Direct quantitative analysis of cesium pencil in simulated hot-cell using remote-LIBS equipped with a miniature collimator

137Cs containing borosilicate glass encapsulated in SS tube, known as Cs-pencil is replacing the traditional 137CsCl powder used in blood irradiator for enhanced nuclear safety. Accurate quantification and checking the homogeneity of 137Cs distribution are an integral aspect of its quality assessment. We present the first quantitative measurement of Cs-pencils using a miniature collimator equipped remote-laser-induced breakdown spectroscopy (LIBS) system, which involves no sample preparation. A simulated hot-cell structure forcing the remote acquisition of signal at >1 m was constructed for this analysis. The relationship between the signal intensity with the solid angle of the collection, created by the collimator with the remote distance was evaluated, and this was supported both experimentally and theoretically. Studies were also carried out to characterize the spectral noise embedded in the LIBS spectrum. The results reveal the inadequacy of fitting algorithms in high noise spectra. With the use of 266 nm laser for ablation, and under ambient Ar conditions, the accuracy and precision for the determination of Cs were found to be 2.5-5% at 1-1.5 m remote distances. The results obtained demonstrated that the miniature collimator equipped remote-LIBS is suitable for analyzing Cs-pencil produced by fissionogenic 137Cs and has enormous potential to be employed as a routine analytical technique in the nuclear industry.