A study devoted to assessing the neutronic performance of the SORGENTINA-RF fusion neutron source... more A study devoted to assessing the neutronic performance of the SORGENTINA-RF fusion neutron source is here presented. The calculation is performed considering the characteristics of the accelerated mixed deuterium/tritium ion beam from the ion source, the transport of ions into the titanium layer that constitutes the ion beam target, their implantation and the fusion reaction cross section. An investigation has been done by varying the ion composition of the beam in order to assess if and to what extent diatomic and triatomic ion species affect the neutron emission rate of the plant. This calculation is also instrumental to evaluate the cost-effectiveness of equipping the ion source with a filtering system to remove secondary ions from the beam.
The development of a Pd-based membrane reactor to be applied in processes for tritium removal fro... more The development of a Pd-based membrane reactor to be applied in processes for tritium removal from various gaseous streams of tokamak systems has been carried out. In particular, the membrane reactor has been designed for decontaminating soft housekeeping wastes of JET. This membrane reactor consists of Pd-Ag permeator tube fixed in a finger-like mode into a stainless steel shell. The feed stream (gases to be detritiated) is fed inside the membrane lumen where the isotopic exchange takes place on to a catalyst bed while pure hydrogen (protium) is sent in countercurrent mode in the shell side. The feed stream consists of 200 Ncm 3 min −1 of helium with 10% of tritiated water (tritium content 1.11 × 10 8 Bq h −1). The membrane reactor design has been based on a simplified calculation model which takes into consideration the very low tritium content of the gas to be processed and the complete oxidation of the tritiated species in the feed stream. The model considers a tubular Pd-Ag membrane divided into finite elements where the mass balances are performed according to both the thermodynamic equilibrium reactions and permeation rates through the membrane of the hydrogen isotopes. The reactor model has permitted to verify that a Pd-Ag commercial tube of diameter 10 mm, length 500 mm and wall thickness 0.150 mm is capable to attain a decontamination factor larger than 10. A new mechanical design of the Pd membrane reactor has been also developed: especially, harmful mechanical stresses of the long permeator tube consequent to the hydrogenation and thermal cycling has been avoided. Furthermore, an innovative effective heating system of the membrane has been also applied.
In this work, the feasibility of nuclear processes is studied via classical thermodynamics by ass... more In this work, the feasibility of nuclear processes is studied via classical thermodynamics by assessing the change in entropy, a parameter that has so far been neglected in the analysis of these reactions. The contribution of the entropy to the reaction spontaneity plays a different role in the fission and fusion reactions. In particular, in fusion reactions the temperature acts as a very powerful amplifier of the entropic term (−T ΔS) that, at the temperature of tokamaks (millions Kelvin), may significantly reduce the thermodynamic spontaneity of these processes. A new approach is followed for assessing the feasibility of the D-based reactions of interest for the magnetically confined nuclear fusion through the investigation of the effect of the temperature on both kinetics and thermodynamics. The results confirm that the deuterium–tritium reaction is the most promising fusion reaction to be realized in tokamak devices. At the temperature of 1.5 × 108 K (≈13 keV), the DT reaction e...
Eutectic PbeLi (lithium 15.6 at.%) alloy has been tested by means of thermogravimetric analysis u... more Eutectic PbeLi (lithium 15.6 at.%) alloy has been tested by means of thermogravimetric analysis under different hydrogenation conditions in the temperature range 25e650 C. The melting temperature of the material changes irreversibly after the first heating ramp, from that of the eutectic alloy (240 C) to that of pure lead (330 C). The capacity to upload hydrogen depends on the thermal cycling and on the humidity presence. Particularly, it has observed that the presence of water traces in the environment leads to the formation of lithium hydroxide. This reaction affects dramatically the hydrogen uploading of the Pb eLi. Such a behavior is discussed in details by considering the change of weight of the Pb eLi along hydrogenation and thermal cycling.
Journal of Materials Engineering and Performance, 2022
Electrical resistivity of pure titanium has been measured using the electrochemical impedance spe... more Electrical resistivity of pure titanium has been measured using the electrochemical impedance spectroscopy technique under an atmosphere of hydrogen and deuterium at 100 kPa. In both hydrogen and deuterium, the electrical resistivity presents a linear trend with the temperature by exhibiting a different magnitude between the two isotopes. The obtained results are discussed by taking into account the amount of hydrogen and deuterium uploaded into the metal. XRD analysis and TG-DTA measurements have been conducted in the range 25-450 °C: the different behavior of titanium with the two gases has been explained by the different isotopes interactions with the sample surface where titanium oxides are supposed to be present. An evident metal embrittlement has been observed only in the presence of hydrogen.
The SORGENTINA-RF project aims to develop a 14 MeV fusion neutron source to produce medical radio... more The SORGENTINA-RF project aims to develop a 14 MeV fusion neutron source to produce medical radioisotopes with special focus on $$^{99}$$ 99 Mo. The facility is based on a positive ion source with an acceleration stage to produce a deuterium (D$$^{+})$$ + ) and tritium (T$$^{+})$$ + ) ion beam that, impacting on a titanium-coated rotating target, allows fusion reactions to take place. Maximizing the neutron production rate is one of the main issues to be addressed in the project and the optimization of some key parameters of the ion beam is of paramount importance in this regard. In this study, a methodology is discussed to reach a definition of the beam characteristics for an effective and sustainable operation of the plant. The most convenient layout that has been found out is based on a single ion source fed by a deuterium and tritium gas mixture. Eventually, a series of considerations about the operation of the ion source and fuel cycle have been drawn.
Patricia Perez is grateful to Fundacao para a Ciencia e a Tecnologia (FCT) for the doctoral grant... more Patricia Perez is grateful to Fundacao para a Ciencia e a Tecnologia (FCT) for the doctoral grant (reference: SFRH/BD/73673/2010). The authors also acknowledge financing from FCT through the project PTDC / EQU -ERQ/098730/2008.
Abstract: Palladium-based membranes have been widely studied in terms of their use in hydrogen se... more Abstract: Palladium-based membranes have been widely studied in terms of their use in hydrogen separation processes. The high permeability and selectivity of these membranes mean that they are suitable for a variety of applications, although these are limited by the high cost of the precious metal. In order to reduce the cost, several researchers have considered the use of thin metal film membranes, as well as low-cost metals and their alloys, as an alternative to Pd. This chapter focuses on the development of membranes based on metals, such as Ni, Nb, V and Ti, which are promising substitutes for Pd alloys. The main issues related to the synthesis of these membranes and the effect of alloying on their chemical and physical properties are described. Properties relating to hydrogen solubility and permeability, as well as embrittlement under hydrogenation cycling, are also reported. Finally, this chapter discusses ceramic and glass porous membranes. Ceramic porous membranes are examined in terms of their applications as support for new metal alloys, while the use of glass porous membranes in gas separation and in membrane reactors is treated in detail.
Abstract The eutectic Pb-Li alloy is used as liquid breeding blanket material in the concept desi... more Abstract The eutectic Pb-Li alloy is used as liquid breeding blanket material in the concept design of future fusion nuclear reactors where the effective extraction of generated tritium is an important unit operation of the fusion fuel cycle. In this context, the adoption of porous stainless steel tubes working as Membrane Gas-Liquid Contactors (MGLCs) has been proposed for recovering hydrogen isotopes from liquid Pb-Li alloys. Taking into account the results achieved in a previous experimental campaign carried out at 370 °C, the hydrogen mass transfer coefficient has been evaluated and compared with data available in literature. The present study reveals that hydrogen extraction consists of diverse steps, although it is mainly controlled by recombination of hydrogen atoms and their desorption from the gas-liquid interface. The overall permeation exhibits mass transfer resistance values in the range 10−7 – 10-6 m2 s Pa mol-1, while hydrogen transport through the MGLC pores takes place with mass transfer resistances significantly smaller (around 10-4 m2 s Pa mol-1). These results make the use of MGLCs very promising for an effective extraction of tritium from liquid breeders in fusion reactors.
Abstract The pressure-composition absorption isotherms of deuterium in an alloy with nominal comp... more Abstract The pressure-composition absorption isotherms of deuterium in an alloy with nominal composition V85Ni15 were measured between 87 and 400 °C for pressures up to ≈17 bar. For T ≤ 144 °C one observes the occurrence of a solid solution α phase for D/M
Abstract Pd-Ag membranes are well-proven technologies in nuclear fusion fuel cycles especially fo... more Abstract Pd-Ag membranes are well-proven technologies in nuclear fusion fuel cycles especially for what concerns the Q2 (Q = H, D, T) recovery from the tokamak exhaust gas stream. Due to their ability in separating Q2 from other gaseous species, they are also proposed to be implemented in the tritium extraction and recovery system of the DEMO helium cooled pebble bed (HCPB) blanket. Inside the HCPB, the produced tritium is recovered by purging with a large He flow doped with H2 (0.1%wt). Thus the gas stream leaving the blanket will contain a very low Q2 and Q2O concentration diluted in a large amount of He. The paper presents the design and the first experimental results of a new facility, named MeSMeR, erected at ENEA Frascati. The facility hosts a multi-tube module made of 10 Pd-Ag tubes (total surface area of 0.16 m2 and average thickness of 116 μm). The membrane module has been assembled by using a modified tube connection. The aim is to assess the Q2 permeation efficiency of the membrane module under several operating conditions and, particularly, by varying the He/H2 feeding ratio and the total feed flow rate.
Pd-alloy membrane tubes are used for hydrogen isotopes separation in the fusion fuel cycle. The e... more Pd-alloy membrane tubes are used for hydrogen isotopes separation in the fusion fuel cycle. The efficiency of these separation processes has been significantly increased by the adoption of thin-walled self-supported membrane tubes that exhibit high permeance and infinite selectivity to hydrogen. A critical aspect in the realization of Pd-based membrane devices (both separators and membrane reactors) is related to the joining of the thin-walled tubes to the membrane module. In this work, an innovative fitting of thin-walled tubes has been obtained by coupling two special stainless steel joints (a weld adapter and a sealing insert) that tighten the flared edge of the tube. In particular, the design of the compression fitting relies on the elastic deformation reserve of the conical edge of the sealing insert that is capable: i) to ensure the sealing of the joining also in presence of the expansion/contraction of the Pd-Ag alloy during the hydrogenation cycling, and ii) to compensate small irregularities of the thin-walled tube (thickness, circularity, etc.). The effectiveness of the new joining technique in terms of both hydrogen perm-selectivity and stability has been verified in preliminary permeations tests.
As a part of the Broader Approach activities, R&D on blanket related material... more As a part of the Broader Approach activities, R&D on blanket related materials, reduced-activation ferritic martensitic (RAFM) steels as a structural material, SiCf/SiC composites for flow channel insert in the liquid blanket and/or use as advanced structural material, advanced tritium breeders and neutron multiplier, has been initiated directed at DEMO. As part of the RAFM steel mass production development, a 5ton heat of RAFM steel (F82H) was procured by Electro Slag Re-melting as the secondary melting method, which was effective in controlling unwanted impurities. An 11ton heat of EUROFER was also produced. For the SiCf/SiC composite development, NITE- and CVI-SiCf/SiC composites were prepared as reference materials and preliminary mechanical and physical properties were measured. Also compatibility tests between SiC and Pb–17Li have been prepared, related to the He-cooled Li–Pb blanket concept. For the beryllide neutron multiplayer Be–Ti alloy development, large size rods of about 30mm diameter were fabricated successfully in EU.
Palladium-silver thin wall tubes are produced by an innovative procedure based on the diffusion w... more Palladium-silver thin wall tubes are produced by an innovative procedure based on the diffusion welding: these permeators are proposed for separating and producing high-pure hydrogen in both separators and membrane reactors. The reliability of these dense metallic permeators is strongly related to the design configuration of the membrane modules. In fact, as a consequence of hydrogenation and thermal cycles, the dense metallic tubes vary significantly in their length: in case of constraints between the membrane and the module, cyclic axial stresses are applied to the thin wall tube involving the rupture of the permeator. In our applications, a finger-like assembly of the permeator tube has been designed: it permits the free elongation and contraction of the palladium alloy tube avoiding any mechanical stress. In this work, different configurations of palladium membrane reactors used for separating ultra pure hydrogen are described and a study of a membrane process for producing ultra pure hydrogen from ethanol reforming is also presented.
A PdeAg (silver 21 wt.%) thin sheet has been tested in order to measure its electrical resistivit... more A PdeAg (silver 21 wt.%) thin sheet has been tested in order to measure its electrical resistivity by means of electrochemical impedance spectroscopy under different hydrogenation conditions in the temperature range 25e350 C. The metal sheet has been assembled with the electrical contacts in a gas tight module where pure hydrogen has been fed at a pressure of 100 and 200 kPa. The electrical resistivity vs. both the temperature and hydrogen pressure presents a characteristic S-shape curve with a minimum and a maximum of the resistivity. This behaviour permitted to recognize three stages: (1) introduction of H into PdeAg lattice up to a well-defined H/M ratio increases the resistivity; (2) further uptake of hydrogen with a decrease of resistivity until a higher H/M ratio; (3) above this higher H/M ratio the resistivity increases sharply. The behaviour of the electrical resistivity is discussed in details by considering the hydrogen uploading into the metal lattice, its effect on the conduction electrons and the scattering of the hydrogen atoms into the metal lattice.
A study devoted to assessing the neutronic performance of the SORGENTINA-RF fusion neutron source... more A study devoted to assessing the neutronic performance of the SORGENTINA-RF fusion neutron source is here presented. The calculation is performed considering the characteristics of the accelerated mixed deuterium/tritium ion beam from the ion source, the transport of ions into the titanium layer that constitutes the ion beam target, their implantation and the fusion reaction cross section. An investigation has been done by varying the ion composition of the beam in order to assess if and to what extent diatomic and triatomic ion species affect the neutron emission rate of the plant. This calculation is also instrumental to evaluate the cost-effectiveness of equipping the ion source with a filtering system to remove secondary ions from the beam.
The development of a Pd-based membrane reactor to be applied in processes for tritium removal fro... more The development of a Pd-based membrane reactor to be applied in processes for tritium removal from various gaseous streams of tokamak systems has been carried out. In particular, the membrane reactor has been designed for decontaminating soft housekeeping wastes of JET. This membrane reactor consists of Pd-Ag permeator tube fixed in a finger-like mode into a stainless steel shell. The feed stream (gases to be detritiated) is fed inside the membrane lumen where the isotopic exchange takes place on to a catalyst bed while pure hydrogen (protium) is sent in countercurrent mode in the shell side. The feed stream consists of 200 Ncm 3 min −1 of helium with 10% of tritiated water (tritium content 1.11 × 10 8 Bq h −1). The membrane reactor design has been based on a simplified calculation model which takes into consideration the very low tritium content of the gas to be processed and the complete oxidation of the tritiated species in the feed stream. The model considers a tubular Pd-Ag membrane divided into finite elements where the mass balances are performed according to both the thermodynamic equilibrium reactions and permeation rates through the membrane of the hydrogen isotopes. The reactor model has permitted to verify that a Pd-Ag commercial tube of diameter 10 mm, length 500 mm and wall thickness 0.150 mm is capable to attain a decontamination factor larger than 10. A new mechanical design of the Pd membrane reactor has been also developed: especially, harmful mechanical stresses of the long permeator tube consequent to the hydrogenation and thermal cycling has been avoided. Furthermore, an innovative effective heating system of the membrane has been also applied.
In this work, the feasibility of nuclear processes is studied via classical thermodynamics by ass... more In this work, the feasibility of nuclear processes is studied via classical thermodynamics by assessing the change in entropy, a parameter that has so far been neglected in the analysis of these reactions. The contribution of the entropy to the reaction spontaneity plays a different role in the fission and fusion reactions. In particular, in fusion reactions the temperature acts as a very powerful amplifier of the entropic term (−T ΔS) that, at the temperature of tokamaks (millions Kelvin), may significantly reduce the thermodynamic spontaneity of these processes. A new approach is followed for assessing the feasibility of the D-based reactions of interest for the magnetically confined nuclear fusion through the investigation of the effect of the temperature on both kinetics and thermodynamics. The results confirm that the deuterium–tritium reaction is the most promising fusion reaction to be realized in tokamak devices. At the temperature of 1.5 × 108 K (≈13 keV), the DT reaction e...
Eutectic PbeLi (lithium 15.6 at.%) alloy has been tested by means of thermogravimetric analysis u... more Eutectic PbeLi (lithium 15.6 at.%) alloy has been tested by means of thermogravimetric analysis under different hydrogenation conditions in the temperature range 25e650 C. The melting temperature of the material changes irreversibly after the first heating ramp, from that of the eutectic alloy (240 C) to that of pure lead (330 C). The capacity to upload hydrogen depends on the thermal cycling and on the humidity presence. Particularly, it has observed that the presence of water traces in the environment leads to the formation of lithium hydroxide. This reaction affects dramatically the hydrogen uploading of the Pb eLi. Such a behavior is discussed in details by considering the change of weight of the Pb eLi along hydrogenation and thermal cycling.
Journal of Materials Engineering and Performance, 2022
Electrical resistivity of pure titanium has been measured using the electrochemical impedance spe... more Electrical resistivity of pure titanium has been measured using the electrochemical impedance spectroscopy technique under an atmosphere of hydrogen and deuterium at 100 kPa. In both hydrogen and deuterium, the electrical resistivity presents a linear trend with the temperature by exhibiting a different magnitude between the two isotopes. The obtained results are discussed by taking into account the amount of hydrogen and deuterium uploaded into the metal. XRD analysis and TG-DTA measurements have been conducted in the range 25-450 °C: the different behavior of titanium with the two gases has been explained by the different isotopes interactions with the sample surface where titanium oxides are supposed to be present. An evident metal embrittlement has been observed only in the presence of hydrogen.
The SORGENTINA-RF project aims to develop a 14 MeV fusion neutron source to produce medical radio... more The SORGENTINA-RF project aims to develop a 14 MeV fusion neutron source to produce medical radioisotopes with special focus on $$^{99}$$ 99 Mo. The facility is based on a positive ion source with an acceleration stage to produce a deuterium (D$$^{+})$$ + ) and tritium (T$$^{+})$$ + ) ion beam that, impacting on a titanium-coated rotating target, allows fusion reactions to take place. Maximizing the neutron production rate is one of the main issues to be addressed in the project and the optimization of some key parameters of the ion beam is of paramount importance in this regard. In this study, a methodology is discussed to reach a definition of the beam characteristics for an effective and sustainable operation of the plant. The most convenient layout that has been found out is based on a single ion source fed by a deuterium and tritium gas mixture. Eventually, a series of considerations about the operation of the ion source and fuel cycle have been drawn.
Patricia Perez is grateful to Fundacao para a Ciencia e a Tecnologia (FCT) for the doctoral grant... more Patricia Perez is grateful to Fundacao para a Ciencia e a Tecnologia (FCT) for the doctoral grant (reference: SFRH/BD/73673/2010). The authors also acknowledge financing from FCT through the project PTDC / EQU -ERQ/098730/2008.
Abstract: Palladium-based membranes have been widely studied in terms of their use in hydrogen se... more Abstract: Palladium-based membranes have been widely studied in terms of their use in hydrogen separation processes. The high permeability and selectivity of these membranes mean that they are suitable for a variety of applications, although these are limited by the high cost of the precious metal. In order to reduce the cost, several researchers have considered the use of thin metal film membranes, as well as low-cost metals and their alloys, as an alternative to Pd. This chapter focuses on the development of membranes based on metals, such as Ni, Nb, V and Ti, which are promising substitutes for Pd alloys. The main issues related to the synthesis of these membranes and the effect of alloying on their chemical and physical properties are described. Properties relating to hydrogen solubility and permeability, as well as embrittlement under hydrogenation cycling, are also reported. Finally, this chapter discusses ceramic and glass porous membranes. Ceramic porous membranes are examined in terms of their applications as support for new metal alloys, while the use of glass porous membranes in gas separation and in membrane reactors is treated in detail.
Abstract The eutectic Pb-Li alloy is used as liquid breeding blanket material in the concept desi... more Abstract The eutectic Pb-Li alloy is used as liquid breeding blanket material in the concept design of future fusion nuclear reactors where the effective extraction of generated tritium is an important unit operation of the fusion fuel cycle. In this context, the adoption of porous stainless steel tubes working as Membrane Gas-Liquid Contactors (MGLCs) has been proposed for recovering hydrogen isotopes from liquid Pb-Li alloys. Taking into account the results achieved in a previous experimental campaign carried out at 370 °C, the hydrogen mass transfer coefficient has been evaluated and compared with data available in literature. The present study reveals that hydrogen extraction consists of diverse steps, although it is mainly controlled by recombination of hydrogen atoms and their desorption from the gas-liquid interface. The overall permeation exhibits mass transfer resistance values in the range 10−7 – 10-6 m2 s Pa mol-1, while hydrogen transport through the MGLC pores takes place with mass transfer resistances significantly smaller (around 10-4 m2 s Pa mol-1). These results make the use of MGLCs very promising for an effective extraction of tritium from liquid breeders in fusion reactors.
Abstract The pressure-composition absorption isotherms of deuterium in an alloy with nominal comp... more Abstract The pressure-composition absorption isotherms of deuterium in an alloy with nominal composition V85Ni15 were measured between 87 and 400 °C for pressures up to ≈17 bar. For T ≤ 144 °C one observes the occurrence of a solid solution α phase for D/M
Abstract Pd-Ag membranes are well-proven technologies in nuclear fusion fuel cycles especially fo... more Abstract Pd-Ag membranes are well-proven technologies in nuclear fusion fuel cycles especially for what concerns the Q2 (Q = H, D, T) recovery from the tokamak exhaust gas stream. Due to their ability in separating Q2 from other gaseous species, they are also proposed to be implemented in the tritium extraction and recovery system of the DEMO helium cooled pebble bed (HCPB) blanket. Inside the HCPB, the produced tritium is recovered by purging with a large He flow doped with H2 (0.1%wt). Thus the gas stream leaving the blanket will contain a very low Q2 and Q2O concentration diluted in a large amount of He. The paper presents the design and the first experimental results of a new facility, named MeSMeR, erected at ENEA Frascati. The facility hosts a multi-tube module made of 10 Pd-Ag tubes (total surface area of 0.16 m2 and average thickness of 116 μm). The membrane module has been assembled by using a modified tube connection. The aim is to assess the Q2 permeation efficiency of the membrane module under several operating conditions and, particularly, by varying the He/H2 feeding ratio and the total feed flow rate.
Pd-alloy membrane tubes are used for hydrogen isotopes separation in the fusion fuel cycle. The e... more Pd-alloy membrane tubes are used for hydrogen isotopes separation in the fusion fuel cycle. The efficiency of these separation processes has been significantly increased by the adoption of thin-walled self-supported membrane tubes that exhibit high permeance and infinite selectivity to hydrogen. A critical aspect in the realization of Pd-based membrane devices (both separators and membrane reactors) is related to the joining of the thin-walled tubes to the membrane module. In this work, an innovative fitting of thin-walled tubes has been obtained by coupling two special stainless steel joints (a weld adapter and a sealing insert) that tighten the flared edge of the tube. In particular, the design of the compression fitting relies on the elastic deformation reserve of the conical edge of the sealing insert that is capable: i) to ensure the sealing of the joining also in presence of the expansion/contraction of the Pd-Ag alloy during the hydrogenation cycling, and ii) to compensate small irregularities of the thin-walled tube (thickness, circularity, etc.). The effectiveness of the new joining technique in terms of both hydrogen perm-selectivity and stability has been verified in preliminary permeations tests.
As a part of the Broader Approach activities, R&D on blanket related material... more As a part of the Broader Approach activities, R&D on blanket related materials, reduced-activation ferritic martensitic (RAFM) steels as a structural material, SiCf/SiC composites for flow channel insert in the liquid blanket and/or use as advanced structural material, advanced tritium breeders and neutron multiplier, has been initiated directed at DEMO. As part of the RAFM steel mass production development, a 5ton heat of RAFM steel (F82H) was procured by Electro Slag Re-melting as the secondary melting method, which was effective in controlling unwanted impurities. An 11ton heat of EUROFER was also produced. For the SiCf/SiC composite development, NITE- and CVI-SiCf/SiC composites were prepared as reference materials and preliminary mechanical and physical properties were measured. Also compatibility tests between SiC and Pb–17Li have been prepared, related to the He-cooled Li–Pb blanket concept. For the beryllide neutron multiplayer Be–Ti alloy development, large size rods of about 30mm diameter were fabricated successfully in EU.
Palladium-silver thin wall tubes are produced by an innovative procedure based on the diffusion w... more Palladium-silver thin wall tubes are produced by an innovative procedure based on the diffusion welding: these permeators are proposed for separating and producing high-pure hydrogen in both separators and membrane reactors. The reliability of these dense metallic permeators is strongly related to the design configuration of the membrane modules. In fact, as a consequence of hydrogenation and thermal cycles, the dense metallic tubes vary significantly in their length: in case of constraints between the membrane and the module, cyclic axial stresses are applied to the thin wall tube involving the rupture of the permeator. In our applications, a finger-like assembly of the permeator tube has been designed: it permits the free elongation and contraction of the palladium alloy tube avoiding any mechanical stress. In this work, different configurations of palladium membrane reactors used for separating ultra pure hydrogen are described and a study of a membrane process for producing ultra pure hydrogen from ethanol reforming is also presented.
A PdeAg (silver 21 wt.%) thin sheet has been tested in order to measure its electrical resistivit... more A PdeAg (silver 21 wt.%) thin sheet has been tested in order to measure its electrical resistivity by means of electrochemical impedance spectroscopy under different hydrogenation conditions in the temperature range 25e350 C. The metal sheet has been assembled with the electrical contacts in a gas tight module where pure hydrogen has been fed at a pressure of 100 and 200 kPa. The electrical resistivity vs. both the temperature and hydrogen pressure presents a characteristic S-shape curve with a minimum and a maximum of the resistivity. This behaviour permitted to recognize three stages: (1) introduction of H into PdeAg lattice up to a well-defined H/M ratio increases the resistivity; (2) further uptake of hydrogen with a decrease of resistivity until a higher H/M ratio; (3) above this higher H/M ratio the resistivity increases sharply. The behaviour of the electrical resistivity is discussed in details by considering the hydrogen uploading into the metal lattice, its effect on the conduction electrons and the scattering of the hydrogen atoms into the metal lattice.
Uploads
Papers by Silvano Tosti