Long-lived radionuclides isotope ratio measurements

Multi-element IDMS is available when using ICP-MS. For transient signals, however, the multi-element capability is reduced as two isotopes have to be measured for each element. In principle all elements of the periodic system having two natural isotopes can be analysed by IDMS as long as mass spectrometric methods for isotope ratio determinations are available. Moreover even mono-isotopic elements can be determined, if they also have a long-lived radionuclide isotope such as iodine-129. 

Instrumental layouts and developments in AMS are reviewed by Kutschera.195 Today AMS is the most powerful, sensitive and selective mass spectrometric technique for measuring long-lived radionuclides at the level of natural isotopic abundances (10-16 to 10-12). Accelerator mass spectrometry (AMS) allows uranium isotope ratio measurements with an abundance sensitivity for 236U in the range of l(rlo-10 l2.l98J"... 

Isotope Ratio Measurement of Long-Lived Radionuclides... 

Accelerator mass spectrometry (AMS) - precise measurement of the isotopic ratios of the long-lived radionuclides that occur naturally in our environment are beyond the ability of conventional mass spectrometers. For isotopes that exist as infinitesimal traces (a single atom in the presence of 1x10 stable atoms) there exist worldwide, a network of around 50 mass spectrometers, each derived from Van de Graaff accelerators, which are used for these analyses (Figure 16.28). 

AMS measures the ratio of a long-lived radionuclide to its stable isotope (e.g., C/ C). However, in the case of plutonium, there is no stable isotope. Hence, it is necessary to add a spike of a known amount of one of the long-lived isotopes, generally Pu (3.75 x 10 years) or Pu (2.4 x 10 years), to the sample in order to quantify the concentrations of the... 

---