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Håkansson, A
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Publications (10 of 50) Show all publications
Åberg Lindell, M., Andersson, P., Grape, S., Hellesen, C., Håkansson, A. & Eriksson, M. (2018). Discrimination of irradiated MOX fuel from UOX fuel by multivariate statistical analysis of simulated activities of gamma-emitting isotopes. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 885, 67-78
Open this publication in new window or tab >>Discrimination of irradiated MOX fuel from UOX fuel by multivariate statistical analysis of simulated activities of gamma-emitting isotopes
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2018 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 885, p. 67-78Article in journal (Refereed) Published
Abstract [en]

This paper investigates how concentrations of certain fission products and their related gamma-ray emissions can be used to discriminate between uranium oxide (UOX) and mixed oxide (MOX) type fuel. Discrimination of irradiated MOX fuel from irradiated UOX fuel is important in nuclear facilities and for transport of nuclear fuel, for purposes of both criticality safety and nuclear safeguards. Although facility operators keep records on the identity and properties of each fuel, tools for nuclear safeguards inspectors that enable independent verification of the fuel are critical in the recovery of continuity of knowledge, should it be lost. A discrimination methodology for classification of UOX and MOX fuel, based on passive gamma-ray spectroscopy data and multivariate analysis methods, is presented. Nuclear fuels and their gamma-ray emissions were simulated in the Monte Carlo code Serpent, and the resulting data was used as input to train seven different multivariate classification techniques. The trained classifiers were subsequently implemented and evaluated with respect to their capabilities to correctly predict the classes of unknown fuel items. The best results concerning successful discrimination of UOX and MOX-fuel were acquired when using non-linear classification techniques, such as the k nearest neighbors method and the Gaussian kernel support vector machine. For fuel with cooling times up to 20 years, when it is considered that gamma-rays from the isotope  134Cs can still be efficiently measured, success rates of 100% were obtained. A sensitivity analysis indicated that these methods were also robust.

Keywords
Spent nuclear fuel, MOX, Gamma spectroscopy, Multivariate analysis, Classification
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-337676 (URN)10.1016/j.nima.2017.12.020 (DOI)000424740800009 ()
Funder
Swedish Research Council, VR 621-2009-3991Swedish Radiation Safety Authority, SSM2016-661
Available from: 2018-01-03 Created: 2018-01-03 Last updated: 2018-04-19Bibliographically approved
Wolniewicz, P., Håkansson, A. & Jansson, P. (2015). Detection of coolant void in lead-cooled fast reactors. Annals of Nuclear Energy, 85, 1096-1103
Open this publication in new window or tab >>Detection of coolant void in lead-cooled fast reactors
2015 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 85, p. 1096-1103Article in journal (Refereed) Published
Abstract [en]

Previous work (Wolniewicz et al., 2013) has indicated that using fission chambers coated with 242Pu and 235U, respectively, can provide the means of detecting changes in the neutron flux that are connected to coolant density changes in a small lead-cooled fast reactor. Such density changes may be due to leakages of gas into the coolant, which, over time, may coalesce to large bubbles implying a high risk of causing severe damage of the core. By using the ratio of the information provided by the two types of detectors a quantity is obtained that is sensitive to these density changes and, to the first order approximation, independent of the power level of the reactor.

In this work we continue the investigation of this proposed methodology by applying it to the Advanced LFR European Demonstrator (ALFRED) and using realistic modelling of the neutron detectors. The results show that the methodology may be used to detect density changes indicating the initial stages of a coalescence process that may result in a large bubble. Also, it is shown that under certain circumstances, large bubbles passing through the core could be detected with this methodology.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-260230 (URN)10.1016/j.anucene.2015.07.027 (DOI)000361413800116 ()
Funder
Swedish Research Council
Available from: 2015-08-18 Created: 2015-08-18 Last updated: 2017-12-04Bibliographically approved
Håkansson, A., Ottosson, J., Qvist, S., Grape, S., Hellesen, C., Lantz, M. & Pomp, S. (2014). IPCC förordar kärnkraft för att minska utsläppen. Svenska Dagbladet (SvD), 11 nov
Open this publication in new window or tab >>IPCC förordar kärnkraft för att minska utsläppen
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2014 (Swedish)In: Svenska Dagbladet (SvD), Vol. 11 novArticle in journal, News item (Other (popular science, discussion, etc.)) Published
National Category
Social Sciences
Identifiers
urn:nbn:se:uu:diva-235820 (URN)
Available from: 2014-11-11 Created: 2014-11-11 Last updated: 2018-04-19Bibliographically approved
Håkansson, A., Davour, A., Grape, S., Hellesen, C., Höök, M., Lantz, M., . . . Qvist, S. (2014). Svensk elförsörjning i framtiden – en fråga med globala dimensioner: En tvärvetenskaplig rapport från Uppsala universitet. Uppsala
Open this publication in new window or tab >>Svensk elförsörjning i framtiden – en fråga med globala dimensioner: En tvärvetenskaplig rapport från Uppsala universitet
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2014 (Swedish)Report (Other academic)
Place, publisher, year, edition, pages
Uppsala: , 2014. p. 66
National Category
Economic History Subatomic Physics
Research subject
Physics with specialization in Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-233392 (URN)
Available from: 2014-10-02 Created: 2014-10-02 Last updated: 2015-01-08Bibliographically approved
Hellesen, C., Wolniewicz, P., Jansson, P., Håkansson, A., Jacobsson Svärd, S. & Österlund, M. (2014). Transient Simulation of Gas Bubble in a Medium Sized Lead Cooled Fast Reactor. In: Kenya Suyama, Takanori Sugawara, Kenichi Tada, Go Chiba and Akio Yamamoto (Ed.), Proceedings of the International Conference on Physics of Reactors (PHYSOR 2014): . Paper presented at International Conference on Physics of Reactors(PHYSOR 2014),September 28-October 3, 2014, Kyoto, Japan.
Open this publication in new window or tab >>Transient Simulation of Gas Bubble in a Medium Sized Lead Cooled Fast Reactor
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2014 (English)In: Proceedings of the International Conference on Physics of Reactors (PHYSOR 2014) / [ed] Kenya Suyama, Takanori Sugawara, Kenichi Tada, Go Chiba and Akio Yamamoto, 2014Conference paper (Other academic)
Abstract [en]

A common problem for many liquid metal cooled fast reactor designs is the positive void worth of the coolant. In this context, an advantage of lead cooled fast reactors is the high temperature of coolant boiling. In contrast to sodium cooled fast reactors this, in practice, precludes coolant boiling. However, partial voiding of the core could result from e.g. gas bubbles entering the core from below. This would introduce a positive reactivity, if the bubble is large enough.

 

In this paper we model this type of event using a point kinetics code coupled to a heat transport code. The reactivity parameters are obtained from a Monte Carlo code. The 300 MWth reactor design Alfred is used as a test case. We show that in general the reactor design studied is robust in such events, and we conclude that small bubbles a measureable Power oscillation would occur. For very large bubbles there exist a possibility of core damage. The cladding is the most sensitive part.

National Category
Energy Systems
Identifiers
urn:nbn:se:uu:diva-232238 (URN)
Conference
International Conference on Physics of Reactors(PHYSOR 2014),September 28-October 3, 2014, Kyoto, Japan
Available from: 2014-09-15 Created: 2014-09-15 Last updated: 2018-02-14Bibliographically approved
Jansson, P., Grape, S., Jacobsson Svärd, S. & Håkansson, A. (2013). A laboratory device for developing analysis tools and methods for gamma emission tomography of nuclear fuel. In: : . Paper presented at The 35th ESARDA Annual Meeting.
Open this publication in new window or tab >>A laboratory device for developing analysis tools and methods for gamma emission tomography of nuclear fuel
2013 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Tomography is a measurement technique that images the inner parts of objects using only external measurement. It is widely used within the field of medicine, and may become important also for nuclear fuel verification where inspectors can obtain information from fuel assemblies’ inner sections without dismantling them.

At Uppsala University, Sweden, a laboratory device has been built for investigating the tomographic measurement techniques on nuclear fuel. The device is composed of machinery to position model fuelrods, activated with Cs-137, in a fuel assembly pattern according to the user's choice. The gamma radiation from the model fuel assembly is collimated to a set of detectors that record the radiation intensity in various positions around the fuel model. Reconstruction of the gamma activity distribution within the fuel model is performed off-line.

The objective for constructing the laboratory device was to support the development of tomographic techniques for nuclear fuel diagnostics as well as for nuclear safeguards purposes. The device allows for evaluating the performance of different data-acquisition setups, measurement schemes and reconstruction algorithms, since the activity content of each fuel rod is well known.

For safeguards purposes, the device is unique in its capability to model various fuel geometries and configurations of partial defects. The latter includes removed, empty and substituted fuel rods. It is well suited for developing tomographic techniques that are optimized for partial defect detection. It also allows for development of analysis tools necessary to quantify detection limits.

Here, we describe the capabilities of the laboratory device and elaborate on how the device may be used to support the nuclear safeguards community with the development of unattended gamma emission tomography.

Keywords
safeguards, gamma emission tomography, nuclear fuel, partial defect, tomographic algorithms
National Category
Subatomic Physics
Research subject
Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-200707 (URN)
Conference
The 35th ESARDA Annual Meeting
Available from: 2013-06-03 Created: 2013-06-03 Last updated: 2018-04-19
Åberg Lindell, M., Grape, S., Håkansson, A. & Jacobsson Svärd, S. (2013). Assessment of proliferation resistances of aqueous reprocessing techniques using the TOPS methodology. Annals of Nuclear Energy, 62, 390-397
Open this publication in new window or tab >>Assessment of proliferation resistances of aqueous reprocessing techniques using the TOPS methodology
2013 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 62, p. 390-397Article in journal (Refereed) Published
Abstract [en]

The aim of this study is to assess and compare the proliferation resistances (PR) of three possible Generation IV lead-cooled fast reactor fuel cycles, involving the reprocessing techniques Purex, Ganex and a combination of Purex, Diamex and Sanex, respectively. The examined fuel cycle stages are reactor operation, reprocessing and fuel fabrication. The TOPS methodology has been chosen for the PR assessment, and the only threat studied is the case where a technically advanced state diverts nuclear material covertly.

According to the TOPS methodology, the facilities have been divided into segments, here roughly representing the different forms of nuclear material occurring in each examined fuel cycle stage. For each segment, various proliferation barriers have been assessed.

The results make it possible to pinpoint where the facilities can be improved. The results show that the proliferation resistance of a fuel cycle involving recycling of minor actinides is higher than for the traditional Purex reprocessing cycle. Furthermore, for the purpose of nuclear safeguards, group actinide extraction should be preferred over reprocessing options where pure plutonium streams occur. This is due to the fact that a solution containing minor actinides is less attractive to a proliferator than a pure Pu solution. Thus, the safeguards analysis speaks in favor of Ganex as opposed to the Purex process.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
proliferation resistance, reprocessing, Generation IV, lead-cooled fast reactor
National Category
Other Physics Topics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-205579 (URN)10.1016/j.anucene.2013.06.040 (DOI)000327170800046 ()
Note

Erratum in Annals of Nuclear Energy, 2014:66, pp 61-62, doi: 10.1016/j.anucene.2013.11.044

Available from: 2013-08-20 Created: 2013-08-20 Last updated: 2018-04-19Bibliographically approved
Wolniewicz, P., Hellesen, C., Jacobsson Svärd, S., Jansson, P., Håkansson, A. & Österlund, M. (2013). Detecting neutron spectrum perturbations due to coolant density changes in a small lead-cooled fast nuclear reactor. Annals of Nuclear Energy, 58, 102-109
Open this publication in new window or tab >>Detecting neutron spectrum perturbations due to coolant density changes in a small lead-cooled fast nuclear reactor
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2013 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 58, p. 102-109Article in journal (Refereed) Published
Abstract [en]

The lead-cooled fast reactor (LFR) is one of the nuclear reactor technologies proposed by the Generation IV International Forum (GIF). The lead coolant allows for inherent safety properties attractive from a nuclear safety point of view, but issues related to corrosion of structural materials and the possible positive coolant reactivity coefficient must be addressed before LFRs can be commercially viable. As an example, a small crack in e.g. a heat exchanger can generate a more or less homogeneous distribution of bubbles in the coolant (void) which if unnoticed, has the potential to cause criticality issues. This fact motivated an investigation of a methodology to detect such voids.

The suggested methodology is based on measurements of the “slow” and “fast” parts of the neutron spectrum because these parts respond in different ways to voiding. For detection, it is tentatively assumed that fission chambers loaded with U-235 and Pu-239, respectively, are deployed. To investigate the methodology according to sensitivity and precision, a number of scenarios have been simulated and analysed using the core simulator Serpent.

The results show that the methodology yields a sensitivity of 3% for each per cent unit of void. Assuming typical detection limits of a few per cent this implies the possibility to detect voids down to the order of 1%. From these studies it was also concluded that the positioning of the detectors relative the reactor core is crucial, which may be useful input during the design phase of a reactor in order to achieve an efficient monitoring system.

Keywords
LFR, Monitoring, Fission chamber, Void, Heat exchanger, Neutron spectrum
National Category
Subatomic Physics
Research subject
Applied Nuclear Physics; Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-198748 (URN)10.1016/j.anucene.2013.03.029 (DOI)000320481600016 ()
Available from: 2013-04-24 Created: 2013-04-24 Last updated: 2017-12-06
Wolniewicz, P., Håkansson, A., Jansson, P. & Jacobsson Svärd, S. (2013). Feasibility study of detection of coolant void in liquid metal cooled fast reactors using changes in the neutron spectrum. Nuclear Engineering and Design, 265, 1255-1265
Open this publication in new window or tab >>Feasibility study of detection of coolant void in liquid metal cooled fast reactors using changes in the neutron spectrum
2013 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 265, p. 1255-1265Article in journal (Refereed) Published
Abstract [en]

Formation of coolant void can lead to an increase in reactivity in metal-cooled fast reactors. Accordingly, the ability to detect formation of void and similar phenomena is highly relevant in order to counteract transient behaviour of such a reactor. As this work shows, the energy distribution of the neutron flux in a fast reactor is sensitive to formation of void. For monitoring purposes, this fact suggests the use of fission chambers with different isotopic content and thus different fission threshold energies. In such a way the monitoring system may be tailored in order to fit the purpose to obtain spectral information of the neutron flux.

In this work, simulations have been performed using the Monte-Carlo-based code SERPENT on the ELECTRA reactor design, a 0.5 MWth lead-cooled fast reactor (LFR) planned for in Sweden. The simulations show significant changes in the neutron spectrum due to the formation of void located in specific in-core regions as well as due to a homogeneous core-wide distribution of small bubbles. In an attempt to quantify and to put a number on the spectroscopic changes, the number of neutrons in the high energy region (2–5 MeV) are compared to the number of neutrons in the low-energy region (50–500 keV) and the changes caused by the introduction of void are analyzed. The implications of the findings are discussed.

National Category
Subatomic Physics
Research subject
Applied Nuclear Physics; Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-210980 (URN)10.1016/j.nucengdes.2013.10.015 (DOI)000330085500127 ()
Available from: 2013-11-18 Created: 2013-11-18 Last updated: 2017-12-06
Hellesen, C., Grape, S., Håkansson, A., Jacobsson Svärd, S. & Jansson, P. (2013). Improved proliferation resistance of fast reactor blankets manufactured from spent nuclear fuel. In: : . Paper presented at The 35th ESARDA Annual Meeting.
Open this publication in new window or tab >>Improved proliferation resistance of fast reactor blankets manufactured from spent nuclear fuel
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2013 (English)Conference paper, Published paper (Other academic)
Abstract [en]

In this paper we investigate how a blanket manufactured from recycled light water reactor (LWR)waste, instead of depleted uranium (DU), could potentially improve the non- proliferationcharacteristics. The blanket made from LWR waste would from the start of operation contain a fractionof plutonium isotopes unsuitable for weapons production. As 239Pu is bred in the blanket it istherefore always mixed with the plutonium already present.

We use a Monte Carlo model of the advanced burner test reactor (ABTR) as reference design, andthe proliferation resistance of the blanket material is evaluated for two criteria, spontaneous neutronemission and decay heat. We show that it is possible to achieve a production of plutonium withproliferation resistance comparable to light water reactor waste with a burnup of 50MWd/kg.

Keywords
Fertile blankets, proliferation resistance, fast reactor
National Category
Subatomic Physics
Research subject
Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-200709 (URN)
Conference
The 35th ESARDA Annual Meeting
Available from: 2013-06-03 Created: 2013-06-03 Last updated: 2018-04-19
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