General Corrosion of Incoloy-800 in Simulated Superheat Reactor Environment
Year: 1964
Type: report
Abstract: The 300 series stainless steels had been selected originally as the reference fuel cladding material for utilization in several superheat reactor (SHR) systems being built as part of the United States Atomic Energy Commission (USAEC) program. The adequacy of the general corrosion resistance of Type-304 stainless steel for superheat fuel cladding was confirmed in the Phase I portion of the study reported previously. Fuel jacket failures that occurred in Type-304 stainless clad fuel elements exposed in the Vallecitos boiling water reactor superheated steam loop indicated the questionable dependability of such stainless steels for this SHX fuel cladding application. The following conclusions are based on the out-of-pile general corrosion evaluations completed to date on Incoloy-800 as a fuel cladding for nuclear superheat applications: 1. The corrosion data from 4000-hour heat transfer tests indicate good corrosion resistance up to at least a 1300°F metal temperature. By use of a devised method of data treatment, the general corrosion for three years exposure at 1300°F can be calculated to average 0.0016 inch with an upper 95 percent confidence limit of 0.0033 inch. 2. A compositionally-disturbed layer develops at the metal-oxide interface. The disturbed layer depth is a function of time and temperature of exposure. The most pessimistic interpretation of the growth rate with time would indicate a layer depth of 0.0017 inch after a three years' exposure at 1300°F. The possible effects of such a layer on cyclic type exposures (i.e., cyclic strain, corrosion fatigue, etc.) have not been evaluated. 3. The corrosion results indicate excellent corrosion resistance of Incoloy-800 when exposed isothermally to steam generated from a simulated BWR and superheated to 1150°F. Corrosion rates .of 3.6 +- 1.2 mg/dm(2) -mo at 1050°F and 10 +- 18 mg/dm(2)-mo at 1150°F are applicable in such exposures with a steam velocity of 20 ft/sec. 4. The potential activity problem from metal-to-system losses increases in significance with increase in metal temperature (especially above 1100°F) and increase in exposure time. At least one-half of the oxide formed on metal operating at temperatures between 1200 and 1300°F will be carried downstream from the cladding. 5. Additional exposures of Incoloy-800 sheaths as heat transfer specimens at metal temperatures of 1200-1400°F are required to permit more accurate extrapolation of the higher temperature corrosion rate and corrosion-product-release rate data and to establish the ratio of alloy constituents lost to the system over time periods of about three years.
DOI: 10.2172/4046872
Authors: W.L. Pearl, E.G. Brush, G.G. Gaul, G.P. Wozadlo
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3085069