APOLLO3® is a common project of CEA, AREVA and EDF for the development of a new generation code system for core physics analysis providing improved accuracy, flexible software architecture and high computation performances and taking into account both RandD and industrial application requirements. This paper presents the most important developments implemented in the deterministic APOLLO3® code, and their validation. APOLLO3® provides new capabilities from spectral aspect up to core calculations and a large panel of solvers adapted for different applications.This paper discusses the general architecture of the software platform, the data libraries, models of cross section self-shielding and solvers implemented in APOLLO3®. The last part of this paper describes the verification and the validation of that platform and examples of use cases PWR (Pressurized Water Reactor) and SFR (Sodium Fast Reactor) applications.