Reactivity measurement methods and the first results of the physical start-up for the nuclear subcritical facility "Neutron source” - A. Bykhun; P. Gladkikh; I. Karnaukhov; V. Lyashchenko; A. Mytsykov; V. Ridozub; V. Selivanov; V. Stomin; A. Ter-tychnyj; I. Ushakov (Ukrainian journal of physics, 2023)