The research field for fusion energy is developing rapidly and in addition to the well known mega project (e.g. ITER, DEMO), compact fusion tokamaks are under investigation. One interesting compact reactor is ARC (Affordable, Robust, Compact), a fusion device under development by Commonwealth Fusion Systems, designed for efficient energy production and material testing, which also involves research activities in Italian universities and industry. The presented work is developed in this framework and focuses on a neutronic analysis of an ARC-class fusion reactor. Monte Carlo simulations are carried out by means of OpenMC tool, to estimate Tritium Breeding Ratio (TBR), power generation, and neutron spectrum.