Effects of Radiation on Two Low-Alloy Steels at Elevated Temperatures

Abstract

The effects of temperature during irradiation on the tensile and impact properties of two low-alloy steels were studied. Tension and impact specimens of 1.25Cr-0.5Mo and 2.25Cr-1Mo steels were irradiated in a range of 2.8 x 1018 to 2.0 x 1020 nvt (greater than 1 Mev) and over a temperature range from room temperature to 1700 F. Results from postirradiation examinations conducted at room temperature indicate that the radiation effects on tensile properties are reduced at irradition temperatures above 725 F and at irradiation temperatures between 900 and 1100 F there is no apparent irradiation damage. For specimens irradiated above approximately 1100 F the tensile and yield strength increased again and strength levels equal to the unirradiated values were not observed until the steel was heated above the A3 point (1630 F). The second increase in tensile and yield strength may be associated with microstructural changes. Results from subsize impact specimens showed that irradiated data equivalent to the unirradiated impact values were not recovered until temperatures in the stress relief range were reached. At the higher temperatures the shift in impact properties appears to be more sensitive to temperature than to radiation dose.

Selection of the Structural Material for the Faret Liquid-Metal Systems

“…(44) Radiation Environment Currently there is speculation that neutron irradiation may permanently damage the ductility of the austenitic stainless steels at FARET temperatures. The experimental evidence is meager, (47,48,49,50) but the implications to high-temperature reactors justify an all-out effort to verify and, if true, to understand the problem so that we can either solve it or learn how to live with it. Unfortunately, meaningful studies take a long time and are costly and difficult.…”