Most pressurized water reactor (PWR) absorber rods are composed of an
Ag–In–Cd (SIC) alloy inside a stainless steel (SS) cladding, themselves
inserted into a Zircaloy tube. During a severe accident, the SIC alloy
which melts at 800 °C does not practically interact with SS. However,
the cladding failure results from its internal pressurization and its
eutectic interaction with Zircaloy and occurs at temperatures greater
than 1200 °C. The subsequent interaction between the SIC melt and the
Zircaloy has a strong impact on the quantities of aerosols released into
the primary circuit and finally on the iodine chemistry. Accurate
knowledge of the Ag–Zr system is a prerequisite to address this issue.
Within this concern, our experimental work is focused both on the
investigation of the Ag–Zr phase diagram and on the determination of the
thermodynamic properties of the intermetallic compounds in the system.
Two intermetallic compounds (AgZr and AgZr2) were identified.
Ag–Zr cast alloys with a Ag/Zr ratio of 1:1 elaborated using an
arc-melting furnace, once annealed, contained only a single phase AgZr.
From metallographic observations, it appears that AgZr2
likely forms by the peritectic reaction from liquid and the bcc (βZr)
phase. The partial enthalpies of solution of silver and zirconium in
aluminum were experimentally determined at 723 °C in order to determine
the enthalpies of formation of the intermetallic compounds. For silver
solution calorimetry in aluminum bath, our measurements were successful
and in agreement with the previous data. Yet, this study shows that
liquid aluminum should not be used as a solvent for zirconium below