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Nondestructive Fission Gas Measurements by Means of Gamma Spectroscopy and Gamma Tomography
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

There is a continuous need in the nuclear industry to characterize irradiated nuclear fuel rods and assemblies, both for fuel performance and for safeguards purposes, and consequently there are various destructive and nondestructive measurement techniques available to meet this need. Gamma spectroscopy is one such nondestructive technique, which has been extensively used for a variety of fuel characterization applications. Furthermore, gamma tomography – a combination of gamma spectroscopic measurements and tomographic reconstruction – has in recent years been demonstrated as an efficient technique for characterization of irradiated nuclear fuel assemblies on a rod-by-rod basis without the need to dismantle the fuel. This thesis comprises four scientific papers in which novel applications of these two techniques have been developed and evaluated.

The major part of this work has been performed at the Halden Boiling Water Reactor (HBWR), where a gamma tomography measurement system is currently under construction, as presented in this thesis. The methods and evaluations presented in this work are based on the conditions at the HBWR.

Based on gamma spectroscopy, a novel nondestructive method for determining fission gas release which occurs over short irradiation sequences has been developed, comprising the measurement and analysis of short lived isotopes in individual fuel rods. The method has been demonstrated based on gamma-ray spectra recorded from an experimental fuel rod irradiated in the HBWR.

Based on gamma tomography, a novel method for identifying failed fuel rods within a nuclear fuel assembly has also been developed. The method comprises the measurement of gamma rays emitted in the decay of selected fission gas isotopes in the gas plenum region of a fuel assembly, tomographic image reconstruction of the internal source distribution and subsequent analysis of the resulting image in order to determine if any of the fuel rods in the assembly has unexpectedly low activity, indicating that it is a leaking fuel rod. Simulation studies performed for HBWR fuel show highly promising results for gamma rays emitted in the decay of two selected fission gas isotopes.

The methods will be further investigated at the HBWR, by performing dedicated gamma spectroscopy measurements and by using the tomographic measurement system currently under construction.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2012. , 14 p.
National Category
Physical Sciences
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
URN: urn:nbn:se:uu:diva-185551OAI: oai:DiVA.org:uu-185551DiVA: diva2:572226
Presentation
2012-11-15, 13:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2008-5888
Note

Papers III and IV have been submitted for publication and while under review by the publishers they are not available here.

Available from: 2012-11-28 Created: 2012-11-26 Last updated: 2013-03-22Bibliographically approved
List of papers
1. Feasibility of performing Pool-Side Fission Gas Release Measurements on Fuel Rods with Short Decay Time
Open this publication in new window or tab >>Feasibility of performing Pool-Side Fission Gas Release Measurements on Fuel Rods with Short Decay Time
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2011 (English)Conference paper, Published paper (Refereed)
National Category
Other Physics Topics
Research subject
Applied Nuclear Physics; Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-169391 (URN)
Conference
2011 Water Reactor Fuel Performance Meeting (TopFuel)
Available from: 2012-02-28 Created: 2012-02-28 Last updated: 2015-01-19
2. Development of a Gamma Tomography Measurement System for Characterizing Halden Boiling Water Reactor Fuel
Open this publication in new window or tab >>Development of a Gamma Tomography Measurement System for Characterizing Halden Boiling Water Reactor Fuel
2011 (English)Conference paper, Published paper (Other academic)
National Category
Other Physics Topics
Research subject
Applied Nuclear Physics; Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-169392 (URN)
Conference
Enlarged Halden Programme Group Meeting
Available from: 2012-02-28 Created: 2012-02-28 Last updated: 2015-01-19
3. Method For Analyzing Fission Gas Release In Fuel Rods Based On Gamma-Ray Measurements Of Short-Lived Fission Products
Open this publication in new window or tab >>Method For Analyzing Fission Gas Release In Fuel Rods Based On Gamma-Ray Measurements Of Short-Lived Fission Products
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2013 (English)In: Nuclear Technology, ISSN 0029-5450, E-ISSN 1943-7471, Vol. 184, no 1, 96-106 p.Article in journal (Refereed) Published
Abstract [en]

Fission gases are produced as a result of fission reactions in nuclear fuel. Most of these gases remain trapped within the fuel pellets, but some may be released to the fuel rod internal gas volume under certain conditions. This phenomenon of fission gas release is important for fuel performance since the released gases can degrade the thennal properties of the fuel rod. fill gas and contribute to increasing fuel rod internal pressure. Various destructive and nondestructive methods are available for determining the amount of fission gas release; however, the current methods are primarily useful for determining the integrated fission gas release fraction, i.e., the amount of fission gas produced in the fuel that has been released to the free rod volume over the entire lifetime of a nuclear fuel rod. In this work, a method is proposed for determining the fission gas release that occurs during short irradia-tion sequences. The proposed method is based on spectroscopic measurements of gamma rays emitted in the decay of short-lived fission gas isotopes. Determining such sequence-specific fission gas release can be of interest when evaluating the fuel behavior for selected times during irradiation, such as during power ramps. The data obtained in this type of measurement may also be useful for investigating the mechanisms behind fission gas release for fuel at high burnup. The method is demonstrated based on the analysis of experimental gamma-ray spectra previously collected using equipment not dedicated for this purpose; however, the analysis indicates the feasibility of the method. Further evaluation of the method is planned, using dedicated equipment at the Halden Boiling Water Reactor.

Keyword
fission gas release, gamma spectroscopy, nuclear fuel
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-187790 (URN)000325236100007 ()
Available from: 2012-12-10 Created: 2012-12-10 Last updated: 2017-12-07Bibliographically approved
4. Feasibility of identifying leaking fuel rods using gamma tomography
Open this publication in new window or tab >>Feasibility of identifying leaking fuel rods using gamma tomography
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2013 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 57, 334-340 p.Article in journal (Refereed) Published
Abstract [en]

In cases of fuel failure in irradiated nuclear fuel assemblies, causing leakage of fission gasses from a fuel rod, there is a need for reliable non-destructive measurement methods that can determine which rod is failed. Methods currently in use include visual inspection, eddy current, and ultrasonic testing, but additional alternatives have been under consideration, including tomographic gamma measurements.

The simulations covered in this report show that tomographic measurements could be feasible. By measuring a characteristic gamma energy from fission gasses in the gas plenum, the rod-by-rod gamma source distribution within the fuel rod plena may be reconstructed into an image or data set which could then be compared to the predicted distribution of fission gasses, e.g. from the STAV code. Rods with significantly less fission gas in the plenum may then be identified as leakers.

Results for rods with low fission gas release may, however, in some cases be inconclusive since these rods will already have a weak contribution to the measured gamma-ray intensities and for such rods there is a risk that a further decrease in fission gas content due to a leak may not be detectable. In order to evaluate this and similar experimental issues, measurement campaigns are planned using a tomographic measurement system at the Halden Boiling Water Reactor.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-197321 (URN)10.1016/j.anucene.2013.02.020 (DOI)000319643000040 ()
Available from: 2013-03-22 Created: 2013-03-22 Last updated: 2017-12-06Bibliographically approved

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S. Holcombe Licentiate Thesis(1293 kB)340 downloads
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