Accelerator mass spectrometry of plutonium isotopes

FIFIELD, L.K.; CRESSWELL, R.G.; DI TADA, M.L.; OPHEL, T.R.; DAY, J.P.; CLACHER, A.P.; KING, S.J.; PRIEST, N.D.

BEAM INTERACTIONS WITH MATERIALS AND ATOMS.

Elsevier

Año: 1996 vol. 117 p. 295 - 303

0168-583X

The feasibility of measuring plutonium isotope ratios by accelerator mass spectrometry has been demonstrated. Measurements on a test sample of known composition and on a blank showed that isotope ratios could be determined quantitatively, and that the present limit of detection by AMS is ~ 106 atoms of plutonium. For 239Pu, this limit is at least two orders of magnitude lower than that practicable by alpha-spectrometry. In addition, 240Pu/239Pu ratios were measured for four samples for which the combined activity of the two isotopes had been determined previously by alpha-counting. All measurements of plutonium isotope ratios entailed injection of PuO~ into the 14UD accelerator operating at 3.5 MV, gas stripping, and analysis of the 7+ charge state after acceleration. Plutonium ions at 28 MeV were detected in a longitudinal-field ionisation chamber with an energy resolution of 3%. Using uranium oxide as a surrogate for plutonium oxide, it was shown that UO- was the predominant negative ion and that the probability for its formation and extraction was 0.3%.