On the basis of screening tests and favorable mechanical propenties, AISI Type 318 stainless steel was selected as a fuel-element cladding material to operate in c coolant comprised essentially of gaseous nitrogen modified by the addition of oxygen and water vapor. Tests at atmospheric pressure confirmed calculations which indicated that small additions of oxygen to nitrogen would inhibit nitriding by the process of preferential oxidation. The tests at atmospheric pressure determined that the rate of oxidation of Type 318 stainless was generally at a minimum when 0.5 volume per cent oxygen was added to the nitrogen gas. Oxidation of this steel was more severe when additions of 0.1 and 5.0 volume per cent oxygen were made to the nitrogen The rate of oxidation was primarily temperature dependent, but was also influenced by time. Oxidation during exposure periods of less than 1000 hr appeared to proceed at a parabolic rate. On longer exposures, however, there wcre indications of more rapid attack. A maximum depth of attack of 2.9 mils was observed on Type 318 stainless which had been exposed at 1650 F for 3658 hr. Stress-corrosion studies indicated that unstressed and stressed specimens were attacked at about the same rate. Stresses …

Comments made hy FMPC personnel on Eurochemic technical documents are given, (T.R.H.)