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On-site Gamma-ray Spectroscopic Measurements of Fission Gas Release in Irradiated Nuclear Fuel
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Nuclear and Particle Physics, Nuclear Physics.
2007 (English)In: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 65, no 1, 36-45 p.Article in journal (Refereed) Published
Abstract [en]

An experimental, non-destructive in-pool, method for measuring fission gas release (FGR) in irradiated nuclear fuel has been developed. Using the method, a significant number of experiments have been performed in-pool at several nuclear power plants of the BWR type. The method utilises the 514 keV gamma-radiation from the gaseous fission product Kr-85 captured in the fuel rod plenum volume. A submergible measuring device (LOKET) consisting of an HPGe-detector and a collimator system was utilised allowing for single rod measurements on virtually all types of BWR fuel. A FGR database covering a wide range of burn-ups (up to average rod burn-up well above 60 MWd/kgU), irradiation history, fuel rod position in cross section and fuel designs has been compiled and used for computer code benchmarking, fuel performance analysis and feedback to reactor operators. Measurements clearly indicate the low FGR in more modern fuel designs in comparison to older fuel types.

Place, publisher, year, edition, pages
2007. Vol. 65, no 1, 36-45 p.
Keyword [en]
FGR database, fission gas release (FGR), fuel performance, fuel design, gamma-ray spectroscopy, krypton, LOKET
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-94564DOI: 10.1016/j.apradiso.2006.07.004ISI: 000242678800007OAI: oai:DiVA.org:uu-94564DiVA: diva2:168452
Available from: 2006-05-16 Created: 2006-05-16 Last updated: 2011-05-05Bibliographically approved
In thesis
1. Studies of Nuclear Fuel Performance Using On-site Gamma-ray Spectroscopy and In-pile Measurements
Open this publication in new window or tab >>Studies of Nuclear Fuel Performance Using On-site Gamma-ray Spectroscopy and In-pile Measurements
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Higher target burnups, part length rods and various fuel additives are some examples of this trend. Together with an increasing demand from the public for even safer nuclear power utilisation, this implies an increased focus on various experimental, preferably non-destructive, methods to characterise the fuel.

This thesis focuses on the development and experimental evaluation of such methods. In its first part, the thesis presents a method based on gamma-ray spectroscopy with germanium detectors that have been used at various power reactors in Europe. The aim with these measurements is to provide information about the thermal power distribution within fuel assemblies in order to validate core physics production codes. The early closure of the Barsebäck 1 BWR offered a unique opportunity to perform such validations before complete depletion of burnable absorbers in Gd-rods had taken place. To facilitate the measurements, a completely submersible measuring system, LOKET, was developed allowing for convenient in-pool measurements to be performed.

In its second part, the thesis describes methods that utilise in-pile measurements. These methods have been used in the Halden test-reactor for determination of fission gas release, pellet-cladding interaction studies and fuel development studies.

Apart from the power measurements, the LOKET device has been used for fission gas release (FGR) measurements on single fuel rods. The significant reduction in fission gas release in the modern fuel designs, in comparison with older designs, has been demonstrated in a series of experiments. A FGR database covering a wide range of burnup, power histories and fuel designs has been compiled and used for fuel performance analysis. The fission gas release has been measured on fuel rods with average burnups well above 60 MWd/kgU. The comparison between core physics calculations (PHOENIX-4/POLCA-7) and the in-pool measurements of thermal power indicates that the nodal power can generally be predicted with an accuracy within 4% and the bundle power with an accuracy better than 2%, expressed as rms errors.

In-pile experiments have successfully simulated the conditions that occur in a fuel rod following a primary debris failure, being secondary fuel degradation. It was concluded that massive hydrogen pick-up takes place during the first few days following the primary failure and that a pre-oxidized layer does not function as a barrier towards hydriding in an environment with a very high partial pressure of hydrogen. Another series of in-pile experiments clearly indicate that increased UO2 grain size is an effective way of suppressing fission gas release in LWR fuel up to the burnup level covered (55 MWd/kgUO2).

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 103 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 191
Nuclear physics, fission gas release, nuclear fuel, core physics, gamma-ray spectroscopy, LOKET, thermal power, burnup, fuel failure, validation, cladding, Kärnfysik
urn:nbn:se:uu:diva-6912 (URN)91-554-6582-X (ISBN)
Public defence
2006-06-07, Sal 2001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:30
Available from: 2006-05-16 Created: 2006-05-16Bibliographically approved

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