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DE88 °02897The radiation chemistry of nitrogen/oxygen/water systems is reviewed. General radiolytic effects in dry nitrogen/oxygen systems are relatively well characterized. Irradiation results 1n the formation of steady state concentrations of ozone, nitrous oxide and nitrogen dioxide. In closod systems, the concentration observed depends on the total dose, temperature and initial gas composition. Only three studies have been published that focus on the radiation chemistry of nitrogen/oxygen/water homogeneous gas systems. Mixed phase work that is relevant to the gaseous system is also summarized. The presence of water vapor results in the formation of nitric acid and significantly changes the chemistry observed in dry air systems. Mechanistic evidence from the studies reviewed are summarized and discussed in relation to characterizing the gas phase during the containment period of a repository in tuff.

Three iron-to nickel-based austeniric alloys (Types 304L and 316L stainless steels and Alloy 825) are being considered as candidate materials for the fabrication of highlevel radioactive-waste containers. Waste will include fuel assemblies from reactors as well as high-level waste in borosilicate glass forms, and will be sent to the prospective repository at Yucca Mountain, Nevada. The decay of radionuclides in the repository will result in the generation of sub stantial heat and in fluences of gamma radiation. Container materials may undergo any of several modes of degradation in this environment, including atmospheric oxidation; uniform aqueous phase corrosion; pitting; crevice corrosion; sensitization and intergranular stress corrosion cracking (IGSCC); *nd transgranular stress corrosion cracking (TGSCC). This report is an analysis of data i elevant to the pitting, crevice corrosion, and stress corrosion cracking (SCO of the three austeniric candidate alloys. The candi dates are compared in terms of their susceptibilities to these forms of corrosion. Although all three candidates have demonstrated pitting and crevice corrosion in chloride-containing environments, Alloy 825 has the greatest resistance to these types of localized corrosion (LC); such resistance is important because pits can penetrate the metal and serve as crack initiation sites. Both Types 304L and 316L stainless steels are susceptible to SCC in acidic chloride media. In contrast, SCC has not been documented in Alloy 825 under comparable conditions. Gamma radiation has been found to en hance SCC in Types 304 and 304L stainless steels, but it has no detectable effect on the resistance of Alloy 825 to SCC. Furthermore, while the effects of microbiologically in duced corrosion have been observed for 300-series stainless steels, nickel-based alloys such as Alloy 825 seem to be immune to such problems. This analysis indicates that the candidates should be ranked according to their resis tance to LC and SCC as follows: Alloy 825 (best) > Type 316L > Type 304L (worst).

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Volume2 M g n D a t a Abstract 1. Introduction 2. Current List of Candidate Materials 3. Degraded Materials Properties 4. Final Remarks 5 References 6. Tables and Figures Volume 3 CorroSionDataandModeling Abstract 1. Degradation Mode Surveys 2. Resdts of Corrosion Testing 3. Radiation Effects on Corrosion 4. Modeling 5. References