Using a volumetric technique, the deuterium solubility, X, in heavy water (L), low-pressure hexagonal ice (10, and high-pressure cubic clathrate ice (sII) is studied at deuterium pressures up to 1.8 kbar and temperatures from -40 to +5 degrees C. The triple point of the L + I-h + sII equilibrium is located at P = 1.07(3) kbar and T = -4.5(8)degrees C. The molar ratios D-2/D2O of phases at the triple point are X-L = 0.020(5), X-Ih = 0.012(5), and) X-sII = 0.207(5).