Applications of neutron activation analysis in determination of natural and man-made radionuclides, including PA-231

Determination of ultra-trace levels of uranium and thorium in electrolytic copper using radiochemical neutron activation analysis

Uranium and thorium as natural radioactive elements are present everywhere in the environment. Their trace levels are also present in various materials, such as copper, used as a shielding material in gamma-ray spectrometry, usually located very close to the detector. Ultra-low levels of uranium and thorium in electrolytic copper were determined in this study using radiochemical neutron activation analysis (RNAA) via their induced nuclides U-239/Np-239 and Pa-233, respectively. After irradiation of copper together with uranium and thorium standards, various techniques were used for their separation from the matrix. To isolate of short-lived U-239, solvent extraction in a combination of tributyl phosphate (TBP) in toluene was used. To separate Np-239 and Pa-233, extraction chromatography using TEVA and TK-400 resins was applied. Special attention was paid to the estimation of radiochemical recovery, which was determined in each sample aliquot using U-235, Np-238 and Pa-231 tracers. For quantification of induced nuclides and tracers used in the experiment, gamma-ray spectrometry was used. Obtained results showed that electrolytic copper samples contained impurities of uranium and thorium in ultra-trace levels: up to 45 pg/g (550 nBq/g) for uranium and up to 80 pg/g (330 nBq/g) for thorium. The electrolytic copper also contained impurities of Ag, As, Au, Sb, Se and Zn as observed using the k₀-INAA technique.

Analysis of radionuclides at ultra-low levels: A comparison of low and high-energy mass spectrometry with gamma-spectrometry for radiopurity measurements

Recent developments in high-energy accelerator mass spectrometry (AMS) and low-energy inductively coupled plasma mass spectrometry (ICPMS) made them the most sensitive techniques for ultra low-level analysis of ²³⁸U and ²³²Th. Detection limits below 1 nBq g^-1 for analysis of these radionuclides in construction materials were obtained. The most important development in the radiometric sector was operation of HPGe detectors in underground laboratories where detection limits of about 1 µBq kg^-1 were obtained. Specific features of radiometric, mass spectrometry and neutron activation techniques for ultra low-level radionuclide measurements are discussed, and obtained results for analysis of radiopure materials prepared for underground experiments are compared.

Radioanalytical techniques for the determination of 238U, 226Ra and 210Pb in the environment

Different radiometric techniques for the determination of 238U, 226Ra and 210Pb are presented and compared in terms of detection limits with mass spectrometric techniques. It can be concluded that when samples with low activity concentrations have to be measured, the method of choice in the case of 238U should be either RNAA/INAA or alpha particle spectrometry. In the case of 226Ra and 210Pb the best performance can be expected by the alpha spectrometry, whereas drawback of waiting for establishing secular radioactive equilibrium of 210Pb with 210Po makes techniques like beta counting and LSC more attractive for the determination of 210Pb. In addition, a case study on monitoring the former uranium mine Žirovski vrh is presented along with the used methodology and the summarised measurement results.

Determination of Np-237 by radiochemical neutron activation analysis combined with extraction chromatography

A procedure for determination of 237Np, 238Pu, 239,240Pu and 241Pu in environmental samples is described. Neptunium-237 is determined using radiochemical neutron activation analysis with pre- and post-irradiation chemistry based on solvent extraction and extraction chromatography. 238Pu, 239,240Pu is determined using alpha spectrometry and 241Pu by liquid scintillation spectrometry. The vertical profiles of 237Np, 238Pu, 239,240Pu in bottom sediments from the Black Sea are presented.