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Tomography for partial-defect verification: experiences from measurements using different devices
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Nuclear and Particle Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Radiation Sciences.ORCID iD: 0000-0002-3136-5665
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2006 (English)In: ESARDA Bulletin, ISSN 0392-3029, Vol. 33, 15-25 p.Article in journal (Refereed) Published
Abstract [en]

Three devices of different types have been used in tomographic measurements for the purpose of partial-defect verification on the single-rod level. The devices range from a laboratory device used in measurements on a fuel model to an in-pool device used in measurements on irradiated fuel in a fuel-handling pool.

The tomographic technique accounted for in this paper involves measurements of the gamma-ray flux distribution around a fuel assembly followed by computer-aided reconstruction of the internal source distribution. The results are rod-by-rod values of the relative concentrations of selected gamma-emitting isotopes. Also cross-sectional images are obtained.

The tomographic technique presented here has proven to be robust and reliable. In laboratory experiments on a fuel model, reconstructions of relative rod-by-rod activities have been obtained with 1.5 % accuracy (1 σ). Using an in-pool device in measurements on fuel with a cooling time of about 4 weeks, data on fuel rods have been obtained in agreement with production-code calculations. Furthermore, tomographic images of good quality have been acquired.

The applicability of the tomographic technique for partial-defect verification on the single-rod level has been investigated and demonstrated. The gamma-ray source concentration reconstructed in a position corresponding to a removed or replaced rod has been significantly lower than that of normal rods.

Finally, requirements and properties of a device for tomographic measurements on nuclear fuel are discussed. It is argued that the use of a detector system with high energy resolution and high peak efficiency in connection to spectroscopic peak analysis is beneficial.

Place, publisher, year, edition, pages
2006. Vol. 33, 15-25 p.
Keyword [en]
tomography
National Category
Subatomic Physics
Research subject
Applied Nuclear Physics; Physics with specialization in Applied Nuclear Physics
Identifiers
URN: urn:nbn:se:uu:diva-91654OAI: oai:DiVA.org:uu-91654DiVA: diva2:164456
Available from: 2004-04-21 Created: 2004-04-21 Last updated: 2017-01-21
In thesis
1. A Tomographic Measurement Technique for Irradiated Nuclear Fuel Assemblies
Open this publication in new window or tab >>A Tomographic Measurement Technique for Irradiated Nuclear Fuel Assemblies
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The fuel assemblies used at the Swedish nuclear power plants contain typically between 100 and 300 fuel rods. An experimental technique has been demanded for determining the relative activities of specific isotopes in individual fuel rods without dismantling the assemblies. The purpose is to validate production codes, which requires an experimental relative accuracy of <2 % (1 σ).

Therefore, a new, non-destructive tomographic measurement technique for irradiated nuclear fuel assemblies has been developed. The technique includes two main steps: (1) the gamma-ray flux distribution around the assembly is recorded, and (2) the interior gamma-ray source distribution in the assembly is reconstructed. The use of detailed gamma-ray transport calculations in the reconstruction procedure enables accurate determination of the relative rod-by-rod source distribution.

To investigate the accuracy achievable, laboratory equipment has been constructed, including a fuel model with a well-known distribution of 137Cs. Furthermore, an instrument has been constructed and built for in-pool measurements on irradiated fuel assemblies at nuclear power plants.

Using the laboratory equipment, a relative accuracy of 1.2 % was obtained (1 σ). The measurements on irradiated fuel resulted in a repeatability of 0.8 %, showing the accuracy that can be achieved using this instrument. The agreement between rod-by-rod data obtained in calculations using the POLCA–7 production code and measured data was 3.1 % (1 σ).

Additionally, there is a safeguards interest in the tomographic technique for verifying that no fissile material has been diverted from fuel assemblies, i.e. that no fuel rods have been removed or replaced. The applicability has been demonstrated in a measurement on a spent fuel assembly. Furthermore, detection of both the removal of a rod as well as the replacement with a non-active rod has been investigated in detail and quantitatively established using the laboratory equipment.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 85 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 967
Keyword
Nuclear physics, tomography, nuclear fuel, SPECT, core physics, validation, pin power, safeguards, partial-defect verification, Kärnfysik
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-4227 (URN)91-554-5944-7 (ISBN)
Public defence
2004-05-14, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 09:30
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Available from: 2004-04-21 Created: 2004-04-21Bibliographically approved

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Jacobsson Svärd, StaffanJansson, Peter

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