Some nuclear power plants operating in the United States store spent nuclear fuel on-site in dry cask storage systems. Most dry storage systems use canisters fabricated from austenitic stainless steel. This scoping study evaluated the stress corrosion cracking susceptibility of as-received, sensitized, and welded type 304 stainless steel exposed to ammonium nitrate, sulfate, and bisulfate salts representing the soluble chemical composition in non-coastal airborne particulates.

Stress corrosion cracking tests were conducted at 45 °C-44% relative humidity (RH) and 35 °C-72% RH using type 304 stainless steel U-bend specimens coated with single salts and salt mixtures of ammonium sulfate, and ammonium nitrate with varying mole ratios representing the geographic, temporal, and diurnal variation of non-coastal salt composition. Examination of specimens from surface and cross section after exposure for less than two months showed that: (i) stress corrosion cracking had not occurred on any specimens, (ii) general corrosion occurred on the as-received and sensitized specimens deposited with NH4HSO4, (iii) a few shallow pits were evident on specimens deposited with a (NH4)2SO4 and NH4NO3 mixture, and (iii) the welded specimens exposed to NH4HSO4 had extensive general corrosion and grain boundary attack.

Subject
Salts, Sulfates, Deliquescence, Impedance, Mixtures, Ammonium, Particulates, Nitrates, U bends, Efflorescence, Stainless steel, Stress corrosion cracking, Conductivity
Keywords:
Type 304 stainless steel, stress corrosion cracking, U-bend, non-coastal salt
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2013
Association for Materials Protection and Performance (AMPP)
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