In the present work, neutron irradiation effects on swelling were investigated for hexagonal boron nitride (hBN) and hexagonal boron nitride-titanium diboride (hBN-TiB2) composites. hBN and hBN-TiB2 composites were irradiated by reactor neutrons which include thermal, epithermal and fast neutrons at the central thimble of the reactor. The fast neutron (E-n > 0.1 MeV) and thermal neutron (E-n similar to 0.025 eV) fluxes were 1.44 x 10(16) m(-2) s(-1) and 6.48 x 10(16) m(-2) s(-1), respectively. The samples were induced by reactor neutrons up to total dose of 5.7 x 10(20) m(-2). The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were carried out before and after irradiation of the samples. The lattice parameters and unit cell volumes were determined. The swelling percentages were calculated for hBN and hBN-TiB2 samples. For reactor neutrons irradiation, maximum swelling percentages were 4.29% for hBN and about 4.22% for hBN-TiB2 at the maximum exposed neutron dose. Furthermore, phase transition was observed from TiB2 to TiN phase in hBN-TiB2 composites with neutron irradiation. An experimental study was performed on hBN and hBN-TiB2 for nuclear applications (neutron detectors, control rods etc.).