The indoor radon ((222)Rn) activity concentration was measured between January and June in the sc... more The indoor radon ((222)Rn) activity concentration was measured between January and June in the schools of two geothermal areas in Tuscany, central Italy. One of these areas (the Larderello area) is characterized by a large number of geothermal power plants, covering about 9% of the world's geothermal power production. In contrast, the other area, Monte Pisano, has not any such facilities. About 250 measurements were made using track etch detectors. Only a slight difference in the concentrations between the two major sampling areas (98 Bq m(-3) for Larderello area and 43 Bq m(-3) for Monte Pisano area) was found, and this was related to different geological characteristics of the ground and not the presence of the geothermal plants. The measured radon concentrations were always well below the intervention levels in both areas, and health risks for students and personnel in the examined schools were excluded.
h i g h l i g h t s < Technological aspects and design of 3 He neutron proportional counters are ... more h i g h l i g h t s < Technological aspects and design of 3 He neutron proportional counters are reviewed. < Pulse height distribution of the counters were simulated by Monte Carlo code. < Some laboratory developed 3 He-based proportional counter prototypes are described. < A set of gas composition fillings were experimentally investigated.
A B S T R A C T Important challenges for fusion technology deal with the design of safety systems... more A B S T R A C T Important challenges for fusion technology deal with the design of safety systems aimed to protect the Vacuum Vessel (VV) from pressurizing accidents like the Loss Of Coolant Accident (LOCA). To prevent or mitigate structural damages, the solution proposed is a safety system able to quickly condense released steam in cold water at sub-atmospheric conditions. This water suppression tank (VVPSS) is so aiming at limiting the maximum pressure in the VV to 0.2 MPa during in-vessel coolant leak events and at maintaining the VV long-term pressure below atmospheric pressure during air or incondensable gases ingress, through the Direct Contact Condensation (DCC). The novelty of this study resides especially in the working condition of VVPSS, which operates precisely to sub-atmospheric pressure: up to date no explicit experimental data or investigation of DCC are in fact available in literature. To overcome this lack an extensive experimental work has been done at DICI – University of Pisa, where numerous condensation tests (more than 300) were performed. The operation condition investigated took into account downstream pressure between 30 and 117 kPa and water pool temperature from 30 up to 85 °C. The experimental measurements allow to study the influence of steam mass flux, water temperature and pool pressure on the steam condensation phenomenon (and in turn, based on the stable condensation regime, correctly analyze the design parameter of VVPSS). The results obtained are presented and discussed. Innovative condensation regime maps are in addition provided.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1996
The gas amplification properties have been investigated in four types of helium-isobutane gas mix... more The gas amplification properties have been investigated in four types of helium-isobutane gas mixtures consisting of 0.95, 2, 4 and 10% admixture of isobutane. Diethom, Zastawny and Charles gas gain formulae were examined in a wide gain range and the relevant gas constants have been experimentally determined. A slight preference is accorded to the Zastawny formula which is found more flexible in describing the experimental gas gain data. Finally, a simple interpretation of the effect of isobutane percentage in the mixtures on the values of Diethom gas constants is also presented.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1999
Using the microscopic de"nition of the Townsend coe$cient and based on theoretical considerations... more Using the microscopic de"nition of the Townsend coe$cient and based on theoretical considerations related to the physical behaviour of electrons in gases in conjunction with a set of empirical results, a semi-microscopic formula of /N, the "rst Townsend coe$cient to gas density ratio, is developed in the form /N"KS exp[!(S /S)>K], where S"E/N is the electric "eld strength to gas density ratio, and K, S and m (04m41) characterize the gaseous medium. It is shown that when m"0 the /N formula reduces to the product of the analytical forms suggested by Diethorn as well as Williams and Sara. Moreover, it is shown that Diethorn and Zastawny formulae are simply deduced, respectively, as the "rst-and the second-order expansions of the combined formula. Applicability of the obtained gas gain formula for di!erent sets of experimental gas gain data bring out a good consistency of the proposed gas ampli"cation model. (D. Mazed).
Based on theoretical considerations related to the microscopic behaviour of electrons in gases in... more Based on theoretical considerations related to the microscopic behaviour of electrons in gases in conjunction with a macroscopic hypothesis, a semi-microscopic gas gain formula for conventional proportional counters has been already developed and was afterwards successfully tested on gas gain data obtained in Ar-CH 4 -and He-isobutane-filled proportional counters, using an X-ray radiation source. In the present work, it is verified that the semi-microscopic formula works as well in case of the detection of spread energy-spectrum of ionizing charged particles, such as involved within boron lined proportional counters, commonly used for thermal neutron detection. Indeed, we investigate experimentally the validity of the formula for the parameterization of the gas amplification factor data obtained in two boron lined proportional counters, filled with Ar-CH 4 (10%) and Ar-CO 2 (5%). The obtained results show clearly the ability of the gas gain formula to perfectly describe gas gain characteristics in such counters independently of the filling gas mixture used. Consequently, this provides further evidence of generality of the underlying gas amplification semi-microscopic model.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2007
A new active method for continuous airborne radon activity concentration measurements is develope... more A new active method for continuous airborne radon activity concentration measurements is developed. It is based upon the use of a specially designed radon Multiple Cell Proportional Counter (MCPC). The constructed MCPC prototype is described and its operation principle presented. This gas-flow counter is a pile-up of 20 adjacent multiwire proportional counters. It uses argon-propane (1%) as the main counting gas mixture to which an appropriate fraction of ambient air is admixed. The airborne radon activity concentration is to be continuously measured through a periodic integral counting of the a particles emitted by 222 Rn and its short-lived decay products within the sensitive volume. A Monte Carlo simulation program, taking into account the major physical processes that determine directly the detector performances, has been written and used for design optimization purposes. The simulation results show that the admixture of 10% of ambient air seems to be sufficient to continuously assess radon activity concentration levels ranging from about 15 Bq m À3 up to 2.6 Â 10 5 k Bq m À3 for an integral counting time period of 10 min. The expected radon sensitivity is about 1.16 cpm/10 Bq m À3 with a radon counting efficiency of about 180%. The detector a-pulse height spectra obtained by simulation show a very good agreement with those delivered by the constructed MCPC prototype in its minimal configuration. r
A new proportional counter model, baptized Multiple Cell Proportional Counter (MCPC), intended fo... more A new proportional counter model, baptized Multiple Cell Proportional Counter (MCPC), intended for continuous airborne radon activity concentration measurements is described and its operation principle presented. This gas-flow proportional counter, consisting in a pile-up of 20 separate proportional counters elements, uses an argon-propane (1%) as a binary gas mixture to which is admixed an appropriate fraction of ambient air, in
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2005
Aiming for the development of a new technique of on-line airborne radon activity concentration me... more Aiming for the development of a new technique of on-line airborne radon activity concentration measurement, the effect of air on some detection properties of argon-propane (1%)-based proportional counters is investigated when a fraction of 2%, 6% and 10% of it is successively and intentionally admixed to the counting gas in a single-wire proportional counter. The influence of the electron attachment, principally due to oxygen component, on the ionization saturation plateau and the gas amplification process is particularly examined. The previously developed semimicroscopic gas gain formula is found to describe well the gas gain data obtained in each of the gas mixtures analyzed, thus allowing a consistent examination of the air effect on the relevant gas constants. Finally, the possibility to use such air-mixed counting gases in specially designed gas-flow proportional counters intended for new on-line measurement methods of airborne radon ( 222 Rn) activity concentration appeared quite viable. r
The indoor radon ((222)Rn) activity concentration was measured between January and June in the sc... more The indoor radon ((222)Rn) activity concentration was measured between January and June in the schools of two geothermal areas in Tuscany, central Italy. One of these areas (the Larderello area) is characterized by a large number of geothermal power plants, covering about 9% of the world's geothermal power production. In contrast, the other area, Monte Pisano, has not any such facilities. About 250 measurements were made using track etch detectors. Only a slight difference in the concentrations between the two major sampling areas (98 Bq m(-3) for Larderello area and 43 Bq m(-3) for Monte Pisano area) was found, and this was related to different geological characteristics of the ground and not the presence of the geothermal plants. The measured radon concentrations were always well below the intervention levels in both areas, and health risks for students and personnel in the examined schools were excluded.
h i g h l i g h t s < Technological aspects and design of 3 He neutron proportional counters are ... more h i g h l i g h t s < Technological aspects and design of 3 He neutron proportional counters are reviewed. < Pulse height distribution of the counters were simulated by Monte Carlo code. < Some laboratory developed 3 He-based proportional counter prototypes are described. < A set of gas composition fillings were experimentally investigated.
A B S T R A C T Important challenges for fusion technology deal with the design of safety systems... more A B S T R A C T Important challenges for fusion technology deal with the design of safety systems aimed to protect the Vacuum Vessel (VV) from pressurizing accidents like the Loss Of Coolant Accident (LOCA). To prevent or mitigate structural damages, the solution proposed is a safety system able to quickly condense released steam in cold water at sub-atmospheric conditions. This water suppression tank (VVPSS) is so aiming at limiting the maximum pressure in the VV to 0.2 MPa during in-vessel coolant leak events and at maintaining the VV long-term pressure below atmospheric pressure during air or incondensable gases ingress, through the Direct Contact Condensation (DCC). The novelty of this study resides especially in the working condition of VVPSS, which operates precisely to sub-atmospheric pressure: up to date no explicit experimental data or investigation of DCC are in fact available in literature. To overcome this lack an extensive experimental work has been done at DICI – University of Pisa, where numerous condensation tests (more than 300) were performed. The operation condition investigated took into account downstream pressure between 30 and 117 kPa and water pool temperature from 30 up to 85 °C. The experimental measurements allow to study the influence of steam mass flux, water temperature and pool pressure on the steam condensation phenomenon (and in turn, based on the stable condensation regime, correctly analyze the design parameter of VVPSS). The results obtained are presented and discussed. Innovative condensation regime maps are in addition provided.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1996
The gas amplification properties have been investigated in four types of helium-isobutane gas mix... more The gas amplification properties have been investigated in four types of helium-isobutane gas mixtures consisting of 0.95, 2, 4 and 10% admixture of isobutane. Diethom, Zastawny and Charles gas gain formulae were examined in a wide gain range and the relevant gas constants have been experimentally determined. A slight preference is accorded to the Zastawny formula which is found more flexible in describing the experimental gas gain data. Finally, a simple interpretation of the effect of isobutane percentage in the mixtures on the values of Diethom gas constants is also presented.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1999
Using the microscopic de"nition of the Townsend coe$cient and based on theoretical considerations... more Using the microscopic de"nition of the Townsend coe$cient and based on theoretical considerations related to the physical behaviour of electrons in gases in conjunction with a set of empirical results, a semi-microscopic formula of /N, the "rst Townsend coe$cient to gas density ratio, is developed in the form /N"KS exp[!(S /S)>K], where S"E/N is the electric "eld strength to gas density ratio, and K, S and m (04m41) characterize the gaseous medium. It is shown that when m"0 the /N formula reduces to the product of the analytical forms suggested by Diethorn as well as Williams and Sara. Moreover, it is shown that Diethorn and Zastawny formulae are simply deduced, respectively, as the "rst-and the second-order expansions of the combined formula. Applicability of the obtained gas gain formula for di!erent sets of experimental gas gain data bring out a good consistency of the proposed gas ampli"cation model. (D. Mazed).
Based on theoretical considerations related to the microscopic behaviour of electrons in gases in... more Based on theoretical considerations related to the microscopic behaviour of electrons in gases in conjunction with a macroscopic hypothesis, a semi-microscopic gas gain formula for conventional proportional counters has been already developed and was afterwards successfully tested on gas gain data obtained in Ar-CH 4 -and He-isobutane-filled proportional counters, using an X-ray radiation source. In the present work, it is verified that the semi-microscopic formula works as well in case of the detection of spread energy-spectrum of ionizing charged particles, such as involved within boron lined proportional counters, commonly used for thermal neutron detection. Indeed, we investigate experimentally the validity of the formula for the parameterization of the gas amplification factor data obtained in two boron lined proportional counters, filled with Ar-CH 4 (10%) and Ar-CO 2 (5%). The obtained results show clearly the ability of the gas gain formula to perfectly describe gas gain characteristics in such counters independently of the filling gas mixture used. Consequently, this provides further evidence of generality of the underlying gas amplification semi-microscopic model.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2007
A new active method for continuous airborne radon activity concentration measurements is develope... more A new active method for continuous airborne radon activity concentration measurements is developed. It is based upon the use of a specially designed radon Multiple Cell Proportional Counter (MCPC). The constructed MCPC prototype is described and its operation principle presented. This gas-flow counter is a pile-up of 20 adjacent multiwire proportional counters. It uses argon-propane (1%) as the main counting gas mixture to which an appropriate fraction of ambient air is admixed. The airborne radon activity concentration is to be continuously measured through a periodic integral counting of the a particles emitted by 222 Rn and its short-lived decay products within the sensitive volume. A Monte Carlo simulation program, taking into account the major physical processes that determine directly the detector performances, has been written and used for design optimization purposes. The simulation results show that the admixture of 10% of ambient air seems to be sufficient to continuously assess radon activity concentration levels ranging from about 15 Bq m À3 up to 2.6 Â 10 5 k Bq m À3 for an integral counting time period of 10 min. The expected radon sensitivity is about 1.16 cpm/10 Bq m À3 with a radon counting efficiency of about 180%. The detector a-pulse height spectra obtained by simulation show a very good agreement with those delivered by the constructed MCPC prototype in its minimal configuration. r
A new proportional counter model, baptized Multiple Cell Proportional Counter (MCPC), intended fo... more A new proportional counter model, baptized Multiple Cell Proportional Counter (MCPC), intended for continuous airborne radon activity concentration measurements is described and its operation principle presented. This gas-flow proportional counter, consisting in a pile-up of 20 separate proportional counters elements, uses an argon-propane (1%) as a binary gas mixture to which is admixed an appropriate fraction of ambient air, in
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2005
Aiming for the development of a new technique of on-line airborne radon activity concentration me... more Aiming for the development of a new technique of on-line airborne radon activity concentration measurement, the effect of air on some detection properties of argon-propane (1%)-based proportional counters is investigated when a fraction of 2%, 6% and 10% of it is successively and intentionally admixed to the counting gas in a single-wire proportional counter. The influence of the electron attachment, principally due to oxygen component, on the ionization saturation plateau and the gas amplification process is particularly examined. The previously developed semimicroscopic gas gain formula is found to describe well the gas gain data obtained in each of the gas mixtures analyzed, thus allowing a consistent examination of the air effect on the relevant gas constants. Finally, the possibility to use such air-mixed counting gases in specially designed gas-flow proportional counters intended for new on-line measurement methods of airborne radon ( 222 Rn) activity concentration appeared quite viable. r
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Papers by Dahmane Mazed