Analysis of ะก1 experiment on UPTF facility with an advanced ATHLET model

I. Pasichnyk, K. Velkov, S.P. Nikonov, GRS, Germany

21st Symposium of AER on VVER Reactor Physics and Reactor Safety (2011, Dresden, Germany)
Nuclear applications of three dimensional thermal hydraulics


ATHLET simulation results are compared with the available experimental data of C1
experiment on UPTF facility. Leading phenomena by C1 test are the fluid-fluid mixing and
condensation in the cold legs and in the downcomer of the UPTF. The initiating event is the
actuation of the emergency core cooling (ECC) system. Water is injected into the water-filled
or into steam-filled cold legs. The flow mixing and condensation phenomena determine the
global cooldown and the fluid temperature distribution in the downcomer and in that way can
be defined the boundary conditions for performing Pressurized Thermal Shock (PTS)
Developed is a detailed ATHLET model of the UPTF based on a special pre-processor which
generates automatically pseudo-3D nodalization scheme of the facility and also the
corresponding ATHLET input data set including a description of the thermo-hydraulic
objects and the connections between them. In order to account for the specific structure of the
facility newly developed advanced capabilities of ATHLET system code are applied.
Moreover in the special version of ATHLET 2.2B several new enhancements are introduced
which give a substantial acceleration of the 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 presented study is a part of the
validation of the new ATHLET developments and the new nodalization methodology.

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