Abstract
The main goal of this work is to perform pin-by-pin calculations of Swiss LWR fuel assemblies with neutron transport deterministic methods. At Paul Scherrer Institut (PSI), LWR calculations are performed with the core management system CMSYS, which is based on the Studsvik suite of codes. CMSYS includes models for all the Swiss reactors validated against a database of experimental information. Moreover, PSI has improved the pin power calculations by developing models of Swiss fuel assemblies for the Monte Carlo code MCNP, with the isotopic compositions obtained from the In-Core Fuel Management data of the Studsvik suite of codes, by using the SNF code. A step forward is to use a neutron code based on fast deterministic neutron transport methods. The method used in this work is based on a planar Method of Characteristics in which the axial coupling is solved by 1D SP3 method. The neutron code used is nTRACER. Thus, the methodology of this work develops nTRACER models of Swiss PWR fuel assemblies, in which the fuel of each pin and axial level is modelled with the isotopic composition obtained from SNF. This methodology was applied to 2D and 3D calculations of a Swiss PWR fuel assembly. However, this method has two main limitations. First, the cross sections libraries of nTRACER lack some of the isotopes obtained by SNF. Fortunately, this work proves that the missing isotopes do not have a strong effect on keff and the power distribution. Second, the 3D models require high computational memory resources, that is, more than 260 Gb. Thus, the nTRACER code was modified, so now it uses only 8 Gb, without any loss of accuracy. Finally, the keff and power results are compared with Monte Carlo calculations obtained by Serpent.
Highlights
An important goal at Paul Scherrer Institut (PSI) is to conduct research aimed at developing stateof-the-art computational methodologies and incorporate them into a consistent Code System for integral multi-physics multi-scale LWR safety analyses
At Paul Scherrer Institut (PSI), LWR calculations are performed with the core management system CMSYS, which is based on the Studsvik suite of codes
PSI has improved the pin power calculations by developing models of Swiss fuel assemblies for the Monte Carlo code MCNP, with the isotopic compositions obtained from the In-Core Fuel Management data of the Studsvik suite of codes, by using the SNF code
Summary
An important goal at Paul Scherrer Institut (PSI) is to conduct research aimed at developing stateof-the-art computational methodologies and incorporate them into a consistent Code System for integral multi-physics multi-scale LWR safety analyses. The core management system of PSI, CMSYS [1], is based on the Studsvik suite of codes This system includes models for all the Swiss reactors up to the latest operated cycles, which are validated against a database of experimental information. The SNF code [4], which belongs to the Studsvik suite of codes, was recently added to calculate the isotopic compositions and radiation sources of different Swiss fuel assemblies [5]. This code makes use of the In-Core Fuel Management (ICFM) data of CASMO/SIMULATE, providing detailed information of the state of the fuel and its operating history
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