Alloy 33, an austenitic33Cr-32Fe-31Ni-1.6Mo-0.6Cu-0.4N material shows excellent resistance to corrosion when exposed to highly oxidizing media as e.g. HNO3 and HNO3/HF mixtures which are encountered in reprocessing of nuclear fuel. According to the test results available so far, resistance to corrosion in boiling azeotropic (67%)HNO3 is about 6 and 2 times superiorto AISI 304 L and 310 L. In higher concentrated nitric acid it can be considered corrosion resistant up to 95%. HNO3 at 25° C (77° F), up to 90% HNO3 at 50° C (122° F) and up to somewhat less than 85% HNO3 at 75°C (167° F). In 20% HNO3 / 7% HF at 50° C ( 122° F) its resistance to corrosion is superior to AISI 316 Ti and , AlIoy 28 by factors of about 200 and 2.4. Other media tested with different results include 12% HNO3 with up to 3.5 % HF and 0.4 %HF with 32 to 67.5 % HN03 at 90° C (194° F). Alloy 33 is easily fabricated into all product forms required for chemical plants (e.g. plate, sheet, strip, wire, tube and flanges). Components such as dished ends and tube to tube sheet weldments have been successfully fabricated facilitating the use of Alloy 33 for reprocessing of nuclear fuel.
Keywords: Alloy 33, nitric acid, hydrofluoric acid, mixed nitric/ hydrofluoric acid, reprocessing of nuclear fuel