16 results on '"Senis, Lorenzo"'
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2. Geometrical optimisation of a segmented HPGe detector for spectroscopic gamma emission tomography—A simulation study
- Author
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Rathore, Vikram, Senis, Lorenzo, Andersson Sundén, Erik, Jansson, Peter, Håkansson, Ane, and Andersson, Peter
- Published
- 2021
- Full Text
- View/download PDF
3. First Experimental Demonstration of the Use of a Novel Planar Segmented HPGe Detector for Gamma Emission Tomography of Mockup Fuel Rods.
- Author
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Rathore, Vikram, Senis, Lorenzo, Holm, Stefan Jarl, Sundén, Erik Andersson, Håkansson, Ane, Laassiri, Mounia, Dendooven, Peter, and Andersson, Peter
- Abstract
Postirradiation examination of nuclear fuel is routinely performed to characterize the important properties of current and future fuel. Gamma emission tomography is a proven noninvasive technique for this purpose. Among various measurement elements of the technique, a gamma-ray detector is an important element whose spectroscopic abilities and detection efficiency affect the overall results. Finding a combination of high detection efficiency and excellent energy resolution in a single detector is often a challenge. We have designed a novel planar segmented high-purity germanium detector that offers simultaneous measurement in six lines of sight with excellent energy resolution. The simultaneous detection ability enables faster data acquisition in a tomographic measurement, which may facilitate achieving higher spatial resolution. In this work, we have demonstrated the first use of the detector by performing a full tomographic measurement of mockup fuel rods. Two methods of detector data analysis were used to make spectra, and the images (tomograms) were reconstructed using the filtered back projection algorithm. The reconstructed images validate the successful use of the detector for tomographic measurement. The use of the detector for real fuel measurement is being planned and will be performed in the near future. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
4. Simulation of the response of a segmented high-purity germanium detector for gamma emission tomography of nuclear fuel
- Author
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Andersson, Peter, Rathore, Vikram, Senis, Lorenzo, Anastasiadis, Anastasios, Andersson Sundén, Erik, Atak, Haluk, Holcombe, Scott, Håkansson, Ane, Jansson, Peter, and Nyberg, Johan
- Published
- 2020
- Full Text
- View/download PDF
5. Experimental evaluation of the performance of a novel planar segmented HPGe detector for use in gamma emission tomography
- Author
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Rathore, Vikram, Senis, Lorenzo, Håkansson, Ane, Sundén, Erik A., Andersson, Peter, Rathore, Vikram, Senis, Lorenzo, Håkansson, Ane, Sundén, Erik A., and Andersson, Peter
- Abstract
The use of segmented HPGe detectors for gamma-ray tracking applications is well established. The spectroscopic capabilities of these detectors make them most suitable for such applications. For similar reasons, the use of such detectors in the tomographic measurement of irradiated nuclear fuel has also been envisioned. Especially, these detectors can facilitate faster fuel examination with excellent energy resolution. We have proposed and designed a novel planar segmented HPGe detector for use in gamma emission tomography. The design of the detector segmentation and the mode of operation is unique and offers six simultaneous detection channels for tomographic measurements. This work reports the first experimental evaluation of the performance of the detector. Important characteristics of the detector have been obtained, such as energy resolution of the segments in 1-fold (one segment) and 2-fold (two segments) modes, throughput curves, crosstalk energy corrections, and mislocalisation rate. Collimated source tests have been performed and the results have been compared with the MCNP simulations results. The obtained results are as expected and in good agreement with the simulation results, and it is estimated that using this detector can speed up the data collection by 3.2 times in comparison to an unsegmented detector of the same overall dimensions, in a tomographic application. Further improvements are foreseeable if scaling up to a larger detector with greater segmentation.
- Published
- 2023
- Full Text
- View/download PDF
6. Gamma radiation techniques for non-destructive post-irradiation examination of nuclear fuel : Predicting performance and optimizing instrument design
- Author
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Senis, Lorenzo and Senis, Lorenzo
- Abstract
Collimated gamma-based techniques are widely used to study nuclear fuel, especially for non-destructive post-irradiation examination (PIE). Examples of such techniques include gamma emission tomography (GET) and gamma transmission densitometry (GTD). Further development in designing collimated GET and GTD setups can be foreseen, optimizing the spatial resolution from a millimetre scale to a hundred-micron scale. The enhanced performance would be an asset in PIE, providing a unique combination of high spatial resolution and low interrogation effort. The experimental data would provide a detailed insight into the fuel for modelling its performance at high burnup or in accident scenarios. However, optimizing new instrument designs is not trivial. Multiple performance metrics exist, and their interdependence with the setup configuration and sample characteristics requires evaluation. At the same time, trade-offs should be identified and considered according to the application requirements. Monte Carlo (MC) radiation transport tools are generally unsuitable for modelling such collimated setups due to the intrinsic transmission inefficiency of gammas through the collimator slit. Therefore, alternative methods are desired for evaluating the collimator response. This study proposes a structured optimization methodology, where the trade-offs between the performance metrics are considered to suggest optimal collimator designs for GET applications. The method combines analytical methodologies for fast collimator response calculation and accurate MC simulations to evaluate sample self-attenuation and detector response. The results indicate that for sub-millimetric slits, a few hundred microns resolution can be achieved in suitable conditions (high burnup and short cooling time fuel samples) with reasonable investigation time and noise. Furthermore, the methodologies developed were used to evaluate the feasibility of radial gamma transmission micro-densitometry. Such a tech
- Published
- 2023
7. Performance evaluation of a novel gamma transmission micro-densitometer for PIE of nuclear fuel
- Author
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Senis, Lorenzo, Rathore, Vikram, Andersson, Peter, Johnson, Kyle, Jädernäs, Daniel, Losin, Carolina, Minghetti, Daniele, Wright, Jonathan, Schrire, David, Senis, Lorenzo, Rathore, Vikram, Andersson, Peter, Johnson, Kyle, Jädernäs, Daniel, Losin, Carolina, Minghetti, Daniele, Wright, Jonathan, and Schrire, David
- Abstract
Collimated Gamma Transmission Micro-Densitometry (GTMD) is a novel technique proposed to investigate local density variations of nuclear fuel in PIE, with a high spatial resolution. In this work, the first experimental tests of a gamma micro-densitometer are presented and the performance is characterized. The experimental procedures are described, including the aligning process and the calibration methodology. The results demonstrated that for the calibration samples with a thickness above 5 mm, a local density was obtained with a maximum discrepancy of about 2% and a spatial resolution of about 280 µm. The setup was used for the first test on an irradiated ADOPTTM fuel pellet slice. From the measurement, an average bulk density of about 9.58 g/cm3 was calculated and local density features were observed, possibly related to rim effects or the presence of local cracks. The information acquired also presented valuable information for possible improvements in the setup’s performance.
- Published
- 2023
- Full Text
- View/download PDF
8. First experimental demonstration of the use of a novel planar segmented HPGe detector for gamma emission tomography of mockup fuel rods
- Author
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Rathore, Vikram, Senis, Lorenzo, Holm, Stefan Jarl, Andersson Sundén, Erik, Håkansson, Ane, Laassiri, Mounia, Dendooven, Peter, Andersson, Peter, Rathore, Vikram, Senis, Lorenzo, Holm, Stefan Jarl, Andersson Sundén, Erik, Håkansson, Ane, Laassiri, Mounia, Dendooven, Peter, and Andersson, Peter
- Abstract
Post-irradiation examination of nuclear fuel is routinely performed to characterize the important properties of the current and the future fuel. Gamma emission tomography is a proven non-invasive technique for this purpose. Among various measurement elements of the technique, a gamma-ray detector is an important element whose spectroscopic abilities and detection efficiency affect the overall results. Finding a combination of high detection efficiency and excellent energy resolution in a single detector is often a challenge. We have designed a novel planar segmented HPGe detector which offers simultaneous measurement in six lines of sight with excellent energy resolution. The simultaneous detection ability enables faster data acquisition in a tomographic measurement which may facilitate achieving higher spatial resolution. In this work, we have demonstrated the first use of the detector by performing a full tomographic measurement of mockup fuel rods. Two methods of detector data analysis were used to make spectra and the images (tomograms) were reconstructed using the filtered back projection algorithm. The reconstructed images validate the successful use of the detector for tomographic measurement. The use of the detector for real fuel measurement is being planned and will be performed in the near future., VR Bränslediagnostik - 113330190
- Published
- 2023
- Full Text
- View/download PDF
9. Multi-parameter Optimization of Gamma Emission Tomography Instruments for Irradiated Nuclear Fuel Examination
- Author
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Senis, Lorenzo, Rathore, Vikram, Andersson Sundén, Erik, Elter, Zsolt, Trombetta, Débora Montano, Håkansson, Ane, Andersson, Peter, Senis, Lorenzo, Rathore, Vikram, Andersson Sundén, Erik, Elter, Zsolt, Trombetta, Débora Montano, Håkansson, Ane, and Andersson, Peter
- Abstract
Material test reactors have an extended use in irradiation testing of novel nuclear fuel materials and the fuel behavior in off-normal conditions. The performance of the nuclear fuel is examined in in-pile and out-of-pile post-irradiation examinations (PIEs), e.g., using Gamma Emission Tomography (GET). GET is a nondestructive assay that images the internal spatial distribution of gamma-emitting nuclides built up in the fuel due to irradiation. Since GET can be performed close to the reactor and without intrusion in the fuel object, it can potentially speed up the data generation from PIE in irradiation testing. The performance metrics of GET devices can be identified regarding time requirements, noise in the reconstructed image, signal-to-background ratio, and spatial resolution. However, these are complicated to determine, partly due to inherent trade-offs between the metrics themselves, partly because they depend on the fuel activity and its spectrum (i.e., object dependent), and, finally, on the GET setup and its configuration. This work proposes a structured methodology for optimizing the collimator design for a new generation of GET tomography setups, intending to improve spatial resolution by one order of magnitude: from the millimeter scale to the hundred-micron scale. The conflicting performance metrics are determined based on the controllable parameters of the GET setup and the uncontrollable parameters of an anticipated fuel object, able to provide a signal-to-background ratio above 100. The trade-off between the performance remaining metrics is then visualized by a Pareto approach, where dominated solutions are rejected. Finally, constraints on noise level and measurement time are used to find the optimal spatial resolution. Two GET setups are presented using the outlined method. Firstly, to upgrade the tomography test bench BETTAN at Uppsala University, a new segmented HPGe detector was planned to be tested using low-activity fuel rod mock-ups. Second
- Published
- 2023
- Full Text
- View/download PDF
10. Calculation of Spatial Response of a Collimated Segmented HPGe detector for Gamma Emission Tomography by MCNP Simulations
- Author
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Rathore, Vikram, Senis, Lorenzo, Jansson, Peter, Andersson Sundén, Erik, Håkansson, Ane, Andersson, Peter, Rathore, Vikram, Senis, Lorenzo, Jansson, Peter, Andersson Sundén, Erik, Håkansson, Ane, and Andersson, Peter
- Abstract
We have proposed a planar electronically segmented HPGe detector concept in combination with a multi-slit collimator for gamma emission tomography. In this work, the spatial resolution achievable by using the collimated segmented HPGe detector was evaluated, prior to the manufacture and operation of the detector. The spatial response of a collimated segmented HPGe detector concept was evaluated using simulations performed with Monte Carlo N-Particle transport code MCNP6. The full detector and multi-slit collimator system were modeled and for the quantification of the spatial response, the Modulation Transfer Function (MTF) was chosen as a performance metric. The MTF curve was obtained through the calculation of the Line Spread Function (LSF) by analyzing simulated projection data. In addition, tomographic reconstructions of the simulated simplified test objects were made to demonstrate the performance of the segmented HPGe detector in the planned application. For 662 keV photons, the spatial resolution obtained was approximately the same as the collimator slit width for both 100 and 150 mm long collimators. The corresponding spatial resolution at 1596 keV photon energy was almost twice the slit width for 100 mm collimator, due to the partial penetration of the high-energy gamma rays through the collimator bulk. For a 150 mm long collimator, an improved resolution was obtained., VR Bränslediagnostik
- Published
- 2022
- Full Text
- View/download PDF
11. A computational methodology for estimating the detected energy spectra of the gamma-ray flux from irradiated nuclear fuel
- Author
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Senis, Lorenzo, Elter, Zsolt, Rathore, Vikram, Andersson Sundén, Erik, Jansson, Peter, Holcombe, S., Åberg Lindell, M., Håkansson, Ane, Andersson, Peter, Senis, Lorenzo, Elter, Zsolt, Rathore, Vikram, Andersson Sundén, Erik, Jansson, Peter, Holcombe, S., Åberg Lindell, M., Håkansson, Ane, and Andersson, Peter
- Abstract
Gamma-ray spectrometry using collimated detectors is a well-established examination method for irradiated nuclear fuel. However, the feasibility of examining a particular nuclide of interest is subject to constraints; the peak must be statistically determinable with the desired precision and the total spectrum count rate in the detector should not cause throughput issues. Methods were assembled for gamma spectrum prediction to optimize instruments for gamma emission tomography and to enable a priori feasibility evaluation of determination of single peaks of irradiated nuclear fuel. The aim was to find reliable results (~10% accuracy) regarding total spectrum and peak count rates with faster computation time than a full-Monte Carlo approach. For this purpose, the method is based on depletion calculations with SERPENT2, a point-source kernel method for the collimator response, a rig response matrix and a detector response matrix, both computed with MCNP6. The computational methodology uses as input the fuel properties (dimensions, materials, power history, and cooling time), and the instrumental setup (collimator and detector dimensions and materials). The prediction method was validated using measured data from a high-burnup, short-cooled test fuel rodlet from the Halden reactor. Absolute count rates and ratios of characteristic peaks were compared between predicted and measured spectra, showing a total count rate overestimation of 7% and discrepancies between 2-20% for the single peaks (same order of magnitude of the uncertainty). This level of agreement is deemed sufficient for measurement campaigns planning, and the optimization of spectroscopic instruments for use in gamma scanning and tomography of nuclear fuel.
- Published
- 2022
- Full Text
- View/download PDF
12. Calculation of Spatial Response of a Collimated Segmented HPGe detector for Gamma Emission Tomography by MCNP Simulations
- Author
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Rathore, Vikram, primary, Senis, Lorenzo, additional, Jansson, Peter, additional, Sunden, Erik Andersson, additional, Hakansson, Ane, additional, and Andersson, Peter, additional
- Published
- 2022
- Full Text
- View/download PDF
13. Performance Evaluation of a Novel Gamma Transmission Micro-Densitometer for Pie of Nuclear Fuel
- Author
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Senis, Lorenzo, primary, Rathore, Vikram, additional, Andersson, Peter, additional, Johnson, Kyle, additional, Jädernäs, Daniel, additional, Losin, Carolina, additional, Minghetti, Daniele, additional, Wright, Jonathan, additional, and Schrire, David, additional
- Published
- 2022
- Full Text
- View/download PDF
14. Feasibility study of gamma-ray micro-densitometry for the examination of nuclear fuel swelling
- Author
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Senis, Lorenzo, Rathore, Vikram, Jansson, Peter, Andersson, Peter, Johnson, Kyle, Jädernäs, Daniel, Losin, Carolina, Minghetti, Daniele, and Schrire, David
- Subjects
Subatomär fysik ,Subatomic Physics - Abstract
Nuclear fuel undergoes several thermo-mechanical changes during irradiation in a nuclear reactor, such as change of density, caused by solid and gaseous swelling. This affects the heat transport within the pellet and, when leading to the pellet-cladding gap closure, it also affects the gap conductance, causing stress in the cladding. The density of irradiated fuel pellets can be measured in post-irradiation examination using several methods. In this work, a feasibility study was made using the gamma-ray transmission micro-densitometry technique. This is based on the comparison of two intensity measurements, with and without a sample with well-characterized thickness. Using a collimated source, a local examination of the density can be performed, scanning a pellet slice radially. The proposed technique aims to obtain a spatial resolution of cca. 100 microns. In this work, the parameters of the setup, such as the source activity, detector counting time, slit dimensions, collimator length, and sample thickness, are used to predict detector efficiency and expected count rates. The obtainable precision of the density is assessed by first-order uncertainty propagation of counting errors in the gamma-ray detection to the density estimate. A collimator design was presented that achieves a reasonable compromise between time requirements, precision, and spatial resolution. The sensitivity of the performance to set-up parameters was investigated. In addition, a realistic setup was modeled in MCNP6 for validation of the peak count-rate, and to ensure that the total spectrum count-rate is within typical throughput capabilities of HPGe detectors. The MCNP model was also used to confirm that the assumed attenuation law is valid in a relevant geometry, and to assess the spatial resolution, using the 10-90% edge spread of an Edge Spread Function. It is concluded that fuel density can be determined with
- Published
- 2021
15. Segmented HPGe Detector for Gamma Emission Tomography of Nuclear Fuel and Comparison with Existing Detectors
- Author
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Andersson, Peter, Rathore, Vikram, Senis, Lorenzo, Anastasios, Anastasiadis, Andersson Sundén, Erik, Haluk, Atak, Holcombe, Scott, Håkansson, Ane, Jansson, Peter, Nyberg, Johan, Andersson, Peter, Rathore, Vikram, Senis, Lorenzo, Anastasios, Anastasiadis, Andersson Sundén, Erik, Haluk, Atak, Holcombe, Scott, Håkansson, Ane, Jansson, Peter, and Nyberg, Johan
- Abstract
VR Bränslediagnostik-113 330 190
- Published
- 2019
16. Multi-parameter Optimization of Gamma Emission Tomography Instruments for Irradiated Nuclear Fuel Examination
- Author
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Senis, Lorenzo, Rathore, Vikram, Andersson Sunden, Erik, Elter, Zsolt, Trombetta, Débora Montano, Håkansson, Ane, Andersson, Peter, Senis, Lorenzo, Rathore, Vikram, Andersson Sunden, Erik, Elter, Zsolt, Trombetta, Débora Montano, Håkansson, Ane, and Andersson, Peter
- Abstract
Material test reactors have an extended use in irradiation testing of novel nuclear fuel materials and the fuel behavior in off-normal conditions. The performance of the nuclear fuel is examined in in-pile and out-of-pile post-irradiation examinations (PIEs), e.g., using Gamma Emission Tomography (GET). GET is a nondestructive assay that images the internal spatial distribution of gamma-emitting nuclides built up in the fuel due to irradiation. Since GET can be performed close to the reactor and without intrusion in the fuel object, it can potentially speed up the data generation from PIE in irradiation testing. The performance metrics of GET devices can be identified regarding time requirements, noise in the reconstructed image, signal-to-background ratio, and spatial resolution. However, these are complicated to determine, partly due to inherent trade-offs between the metrics themselves, partly because they depend on the fuel activity and its spectrum (i.e., object dependent), and, finally, on the GET setup and its configuration. This work proposes a structured methodology for optimizing the collimator design for a new generation of GET tomography setups, intending to improve spatial resolution by one order of magnitude: from the millimeter scale to the hundred-micron scale. The conflicting performance metrics are determined based on the controllable parameters of the GET setup and the uncontrollable parameters of an anticipated fuel object, able to provide a signal-to-background ratio above 100. The trade-off between the performance remaining metrics is then visualized by a Pareto approach, where dominated solutions are rejected. Finally, constraints on noise level and measurement time are used to find the optimal spatial resolution. Two GET setups are presented using the outlined method. Firstly, to upgrade the tomography test bench BETTAN at Uppsala University, a new segmented HPGe detector was planned to be tested using low-activity fuel rod mock-ups. Second
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