Rosatom expects to begin loading fuel assemblies in the BN-800 fast neutron reactor at the end of December 2013- early January 2014, according to a representative of Rosenergoatom. The reactor is expected to reach criticality in April 2014. The current plan is to start the reactor in August 2014 and bring it to the full power by the end of 2014.
The reactor will begin operations with HEU and MOX fuel in the core. Reportedly, 75% of the first core is HEU. Also,
96 69 assemblies in the first core will contain vibro-packed MOX and about 66 54 assemblies are pellet-based MOX. [CORRECTED on 11/10/2018 based on the paper "The BN-800 core with MOX fuel"] It was reported that 100 MOX assemblies for BN-800 have been manufactured by NIIAR in Dimitrovgrad - apparently these are the vibro-packed MOX assemblies (NIIAR has the required production capacity). The 66 pellet-based MOX assemblies are being manufactured by NIIAR as well. The pellets and fuel elements for these are produced at the Mayak Plant (it has some production capacity, although it lost the bid to build a large fabrication facility to Zheleznogorsk).
BN-800 is expected to switch to full MOX core in 2015-2016, when the fuel fabrication facility at the Mining and Chemical Combine in Zheleznogorsk begins operations (the plant will produce MOX pellets).
Russia is also working on nitride fuel for its fast reactors, but this project is still in its pilot stage (See Anatoli Diakov, "Status and Prospects for Russia's Fuel Cycle," Science & Global Security, 21, no. 3, (2013): 181-182).