Determination of 210Pb and 226Ra/228Ra in continental water using HIDEX 300SL LS-spectrometer with TDCR efficiency tracing and optimized α⧸β-discrimination

• Optimized α⧸β separation for 226Ra/228Ra LS measurement.
• Evaluation of 210Pb/210Bi, 226Ra/222Rn and 228Ra/228Ra parent progeny in-growth relationships.
• Investigation of β-spectra interferences.

An analytical method for determination of 210Pb, 226Ra and 228Ra is presented based on adsorption on 3M Empore RadDiscs, and measurement applying liquid scintillation spectrometry (LSC) after elution. The LSC measurement was performed with optimized α⧸β-discrimination and isotope standardization using the triple to double coincidence ratio (TDCR). The consistency of measurement results between radioactive parent–daughter pairs 210Pb/210Bi, 226Ra/222Rn and 228Ra/228Ac was checked in long-term counting experiments and the influence ofinterference of in-growing daughters from 226Ra into the β-spectrum of 228Ra+228Ac was studied as well. Recommendations for optimized LSC 228Ra measurement besides presence of 226Ra are given.