Influence of Swelling on Irradiated CW Titanium Modified 316 Embrittlement

For fast breeder reactor core materials, the main limitations are usually swelling and irradiation embrittlement. Tension tests and Charpy tests performed on CW Titanium modified 316 (CW 316 Ti) wrappers irradiated in Phenix at up to 100 dpa nrt provide strong evidence of a correlation between swelling and embrittlement.

Tensile tests were performed at room temperature, at 180°C, and at the irradiation temperature on tensile specimens machined from wrappers; the tests were done on different heats leading to different swelling values. Charpy tests were also performed at room temperature, 180°C, and the irradiation temperature on Charpy specimens machined from different wrappers.

As swelling increases, we first observe a large decrease in the total energy absorbed by specimen rupture in Charpy tests and the absence of necking before failure in tensile tests; when swelling reaches about 6%, the total absorbed energy in Charpy tests becomes very low and uniform elongation in tensile tests decreases. At higher swelling values, failure in tensile tests may occur without any plastic deformation, with the UTS itself decreasing sharply.