APOLLO II: a user-oriented, portable, modular code for multigroup transport assembly calculations

APOLLO II is a new, multigroup transport code under development at the Commissariat a l'Energie Atomique. The code has a modular structure and uses sophisticated software for data structuralization, dynamic memory management, data storage and user's macrolanguage. This paper gives an overview of the main methods used in the code for a) multidimensional collision-probability calculations, b) leakage calculations and c) homogenization procedures. Numerical examples are shown to demonstrate the potentialities of the modular structure of the code and the interest of the novel multilevel flat-flux representation used in the calculation of the collision probabilities