Neutronic analysis of the ALLEGRO fast reactor core with deterministic ERANOS code and Monte Carlo Serpent code

Abstract

Abstract The Gas-cooled Fast Reactor is an advanced concept selected to be part of the fourth generation of nuclear reactors. Before its development, the construction of the experimental demonstration reactor ALLEGRO is planned. Given the current interest in this innovative system, a neutronic study of the ALLEGRO reactor core is performed using the Monte Carlo Serpent calculation code and the deterministic ERANOS code. A detailed description of the core design and ceramic fuel composition is provided. To reduce the computational cost of the simulations for future applications, different cases are analyzed using different computational options in the TGV/VARIANT module and a 7-group energy structure. To validate the ERANOS models, the results are compared with the three-dimensional heterogeneous reference model developed in Serpent. The main parameters of the core, at the beginning of life, are calculated, such as the k-eff value, flux and power distributions, Doppler constant, effect of helium density on reactivity and the β-eff value. The main discrepancies in the results correspond to the diffusion and simplified transport calculations, due to the low density of helium. By using the 7-group structure, it was possible to reduce the calculation time with a reduced penalty in the precision of the results. Furthermore, the best agreement was obtained, with respect to the Serpent model, for the transport calculation (P3) with the 7-energy group structure. The k-eff and fuel isotope mass evolution during burnup is analyzed assuming an operating time of 365\xa0days. The relative fuel fraction at the beginning and end of cycle, the breeding ratio and the average burnup are also given.