A.A. Trenkin - Ph.D. (Phys.-Math.), Leading Research Scientist, State Corporation on Atomic Energy «Rosatom», Federal State Unitary Entity «Russian Federal Nuclear Center - All-Russian Scientific and Research Institute of Experimental Physics» (RFNC-VNIIEF), (Sarov, Nizhny Novgorod region). E-mail: trenkin@ntc.vniief.ru