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

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).

KEYWORDS:

• Uranium
• NAA
• short-lived activation product
• PCF
• self-serve facility
• ores and minerals

Acknowledgments

Authors would like to thank Head, ROD and PCF operation crews at Dhruva and for their support towards sample irradiations. Authors are thankful to Dr. P. K. Mohapatra, Head, Radiochemistry Division, and Associate Director, RC and I Group, for his encouragement and support. Authors thank Dr A. Sengupta, RCD for his guidance and help for this work and Mrs. Priya V Mestry RCD for her help. Authors also thank Dr. S. V. Thakare, RPhD and Mr Naresh Gamare, RPhD, BARC for their help in sample irradiation. This work is a part of PhD thesis of Mr. S. K. Samanta in Chemical sciences under Homi Bhabha National Institute (HBNI), DAE.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Credit authorship contribution statement

S. K. Samanta: Conceptualization, design of methodology, experiments, final data collection and analysis, supervision, manuscript preparation. Sonika Gupta: Helping in sample preparation, irradiation and measurements. R. Acharya: Conceptualization, investigation, supervision, manuscript preparation.