Release Behaviors of Elements from an Ag-In-Cd Control Rod Alloy at Temperatures up to 1673 K

A control rod alloy composed of silver (Ag), indium (In), and cadmium (Cd) was heated in argon or oxygen at 1073 to 1673 K for 60 to 3600 s. Then, the release behaviors of the elements were analyzed. The elemental release was quite limited below the liquefaction temperature. In argon, almost the entire Cd content was released within 3600 s at >1173 K and within 60 s at >1573 K while the released fractions of Ag and In were <3% and <8%, respectively. In oxygen, the release of Cd, which was quite small at temperatures lower than 1573 K, largely increased to similar to 30% to 50% at 1673 K for short periods. The releases of Ag and In were also small in oxygen under the analyzed conditions. The comparison with the experimental data suggests that conventional empirical release models may underestimate the Cd release at lower temperatures just after control rod failure in severe accidents.