The dose relevant natural occurring radionuclides in drinking and mineral water result dominantly from the U-238 decay series as being 238U, 234U, 226Ra as well as 210Pb and 210Po. Additionally, 228Ra from the Th-232 decay series and the radioactive noble gas Rn (especially 222Rn) and Tritium might play an important role. Procedures for all these isotopes are described in this handbook. All key nuclides can be determined quickly in a combined procedure.
Especially the Radium RAD Disk filter method for Radium and Lead isotopes described ahead (188.8.131.52.) (fig. 21) forms the central step in our rapid analytical procedure, suggested for the determination of key nuclides and group parameters in drinking water. The method can be combined with the direct 222Rn extraction (184.108.40.206.) and gross α/β-measurement after evaporation (220.127.116.11.). The direct measurement of the water sample as gel allows additionally the estimation of short and long-lived radionuclides (fig. 22). However, the lower limit of detection for β-emitters, required by the European drinking water ordinance, can only be obtained with a low level LS counter. Tritium with a limit of 100 Bq/L may easily be quantified by distillation (18.104.22.168.). More details of the whole scheme can be found in [Moebius et al. 2005]. The reliability and simplicity of the method can be enhanced by applying TDCR. Thus, quench correction is facilitated or totally avoided.
Figure 22: Advanced scheme for the determination of group parameters and key nuclides in water
Table 5: Summary of the determination of group parameters and key nuclides (MDA data for LL LS counter with PSD, e.g. Hidex 300SL)