Hydrogen absorption by Zr-2,5%Nb alloy has been investigated under irradiation with fluence up to 4,21022 n/cm2 (Е>0,1 MeV) at temperatures in the range between 40 °C and 80 °С. It was shown that at hydrogen concentration higher than ~20 ppm the S-ZrH166 phase with face-centered cubic lattice is formed. At hydrogen concentration higher than ~30 ppm hydrides (blisters) are accumulated on the water-cooled zirconium surface. When hydrogen concentration increases so do blister density and size. It was determined that hydrogen absorption by metal depends on sediment size and irradiation temperature. During CPS channel operation the hydrogen concentration in metal almost does not depend on fluence. The effect on hydrogen absorption of the phase composition of zirconium alloy is observed.