[en] Japan Atomic Energy Agency, JAEA, is conducting the renewal program of the STACY (Static Experiment Critical Facility), from a homogeneous solution system to a heterogeneous water moderated system, in order to verify the criticality calculation considering the fuel debris which have been produced in the accident of the Fukushima Daiichi Nuclear Power Station. The first criticality of the new STACY is scheduled at the beginning of 2021. The new basic experimental cores of the first experimental campaign of STACY are designed. Two types of grid plates which grid interval is 1.27 cm and 1.50 cm, respectively will be fabricated for the experiments. Critical conditions with these grid plates with 5 wt% enrichment of ²³⁵U fuel rods are evaluated. The maximum number of fuel rods and concentration of boron doped in the moderator were calculated to keep the restrictions of STACY. The maximum and minimum values of the coefficients of reactivity and the kinetic parameters were obtained. It is confirmed that it is possible to operate the basic experimental cores with keeping the restrictions established by the license document. In this paper, possible configuration of the basic experimental cores and their limitations are discussed and presented. Series of critical experiments with the basic experimental cores will be performed with the results of this study