Results of the TOSQAN Spray Benchmark - IRSN

1/12 Session n°4 , Paper n°6

Modelling of Sprays in Containment Applications: Results of the TOSQAN Spray Benchmark (Test 101) J. Malet1, P. Lemaitre1, E. Porcheron1, J. Vendel1, A. Bentaib1, W. Plumecocq1, F. Dumay2, Y.-C. Chin3, M. Krause3, L. Blumenfled4, F. Dabbene4, P. Royl5, J. Travis5 1) IRSN, BP 68 - 91192 Gif-sur-Yvette 4) CEA/DEN/DM2S/SFME/LTMF, CEA cedex, France Saclay, 91191 Gif-sur-Yvette cedex, 2) AUSY, 10, rue des Acacias, BP 94, 92134 France Issy-les-Moulineaux cedex, France 5) FZK, Postfach 3640, D-76021 Karlsruhe, 3) AECL, Chalk River, Ontario, K0J 1J0, Germany Canada SARNET: FI6O-CT-2004-509065 SUMMARY The TOSQAN project has been created to perform separate-effect tests that are representative of typical post-accident thermal-hydraulic flow conditions in the reactor containment (wall condensation spray, sump, aerosol). The TOSQAN facility has a high density of instrumentation (gas temperature, steam concentration, droplet velocity and diameter). The main thermal-hydraulic phenomena when water sprays are used in containment are the mixing induced by spray entrainment and the heat and mass transfer on droplets and walls. In order to study the latter phenomena, a benchmark has been initiated, based on the TOSQAN Test 101. In this test, a cold-water spray is injected into the steamair-filled vessel, resulting in partial depressurization. The first phase (2003-2004) was blind and the second (2005) open. The codes involved are either 0D-codes or Multi-Dimensional codes. It is shown that the calculated total pressure is very sensitive to the modelling, depending on how the vaporization of droplets in the gas or on the structures is taken into account. Local results show that the spray injection should be carefully modeled and that experimental data are necessary. This benchmark on Test 101 continues in the frame of SARNET with a third phase for post-calculations including the new experimental data on the spray injection. A second TOSQAN spray benchmark is also proposed (Test 113) and concerns gas dispersion by sprays of an air-helium stratified mixture. A. INTRODUCTION

During the course of a hypothetical severe accident in a Pressurized Water Reactor (PWR), hydrogen can be produced by the reactor core oxidation and distributed into the containment according to convection flows. In order to prevent overpressures in steam break event, spray systems are used in the containment. However, the effect of spray could even increase the hydrogen risk by condensing steam and locally enriches gaseous mixtures with hydrogen. The TOSQAN (TOnus Qualification ANalytique) project has been created to simulate separateeffect tests representative of typical accidental thermal-hydraulic flow conditions in the reactor containment (wall condensation [1], spray, sump, aerosol). The idea of the TOSQAN spray program is to perform an intermediate study between separate-effect tests and integral tests, considering one phenomenon (gas-spray interaction), with a high density of instrumentation. The present work concerns the interaction of an internal water spray used at the top of the containment in order to reduce the steam partial pressure, under air-steam mixtures conditions. The main phenomena occurring when water spray is used are the mixing induced by spray entrainment and the heat and mass transfer on droplets and walls. In order to study the latter phenomena, different codes are used in the frame of two benchmarks (blind and open). The objective of this paper is to present the main results of this benchmark. The first European Review Meeting on Severe Accident Research (ERSMAR-2005) Aix-en-Provence, France, November 14-16, 2005


B. BENCHMARK HISTORY This benchmark has been originally initiated in March 2003 by FZK and IRSN in order to perform together a spray calculation under typical conditions of a hypothetical nuclear reactor accident, using GASFLOW and TONUS-CFD. The test chosen for this exercise was taken from the TOSQAN test matrix [2]: test 101. GOTHIC code used by AECL has joined the benchmark in June 2003. Lumped-parameter (LP) codes have been used at the IRSN for pretest calculations of the TOSQAN spray tests matrix (CPA/ASTEC, TONUS-LP, ACACIA) and have thus joined the benchmark in April 2004. The first meeting was held in June 2004 where all blind calculations were discussed. Experiments have been performed between June 2004 and April 2005 (repeated several times). New initial and boundary conditions based on the 1st meeting discussions and on the experimental results have been defined. During the second meeting in April 2005, results of the new ‘open’ calculations have been presented. C. TOSQAN EXPERIMENT The TOSQAN experiment (Figure 1) is a closed cylindrical vessel (7 m3, i.d. 1.5 m, total height of 4.8 m) into which steam or non-condensable gases can be injected through a vertical pipe located on the vessel axis. The spray is injected on the vessel axis, 70 cm from the top of the facility. Over 150 thermocouples are located in the vessel (in the main flow and near the walls). 54 sampling points for mass spectrometry are used for steam volume fraction measurements [3]. Optical accesses are provided by 14 overpressure resistant viewing windows permitting non-intrusive optical measurements along an enclosure diameter at 4 different levels (LDV and PIV for the gas velocities, Raman spectrometry for steam volume fractions [4]). Measurements are mainly located at the different positions presented in Figure 1. The TOSQAN vessel has thermostatically controlled walls so that the wall temperatures can be kept constant. Vol = 7.0 Volume = 7mm33

Oil in (T2)

1.5 m window

Dj = 0.41 m

Steam Injection Injection height Height 2.1 m 2.1 m

Air Steam helium Sump 0.87 m

Z16=4.8m Z15

Oil out

Condensation Zone : 2 m 9.4 m2

Upper wall

Spray injection line

Spray Injection Line

Oil in the wall (T1)

Condensed water

0.68 m

Oil in the wall (T2)

Main Vessel 3.93 m

Z14 Z12

Z13 Middle wall (2 m height)

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Z10 Z8 Steam injection line

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Z7 Z5

Z4 Z2

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Z0=0m Rows of 6 thermocouples Sampling lines for mass Spectrometry (6 points on a ½ radius) Window for laser measurements : LDV, Raman Spectrometry, Rainbow Refractometry (upper part only)

Figure 1: schematic view of the TOSQAN facility and positions of the measurements.

Spray tests presented here consist of a water spray injection into the enclosure, which is initially filled with an air-steam or an air-steam-helium mixture, the walls having already

The first European Review Meeting on Severe Accident Research (ERSMAR-2005) Aix-en-Provence, France, November 14-16, 2005


reached their nominal temperature. A vessel depressurization is observed and a final equilibrium is reached. Measurements are performed during the depressurization and during this final equilibrium. The TOSQAN spray test matrix is presented on Table 1. Test 101 is the reference test with air-steam mixture (A-S), whereas test 102 is the reference test with air-steam-helium mixture (A-S-H). The other tests are performed by changing the spray injection mass-flow rate Qinj (#103 and #104), the spray injection temperature (#107), the superheating (Tg-Tsat) (#105 and #106), the initial gas temperature Tg (#108), the difference between saturation temperature and injection temperature (Tsat-Tinj), (#107 and #108), the gas composition (#109 and #110, Xs for steam volume fraction, Xh for helium volume fraction and RH for relative humidity), and the droplet diameter D (#111 and #112). As a result, they have different final pressures P, temperatures and gas compositions. The design of these tests has been performed in the frame of a European Concerted Action SCACEX [5] and details on this spray test matrix can be found in [2] and [6] (calculations of the test matrix with ACACIA and TONUS-LP).

Mixture Ref.101 Ref. 102 103 104 105 106 107 108 109 110 111 112

A-S A-S-H A-S A-S A-S A-S A-S A-S A-S-H A-S-H A-S A-S

Initial gas mixture characteristics Tg P Xs RH Xh Tsat (°C) (°C) (bar) (%) 120 2.5 0.6 75 0 112.6 120 2.5 0.4 50 0.2 100.7 120 2.5 0.6 75 0 112.6 120 2.5 0.6 75 0 112.6 120 2.5 0.3 34 0 91.5 120 3 0.65 98 0 119.6 120 2.5 0.6 75 0 112.6 140 5 0.6 83 0 132.7 120 2.5 0.5 63 0.1 107.4 120 2.5 0.3 38 0.3 91.6 120 2.5 0.6 75 0 112.6 120 2.5 0.6 75 0 112.6

Tg-Tsat (°C) 7.4 19.3 7.4 7.4 28.4 0.4 7.4 7.3 12.6 28.4 7.4 7.4

Qinj (g/s) 30 30 10 70 30 30 30 30 30 30 30 30

Spray characteristics Tinj Tsat–Tinj (°C) (°C) 92.6 20 80.7 20 92.6 20 92.6 20 71.5 20 99.6 20 52.6 60 112.7 20 87.4 20 71.6 20 92.6 20 92.6 20

D (µm) 200 200 200 200 200 200 200 200 200 200 350 500

Table 1: nominal spray tests matrix in TOSQAN.

The test proposed for this benchmark is the so-called reference spray test 101 and its initial and boundary conditions are described hereafter. Ø The day before the test, the open vessel is heated up to 120 °C; Ø Steam injection is performed in the closed vessel containing one bar dry air at 120 °C, until total pressure of 2.5 bar is reached; Ø After reaching a total pressure of 2.5 bar, steam injection is stopped; the so-called initial conditions of the spray phase are reached (see Table 2); Ø Wall temperatures are controlled during the whole sequence; however, as soon as the spray touches the lower wall, some variations of the wall temperatures are observed (Table 3); Ø Water spray injection is started (t = 0 s) at a constant flow-rate and a constant injection temperature, except the first 1000 s (Table 4); Ø The water in the sump of the vessel is removed as fast as spray droplets arrive; Ø The test is stopped when the pressure reaches a quite constant level (final equilibrium).



Mean gas temperature out of the spray zone Mean gas temperature in the spray zone Total pressure Initial gas composition (from mass balance)

131.1 °C 131.0 °C 2.5 bar 213 moles of air + 308 moles of steam, (59.1%vol steam)

Table 2: experimental gas initial conditions just before spray injection (t = 0 s).

Mean wall temperature Just before spray injection 122.1 0-102 s 121.5 107 s- 300 s 120.4 306 s – 601 s 119.9 End of the test 118.9

Upper wall 121.8 121.4 120.8 120.3 119.3

Middle wall Lower wall 122.3 121.7 121.6 121.3 120.4 120.3 119.4 120.0 120.1 115.4

Table 3: measured mean wall temperatures (in °C). Spray flow-rate Spray angle Spray injection height Initial droplet initial size Initial droplet velocity Droplet injection temperature (°C) At t=0 s At t=311 s At t=1000 s

29.96 g/s 55 °C 0.65 m from the top on TOSQAN axis (r=0) 130 µm 20 m/s Mean value integrated over 5s at the given time – linear interpolation between two steps 119.1 °C 22.1 °C 27.7 °C

Table 4: experimental spray characteristics.

The values of the initial droplet size and velocity chosen at the nozzle exit (Table 4) are difficult to estimate. Measurements have been performed below the nozzle exit: Ø The droplet size distribution measured at 1.35 m from the injection (by Interferometrics Laser Imaging for Droplet Sizing [7]), shows an arithmetic mean diameter of 145 µm and a mode between 90 µm and 110 µm (see Figure 2); Ø The droplet initial velocity at the nozzle exit can be estimated between 38 m/s and 3 m/s (divergent inside the nozzle of 1 mm inlet internal diameter and 3.5 mm outlet diameter); furthermore, measurements (Particle Image Velocimetry) have been performed 50 mm from the nozzle exit and show a droplet velocity about 10 m/s (Figure 11); the velocity at the nozzle exit should be higher than this value (deceleration of the droplets), and lower than 38 m/s; a velocity around 20 m/s seems thus to be a good approximation. It has to be emphasized that all of these experimental boundary conditions were not known, even at the time of the second phase of the benchmark (especially the injection velocity). Boundary conditions used by each code will thus be specified in the next sections.



50 45

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Figure 2: droplet size distribution measured during final equilibrium at 1.35 m from the nozzle, on the TOSQAN axis.

D. NUMERICAL CODES

The different codes used here are briefly presented in this section, and a specific topic concerning the injection conditions of the multi-dimensional codes is also summarized here. GASFLOW (FZK)

GASFLOW-II is a finite-volume computer code that solves the time-dependent compressible Navier-Stokes equations with multiple gas species. Spray modelling assumes a mechanical equilibrium between gas and drops (same velocity for both phases). Concerning the thermal part, a specific internal energy equation for the droplet is added, and the gas temperature is computed by subtracting the droplet energy from the total energy equation and inverting this relationship for the gas temperature; the specific internal energy equation is also inverted to get the droplet temperature. The mass transfer is modelled to represent the droplet evaporation in the gas and condensation of steam on droplets. A droplet “sink” term is added in a so-called “droplet depletion model”: it is either a parametric model (bulk rainout) or a mechanistic model (droplets impacting the walls); the first one is used here to “simulate” droplet evaporation on the walls. GOTHIC (AECL)

GOTHIC (Generation Of Thermal Hydraulic Information for Containments) is a generalpurpose thermal-hydraulics computer program. It can be used for design, safety and licensing, and operating analysis of nuclear containments and other confinements. The version used for this analysis is GOTHIC version 6.1bp2. Model response is determined by solving a combination of mass, momentum and energy conservation equations for three phases: vapour, liquid and droplets, and by solving closure relations for interface mass, energy and momentum transfer. Each phase may have different velocities and temperatures. TONUS-CFD (CEA)

The multi-dimensional code TONUS-CFD uses an unstructured finite-element approach to model multi-component flow for weakly compressible flows (low Mach Number asymptotic model). The gas and the droplet phases are modelled with separate flow-field. An equation describes the droplet diameter variation. The gas and the dispersed phase interact each other and exchange momentum, thermal energy and mass. The interaction terms have been derived from the correlations for an isolated spherical sphere moving in a gas at rest. The mass interactions have been derived assuming an analogy between thermal energy and mass The first European Review Meeting on Severe Accident Research (ERSMAR-2005) Aix-en-Provence, France, November 14-16, 2005


transfer between gas and droplets. The relation on the mass transfer is based on the water steam at saturation. ACACIA (IRSN)

The ACACIA is a basic program for the calculations of droplets characteristics in an airsteam-helium mixture. In this code, the vessel is not modelled, i.e. a unique compartment is considered. Gas thermodynamic conditions are fixed.ACACIA computes only the droplets characteristics. The spray is modelled as a single droplet falling under gravity and drag forces. Equations solved are the motion equation for the droplet, including gravity and drag forces, heat and mass transfer at the droplet interface, heat transfer to the droplet. The input gas characteristics of the ACACIA results can be taken from the TONUS-LP or from the ASTEC/CPA. Since results of ACACIA were similar to the one of ASTEC/CPA if the latter was used as an input (because of similar modelling), ACACIA code was only participating the first phase of the benchmark. ASTEC/CPA (IRSN)

ASTEC is a complex system of codes for reactor safety assessment. In this exercise, only the CPA (Containment Part of ASTEC) Module is used. It is used with the following main elements: zones (compartments), junctions (liquids and atmospherics), and structures. The zones are connected by junctions and contain steam, water and non-condensable gases. They exchange heat with structures by different heat transfer regimes: convection, radiation and condensation. The spray is modelled by taking into account the following phenomena: droplet size distribution, relaxation of droplets, coagulation of droplets, interaction between spray and gas, interaction between spray and walls, interaction between spray and fission products. The evolution of the thermal-hydraulic conditions in a zone is obtained from a mass and energy balance, from the droplet behavior results and the evolution of the droplet-distribution function between the top and the bottom of the zone. TONUS-LP (IRSN-CEA) In the multi-compartment code TONUS-LP, a single compartment has been used for the TOSQAN spray benchmark calculation. The non-condensable gases are supposed to follow the perfect gas law hypothesis and the steam is modeled as a real gas. The solved equations are the following: mass balance of all species, water mass balance in the sump of the compartment, energy balance in the compartment, energy balance for the sump, energy balance for the structures. No evaporation of the droplet or convection effect due to the spray is modeled, and gas and sump mixture properties are the calculated variables in the standard version. In order to take into account droplet evaporation due to droplet/wall interactions, the spray flow-rate is lowered by a fraction of the real one's. The missing spray water is then considered as a steam source. This fraction is a user parameter. A modelling of droplet evaporation due to droplet/gas interaction is also considered in order to deals with the hot thermodynamic conditions. CFD-CODES INJECTION CHARACTERISTICS The specifications of the injection characteristics of the multi-dimensional codes are given in Table 5.



GASFLOW 2.05 cm injection width number of cells on 1 the injection 0.75 cm/s radially to the droplet walls, 1.5 cm/s axially velocity downward

GOTHIC 10 cm radius 3 (varying size)

TONUS CFD 5 cm diameter 4

0 m/s

0.93 m/s downward

gas velocity

0 m/s

0 m/s

0 m/s

droplet temperature droplet size water mass-flow rate droplet volume fraction nozzle injection tube

20°C

20°C

30°C

200 µm 200 µm 10 g/s radially and 20 g/s 30 g/s axially downward 100% 100%

axially

200 µm 25 g/s 2%

Not considered, injection Not considered, tube represented by fluid injection tube replaced mesh by fluid zone 25 cm first vertical cell 5 cm below injection

Not considered, injection tube replaced by fluid zone 1.3 cm

Table 5: specifications of the spray injection conditions of the CFD-codes.

E. CODE-EXPERIMENT COMPARISON AND DISCUSSION E. 1 THERMODYNAMICAL GLOBAL BEHAVIOUR The thermodynamical global behaviour concerns the pressure variation in the TOSQAN vessel. Results for the total pressure at the final equilibrium are presented on Figure 3 and Table 6. In this table, results are given for the different modellings made by the code participants. The first line (Modelling 1, M1) corresponds to calculations of the first phase of the benchmark, i.e. without any droplet-wall interaction: in the experimental case, droplets touch the bottom walls of TOSQAN and can evaporate. The second line of this table (Modelling 2, M2) concerns the calculations of the second phase of the benchmark performed taking into account droplet evaporation on walls. Each code chooses a different way to take into account this phenomenon and these ways will be discussed hereafter. However, it can be seen from Table 6 that the droplet-wall interaction is of major importance and seems to explain the lower pressures observed in the calculations performed without account this phenomena. The relative difference between both modellings lies between 20 and 46 % on the calculated pressure (last line of Table 6). TOSQAN CPA/ASTEC GASFLOW GOTHIC Modelling 1 Modelling 2 (M2-M1)/M2

2.152

1.20 2.04 41.2

1.56 2.05 23.9

1.36 1.89 2.29 28.0 40.6

TONUSCFD 1.36 -

TONUSLP 1.06 1.95 45.6

Table 6: total pressure (bar) and associated relative difference (%) calculated by the different codes and obtained experimentally at final equilibrium. The first European Review Meeting on Severe Accident Research (ERSMAR-2005) Aix-en-Provence, France, November 14-16, 2005


The time evolutions of the total pressures (codes and experiment) are presented on Figure 3. The following points have to be considered: • CPA: modelling 2 is performed assuming that one part (around 10 %) of the droplets is removed; this modelling allows to reach the experimental pressure; • GASFLOW: a droplet depletion model is used in order to get the experimental pressure level; droplet depletion model including one part of the steam coming from the droplet that are vaporized is reinjected to the gaseous mixture, and another part is removed in order to take into account the interaction between the walls and the droplets; • GOTHIC: modelling 2 is performed by multiplying the wall convective heat transfer HTC by a factor between 3.5 (left column in Table 6) and 10 (right column in Table 6): this parameter has a significant effect and the resulting pressure is enhanced; if 35 W.m-2.K-1 is taken for HTC (instead of 6), the final pressure is equal to the experimental one; the justification for this value is that the gas velocity is enhanced close to the walls and the flow is not anymore ‘free’ but a ‘forced flow’; • TONUS-LP: the standard version of this code does not take into account droplets vaporization and the modelling leads to condensation of the steam on the droplets until the spray temperature and the boiling one's are equal; in the modelling 2, the injected spray flow-rate is lowered by a fraction of the real one's (10% hereafter) and droplet spray evaporation is also modeled. • TONUS-CFD: it does not take into account the droplet-wall interaction and it can be seen on Table 6 that the pressure level reached at the final equilibrium is the same as the one obtained by GOTHIC if the same assumption is made. TOSQAN Spray Benchmark - TEST 101 3,0

Pressure (bar)

2,5

2,0

1,5

TOSQAN GASFLOW (2D) - With droplet-wall interaction TONUS-CFD (2D) - No droplet-wall interaction TONUS (0D) - No droplet vaporisation TONUS-LP - With droplet-wall interaction CPA/ASTEC (LP) - With droplet-wall interaction GOTHIC-HTC*3.5 (2D) GOTHIC-HTC*10 (2D)

1,0

0,5

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4500

5000

time (s)

Figure 3: time evolution of the total pressure.

E. 2 LOCAL BEHAVIOUR Numerous data have been obtained from the calculations on local variables (gas temperature, concentrations, velocities, droplet temperature, sizes and velocities). We will present here mainly the curves for which experimental data have been obtained: gas temperature, steam concentration, droplet velocities and droplet sizes. All the data available for code-to-code comparison are given in Table 7.



Variable

Location, time Codification (X: participant name) Measurements *** Time evolutions Gas temperature T_gas_z14_R12_X.dat x Gas velocities U_gas_z14_R12_X.dat Z14*, R12 Steam volume fraction SVF_gas_z14_R12_X.dat x Droplet temperature T_d_z14_R12_X.dat Droplet velocities U_d_z14_R12_X.dat x Droplet diameters D_d_z14_R12_X.dat Gas temperature Z11, R12 T_gas_Z11_R12_X.dat x Gas velocities U_gas_z11_R12_X.dat Z6, R12 Gas temperature T_gas_Z6_R12_X.dat x Steam volume fraction SVF_gas_Z6_R12_X.dat x Radial profiles Gas temperature (°C) T_gas_z14_R_ti_X.dat x Z14* Gas velocities (m/s) U_gas_z14_R_ti _X.dat Steam volume fraction (%) t=600s, t=tfin SVF_gas_z14_R_ti _X.dat x Droplet temperature (°C) T_d_z14_R_ti_X.dat Droplet velocities (m/s) U_d_z14_R_ti_X.dat x Droplet diameters (µm) ** D_d_z14_R_ti_X.dat Gas temperature Z11 T_gas_Z11_R_ti_X.dat x t=600s, t=tfin Gas velocities U_gas_Z11_R_ti _X.dat Gas temperature T_gas_Z6_R_ti_X.dat Z6 x t=600s, t=tfin Steam volume fraction SVF_gas_Z6_R_ti _X.dat Vertical profiles Droplet temperature R12, t=600s, T_d_z_R12_ti_X.dat t=tfin Droplet diameters D_d_z_R12_ti_X.dat Droplet temperature R7, t=600s, T_d_z_R7_ti_X.dat t=tfin Droplet diameters D_d_z_R7_ti_X.dat *location Z14 is ‘a location close to the spray injection’, since it can vary from codes to experiments ** droplet diameters (size distribution) have been measured at Z10 on the TOSQAN axis, at different times *** in bold: figure presented in this paper Table 7: requested results for the TOSQAN benchmarks.

Time evolutions of gas temperatures close to the spray injection (Z14) and at Z6 (200 cm from the spray nozzle) are given on Figure 4 and the radial profile at Z14 on Figure 6. The experimental results show that the gas temperature is higher at Z6 than at Z14 (Figure 4). This is probably mainly due to the spray because more droplets are present close to the injection, leading to higher energy exchange with the gas, and thus a higher cooling of the gas at Z14 than Z6. All codes show this same behavior. However, this difference of temperature ∆TZ6-Z14 between both locations is not the same in all codes, either much higher or of the opposite site (Figure 5). For codes having ∆TZ6-Z14 higher (TONUS and GASFLOW), one explanation could come from the “way” the spray is dispersed downward. If the spray is too “concentrated” on the TOSQAN axis, its effect on the gas cooling is higher. This explanation seems to be confirmed by the radial profiles (Figure 6): even if the number of experimental points is limited, it can be seen that the width of the gas temperature zone “cooled” by the spray is larger in the experiment than in these two codes.



TOSQAN Spray benchmark - TEST 101 TOSQAN Spray Benchmark - TEST 101 140 TOSQAN Z6_R12 GASFLOW (2D) TONUS-CFD (2D) GOTHIC - HTC*3,5 (2D) GOTHIC - HTC*10 (2D) ASTEC/CPA (0D - mean value)

130

110

90

gas temperature (°C)


130

TOSQAN Z13_R12 GASFLOW (2D) TONUS-CFD (2D) GOTHIC - HTC*3.5 (2D) GOTHIC - HTC*10 (2D) ASTEC/CPA (0D - mean value)

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Figure 4: time evolution of the gas temperature close to the spray injection (Z14, left) and at Z6 (right), on the TOSQAN axis. TOSQAN Spray Benchmark - TEST 101 TOSQAN Spray Benchmark - TEST 101

120

60

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TOSQAN Z6_R12 GASFLOW (2D) TONUS-CFD (2D) GOTHIC - HTC*3,5 (2D) GOTHIC - HTC*10 (2D)

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90 80 TOSQAN - Zn = 22 cm

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GOTHIC HTC*10 - Zn = 10 cm Zn = distance from the spray nozzle

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0,75

radius (m) / steady state time (s)

Figure 5: gas temperature difference between the location Z6 and Z14.

Figure 6: radial profile at Z14, at TOSQAN axis, at final equilibrium.

Results on steam volume fraction (SVF) are presented on the same way as the one used for gas temperature: two time evolutions at Z6 and Z14 (Figure 7) and one radial profile close to the injection at final equilibrium (Figure 9). The SVF difference between Z6 and Z14 (between 200 and 10 cm from the nozzle) is presented on Figure 8 for the codes, and a vertical profile of SVF measured experimentally between 40 and 15 cm is given on Figure 10. From the latter figure, it could be concluded that a decrease of steam concentration is observed close to the injection due to steam condensation on droplets (the mass stratification is around 1-3% considering the experimental fluctuations). Concerning the codes, TONUS code and one calculation of GOTHIC shows clearly this effect of steam condensation, but the one calculated by TONUS seems to be too high: it corresponds to a linear increase of 1%vol/25 cm over 2 m high. This is the right variation for the dense spray region near the nozzle, but is probably too high for the zone where the spray region is less dense. This confirms the results obtained for gas temperature showing that the spray is not enough diluted in the TONUS calculations. The negative value of this concentration difference obtained for some calculations is probably due to droplet evaporation taken into account in the modelling. From the radial profiles, it can be seen that GOTHIC and GASFLOW have approximately the same level of steam volume fraction as in the experiment (and as well as the same level of final pressure, as it has been seen before), whereas the TONUS one is lower. This is a normal result since the TONUS modelling does not take into account any droplet evaporation on structures as it is done in GASFLOW and GOTHIC (in different ways): the effect of such modelling has a great importance to reach the experimental steam partial pressure and total pressure. The first European Review Meeting on Severe Accident Research (ERSMAR-2005) Aix-en-Provence, France, November 14-16, 2005


TOSQAN Spray Benchmark - TEST101

TOSQAN Spray Benchmark - TEST 101

0,70

0,70 0,65

0,60 steam volume fraction - C

steam volume fraction - C

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TOSQAN 040604 - Zn = 15 cm GASFLOW (2D) - Zn = 10 cm TONUS (2D) - Zn = 10 cm GOTHIC-HTC*3.5 (2D) - Zn = 10 cm GOTHIC-HTC*10 (2D) - Zn = 10 cm ASTEC/CPA - Mean

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0,55 0,50 0,45 0,40 TOSQAN 261004 - Zn = 24 cm TOSQAN 271004 - Zn = 24 cm GASFLOW (2D) - Zn = 205.5 cm TONUS (2D) - Zn = 205.5 cm GOTHIC-HTC*3.5 (2D) - Zn = 205.5 cm GOTHIC-HTC*10 (2D) - Zn = 205.5 cm ASTEC/CPA - Mean

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Figure 7: time evolution of SVF on Z14 (left) and at Z6 (right) on TOSQAN axis. TOSQAN Spray Benchmark - TEST 101

TOSQAN Spray Benchmark - TEST 101 0,60

GASFLOW (2D) - (Z6-Z14) TONUS (2D) - (Z6-Z14) 0,15

0,50

GOTHIC - HTC*3,5 (2D) - (Z6-Z14)

steam volume fraction - C

difference of steam volume fraction between Z6 and Z14

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TOSQAN spray test 101 - 040604 60

55 Steam volume fraction (%)

Measurements on the droplet velocities have also been performed close to the spray nozzle, at two locations: 5 and 15 cm from the nozzle, on the TOSQAN axis (Figure 11). However, numerical results cannot really be compared regarding to the level of velocities, since the injection velocities in the codes were much lower than the one obtained in the experiment (experimental results obtained after the calculations have begun). However, it can also be seen on this figure that the calculated width of the spray is much lower than in the experiment: since the ‘experimental’ spray angle has been used in the codes, the low level of velocity used numerically explains probably the smaller width of the calculated spray profiles and its effect on the temperature and steam volume fraction described earlier in this paper.

0,00

Figure 9: steam volume fraction radial profile at Z14 on TOSQAN axis.

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Figure 10: vertical profile of the steam volume fraction on the TOSQAN axis. TOSQAN Spray Benchmark - TEST 101 10 8 Droplet velocity - Ud_z (m/s)

Figure 8: difference of steam volume fraction between Z6 and Z14.

-0,15

radius (m) / final equilibrium

time (s)

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TOSQAN 281004 - Zn = 5 cm TOSQAN 281004 - Zn = 15 cm GASFLOW (2D) Z13_R - Zn = 10 cm TONUS (2D) Z13_R - Zn = 10 cm GOTHIC-HTC*3.5 (2D) Z13_R - Zn = 10 cm GOTHIC-HTC*10 (2D) Z13_R - Zn = 10 cm

2 0 -2 -4 -6 -8 -10 -0,75 -0,65 -0,55 -0,45 -0,35 -0,25 -0,15 -0,05 0,05

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Figure 11: droplet velocities radial profile near the injection at final equilibrium. The first European Review Meeting on Severe Accident Research (ERSMAR-2005) Aix-en-Provence, France, November 14-16, 2005


F. CONCLUSION Two exercises on TOSQAN spray test 101 have been performed in 2004 and 2005 in the frame of a benchmark. They concern multi-dimensional and lumped-parameter codes. The first phase of this benchmark has shown that the droplet-wall interaction in TOSQAN could not be neglected in the modelling to reach the experimental level of pressure. The second phase of this benchmark shows that the difference between both modelling lies between 20 and 46% on the calculated pressure. It shows also that there are different ways to model the droplet-wall interaction, and that, at that time, no experimental measurements on TOSQAN allow concluding how this droplet-wall interaction has to be modeled. The other point of this second phase is the importance of the spray boundary conditions that were measured after this phase has begun. It is found that the multi-dimensional codes calculate generally a much denser spray near the TOSQAN axis, resulting to a higher influence of the spray in this region: further post-calculations by the CFD-codes, taking into account the spray characteristics close to the injection, appear important to confirm these results. G. PERSPECTIVE

A third phase of this benchmark on Test 101 is proposed for further calculations for multidimensionnal codes. It is also open to new participants of SARNET (LP or CFD codes). A second TOSQAN spray benchmark based on Test 113 is proposed since June 2005, which concerns more specifically gas-droplet momentum exchange (no heat and mass transfer). Test 113 is a cold spray injected in an initially air-helium stratified mixture with helium located on the upper part of the vessel. It is proposed to calculate the helium pressurization and stratification, as well as the air-helium mixing by the spray. Specifications of this test can be given in the frame of SARNET and found in [8]. REFERENCES [1] Malet J. , E. Porcheron, J. Vendel, 2005, Filmwise condensation applied to containment studies: conclusions of the TOSQAN air-steam condensation tests, NURETH-11, Avignon, France. [2] Malet J., E. Porcheron, P. Cornet, J. Vendel, K. Fischer, 2003, Scaling of water spray in large enclosures – Application to nuclear reactor spraying systems, NURETH-10, Seoul, Korea [3] Auban O., J. Malet, P. Brun, J. Brinster, J. J. Quillico., E. Studer, 2003, Implementation of gas concentration measurement systems using mass spectrometry in containment thermal-hydraulics test facilities: different approaches for calibration and measurement with steam/air/helium mixtures, NURETH-10, Seoul, Korea [4] Porcheron E., P. Brun, P. Cornet, J. Malet, J. Vendel, 2003, Optical diagnostics applied for single and multi-phase flow characterization in the TOSQAN facility dedicated for thermal hydraulic containment studies, NURETH-10, Seoul, Korea [5] Fischer K. et al. 2002, Scaling of containment experiments (SCACEX), European contract n°FIR1CT2001-20127, Final Project Report [6] Malet J., P. Lemaitre., E. Porcheron, J. Vendel, 2005, Water spray interaction with air-steam mixtures under containment spray conditions: comparison of heat and mass transfer modelling with the TOSQAN spray tests, NURETH-11, Avignon, France [7] Porcheron P., P. Lemaitre, J. Malet, A. Nuboer, P. Br un, L. Bouilloux, J. Vendel, 2005, Water interaction with air / steam mixtures under spray containment conditions: experimental study in the TOSQAN facility, NURETH-11, Avignon, France [8] Malet J., E. Porcheron, P. Lemaître, J. Vendel, P. Royl, J. Travis, 2005, TOSQAN Spray Benchmark n°2: TOSQAN Test 113: Helium mixing due to spray activation – Specification report Rev. 0, Report IRSN/DSU/SERAC/LEMAC/05-20
