Development of Pu analysis in high active liquid waste (JASPAS JC-13)

not registered ; not registered ; Jitsukata, Shu*; Kurosawa, A.; Ikeda, Hisashi

It has been required from IAEA to determine a small amount of plutonium in the high active liquid waste solutions (HALW) in the tokai reprocessing plant. High performance spectrophotometer (HPSP), which could be obtained lower detection limit than conventional spectrophotometer, is studied to be applied the inspection and verification analysis. The results of applicability test are described in this report, [Cold Test] Neodymium, showing an absorption peak near the absorption wavelength of plutonium (VI), was used as an alternative element to plutonium, in order to review the calculation method of the peak intensity. [Hot Test] Plutonium nitrate solution was used for the fundamental test of this method. Since the method is known to be influenced by acidity, suspended sludge and coexistent elements in a sample, each dependency was examined. It was found that measurement results varied about 14% at a nitric acid concentration of 2-4 mol/L. Sludge could be removed by filtration before the measurement. The effect of coexisting elements could be eliminated adjusting the optical balance between reference and sample beam intensity. In the case of measuring a low concentration plutonium solution, a ratio of the peak intensity to the background intensity (S/B ratio) was not enough to the measured low concentration of Plutonium. Therefore a method should be improved the S/B ratio by analyzing the obtained spectra. Data accumulation method, simple moving average method and Fourier transform analysis was tested. The results showed that a combination of the accumulated average method and the moving average method was the optimum method fbr the purpose. Linearity of the calibration curve was found between 0-11 mgPu/L. Synthetic sample solution, which simulated the actual constituents of the HALW with plutonium, showed a good linear relation at 0-11 mgPu/L. The detection limit for plutonium concentration was 0.07 mgPu/L. When the synthetic HALW solution containing plutonium was m