As long as VVER-440 reactors exist, their fuel design is subject to ongoing improvement. Efforts to find the optimal fuel design continue and encompass increasingly extending ranges of both geometry and material parameters of fuel assemblies. This paper presents the results of optimized radial enrichment profiling for RK3+ fuel assemblies and discusses whether it is absolutely necessary to use burnable absorbers (Gd2O3 rods) in fuel assemblies suggested for prospective fuel cycles. Regarding RK3+ and RK2 fuel assemblies, this paper also presents thermohydraulic data yielded by computations performed using SC-1 certified software for a VVER-440 seven-assembly core fragment. These computations show that - compared to RK2 assemblies of the same capacity - RK3+ assemblies with optimized enrichment profile have more uniform radial temperature distributions and lower maximum outlet temperatures.

In 2016 OECD put forward a routine problem to simulate the operation conditions in VVER-1000 reactor of Rostov NPP unit No. 2 taking into account control rod motions. The participants were encouraged to simulate the integrated process and obtain the indications of the hot leg temperature control sensors depending on control rod motions. The data from in the experiment at 75% nominal power was selected for the first test carried out in the frames of the international task. Insertion of the 10th and 9th CPS rod groups into the core without driving was carried out in the low power testing experiments at Rostov NPP unit No. 2 (May 31, 2010). The task was split into several subtasks, each with its own specifics. One of such subtasks is focused on the simulation of the standard temperature control indications at the FA outlet. The way of solving the abovementioned subtask is reflected in the present report.

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