Study On Radiochemical Separation And Analysis For ～(93)Zr

Zirconium isotope ⁹³Zr, reported half life of which is 1.53×10⁶y, is a long-livedpureβ-particle-emitting radionuclide, with energy of 60.6 keV(97.5%) and 91.4keV(2.5%). It is produced by nuclear fission and neutron activation of the stableisotope of ⁹²Zr. As it has high fission yield among all the fissionable materials, moreattention should be paid when high level radioactive wastes are dealed with. But up tonow, there are few reports about ⁹³Zr separation method and there is deficient innuclear data of ⁹³Zr. In order to supply samples for measuring its nuclear data, aradiochemical procedure needs to be developed to separate ⁹³Zr from the fissionproducts mixture.A silica gel adsorption method is choosen to separate Zr, because this method isuseful, simple and especially, it has high selectivity for adsorption of Zr.Experiments show that Cs, Sr, Mn, Co have no significant adsorption. With increasingof the acid concentration, the adsorption of Pu and U are decreasing. Also, the elutesolution is common and easily to be got.First, it was tested the adsorption and deadsorption behavior of stable Zr on silicagel with spectrophotometry assay. The column(4 mm diameter, 10 cm length) wasmade of glass. And the column was conditioned with 1 mol/1 HNO₃. Then asample ,which is 1 mol/L HNO₃ solution and contains stable Zr, was loaded to thecolumn with 1 mol/L HNO₃. The adsorbed Zr was desorbed with 10 tool/1 HNO₃.Results showed that the adsorption and desorption are quantitative in the range ofallowable error. Secondly, ⁹⁵Zr was separated from uranium fission products with thesame method and the radiochemical yeild is greater than 97%. The decontaminationfactors are 2.13×10³, 1.18×10⁴, 1.54×10⁴, 4.3×10² for ¹³⁷Cs, ⁸⁵Sr, Pu,¹⁵²Eu ,respectively. But they still did not satisfy our demand. So a TBP extraction andthe second silica gel column separation steps were adopted for further purification.Finally, using the developed procedure ⁹³Zr from a irradiated test fuel element ofQinshan Nuclear Power Plant was separated. The feed solution about 1 ml was loadedto the column and the column was washed with 23 column volume of 1 mol/L HNO₃. Then ⁹³Zr was desorbed with 10 mol/L HNO₃. The desorbed solution from the TBPextraction step was last loaded on the second silica gel column and repeated the stepsof the column separation. The ⁹³Zr obtained from whole procedure was measured byHGPeγspectrometer and liquid scintillation analyzer. The results show thedecontamination of theγ-emitting nuclides are almost complete. A comparison of our⁹³Zr liquid scintillation spectrum with that of ⁶³Ni indicates that the ⁹³Zr sampleseparated is pure.The whole recovery of the process is over 60%.Considering the ⁹³Zr standard solution is not available and the maximalβenergyof ⁶³Ni is close to the energy of ⁹³Zr, we use the ⁶³Ni standard to replace the ⁹³Zr toscale the efficiency when we measured the radioactivity of ⁹³Zr with liquidscintillation spectrometry. In this work, the effect of the acidity and the volum ofsamples were measured. Then the efficiency should be calculated from thequench-efficiency curve.To measured the number of ⁹³Zr atom with MC-ICP-MS, the optimizationparameters were achieved, such as collision gas flow rate and ion lens system. At hast,the concentration of ⁹³Zr was calculated by the curves of ⁹³Zr concentrations tosingnal intensities and ⁹¹Zr concentrations to singal intensities. The methord wasproved to be feasible.