Qualitative and quantitative analysis of beta emitters in aqueous solutions
A beta spectrometer, consisting of a liquid scintillation counter, coupled to a programmable multichannel analyser was used to achieve the objective of detecting and measuring beta activity in low level aqueous environmental solution as well as identifying the radioisotopes present. Aqueous solutions of standard beta emitters, covering a range of energies between 18.6 KeV and 3550 KeV, were used to develop computer methods for analysis. The best proportions of the counting cocktail was found consist of 4.0 ml of aqueous sample, 3.0 ml of Triton X-100 and 3.0 ml of toluene containing 4.0 g per litre PRO and 0.4 g per litre POPOP. The effects of pH, acids, bases, buffers, and salts on the stability of the mixture and on the detection efficiency of the radioisotopes, were investigated and found not to be severe. Pretreatment of the sample was not required. It was found that temperature changes, beyond the operating temperature range, could result severe errors. 1024 channels of aquisition area, for the collection of the spectra, give good conditions for computer analysis. End channel and channel number of maximum count calibration gave a linear relationship to the Em, of standard beta emitters. It was found that the theoretical fitting of the spectra is possible and the normalisation ratio V of the theoretical to the experimental fitting procedure has alinear relationship to the activity of emitter. Kurie plot was applied for checking the Emav value of the emitters used. Application of the Cerenkov counting technique for beta emitters, gives extra data to support the main results. For the analysis of environmental solutions, which may contain a variety of radioisotopes, the system was used to obtain spectra of alpha emitters, beta emitters with internal conversion and Cerenkov radiation. Synthetic mixtures of tritium and carbon-14 of activity ratios between 8:1 and 1:8 were used to investigate the problems of multielement spectral analysis.