Japan Atomic Energy Agency (JAEA) has been conducting the environmental sample analysis, which is one of the IAEA’s safeguards measures. In the analysis, isotope ratios of ultra-trace amounts of uranium and plutonium in samples taken from nuclear facilities are determined to detect undeclared nuclear materials and activities. In order to keep and enhance the reliability of the measurement results, validation of analytical methods and estimation of measurement uncertainty in such ultra-trace analysis should be properly done in accordance with worldwide standards. In this paper, the current activities on achievement of QA/QC (quality assurance and quality control) and estimation of measurement uncertainty in the ultra-trace analysis at a clean chemistry laboratory (CLEAR) of JAEA are reported.

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The extraction behaviour of Ag(I) from an aqueous nitrate medium employing (N-thio acetyl) benzamide(HA) in n-butanol has been investigated in presence of several organophosphorus donors like, tri-butyl phosphine oxide, tri-phenyl phosphine oxide and tributyl phosphate at pH 4.0 adopting radio tracer technique. The synergism was found in presence of neutral donors due to the formation of the adduct [Ag (A) (H₂O) (B)] in n-butanol (B denotes neutral donor). The overall equilibrium constant for each of the three ternary complexes and also for binary system were calculated from extraction data. It was found that the extent of extraction of Ag (I) in organic phase both as the binary complex as well as ternary complex increased with increase in temperature. The temperature dependence of the equilibrium constants were investigated in order to evaluate the thermodynamic parameters like enthalpy (ΔH°), entropy (ΔS°) and free energy (ΔG°). Extraction mechanism was finally supported by I.R spectra of ternary adduct.

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