The OECD/NEA PSB-VVER project provided unique and useful experimental data from the large-scale PSB-VVER test facility for code validation. This facility represents the scaled down layout of the Russian designed PWR reactors, namely VVER-1000. The fifth experiment is a LB LOCA in cold leg. The objectives of the test are the investigation of the thermal-hydraulic response of the VVER-1000 following a LB LOCA accident as well as the investigation of the phenomena involved in the transient by the availability of experimental data which are useful for the validation of thermal-hydraulic system codes. The paper discusses the achievements of the assessment of CATHARE2 code from the qualitative and the quantitative evaluations of the results. The results are compared with the analysis carried out by RELAP5-3D code. The quantification of the accuracy is based on the Fast Fourier Transform Base Method, developed at University of Pisa, which provides an integral representation of the accuracy quantification in the frequency domain.