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Branger, E., Grape, S., Jansson, P. & Jacobsson Svärd, S. (2018). Experimental evaluation of models for predicting Cherenkov light intensities from short-cooled nuclear fuel assemblies. Journal of Instrumentation, 13, Article ID P02022.
Open this publication in new window or tab >>Experimental evaluation of models for predicting Cherenkov light intensities from short-cooled nuclear fuel assemblies
2018 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 13, article id P02022Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Cherenkov detectors; Search for radioactive and fissile materials; Simulation methods and programs; Radiation calculation
National Category
Subatomic Physics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-346692 (URN)10.1088/1748-0221/13/02/P02022 (DOI)000425937900001 ()
Funder
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011
Available from: 2018-03-20 Created: 2018-03-20 Last updated: 2018-08-17Bibliographically approved
Branger, E., Grape, S., Jansson, P. & Jacobsson Svärd, S. (2018). Experimental study of background subtraction in Digital Cherenkov Viewing Device measurements. Journal of Instrumentation, 13(8)
Open this publication in new window or tab >>Experimental study of background subtraction in Digital Cherenkov Viewing Device measurements
2018 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 13, no 8Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Nuclear safeguards, Cherenkov light, DCVD, Nuclear fuel
National Category
Subatomic Physics
Research subject
Physics with specialization in Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-357150 (URN)10.1088/1748-0221/13/08/T08008 (DOI)
Funder
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011
Available from: 2018-08-13 Created: 2018-08-13 Last updated: 2018-08-17Bibliographically approved
Bourva, L. & Jansson, P. (Eds.). (2018). International Workshop on Numerical Modelling of NDA Instrumentation and Methods for Nuclear Safeguards: (NM-NDA-IMNS18). Paper presented at International Workshop on Numerical Modelling of NDA Instrumentation and Methods for Nuclear Safeguards, Luxembourg, May 16-17, 2018. European Safeguards Research & Development Association (ESARDA)
Open this publication in new window or tab >>International Workshop on Numerical Modelling of NDA Instrumentation and Methods for Nuclear Safeguards: (NM-NDA-IMNS18)
2018 (English)Conference proceedings (editor) (Other academic)
Place, publisher, year, edition, pages
European Safeguards Research & Development Association (ESARDA), 2018. p. 151
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-366710 (URN)
Conference
International Workshop on Numerical Modelling of NDA Instrumentation and Methods for Nuclear Safeguards, Luxembourg, May 16-17, 2018
Available from: 2018-11-23 Created: 2018-11-23 Last updated: 2018-11-26Bibliographically approved
Jansson, P. (2018). Nonproliferation and nuclear fuel cycle back-end research at Uppsala University, Sweden: Special Seminar at PNNL.
Open this publication in new window or tab >>Nonproliferation and nuclear fuel cycle back-end research at Uppsala University, Sweden: Special Seminar at PNNL
2018 (English)Other (Other academic)
Abstract [en]

A brief overview of Uppsala University and the Department of Physics and Astronomy will be followed by a presentation of current research activities within the Division of Applied Nuclear Physics. Special attention will be given to on-going research in two sub-groups; Research for Nuclear Nonproliferation and research for the needs of the Swedish Nuclear Fuel and Waste Management company that is responsible for managing all the used nuclear fuel in Sweden, including encapsulation and deep geological disposal.

After the more organizational overview, the research performed within the research group regarding single photon gamma emission tomography (GET) of nuclear fuel assemblies will be presented both from a historical perspective and from the perspective of what is currently ongoing. Specifically, the work currently ongoing within the Swedish support program to IAEA Safeguards regarding GET will be presented.

Publisher
p. 59
Keywords
tomography, geological disposal, KBS-3, DCVD, back-end, gamma scanning, nuclear, MVA
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-340081 (URN)
Note

Presentation given at a Special Seminar on 2018-01-25 in the Radiation Detection & Nuclear Sciences Group at Pacific Northwest National Laboratory, USA.

Available from: 2018-01-25 Created: 2018-01-25 Last updated: 2018-02-01Bibliographically approved
Jansson, P. & Lantz, M. (2018). Räkneuppgifter till Säkerhetsanalyser inom energisektorn. Uppsala universitet
Open this publication in new window or tab >>Räkneuppgifter till Säkerhetsanalyser inom energisektorn
2018 (Swedish)Book (Other academic)
Place, publisher, year, edition, pages
Uppsala universitet, 2018. p. 39
Keywords
säkerhetsanalys, PSA, FTA, ETA, risk, säkerhet, sannolikhet
National Category
Probability Theory and Statistics Physical Sciences
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-337569 (URN)
Available from: 2018-01-02 Created: 2018-01-02 Last updated: 2018-08-21Bibliographically approved
Branger, E., Grape, S., Jacobsson, S., Jansson, P. & Andersson Sundén, E. (2017). Comparison of prediction models for Cherenkov light emissions from nuclear fuel assemblies. Journal of Instrumentation, 12, Article ID P06007.
Open this publication in new window or tab >>Comparison of prediction models for Cherenkov light emissions from nuclear fuel assemblies
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2017 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 12, article id P06007Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Cherenkov and transition radiation; Cherenkov detectors; Search for radioactive and; fissile materials; Interaction of radiation with matter
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-309739 (URN)10.1088/1748-0221/12/06/P06007 (DOI)000405090600007 ()
Funder
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011
Available from: 2016-12-07 Created: 2016-12-07 Last updated: 2018-08-17Bibliographically approved
Jansson, P. (2017). Converged results from Geant4 calculations of pin-by-pin contributions to 137Cs gamma radiation flux at Clab.
Open this publication in new window or tab >>Converged results from Geant4 calculations of pin-by-pin contributions to 137Cs gamma radiation flux at Clab
2017 (English)Data set, Aggregated data
Abstract [en]

A set of Geant4 calculations have been performed in reference [1] in which the gamma radiation flux through the opening of the collimator slit in the nuclear fuel gamma scanning equipment installed at the Swedish interim storage for used nuclear fuel (Clab) was calculated. This dataset contains data aggregated from the data in [1]. Specifically, the most converged gamma flux together with its calculated statistical uncertainty for each nuclear fuel rod is presented here.

[1] Jansson P.; "Results from Geant4 calculations of pin-by-pin contributions to 137Cs gamma radiation flux at Clab"; URL: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-316271; 2016

Keywords
Geant4, Clab, Gamma flux, Cs-137
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-317352 (URN)
Funder
Swedish National Infrastructure for Computing (SNIC), SNIC 2015/1-451Swedish National Infrastructure for Computing (SNIC), SNIC 2016/1-275
Note

Bash script updated 2018-02-26

Available from: 2017-03-14 Created: 2017-03-14 Last updated: 2018-03-02Bibliographically approved
Jansson, P. (2017). Digital Pulse Processing in HPGe Gamma-ray Spectroscopy: Supplement to the spring 2013, 2016 & 2017 courses on Activity Measurements with Germanium Detectors. Uppsala universitet
Open this publication in new window or tab >>Digital Pulse Processing in HPGe Gamma-ray Spectroscopy: Supplement to the spring 2013, 2016 & 2017 courses on Activity Measurements with Germanium Detectors
2017 (English)Book (Other academic)
Abstract [en]

A summary of basic digital signal processing systems is provided. Methods currently used in gamma-ray spectroscopy based on digital techniques are summarized. A list of references regarding digital spectroscopy is provided to guide the reader to relevant work.

Place, publisher, year, edition, pages
Uppsala universitet, 2017. p. 15
Keywords
digital pulse processing, HPGe, gamma-ray spectroscopy, high-purity germanium
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-349294 (URN)
Available from: 2018-04-25 Created: 2018-04-25 Last updated: 2018-04-26Bibliographically approved
Hellesen, C., Grape, S., Jansson, P., Jacobsson, S., Åberg Lindell, M. & Andersson, P. (2017). Nuclear Spent Fuel Parameter Determination using Multivariate Analysis of Fission Product Gamma Spectra. Annals of Nuclear Energy, 110, 886-895
Open this publication in new window or tab >>Nuclear Spent Fuel Parameter Determination using Multivariate Analysis of Fission Product Gamma Spectra
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2017 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 110, p. 886-895Article in journal (Refereed) Published
Abstract [en]

In this paper, we investigate the application of multivariate data analysis methods to the analysis of gamma spectroscopy measurements of spent nuclear fuel (SNF). Using a simulated irradiation and cooling of nuclear fuel over a wide range of cooling times (CT), total burnup at discharge (BU) and initial enrichments (IE) we investigate the possibilities of using a multivariate data analysis of the gamma ray emission signatures from the fuel to determine these fuel parameters. This is accomplished by training a multivariate analysis method on simulated data and then applying the method to simulated, but perturbed, data.

We find that for SNF with CT less than about 20 years, a single gamma spectrum from a high resolution gamma spectrometer, such as a high-purity germanium spectrometer, allows for the determination of the above mentioned fuel parameters.

Further, using measured gamma spectra from real SNF from Swedish pressurized light water reactors we were able to confirm the operator declared fuel parameters. In this case, a multivariate analysis trained on simulated data and applied to real data was used.

Keywords
Multivariate analysis, principal component analysis, partial least squares regression, gamma ray, nuclear fuel, safeguards
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-327108 (URN)10.1016/j.anucene.2017.07.035 (DOI)000412251000078 ()
Funder
Swedish Radiation Safety Authority
Available from: 2017-08-03 Created: 2017-08-03 Last updated: 2018-04-19Bibliographically approved
Branger, E., Grape, S., Jacobsson, S., Jansson, P. & Andersson Sundén, E. (2017). On Cherenkov light production by irradiated nuclear fuel rods. Journal of Instrumentation, 12, Article ID T06001.
Open this publication in new window or tab >>On Cherenkov light production by irradiated nuclear fuel rods
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2017 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 12, article id T06001Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Nuclear safeguards, Geant4, Cherenkov light, DCVD, Nuclear fuel rod
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-309736 (URN)10.1088/1748-0221/12/06/T06001 (DOI)000405090900001 ()
Funder
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011
Available from: 2016-12-07 Created: 2016-12-07 Last updated: 2018-08-17Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3136-5665

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