Nowadays computer models of fuel fabrication/refabrication, SNF reprocessing and waste management processes are under development as part of technologies front-end and back-end of closed fuel cycle. One of them is software package “VIZART” [1,2]. Code “VIZART” is used for material flow calculations of technological schemes and dynamic calculations of equipment work, taking into account capacity, transfer time between apparatuses and volumes of storage vessels. Results of such calculations are needed for development of initial data for equipment and facilities design.
Developed mathematical models are used to calculate regular transition and emergency modes, mass-dimension characteristics of equipment items, working hours and resources. The codes of individual processes in SNF reprocessing are included in “VIZART” as stand-alone modules and can be used both for calculation of technological modes and clarifying of coefficient and parameters of operation balance and dynamic calculations.
For example, model of linear crystallizer  was used to choose its optimal working mode for the crystallization refining of uranyl nitrate hexahydrate (UNH) melts in 2017. Temperature of crystallization, composition of initial solution of UNH melt, composition of washing solution, flow rates can be varied in this mathematical model. The yield of main component into crystals and its flow distribution also can be calculated. Optimal composition of initial solution, the temperature of crystallization process in purpose getting maximum yield of UNH crystals in experiments were chosen on the base of pre-test calculations. The estimation of filling time for crystal receiving vessel can be calculated by this mathematical model, as well. Knowing the filling time helped to create a working timeline for crystallizer. Further analysis of obtained experimental data and values calculated with mathematical model showed discrepancy of values on an average no more than 5 %.
Obtained results allow to clarify the parameters of dynamic calculations in «VIZART» of U-Pu-Np mixture crystallization refining. Working time and volumes of solutions in storage vessels were determined, as well.
Nowadays there are more than 30 individual models of main operations in hydrometallurgical and pyrochemical SNF reprocessing.
 Tretyakova S., Shmidt O., Makeyeva I. Spent nuclear fuel reprocessing modeling. - In: Proc. of 17th Radiochemical Conf. Czech Republic, Marianske Lazne, 11-16 May 2014, p. 376
 O.V. Shmidt, I.R. Makeeva, S.N. Liventsov Modeling closed nuclear fuel cycle processes. – Procedia Chemistry, V. 21 (2016), pp. 503 – 508.
 S. Veselov, V. Volk, V. Kasheev, et al., "Mathematic Simulation of Crystallization Refining Process of Spent Nuclear Fuel Reprocessing Desired Products in Linear Crystallizer", Advanced Materials Research, Vol. 1084 (2015), pp. 666-672