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Sintering and characterization of ZrN and (Dy,Zr)N as surrogate materials for fast reactor nitride fuel
KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.ORCID iD: 0000-0003-4136-6458
Japan Energy Agency.
2014 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 444, no 1-3, 7-13 p.Article in journal (Refereed) Published
Abstract [en]

Pellets of inert matrix material ZrN, and surrogate nitride fuel material (Dy0.4Zr0.6)N, are fabricated for the purpose of investigating the origin and the effect of carbon and oxygen impurity concentrations. Oxygen concentrations of up to 1.2 wt% are deliberately introduced into the materials with two separate methods. The achievable pellet densities of these materials, as a function of O content, sintering temperature and dimensional powder properties are determined. O dissolved into (Dy,Zr)N increases the achievable densities to a larger extent than if dissolved into ZrN. The segregation of O-rich phases in ZrN indicates a low O solubility in the material. Oxygen pick-up during the fabrication of the product as well as its exposure to air is demonstrated. The quality of the materials is monitored by the systematic analysis of O, N and C contents throughout the fabrication and sintering processes, supported by XRD and SEM analyses.

Place, publisher, year, edition, pages
2014. Vol. 444, no 1-3, 7-13 p.
Keyword [en]
Effect of carbons, Oxygen concentrations, Oxygen impurity, Powder properties, Sintering process, Sintering temperatures, Surrogate materials, Systematic analysis
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-123530DOI: 10.1016/j.jnucmat.2013.09.001ISI: 000329888100002ScopusID: 2-s2.0-84885090542OAI: diva2:627110

QC 20140214. Updated from accepted to published.

Available from: 2013-06-11 Created: 2013-06-11 Last updated: 2014-02-14Bibliographically approved
In thesis
1. Experimental and theoretical studies of nitride fuels
Open this publication in new window or tab >>Experimental and theoretical studies of nitride fuels
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With respect to nitrides being considered as potential fast reactor fuels, research is conducted on the out-of-pile thermophysical properties, sintering and fabrication processes, gas migration mechanisms, self-diffusion and point defect behaviour of actinide nitrides, their surrogate materials, and the inert matrix material ZrN . The experimental research, carried out in the framework of qualifying fuel for the European Lead Cooled Training Reactor (ELECTRA), shows that sintered ZrN and (Dy,Zr)N pellet densities are influenced by the oxygen concentration in the material. The effect is confirmed in sintered (Pu,Zr)N pellets. Oxygen concentration also plays a role in the thermophysical properties of inert matrix nitride fuels, but does not have an impact on the electrical properties of these materials. With the fuel fabrication methods applied here, clean nitride powders can be synthesized. However, the subsequent fabrication phases, including milling and solid solution formation, increases the impurity levels significantly. Research of equal importance is performed on materials free of fabrication-induced impurities, whose properties are studied by employing first-principles methods. ZrN, UN and (U,Zr)N are studied, whereas the results from ZrN are expected to be applicable for actinide nitrides as a first approximation. The migration of noble gases in ZrN, on the atomic scale, confirms the experimentally observed tendency for noble gases with higher atomic number to be retained in the fuel matrix, while the majority of He is released to the fuel pin. Materials modelling implies that self-diffusion of nitrogen and metal atoms in inert matrix nitride fuels is accelerated under irradiation, since noble gas retention reduces migration barriers which govern self-diffusion. Unlike Kr and Xe, He has the capacity to be released into the fuel matrix, after having been trapped in a vacancy. The results are expected to aid in providing an explanation to the macroscopic diffusion phenomena in nitride fuels, as the diffusion behaviour of noble gases is sparsely studied. In addition, a study on the miscibility of ZrN and UN in a narrow composition range suggests solubility, based on the negative mixing energies. The results obtained from research on inert matrix nitride fuel underline several beneficial properties which are desirable in a fast reactor fuel. The relevance of these results is analyzed and contextualized in the thesis, from the perspective of current research and development in the field.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. x, 74 p.
Trita-FYS, ISSN 0280-316X ; 12013:18
fast reactor fuel, ab-initio modelling, fuel fabrication, inert matrix nitride fuel
National Category
Condensed Matter Physics
urn:nbn:se:kth:diva-123521 (URN)978-91-7501-794-5 (ISBN)
Public defence
2013-06-14, FD5, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 14:00 (English)

QC 20130611

Available from: 2013-06-11 Created: 2013-06-10 Last updated: 2013-06-11Bibliographically approved

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