  The existing hydrous titanium oxide (HTiO) technique for the measurement of
224Ra and 226Ra in the water at the Sudbury Neutrino Observatory (SNO) has been
changed to make it faster and less sensitive to trace impurities in the HTiO
eluate. Using HTiO-loaded filters followed by cation exchange adsorption and
HTiO co-precipitation, Ra isotopes from 200-450 tonnes of heavy water can be
extracted and concentrated into a single sample of a few millilitres with a
total chemical efficiency of 50%. Combined with beta-alpha coincidence
counting, this method is capable of measuring 2.0x10^3 uBq/kg of 224Ra and
3.7x10^3 uBq/kg of 226Ra from the 232Th and 238U decay chains, respectively,
for a 275 tonne D2O assay, which are equivalent to 5x10^16 g Th/g and 3x10^16 g
U/g in heavy water.
