Interlaboratory analytical comparison of the cobalt and carbon contents of two nuclear grade boiler tubing superalloys

Accurate determinations of the cobalt and carbon contents in the boiler tubing alloys UNS N06600 and UNS N08800 are important to the proper specification of these materials for CANDU power reactors. Samples were prepared and an interlaboratory comparison of analytical methods for these elements has been conducted between eleven laboratories to determine the relative reliability of these methods as well as to detect any bias due to sampling of the tubing material itself. Both the colorimetric and atomic absorption methods yielded cobalt concentrations that were statistically identical; similar relative precisions (2σ = 5%) were obtained with either method. Carbon determinations of the UNS N06600 alloy done by combustion also produced excellent agreement (within 8%) among corresponding laboratories, but poorer agreement was obtained with the UNS N08800 alloys. No bias due to different sampling methods could be detected. (auth)