Short term creep rupture predictions for tantalum alloy T-111

Abstract

A knowledge of the short term creep rupture behavior of Tantalum alloy T-111 is necessary to predict device integrity in the heat source section of Radioisotope Thermoelectric Generators (RTG's) at the end of service life, in the event of a fuel fire. High pressures exist in RTG's near the end of service life, these are caused by gas generation resulting from radioactive decay of the nuclear fuel. The internal pressure exerts a significant hoop stress on the T-111 alloy structural containment member. This paper analyses the short term creep behavior (rupture times up to -2 x 103 hrs.) of cold worked (CW) T-111 alloy, using the existing data of Stepherison (1967). Corellafions for the time to rupture, time to 1% strain and minimum creep rate have been obtained from this data using multivariable linear regression analysis. These results are compared to other short term rupture data for T-111 alloy. Finally, at the stress/temperature levels relevant to the RTG fuel f'tre scenario near the end of service life, the rupture time correlation for T-111 alloy predicts a rupture time of approximately 100 hrs.