Rapid and non-destructive quantification of trace to minor concentrations of Uranium in ores, minerals and reference materials by instrumental neutron activation analysis using high-flux pneumatic carrier facility of Dhruva reactor

Abstract

ABSTRACT Rapid and non-destructive determination of trace quantities of Uranium in “as received” solid samples using a suitable analytical method is a challenging task. Uranium can be quantified by Instrumental Neutron Activation Analysis (INAA) using both short lived (239U) and medium-lived (239Np from decay of 239U) activation products. In the present work, INAA method has been optimised in terms of sample mass, duration of irradiation, lesser decay period and faster counting to acquire reasonable counts (peak area) under the peak of interest. Pneumatic Carrier Facility (PCF), high neutron flux (5 × 1013 n/cm2 /s at 50 MW power) at Dhruva research reactor, has been advantageously utilised for short duration irradiation (1 min) of the samples. Quantification of Uranium utilising 239U short-lived activation product (23.5 min half-life) formed after short irradiation, makes the methodology faster without any longer decay time. Immediately after 1 min of irradiation, the short-lived 239U activation product showed higher analytical sensitivity compared to that of medium-lived activation product (239Np) having gamma-rays at 106 and 277 keV. The detection limit of uranium was found to be much lower when it was calculated using 239U activation product. A comparative study was carried out between the short and medium lived activation products of 238U. The method was applied for determination of trace quantities of total Uranium in ores and minerals like Zircon, Ilmenite and Rutile having complex matrices. INAA method was validated by analysing USGS CRMs like STM-1, RGM-1 and AGV-1 and IAEA RM RGU-1. The detection limit was found to be around 1 ppb for the analysed solid samples (ores and minerals).