Analysis of simulated and high level waste samples by ICP-AES

In a reprocessing plant for spent nuclear fuel, the spent fuel is dissolved in concentrated nitric acid to facilitate removal of plutonium and un-burnt uranium by suitable chemical separation process. The raffinate solution contains more than 99 % of the non-volatile fission product elements, impurities from the cladding materials, corrosion products, traces of un-separated plutonium and most of the trans-uranic elements. This reprocessing waste is called high-level radioactive liquid waste (HLLW). Such solutions are known to contain high concentration of certain elements viz: Fe (0.72 - 1) g/L, Na (3-5) g/L, Cr (0.12- 0.2) g/l, K (0.2-0.4) g/L, Mn (0.4-0.5) g/L, Sr (0.03-0.1) g/L, Ba (0.06-0.1) g/ L, U (3-5) g/L, Ni (0.1-0.2) g/L, Zr (0.004-0.02) g/L and lanthanides (present as rare earth mixture viz: Ce, La, Nd, Pr, Sm, Y etc.- (0.1-0.3) g/L. In addition few elements such as Pd, Mo, In, Sb, Se and Te have also been included as specification elements of interest in other waste solutions generated from DAE units such as IGCAR, PREFRE and BARC (WMD) etc. As a part of the work of the task force for characterization of SHLW/HLLW, methods were required to be developed by ICP-AES for determining about 25 elements such as Ag, Al, Ba, Ca, Cd, Ce, Cr, Dy, Eu, Fe, Gd, Hf, In, La, Mn, Mg, Mo, Na, Nd, Ni, Pd, Sb, Se, Sr, Sm, Y and Zr etc in such waste solutions. As these waste solutions contain appreciable amounts of Cr, Fe, Mn and Na (few % levels) contribution on the various analytical channels were monitored by aspirating 50-500 μg/mL of these interfering elements in to ICP. It was observed that up to 200 μg/mL concentration level of the interferent, there is no significant contribution to the analytical channels of elements of interest. Few synthetic samples containing these elements were prepared and analyzed by ICP-AES after the removal of uranium by 30 % TBP in CCl4 in 4M HNO3 medium. For all the elements, parameters were suitably optimised to select a suitable analytical line taking in to account the relative sensitivity and interference factors. Based on the method developed samples from PREFRE, CIRUS, and FBR were analyzed. The results of two synthetic samples analyzed by the method developed for 14 typical elements