Examination of stainless steel ducts and pin wire wraps of fuel assemblies from BN-350

Remote optical metallography, scanning electron microscopy, X-ray microanalysis and microhardness measurements were used to determine the depth of corrosion during water storage and the extent of sensitization in-reactor in the irradiated steel ducts and wire wraps of representative fuel assemblies from the fast reactor B N-350. The objective of all this work was to characterize the condition of BN-350 assemblies after 5-20 years water immersion in the reactor spent fuel storage pool before drying and packaging them for prolonged storage. The depth of corrosion after 5-15 years in the oxygenated water of the spent fuel storage pool at the reactor was measured as < 50μm austenitic steels, and for ferritic steel.Corrosion was found to be greatest for the 12X18H10T steel and least for the 03X16H15M3 steel. Immersion density measurements were performed on samples of the four steel after fast neutron exposures of 10-70 dpa. The three austenitic steel exhibited decreases in their relative density in the range of 5.6-9.4%, while minimum swelling of <1.5% was observed for the ferritic steel 1X13M2MVB