The concentration of unbound neutral anion vacancies in cerium gadolinium ceramics Ce(0.8)Gd(0.2)O(1.9) with a submicrocrystalline structure has been determined using low-temperature helium defectoscopy at temperatures ranging from 613 to 773 K and at saturation pressures from 0.05 to 12 MPa. It has been found that the energy of dissociation of impurity-vacancy complexes is 1.1 +/- 0.2 eV, and the energy of dissolution of helium in defects is -0.8 +/- 0.2 eV. The obtained results have been compared both with the experimental data on the energy of interaction between helium and ions of the cerium gadolinium ceramics and with the results of the quantum-chemical calculations. It has been demonstrated that the anomalously low value of the energy of helium dissolution in the studied ceramic samples is determined by the chemical interaction of helium with the nearest environment of the cerium cations.