Establishment Of The Method To Determine Nitrous Acid In Reprocessing Solution With Spectrofluorimetry

Nitric acid is the main matrix in the spent fuel reprocessing, in which there is the existence of nitrous acid decomposed by light and irradiation at all time. The concentration of nitrous acid influences the valence of elements such as neptunium, plutonium and some fission products. Thereby, it would influence the recovery of plutonium , the tend towards of neptunium and the decontamination of fission products. Thus, the determination of nitrous acid is one of the absolutely necessary analysis items in control analysis for reprocessing. Building a sensitive, simple and feasible analytical procedure for determination of nitrous acid is very important.After a large number of investigation on the literatures abroad and inland, we have found that there are many reports about the analysis of nitrous acid in wider environment and food products, but few in the spent fuel reprocessing. In the analytical procedures, most of them are about spectrophotometry and spectrofluorimetry, and the majority measuring methods in reprocessing is based on spectrophotometry. The dominance of which is on that it has high selectivity, but it has low sensitivity relatively, which would be a disadvantage to the analysis in reprocessing because the samples couldn' t be diluted when employed in actual determination. Now, we haven' t founded any reports about spectrofluorimetry employed in reprocessing analysis for detecting the content of nitrous acid.Spectrofluorimetry has good selectivity and high sensitivity. Employing in actual detection in reprocessing the samples could be diluted, thus would reduce the sample' s activity and toxicity, it is helpful to safe protecting.But most methods of Spectrofluorimetry have tedious procedures and have disadvantages to the analysis of nitrous acid in reprocessing. We found that operation processes is comparatively simple with the use of 5-aminofluorescence as the indicator through the comparing data from the whole bag of tricks, which also have high sensitivity and good stability, and could be used in reprocessing. Therefore, the research adopts 5-aminofluorescence as the indicator in the nitrous acid analysis.5-aminofluorescence has weak fluorescence. It will be diazotized by nitrous acid and produce a diazotizating compound in acidic condition, which the solution fluorescence will enhance sharply for the sake of nitrozation. We can calculate the concentration of nitrous acid by detecting the fluorescence intensity. Content:(1) By choosing the operation condition of the chemical apparatus, the consumption of ligand, the acidity of reaction system and reaction time etc, improved fluorescence signal and reduced the background.(2)Experimented with 30 kinds of cation and found most of them has no interference effect.(3) Detected a serious of standard samples' fluorescence intensity and drew a working curve under the selective condition, established a trace analysis method, demonstrated the technique' s linearity error and determination limits.(4) Detected the nitrous acid concentration in the simulation sample and tested the recovery rate.(5)To ensure the quality of the analysis technique, the paper evaluated the uncertainty of the testing result about wavelength, standard samples and actual samples, provided with the collection of all the parameters and the calculation methods needed for the calculation process, and evaluated thevalues of standard uncertainty, combined standard uncertainty, and expanded uncertainty.(6) Applied in the nitrous acid concentration detection in the simulation sample under the selective condition and checked the relative standard deviation of the technique and the samples' recovery rate.The method established by this work increased sensitivities by 2-4 magnitude compared to the common technique. Meanwhile, the determination accuracy is increased according to the optimization of operational parameters. The technique developed by this paper enabled the determination limits of solution to be as low as 42pg/mL (120pg/ml) and tallied with 50pg/ml reported by literature when the...