Modelling the radiation damage of fast reactor fuel cans due to helium

Using the U-120 cyclotron radiation damage was simulated of fast reactor fuel cans by fast neutrons producing helium by transmutation. The distribution of helium in the can material is considered to be homogeneous. The initial material of austenitic stainless steel was in the shape of rods, 20 to 25 mm in diameter. A method was developed of homogeneous helium implantation in steel simulating transmutation leading to helium formation in the can material as one of the factors of radiation damage of the materials in fast reactors. Mechanical properties of samples were measured using a tensile strength testing machine; the decrease in the overall ductility of samples with homogeneously implanted helium is the measure of high-temperature embrittlement of can materials in an actual fast reactor. Helium implanted in austenitic steel is distributed in the crystal lattice in either substitution or interstitial positions. The least ductility decrease was attained in steel S-14, this both after dissolving annealing and with 35% deformation. In the implantation region 8x10-7 to 5x10-5 of helium atoms to a steel atom, the percentage decrease in the overall ductility follows the function of the logarithm of the homogeneously implanted helium concentration. (O.K.)