Measuring effective radium concentration with large numbers of samples. Part I - experimental method and uncertainties

► We measured the effective radium concentration ECRa for a large number of samples. ► We used accumulation technique with scintillation flasks and SSNTDs. ► More than 1570 various rock and soil samples have been studied for their ECRa. ► The detection limit is adequate and varies between 0.04 and 0.09 Bq kg−1. ► The scintillation flask method appeared particularly useful and robust.