C-PORCA 7: a nodal diffusion reactor calculation code to support off-line and on-line core analysis at Paks nuclear power plant
28th Symposium of AER on VVER Reactor Physics and Reactor Safety (2018, Olomouc, Czechia)
Advances in spectral and core calculation methods
The C-PORCA/HELIOS models have been used at NPP Paks as basic core neutron physics calculation tools for many years. During the last decade some new kind of fuel assemblies were utilised in Paks. In order to fulfil the accuracy and performance requirements of the off-line core analysis and in-core monitoring continuous development and testing of the codes have been performed. As a latest development the C-PORCA is available to calculate not only VVER-440, but VVER-1000 core as well.
The C-PORCA is a node-wise diffusion model for the purpose of 3D core analysis. As it is common in node-wise approach the assemblies inside the core are divided into hexagonal or triangular prisms with several numbers of axial layers. These space elements called nodes have got homogenous neutron cross sections. The solver of the diffusion equation needs to determine the space dependent neutron flux inside the nodes and join the fluxes between adjacent nodes applying the flux discontinuity and neutron current continuity. For this purpose the hybrid finite element method is used in C-PORCA.
The HELIOS is a well-known neutron transport code. Its utilisation at Paks NPP has dual use. On one hand this code is a basic tool for preparation of homogenised few-group neutron cross sections inside fuel nodes and areas without fuel such as regions of reflectors and absorbers. On the other hand the flexibility of the code allows to use it for the purpose of testing.
In this paper the main characteristics of the diffusion solver applied in the C-PORCA model is described. The accuracy of this solver is also demonstrated, on the basis of comparisons with different international references available in hexagonal geometry. The C-PORCA results have been compared against benchmark data, produced in the frame of the AER (Atomic Energy Research) community during the last decades. All presented comparisons illustrate that the accuracy of the C-PORCA diffusion solver is excellent.