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Experimental study of background subtraction in Digital Cherenkov Viewing Device measurements
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.ORCID-id: 0000-0001-8207-3462
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.ORCID-id: 0000-0002-5133-6829
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.ORCID-id: 0000-0002-3136-5665
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.ORCID-id: 0000-0003-3411-7058
2018 (engelsk)Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 13, nr 8, artikkel-id T08008Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
2018. Vol. 13, nr 8, artikkel-id T08008
Emneord [en]
Nuclear safeguards, Cherenkov light, DCVD, Nuclear fuel
HSV kategori
Forskningsprogram
Fysik med inriktning mot kärnfysik
Identifikatorer
URN: urn:nbn:se:uu:diva-357150DOI: 10.1088/1748-0221/13/08/T08008ISI: 000442556100001OAI: oai:DiVA.org:uu-357150DiVA, id: diva2:1238226
Forskningsfinansiär
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011Tilgjengelig fra: 2018-08-13 Laget: 2018-08-13 Sist oppdatert: 2019-08-01bibliografisk kontrollert
Inngår i avhandling
1. Enhancing the performance of the Digital Cherenkov Viewing Device: Detecting partial defects in irradiated nuclear fuel assemblies using Cherenkov light
Åpne denne publikasjonen i ny fane eller vindu >>Enhancing the performance of the Digital Cherenkov Viewing Device: Detecting partial defects in irradiated nuclear fuel assemblies using Cherenkov light
2018 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

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.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2018. s. 97
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1708
Emneord
DCVD, Nuclear safeguards, Cherenkov light, Nuclear fuel assembly, Partial defect verification
HSV kategori
Forskningsprogram
Fysik med inriktning mot tillämpad kärnfysik
Identifikatorer
urn:nbn:se:uu:diva-357578 (URN)978-91-513-0415-1 (ISBN)
Disputas
2018-10-12, Room 2005, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (engelsk)
Opponent
Veileder
Forskningsfinansiär
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011
Tilgjengelig fra: 2018-09-14 Laget: 2018-08-17 Sist oppdatert: 2018-10-02

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