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Modeling defect structure evolution in spent nuclear fuel container materials
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.ORCID iD: 0000-0001-5059-1791
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Materials intended for disposal of spent nuclear fuel require a particular combination of physical and chemical properties. The driving forces and mechanisms underlying the material’s behavior must be scientifically understood in order to enable modeling at the relevant time- and length-scales. The processes that determine the mechanical behavior of copper canisters and iron inserts, as well as the evolution of their mechanical properties, are strongly dependent on the properties of various defects in the bulk copper and iron alloys.

The first part of the present thesis deals with precipitation in the cast iron insert. A nodular cast iron insert will be used as the inner container of the spent nuclear fuel. Precipitation is investigated by computing effective interaction energies for point defect pairs (solute–solute and vacancy–solute) in bcc iron using first-principles calculations. The main considered impurities in the iron matrix include 3sp (Si, P, S) and 3d (Cr, Mn, Ni, Cu) solute elements. By computing interaction energies possibility of formation of different second phase particles such as late blooming phases (LBPs) in the cast iron insert is evaluated.

The second part is devoted to the fundamentals of dislocations and their role in plastic deformation of metals. Deformation of single-crystal copper under high strain rates is simulated by employing dislocation dynamics (DD) method to examine the effect of strain rate on mechanical properties as well as dislocation microstructure development.

Creep deformation of copper canister at low temperatures is studied. The copper canister will be used in the long-term storage of spent nuclear fuel as the outer shell of the waste package to provide corrosion protection. A glide rate is derived based on the assumption that at low temperatures it is controlled by the climb rate of jogs on the dislocations. Using DD simulation creep deformation of copper at low temperatures is modeled by taking glide but not climb into account. Moreover, effective stresses acting on dislocations are computed using the data extracted from DD simulations.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , 51 p.
Keyword [en]
Cast iron insert, First principles calculations, Point defects, Effective interaction energy, Late blooming phase, Dislocation dynamics, High strain rate deformation, Single-crystal copper, Copper canister, Creep, Glide
National Category
Materials Engineering
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-206175ISBN: 978-91-7729-379-8 (print)OAI: oai:DiVA.org:kth-206175DiVA: diva2:1091696
Public defence
2017-06-02, Sal B2, Brinellvägen 23, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170428

Available from: 2017-04-28 Created: 2017-04-27 Last updated: 2017-04-28Bibliographically approved
List of papers
1. Dislocation dynamics modeling of plastic deformation in single-crystal copper at high strain rates
Open this publication in new window or tab >>Dislocation dynamics modeling of plastic deformation in single-crystal copper at high strain rates
2016 (English)In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 107, no 11, 988-995 p.Article in journal (Refereed) Published
Abstract [en]

Tensile deformation of single-crystal copper along [001] orientation is modeled. Single crystal is deformed at three sets of high strain rates, ranging from 10(3) to 10(5) s(-1), using the three-dimensional dislocation dynamics technique to simulate dislocation microstructure evolution and the resultant macroscopic response. Two initial dislocation configurations consisting of straight dislocations and Frank-Read sources are randomly distributed over the simulation volume with an edge length of 1 mu m. For both initial setups, the mechanical response of the single crystal to the external loading demonstrates a considerable effect of strain rate. In addition, strain rate influences dislocation density evolution and consequently development of the dislocation microstructure. At all applied strain rates for both initial dislocation setups, dislocations evolve into a heterogeneous microstructure and this heterogeneity increases with plastic strain and strain rate.

Place, publisher, year, edition, pages
Carl Hanser Verlag GmbH, 2016
Keyword
Dislocation dynamics, Single-crystal copper, High strain rate deformation, Strain rate effect, Heterogeneous microstructure
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-197777 (URN)10.3139/146.111433 (DOI)000387884000002 ()2-s2.0-84994479646 (Scopus ID)
Note

QC 20161228

Available from: 2016-12-28 Created: 2016-12-08 Last updated: 2017-04-27Bibliographically approved
2. First-principles study of interactions between substitutional solutes in bcc iron
Open this publication in new window or tab >>First-principles study of interactions between substitutional solutes in bcc iron
Show others...
2016 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 475, 140-148 p.Article in journal (Refereed) Published
Abstract [en]

Using density functional theory based calculations, employing the locally self-consistent Green's function method and the projected augmented wave method, we develop a database of solute-solute interactions in dilute alloys of bcc Fe. Interactions within the first three coordination shells are computed for the ferromagnetic state as well as for the paramagnetic (disordered local moment) state of the iron matrix. The contribution of lattice relaxations to the defect interaction energy is investigated in the ferromagnetic state. Implications of the obtained results for modeling the phenomena of point defect clustering and phase precipitation in bcc Fe-based alloys and steel are discussed.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Ab initio calculations, Interactions, Iron, Substitutional defects
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-186909 (URN)10.1016/j.jnucmat.2016.04.013 (DOI)000377307300017 ()2-s2.0-84963625913 (Scopus ID)
Funder
Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning
Note

Funding Details: SKB, Swedish Nuclear Fuel and Waste Management Company

QC 20160518

Available from: 2016-05-18 Created: 2016-05-16 Last updated: 2017-04-27Bibliographically approved
3. The role of glide during creep of copper at low temperatures
Open this publication in new window or tab >>The role of glide during creep of copper at low temperatures
(English)Manuscript (preprint) (Other academic)
Keyword
creep, dislocation dynamics, glide, internal stress
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-206209 (URN)
Note

QC 20170428

Available from: 2017-04-28 Created: 2017-04-28 Last updated: 2017-04-28Bibliographically approved
4. Ab-initio based search for late blooming phase compositions in iron alloys
Open this publication in new window or tab >>Ab-initio based search for late blooming phase compositions in iron alloys
(English)Manuscript (preprint) (Other academic)
Keyword
iron alloys, ab initio calculation, solute clusters, precipitate phases
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-206206 (URN)
Note

QC 20170428

Available from: 2017-04-28 Created: 2017-04-28 Last updated: 2017-04-28Bibliographically approved

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