Advanced ATHLET Model for the UPTF Facility
NURETH-14 - 2011 September 25-30

Presented at:
2011 September 25-30
Toronto, Canada
Session Title:
B4-1 Plant System Safety Code Development and Assessment

Sergey Nikonov (RRC “Kurchatov Institute”)
Ihor Pasichnyk (GRS mbH)
Kiril Velkov (GRS mbH)


The aim of the presented study is to determine the limits of application of the one dimentional system code ATHLET by describing in a pseudo 3D manner the thermohydraulic modelling of a reactor pressure vessel. For this purpose ATHLET simulation results are compared with available experimental data of the UPTF facility.  Developed is a detailed ATHLET model based on a special preprocessor which is able to generate automatically a three dimensional nodalization of the facility. Based on this nodalization the preprocessor creates the necessary ATHLET input data set, including a description of the thermohydraulic objects and the connections between them. To take into account a spacial structure of interacting objects, advanced capabilities of ATHLET system code, namely cross connections in a system of parallel thermohydraulic channels are applied. Moreover in a new version of ATHLET several improvements are introduced: 1) an algorithm of the ATHLET Jacobian preconditioner is optimized; 2) a new direct sparse matrix solver based on the KLU algorithm of Tim Davis is implemented which gives a substantial acceleration of calculations for a large number of control volumes and makes feasible transient simulations with a detailed (ten thousands of control volumes) description of the investigated facility. The obtained comparisons have proved the advantages of the new modelling and applied computational algorithms and have confirmed the ability of the ATHLET code to describe in a pseudo 3D manner the thermohydraulic processes in a reactor pressure vessel.

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