THE BEHAVIOR OF ZrO
WITH MOLTEN IRON AT HIGH TEMPERATURES
T. I. Borodina,
G. E. Val’yano,
E. P. Pakhomov,
V. É. Peletskii,
and Z. Helmann
Translated from Ogneupory i Tekhnicheskaya Keramika, Nos.7–8,pp.25–34,July – August, 2002.
It is shown that in a system of molten Fe(Cr, Ni) and zirconia in an atmosphere of argon at temperatures of up
to about 2900 K no chemical reaction occurs; still, at 2510 – 2700 K, zirconia converts to a viscous mobile
mass that is expelled to float by the heavier molten metal. It is suggested that this behavior is associated with
the partial reduction of zirconia to a nonstoichiometric state ZrO
. Movement of the molten metal in the
crucible is discussed allowing for the specific energy distribution in a high-frequency field.
Over the past decades, providing for higher safety of
both long-in-service and newly constructed nuclear power
plants (encompassing around 400 energy units in 26 coun-
tries over the world) has become an issue of urgent concern.
In particular, the ever-increasing requirements placed on en-
vironmental protection prohibit the release of radioactive
materials from a damaged reactor even serious accidents at
nuclear power plants.
As a means of preventing nuclear-reactor accidents, a
special technical facility (a trap) should be provided for re
taining 100 – 200 tons of a high-temperature molten oxide-
metal material composed of UO
+ Fe(Cr, Ni) +
Zr + Fe(Cr, Ni)O
An analysis has shown that the best and practically the
only protective material suitable for this purpose is zirco
nium dioxide (zirconia) with main characteristics T
3000 K, E
= 1100 kJ/mole, T
= 4600 K, g»6g/cm
, and cost around $10 per kg.
STATEMENT OF PROBLEM
This work is concerned with a study of the resistance of
) to the molten core, in particular to its metal
lic part mostly represented by the iron.
It was shown in  that neither Fe nor Fe(Cr, Ni) in an
inert atmosphere are capable of chemically reacting with
at temperature up to the ZrO
melting point (2980 K) or
even higher (in the liquid phase). A similar result was ob-
tained for the binder barium-strontium monoaluminate
(henceforth denoted for brevity BA (or SA))
that was developed for zirconia-based hydrated concrete
(ZHC) — a fabricable heat-resistant material for lining
These results were obtained during out high high-tem-
perature tests (over 2000 K) with a duration of 15 – 30 min
— as it turned out, a basically important circumstance.
In the subsequent tests for chemical interaction between
molten Fe(Cr, Ni) and ZrO
kept in contact for a longer time
(2 – 10 h) it was established, indeed, that no chemical inter
action took place; still, at 2500 – 2700 K in an inert atmo
sphere (argon), the ZrO
-based material converts to a viscous
plastic mass, which sets the stage for a new mechanism of
degradation of components fabricated from this material.
To further test this result, an investigation was carried
out using different compositions of zirconia-based material
(Table 1). The results obtained are considered in some detail
Mixtures of metals of different composition (Table 2)
were heated under high-frequency conditions ( f =40–
70 kHz, N = 60 kW) in non-isothermal crucibles made of zir
conia-based materials containing around 0.5% trace elements
(apart from HfO
). The concrete crucibles were pre-calcined
An inductor with dimensions of Æ 57 ´ 84 mm (nine
coils of a tube 6 mm in diameter were used). The crucible
used had dimensions of Æ 40 ´ 60 mm; it was covered with a
Refractories and Industrial Ceramics Vol. 43, Nos.7–8, 2002
1083-4877/02/0708-0251$27.00 © 2002 Plenum Publishing Corporation
Institute for Thermal Physics of Extreme States, Joint Institute for
High Temperatures, Russian Academy of Sciences, Russia.
Siemens, KWU Department, Germany.