The electron spin resonance method was used in na investigation of heavily doped n-type silicon [phosphorus concentration N_P = (2-10)×10¹⁸ cm^-3] irradiated with reactor neutrons in doses 5×10¹⁷-4×10¹⁹ cm^-2. In addition to the spectra of the familiar G7 (divacancy) and P3 (tetravacancy) centers, the investigated samples exhibited two new spectra denoted by H9 and H10. The parameters of the spin Hamiltonian of these spectra were determined. According to the results obtained, the H9 spectrum was due to nonorientable divacancies located in zones of strong lattice deformation zones was ε ≥ 10^-3. It was postulated that H10 is a vacancy-type defect with a paramagnetic electron localized on a broken bond of a silicon atom. Some of the characteristics of the P3 and P6 spectra observed for heavily doped n-type silicon indicated that the manifestation of these centers depends on the Fermi level position.