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Mass Spectrometric Techniques

In marine science, the measurements of long-lived radionuclides are used to fingerprint sources and their dispersion. The isotopic fingerprint of these sources is unique and can be used for tracing and identifying the pollutants. Mass spectrometric (MS) measurements can sometimes be the only technique able to relieve the isotopic fingerprint, especially for the minor isotopes of an element. MS techniques have very low detection limits permitting us to use smaller water-sample size which would not be possible if the long-lived radionuclides are measured by radiometric methods. The smaller water-sample size also permits an easier and faster handling on ship based sampling campaigns. The Radiometrics Laboratory mainly uses three different MS techniques for its Research Programme:

  • Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
  • Secondary Ion Mass Spectrometry (SIMS)
  • Accelerator Mass Spectrometry (AMS)

Table. Typical 240Pu/239Pu atom ratios from different Pu sources

Source240Pu/239Pu
Global fallout
(Northern Hemisphere)
0.18
Sellafield
re-processing plant
0.050.25
Cap la Hague
re-processing plant
0.34
Chernobyl accident0.56
Weapons grade Pu0.02-0.067