Evaluation of the economically reasonable nuclear fuel irradiation time period extension for the WWER type reactors

The problem of NPP flexibility increase at the expense of water-water reactor power unit operation in the regime of arbitrary decrease of their capacity after complete use of the reactivity gain for the fuel burn-up is considered. Prolongation of the reactor company tau at the expense of using power and temperature reactivity effects makes it possible to increase power generation with the same fuel loading in accordance with the requirements for the power system in the whole. The results of multivariant calculations of economically optimal tau(tausub(opt)) for the units with WWER-440 type reactors are presented. It is obvious analyzing the obtained data that tausub(opt) values can be changed within rather wide ranges dependent on economic parameters of the power unit operation in the operation regime before the beginning of the reactor company prolongation. The less is fuel component of the power cost in this case and the higher is the ratio of power price to the fuel component of its cost and the less is tausub(opt)