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Nuclear safeguards evaluation and analysis techniques for application to nuclear fuel material in Generation IV nuclear energy systems
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A new generation of nuclear energy systems called Generation IV is under development to ensure that nuclear power will be a safe, reliable and sustainable energy source for the future. This thesis addresses the challenge of making future nuclear energy systems increasingly resistant to nuclear material diversion attempts.

Several tools have been developed for structured evaluation of a system's resistance to nuclear proliferation, in order to identify areas where nuclear energy systems are the most inherently vulnerable. In this thesis, the TOPS methodology has been applied to three different fuel cycles involving a fast reactor with fuel recycling and fuel fabrication capabilities. The recycling facility, where the fuel is dissolved and undergoes chemical separation, is identified as being particularly vulnerable. Nondestructive measurements for verification of fuel assemblies in the receipt area of the recycling facility are essential, since it is the last opportunity to verify intact fuel items. Moreover, iterative evaluation of proliferation resistance by using two different assessment methodologies – TOPS and PR&PP – as suggested in this thesis, may act as an aid in facility design and for proposing safeguards implementation.

Based on the identified need to measure irradiated fuel assemblies prior to dissolution in the recycling facility, new methods used for analyzing gamma-ray spectroscopy data using multivariate analysis methods have been investigated. Fuel parameters of modeled nuclear fuel have been determined without any reliance on operator-declared data. Nonlinear classifiers, e.g. support vector machines (SVM), have successfully been used for discrimination between uranium oxide fuels and mixed oxide fuels. Cooling time, burnup and initial fissile content have been determined using decision tree and SVM regression. The results are promising and indicate that the nuclear safeguards regime may benefit from using multivariate techniques for data analysis. It must be emphasized, however, that experimental verification of the multivariate analysis techniques is necessary.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. , p. 72
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1617
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:uu:diva-337699ISBN: 978-91-513-0202-7 (print)OAI: oai:DiVA.org:uu-337699DiVA, id: diva2:1172034
Public defence
2018-02-23, Å4001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2018-01-31 Created: 2018-01-09 Last updated: 2018-03-08
List of papers
1. Assessment of proliferation resistances of aqueous reprocessing techniques using the TOPS methodology
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
2. Schematic design and safeguards instrumentation of a Gen IV fuel recycling facility.
Open this publication in new window or tab >>Schematic design and safeguards instrumentation of a Gen IV fuel recycling facility.
2013 (English)Conference paper, Published paper (Other academic)
Abstract [en]

The sustainability criterion for Gen IV systems, inherently presumes the availability of efficient fuel recycling capabilities. Research activities concerning advanced fuel recycling are currently pursued, and one area for such research concerns safeguards aspects of recycling facilities. Since a recycling facility may be considered as sensitive from a non-proliferation perspective, it is important to address these issues early in the design process, according to the principle of Safeguards By Design.

Presented in this paper is a suggested safeguards approach for a fuel recycling facility belonging to a small Gen IV lead-cooled fast reactor system that is under study in Sweden. A schematic design of a small-scale recycling facility, where actinides are separated using group actinide solvent extraction, is put forward. Measurement points are suggested based on available information on the recycling process activities and calculated material flows.

Based on the identified need for measurements in the facility, possible techniques and instrumentation for measurements have been identified with the purpose to provide both inspecting parties and facility operators with necessary information for their respective needs. More generally, this type of analysis may be used to support Safeguards By Design in the planning of new recycling facilities.

Keywords
Gen IV, recycling, group actinide extraction, instrumentation, Safeguards By Design
National Category
Other Physics Topics
Research subject
Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-204141 (URN)
Conference
The 35th ESARDA Annual Meeting
Available from: 2013-07-22 Created: 2013-07-22 Last updated: 2018-01-15
3. Proliferation resistance assessments during the design phase of a fuel recycling facility as a means of reducing proliferation risks
Open this publication in new window or tab >>Proliferation resistance assessments during the design phase of a fuel recycling facility as a means of reducing proliferation risks
2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The sustainability criterion for Gen IV nuclear energy systems inherently presumes the availability of efficient fuel recycling capabilities. One area for research on advanced fuel recycling concerns safeguards aspects of this type of facilities. Since a recycling facility may be considered as sensitive from a non-proliferation perspective, it is important to address these issues early in the design process, according to the principle of Safeguards By Design.

Presented in this paper is a mode of procedure, where assessments of the proliferation resistance (PR) of a recycling facility for fast reactor fuel have been performed so as to identify the weakest barriers to proliferation of nuclear material. Two supplementing established methodologies have been applied; TOPS and PR&PP. The chosen fuel recycling facility belongs to a small Gen IV lead-cooled fast reactor system that is under study in Sweden. A schematic design of the recycling facility, where actinides are separated using solvent extraction, has been examined.

The PR assessment methodologies make it possible to pinpoint areas in which the facility can be improved in order to reduce the risk of diversion. The initial facility design may then be slightly modified and/or safeguards measures may be introduced to reduce the total identified proliferation risk. After each modification of design and/or safeguards implementation, a new PR assessment of the revised system can been carried out. This way, each modification can be evaluated and new ways to further enhance the proliferation resistance can be identified.

This type of iterative procedure may support Safeguards By Design in the planning of new recycling plants and other nuclear facilities.

Keywords
Proliferation resistance, safeguards by design, reprocessing, Generation IV
National Category
Other Physics Topics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-205866 (URN)
Conference
GLOBAL 2013: International Nuclear Fuel Cycle Conference
Available from: 2013-08-23 Created: 2013-08-23 Last updated: 2018-04-19Bibliographically approved
4. Discrimination of irradiated MOX fuel from UOX fuel by multivariate statistical analysis of simulated activities of gamma-emitting isotopes
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
Show others...
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
5. Determination of irradiated nuclear fuel characteristics by nonlinear multivariate regression of simulated gamma-ray emissions
Open this publication in new window or tab >>Determination of irradiated nuclear fuel characteristics by nonlinear multivariate regression of simulated gamma-ray emissions
Show others...
2017 (English)In: Article in journal (Refereed) Submitted
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-337677 (URN)
Available from: 2018-01-03 Created: 2018-01-03 Last updated: 2018-04-19

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