Determination of sulfur in steels by radiochemical neutron activation analysis with liquid scintillation counting

A method has been developed for the determination of low-level sulfur in steels by radiochemical neutron activation analysis. During sample irradiation, ³⁵S is produced by the ³⁴S(n,γ)³⁵S reaction. Irradiated steels are mixed with sulfur carrier and dissolved in HCl/HNO₃. Sulfur is reduced to H₂S by reaction with HI/H₃PO₂/HCl. The evolved H₂S is absorbed in dilute NaOH, which is mixed with scintillation cocktail for the measurement of ³⁵S by liquid scintillation counting. Sulfur carrier yield is determined by iodometric titration. Chlorine is also determined by RNAA in order to correct for ³⁵S produced via the ³⁵Cl(n,p)³⁵S reaction. Sulfur has been determined at mass fractions as low as ≈5 mg/kg in ultra-high-purity iron using this method.