sich ein Holzzylinder, der mit Röhren und Löchern bearbeitet ist. Das Werk eines sanften Verrückten.-Erinnerst du dich daran? -Nein, Sam. -Das war Jim. Er redete mit dir mit Wind, er war nicht brav. Du hast ein Jahr mit ihm verbracht. Der zweite ist eine kleine Windharfe. Auf ihrem Rahmen steht »Line«. Ich halte meine Fackel in Richtung der dritten Nische... Ein sehr voller Didgeridoo-Ton dringt in den Raum, ich bekomme eine Gänsehaut, ich zittere heftig, von Kopf bis Fuß, die Fackel zittert, ich lasse sie los und strecke meine Hände nach dem Melchior-Samowar aus, der in der Nische steht und auf dem drei Buchstaben eingraviert sind: TOM«. Der Schutz vor der Realität und die Enthüllung der Wahrheit stehen sich nicht unvereinbar gegenüber. Sam funktioniert sowohl als selbstgebauter psychologischer Schutzmechanismus als auch als Motor der Erkenntnis für den Protagonisten. Deshalb kann man sagen, dass die Thematik des Bruchs, welche die Kurzgeschichte charakterisiert, einerseits die Bedeutung von »Aufbruch, Öffnung«, andererseits die des Neuanfangs entfaltet. Sam die richtige Aussprache zu lehren lässt den Helden in seiner Illusion versinken und erlaubt es ihm auch an anderer Stelle, aus ebendieser Illusion auszubrechen. Sams Spracherziehung eröffnet einen neuen Raum in der zerstörten Welt, wo empowerment entstehen kann. So heißt es am Ende der Kurzgeschichte: »Debout. Ce qui te manque ne reviendra jamais. Ne le cherche plus : crée-le«. 22 Fazit Indem die Kurzgeschichte das Ende als einen Moment des Bruchs erzählt, der eine absolute Trennung zwischen der alten und der neuen Welt schafft, thematisiert Damasios Erzählung die innere Spaltung des Protagonisten. Damasio bezieht die Sprache auf die psychische Verfassung der Hauptfigur. Sam und alle anderen imaginären Kinder des Protagonisten üben Funktionen aus, die für postapokalyptische Fiktion insgesamt zentral sind: Eine kathartische Funktion (Trost spenden), eine kritische und pädagogische Funktion (Desillusionierung und Warnung) sowie eine befähigende und emanzipatorische Funktion (Aufrechterhaltung von Handlungsmächtigkeit). »Dystopias matter because they make us think. They help us to imagine and envisage how the present can change into something very nasty. They tell us what's wrong with the now, and they imagine how things could (easily) become much worse« (40). Erzählungen wie Damasios Kurzgeschichte haben die Fähigkeit, eine Neuorientierung des persönlichen Verhaltens bei den Lesern einzuleiten. Indem sie einen dunklen Teil der Gesellschaft sichtbar machen, erinnern sie daran, dass Bindungen überlebenswichtig sind. »Sam va mieux« geht der Frage nach, wie sich Handlungsmacht trotz der Katastrophe entfaltet und welche Wirkungen dadurch möglicherweise erzeugt werden können. Eine Möglichkeit besteht im Willen, auf kreative Weise mit einer sich verändernden Welt umzugehen. Der Mensch hat das Potenzial und die Pflicht, die Welt nicht passiv zu erleiden. So kann Empowerment entstehen: Postapokalyptische Fiktionen »depict dark, frightening, sometimes apocalyptic futures (the end of civilization, the death of humankind, the destruction of the earth) while shedding light on a grey zone -where we find ourselves right now -from where we may change our future« (Claisse und Delvenne 157). Durch die Fokussierung auf die Zeit danach wird klar, dass die Überlebenden sich anpassen und neue Ressourcen finden müssen. Die posthumanistische Sichtweise auf die Geschehnisse vermittelt, dass die Menschheit ihre Zukunft nicht mehr als unabhängig von Tieren, Pflanzen und sogar Artefakten betrachten kann. Das Anthropozän zwingt sie, die Wechselbeziehungen aller Arten untereinander und mit ihren Umgebungen zu denken (Engélibert 191). Wenn alte Lösungsrepertoires nicht mehr funktionieren, zwingen die neuen Bedingungen sie dazu, kreativ zu werden, um zu überleben. Die Fiktion zeigt die Notwendigkeit auf, diese Strategien bereits jetzt, vor der Katastrophe, anzuwenden. Der Überlebenswille in einer menschenfeindlich gewordenen Welt hat nur einen Sinn, wenn die politische, aktive Komponente der SF nicht nur von engagierten Schriftstellern wie Damasio, sondern auch von der Literaturtheorie als Potenzial anerkannt wird (Leconte und Passard 11).

»J'écris pour porter des valeurs et des messages« (»Ich schreibe, um Werte und Botschaften zu vermitteln«, Hrod.

Deren Herausforderungen für Übersetzungen wird sich die nächste Ausgabe von ReS Futurae widmen; ReS Futurae 24, »Science Fiction et traduction«, 2024.

»Être vivant […] c'est se confronter à ce qui n'est pas soi, être traversé par l'altérité«; »aucune vie ne peut s'épanouir en vase clos«.

Vgl. Calvino 6; Castex.

»Steh auf. Das, was dir fehlt, wird nie wiederkommen. Suche es nicht mehr: Erschaffe es«.