RADIOCHEMICAL NEUTRON-ACTIVATION ANALYSIS FOR TRACE CHLORINE IN STEELS AND ALLOYS

Chlorine is usually present at low concentrations in reactor materials and thermal neutron activation of Cl-35 produces Cl-36, which has a l ong half-life and is a radionuclide of significance in nuclear waste d isposal. This paper describes a radiochemical method that has been dev eloped to measure low concentrations of CI in reactor stainless steels , so that the amount of Cl-36 in radioactive wastes can be estimated, The method is based on the irradiation of a 1 g sample in a thermal ne utron nux of 10(16), m(-2) s(-1), followed by dissolution in HNO3 with the addition of stable KCI carrier/tracer. The Cl is precipitated as AgCl, and the recovery is measured gravimetrically. The Cl-38, which h as a half-life of 37 min, is measured with gamma-ray spectrometry, The entire process, from irradiation to the end of counting, takes simila r to 1.5 h. The recovery is near-quantitative, and the detection limit for Cl in most stainless steels is below 1 mg/kg.