THE UNIVERSITY
OF HONG KONG
DEPARTMENT OF MECHANICAL ENGINEERING
SEMINAR
Title:
The problem of growth in irradiated Zr alloys
Speaker:
Professor Tamás Ungár
School of Materials Performance
The University of Manchester
Manchester, UK
Date:
31 October, 2016 (Monday)
Time:
11:00 a.m.
Venue:
Room 7-37, Haking Wong Building, HKU
Abstract:
Zirconium alloys are widely used by the nuclear industry as fuel cladding
material. However, within the extreme environment of fast neutron
irradiation, high temperature and corrosive cooling media zirconium
claddings exhibit dimensional instabilities as a result of irradiation induced
growth, irradiation enhanced creep and hydrogen pick up [1-3]. These
instabilities can significantly limit the lifetime of fuel assemblies, impacting
on power plant efficiency as well as waste production by requiring more
frequent shutdowns and fuel removal. Many studies have been carried out
to investigate the origin of this dimensional instability, and a correlation
has been observed with the formation of various dislocation structures,
however a mechanistic understanding is still elusive. Recent X-ray
diffraction based substructure characterization either by synchrotron or
laboratory experiments can supplement transmission electron microscopy
investigations. Recent results on dislocation loop formation by both,
neutron and proton irradiated Zr alloys will be presented and discussed to
reveal the present understanding of irradiation damage in Zr alloys used in
the nuclear industry.
1.
2.
3.
Griffiths, M., 2008. Microstructure evolution in Zr alloys during
irradiation: dose, dose rate, and impurity dependence. Journal of ASTM
International, 5(1), pp.19–26.
McGrath, M.A. & Yagnik, S., 2011. Experimental Investigation of
Irradiation Creep and Growth of Recrystallized Zircaloy-4 Guide Tubes
Pre-Irradiated in PWR. In Journal of ASTM International. pp. 875–898.
T. Seymour, P. Franke, L. Balogh, T. Ungár, S.P. Thompson, D. Jädernäs,
J. Romero, L. Hallstadius, M.R. Daymond, G. Ribarik, M. Preuss,
Evolution of dislocation structure in neutron irradiated Zircaloy-2
studied by synchrotron x-ray peak profile analysis, submitted to Acta
Materialia.
*Permanent address: Department of Materials Physics, Eötvös University
Budapest, Budapest, Hungary
Biography:
Tamás Ungár, Professor emeritus
Department of Materials Physics, Eötvös University Budapest, Hungary
PhD in 1980 at the Eötvös University Budapest in Hungary. Postdoctoral
fellow as Humboldt stipend holder at the Max-Planck-Institute of
Metallforschung in Stuttgart Germany with Dr M. Wilkens, Prof. H. Mughrabi
and Prof. A. Seeger. 1988 Dr of Science (DSc) of the Hungarian Academy of
Sciences. 1988 to 2013 Full Professor at Eötvös University Budapest in
Hungary. Since 2013 Professor emeritus at the same University. Research
interest metals, alloys, geological minerals and materials, correlation
between physical properties and microstructure, dislocations, planar
defects, grain and subgrain structure. Characterization of the substructure
by X-ray and neutron diffraction line profile analysis. Hanawalt award from
ICDD in 2007 for the dislocation model of strain anisotropy, Humboldt
Research Prize in 2008/2009. Visiting professor at ETH Zurich 1991-92,
and City University Hong Kong 2013-2014. Research Fellow at the School of
Materials Performance at the University of Manchester, Manchester, UK,
2016-2017. Four former PhD students now department chairs. Published
about 240 research papers, over 6000 citations, H number 43.
ALL INTERESTED ARE WELCOME
For further information, please contact Dr. M.X. Huang at 3917 7906.
Research areas: Advanced Materials and Energy