Verification and Determination of the Decay Heat in Spent PWR Fuel by Means of Gamma Scanning

Osifo, Otasowie; Svärd, Staffan Jacobsson; Håkansson, Ane; Willman, Christofer; Bäcklin, A.; Lundqvist, Tobias

doi:10.13182/nse160-129tn

Cited by 4 publications

(2 citation statements)

References 6 publications

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“…the residual heat and burnup [1] and the International Atomic Energy Agency (IAEA) must be assured that the information on the nuclear material is correct before the encapsulation since it will not be easily accessible afterwards [2]. At present, the IAEA has identified a need for new measuring techniques [3], e.g.…”

Section: Verification Of Fuel Assemblies' Completenessmentioning

confidence: 99%

Applicability of a set of tomographic reconstruction algorithms for quantitative SPECT on irradiated nuclear fuel assemblies

Svärd

Holcombe

Grape

2015

Nuclear Instruments and Methods in Physics Research Section A:

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a b s t r a c tA fuel assembly operated in a nuclear power plant typically contains 100-300 fuel rods, depending on fuel type, which become strongly radioactive during irradiation in the reactor core. For operational and security reasons, it is of interest to experimentally deduce rod-wise information from the fuel, preferably by means of non-destructive measurements. The tomographic SPECT technique offers such possibilities through its two-step application; (1) recording the gamma-ray flux distribution around the fuel assembly, and (2) reconstructing the assembly's internal source distribution, based on the recorded radiation field. In this paper, algorithms for performing the latter step and extracting quantitative relative rod-by-rod data are accounted for.As compared to application of SPECT in nuclear medicine, nuclear fuel assemblies present a much more heterogeneous distribution of internal attenuation to gamma radiation than the human body, typically with rods containing pellets of heavy uranium dioxide surrounded by cladding of a zirconium alloy placed in water or air. This inhomogeneity severely complicates the tomographic quantification of the rod-wise relative source content, and the deduction of conclusive data requires detailed modelling of the attenuation to be introduced in the reconstructions. However, as shown in this paper, simplified models may still produce valuable information about the fuel.Here, a set of reconstruction algorithms for SPECT on nuclear fuel assemblies are described and discussed in terms of their quantitative performance for two applications; verification of fuel assemblies' completeness in nuclear safeguards, and rod-wise fuel characterization. It is argued that a request not to base the former assessment on any a priori information brings constraints to which reconstruction methods that may be used in that case, whereas the use of a priori information on geometry and material content enables highly accurate quantitative assessment, which may be particularly useful in the latter application.Two main classes of algorithms are covered; (1) analytic filtered back-projection algorithms, and (2) a group of model-based or algebraic algorithms. For the former class, a basic algorithm has been implemented, which does not take attenuation in the materials of the fuel assemblies into account and which assumes an idealized imaging geometry. In addition, a novel methodology has been presented for introducing a first-order correction to the obtained images for these deficits; in particular, the effects of attenuation are taken into account by modelling the response for an object with a homogeneous mix of fuel materials in the image area. Neither the basic algorithm, nor the correction method requires prior knowledge of the fuel geometry, but they result in images of the assembly's internal activity distribution. Image analysis is then applied to deduce quantitative information.Two algebraic algorithms are also presented, which model attenuation in the fuel assemblies to different degrees...

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Section: Verification Of Fuel Assemblies' Completenessmentioning

confidence: 99%

Applicability of a set of tomographic reconstruction algorithms for quantitative SPECT on irradiated nuclear fuel assemblies

Svärd

Holcombe

Grape

2015

Nuclear Instruments and Methods in Physics Research Section A:

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“…Burn-up 1.2% to 4% Willman et al (2006), Osifo et al (2008), Guardini (2004) Cooling Time 1.5% to 4% Willman et al (2006), Osifo et al (2008), Guardini (2004) Decay heat 2% to 3% Simpson et al (2008), Jansson (2002), Osifo et al (2008) Initial enrichment <1% (~25% of 235 U content) Min et al (1988) From a Clink planning perspective it is important to keep in mind the need for calibration of the passive gamma and gamma tomography methods to be able to determine decay heat. The calibration procedure includes both calorimetric measurements, of which some have been performed already, and measurements with passive gamma or gamma tomography in the measurement geometry to be used at the facility.…”

Section: Parameter Uncertainty Referencesmentioning

confidence: 99%

Nondestructive Assay Options for Spent Fuel Encapsulation

Tobin

Jansson

2014

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This report describes the role that nondestructive assay (NDA) techniques and systems of NDA techniques may have in the context of an encapsulation and deep geological repository. The potential NDA needs of an encapsulation and repository facility include safeguards, heat content, and criticality. Some discussion of the facility needs is given, with the majority of the report concentrating on the capability and characteristics of individual NDA instruments and techniques currently available or under development. Particular emphasis is given to how the NDA techniques can be used to determine the heat production of an assembly, as well as meet the dual safeguards needs of 1) determining the declared parameters of initial enrichment, burn-up, and cooling time and 2) detecting defects (total, partial, and bias). The report concludes with the recommendation of three integrated systems that might meet the combined NDA needs of the encapsulation/repository facility.

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