Qualification of TRACE V5 Code Against Fast Cooldown Transient in the PKL-III Integral Test Facility
NURETH-14 - 2011 September 25-30


Presented at:
NURETH-14
2011 September 25-30
Location:
Toronto, Canada
Session Title:
B13-3 Development, Assessment and Applications of TRACE

Authors:
Eugenio Coscarelli (GRNSPG, Università di Pisa)
Alessandro Del Nevo (GRNSPG, Università di Pisa)
Francesco S. D'Auria (University of Pisa, GRNSPG, Italy)
  

Abstract

The present paper deals with the analytical study of the PKL experiment G3.1 performed using the TRACE code (version 5.0 patch 1). The G-series consists of eight tests carried out at the PKL-III facility located in Germany. In particular, the test G3.1 simulates a fast cooldown transient, namely, a main steam line break. The break in the steam line, causes a rapid depressurization of the affected steam generator. This leads to a strong asymmetry caused by an increase of the heat transfer from the primary to the secondary side that induces a fast cooldown transient on the primary side affected loop. The asymmetric overcooling effect requires an assessment of the reactor pressure vessel integrity considering PTS (pressurized thermal shock) and an assessment of potential recriticality following entrainment of colder water into the core area.The analytical investigation is performed by developing a complete TRACE input model of the PKL integral test facility, including 3-dimensional components to simulate the thermal-hydraulic behavior of the fluid in the reactor vessel (RPV). The aim of this work is the qualification of the heat transfer capabilities of the TRACE code from primary to secondary side in the intact and affected steam generators (SGs) during the rapid depressurization and the boil-off in the affected SG against experimental data. The accuracy of the calculation is evaluated by qualitative and quantitative analysis. The quantification of the accuracy is performed using the Fast Fourier Transform Base Method (FFTBM) developed at University of Pisa. The tool provides an integral representation of the accuracy quantification in the frequency domain.

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