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Non-destructive Experimental Determination of the Pin-power Distribution in Nuclear Fuel Assemblies
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Nuclear and Particle Physics.
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In: Nuclear Technology, ISSN 0029-5450Article in journal (Refereed) Submitted
URN: urn:nbn:se:uu:diva-91656OAI: oai:DiVA.org:uu-91656DiVA: diva2:164458
Available from: 2004-04-21 Created: 2004-04-21Bibliographically approved
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.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 967
Nuclear physics, tomography, nuclear fuel, SPECT, core physics, validation, pin power, safeguards, partial-defect verification, Kärnfysik
National Category
Subatomic Physics
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
Available from: 2004-04-21 Created: 2004-04-21Bibliographically approved

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