A static mode mass spectrometer for the measurement of noble gases

A “static” mode mass spectrometer has been developed for measuring the fission product gases Xe and Kr in the determination of nuclear fuel burnup. Accurate and reproducible results from samples of less than 10¹⁰ atoms have been demonstrated. The all metal spectrometer system was designed to operate without dynamic pumping during an analysis so that the noble gas present is not depleted. System pressure from all sources during a run may vary from 10⁻¹⁰ torr to 10⁻⁶ torr. Quantitative gas samples were obtained from low level burnup of 93% enriched ²³⁵U, irradiated in a known neutron flux. This method appears feasible for samples as small as 10⁷ atoms or even less with the experimental modifications suggested in the text.