Vacuum fusion-mass spectrometric determination of H, N and O in U3Si fuel using the standard addition technique

A vacuum fusion-mass spectrometric method is described for the determination of H, N and O in uranium suicide fuels. Samples are fused with an 85% Pt/15% Sn flux in a graphite crucible heated to 1300 °C to release nitrogen and oxygen as N2 and CO, respectively. Hydrogen evolves more readily and is determined without the flux, to minimize the H2 blank. The H+2, C+ and N+ signals are used to determine the partial pressures of the extracted H2, CO and N2, after calibration with known gas mixtures. The precision and accuracy of gas analysis is ca. 2% (1s). The N and O determinations in fuel samples are quantitated by the standard addition technique, which shows recoveries of 91 and 99% for N and O, respectively. The hydrogen results showed good agreement with those obtained by an independent hot vacuum extraction method. The overall uncertainty of fuel analyses is large because of fuel heterogeneity. Detection limits are: H, 1; N, 9; O, 30 μgg.