Neutron activation determination of rhodium with preliminary micro-fire-assay concentration into a bismuth collector

The authors investigated the possibility of neutron activation determination of rhodium with micro-fire-assay preconcentration (MFAP) in conventional laboratory muffle furnaces or tube furnaces. Lead and bismuth were investigated as collectors. Lead or bismuth alloys obtained by MFAP of the test samples and reference samples (RS) with subsequent cupellation were irradiated along with monitors in the thermal channel of the VVR-K reactor at the Institute of Nuclear Physics (Academy of Sciences of the Kazakh SSR), equipped with a pneumatic transport system, in a flux of approximately 1 x 1013 neutrons per square centimeter per second. The monitors were comparison samples of manganese with a concentration of 2 x 10-5 g. The sample irradiation time was 1 min, measurement time 5 min. The measurements were performed 1.5 min and 1 h after irradiation in a gamma-ray spectrometer with a germanium-lithium detector with a volume of 40 cm3. The resolution of the spectrometer was 4.5 keV for the 1332-keV gamma line (60Co). The spectra of the monitors were taken under fixed conditions for 3 min, starting 10 min after irradiation. The rhodium content was determined from the area of the photopeak of the gamma line with an energy of 556 keV (104Rh + /sup 104m/Rh). With a rhodium content of 10-1% by weight (concentrates and slimes from copper-nickel ores), when using the cadmium channel (thickness 0.7 mm) with certain samples, rhodium can also be determined by purely instrumental NAA without preconcentration