| 1. |
- DiJulio, D. D., et al.
(författare)
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Measurements and Monte-Carlo simulations of the particle self-shielding effect of B4C grains in neutron shielding concrete
- 2018
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Ingår i: Radiation Physics and Chemistry. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0969-806X .- 1879-0895. ; 147, s. 40-44
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Tidskriftsartikel (refereegranskat)abstract
- A combined measurement and Monte-Carlo simulation study was carried out in order to characterize the particle self-shielding effect of B4C grains in neutron shielding concrete. Several batches of a specialized neutron shielding concrete, with varying B4C grain sizes, were exposed to a 2 angstrom neutron beam at the R2D2 test beamline at the Institute for Energy Technology located in Kjeller, Norway. The direct and scattered neutrons were detected with a neutron detector placed behind the concrete blocks and the results were compared to Geant4 simulations. The particle self-shielding effect was included in the Geant4 simulations by calculating effective neutron cross-sections during the Monte-Carlo simulation process. It is shown that this method well reproduces the measured results. Our results show that shielding calculations for low-energy neutrons using such materials would lead to an underestimate of the shielding required for a certain design scenario if the particle self shielding effect is not included in the calculations.
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| 2. |
- Grusell, Erik
(författare)
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On the definition of absorbed dose
- 2015
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 107, s. 131-135
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The quantity absorbed dose is used extensively in all areas concerning the interaction of ionizing radiation with biological organisms, as well as with matter in general. The most recent and authoritative definition of absorbed dose is given by the International Commission on Radiation Units and Measurements (ICRU) in ICRU Report 85. However, that definition is incomplete. The purpose of the present work is to give a rigorous definition of absorbed dose. Methods: Absorbed dose is defined in terms of the random variable specific energy imparted. A random variable is a mathematical function, and it cannot be defined without specifying its domain of definition which is a probability space. This is not done in report 85 by the ICRU, mentioned above. Results: In the present work a definition of a suitable probability space is given, so that a rigorous definition of absorbed dose is possible. This necessarily includes the specification of the experiment which the probability space describes. In this case this is an irradiation, which is specified by the initial particles released and by the material objects which can interact with the radiation. Some consequences are discussed. Specific energy imparted is defined for a volume, and the definition of absorbed dose as a point function involves the specific energy imparted for a small mass contained in a volume surrounding the point. A possible more precise definition of this volume is suggested and discussed. Conclusions: The importance of absorbed dose motivates a proper definition, and one is given in the present work. No rigorous definition has been presented before. (C) 2014 Elsevier Ltd. All rights reserved.
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| 3. |
- Höglund, Carina, et al.
(författare)
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Stability of (B4C)-B-10 thin films under neutron radiation
- 2015
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 113, s. 14-19
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of (B4C)-B-10 have shown to be very suitable as neutron-converting material in the next generation of neutron detectors, replacing the previous predominantly used He-3. In this contribution we show under realistic conditions that (B4C)-B-10 films are not damaged by the neutron irradiation and interactions, which they will be exposed to under many years in a neutron detector. 1 mu m thick (B4C)-B-10 thin films were deposited onto Al or Si substrates using dc magnetron sputtering. As-deposited films were exposed to a cold neutron beam with fluences of up to 1.1 x 10(14) cm(-2) and a mean wavelength of 6.9 angstrom. Both irradiated and as-deposited reference samples were characterized with time-of-flight elastic recoil detection analysis, scanning electron microscopy, transmission electron microscopy, X-ray photoemission spectroscopy, and X-ray diffraction. We show that only 1.8 ppm of the B-10 atoms were consumed and that the film composition does not change by the neutron interaction within the measurement accuracy. The irradiation does not deteriorate the film adhesion and there is no indication that it results in increased residual stress values of the as-deposited films of 0.095 GPa. From what is visible with the naked eye and down to atomic level studies, no change from the irradiation could be found using the above-mentioned characterization techniques. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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| 4. |
- Kholodnaya, Galina, et al.
(författare)
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Pulsed plasma chemical synthesis of carbon-containing titanium and silicon oxide based nanocomposite
- 2018
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Ingår i: Radiation Physics and Chemistry. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0969-806X .- 1879-0895. ; 144, s. 132-137
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents the results of the experimental investigation of the physical and. chemical properties of the TixSiyCzOw composite nanopowders, which were first obtained using a pulsed plasma chemical method. The pulsed plasma chemical synthesis was achieved using a technological electron accelerator (TEA-500). The parameters of the electron beam are as follows: 400-450 keV electron energy, 60 ns half-amplitude pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. The main physical and chemical properties of the obtained composites were studied (morphology, chemical, elemental and phase composition). The morphology of the TixSiyCzOw composites is multiform. There are large round particles, with an average size of above 150 nm. Besides, there are small particles (an average size is in the range of 15-40 nm). The morphology of small particles is in the form of crystallites. In the TixSiyCzOw synthesised composite, the peak with a maximum of 946 cm(-1) was registered. The presence of IR radiation in this region of the spectrum is typical for the deformation of atomic oscillations in the Si-O-Ti bond, which indicates the formation of the solid solution. The composites consist of two crystal phases - anatase and rutile. The prevailing phase of the crystal structure is rutile.
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| 5. |
- Nikjoo, H., et al.
(författare)
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Perspectives in radiation biophysics : From radiation track structure simulation to mechanistic models of DNA damage and repair
- 2016
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 128, s. 3-10
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Tidskriftsartikel (refereegranskat)abstract
- In radiation targeted therapy and genetic risk estimation of low dose radiation protection there is a crucial need for full description of DNA damage response and repair (DDR) leading to cell death and cell mutation. We propose such a description can be arrived through realistic track-structure simulations together with mechanistic mathematical formulation of DDR and the availability of experimental data for testing the proof of principle. In this paper we review briefly first the state of the art in DNA damage and repair, and then the recent advances in the physics of track structure which represents an essential tool in radiation biophysics.
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| 6. |
- Norrfors, K. Karin, et al.
(författare)
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γ-radiation induced corrosion of copper in bentonite-water systems under anaerobic conditions
- 2018
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Ingår i: Radiation Physics and Chemistry. - : Elsevier Ltd. - 0969-806X .- 1879-0895. ; 144, s. 8-12
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Tidskriftsartikel (refereegranskat)abstract
- In this work we have experimentally studied the impact of bentonite clay on the process of radiation-induced copper corrosion in anoxic water. The motivation for this is to further develop our understanding of radiation-driven processes occurring in deep geological repositories for spent nuclear fuel where copper canisters containing the spent nuclear fuel will be embedded in compacted bentonite. Experiments on radiation-induced corrosion in the presence and absence of bentonite were performed along with experiments elucidating the impact irradiation on the Cu2+ adsorption capacity of bentonite. The experiments presented in this work show that the presence of bentonite clay has no or very little effect on the magnitude of radiation-induced corrosion of copper in anoxic aqueous systems. The absence of a protective effect similar to that observed for radiation-induced dissolution of UO2 is attributed to differences in the corrosion mechanism. This provides further support for the previously proposed mechanism where the hydroxyl radical is the key radiolytic oxidant responsible for the corrosion of copper. The radiation effect on the bentonite sorption capacity of Cu2+ (reduced capacity) is in line with what has previously been reported for other cations. The reduced cation sorption capacity is partly attributed to a loss of Al-OH sites upon irradiation.
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| 7. |
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| 8. |
- Pokapanich, Wandared, et al.
(författare)
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Core level photoelectron spectroscopy probed heterogeneous xenon/neon clusters
- 2017
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 135, s. 45-48
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Tidskriftsartikel (refereegranskat)abstract
- Binary rare gas clusters; xenon and neon which have a significant contrariety between sizes, produced by a co-expansion set up and have been studied using synchrotron radiation based x-ray photoelectron spectroscopy. Concentration ratios of the heterogeneous clusters; 1%, 3%, 5% and 10% were controlled. The core level spectra were used to determine structure of the mixed cluster and analyzed by considering screening mechanisms. Furthermore, electron binding energy shift calculations demonstrated cluster aggregation models which may occur in such process. The results showed that in the case of low mixing ratios of 3% and 5% of xenon in neon, the geometric structures exhibit xenon in the center and xenon/neon interfaced in the outer shells. However, neon cluster vanished when the concentration of xenon was increased to 10%.
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| 9. |
- Polito, C., et al.
(författare)
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Dual-modality imaging with a ultrasound-gamma device for oncology
- 2018
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Ingår i: Radiation Physics and Chemistry. - : Elsevier. - 0969-806X .- 1879-0895. ; 147, s. 77-84
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Tidskriftsartikel (refereegranskat)abstract
- Recently, dual-modality systems have been developed, aimed to correlate anatomical and functional information, improving disease localization and helping ontological or surgical treatments.& para;& para;Moreover, due to the growing interest in handheld detectors for preclinical trials or small animal imaging, in this work a new dual modality integrated device, based on a Ultrasounds probe and a small Field of View Single Photon Emission gamma camera, is proposed.
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| 10. |
- Prochazkova, L., et al.
(författare)
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Gamma-radiolytic preparation of multi-component oxides
- 2016
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 1879-0895 .- 0969-806X. ; 124, s. 68-74
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of solid precursors to Zn1-XCdXO and (Lu,Y)(3)Al5O12:Ce induced by Co-60 gamma-ray irradiation of aqueous solutions containing soluble metal salts and ammonium formate is presented: Due to the irradiation, crystalline zinc carbonate hydroxide Zn-4(CO3)(OH)(6). H2O or amorphous carbonates of Lu, Y and Al were formed in the solutions. After calcination at 500 degrees C, the agglomerated phase-pure Zn1-XCdXO with crystallite size about 50 nm was obtained if the Cd concentration in solutions remained below 16 M% (with respect to Zn) with x being up to 0.035. The solid precursors to garnets contained the intended concentration of all elements, according to X-ray fluorescence analysis. After calcination at 1200 degrees C in mild vacuum, the respective phase-pure garnets with crystallite size 100 nm or their solid solution were produced when the Ce dopation was kept below 2 M% (with respect to rare-earth metals). The Ce solubility in the garnet lattice was estimated as 1-2 M% at the calcination conditions used.
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| 11. |
- Sproll, Veronique, et al.
(författare)
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Structure-property correlations of ion-containing polymers for fuel cell applications
- 2016
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 118, s. 120-123
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate the structure-property correlations of grafted proton conducting membranes, the model system consisting of an ETFE base film grafted with polystyrene and subsequent sulfonation (ETFE-g-PSSA) along with crosslinked derivatives ETFE-g-P(SSA-co-DiPB) were synthesized. The characteristics of the final membranes were characterized by PFG-NMR diffusometry, in-plane conductivity and by investigations of the dimensional changes of the grafted membranes. The collected data were correlated with the inherent anisotropy of the ETFE base film. (C) 2015 Elsevier Ltd. All rights reserved.
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| 12. |
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| 13. |
- Toijer, Elin, et al.
(författare)
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H 2 O 2 and γ-radiation induced corrosion of 304L stainless steel in aqueous systems
- 2019
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Ingår i: Radiation Physics and Chemistry. - : Elsevier Ltd. - 0969-806X .- 1879-0895. ; 159, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- In light-water reactors the water used as neutron moderator and coolant is subjected to a constant radiation field which leads to the formation of a number of oxidizing and reducing species. In this work, the reactivity of the radiolysis product H 2 O 2 towards the 304L alloy, commonly used for structural materials in nuclear power plants, was investigated as well as oxidative dissolution of steel components as a consequence of γ-radiation and chemically added H 2 O 2 . The concentration of hydrogen peroxide as a function of time was monitored in the presence of different amounts of steel powder, and the second order reaction rate constant was determined to k 2 = (1.8 ± 0.2) × 10 −10 m s −1 . In the case of catalytic decomposition of hydrogen peroxide, hydroxyl radicals are formed which can be scavenged by methanol. In this reaction formaldehyde is formed, which can be detected spectroscopically. A high yield of formaldehyde was observed, indicating that catalytic decomposition is the main reaction path of H 2 O 2 in the current system. A significant contribution of the homogeneous Fenton reaction to both the reaction rate constant and the formaldehyde formation must however be considered, as Fe(II) will be released from the oxide layer in solution. In the case of γ-irradiation, an increased nickel content in solution compared to background experiments is seen. When the steel is subjected to chemically added hydrogen peroxide on the other hand, the chromium content in solution is increased. This indicates that the different types of exposure will impact different parts of the oxide layer characterized by different composition.
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| 14. |
- Vasilopoulou, T., et al.
(författare)
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Neutron streaming along ducts and labyrinths at the JET biological shielding : Effect of concrete composition
- 2015
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Ingår i: Radiation Physics and Chemistry. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0969-806X .- 1879-0895. ; 116, s. 359-364
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Tidskriftsartikel (refereegranskat)abstract
- Experiments and Monte Carlo simulations were performed at the Joint European Torus (JET) in order to validate the computational tools and methods applied for neutron streaming calculations through penetrations in the JET Hall biological shielding. In the present work the sensitivity of the simulations on the hydrogen and boron content in concrete shielding was investigated. MCNP code was used to simulate neutron streaming along the JET Hall personnel entrance labyrinth for deuterium-deuterium and deuterium-tritium plasma sources for different concrete wall compositions. Neutron fluence and ambient dose equivalent along the labyrinth were calculated. Simulation results for the "as built" JET concrete composition were compared against measurements performed using thermoluminescence detectors. This study contributes to the optimization of the radiation shielding of JET and, furthermore, provides information from JET experience that may assist in optimizing and validating the radiation shielding design methodology used in its successor fusion devices ITER and DEMO.
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| 15. |
- Yang, Miao, et al.
(författare)
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Exploring the limitations of the Hantzsch method used for quantification of hydroxyl radicals in systems of relevance for interfacial radiation chemistry
- 2017
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Ingår i: Radiation Physics and Chemistry. - : Elsevier. - 0969-806X .- 1879-0895. ; 130, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- In the presence of Tris or methanol, hydroxyl radicals in systems of relevance for interfacial radiation chemistry can be quantified indirectly via the Hantzsch method by determining the amount of the scavenging product formaldehyde formed. In this work, the influence of the presence of H2O2 on the Hantzsch method using acetoacetanilide (AAA) as derivatization reagent is studied. The experiments show that the measured CH2O concentration deviates from the actual concentration in the presence of H2O2 and the deviation increases with increasing [H2O2]0/[CH2O]0. The deviation is negative, i.e., the measured formaldehyde concentration is lower than the actual concentration. This leads to an underestimation of the hydroxyl radical production in systems containing significant amount of H2O2. The main reason for the deviation is found to be three coupled equilibria involving H2O2, CH2O and the derivative produced in the Hantzsch method.
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