| 1. |
- Andersson, Peter, 1981-, et al.
(författare)
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Coincidence spectroscopy for increased sensitivity in radionuclide monitoring
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The majority of the energy in a nuclear explosion is released in the immediate blast and the initial radiation accounts. The remaining fraction is released through radioactive decay of the explosion's fission products and neutron activation products over a longer time span. This allows for the detection of a nuclear explosion by detecting the presence of residual decay. Radionuclide monitoring stations for detection of radioactive emissions to the atmosphere is thereby an important tool in the verification of compliance with nuclear disarmament treaties. In particular, the globally spanning radionuclide station network of the International Monitoring System (IMS) has been implemented for verification of the Comprehensive Nuclear-Test-Ban Treaty.High Purity Germanium (HPGe) detectors are workhorses in radionuclide monitoring. The detection of characteristic gamma rays can be used to disclose the presence of signature nuclides produced innuclear weapon tests. A particular development that has potential to improve the sensitivity of radionuclide monitoring is the coincidence technique where decaying nuclides that emit several coincident gamma rays can be detected at much smaller activity concentrations than with conventional gamma spectroscopy.In this project, dedicated gamma-gamma coincidence detectors are being developed, utilizing electronically segmented HPGe detectors. These detectors are expected to be highly sensitive to low-activity samples of nuclides that present coincident emissions of gamma rays. In this paper we present the concept, define performance parameters, and explore the performance of such detectors to a subset of radionuclides of particular CTBT relevance. In addition, we discuss the path forward in developing a next generation gamma-gamma coincidence spectroscopy system of segmented HPGe.
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| 2. |
- Branger, Erik, 1988-, et al.
(författare)
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Combining DCVD measurements at different alignments for enhanced partial defect detection performance
- 2021
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Ingår i: Proceedings of the INMM & ESARDA Joint Virtual Annual Meeting August 23-26 & August 30-September 1, 2021.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the current Digital Cherenkov Viewing Device (DCVD) measurement methodology, the DCVD is aligned over the centre of a fuel assembly when measuring emitted Cherenkov light. Due to the collimation of light, and due to the lifting handle of PWR fuel assemblies covering the fuel periphery, the DCVD is more sensitive to partial defects near the fuel assembly centre than near the periphery. Here, we investigate the sensitivity of the DCVD for detecting partial defects for different instrument alignments. By performing measurements at both the centre and near the assembly periphery, more accurate measurements near the periphery can be obtained.DCVD images were simulated for different partial defect scenarios with 30% of the fuel rods removed or replaced with low, medium or high-density rods. Simulations were run with different DCVD alignments, and the Cherenkov light distribution in the images were quantitatively analysed and compared to simulated images for a fuel assembly without defects. The simulation results were also compared with measurements of intact spent fuel assemblies.The simulations show that the local Cherenkov light intensity deviation due to a partial defect is not sensitive to the alignment. Hence, the current methodology is robust, and will not benefit from measuring at different alignments. Regarding the signal-to-noise ratio, combining measurements at different alignments can improve the measurements. However, the improvement is modest, and for the DCVD it may be preferred to simply use the current methodology and make longer measurements. For future autonomous Cherenkov measuring systems, combining images can be a way of improving the quality of the measurements.
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| 3. |
- Branger, Erik, 1988-, et al.
(författare)
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Comparison of prediction models for Cherenkov light emissions from nuclear fuel assemblies
- 2017
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool used by nuclear safeguards inspectors to verify irradiated nuclear fuel assemblies in wet storage based on the Cherenkov light produced by the assembly. Verification that no rods have been substituted in the fuel, so-called partial-defect verification, is made by comparing the intensity measured with a DCVD with a predicted intensity, based on operator fuel declaration. The prediction model currently used by inspectors is based on simulations of Cherenkov light production in a BWR 8x8 geometry. This work investigates prediction models based on simulated Cherenkov light production in a BWR 8x8 and a PWR 17x17 assembly, as well as a simplified model based on a single rod in water. Cherenkov light caused by both fission product gamma and beta decays were considered.The simulations reveal that there are systematic differences between the models, most noticeably with respect to the fuel assembly cooling time. Consequently, a prediction model that is based on another fuel assembly configuration than the fuel type being measured, will result in systematic over or underestimation of short-cooled fuel as opposed to long-cooled fuel. While a simplified model may be accurate enough for fuel assemblies with fairly homogeneous cooling times, the prediction models may differ by up to 18 \,\% for more heterogeneous fuel. Accordingly, these investigations indicate that the currently used model may need to be exchanged with a set of more detailed, fuel-type specific models, in order minimize the model dependant systematic deviations.
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| 4. |
- Branger, Erik, 1988-, et al.
(författare)
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Effects of modelling assumptions on Cherenkov light intensity predictions
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is one of the instruments available to IAEA inspectors to verify spent nuclear fuel in wet storage. The DCVD can be used for partial defect verification, verifying that 50% or more of a fuel assembly has not been diverted. The partial defect verification relies on a comparison between measured and predicted intensities, based on operator fuel declarations. Recently, IAEA inspectors have encountered spent fuels with short cooling times where there were systematic differences between predictions and measurements. Through the Swedish support program, this deviation was investigated, by studying various modelling assumptions that could cause the discrepancy.The predominant cause of the discrepancy was beta-decay electrons, passing through the fuel cladding and entering the water with sufficient energy to directly produce Cherenkov light. Analysis of measurement data for a set of fuels where the discrepancy was found to be pronounced revealed that for modern fuel designs with thin claddings the beta contribution is enhanced, and for short-cooled fuels additional beta-decaying isotopes are abundant and must be considered. Furthermore, the data showed that for nuclear fuels that had not reached the discharge burnup, the fuel irradiation history may cause a relative enhancement of the abundance of beta-decaying isotopes relative to other isotopes causing Cherenkov light. Other studied modelling assumptions, such as void, burnable absorbers and using binned gamma spectra, showed that they only introduced a modest bias, and proper default values and data handling can mitigate it. A method to predict the direct beta contribution to the Cherenkov light intensity was developed, which can ensure that the observed biases will be eliminated from future verification campaigns. It is advised that this enhanced prediction method be included in the DCVD software, and made available to inspectors.
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| 5. |
- Branger, Erik, 1988-
(författare)
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Enhancing the performance of the Digital Cherenkov Viewing Device : Detecting partial defects in irradiated nuclear fuel assemblies using Cherenkov light
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is an instrument used by authority safeguards inspectors to verify irradiated nuclear fuel assemblies in wet storage based on Cherenkov light emission. It is frequently used to verify that parts of an assembly have not been diverted, which is done by comparing the measured Cherenkov light intensity to a predicted one.This thesis presents work done to further enhance the verification capability of the DCVD, and has focused on developing a second-generation prediction model (2GM), used to predict the Cherenkov light intensity of an assembly. The 2GM was developed to take into account the irradiation history, assembly type and beta decays, while still being usable to an inspector in-field. The 2GM also introduces a method to correct for the Cherenkov light intensity emanating from neighbouring assemblies. Additionally, a method to simulate DCVD images has been seamlessly incorporated into the 2GM.The capabilities of the 2GM has been demonstrated on experimental data. In one verification campaign on fuel assemblies with short cooling time, the first-generation model showed a Root Mean Square error of 15.2% when comparing predictions and measurements. This was reduced by the 2GM to 7.8% and 8.1%, for predictions with and without near-neighbour corrections. A simplified version of the 2GM for single assemblies will be included in the next version of the official DCVD software, which will be available to inspectors shortly. The inclusion of the 2GM allows the DCVD to be used to verify short-cooled assemblies and assemblies with unusual irradiation history, with increased accuracy.Experimental measurements show that there are situations when the intensity contribution due to neighbours is significant, and should be included in the intensity predictions. The image simulation method has been demonstrated to also allow the effect of structural differences in the assemblies to be considered in the predictions, allowing assemblies of different designs to be compared with enhanced accuracy.
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| 6. |
- Branger, Erik, 1988-, et al.
(författare)
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Experimental evaluation of models for predicting Cherenkov light intensities from short-cooled nuclear fuel assemblies
- 2018
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool used by nuclear safeguards inspectors to verify irradiated nuclear fuel assemblies in wet storage based on the recording of Cherenkov light produced by the assemblies. One type of verification involves comparing the measured light intensity from an assembly with a predicted intensity, based on assembly declarations. Crucial for such analyses is the performance of the prediction model used, and recently new modelling methods have been introduced to allow for enhanced prediction capabilities by taking the irradiation history into account, and by including the cross-talk radiation from neighbouring assemblies in the predictions.In this work, the performance of three models for Cherenkov-light intensity prediction is evaluated by applying them to a set of short-cooled PWR 17x17 assemblies for which experimental DCVD measurements and operator-declared irradiation data was available; (1) a two-parameter model, based on total burnup and cooling time, previously used by the safeguards inspectors, (2) a newly introduced gamma-spectrum-based model, which incorporates cycle-wise burnup histories, and (3) the latter gamma-spectrum-based model with the addition to account for contributions from neighbouring assemblies.The results show that the two gamma-spectrum-based models provide significantly higher precision for the measured inventory compared to the two-parameter model, lowering the standard deviation between relative measured and predicted intensities from 15.2% to 8.1% respectively 7.8%.The results show some systematic differences between assemblies of different designs (produced by different manufacturers) in spite of their similar PWR 17x17 geometries, and possible ways are discussed to address such differences, which may allow for even higher prediction capabilities. Still, it is concluded that the gamma-spectrum-based models enable confident verification of the fuel assembly inventory at the currently used detection limit for partial defects, being a 30% discrepancy between measured and predicted intensities, while some false detection occurs with the two-parameter model. The results also indicate that the gamma-spectrum-based prediction methods are accurate enough that the 30% discrepancy limit could potentially be lowered.
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| 7. |
- Branger, Erik, 1988-, et al.
(författare)
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Experimental study of background subtraction in Digital Cherenkov Viewing Device measurements
- 2018
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is an imaging tool used by authority inspectors for partial defect verification of nuclear fuel assemblies in wet storage, i.e. to verify that part of an assembly has not been diverted. One of the currently adopted verification procedures is based on quantitative measurements of the assembly's Cherenkov light emissions, and comparisons to an expected intensity, calculated based on operator declarations. A background subtraction of the intensity data in the recorded images is necessary for accurate quantitative measurements. The currently used background subtraction is aimed at removing an electronics-induced image-wide offset, but it is argued here that the currently adopted procedure may be insufficient.It is recommended that a standard dark-frame subtraction should be used, to remove systematic pixel-wise background due to the electronics, replacing the currently used offset procedure. Experimental analyses show that a dark-frame subtraction would further enhance the accuracy and reliability of DCVD measurements. Furthermore, should ageing of the CCD chip result in larger systematic pixel-wise deviations over time, a dark-frame subtraction can ensure reliable measurements regardless of the age of the CCD chip. It can also help in eliminating any adverse effects of malfunctioning pixels. In addition to the background from electronic noise, ways to compensate for background from neighbouring fuel assemblies and ambient light are also discussed.
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| 8. |
- Branger, Erik, 1988-, et al.
(författare)
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Image analysis to support DCVD verification
- 2023
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Ingår i: Proceedings of the INMM & ESARDA Joint Annual Meeting, May 22-26, 2023. - : Institute of Nuclear Materials Management (INMM).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is one instrument available to authority inspectors for verifying spent fuel assemblies in wet storage. The measurements result in images of the Cherenkov light emissions from the fuel assembly under study. This work presents research on applying image analysis and statistical methods to improve data quality and to extract more information from the measurements, extending the use of these methods beyond what is currently implemented in the DCVD software. The goal of this project is to apply template matching and statistical analysis to the images. However, before such techniques can be applied, effort is needed to ensure that the measurements are directly comparable. Two main issues are investigated here, the first being the positioning of the Region-Of-Interest. By developing an automated Region-Of-Interest placer, a consistent and reproducible Region-Of-Interest placement can be achieved. The second is automatic identification of fuel type, to support a later comparison with a template. We demonstrate that a method based on Principal Component Analysis can be used to determine the fuel type. Finally, we present the first results regarding template matching, comparing a measured image to a template, aiming to identify regions in the image where the two differ. Such differences could be due to a partial defect located in that region, but also due to other reasons such as debris covering the fuel top. Automatically identification of such regions can in the future be used to focus inspector attention to features requiring expert judgement, supporting efficient use of the measurement data and inspector effort. The first results demonstrate the feasibility of the method, but also that more work is required before the method is robust.
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| 9. |
- Branger, Erik, 1988-, et al.
(författare)
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Improved Cherenkov Light Prediction Model for Enhanced DCVD Performance
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is an instrument used to verify irradiated nuclear fuel assemblies in wet storage based on the fuel’s Cherenkov light emissions. The DCVD is frequently used for partial defect verification, verifying that 50% or more of an assembly has not been diverted. The verification methodology is based on comparison of the measured Cherenkov light intensity to a predicted intensity, based on operator declarations.For the last five years, a dedicated PhD project at Uppsala University has been aiming at enhancing and improving the verification capabilities when using the DCVD. The project is now approaching its end, and this paper summarizes the comprehensive work performed regarding improving the prediction capabilities.A new prediction model has been developed, considering more fuel assembly details to ensure more accurate predictions. With the new model, the irradiation history of an assembly, the assembly design and the contributions from gamma and beta decays are taken into account. The model has also been extended to account for the radiation from neighbouring fuel assemblies, which can enter the assembly being measured and contribute to the measured Cherenkov light. The performance of the prediction model and the neighbour intensity prediction model has been validated against fuel measurements by the IAEA at a PWR facility with short-cooled fuel. The results show that the new model offers an improved prediction capability, allowing the fuel inventory to be verified with no fuel assemblies being identified as outliers requiring additional investigation. A simplified version of the prediction model will be implemented in the next DCVD software version, making it available to IAEA inspectors.This development of the DCVD capabilities are in line with the fourth theme of the IAEA safeguards symposium, “Shaping the future of safeguards implementation”, by resolving challenges related to the DCVD and by extending the capabilities of the instrument.
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| 10. |
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| 11. |
- Branger, Erik, 1988-, et al.
(författare)
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Investigating the Cherenkov light production due to cross-talk in closely stored nuclear fuel assemblies in wet storage
- 2018
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Ingår i: ESARDA Bulletin. - : European Commission Joint Research Centre. - 1977-5296. ; :57, s. 66-74
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is one of the tools available to a safeguards inspector performing verifications of irradiated nuclear fuel assemblies in wet storage. One of the main advantages of safeguards verification using Cherenkov light is that it can be performed without moving the fuel assemblies to an isolated measurement position, allowing for quick measurements. One disadvantage of this procedure is that irradiated nuclear fuel assemblies are often stored close to each other, and consequently gamma radiation from one assembly can enter a neighbouring assembly, and produce Cherenkov light in the neighbour. As a result, the measured Cherenkov light intensity of one assembly will include contributions from its neighbours, which may affect the safeguards conclusions drawn.In this paper, this so-called near-neighbour effect, is investigated and quantified through simulation. The simulations show that for two fuel assemblies with similar properties stored closely, the near-neighbour effect can cause a Cherenkov light intensity increase of up to 3% in a measurement. For one fuel assembly surrounded by identical neighbour assemblies, a total of up to 14% of the measured intensity may emanate from the neighbours. The relative contribution from the near-neighbour effect also depends on the fuel properties; for a long-cooled, low-burnup assembly, with low gamma and Cherenkov light emission, surrounded by short-cooled, high-burnup assemblies with high emission, the measured Cherenkov light intensity may be dominated by the contributions from its neighbours.When the DCVD is used for partial-defect verification, a 50% defect must be confidently detected. Previous studies have shown that a 50% defect will reduce the measured Cherenkov light intensity by 30% or more, and thus a threshold has been defined, where a ≥30% decrease in Cherenkov light indicates a partial defect. However, this work shows that the near-neighbour effect may also influence the measured intensity, calling either for a lowering of this threshold or for the intensity contributions from neighbouring assemblies to be corrected for. In this work, a method is proposed for assessing the near-neighbour effect based on declared fuel parameters, enabling the latter type of corrections.
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| 12. |
- Branger, Erik, 1988-, et al.
(författare)
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Investigating the sensitivity to irradiation history when predicting fuel parameters using random forest regression
- 2021
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Ingår i: ESARDA Bulletin. - : European Commission Joint Research Centre. - 1977-5296. ; 62, s. 2-10
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Tidskriftsartikel (refereegranskat)abstract
- Safeguards verification of spent nuclear fuel assemblies is frequently done by performing non-destructive measurements, which are used to verify the completeness and correctness of operator declarations such as initial enrichment (IE), burnup (BU) and cooling time (CT) of the fuel. However, different irradiation histories may result in the same combination of CT, BU and IE, and such fuels may behave differently despite identically declared values. The goal of this work is to investigate what effect the irradiation history has on the ability to predict the fuel parameters using random forest regression. Random forest regression models were trained to predict the fuel parameters IE, BU and CT based on combinations of radiation signatures calculated from a previously modelled Pressurised Water Reactor (PWR) spent nuclear fuel library. The radiation signatures studied were the relative gamma-ray activities of Cs137, Cs134 and Eu154, their total gamma-ray activity, the total neutron emission rate and the parametrized early die-away time ? from the Differential Die-away Self Interrogation (DDSI) instrument. The performance of the models were tested on simulations of 2192 PWR fuel assemblies from the Ringhals 3 and 4 nuclear power plants in Sweden, which were simulated based on their documented irradiation histories. Despite significant differences in irradiation history between the training and testing data sets, the Ringhals assembly parameters could be predicted with similar accuracy as for assemblies in the training set. The relative gamma-ray activities were sufficient to predict the CT with an RMSE of 2 years, and adding a total gamma or total neutron signature allowed the BU to be predicted with an RMSE of 1.4 MWd/kgU. The DDSI early die-away time ? enabled an accurate IE prediction, with an RMSE of 0.16 w%. The differences between irradiation histories introduced a systematic bias where CT was overestimated by about 1 year and the BU by about 1.5 MWd/kgU.
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| 13. |
- Branger, Erik, 1988-, et al.
(författare)
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On Cherenkov light production by irradiated nuclear fuel rods
- 2017
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Safeguards verification of irradiated nuclear fuel assemblies in wet storage is frequently done by measuring the Cherenkov light in the surrounding water produced due to radioactive decays of fission products in the fuel. This paper accounts for the physical processes behind the Cherenkov light production caused by a single fuel rod in wet storage, and simulations are presented that investigate to what extent various properties of the rod affect the Cherenkov light production. The results show that the fuel properties has a noticeable effect on the Cherenkov light production, and thus that the prediction models for Cherenkov light production which are used in the safeguards verifications could potentially be improved by considering these properties.It is concluded that the dominating source of the Cherenkov light is gamma-ray interactions with electrons in the surrounding water. Electrons created from beta decay may also exit the fuel and produce Cherenkov light, and e.g. Y-90 was identified as a possible contributor to significant levels of the measurable Cherenkov light in long-cooled fuel. The results also show that the cylindrical, elongated fuel rod geometry results in a non-isotropic Cherenkov light production, and the light component parallel to the rod's axis exhibits a dependence on gamma-ray energy that differs from the total intensity, which is of importance since the typical safeguards measurement situation observes the vertical light component. It is also concluded that the radial distributions of the radiation sources in a fuel rod will affect the Cherenkov light production.
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| 14. |
- Branger, Erik, 1988-, et al.
(författare)
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On the inclusion of light transport in prediction tools for Cherenkov light intensity assessment of irradiated nuclear fuel assemblies
- 2019
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool used to verify irradiated nuclear fuel assemblies in wet storage by imaging the Cherenkov light produced by the radiation emitted from the assemblies. It is frequently used for partial defect verification, verifying that part of an assembly has not been removed and/or replaced. In one of the verification procedures used, the detected total Cherenkov light intensities from a set of assemblies are compared to predicted intensities, which are calculated using operator declarations for the assemblies.This work presents a new, time-efficient method to simulate DCVD images of fuel assemblies, allowing for estimations of the Cherenkov light production, transport and detection. Qualitatively, good agreement between simulated and measured images is demonstrated. Quantitatively, it is shown that relative intensity predictions based on simulated images are within 0.5% of corresponding predictions based solely on the production of Cherenkov light, neglecting light transport and detection. Consequently, in most cases it is sufficient to use predictions based on produced Cherenkov light, neglecting transport and detection, thus substantially reducing the time needed for simulations.In a verification campaign, assemblies are grouped according to their type, and the relative measured and predicted intensities are compared in a group. By determining transparency factors, describing the fraction of Cherenkov light that is blocked by the top plate of an assembly, it is possible to adjust predictions based on the production of Cherenkov light to take the effect of the top plate into account. This procedure allows assemblies of the same type bit with different top plates to be compared with increased accuracy. The effect of using predictions adjusted with transparency factors were assessed experimentally on a set of Pressurized Water Reactor 17x17 assemblies having five different top plate designs. As a result of the adjustment, the agreement between measured and predicted relative intensities for the whole data set was enhanced, resulting in a reduction of an RMSE from 14.1% to 10.7%. It is expected that further enhancements may be achieved by introducing more detailed top-plate and spacer descriptions.
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| 15. |
- Branger, Erik, 1988-, et al.
(författare)
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Partial defect detection using the DCVD and a segmented Region-Of-Interest
- 2020
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a safeguards instrument available to international nuclear safeguards inspectors. It is frequently used to verify fuel on the gross defect level, and approved for partial defect verification, i.e. to assess that parts of a fuel assembly have not been diverted. The current limit for partial defect verification with the DCVD is on the 50% level. In the verification process, an analysis methodology is used where the inspector places a Region-Of-Interest (ROI) around the fuel assembly and assesses the total Cherenkov light intensity within this region. The intensity is then compared to a predicted value, and deviations from the predicted value are used to flag fuel assemblies for further investigations. In this work, we investigate a slightly different analysis approach, where the ROI is split into two or three segments to more accurately capture changes in light intensity in different regions of the captured image. The purpose is to increase the sensitivity of the DCVD to partial defects below the 50% level. Based on simulations of a Pressurised Water Reactor 17x17 fuel assembly, we conclude that a partial defect on the 30% level decreases the Cherenkov light intensity by at least 15% using one single ROI, by at least 20% using a ROI with two segments, and by at least 22% using a ROI with three segments. The analysis approach using two or three ROI segments instead of one thus appears to be more sensitive to partial defects, and can enable more accurate detection of partial defects on the 50% level as well as partial defect detection below the 50% level.Validation of the approach using a limited set of measurement data of intact fuel assemblies supports that detection of light intensity reductions by 20% and 22% is possible, while ensuring that the false positive rate is kept sufficiently low. However, an optimization of ROI segment splits as well as a more extended validation of the approach is required before the method can be considered reliable and applicable to all fuel assemblies that the DCVD can verify today.
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| 16. |
- Branger, Erik, 1988-, et al.
(författare)
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Plutonium Production under Uranium Constraint
- 2023
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Ingår i: Science and Global Security. - : Routledge. - 0892-9882 .- 1547-7800. ; 31:3, s. 115-136
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Tidskriftsartikel (refereegranskat)abstract
- Production rates of fissile materials are often used to independently assess the number of nuclear warheads a state may possess. One key constraint of a plutonium-based nuclear weapons program is the availability of natural uranium, where a shortage of uranium will constrain plutonium production in the fuel cycle. Recycling of the reprocessed uranium can be used to mitigate such a shortage. Furthermore, since military reactors operate in short cycles to ensure that the plutonium is weapon-grade, it may be possible to operate them using slightly depleted uranium, provided that there are sufficient reactivity margins. Using slightly depleted or recycled uranium, the plutonium production can increase by a factor 2–5 as compared to a once-through scenario, for the same input of natural uranium. For future assessments of a state’s plutonium production, a uranium constraint should only be considered if there is clear evidence that no nuclear fuel cycle involving uranium recycling is implemented, or if evidence exists that the recycling is insufficient to mitigate the constraint.
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| 17. |
- Branger, Erik, 1988-, et al.
(författare)
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Studies of the impact of beta contributions on Cherenkov light emission by spent nuclear fuel
- 2022
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Ingår i: ESARDA Bulletin. - : ESARDA. - 1977-5296. ; 64:1, s. 2-9
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Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is one of the instruments used by safeguards inspectors to verify spent nuclear fuel in wet storage. The DCVD can be used for partial defect verification, where the inspectors verify that 50% or more of an assembly has not been diverted. The methodology is based on comparing the measured Cherenkov light intensity with a predicted intensity, calculated with operator information.Recently, IAEA inspectors have encountered fuel assemblies for which systematic deviations between predictions and measurements could be observed, indicating that the prediction model did not take into account all sources of Cherenkov light production. One contribution to the Cherenkov light intensity that is frequently omitted is the contribution from beta decays, where energetic electrons exit the fuel material and enter the water with sufficient energy to directly produce Cherenkov light. The objective with this work was hence to study beta contributions and evaluate whether that could be the cause of discrepancy between predictions and experimental data.By simulating the beta contribution for fuel assemblies where the discrepancy was experimentally observed, it was determined that beta decays were the cause. The fuel assemblies had fuel rods with relatively small radii, thin cladding, a short cooling time and an irradiation history that resulted in a relatively large beta contribution for assemblies that had a comparatively low burnup. Therefore, the beta contribution was significant, and caused 10-40% of the total Cherenkov light intensity. By including the beta contributions in the predictions, the RMSE of the deviation between prediction and measurement could be reduced from 20.7% to 11.6% for the available measurement data. The results highlight that the beta contribution can be significant and should be taken into account for accurate predictions.
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| 18. |
- Branger, Erik, 1988-, et al.
(författare)
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Verifying PWR assemblies with rod cluster control assembly inserts using a DCVD
- 2019
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Ingår i: ESARDA Bulletin. - 1977-5296. ; :58, s. 35-40
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Tidskriftsartikel (refereegranskat)abstract
- One of the instruments available to authority inspectors to measure and characterize the Cherenkov light emissions from irradiated nuclear fuel assemblies in wet storage is the Digital Cherenkov Viewing Device (DCVD). Based on the presence, characteristics and intensity of the Cherenkov light, the inspectors can verify that an assembly under study is not a dummy object, as well as perform partial defect verification of the assembly.PWR assemblies are sometimes stored with a rod cluster control assembly (RCCA) inserted, which affects the Cherenkov light production and transport in the assembly. Such an insert will also block light from exiting the top of the fuel assembly, which will affect the light distribution and intensity of the Cherenkov light emissions. Whether or not this constitutes a problem when verifying the assemblies for gross or partial defects with a DCVD has not previously been investigated thoroughly.In this work, the Cherenkov light intensity of a PWR 17x17 assembly with two different RCCA inserts were simulated and analysed, and compared to the Cherenkov light intensity from an assembly without an insert. For the studied assembly and insert types, the DCVD was found to be able to detect partial defects on the level of 50% in all studied cases with similar performance, though with a higher measurement uncertainty due to the reduced intensity when an RCCA insert is present. Consequently, for the studied assembly and insert types, assemblies with inserts can be verified with the same methodology as used for assemblies without inserts, with similar partial defect detection performance.The simulation approach used also made it possible to investigate the minimum Cherenkov light intensity reduction resulting from partial defects of other levels than 50%, in the PWR 17x17 fuel assembly with and without RCCA inserts. The results for the simulations without an insert were in agreement with previous results, despite differences in substitution patterns, substitution materials, modeling software and analysis approach.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Caldeira Balkeståhl, Li, et al.
(författare)
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Parametrization of the differential die-away self-interrogation early die-away time for PWR spent fuel assemblies
- 2019
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Ingår i: ESARDA Bulletin. - JRC Ispra. ; , s. 13-21
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Konferensbidrag (refereegranskat)abstract
- The differential die-away self-interrogation (DDSI) instrument developed and built in Los Alamos National Laboratory (LANL) is being considered for verification before final disposal. One of the signals from this instrument, the early die-away time, has been shown to be proportional to the multiplication of the spent fuel assembly. Full-scale simulations of the instrument response using MCNP are time consuming. This may become a problem in cases when the instrument response to a large number of fuel assemblies is required, such as in the case of training machine learning models. In this paper, we propose a parametrization of the early die-away time as a function of initial enrichment (IE), burn-up (BU) and cooling time (CT), for intact PWR spent fuel assemblies. The parametrization is calculated from a dataset of 1040 simulated PWR spent fuel assemblies with fuel parameters in the range of IE=2-5%, BU=15-60 GWd/tU and CT=5-70 years. The simulations are done using Serpent2 for the depletion calculation and MCNP6 for the neutron transport and detection in the DDSI. It was found that the CT dependence can be decoupled from the BU and IE dependence, and that it follows an exponential decay. The BU and IE dependences have been fitted with several different functions, and the best fit was chosen based on the chi-square value. The determination of the die-away time using the parametrization has been tested on a separate dataset, resulting in a root mean square error (RMSE) of 0.6 µs (the early die-away time ranges from 28 µs to 84 µs). A description of this work is given in the paper together with details on the choice of parametrizing function, and qualitative arguments for that choice.
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| 23. |
- Davour, Anna, et al.
(författare)
-
Applying image analysis techniques to tomographic images of irradiated nuclear fuel assemblies
- 2016
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 96, s. 223-229
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a set of image analysis techniques used for extraction of information from cross-sectional images of nuclear fuel assemblies, achieved from gamma emission tomography measurements. These techniques are based on template matching, an established method for identifying objects with known properties in images.We demonstrate a rod template matching algorithm for identification and counting of the fuel rods present in the image. This technique may be applicable in nuclear safeguards inspections, because of the potential of verifying the presence of all fuel rods, or potentially discovering any that are missing.We also demonstrate the accurate determination of the position of a fuel assembly, or parts of the assembly, within the imaged area. Accurate knowledge of the assembly position enables detailed modelling of the gamma transport through the fuel, which in turn is needed to make tomographic reconstructions quantifying the activity in each fuel rod with high precision.Using the full gamma energy spectrum, details about the location of different gamma-emitting isotopes within the fuel assembly can be extracted. We also demonstrate the capability to determine the position of supporting parts of the nuclear fuel assembly through their attenuating effect on the gamma rays emitted from the fuel. Altogether this enhances the capabilities of non-destructive nuclear fuel characterization.
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| 24. |
- Elter, Zsolt, et al.
(författare)
-
A methodology to identify partial defects in spent nuclear fuel using gamma spectroscopy data
- 2020
-
Ingår i: ESARDA Bulletin. - : ESARDA and Joint Research Centre of the European Commission. - 1977-5296. ; :61, s. 22-31
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes a methodology to identify partial defects in modelled spent nuclear fuel using passive gamma spectroscopy data. A fuel library, developed with Serpent2, was used to calculate the material composition of spent nuclear fuel. Two fuel configurations were investigated in this work; one where the fuel assembly configuration was intact and one where 30% of the fuelrods were substituted with stainless steel rods in a random configuration. Emission and detection of gamma radiation from 134Cs, 137Cs and 154Eu was simulated using a model of a passive gamma spectroscopy measurement station mimicking the Clab measurement station in Sweden. A simple HPGe detector model was implemented, and its detector efficiency was assessed using a range of different source energies. Realistic total gamma attenuation coefficients were calculated using the XCOM database.The modelled estimates of detected full-energy peak counts were then used in a Principal Component Analysis in order to investigate whether it was possible to distinguish between intact and partial defect fuel assemblies or not. The results showed that partial defects could be identified using the simultaneous analysis of all three peak intensities, and that the ability to do so increased when only gamma emission energies from 154Eu were considered.
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| 25. |
- Elter, Zsolt, et al.
(författare)
-
Development of a modeling approach to estimate radiation from a spent fuel rod quiver
- 2020
-
Ingår i: PHYSOR 2020. - : EDP Sciences. - 9781527264472
-
Konferensbidrag (refereegranskat)abstract
- Before encapsulation of spent nuclear fuel in a geological repository, the fuels need to be verified for safeguards purposes. This requirement applies to all spent fuel assemblies, including those with properties or designs that are especially challenging to verify. One such example are quivers, a new type of containers used to hold damaged spent fuel rods. After placing damaged rods inside the quivers, they are sealed with a thick lid and the water is removed. The lid is thick enough to significantly reduce the amount of the gamma radiation penetrating through it, which can make safeguards verification from the top using gamma techniques difficult. Considering that the number of quivers at storage facilities is foreseen to increase in near future, studying the feasibility of verification is timely.In this paper we make a feasibility study related to safeguards verification of quivers, aimed at investigating the gamma and neutron radiation field around a quiver designed by Westinghouse AB and filled with PWR fuel rods irradiated at the Swedish Ringhals site. A simplified geometry of the quiver and the detailed operational history of each rod are provided by Westinghouse and the reactor operator, respectively.The nuclide inventory of the rods placed in the quiver and the emission source terms are calculated with ORIGEN-ARP. The radiation transport is modeled with the Serpent2 Monte Carlo code. The first objective is to assess the capability of the spent fuel attribute tester (SFAT) to verify the content for nuclear safeguards purposes. The results show that the thick quiver lid attenuates the gamma radiation, thereby making gamma radiation based verification from above the quiver difficult.
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| 26. |
- Elter, Zsolt, et al.
(författare)
-
feign : a Python package to estimate geometric efficiency in passive gamma spectroscopy measurements of nuclear fuel
- 2019
-
Ingår i: Journal of Open Source Software. - : Open Journals. - 2475-9066. ; 4:42
-
Tidskriftsartikel (refereegranskat)abstract
- The operator declarations of spent nuclear fuel assemblies are routinely verified for nuclearsafeguards purposes to ensure their non-diversion and integrity. Many countries considerthe possibility of eventually placing the fuel in a geological repository and prior to this it isexpected that the fuel assemblies need to be carefully characterized and verified, for instanceusing gamma spectroscopy measurements. It can be expected that in connection to suchactivities, verifying parameters such as burnup (the energy outtake from the nuclear fuel),cooling time (the time the fuel spent outside the reactor after operation), initial enrichment(the amount of fissile material in the fuel before operation) and integrity (whether pins insidethe assembly have been manipulated) may become an important task of nuclear safeguardsinspectors, since discrepancies may indicate unauthorized activities at the facilities. Ideally,the verification should be done with non-destructive assay systems.Passive gamma spectroscopy provides a robust and relatively simple method to analyze spentfuel since the characteristics of spent nuclear fuel strongly affect the gamma radiation emittedfrom the fuel (Jansson, 2002). Lately, passive gamma tomography has also become a possiblemethod to characterize and analyze properties of spent nuclear fuels (Mayorov et al., 2017).In both cases, gamma radiation is measured around the fuel assembly from a distance usingone or more collimated detectors with spectroscopic capabilities. Of great interest is thedetector efficiency of these systems, i.e., the ratio between number of detected particles andnumber of particles emitted by the source. The detector efficiency is the product of thegeometric efficiency (probability that emitted particles reach the detector region) and theintrinsic efficiency of the detector (probability that the particles are detected)
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| 27. |
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| 28. |
- Elter, Zsolt, et al.
(författare)
-
Investigating the gamma and neutron radiation around quivers for verification purposes
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Before encapsulation of spent nuclear fuel in a geological repository, the fuels need to be verified fors afeguards purposes. This requirement applies to all spent fuel assemblies, including those with properties or designs that are especially challenging to verify. One such example are quivers, a new type of containers used to hold damaged spent fuel rods. After placing damaged rods inside the quivers, they are sealed with a thick lid and the water is removed. The lid is thick enough to significantly reduce the amount of the gamma radiation penetrating through it, which can make safeguards verification from the top using gamma techniques difficult.In this paper we make a first feasibility study related to safeguards verification of quivers, aimed at investigating the gamma and neutron radiation field around a quiver using a simplified quiver geometry. The nuclide inventory of the rods placed in the quiver is calculated with Serpent and Origen-Arp, and the radiation transport is modeled with Serpent. The objective is to assess the capability of existing non-destructive assay instruments, measuring the gamma and/or neutron radiation from the object, to verify the content for nuclear safeguards purposes. The results show that the thick quiver lid attenuates the gamma radiation, thereby making gamma-radiation based verification from above the quiver difficult. Verification using neutron instruments above the quiver, or gamma and/or neutron instruments on the side may be possible. These results are in agreement with measurements of a BWR quiver using a DCVD, performed by the authors.
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| 29. |
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| 30. |
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| 31. |
- Elter, Zsolt, et al.
(författare)
-
Pressurized water reactor spent nuclear fuel data library produced with the Serpent2 code
- 2020
-
Ingår i: Data in Brief. - : Elsevier BV. - 2352-3409. ; 33
-
Tidskriftsartikel (refereegranskat)abstract
- The paper describes a data library containing material composition of spent nuclear fuel. The data is extracted from burnup and depletion calculations with the Serpent2 code. The simulations were done with a PWR fuel pin cell geometry, for both initial UO2 and MOX fuel load for a wide range of initial enrichments (IE) or initial plutonium content (IPC), discharge burnup (BU) and cooling time (CT).The fuel library contains the atomic density of 279 nuclides (fission products and actinides), the total spontaneous fission rate, total photon emission rate, activity and decay heat at 789,406 different BU, CT, IE configurations for UO2 fuel and at 531,991 different BU, CT, IPC configurations for MOX fuel. The fuel library is organized in a publicly available comma separated value file, thus its further analysis is possible and simple.
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| 32. |
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| 33. |
- Grape, Sophie, 1982-
(författare)
-
Applied Nuclear Physics in the Alva Myrdal Centre for Nuclear Disarmament: Non-Proliferation and Safeguards Activities
- 2023
-
Konferensbidrag (populärvet., debatt m.m.)abstract
- In 2020, the Swedish government announced the plans to start up a national competence centre on nuclear disarmament in Sweden. The objective was to highlight the importance of nuclear disarmament and to promote research, teaching and policy support on relevant topics. In mid-2021, the Alva Myrdal Centre (AMC) on nuclear disarmament was formally established at Uppsala University. The AMC combines competences from different disciplines such as peace and conflict research, applied nuclear physics, and international law, and organises the work into six different working groups. One of the working groups, led by the Division of Applied Nuclear Physics at Uppsala University, is focusing on technical aspects. In this division, research on nuclear safeguards has been performed for over 30 years, and competence exists on a number of applied physics applications ranging from nuclear reactions, nuclear power and detection of radionuclides. This presentation gives an overview of a number of different technical research projects that have been pursued within the technical working group under AMC.
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| 34. |
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| 35. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Building a Strategy for ESARDA - Education, Training and Knowledge Management
- 2015
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This document proposes a new strategy for how the ESARDA organization could work with education, training and knowledge management in nuclear safeguards. With this document we want to anchor these ideas within the organization and its management, in order to have a broad support for this initiative. We propose to activate all ESARDA working groups in the process of identifying, selecting and preparing material for module based education and training. ESARDA could then more effectively broaden its education and training activities and strengthen the connections with academia. In this way, we would also create a way to export knowledge on nuclear safeguards to nuclear education programs on the European level. We propose to create a task force that addresses a set of identified questions; examples are how to implement the new strategy, how to interact with academia and young professionals and how to develop, maintain, and structure the educational modules. By the end of 2015, the findings of the task force should be presented to the ESARDA management in order to be able to make a more informed decision on how to proceed with the new strategy.
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| 36. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Determination of spent nuclear fuel parameters using modelled signatures from non-destructive assay and Random Forest regression
- 2020
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 969
-
Tidskriftsartikel (refereegranskat)abstract
- Verification of fuel parameters is a central undertaking for nuclear inspectors aiming at verifying the completeness and correctness of operator declarations. Traditionally, such verification is done analysing data from one instrument at a time. Here we present a study based on simulated data from various non-destructive assay measurement techniques applied on modelled PWR nuclear fuel assemblies. The data comprised multiple signatures and were analysed using machine learning algorithms. These signatures included activities from gamma-ray emitting fission product radionuclides, the parametrised early die-away time.. from the prototype Differential Die-away Self-Interrogation (DDSI) instrument, as well as the total Cherenkov light intensity which is directly measurable. The objective of the work is to systematically explore the capability to predict values of the fuel parameters initial enrichment (IE), burnup (BU) and cooling time (CT) independently of operator declarations, using Random Forest regression and modelled pressurised water reactor (PWR) fuel. The results show that passive gamma-ray activities alone can be used to predict IE, BU and CT for CT<20 years, and that by adding a feature proportional to the total gamma-ray activity, the errors in the predictions are significantly reduced. In this work, two measures proportional to total gamma activity have been studied: the sum of all considered gamma-ray intensities, and the total Cherenkov light intensity. From this work it was concluded that for fuels with CTs between 20 and 70 years, CT can be well determined by a multivariate analysis of the activities of Cs-134, Cs-137, Eu-154. For a BU determination, an additional feature corresponding to total gamma activity is required. This is, however, not sufficient to determine IE, which requires inclusion of the neutron signature.. as well.
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| 37. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Development of a PhD course in verification of nuclear test explosions under AMC
- 2022
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Under the AMC, a range of activities covering education, research and outreach are foreseen. One of them concerns education and the build-up of competence related to disarmament, and for that reason collaborative efforts have been ongoing during 2021 and 2022 to develop a PhD-level course in verification of nuclear test explosions, and to offer it during September-October 2022. The course has developed by Uppsala University and the Swedish Defence Reserach Agency (FOI) and corresponds to 7.5 credits. It is a cross-disciplinary course that spans over several disciplines. It introduces the participants to treaties and verification regimes governing nuclear weapons and it explains identification, calculation and analysis of signatures from nuclear weapon explosions. Furthermore, effort has been made to let the participants actively work with data collection, aggregation, analysis and with the interpretation and evaluation of data. The course includes also both a laboratory exercise on detection of radionuclides, and a project work in which the participants analyze a test explosion scenario and summarize their findings and conclusions in a manner very similar to how this is done in reality.This poster will describe the details of the course and its content. Since the course is planned to be offered just before this conference, we also hope to provide some information on its execution, as well as feedback from the participants.
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| 38. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Experimental verification of simulated predictions from the DDSI instrument
- 2023
-
Ingår i: Proceedings of the INMM & ESARDA Joint Annual Meeting, May 22-26, 2023. - : Institute of Nuclear Materials Management (INMM). ; , s. 1-10
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Differential Die-away Self Interrogation (DDSI) instrument was researched for many years under the Next Generation Safeguards Initiative Spent Fuel effort. Later a prototype instrument was manufactured and used to make non-destructive measurements of spent nuclear fuel in the Swedish Central Interim Storage Facility for Spent Nuclear Fuel (Clab) in Sweden in 2018. Results of DDSI research, based on either simulations or measurement time, have indicated that the instrument could successfully be used to draw safeguards-relevant conclusions about spent nuclear fuel.In this work we investigate how well the modelled response of the DDSI instrument, based on Serpent and MCNP simulations, corresponds to measured data of 17x17 pressurised reactor fuel. We also studied repeatability, i.e. to what extent repeated measurements on the same fuel assembly gave consistent results. We also investigated the dependence of tau on the selected time window. The results show that tau values determined from measurement data are consistently higher than tau values determined from simulations, and that the magnitude of tau is dependent on the choice of time window. We also note that tau is relatively insensitive to positioning in the DDSI instrument.
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| 39. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Forskning inom teknisk kärnämneskontroll vid Uppsala universitet under 2014–2015
- 2016
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Uppsala universitet har inom ramen för olika avtal med SSM under 2014-2015 bedrivit ett omfattande forskningsprogram inom kärnämneskontroll. Forskningsprogrammet har under denna tid innefattat 3 doktorander med dedikerade forskningsprojekt och ett flertal seniora forskare som helt eller delvis har varit engagerade inom kärnämneskontroll.Denna rapport uppmärksammar särskilt fyra forskningsområden av hög relevans för den globala kärnämneskontrollen, vilka benämns; DCVD, Next Generation Safeguards Initiative, verifiering av atypiska bränsleobjekt och Generation IV kärnkraftsystem. Även andra forskningsaktiviteter har genomförts inom ramen för forskningsprogrammet, vilka dock ligger utanför redovisningen i denna rapport.Under perioden 2014-2015 producerades inom forskningsprogrammet 9 artiklar som skickats till vetenskapliga tidskrifter med peer-review-granskning. Därutöver gjordes medvetna satsningar på att lyfta fram forskningen på de arenor som är av störst betydelse för det internationella kärnämneskontrollarbetet, d.v.s. på de symposier och möten som arrangeras av FN:s internationella atomenergiorgan (IAEA), det europeiska samarbetsorganet ESARDA och den amerikanska organisationen INMM. Vid dessa internationella konferenser publicerades ytterligare 15 vetenskapliga artiklar med unikt innehåll under perioden. En publikationslista med samtliga forskningsarbeten som producerats under perioden redovisas i denna rapport.
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| 40. |
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| 41. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Machine learning in nuclear safeguards
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- •Before placing spent nuclear fuel in in a geological repository, they will be characterized and their declared properties will be verified.•We have created large library of modelled spent nuclear fuel (SNF) assemblies and estimated their activity of gamma-ray emitting fission products, the early die-away time τ and the Cherenkov light intensity.•We have used Random Forest regression to evaluate the capability to determine the fuel parameters initial enrichment (IE), burnup (BU) and cooling time (CT) using data from non-destructive assay (NDA) techniques
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| 42. |
- Grape, Sophie, 1982-, et al.
(författare)
-
New perspectives on nuclear power - Generation IV nuclear energy systems to strengthen nuclear non-proliferation and support nuclear disarmament
- 2014
-
Ingår i: Energy Policy. - : Elsevier BV. - 0301-4215 .- 1873-6777. ; 73, s. 815-819
-
Tidskriftsartikel (refereegranskat)abstract
- Recently, nuclear power has received support from environmental and climate researchers emphasizing the need to address factors of global importance such as climate change, peace and welfare. Here, we add to previous discussions on meeting future climate goals while securing safe supplies of energy by discussing future nuclear energy systems in the perspective of strengthening nuclear non-proliferation and aiding in the process of reducing stockpiles of nuclear weapons materials.New nuclear energy systems, currently under development within the Generation IV (Gen IV) framework, are being designed to offer passive safety and inherent means to mitigate consequences of nuclear accidents. Here, we describe how these systems may also be used to reduce or even eliminate stockpiles of civil and military plutonium—the former present in waste from today׳s reactors and the latter produced for weapons purposes. It is argued that large-scale implementation of Gen IV systems would impose needs for strong nuclear safeguards. The deployment of Safeguards-by-Design principles in the design and construction phases can avoid draining of IAEA resources by enabling more effective and cost-efficient nuclear safeguards, as compared to the current safeguards implementation, which was enforced decades after the first nuclear power plants started operation.
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| 43. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Non-proliferation and safeguards activities within the Alva Myrdal Centre for nuclear disarmament
- 2022
-
Ingår i: Proceedings of the Symposium on International Safeguards: Reflecting on the Past and Anticipating the Future.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In 2020, the Swedish government announced the intent to start up a national competence centre on nuclear disarmament in Sweden. The goal was to highlight the importance of nuclear disarmament issues, and to promote research, teaching and policy support on topics relevant to nuclear disarmament. During the spring semester 2021, the Alva Myrdal Centre (AMC) on nuclear disarmament was established at Uppsala University. The AMC combines competences from different disciplines such as peace and conflict research, applied nuclear physics, and international law, and organises the work into six different working groups. One of the working groups is focusing on technical aspects, while the remaining five working groups are focusing on policy aspects. The technical working group is led by the Division of Applied Nuclear Physics at Uppsala University, where research on nuclear safeguards has been performed for over 30 years, and where competence in addition exists on a number of applied physics applications ranging from nuclear reactions, nuclear power and detection of radionuclides.
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| 44. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Partial defect verification using the DCVD : a capability evaluation approach
- 2011
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a non-intrusive instrument available to theInternational Atomic Energy Agency (IAEA) for verifying spent nuclear fuel in storage pools. It iscurrently used for gross-defect evaluations, i.e. to verify that an item in a storage pool is anirradiated fuel assembly and not a fresh assembly or a dummy. This is done by recording images ofthe Cherenkov light emitted in the water surrounding the fuel. Currently, the instrument’s ability toalso detect partial defects at the 50% level or even lower is under study. Here, experimental work iscomplimented by modeling and simulations due to the limited availability of assemblies with partialdefects.Ideally, an IAEA inspector should be able to use the DCVD at e.g. a fuel storage site andimmediately after scanning obtain information on (1) whether an item is an irradiated fuel assemblyor not, and (2) whether the assembly is intact or suffers from a partial defect. This paper discusses adecision-making methodology intended for the latter purpose with the objective to implement it inthe DCVD software in order to facilitate smooth inspection procedures. Inspectors will thus not berequired to possess any expertise in the decision-making methodology.The paper also describes measurements performed during spring 2011 at the CLAB interim spentfuel storage in Sweden. The measurements were carried out with the objective to optimize theequipment handling and work flow during this type of measurement campaigns and to form a basisfor the evaluation of the DCVD’s ability to detect partial defects.
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| 45. |
- Grape, Sophie, 1982-
(författare)
-
PWO Crystal Measurements and Simulation Studies of Anti-Hyperon Polarisation for PANDA
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Gesellschaft für Schwerionenforschung (GSI) facility in Darmstadt, Germany, will be upgraded to accommodate a new generation of physics experiments. The future accelerator facility will be called FAIR and one of the experimentsat the site will be PANDA, which aims at performing hadron physics investigations by colliding anti-protons with protons. The licentiate thesis consistsof three sections related to PANDA. The first contains energy resolutionstudies of PbWO4 crystals, the second light yield uniformity studies of PbWO4 crystals and the third reconstruction of the lambda-bar-polarisation in the PANDA experiment. Two measurements of the energy resolution were performed at MAX-Lab in Lund, Sweden, with an array of 3x3 PbWO4 crystals using a tagged photon beam with energies between 19 and 56 MeV. For the April measurement, the crystals were cooled down to -15 degrees C and for the September measurement down to -25 degrees C. The measured relative energy resolution, /E, is decreasing from approximately 12% at 20 MeV to 7% at 55 MeV. In the standard energy resolution expression /E = a/ b/E c, the three parameters a, b and c seem to be strongly correlated and thus difficult to determine independently over this relative small energy range. The value of a was therefore fixed to that one would expect from Poisson statistics of the light collection yield (50 phe/MeV) and the results from fits were /E=0.45%/ 0.18%/EGeV 8.63% and /E = 0.45%/0.21%/EGeV 6.12% for the April and September measurements, respectively. The data from the September measurement was also combined with previous data from MAMI for higher energies, ranging from approximately 64 to 715 MeV. The global fit over the whole range of energies gave an energy resolution expression of /E = 1.6%/ 0.095%/EGeV 2.1%. Light yield uniformity studies of five PbWO4 crystals, three tapered and two non-tapered ones, have also been performed. The tapered crystals delivered a light output which increased with increasing distance from the Photo Multiplier Tube (PM tube). Black tape was put on different sides of one tapered crystals, far from the PM tube to try to get a more constant uniformity prole. It was seen that the light output profile depends on the position of the tape. Generally, the steep increase in light output at large distances from the PM tube could be damped. The third part of the thesis concerns the reconstruction of the lambdabar polarisation in the reaction . Events were generated using a modied generator from the PS185 experiment at LEAR. With a 100% polarisation perpendicular to the scattering plane, a polarisation of (99±1.8)% was reconstructed. Slight non-zero polarisations along the axis determined by the outgoing hyperon as well as the axis in the scattering plane, were also reconstructed. These were (4.1±2.1)% and (2.6±2.0)% respectively. From this investigation it was shown that the detector efficiency was not homogeneous and that slow pions are difficult to reconstruct.
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| 46. |
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| 47. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Recent modelling studies for analysing the partial-defect detection capability of the Digital Cherenkov Vieweing Device
- 2014
-
Ingår i: Esarda Bulletin. - Ispra. - 0392-3029. ; :51, s. 3-8
-
Tidskriftsartikel (refereegranskat)abstract
- Strong sources of radioactivity, such as spent nuclear fuel stored in water pools, give rise to Cherenkov light. This light originates from particles, in this case electrons released from gamma-ray interactions, which travel faster than the speed of light in the water. In nuclear safeguards, detection of the Cherenkov light intensity is used as a means for verifying gross and partial defect of irradiated fuel assemblies in wet storage. For spent nuclear fuel, the magnitude of the Cherenkov light emission depends on the initial fuel enrichment (IE), the power history (in particular the total fuel burnup (BU)) and the cooling time (CT). This paper presents recent results on the expected Cherenkov light emission intensity obtained from modelling a full 8x8 BWR fuel assembly with varying values of IE, BU and CT. These results are part of a larger effort to also investigate the Cherenkov light emission for fuels with varying irradiation history and other fuel geometries in order to increase the capability to predict the light intensity and thus lower the detection limits for the Digital Cherenkov Viewing Device (DCVD). The results show that there is a strong dependence of the Cherenkov light intensity on BU and CT, in accordance with previous studies. However, the dependences demonstrated previously are not fully repeated; the current study indicates a less steep decrease of the intensity with increasing CT. Accordingly, it is suggested to perform dedicated experimental studies on fuel with different BU and CT to resolve the differences and to enhance future predictive capability. In addition to this, the dependence of the Cherenkov light intensity on the IE has been investigated. Furthermore, the modelling of the Cherenkov light emission has been extended to CTs shorter than one year. The results indicate that high-accuracy predictions for short-cooled fuel may require more detailed information on the irradiation history.
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| 48. |
- Grape, Sophie, 1982-, et al.
(författare)
-
Recent modelling studies for analysing the partial-defect detection capability of theDigital Cherenkov Viewing Device
- 2013
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is an instrument available to IAEA inspectors forverifying spent nuclear fuel in wet storage at nuclear facilities. The instrument records the Cherenkovlight that is emitted in the water surrounding the highly radioactive fuel. The light intensity is largelydependent on the amount of nuclear material in the fuel as well as its burnup and cooling time and can beused by the inspector as a measure for verifying the properties of the fuel.To aid in the analysis of the Cherenkov light intensity, a simulation toolkit has been developed, whichmodels the emission, transport and detection of Cherenkov light. This toolkit is particularly useful forinvestigating the response of the DCVD for fuel assemblies subject to different types of partial defects,where fuel rods might have been removed or substituted with non-irradiated material. Variousconfigurations of partial defects may be simulated in order to evaluate the detection capabilities of theDCVD.Here, we present how the light intensity recorded by the DCVD is affected by the fuel history and by thepartial defect scenario. We present a methodology for how the analysis and interpretation of recordedintensities may be performed to result in confidence-supported statements of different levels of partialdefect. Finally, we suggest topics for further studies to accomplish an automated inspection system based on this methodology.
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| 49. |
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| 50. |
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