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Design of a new experimental facility to reproduce LOVA and LOCA consequences on dust resuspension
Fusion Engineering and Design 98–99 (2015) 2191–2195
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Design of a new experimental facility to reproduce LOVA and LOCA consequences on dust resuspension A. Malizia ∗ , M. Gelfusa, G. Francia, M. Boccitto, M. Del Vecchio, D. Di Giovanni, M. Richetta, C. Bellecci, P. Gaudio Associazione EURATOM-ENEA, Department of Industrial Engineering, Quantum Electronics and Plasma Physics Research Group (QEP), University of Rome “Tor Vergata”, Via del Politecnico 1, 00133 Rome, Italy
h i g h l i g h t s • Design and realization of new experimental facility. • Numerical simulation to test the mechanical resistance of the new facility. • New way to experimentally reproduce LOVA and LOCA consequences on dust resuspension inside the tokamaks.
a r t i c l e
i n f o
Article history: Received 28 August 2014 Accepted 13 November 2014 Available online 19 December 2014 Keywords: Security ITER LOVA LOCA
a b s t r a c t Dust resuspension inside the vacuum vessel is one of the key security issues of the new-generation tokamaks (such as ITER or DEMO). It is well known that a fusion device generates dusts due to plasma–surface interactions, which cause a significant erosion of plasma facing components. Consequently, operators will have to manage several hundreds of kilograms of beryllium and tungsten dusts inside the VV. According to the reference categories, two main accidental situations lead to dusts re-suspension: loss of vacuum accidents (LOVA – air flow due to a rupture of a penetration line) and loss of coolant accidents (LOCA – fluid flashing due to a rupture of a coolant system pipe). The authors have gained a strong experience in the field of dust resuspension by virtue of the studies on the STARDUST facility, whose limitations, however, prevent from completing further analysis. These are, in particular, a reduced field of view to track the dust with optical techniques, the impossibility to replicate a LOVA from the upper port as well as any kind of LOCA. To overcome these problems, the authors have designed several new layouts of the facility. Numerical simulations to test the mechanical resistance together with a deep analysis of advantages and limitations have been performed for each layout. The authors will present the proposals for the new facility, the numerical results of the simulations and a comparison between the layouts analyzed. A new experimental facility will be then described to reproduce dust re-suspension due to both LOVA and LOCA consequences. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Nuclear fusion is expected to be one of the most important alternatives for energy production for the future generations. One of the key safety and security aspects for the next generation plants (such as ITER and DEMO) will be the production of huge amount of dust during normal operation [1,2]. The accidents (such as loss of vacuum accidents (LOVA), loss of coolant accidents (LOCA) or
∗ Corresponding author. Tel.: +39 3666000132. E-mail address: [email protected] (A. Malizia). http://dx.doi.org/10.1016/j.fusengdes.2014.11.009 0920-3796/© 2014 Elsevier B.V. All rights reserved.
loss of coolant flow accidents (LOFA)), which can provoke this resuspension of dust, are objects of research activities of quantum electronics and plasma (QEP) Physics Research Group of University at Rome “Tor Vergata”. The QEP research group, in collaboration with ENEA FUS TECH (Frascati), developed the facility STARDUST [3–9] to analyze the LOVA effects on dust re-suspension [7–9]. Using the STARDUST facility the QEP research group developed and validated an extruded 2D thermofluidodynamic model [3,5,6,9,10] to analyze the effect of a LOVA on dust. Optical techniques, PIV [11,12] and Shadowgraph [12,13], have been used to track the dust in the early stages of the accident simulations by means of images collection at high frequencies rates [11–13]. In collaboration with
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A. Malizia et al. / Fusion Engineering and Design 98–99 (2015) 2191–2195
the University of Madrid also numerical algorithms to track the dust re-suspended in post-processing data analysis [11–13] have been developed. The main limitations of the STARDUST facility are: • It is not possible to experimentally simulate a LOCA accident [11–13]. • The field of view is small and it is not possible to track the dust for long distance from the air inlet [11–13]. • It is not possible to replicate LOVAs for more than one accidental configuration [11–13]. The QEP research group has designed and implemented mechanical modifications to STARDUST in order to get a facility with a bigger field of view through the introduction of new windows with a larger diameter together with the introduction of new air inlet and different lid configurations. These implementation have been designed in 3D with the software Solidworks and the mechanical resistance has been tested numerically (with the same software) to verify the mechanical resistance of the new facility under the experimental boundary conditions expected to reproduce LOVA and LOCA that is essential for the future studies on safety and security inside the nuclear fusion plants [14]. The final layout of the facility has been design and built joining the best characteristics of the different layouts numerically tested. The numerical simulations and the principal results will be presented in the paper by the authors together with the final layout realized. 2. The new facility – implementation The authors started the work from the 3D designs of the new STARDUST facility. Taking into account that the implementations needed are related to an increase of the field of view and of the inlet points of compressed air in order to allow an improvement to the dust tracking and a higher range of experimental accident conditions, the authors have designed and tested two different layouts. The software used is SOLIDWORKS2013® that allows also the possibility to assign the material characteristics and mechanical constraints and to simulate the stress of the different components of the tank (lids, windows and walls) under the vacuum conditions expected inside the tank during the experiments. The first boundary conditions assigned are the characteristics of the material of the tank’s components: Stainless Steel AISI 316L for walls and lids; quartz for the windows, in order to properly simulate the mechanical behavior during the simulations (see Figs. 1 and 2). Since the quartz data were available in the software library, they have been obtained from literature and added to the database.
Fig. 2. Constraints assumed the lids.
The simulation phase has been carried out according to the steps below: • • • • •
Calculation of the distributed load to be applied. Assignment of constraints. Application of the load. Mesh elaboration. Simulation and plotting of results.
It is important to point out that the tank, the lids and the windows have been studied separately to facilitate mesh elaboration and the subsequent mechanical tests, as well as the complex study of constraints between glasses and their frames. In particular, in order to test the glass resistance, the output values obtained from the simulation for the tank and lids have been used as displacement and deformation input values to be assigned to the edges. The load used in the simulations is due to an internal pressure of 100 Pa and an external pressure of one atmosphere. With regards the tank, the load value is obtained by multiplying the internal–external pressure variation by the total internal surface: P ∗ Atot = 101, 125 Pa ∗ 1.43 m2 = 144, 608.75 N
(1)
The same procedure has been used to test the lid (2): P ∗ Atot = 101, 125 Pa ∗ 0.255 m2 = 25791.58 N
(2)
with: • P difference between the tank internal pressure and the external one. • Atot surface subject to the distributed load. As constraints, with regard to the tank, we have considered the lid flange joints, because these do not affect the simulation and are not subject to a pressure gradient; similarly, the constraints to be adopted for the lids are the external edges where the bolts are housed. The obtained and plotted results are: • Stresses () in every point, calculated in N/m2 (Pa). • Displacements, in mm. • Equivalent deformation, defined as ESTRN and calculated as follows (3):
ε + ε (1/2) 1 2
Fig. 1. Constraints assumed the lids.
ESTRN = 2
3
(3)
A. Malizia et al. / Fusion Engineering and Design 98–99 (2015) 2191–2195
2193
differences of the stress and deformations between the different layouts (see Table 1). The stresses are higher than the one of the old layout. The safety factor (FOS) is always higher than 1 in all the simulations and the deformations and displacements are comparable to those of the old layout. The numerical simulations of the two different layouts demonstrate the feasibility of the mechanical implementations proposed under the experimental conditions expected. The final layout proposed by QEP presents the following implementations: • Two lids with quartz windows with a diameter of 21.5 cm placed at the equatorial level (with the center coincident with the two axis of symmetry of the tank, see Fig. 6). • Two lids with quartz windows with a diameter of 21.5 cm placed at the divertor level (bottom part of the tank see Fig. 6).
Fig. 3. Stresses and displacements of the wall’s tank.
with: ε1 = 0.5[(εx − ε∗)2 + (εy − ε∗)2 + (εz − ε∗)2 ] 2
2
(xy ) + (xz ) + (yz ) 4 εx + εy + εz ε∗ = 3
(4)
2
ε2 =
(5) (6)
For details on variables components see [15]. • Safety factor (FOS): defined as the ratio between the yield stress and the Von Mises stress, regarded as the most suitable to evaluate ductile materials. The theory states that a ductile material starts to yield in a given point when the Von Mises stress equals the stress point that, in this case, is considered the yield point. For safety purposes, it must be vonMises ≤ limite , that is, in every point FOS > 1.
Fig. 4. Stress and deformations of the lid.
3. Results and data discussion In this section, the results of one case of the stress simulations are showed. Fig. 3 shows the stress and movements of the wall under an internal vacuum condition of 100 Pa (and a wall temperature of 140 ◦ C). The same conditions have been used to simulate stresses, deformations and displacements of the lids (see Fig. 4). The stress tensor of the lid, under the vacuum conditions expected, has been used as boundary condition to simulate the stress of the quartz window that has been placed on it. This is necessary to verify the resistance of the window under the experimental worst conditions (see Fig. 5) The stress simulations have been developed for both the new experimental layout proposed and also for the old STARDUST configuration. The results have been compared in order to evaluate the
Fig. 5. Stress tensor of the quartz window.
Table 1 Deformations and stress comparison. Old layout
Layout 1
Layout 2
Lid layout 1
Lid layout 2
Stress (MPa) Max Min
4.65 0.012
9.3 0.08
15 0.012
46 0.15
35 0.02
Displacements (mm) Max Min
4 × 10−3 1 × 10−3
3.5 × 10−2 1 × 10−7
2.7 × 10−2 2.2 × 10−7
3.5 × 10−1 3 × 10−6
2.1 × 10−1 1.5 × 10−4
Deformations (mm) Max Min
1.3 × 10−5 8.5 × 10−8
4.5 × 10−5 6 × 10−1 ◦
4.2 × 10−5 1.9 × 10−7
1.2 × 10−4 2 × 10−5
1.2 × 10−4 3.4 × 10−7
FOS Max Min
>20 7.5
>20 1.5
>20 1.4
>20 4.1
>20 1.9
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Fig. 6. New Experimental Layout.
• A new quartz window with a diameter of 21.5 cm on the top of the tank (see Fig. 6).
• Two new air inlet of the top of the tank in order to simulate LOCA air recirculation consequences (see Fig. 6). 4. Conclusions and future developments
The new windows added can be replaced with similar windows with a lower diameter (15 cm) in order to obtain different combination of field of view (FOV) important to implement PIV and Shadowgraph experiments [11–13].
• Two air inlets on the lateral wall to simulate LOVA with an air recirculation comparable to those expected in ITER (see conclusion of [5]).
The authors have performed numerical simulations to test the feasibility of the implementation proposed for the experimental facility and this is important to optimize the realization of the new layouts in terms of mechanical resistance and costs. The implementations selected allow to: (1) increase the FOV inside the chamber in order to optimize the images acquisition with optical techniques; (2) experimentally simulate new LOVA conditions and also the LOCA consequences. These were the main
A. Malizia et al. / Fusion Engineering and Design 98–99 (2015) 2191–2195
objectives necessary to continue the experimental activities in this important field of nuclear fusion safety and security. The future developments are: (1) characterize the thermofluidodynamic behavior of the new configuration both experimentally and numerically; (2) develop a multiphase model of dust dispersion in case of LOVA. Acknowledgments A special thanks to the factory that has realized the new facility: ISOLCERAM (http://www.isolceram.it/) and to its owner Mauro Ugazio. References [1] P. Gaudio, A. Malizia, I. Lupelli, Experimental and numerical analysis of dust resuspension for supporting chemical and radiological risk assessment in a nuclear fusion device, in: International Conference on Mathematical Models for Engineering Science – Proceedings, 2010, pp. 134–147. [2] A. Malizia, I. Lupelli, M. Richetta, M. Gelfusa, C. Bellecci, P. Gaudio, Safety analysis in large volume vacuum systems like tokamak: experiments and numerical simulation to analyze vacuum ruptures consequences, Adv. Mater. Sci. Eng. (2014), http://dx.doi.org/10.1155/2014/201831, 30 pp., Article ID 201831. [3] M. Benedetti, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, M. Richetta, Large eddy simulation of loss of vacuum accident in STARDUST facility, Fusion Eng. Des. 88 (9–10) (2013) 2665–2668. [4] C. Bellecci, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, R. Quaranta, et al., Validation of a loss of vacuum accident (LOVA) computational fluid dynamics (CFD) model, Fusion Eng. Des. 86 (9–11) (2011) 2774–2778. [5] C. Bellecci, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, R. Quaranta, et al., STARDUST experimental campaign and numerical simulations: influence of obstacles and temperature on dust resuspension in a vacuum vessel under LOVA, Nucl. Fusion 51 (5) (2011), Art. No. 053017.
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[6] C. Bellecci, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, R. Quaranta, et al., Loss of vacuum accident (LOVA): comparison of computational fluid dynamics (CFD) flow velocities against experimental data for the model validation, Fusion Eng. Des. 86 (4–5) (2011) 330–340. [7] M. Benedetti, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, M. Richetta, Scaled experiment for loss of vacuum accidents in nuclear fusion devices: experimental methodology for fluid-dynamics analysis in STARDUST facility, in: Recent Researches in Mechanics – Proc. of the 2nd Int. Conf. on FLUIDSHEAT’11, TAM’11, Proc. of the 4th WSEAS Int. Conf. UPT’11, CUHT’11, 2011, pp. 142–147. [8] C. Bellecci, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, R. Quaranta, et al., Experimental mapping of velocity flow field in case of L.O.V.A. inside stardust facility, in: 37th EPS Conference on Plasma Physics 2010. EPS 2010, vol. 2, 2010, pp. 703–706. [9] C. Bellecci, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, R. Quaranta, et al., Characterization of divertor influence in case of LOVA: CFD analysis of stardust experimental facility, in: 36th EPS Conference on Plasma Physics 2009, EPS 2009 – Europhysics Conference Abstracts, 33 E1, 2009, pp. 266–269. [10] I. Lupelli, P. Gaudio, M. Gelfusa, A. Malizia, I. Belluzzo, M. Richetta, Numerical study of air jet flow field during a loss of vacuum, Fusion Eng. Des. 89 (9–10) (2014) 2048–2052. [11] A. Malizia, M. Camplani, M. Gelfusa, I. Lupelli, M. Richetta, L. Antonelli, et al., Dust tracking techniques applied at STARDUST facility: first results, Fusion Eng. Des. 89 (9–10) (2014) 2098–2102. [12] A. Malizia, M. Camplani, M. Gelfusa, L. Antonelli, F. Barbato, M. Del Vecchio, et al., Dust mobilization and transport measures in the STARDUST facility, in: EPS2008 Proceedings, 41st EPS Conference on Plasma Physics, Berlin Germany, 23–27 June 2014, vol. 38F, 2014, P-5.006. [13] P. Gaudio, A. Malizia, M. Camplani, F. Barbato, L. Antonelli, M. Gelfusa, et al., Shadowgraph technique applied to STARDUST facility for dust tracking: first results, in: Proceedings ICFDT 2013 Conference, INFN, Frascati, 25–27 November, 2013, 2013. [14] T. Pinna, L.C. Cadwallader, G. Cambi, S. Ciattaglia, S. Knipe, F. Leuterer, et al., Operating experiences from existing fusion facilities in view of ITER safety and reliability, Fusion Eng. Des. 85 (7–9) (2010) 1410–1415. [15] User Guide of Solidworks, 2013.
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Design of a new experimental facility to reproduce LOVA and LOCA consequences on dust resuspension A. Malizia ∗ , M. Gelfusa, G. Francia, M. Boccitto, M. Del Vecchio, D. Di Giovanni, M. Richetta, C. Bellecci, P. Gaudio Associazione EURATOM-ENEA, Department of Industrial Engineering, Quantum Electronics and Plasma Physics Research Group (QEP), University of Rome “Tor Vergata”, Via del Politecnico 1, 00133 Rome, Italy
h i g h l i g h t s • Design and realization of new experimental facility. • Numerical simulation to test the mechanical resistance of the new facility. • New way to experimentally reproduce LOVA and LOCA consequences on dust resuspension inside the tokamaks.
a r t i c l e
i n f o
Article history: Received 28 August 2014 Accepted 13 November 2014 Available online 19 December 2014 Keywords: Security ITER LOVA LOCA
a b s t r a c t Dust resuspension inside the vacuum vessel is one of the key security issues of the new-generation tokamaks (such as ITER or DEMO). It is well known that a fusion device generates dusts due to plasma–surface interactions, which cause a significant erosion of plasma facing components. Consequently, operators will have to manage several hundreds of kilograms of beryllium and tungsten dusts inside the VV. According to the reference categories, two main accidental situations lead to dusts re-suspension: loss of vacuum accidents (LOVA – air flow due to a rupture of a penetration line) and loss of coolant accidents (LOCA – fluid flashing due to a rupture of a coolant system pipe). The authors have gained a strong experience in the field of dust resuspension by virtue of the studies on the STARDUST facility, whose limitations, however, prevent from completing further analysis. These are, in particular, a reduced field of view to track the dust with optical techniques, the impossibility to replicate a LOVA from the upper port as well as any kind of LOCA. To overcome these problems, the authors have designed several new layouts of the facility. Numerical simulations to test the mechanical resistance together with a deep analysis of advantages and limitations have been performed for each layout. The authors will present the proposals for the new facility, the numerical results of the simulations and a comparison between the layouts analyzed. A new experimental facility will be then described to reproduce dust re-suspension due to both LOVA and LOCA consequences. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Nuclear fusion is expected to be one of the most important alternatives for energy production for the future generations. One of the key safety and security aspects for the next generation plants (such as ITER and DEMO) will be the production of huge amount of dust during normal operation [1,2]. The accidents (such as loss of vacuum accidents (LOVA), loss of coolant accidents (LOCA) or
∗ Corresponding author. Tel.: +39 3666000132. E-mail address: [email protected] (A. Malizia). http://dx.doi.org/10.1016/j.fusengdes.2014.11.009 0920-3796/© 2014 Elsevier B.V. All rights reserved.
loss of coolant flow accidents (LOFA)), which can provoke this resuspension of dust, are objects of research activities of quantum electronics and plasma (QEP) Physics Research Group of University at Rome “Tor Vergata”. The QEP research group, in collaboration with ENEA FUS TECH (Frascati), developed the facility STARDUST [3–9] to analyze the LOVA effects on dust re-suspension [7–9]. Using the STARDUST facility the QEP research group developed and validated an extruded 2D thermofluidodynamic model [3,5,6,9,10] to analyze the effect of a LOVA on dust. Optical techniques, PIV [11,12] and Shadowgraph [12,13], have been used to track the dust in the early stages of the accident simulations by means of images collection at high frequencies rates [11–13]. In collaboration with
2192
A. Malizia et al. / Fusion Engineering and Design 98–99 (2015) 2191–2195
the University of Madrid also numerical algorithms to track the dust re-suspended in post-processing data analysis [11–13] have been developed. The main limitations of the STARDUST facility are: • It is not possible to experimentally simulate a LOCA accident [11–13]. • The field of view is small and it is not possible to track the dust for long distance from the air inlet [11–13]. • It is not possible to replicate LOVAs for more than one accidental configuration [11–13]. The QEP research group has designed and implemented mechanical modifications to STARDUST in order to get a facility with a bigger field of view through the introduction of new windows with a larger diameter together with the introduction of new air inlet and different lid configurations. These implementation have been designed in 3D with the software Solidworks and the mechanical resistance has been tested numerically (with the same software) to verify the mechanical resistance of the new facility under the experimental boundary conditions expected to reproduce LOVA and LOCA that is essential for the future studies on safety and security inside the nuclear fusion plants [14]. The final layout of the facility has been design and built joining the best characteristics of the different layouts numerically tested. The numerical simulations and the principal results will be presented in the paper by the authors together with the final layout realized. 2. The new facility – implementation The authors started the work from the 3D designs of the new STARDUST facility. Taking into account that the implementations needed are related to an increase of the field of view and of the inlet points of compressed air in order to allow an improvement to the dust tracking and a higher range of experimental accident conditions, the authors have designed and tested two different layouts. The software used is SOLIDWORKS2013® that allows also the possibility to assign the material characteristics and mechanical constraints and to simulate the stress of the different components of the tank (lids, windows and walls) under the vacuum conditions expected inside the tank during the experiments. The first boundary conditions assigned are the characteristics of the material of the tank’s components: Stainless Steel AISI 316L for walls and lids; quartz for the windows, in order to properly simulate the mechanical behavior during the simulations (see Figs. 1 and 2). Since the quartz data were available in the software library, they have been obtained from literature and added to the database.
Fig. 2. Constraints assumed the lids.
The simulation phase has been carried out according to the steps below: • • • • •
Calculation of the distributed load to be applied. Assignment of constraints. Application of the load. Mesh elaboration. Simulation and plotting of results.
It is important to point out that the tank, the lids and the windows have been studied separately to facilitate mesh elaboration and the subsequent mechanical tests, as well as the complex study of constraints between glasses and their frames. In particular, in order to test the glass resistance, the output values obtained from the simulation for the tank and lids have been used as displacement and deformation input values to be assigned to the edges. The load used in the simulations is due to an internal pressure of 100 Pa and an external pressure of one atmosphere. With regards the tank, the load value is obtained by multiplying the internal–external pressure variation by the total internal surface: P ∗ Atot = 101, 125 Pa ∗ 1.43 m2 = 144, 608.75 N
(1)
The same procedure has been used to test the lid (2): P ∗ Atot = 101, 125 Pa ∗ 0.255 m2 = 25791.58 N
(2)
with: • P difference between the tank internal pressure and the external one. • Atot surface subject to the distributed load. As constraints, with regard to the tank, we have considered the lid flange joints, because these do not affect the simulation and are not subject to a pressure gradient; similarly, the constraints to be adopted for the lids are the external edges where the bolts are housed. The obtained and plotted results are: • Stresses () in every point, calculated in N/m2 (Pa). • Displacements, in mm. • Equivalent deformation, defined as ESTRN and calculated as follows (3):
ε + ε (1/2) 1 2
Fig. 1. Constraints assumed the lids.
ESTRN = 2
3
(3)
A. Malizia et al. / Fusion Engineering and Design 98–99 (2015) 2191–2195
2193
differences of the stress and deformations between the different layouts (see Table 1). The stresses are higher than the one of the old layout. The safety factor (FOS) is always higher than 1 in all the simulations and the deformations and displacements are comparable to those of the old layout. The numerical simulations of the two different layouts demonstrate the feasibility of the mechanical implementations proposed under the experimental conditions expected. The final layout proposed by QEP presents the following implementations: • Two lids with quartz windows with a diameter of 21.5 cm placed at the equatorial level (with the center coincident with the two axis of symmetry of the tank, see Fig. 6). • Two lids with quartz windows with a diameter of 21.5 cm placed at the divertor level (bottom part of the tank see Fig. 6).
Fig. 3. Stresses and displacements of the wall’s tank.
with: ε1 = 0.5[(εx − ε∗)2 + (εy − ε∗)2 + (εz − ε∗)2 ] 2
2
(xy ) + (xz ) + (yz ) 4 εx + εy + εz ε∗ = 3
(4)
2
ε2 =
(5) (6)
For details on variables components see [15]. • Safety factor (FOS): defined as the ratio between the yield stress and the Von Mises stress, regarded as the most suitable to evaluate ductile materials. The theory states that a ductile material starts to yield in a given point when the Von Mises stress equals the stress point that, in this case, is considered the yield point. For safety purposes, it must be vonMises ≤ limite , that is, in every point FOS > 1.
Fig. 4. Stress and deformations of the lid.
3. Results and data discussion In this section, the results of one case of the stress simulations are showed. Fig. 3 shows the stress and movements of the wall under an internal vacuum condition of 100 Pa (and a wall temperature of 140 ◦ C). The same conditions have been used to simulate stresses, deformations and displacements of the lids (see Fig. 4). The stress tensor of the lid, under the vacuum conditions expected, has been used as boundary condition to simulate the stress of the quartz window that has been placed on it. This is necessary to verify the resistance of the window under the experimental worst conditions (see Fig. 5) The stress simulations have been developed for both the new experimental layout proposed and also for the old STARDUST configuration. The results have been compared in order to evaluate the
Fig. 5. Stress tensor of the quartz window.
Table 1 Deformations and stress comparison. Old layout
Layout 1
Layout 2
Lid layout 1
Lid layout 2
Stress (MPa) Max Min
4.65 0.012
9.3 0.08
15 0.012
46 0.15
35 0.02
Displacements (mm) Max Min
4 × 10−3 1 × 10−3
3.5 × 10−2 1 × 10−7
2.7 × 10−2 2.2 × 10−7
3.5 × 10−1 3 × 10−6
2.1 × 10−1 1.5 × 10−4
Deformations (mm) Max Min
1.3 × 10−5 8.5 × 10−8
4.5 × 10−5 6 × 10−1 ◦
4.2 × 10−5 1.9 × 10−7
1.2 × 10−4 2 × 10−5
1.2 × 10−4 3.4 × 10−7
FOS Max Min
>20 7.5
>20 1.5
>20 1.4
>20 4.1
>20 1.9
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Fig. 6. New Experimental Layout.
• A new quartz window with a diameter of 21.5 cm on the top of the tank (see Fig. 6).
• Two new air inlet of the top of the tank in order to simulate LOCA air recirculation consequences (see Fig. 6). 4. Conclusions and future developments
The new windows added can be replaced with similar windows with a lower diameter (15 cm) in order to obtain different combination of field of view (FOV) important to implement PIV and Shadowgraph experiments [11–13].
• Two air inlets on the lateral wall to simulate LOVA with an air recirculation comparable to those expected in ITER (see conclusion of [5]).
The authors have performed numerical simulations to test the feasibility of the implementation proposed for the experimental facility and this is important to optimize the realization of the new layouts in terms of mechanical resistance and costs. The implementations selected allow to: (1) increase the FOV inside the chamber in order to optimize the images acquisition with optical techniques; (2) experimentally simulate new LOVA conditions and also the LOCA consequences. These were the main
A. Malizia et al. / Fusion Engineering and Design 98–99 (2015) 2191–2195
objectives necessary to continue the experimental activities in this important field of nuclear fusion safety and security. The future developments are: (1) characterize the thermofluidodynamic behavior of the new configuration both experimentally and numerically; (2) develop a multiphase model of dust dispersion in case of LOVA. Acknowledgments A special thanks to the factory that has realized the new facility: ISOLCERAM (http://www.isolceram.it/) and to its owner Mauro Ugazio. References [1] P. Gaudio, A. Malizia, I. Lupelli, Experimental and numerical analysis of dust resuspension for supporting chemical and radiological risk assessment in a nuclear fusion device, in: International Conference on Mathematical Models for Engineering Science – Proceedings, 2010, pp. 134–147. [2] A. Malizia, I. Lupelli, M. Richetta, M. Gelfusa, C. Bellecci, P. Gaudio, Safety analysis in large volume vacuum systems like tokamak: experiments and numerical simulation to analyze vacuum ruptures consequences, Adv. Mater. Sci. Eng. (2014), http://dx.doi.org/10.1155/2014/201831, 30 pp., Article ID 201831. [3] M. Benedetti, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, M. Richetta, Large eddy simulation of loss of vacuum accident in STARDUST facility, Fusion Eng. Des. 88 (9–10) (2013) 2665–2668. [4] C. Bellecci, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, R. Quaranta, et al., Validation of a loss of vacuum accident (LOVA) computational fluid dynamics (CFD) model, Fusion Eng. Des. 86 (9–11) (2011) 2774–2778. [5] C. Bellecci, P. Gaudio, I. Lupelli, A. Malizia, M.T. Porfiri, R. Quaranta, et al., STARDUST experimental campaign and numerical simulations: influence of obstacles and temperature on dust resuspension in a vacuum vessel under LOVA, Nucl. Fusion 51 (5) (2011), Art. No. 053017.
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