uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Investigating the Cherenkov light production due to cross-talk in closely stored nuclear fuel assemblies in wet storage
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.ORCID iD: 0000-0001-8207-3462
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.ORCID iD: 0000-0002-5133-6829
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.ORCID iD: 0000-0002-3136-5665
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Show others and affiliations
2017 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
2017.
Keywords [en]
DCVD; partial defect verification; Cherenkov light; Geant4; Cross-talk
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
URN: urn:nbn:se:uu:diva-323613OAI: oai:DiVA.org:uu-323613DiVA, id: diva2:1106869
Conference
2017 ESARDA symposium
Funder
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2018-08-17
In thesis
1. Enhancing the performance of the Digital Cherenkov Viewing Device: Detecting partial defects in irradiated nuclear fuel assemblies using Cherenkov light
Open this publication in new window or tab >>Enhancing the performance of the Digital Cherenkov Viewing Device: Detecting partial defects in irradiated nuclear fuel assemblies using Cherenkov light
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 97
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1708
Keywords
DCVD, Nuclear safeguards, Cherenkov light, Nuclear fuel assembly, Partial defect verification
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-357578 (URN)978-91-513-0415-1 (ISBN)
Public defence
2018-10-12, Room 2005, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Radiation Safety Authority, SSM2012-2750Swedish National Infrastructure for Computing (SNIC), p2007011
Available from: 2018-09-14 Created: 2018-08-17 Last updated: 2018-10-02

Open Access in DiVA

No full text in DiVA

Search in DiVA

By author/editor
Branger, ErikGrape, SophieJansson, PeterAndersson Sundén, ErikJacobsson Svärd, Staffan
By organisation
Applied Nuclear Physics
Subatomic Physics

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 246 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf