[en] CP - 2D is a two dimensional transport code based on the first flight collision probability method. The geometry description is formalized in factor geometry approach. This is a great advantage since the code is modularly built and a straightforward development from simple to complex geometry is possible. The flexibility of the geometry allows treating circular (CANDU) or rectangular fuel pin (TRIGA, PWR) clusters and also a relatively large local zone. A detailed pin structure and individual fuel elements description is permitted. Also the boundary of the assembly can be exactly treated. The first version CP - 2D1.0 was released in 1998. The second, CP - 2D2.0, was released in 1999 and uses a multi-stratified coolant model for CANDU loss of coolant accident analysis. The third version is in the testing stage and contains a generalized burning scheme. This version is intended for fuel assembly neutronic performance analysis. The paper is focused on the mathematical, numerical, programming and modelling aspects used to obtain an efficient tool for complicated geometry. Optimal algorithms, a new tracking scheme based on the mobile set of chords and macro-bands techniques, automatic evaluation of the integration errors, generalized burning algorithm, geometry factorization are some of the most efficient approaches for the reducing of the memory requirements and computing time and for the increasing of the stability and the accuracy. Some results (reactivities, flux distributions, distributions of fission power per element) are presented for a multi-stratified model of the partial and total loss of coolant accident in a typical CANDU cell. The results are compared with HELIOS results. (author)