The determination of total rare earths in irradiated nuclear fuels by extraction-spectrophotometry

Investigation was made into the operating conditions for the preliminary separation of uranium and plutonium from the dissolution solution of irradiated fuels by TOPO-cyclohexane, and the extraction of total rare earths by PMBP-benzene. The content of total rare earths is determined spectrophotometrically with chlorophosphonazo-mA as the color developer. The optinium condition for reducing the absorptivity of yttrium with (NH4)2C2O4 was proposed. Under this condition the absorptivities of yttrium and the cerium group tend to be similar. The recovery of each rare earth element is about 97%. By means of this procedure the content of total rare earths in the irradiated uranium fuels is determined and the burn-up of the fuels is calculated. The result is consistent with that obtained by mass spectrometric and radiochemical methods with a deviation less than +- 2%. The procedure may be applied to the determination of the burn-up of irradiated uranium fuel