Total reflection X-ray fluorescence for determination of radium in water simulated by MCNP6.2 code

The measurement of trace concentrations of radium in water by total reflection X-ray fluorescence (TXRF) is addressed. X-ray fluorescence spectra and the calibration plot data were numerically simulated by the MCNP6.2 code using a 2482 Bq/g 226Ra standard solution, with gallium added as an internal standard element. From the simulations, the lower limit of activity concentration measurable by this technique is 0.047 Bq/L. The results also show that the detection limit 2.56 x 10-11 g can be achieved in a molybdenum X-ray tube in TXRF geometry, provided the samples are previously evaporated to a dry residue. For drinking water, it requires a complete evaporation of 937 mL containing 1.0 Bq/L of 226Ra, which is the current upper limit of activity concentration recommended by the World Health Organization (WHO) guideline.

Automated summary

The TXRF technique can measure trace concentrations of radium in water with a detection limit of 0.047 Bq/L. With a molybdenum X-ray tube in TXRF geometry, a detection limit of 2.56 x 10-11 g can be achieved, but samples need to be evaporated to a dry residue beforehand. The WHO guideline recommends an upper limit of 1.0 Bq/L for radium in drinking water.