Experimental evaluation of239Pu,238Pu and233U spikes for determining plutonium concentration by thermal ionization mass spectrometry and alpha-spectrometry

Experimental evaluation on the use of²³⁹Pu spike in Isotope Dilution-Thermal Ionization Mass Spectrometry (ID-TIMS),²³⁸Pu spike in Isotope Dilution Alpha Spectrometry (IDAS) and²³³U as a Non-Isotopic Diluent in Alpha Spectrometry (N-IDAS), for determing plutonium concentration in samples with burn-up values in the range of 1,000–10,000 MWD/TU is done. Precision is determined by analyzing replicate aliquots from different samples using each of the three spikes. Accuracy is established by comparing the results with those obtained by using well recognized spike²⁴²Pu in ID-TIMS. It is shown that the use of²³⁹Pu spike with the latest generation thermal ionization mass spectrometers gives the best precision (0.2%), whereas the precision values of 0.5 and 1% can be obtained by using²³⁸Pu and²³³U spikes, respectively, on a routine basis. Reasons for the difference in the precision values are discussed, along with the merits and drawbacks on the use of different spike isotopes.