Articles de revistahttp://hdl.handle.net/2117/1847472020-07-09T14:59:42Z2020-07-09T14:59:42ZShear Alfvén wave continuum spectrum with bifurcated helical core equilibriaRakha, AllahLauber, PhilippMantsinen, Mervi JohannaSpong, Donaldhttp://hdl.handle.net/2117/1882052020-06-18T18:45:19Z2020-05-20T07:53:21ZShear Alfvén wave continuum spectrum with bifurcated helical core equilibria
Rakha, Allah; Lauber, Philipp; Mantsinen, Mervi Johanna; Spong, Donald
The radial structure of the continuum spectrum of shear Alfvén and Alfvén-acoustic waves in the beta-induced Alfvén eigenmode (BAE) frequency range is modeled for tokamak plasmas in the presence of 3D effects obtained from the bifurcated MHD equilibrium reconstruction. Plasma compressibility and geodesic curvature effects responsible for the low-frequency continuum spectrum calculations are invoked. In the equilibrium calculations we find that the helically distorted MHD equilibria may exist even for the axisymmetric devices if q = 1 rational surfaces are present. The continuum calculations with the bifurcated equilibria lead to a frequency splitting between the highest frequency branch and the lowest frequency branch continua at the frequency accumulation point. Radially localised shifting of modes happens via coupling of the adjacent n − 1 continuum around an accumulation point. Our modelling (including 3D effects) correctly reproduces the phenomenon of continuum frequency splitting and provides a possible solution for the differences of few kHz in frequency splitting, which remained unexplained with the 2D kinetic calculations (Curran et al 2012 Plasma Phys. Control. Fusion 54 055001). The pressure scaling confirms the increase of helical excursion of the magnetic axis in equilibrium reconstruction and hence the range of continuum frequency splitting. In our calculations, the existence of low-frequency continua is in agreement with the experimentally observed low-frequency modes.
2020-05-20T07:53:21ZRakha, AllahLauber, PhilippMantsinen, Mervi JohannaSpong, DonaldThe radial structure of the continuum spectrum of shear Alfvén and Alfvén-acoustic waves in the beta-induced Alfvén eigenmode (BAE) frequency range is modeled for tokamak plasmas in the presence of 3D effects obtained from the bifurcated MHD equilibrium reconstruction. Plasma compressibility and geodesic curvature effects responsible for the low-frequency continuum spectrum calculations are invoked. In the equilibrium calculations we find that the helically distorted MHD equilibria may exist even for the axisymmetric devices if q = 1 rational surfaces are present. The continuum calculations with the bifurcated equilibria lead to a frequency splitting between the highest frequency branch and the lowest frequency branch continua at the frequency accumulation point. Radially localised shifting of modes happens via coupling of the adjacent n − 1 continuum around an accumulation point. Our modelling (including 3D effects) correctly reproduces the phenomenon of continuum frequency splitting and provides a possible solution for the differences of few kHz in frequency splitting, which remained unexplained with the 2D kinetic calculations (Curran et al 2012 Plasma Phys. Control. Fusion 54 055001). The pressure scaling confirms the increase of helical excursion of the magnetic axis in equilibrium reconstruction and hence the range of continuum frequency splitting. In our calculations, the existence of low-frequency continua is in agreement with the experimentally observed low-frequency modes.Methodology for the improvement of the AINA code wall-model applied to DEMO WCPB blanketFabbri, MarcoBlas del Hoyo, Alfredo deRiego Pérez, AlbertDies Llovera, JavierZamora Poveda, ImanolBaeza Pérez, Eduardhttp://hdl.handle.net/2117/1880912020-05-20T05:54:56Z2020-05-19T11:42:13ZMethodology for the improvement of the AINA code wall-model applied to DEMO WCPB blanket
Fabbri, Marco; Blas del Hoyo, Alfredo de; Riego Pérez, Albert; Dies Llovera, Javier; Zamora Poveda, Imanol; Baeza Pérez, Eduard
The present work describes and supports the methodology for the improvement of the wall model devel-oped in AINA and its specific application to the Japanese DEMO Water Cooled Pebbled Bed. The set-upand application of this approach aims to obtain robust models by estimating the behavior of the studiedsystems as accurately as possible. These systems are represented in a simplified way. This requires thecomputation of a 3D radiation transport which has been carried out by means of MCNP6.1, ADVANTG andthermal-hydraulic calculations using ANSYS®Fluent®. Several CFD mesh typologies and discretizationshave also been employed to test the Richardson theorem. In addition, 1D simplified models have alsobeen created and optimized for their usage in AINA code. The temperature distribution also shows goodagreement (within 7%). In some cases the simplified models have not behaved in a conservative man-ner compared with the outcomes obtained for the 3D models. This observed absence of conservatism isintrinsic to the 1D approach. To cope with these effects, scaling functions have been determined as a ratiobetween the most conservative radial temperature distribution – computed by fully detailed 3D CFD –and the 1D simplified model. The scaling functions will be applied to the AINA computed wall tempera-ture distribution. To conclude, the determination and coherence of the result obtained using independenttools and approaches, ANSYS®Fluent®vs AINA thermal-hydraulic routines, lead us to recommend theproposed methodology.
2020-05-19T11:42:13ZFabbri, MarcoBlas del Hoyo, Alfredo deRiego Pérez, AlbertDies Llovera, JavierZamora Poveda, ImanolBaeza Pérez, EduardThe present work describes and supports the methodology for the improvement of the wall model devel-oped in AINA and its specific application to the Japanese DEMO Water Cooled Pebbled Bed. The set-upand application of this approach aims to obtain robust models by estimating the behavior of the studiedsystems as accurately as possible. These systems are represented in a simplified way. This requires thecomputation of a 3D radiation transport which has been carried out by means of MCNP6.1, ADVANTG andthermal-hydraulic calculations using ANSYS®Fluent®. Several CFD mesh typologies and discretizationshave also been employed to test the Richardson theorem. In addition, 1D simplified models have alsobeen created and optimized for their usage in AINA code. The temperature distribution also shows goodagreement (within 7%). In some cases the simplified models have not behaved in a conservative man-ner compared with the outcomes obtained for the 3D models. This observed absence of conservatism isintrinsic to the 1D approach. To cope with these effects, scaling functions have been determined as a ratiobetween the most conservative radial temperature distribution – computed by fully detailed 3D CFD –and the 1D simplified model. The scaling functions will be applied to the AINA computed wall tempera-ture distribution. To conclude, the determination and coherence of the result obtained using independenttools and approaches, ANSYS®Fluent®vs AINA thermal-hydraulic routines, lead us to recommend theproposed methodology.Research in plasma physics and fusion nuclear technology in the Department of Physics of UPCFutatani, ShimpeiMas de les Valls Ortiz, ElisabetSuárez Cambra, DanielBatet Miracle, Lluíshttp://hdl.handle.net/2117/1791782020-03-05T04:53:13Z2020-03-04T10:56:43ZResearch in plasma physics and fusion nuclear technology in the Department of Physics of UPC
Futatani, Shimpei; Mas de les Valls Ortiz, Elisabet; Suárez Cambra, Daniel; Batet Miracle, Lluís
Advanced Nuclear Technologies (ANT) Research Group of Universitat Politècnica de Catalunya (UPC) has diverse fields of activity; research lines in the field of Nuclear Fusion are summarized in this article. Activities of ANT group in this field encompass from Plasma Physics to Control Engineering, including studies of plasma instabilities, fluid-dynamics and heat and mass transfer analyses; and relate to a variety of subsystems, from the plasma itself to the ancillary systems, including the plasma facing components and the Breeding Blankets. Breeding Blankets are complex components that perform three functions in a fusion reactor: shielding the magnets, recovering the heat produced in the plasma, and producing tritium, which is one of the fuels of fusion. Most of ANT group activities are framed within the EUROFusion program (www.euro-fusion.org), in close collaboration with existing experimental fusion devices and with ITER, the large international R&D fusion project (www.iter.org)
2020-03-04T10:56:43ZFutatani, ShimpeiMas de les Valls Ortiz, ElisabetSuárez Cambra, DanielBatet Miracle, LluísAdvanced Nuclear Technologies (ANT) Research Group of Universitat Politècnica de Catalunya (UPC) has diverse fields of activity; research lines in the field of Nuclear Fusion are summarized in this article. Activities of ANT group in this field encompass from Plasma Physics to Control Engineering, including studies of plasma instabilities, fluid-dynamics and heat and mass transfer analyses; and relate to a variety of subsystems, from the plasma itself to the ancillary systems, including the plasma facing components and the Breeding Blankets. Breeding Blankets are complex components that perform three functions in a fusion reactor: shielding the magnets, recovering the heat produced in the plasma, and producing tritium, which is one of the fuels of fusion. Most of ANT group activities are framed within the EUROFusion program (www.euro-fusion.org), in close collaboration with existing experimental fusion devices and with ITER, the large international R&D fusion project (www.iter.org)RaDoM2: an improved radon dosimeterRomano, StefanoCaresana, M.Curioni, A.Silari, Marcohttp://hdl.handle.net/2117/1775222020-05-07T11:55:56Z2020-02-12T08:46:50ZRaDoM2: an improved radon dosimeter
Romano, Stefano; Caresana, M.; Curioni, A.; Silari, Marco
A new dosimeter for radon progeny called RaDoM (Radon Dose Monitor) was recently developed at CERN . RaDoM is an active detector able to directly estimate the effective dose due to the radon progeny. The first version, which used the Timepix hybrid pixel detector, a system of filters and a pump, correctly assessed the effective dose in situations where the environmental conditions are characterized by a standard equilibrium factor, but showed low efficiency for low radon concentrations and in clean air environments. In this improved version, RaDoM2, the Timepix has been replaced by a silicon pin diode. This solution has allowed the optimization of the geometry, the pump flow rate and the associated electronics, improving the performance of RaDoM and substantially reducing its manufacturing costs. This paper describes the RaDoM2, its improved performance compared to RaDoM, the cloud and user interface, tests in a radon chamber and on-the-field measurements
2020-02-12T08:46:50ZRomano, StefanoCaresana, M.Curioni, A.Silari, MarcoA new dosimeter for radon progeny called RaDoM (Radon Dose Monitor) was recently developed at CERN . RaDoM is an active detector able to directly estimate the effective dose due to the radon progeny. The first version, which used the Timepix hybrid pixel detector, a system of filters and a pump, correctly assessed the effective dose in situations where the environmental conditions are characterized by a standard equilibrium factor, but showed low efficiency for low radon concentrations and in clean air environments. In this improved version, RaDoM2, the Timepix has been replaced by a silicon pin diode. This solution has allowed the optimization of the geometry, the pump flow rate and the associated electronics, improving the performance of RaDoM and substantially reducing its manufacturing costs. This paper describes the RaDoM2, its improved performance compared to RaDoM, the cloud and user interface, tests in a radon chamber and on-the-field measurementsOn the scaling of uncertainties in thermal hydraulic system codesCasamor Vidal, MaxMartínez Quiroga, Víctor ManuelReventós Puigjaner, Francesc JosepMendizabal Sanz, RafaelFreixa Terradas, Jordihttp://hdl.handle.net/2117/1754702020-05-07T11:44:39Z2020-01-22T18:49:53ZOn the scaling of uncertainties in thermal hydraulic system codes
Casamor Vidal, Max; Martínez Quiroga, Víctor Manuel; Reventós Puigjaner, Francesc Josep; Mendizabal Sanz, Rafael; Freixa Terradas, Jordi
The present work addresses the scaling e ect on safety margins and uncertainties for best estimate plus uncertainty (BEPU) methodologies. The results of an experiment from the OECD/NEA ROSA-2 project at the LSTF facility have been used. LSTF is a mock-up of a PWR reactor which follows a power-to-volume scaling approach. A validated RELAP5 model of the experiment has been upscaled to two di erent scales in order to assess the impact of the di erent uncertainty parameters. This process followed the scaling-up methodology (SCUP) developed at UPC. The comparison of the three calculations at di erent scales is presented as well as an uncertainty quantification following the GRS methodology for propagating uncertainties. The comparison of the propagation of the uncertainties at di erent scales has shown that the influence of the scale on the input parameters is negligible. On the other hand, the safety margins are slightly influenced by the scale of the reactor.
2020-01-22T18:49:53ZCasamor Vidal, MaxMartínez Quiroga, Víctor ManuelReventós Puigjaner, Francesc JosepMendizabal Sanz, RafaelFreixa Terradas, JordiThe present work addresses the scaling e ect on safety margins and uncertainties for best estimate plus uncertainty (BEPU) methodologies. The results of an experiment from the OECD/NEA ROSA-2 project at the LSTF facility have been used. LSTF is a mock-up of a PWR reactor which follows a power-to-volume scaling approach. A validated RELAP5 model of the experiment has been upscaled to two di erent scales in order to assess the impact of the di erent uncertainty parameters. This process followed the scaling-up methodology (SCUP) developed at UPC. The comparison of the three calculations at di erent scales is presented as well as an uncertainty quantification following the GRS methodology for propagating uncertainties. The comparison of the propagation of the uncertainties at di erent scales has shown that the influence of the scale on the input parameters is negligible. On the other hand, the safety margins are slightly influenced by the scale of the reactor.Measurement of the 235U(n, f) cross section relative to the 6Li(n, t) and 10B(n, a) standards from thermal to 170 keV neutron energy range at n_TOFAmaducci, SimoneCosentino, LuigiBarbagallo, MassimoCasanovas Hoste, AdriàCalviño Tavares, FranciscoCortés Rossell, Guillem PereTarifeño Saldivia, Ariel Estebanhttp://hdl.handle.net/2117/1745672020-05-07T12:07:09Z2020-01-10T10:28:55ZMeasurement of the 235U(n, f) cross section relative to the 6Li(n, t) and 10B(n, a) standards from thermal to 170 keV neutron energy range at n_TOF
Amaducci, Simone; Cosentino, Luigi; Barbagallo, Massimo; Casanovas Hoste, Adrià; Calviño Tavares, Francisco; Cortés Rossell, Guillem Pere; Tarifeño Saldivia, Ariel Esteban
The 235U(n, f ) cross section was measured at n_TOF relative to 6Li(n, t) and 10B(n,a) , with high resolution ( L=183.49(2) m) and in a wide energy range (25meV-170keV) with 1.5% systematic uncertainty, making use of a stack of six samples and six silicon detectors placed in the neutron beam. This allowed us to make a direct comparison of the yields of the 235U(n, f ) and of the two reference reactions under the same experimental conditions, and taking into account the forward/backward emission asymmetry. A hint of an anomaly in the 10-30keV neutron energy range had been previously observed in other experiments, indicating a cross section systematically lower by several percent relative to major evaluations. The present results indicate that the cross section in the 9-18keV neutron energy range is indeed overestimated by almost 5% in the recently released evaluated data files ENDF/B-VIII.0 and JEFF3.3, as a consequence of a 7% overestimate in a single GMA node in the IAEA reference file. Furthermore, these new high-resolution data confirm the existence of resonance-like structures in the keV neutron energy region. The results here reported may lead to a reduction of the uncertainty in the 1-100keV neutron energy region. Finally, from the present data, a value of 249.7±1.4(stat)±0.94(syst) b·eV has been extracted for the cross section integral between 7.8 and 11eV, confirming the value of 247.5±3 b·eV recently established as a standard.
2020-01-10T10:28:55ZAmaducci, SimoneCosentino, LuigiBarbagallo, MassimoCasanovas Hoste, AdriàCalviño Tavares, FranciscoCortés Rossell, Guillem PereTarifeño Saldivia, Ariel EstebanThe 235U(n, f ) cross section was measured at n_TOF relative to 6Li(n, t) and 10B(n,a) , with high resolution ( L=183.49(2) m) and in a wide energy range (25meV-170keV) with 1.5% systematic uncertainty, making use of a stack of six samples and six silicon detectors placed in the neutron beam. This allowed us to make a direct comparison of the yields of the 235U(n, f ) and of the two reference reactions under the same experimental conditions, and taking into account the forward/backward emission asymmetry. A hint of an anomaly in the 10-30keV neutron energy range had been previously observed in other experiments, indicating a cross section systematically lower by several percent relative to major evaluations. The present results indicate that the cross section in the 9-18keV neutron energy range is indeed overestimated by almost 5% in the recently released evaluated data files ENDF/B-VIII.0 and JEFF3.3, as a consequence of a 7% overestimate in a single GMA node in the IAEA reference file. Furthermore, these new high-resolution data confirm the existence of resonance-like structures in the keV neutron energy region. The results here reported may lead to a reduction of the uncertainty in the 1-100keV neutron energy region. Finally, from the present data, a value of 249.7±1.4(stat)±0.94(syst) b·eV has been extracted for the cross section integral between 7.8 and 11eV, confirming the value of 247.5±3 b·eV recently established as a standard.Cross section measurements of 155,157Gd(n,gamma) induced by thermal and epithermal neutronsMastromarco, M.Aberle, O.Calviño Tavares, FranciscoCasanovas Hoste, AdriàCortés Rossell, Guillem PereTarifeño Saldivia, Ariel Estebanhttp://hdl.handle.net/2117/1653992020-05-07T12:07:09Z2019-07-02T07:43:33ZCross section measurements of 155,157Gd(n,gamma) induced by thermal and epithermal neutrons
Mastromarco, M.; Aberle, O.; Calviño Tavares, Francisco; Casanovas Hoste, Adrià; Cortés Rossell, Guillem Pere; Tarifeño Saldivia, Ariel Esteban
Neutron capture cross section measurements on 155Gd and 157Gd were performed using the time-of-flight technique at the n_TOF facility at CERN on isotopically enriched samples. The measurements were carried out in the n_TOF experimental area EAR1, at 185 m from the neutron source, with an array of 4 C6D6 liquid scintillation detectors. At a neutron kinetic energy of 0.0253 eV, capture cross sections of 62.2(2.2) and 239.8(8.4) kilobarn have been derived for 155Gd and 157Gd, respectively, with up to 6% deviation relative to values presently reported in nuclear data libraries, but consistent with those values within 1.6 standard deviations. A resonance shape analysis has been performed in the resolved resonance region up to 181 eV and 307 eV, respectively for 155Gd and 157Gd, where on average, resonance parameters have been found in good agreement with evaluations. Above these energies and up to 1 keV, the observed resonance-like structure of the cross section has been analysed and characterised. From a statistical analysis of the observed neutron resonances we deduced: neutron strength function of 2.01(28)×10-4 and 2.17(41)×10-4; average total radiative width of 106.8(14) meV and 101.1(20) meV and s-wave resonance spacing 1.6(2) eV and 4.8(5) eV for n + 155Gd and n + 157Gd systems, respectively.
2019-07-02T07:43:33ZMastromarco, M.Aberle, O.Calviño Tavares, FranciscoCasanovas Hoste, AdriàCortés Rossell, Guillem PereTarifeño Saldivia, Ariel EstebanNeutron capture cross section measurements on 155Gd and 157Gd were performed using the time-of-flight technique at the n_TOF facility at CERN on isotopically enriched samples. The measurements were carried out in the n_TOF experimental area EAR1, at 185 m from the neutron source, with an array of 4 C6D6 liquid scintillation detectors. At a neutron kinetic energy of 0.0253 eV, capture cross sections of 62.2(2.2) and 239.8(8.4) kilobarn have been derived for 155Gd and 157Gd, respectively, with up to 6% deviation relative to values presently reported in nuclear data libraries, but consistent with those values within 1.6 standard deviations. A resonance shape analysis has been performed in the resolved resonance region up to 181 eV and 307 eV, respectively for 155Gd and 157Gd, where on average, resonance parameters have been found in good agreement with evaluations. Above these energies and up to 1 keV, the observed resonance-like structure of the cross section has been analysed and characterised. From a statistical analysis of the observed neutron resonances we deduced: neutron strength function of 2.01(28)×10-4 and 2.17(41)×10-4; average total radiative width of 106.8(14) meV and 101.1(20) meV and s-wave resonance spacing 1.6(2) eV and 4.8(5) eV for n + 155Gd and n + 157Gd systems, respectively.