The accident at the Chornobyl nuclear power plant was one of the most serious nuclear incidents in human history. A radioactive plume covered a whole strip of northeastern Europe. The consequences of this catastrophe are still being felt, both in Ukraine and around the world. The article is devoted to the assessment of the consequences of radiocesium contamination of agricultural lands and irrigated waters during a possible accident at the Zaporizhzhia NPP and the associated Cs 137 contamination of sunflower products in the Zaporizhzhia region. The studies were carried out using a dynamic mathematical model for the formation of radionuclide activity in the "water-soilplant-product" system, ECOSIS-87 (Ecoplant). The article presents the results of studies of possible contamination of the environment by radiocesium according the Chornobyl NPP-86 scenario and sunflower production by the method of mathematical dynamic modeling. The calculations were carried out on the basis of the results of an agrochemical and agroecological survey of the state of soils in Ukraine and the Dnipro cascade of reservoirs. If an explosion occurs at the Zaporizhzhia NPP, the power of which will be equal to the Chornobyl NPP, then 100,000 hectares of agricultural land in the region will be taken out of the agricultural production of the Zaporizhzhia region. On agricultural lands where soil contamination with radiocaesium will be more than 5 Ci/km 2 , and the concentration in irrigated waters will reach 2 Bq/dm 3 , sunflower, which was grown for seeds to produce oil will need to be replaced with an industrial crop, which will also lead to loss of seed yield sunflower. Crop losses will lead to a decrease in the volume of sunflower oil. It should also be taken into account that the purification of soil and water does not occur in one year. At least in 5 years the situation will begin to improve.