Irradiation Experiment to Determine Effect of Long Term Low Dose Irradiation on FBTR Grid Plate Material

• An accelerated irradiation test was performed in FBTR to characterize the mechanical property changes of the type 316 SS grid plate material subjected to low dose irradiation. • SS 316 irradiated to neutron doses of 1.1 - 2.6 dpa showed an increase in YS and UTS from the unirradiated values • The increase in YS was more pronounced than increase in UTS and this resulted in a reduction of uniform elongation or strain to necking. • These results are consistent with the results of irradiated SS316 reported in the literature • The 2.6 dpa specimen exhibiting a uniform elongation of above 20% at test temperatures of 28°C, 350°C and 400°C indicated retention of adequate residual ductility in SS 316 irradiated to this displacement damage. • Based on an extrapolation of the experimental data, the limiting value of 10% on uniform elongation is estimated to be reached after 6.5 EFPY, at a dose of 4.4 dpa. • Further irradiation experiments are planned to validate this extrapolation