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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Article
Use of Dopants for Thoria Sintering Temperature Reduction-Characterization of THO2
Author(s)
Hidetoshi Takiishi1, Luis A. Gênova1, Elton D. Cavalheira1, Marycel B. Cotrim2, Wilson Santos2 and Paulo E. O. Lainetti2
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DOI:10.17265/1934-8975/2016.12.004
Affiliation(s)
1. Science and Materials Technology Center–CCTM, Nuclear and Energetic Research Institute (IPEN-CNEN/SP), Av. Prof. Lineu Prestes 2242, São Paulo/SP. CEP 05508-000, Brazil
2. Chemistry and Environment Center–CQMA, Nuclear and Energetic Research Institute (IPEN-CNEN/SP), Av. Prof. Lineu Prestes 2242, São Paulo/SP. CEP 05508-000, Brazil
ABSTRACT
Thorium is nearly three times more abundant than uranium in the Earth’s crust.
Some papers evaluate the thorium resources in Brazil over 1,200,000 metric t. These figures
mean that the country is probably the biggest thorium resource in the world, with
only part of the territory prospected. Nevertheless, Brazil has not a research program
for use of thorium in nuclear reactors, even having dedicated special attention
to the subject in the beginning of its nuclear activities, in the fifties and sixties.
From 1985 until 2003 IPEN operated a pilot plant for thorium nitrate production
and purification, used by Brazilian industry for production of gas mantles. This
facility produced over 170 metric t of thorium nitrate. Despite the non-nuclear
application, the pilot plant was unique in the southern hemisphere. On the other
hand, Brazil has the biggest world niobium resources. The Brazilian thorium and
niobium resources added to the predictable future importance of alternative fissile
materials have motivated this research, since uranium is a finite resource if used
in the present thermal nuclear reactors. Besides this, thorium oxide is an important
nuclear reactor material. It is a refractory oxide and its ceramic fabrication process
involves a very high temperature sintering treatment considering that thoria melting
point is very high (3,650 K). Cations of elements
of the group VB (V, Nb and Ta) have a known effect in the reduction of
thoria sintering temperature. IPEN has initiated an investigation about the use
of niobium as a dopant for thoria sintering temperature reduction. The thoria used
in the research was produced in the IPEN’s pilot plant and different amounts of
niobium oxide (Nb2O5) will be added to thoria
by different routes. The powders will be compressed and the compacted pellets will
be sintered at different temperatures. The influence of the different parameters
in the density of sintered pellets is being investigated. This paper presents the
chemical and physical characterization for the thoria
used in the investigation.
KEYWORDS
Thorium, processing, purification, thoria, dopants, sintering, temperature, reduction.
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