а). Dependence of burnup depth on the height of the reactor core at the end of nuclear fuel irradiation campaign: 1 – without taking re-shuffling of graphite blocks into account; 2 – taking re-shuffling of graphite blocks into account. b). Dependence of the value of expired lifespan of graphite along the core height at the end of reactor fuel irradiation campaign with different non-uniformity of heat release after re-shuffling the blocks at the middle of fuel irradiation campaign