The effect of boron and titanium addition on the behavior of steel alloys of base composition AISI304 as a nuclear radiation shielding material

Borated stainless-steel alloys are candidate neutron absorber materials for criticality control in disposal containers or dry storage canisters.Type 304Mo borated stainless steels are similar to conventional Type 304Mo stainless steels except that they contain a boron addition, which imparts a much higher thermal neutron absorption cross section than other austenitic stainless steels.Three grades of steel alloys with base composition of AISI304Mo but having either Ti or B or Ti and B (SS304MoTi, SS304MoB and SS304MoTiB) were modified and produced using 30 kg pilot plant medium frequency induction furnace under similar conditions.The macroscopic-cross sections for neutrons of energy higher than 10 keV, slow, and total slow neutrons were measured using 241 Am-Be neutron source for the produced samples.The developed boron and boron-titanium stainless steel alloys were found to have higher cross sections for neutrons higher than 10 keV, slow, and total slow neutrons than SS304Mo.Moreover, the associated neutron half value layer (HVL) was calculated for each sample.Additionally, gamma ray shielding properties were measured for several gamma ray energies that emitted from 232 Th radioactive source.Among the investigated steels, the lowest corrosion rate was found in the modified steel containing boron.Samples of the properly treated steels were subjected to microstructure observation, hardness, tensile and impact testing.The microstructure observation revealed an austenitic phase in all investigated steel alloys and a very large number of twins in the optical micrographs of the investigated samples.The strengthening effect of B or Ti and B is to great extent the reason of the solution hardening and precipitation strengthening effects of these elements as these elements are strong carbide or nitride formers.The higher B content increases the formation speed of intermetallic compounds and lowers the ductility.