PERFORMANCE-CHARACTERISTICS OF A GLOVE BOX INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETER FOR THE ANALYSIS OF NUCLEAR-MATERIALS

A commercial inductively coupled plasma mass spectrometer (Elan 250) was modified in order to analyse nuclear materials in a glove box. The nebulizer, plasma torch and sliding interface are situated inside the glove box while the mass spectrometer and associated electronics are outside. The sensitivity of the modified instrument is slightly reduced compared with the original owing to a flange that separates the mass spectrometer from the vacuum interface. This has modified the original distance between the skimmer cone and the ion lens system. The plasma torch is mounted in a fixed position and the load coil is now separated 25 mm from the tip of the sampling cone. Optimum plasma operating conditions, stability of the signal and isotopic ratios, levels of oxide and hydroxide polyatomic ions were evaluated in the modified instrument for selected fission products and actinides. The effect of the ion lens settings on sensitivity and mass discrimination were studied in detail. Interference effects due to heavy matrix elements (U and Pu) were also studied.