In particular, increasing the mass of uranium in one fuel rod would enable to lower uranium enrichment level without reduction of thermal power generation in the reactor. In turn, a lower uranium enrichment will reduce the cost of the nuclear fuel production chain, as well as facilitate handling irradiated fuel.
https://www.neweurope.eu/article/russias-rosatom-develops-lower-uranium-enrichment-for-finlands-loviisa-npp/