  We examine an intrinsic graphene connected to the phonon thermostat at
temperature T under irradiation of thermal photons with temperature T_r, other
than T. The distribution of nonequilibrium electron-hole pairs was obtained for
the cases of low and high concentration of carriers. For the case when the
interparticle scattering is unessential, the distribution function is
determined by the interplay of intraband relaxation of energy due to acoustic
phonons and interband radiative transitions caused by the thermal radiation.
When the Coulomb scattering dominates, then the quasi-equilibrium distribution
with effective temperature and non-equilibrium concentration, determined
through balance equations, is realized. Due to the effect of thermal radiation
with temperature $T_r\neq T$ concentration and conductivity of carriers in
graphene modify essentially. It is demonstrated, that at $T_r>T$ the negative
interband absorption, caused by the inversion of carriers distribution, can
occur, i.e. graphene can be unstable under thermal irradiation.
