For dosimetry of beta -radionuclides in surface and potable water, an impre
gnated porous scintillator based on p-terphenyl is proposed, which is a mat
rix with through pores with a sorbent selectively absorbing radionuclides o
n the pore surface. Synthetic hydroxyapatite is used as sorbent for stronti
um-90. High measurement sensitivity is ensured by concentration of the emit
ter from large volume of water and realization of 4 pi -geometry of radiati
on detection.