[en] One of the most important impurities in the reactor materials is boron. A boron atom captures thermal neutron fission and emits an alpha particle and a lithium ion in reciprocal directions. Either particle escaping the sample surface can create a damage zone in the plastic. When the plastic is etched in a strong basic solution these damage zones etch to form pits or tracks. The density of tracks, ρ, on the detector is directly related to the boron concentration in the sample and the thermal neutron dose according to the equation:ρ_tot=0.0495 N_bσφt(R_aη_a+R_liη_li). Measuring φ, thermal neutron flux in HWZPR, and irradiation time, t, may be obtained the boron concentration, N_B, in the sample by using this equation