Authors:S. Ravi, S. Ravi, A. K. Deepa, A. K. Deepa, S. Susheela, S. Susheela, P. V. Achuthan, P. V. Achuthan, S. Anil Kumar, and U. Jambunathan
A method has been developed for the estimation of 90Sr in reprocessed uranium oxide samples obtained from the Purex processing of natural uranium spent fuel discharged from the
research reactor. The method employs a combination of precipitation and solvent extraction procedure to eliminate other beta-impurities
prior to resorting to the estimation of 90Sr by beta-counting. 106Ru was eliminated by volatalizing with perchloric acid, uranium was removed by carrier precipitation with strontium as sulphate.
The sulphate precipitate was converted to carbonate and dissolved in nitric acid. 234Th and 234Pa were eliminated by synergistic solvent extraction using tri-n-butyl phosphate and thenoyl trifluoroacetone extractant mixture
in xylene. An iron scavenging step was included to remove any residual impurities. Finally, strontium is precipitated as SrC2O4. H2O. The separated 90Sr activity was followed to check the equilibrium growth of 90Y.
Authors:S. Ravi, A. Deepa, B. Surekha, S. Susheela, P. Achuthan, S. Anil Kumar, K. Vijayan, U. Jambunathan, S. Munshi, and P. Dey
90Sr estimation in reprocessed uranium was carried out by a series of solvent extraction and carrier precipitation techniques
using strontium and lanthanum carriers. Fuming with HClO4 was used to remove 106Ru as RuO4. Three step solvent extraction with 50% tri-n-butyl phosphate in xylene in presence of small amounts of dibutyl phosphate
and thenoyl trifluoro acetone was carried out to eliminate uranium, plutonium, thorium and protactinium impurities. Lanthanum
oxalate precipitation in acid medium was employed to scavenge the remaining multivalent ions. Strontium was precipitated as
strontium oxalate in alkaline pH and 137 Cs was removed by washing the precipitate with water. A strontium recovery well above 70% was obtained. Final estimation
was carried out by radiometry using end window GM counter after drying the precipitate under an infra red lamp. The same procedure
was extended to the estimation of 90Sr in a diluted sample of the actual spent fuel solution. An additional lanthanum oxalate precipitation step was required
to remove the entire 144Ce impurity from this sample. This modified procedure was employed in the determination of 90Sr in a number of reprocessed uranium samples and the over all precision of the method was found to be well within ±10%. An
additional barium chromate precipitation step was necessary for the analysis of reprocessed uranium samples from high bumup
fuels to eliminate trace amounts of short lived 224Ra produced during the decay of 232U and its daughters as they interfere in the estimation of 90Sr.