[en] The core of IRR-1 reactor consists of two types of MTR fuel elements: standard fuel elements with 23 fuel plates and special fuel elements with 17 fuel plates (to allow for insertion of Cd-In-Ag control blades). Spent fuel elements are currently stored in small apart racks, , in the reactor pool. It is planed to relocate all spent fuel elements in a new spent fuel storage pool (SFSP). he elements will be surrounded by Cd boxes, which form a compact array that must be ept subcritical (k_eff < 0.9) under all possible conditions. The Monte Carlo code MCNP (1) and the transport/diffusion codes WIMS/EXTERMINATOR (EXT2) were both employed in the analyses of the reactor core and the SFSP. The core calculations, besides determining the k_eff, include the neutron flux and the power distributions. The purpose of this paper is to describe these analyses and discuss their results