Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Helium cluster dissolution in molybdenum
KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.
KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.
2009 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 21, no 33, 335401- p.Article in journal (Refereed) Published
Abstract [en]

Helium retention and diffusion in molybdenum is studied on an atomistic scale with ab initio methods. The thermal stability of helium–vacancy clusters is quantified within the framework of density functional theory. Calculated helium emission rates are used to derive a desorption spectrum which is compared with experimental results. The agreement between the current calculations and available experiments is satisfactory except in the high temperature end of the spectrum. The current results indicate that above 1100 K He migration is assisted by lattice defects such as vacancies, rather than through interstitial diffusion.

Place, publisher, year, edition, pages
2009. Vol. 21, no 33, 335401- p.
Keyword [en]
Ab initio, Atomistic scale, Desorption spectra, Helium clusters, Helium emissions, Helium retention, Helium-vacancy clusters, High temperature, Interstitial diffusion, Lattice defects, Thermal stability
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-10920DOI: 10.1088/0953-8984/21/33/335401ISI: 000268413300014Scopus ID: 2-s2.0-70349097246OAI: oai:DiVA.org:kth-10920DiVA: diva2:232014
Note
QC 20101101Available from: 2009-08-24 Created: 2009-08-19 Last updated: 2012-03-12Bibliographically approved
In thesis
1. Helium in CERMET fuel - binding energies and diffusion
Open this publication in new window or tab >>Helium in CERMET fuel - binding energies and diffusion
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents a first principle approach to model helium diffusionand retention in molybdenum. Results from electron structure calculations within the framework of density functional theory are used to assess parameters in a rate theory model. The model is used to reproduce experimental desorption spectra, which, to a large degree of accuracy, coincide with experimental data in temperature regions relevant for nuclear fuel applications. The models indicate that produced helium will diffuse out into the fuel pin during operation. However, some helium will be trapped in molybdenum vacancies. The amount of trapped helium will largely depend on the fuel operational temperature.

Data presented in the thesis is a first step towards a self consistent dataset of first principle data on helium diffusion in CERMET fuel, one candidate fuel suggested for transmutation of nuclear waste. To realise the use of CERMET fuel, modelling of fuel performance is essential, and to accomplish this, the understanding of helium diffusion and retention in molybdenum is one important aspect.

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 33 p.
Series
Trita-FYS, ISSN 0280-316X ; 2009:27
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-10933 (URN)978-91-7415-353-5 (ISBN)
Presentation
2009-08-21, Sal FA31, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-08-25 Created: 2009-08-25 Last updated: 2010-11-02Bibliographically approved
2. Helium Filled Bubbles in Solids: Nucleation, Growth and Swelling
Open this publication in new window or tab >>Helium Filled Bubbles in Solids: Nucleation, Growth and Swelling
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Heliumfyllda bubblor i fasta material : Kärnbildning, tillväxt och svällning
Abstract [en]

When nuclear fuel, fabricated for the purpose of transmuting spent fuel is irradiated, significant amounts of He is produced from alpha particles mainly emitted when 242Cm decays into 238Pu. From irradiation experiments it is known that the presence of He in the solids alters the swelling behaviour of the material. The thesis presents the theoretical background from which nucleation models of He bubbles can be formulated. Such models are presented for He in metals, and the case of He in Mo is studied as an example. MgO, which together with Mo is suggested as a matrix material in transmutation fuel is also studied and the stability of He containing bubbles in this material is discussed.

By calculating parameters for a rate theory model derived from atomistic modelling, it is shown that He can stabilise vacancy clusters and cause cluster growth at temperatures and irradiation doses where nucleation and growth would not otherwise occur. At the initial stages of nucleation He can stabilise small bubbles while larger bubbles are unstable. This results in an incubation time of swelling, which implies that He does not always cause increased swelling, but can at certain irradiation conditions slow down the growth of large vacancy clusters and thereby delay swell\-ing beyond the time of the irradiation.

When comparing the behaviour of bubble nucleation in Mo and MgO, it is found that He has a significant impact even at very low concentrations in Mo. In contrast, the concentration of He has to be considerably higher in MgO to affect the swelling behaviour. For an inert matrix fuel, designed for transmutation purposes, this implies that the Mo matrix will have a tendency to swell considerably at rather high temperatures due to He stabilised vacancy clusters. If operated at lower temperatures, the swelling could instead be reduced due to the incubation time. In a MgO matrix, the swelling behaviour will instead depend largely on the production rate of He. For a low production rate, the material will have a swelling behaviour similar to the one seen when He is not present in the material. A high production rate implies that He will remain in vacancy clusters, thereby stabilising the clusters and enhancing the growth and swelling.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 83 p.
Series
Trita-FYS, ISSN 0280-316X ; 2012:06
Keyword
Helium, Radiation Damage, DFT, molybdenum, MgO
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-90960 (URN)978-91-7501-263-6 (ISBN)
Public defence
2012-04-04, F3, Lindstedtsvägen 23, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2012-03-12 Created: 2012-03-05 Last updated: 2012-03-12Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Runevall, OddSandberg, Nils
By organisation
Reactor Physics
In the same journal
Journal of Physics: Condensed Matter
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 60 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf