Neutron shielding performance of Cd/316L composite fabricated by arc plasma sintering

Ensuring subcriticality over storage duration, even in accident condition, is one of the important requirements for dry cask designed to store spent fuel from nuclear reactor. To comply this requirement, neutron absorbers are incorporated in the spent fuel basket to decrease the neutron multiplication factor and reactivity. The objectives of this study are to prepare Cd/316L composite for neutron absorber material by powder metallurgy and determine the neutron shielding performance of the obtained composite. Powder mixtures of SS316L with various Cd contents were milled using high energy milling, followed by pressing and sintering at 450 °C and 700 °C. The analyses of the samples were carried out using XRD, SEM-EDS, XRF, and neutron transmittance test. Additionally, the neutron transmittance was also calculated using MCNP5. The results show that transformation of austenite to α-ferrite occurred during powder milling process which remained in the sample after sintering at 450 °C. Transformation of α-ferrite in the milled sample to austenite occurred after sintering at 700 °C. Cd in the samples were predominantly oxidized to form CdO phase during sintering process at both temperature conditions. The loss of Cd content in the Cd/SS316L samples after milling process was approximately 10 %. The Cd content further decreased by approximately 10 and 50 % after sintering at 450 and 700 °C, respectively. Neutron transmittance test shows that the transmittance value for thermal neutron decreased with the increased of Cd in the Cd/316 sample. A good agreement has been obtained between the results from experiment and MCNP calculation.