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Branger, E., Grape, S., Jansson, P. & Jacobsson Svärd, S. (2019). On the inclusion of light transport in prediction tools for Cherenkov light intensity assessment of irradiated nuclear fuel assemblies. Journal of Instrumentation, 14, Article ID T01010.
Open this publication in new window or tab >>On the inclusion of light transport in prediction tools for Cherenkov light intensity assessment of irradiated nuclear fuel assemblies
2019 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, article id T01010Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Nuclear safeguards, Geant4, Cherenkov light, DCVD, Nuclear fuel
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-357151 (URN)10.1088/1748-0221/14/01/T01010 (DOI)000457930800001 ()
Funder
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011
Available from: 2018-08-13 Created: 2018-08-13 Last updated: 2019-03-05Bibliographically approved
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
Branger, E., Grape, S., Jansson, P. & Jacobsson, S. (2018). Improved Cherenkov Light Prediction Model for Enhanced DCVD Performance. In: : . Paper presented at IAEA Symposium on International Safeguards: Building Future Safeguards Capabilities 5–8 November 2018, Vienna, Austria.
Open this publication in new window or tab >>Improved Cherenkov Light Prediction Model for Enhanced DCVD Performance
2018 (English)Conference paper, Published paper (Other academic)
Abstract [en]

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.

Keywords
DCVD, Nuclear Fuel, Nuclear Safeguards
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-367334 (URN)
Conference
IAEA Symposium on International Safeguards: Building Future Safeguards Capabilities 5–8 November 2018, Vienna, Austria
Funder
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011
Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2019-03-07Bibliographically 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
Show others...
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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3136-5665

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