| 1. |
- Afanaciev, K.G., et al.
(författare)
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Investigation of the radiation hardness of GaAs sensors in an electron beam
- 2012
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 7:11
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Tidskriftsartikel (refereegranskat)abstract
- A compact and finely grained sandwich calorimeter is designed to instrument the very forward region of a detector at a future e+e- collider. The calorimeter will be exposed to low energy e+e - pairs originating from beamstrahlung, resulting in absorbed doses of about one MGy per year. GaAs pad sensors interleaved with tungsten absorber plates are considered as an option for this calorimeter. Several Cr-doped GaAs sensor prototypes were produced and irradiated with 8.5-10 MeV electrons up to a dose of 1.5 MGy. The sensor performance was measured as a function of the absorbed dose.
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| 2. |
- Bernitt Cartemo, Petty, 1984, et al.
(författare)
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Building a generic voxel phantom ofIRINA for Monte Carlo simulations
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The human phantom IRINA, which is widely used for whole body counting calibrations, has been modelled using MATLAB. This document summa-rizes and explains the procedure that was applied for building voxel ver-sions of IRINA in standing position. All 6 sizes in standing positions were successfully modelled with the help of MATLAB and the files are ready to use for any MC simulation. The MC code GATE was used to verify the geometry of the IRINA phantom by comparing the placement of source tubes and scatterers in the Monte Carlo model to the original IRINA docu-mentation. The methodology can easily be used for building voxel phan-toms of IRINA in sitting and bending position, as well as any other geome-try that may be needed.
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| 3. |
- Bernitt Cartemo, Petty, 1984, et al.
(författare)
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Comparison of computational phantoms and investigation of the effect of biodistribution on activity estimations
- 2016
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 171:3, s. 358-364
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Tidskriftsartikel (refereegranskat)abstract
- We have made a comparison between two computational phantoms, modeled from the unified phantom UPh-08T, for whole-body counting applications. One of these was further compared with the ICRP reference adult male computational phantom. The simulations that were performed for the comparison of all three voxel phantoms use various distributions of 60Co. The two voxel phantoms of the UPh-08T showed good agreement, despite different methods of phantom modeling. Also, effects on efficiency of the inhomogeneous distribution of a radionuclide in the computational UPh-08T phantom were studied, using the realistic biodistribution of 140La. Our results show that the activity estimation of radionuclides, which are inhomogeneously distributed in the human body, will be in error if a homogeneous distribution is assumed for the calibration of whole-body counting systems.
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| 4. |
- Bernitt Cartemo, Petty, 1984, et al.
(författare)
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Depth Profiling with the Chalmers Pulsed Positron Beam
- 2014
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Ingår i: International Journal of Nuclear Energy Science and Technology. - 1741-637X .- 1741-6361. ; 8:2, s. 105 - 116
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Tidskriftsartikel (refereegranskat)abstract
- Positron lifetime measurements are used as a tool for obtaining a deeper understanding of positron behaviour in solids and calibrating the Chalmers Pulsed Positron Beam. Experiments are executed for positron energies up to 13 keV corresponding to the maximum penetration depth in Au of roughly 400 nm and measurement results are compared to PENELOPE simulations. Reference towards Makhov modelling is made. The future goal of the study is to investigate the depth dependence of ion-induced radiation damage where positrons will be used to characterise sizes and intensities of vacancy-type lattice defects.
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| 5. |
- Bernitt Cartemo, Petty, 1984
(författare)
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Investigation of Nuclear Materials with Positron Measurements
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Positron Annihilation Lifetime Spectroscopy can be used to characterize radia- tion-induced material defects to subsequently optimize nuclear materials with respect to radiation damage. Nuclear Systems of the future such as Generation IV and fusion concepts demand high performance from structural materials, comprising a material's stability in highly-radiative and hot environments. Analyzing experimental data obtained with the Chalmers Pulsed Positron Beam can help to design material compositions that are able to perform safely under such such conditions.The following work summarizes the efforts made to understand necessary basics of the measurement technique and to validate simulation tools for estimating positron behavior in solid media. A study on positron depth profiling aims at approximating the range positrons travel until annihilation takes place in order to estimate the depth of ion-implanted defects. In the framework of the European collaboration project GETMAT, ions are used to simulate neutron irradiation as expected from reactor conditions in Generation IV Systems. Temporary results from this project are presented and lay base for more detailed information on the evolution of ion-implanted lattice defects.So far it is concluded that the Monte Carlo code PENELOPE is a useful tool for calibrating the Chalmers Pulsed Positron Beam since experimental and simulation data agree well with each other. Early results within GETMAT predict that microscopic material structures are clearly influenced by radiation even though distinct conclusions regarding macroscopic effects are not made yet.
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| 6. |
- Bernitt Cartemo, Petty, 1984
(författare)
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Measurements of Positron Penetration Depth at Low Energies with a Pulsed Beam
- 2010
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Ingår i: IYNC 2010 proceedings.
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Konferensbidrag (refereegranskat)abstract
- Positron lifetime measurements are made with the Chalmers Pulsed Positron Beam with the aim to investigatethe positron penetration depth according to positron energy. The experiments are executed for samples of verythin Au with a thickness of maximum 50 nm. Positron motion inside the material is simulated by PENELOPE-2008and comparisons to Makhov modeling are made. Positron methods are generally used to investigate properties ofdisturbed lattice structures but the following study concentrates mostly on making it possible to create positrondepth profiles in accordance to positron energy
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| 7. |
- Bernitt Cartemo, Petty, 1984
(författare)
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Radiation Detection Techniques for the Enhancement of Nuclear Safety
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The hazard originating from the use of nuclear materials in various areas of the society necessitates a number of experimental techniques for controlling and increasing the safety connected to radioactive substances.The following thesis is divided into two parts, representing different aspects to the detection of radiation effects.The first part aims at investigating radiation-induced material damage of steel alloys that may potentially be used in future Generation IV systems. Concepts like the LFR or SFR will operate under higher temperature and radiation levels than present LWR and detailed knowledge on the material integrity under high level conditions is important for the performance of the major safety barrier and thus the safety of a nuclear power plant. Ion-irradiation is used to simulate neutron-induced damage and the microstructure of the samples is investigated with the help of Positron Annihilation Lifetime Spectroscopy with the Chalmers Pulsed Positron Beam. A study regarding problems and challenges of ion-irradiation experiments is included. Additionally, depth profiling for the calibration of the measurement setup is performed.The second part aims at experimental and computational methods for purposes of Nuclear Safeguards and Emergency Preparedness, respectively. The chapter on safeguards measurements treats two of the major issues within the field, namely spent fuel and nuclear forensics. Firstly, an independent method for investigations of the boron content in a PWR fuel pool is presented, demonstrating how liquid scintillator detectors can be applied for estimations of the relative amount of neutrons absorbed in H and B. Secondly, HPGe measurements on strong Am-sources are performed for a qualitative analysis of inherent impurities to be used as signatures for the identification of unknown sources, helpful to forensic investigations.The chapter on Emergency Preparedness summarizes the computational work that was performed for simulations of source distributions in human phantoms. The IRINA voxel phantom is presented and Monte Carlo simulations for comparisons to the IGOR voxel phantom and the ICRP reference adult male voxel phantom are made for different distributions of Co and La in the human body.
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| 8. |
- Bernitt Cartemo, Petty, 1984, et al.
(författare)
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Sensitivity of the neutronic design of an Accelerator-Driven System (ADS) to the anisotropy of yield of the neutron generator and variation of nuclear data libraries
- 2013
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Ingår i: Proceeding of ESARDA meeting 2013.
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Konferensbidrag (refereegranskat)abstract
- The Accelerator-Driven System concept was chosen to be a basis for the Multi-purpose Hybrid Research Reactor for High-tech Applications (MYRRHA), which can operate in both sub-critical and critical mode. Therefore, the design studies in the scope of this project were varying from accelerator and material aspects to the demonstration of transmutation possibilities of the system. However, the sensitivity of neutron characteristics of the system to the anisotropy of yield of neutron generator and variation of nuclear data libraries may appear to be an important issue.In this study the corresponding sensitivity analysis was performed in order to evaluate the sensitivity of ADS neutronic design to the variation of nuclear data libraries and influence of the anisotropy of the neutron yield of the accelerator.
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| 9. |
- Chernikova, Dina, 1982, et al.
(författare)
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Testing a direct method for evaluating the concentration of boron in a fuel pool using scintillation detectors, and a 252Cf and an 241Am-Be source
- 2013
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Ingår i: Proceeding of ESARDA meeting 2013.
-
Konferensbidrag (refereegranskat)abstract
- The present investigations are aimed at the development and testing of a direct non-destructive method for evaluating the concentration of boron in a fuel pool using scintillation detectors. The method uses a modified ratio between two gamma lines with energy of 480 keV and 2.23 MeV. These lines belong to the capture of a thermal neutron in boron and hydrogen, respectively. The relation between them can reveal the concentration of boron in the fuel pond.The method proposed was tested in a laboratory experiment with a 252Cf and an 241Am-Be source. EJ-309 liquid scintillation detectors were used for measurements of gamma spectra. The concentration of boron in water varied from 1550 ppm to 4200 ppm. The optimization and test studies were performed via MCNPX simulations.The results of these tests are provided in the present paper and they show that the boron content in water can be determined through using the characteristics of gamma lines with energy of 480 keV and 2.23 MeV.
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| 10. |
- Pazsit, Imre, 1948, et al.
(författare)
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Developments in Core-Barrel Motion Monitoring and Applications to the Ringhals PWR Units
- 2016
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Ingår i: Nuclear science and engineering. - : American Nuclear Society. - 0029-5639 .- 1943-748X. ; 182:2, s. 213-227
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Tidskriftsartikel (refereegranskat)abstract
- Core-barrel motion (CBM) surveillance and diagnostics, based on the amplitude of the peaks of the normalized auto power spectral densities (APSDs) of the ex-core neutron detectors, have been performed and continuously developed in Sweden and were applied for monitoring of the three PWR units, Ringhals 2 to 4. From 2005, multiple measurements were taken during each fuel cycle, and these revealed a periodic behavior of the 8-Hz peak of the beam-mode motion: the amplitude increases within the cycle and returns to a lower value at the beginning of the next cycle. The work reported in this paper aims to clarify the physical reason for this behavior. A combination of a mode separation method in the time domain and a nonlinear curve fitting procedure of the frequency spectra revealed that two types of vibration phenomena contribute to the beam-mode peak. The lower frequency peak around 7 Hz in the ex-core detector APSDs corresponds to the CBM, whose amplitude does not change during the cycle. The higher frequency peak around 8 Hz arises from the individual vibrations of the fuel assemblies, and its amplitude increases monotonically during the cycle. This paper gives an account of the work that has been made to veri,b, the above hypothesis.
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