Ra-226 determination via the rate of Rn-222 ingrowth with the Radium Delayed Coincidence Counter (RaDeCC)

W. Geibert (1) , V. Rodellas (2) , A. Annett (1) , P. van Beek (3) , J. Garcia-Orellana (2, 4) , Y. T. Hsieh (5) , P. Masque (2, 6)

1 School of Geosciences [Edinburgh]
2 ICTA - Institut de Ciencia i Tecnologia Ambientals
3 GEOMAR LEGOS
4 Departament de Física
5 Department of Earth Sciences [Oxford]
6 Departament de Física

We present a new method to determine Ra-226 in aqueous environmental samples, based on the rate of ingrowth of Rn-222 from Ra-226, using the radium delayed coincidence counter (RaDeCC). We use the same instrument setup that is used for the determination of Ra-223 and Ra-224. In contrast to methods published earlier, the approach does not require a modification of the counting equipment, counting separately for Ra-226, or waiting for radioactive equilibrium. We show that the calibration works from as low as 10 dpm (0.166 Bq) per sample, up to more than 1000 dpm (16.7 Bq). Although uncertainties are larger (typically around 10%) than reported uncertainties for gamma counting, liquid scintillation, or mass spectrometry at comparable activities, the simple setup, low cost, and robustness of the method make it a useful approach for underway measurements, combinations with short-lived radium isotopes, or monitoring purposes when limited funding or infrastructure is available.

Mots clés: SUBMARINE GROUNDWATER DISCHARGE; COASTAL WATERS; ISOTOPES; SPECTROMETRY; SEAWATER; FIBER

Domaines: Océan, Atmosphère

W. Geibert, V. Rodellas, A. Annett, P. van Beek, J. Garcia-Orellana, et al.. Ra-226 determination via the rate of Rn-222 ingrowth with the Radium Delayed Coincidence Counter (RaDeCC). Limnology and Oceanography: Methods, 2013, 11, pp.594-603. ⟨10.4319/lom.2013.11.594⟩. ⟨hal-00985399⟩